RESUMO
This study evaluated the effects of dose of equine chorionic gonadotropin (eCG) and its splitting in different days of the synchronization protocol on reproductive performance of primiparous and multiparous Nellore cows. In the present study, 2,536 Nellore cows (1,634 primiparous and 902 multiparous) were assigned to receive in a 2 × 2 factorial design 1) an intravaginal progesterone (P4) device and 2.0 mg of estradiol benzoate (EB) on day -11, 12.5 mg (i.m.) of dinoprost tromethamine (PGF), 300 IU (i.m.) of eCG, 0.6 mg (i.m.) of estradiol cypionate (ECP), and P4 device withdrawal on day -2, followed by TAI on day 0 (n = 632 cows, being 409 primiparous and 223 multiparous; 300-2), 2) 300 IU (i.m) of eCG administered on days -4 and -2 (150 IU of eCG/day; n = 637 cows, being 412 primiparous and 225 multiparous; 300-4-2), 3) 400 IU (i.m.) of eCG administered on day -2 (n = 633 cows, being 406 primiparous and 227 multiparous; 400-2), and 4) 400 IU (i.m) of eCG administered on days -4 and -2 (200 IU of eCG/day; n = 634 cows, being 407 primiparous and 227 multiparous; 400-4-2). Individual cow BCS was assessed on days -11, 0 (timed-AI), and 31 of the study. Body condition score of the animals was classified into LOW or HIGH using the threshold of 2.75 (≤2.75 = LOW; >2.75 = HIGH). For primiparous cows, an eCG splitting effect was observed on follicle size, as cows receiving eCG on days -4 and -2 of the synchronization protocol had a larger follicle than cows administered eCG only on day -2. For day 31 P/AI, primiparous cows receiving 400-4-2, regardless of BCS, had a greater P/AI than cows from other treatments. Administering 400-4-2 to LOW BCS cows also resulted in greater P/AI than all other treatments assigned to LOW BCS cows. For multiparous cows, no treatment effect was observed for follicle size, estrus expression, and day 31 P/AI (P ≥ 0.21). In summary, increasing the dose and splitting the dose of eCG positively impacted the pregnancy rates of primiparous cows under a BCS ≤2.75, but no effects were detected on multiparous cows.
Assuntos
Progesterona , Reprodução , Gravidez , Feminino , Bovinos , Animais , Cavalos , Progesterona/farmacologia , Estradiol/farmacologia , Taxa de Gravidez , Dinoprosta/farmacologia , Inseminação Artificial/veterinária , Inseminação Artificial/métodos , Gonadotropina Coriônica/farmacologia , Sincronização do Estro/métodos , Hormônio Liberador de Gonadotropina/farmacologiaRESUMO
The objective of this observational study was to evaluate estrous expression at the first estrus occurring between 7 to 30 d in milk (DIM), as detected by an automated activity monitor (AAM), and its association with genomic daughter pregnancy rate (GDPR) and genomic expected milk production (GEM) in lactating dairy cows. A total of 4,119 lactations from 2,602 Holstein cows were included. Cows were enrolled as first lactation (n = 1,168), second lactation (n = 1,525) and third and greater lactation (n = 1,426). Hair samples were collected from the tail switch, and cows were genotyped using an SNP platform (Clarifide, Zoetis, São Paulo, SP, Brazil). Postpartum cows were examined daily by the farm personnel from calving until 10 DIM. Calving was classified as assisted (forced calf extraction) and unassisted (normal calving). Retained fetal membranes (RFM), hyperketonemia (KET), and left displaced abomasum (LDA) were also recorded. Mean GDPR (± SD) was -0.29 ± 1.4, and the intensity and duration of the first estrus event was 15.9 ± 13.1 x-factor (intensity unit measurement) and 11.1 ± 3.8 h, respectively. Cows that had greater GDPR had greater intensity and longer duration of estrus at the alert, independent of parity. Overall resumption of estrous expression, between 7 to 30 DIM, was 41.2% (1,695/4,119), where 58.8% (2,424/4,119) did not have an estrus event, 31.0% (1,274/4,119) of cows had one event of estrus, and 10.2% (421/4,119) of cows had 2 or more events of estrus early postpartum. Mean DIM (± SD) at first estrus event, detected by the AAM, was 19.4 ± 4.4 d. Days in milk at first event for cows with one event was 20.7 ± 1.6 d and 15.9 ± 3.1 d for cows with 2 or more events of estrus. First lactation cows were more likely to have an estrus event early postpartum when compared with second and third and greater lactation cows (45.2 ± 1.4% [530/1168] vs. 41.6 ± 1.3% [636/1525] vs. 37.2 ± 1.3% [529/1426], respectively). There was an interaction of parity and GDPR on the proportion of cows demonstrating an early postpartum estrus. There was no difference in the proportion of cows with an early postpartum estrus between those with assisted or unassisted calving, RFM, or LDA. However, cows that had KET were less likely to have an alert early postpartum when compared with cows that did not have KET. Mean genomic expected milk production (± SD) was 256.8 ± 600.1 kg. There was no interaction between GEM and parity on estrous expression (i.e., intensity and duration). There was no interaction between GEM and GDPR on the proportion of estrus early postpartum.
Assuntos
Lactação , Leite , Feminino , Gravidez , Bovinos , Animais , Núcleo Familiar , Taxa de Gravidez , Brasil , Genômica , EstroRESUMO
Three experiments were designed to evaluate the effects of conventional and sexed-semen on reproductive performance of dairy females detected in estrus. In Exp. 1, 978 lactating Holstein cows and 116 Holstein heifers were used. Cows or heifers were randomly assigned to receive conventional (CONV) or sexed (SEXD) semen on day 0 of a TAI protocol. The TAI was performed using commercial CONV or SEXD frozen-thawed semen from the same 6 Holstein bulls, and SEXD semen was sexed through fluorescence cytometry. In Exp. 2, 390 lactating Holstein × Gir dairy cows and 344 Holstein × Gir heifers were used. Cows and heifers were randomly assigned to receive CONV or SEXD semen on day 0 with frozen-thawed semen from 5 Holstein × Gir bulls. The SEXD was sorted through the Sexcel™ methodology. In Exp. 3, 789 primiparous lactating Holstein cows were enrolled. Cows were randomly assigned to receive CONV or SEXD semen from 5 Holstein bulls, and the SEXD semen was sexed using the same semen allocation methodology described in Exp. 2. All data were analyzed using SAS. Regardless of the experiment, no treatment × bull interaction was observed for any of the variables analyzed herein (P ≥ 0.20). In Exp. 1, multiparous cows assigned to CONV had a greater P/AI vs. cohorts assigned to SEXD (P < 0.01) and a similar response tended to be observed for secundiparous cows (P = 0.10). No treatment effects were further observed when the effects of semen on day 60 P/AI were stratified by heat stress, milk yield, and CL at the beginning of the protocol. In Exp. 2, no P/AI differences between treatment were detected either on days 32 (P = 0.32) or 60 of pregnancy (P = 0.20). In Exp. 3, cows assigned to SEXD had reduced P/AI on day 32 (P = 0.03) and tended to have a reduced P/AI on day 60 of pregnancy (P = 0.06). No further treatment effects or interactions were observed herein (P ≥ 0.13). Overall P/AI of SEXD semen was 78% of the CONV (P < 0.01), but the variation of these results requires some attention. Moreover, an additional analysis was performed considering the median value of P/AI in bulls assigned to CONV and SEXD, and bulls that had a greater P/AI in CONV also had a greater P/AI in SEXD (P = 0.03). In summary, although not directly comparable, the sexing technologies herein provided similar results in heifers, but not in other categories (primiparous, secundiparous, and multiparous cows). Additionally, the P/AI of a sexed semen is associated to its performance on the conventional semen counterpart. Moreover, in the present experiment, no other parameters were shown to impact fertility of dairy females assigned to conventional or sexed-semen.
RESUMO
This experiment was designed to evaluate the effects of increasing doses of estradiol cypionate (ECP) and different body condition score (BCS) on reproductive performance of Bos indicus beef females assigned to a timed-artificial insemination (TAI) management. In this experiment, 1683 Bos indicus Nellore cows were blocked by parity and assigned to receive 1) an intravaginal P4 device (1.9 g of P4) and 2.0 mg of estradiol benzoate on day -11, 12.5 mg (i.m.) of dinoprost tromethamine, 300 IU (i.m.) of equine chorionic gonadotrophin, 0.6 mg (i.m.) of estradiol cypionate and CIDR withdrawal on day -2, followed by TAI on day 0 (n = 849; 0.6ECP) or 2) the same synchronization protocol with 1.0 mg of ECP on day -2 (n = 834; 1.0ECP). In both treatments, estrus expression was measured between days -2 and 0. Body condition score (BCS) was evaluated on days -11, 31, and 71 of the experiment and the BCS variation (Δ) was also determined between these timepoints. Transrectal ultrasonography was performed on days 31, 71, and 111 for pregnancy rate determination. All binary data were analyzed using cow as the experimental unit with GLIMMIX, whereas continuous variables were analyzed with the MIXED procedure of SAS. No treatment effects were observed on estrus expression rate. Treatment × BCS interactions were observed for pregnancy rates in all time points (days 31, 71, and 111), as 1.0ECP cows with a LOW BCS also had a greater P/AI than cows assigned to 0.6ECP. In summary, increasing the dose of ECP benefited the reproductive performance of Nellore beef cows with a reduced BCS (≤2.75), whereas no benefits were seen when the BCS was considered adequate (>2.75).
Assuntos
Estradiol , Progesterona , Gravidez , Feminino , Bovinos , Animais , Cavalos , Progesterona/farmacologia , Estradiol/farmacologia , Reprodução , Taxa de Gravidez , Inseminação Artificial/veterinária , Inseminação Artificial/métodos , Dinoprosta/farmacologia , Sincronização do Estro/métodos , Hormônio Liberador de GonadotropinaRESUMO
This study was designed to evaluate whether the utilization of a second PGF2α treatment at the end of an estradiol/progesterone (E2/P4)-based protocol with or without GnRH at the beginning of the protocol would improve pregnancy rates of lactating Holstein cows assigned to timed embryo transfer. A total of 501 lactating Holstein cows in 5 farms were enrolled in the experiment. Within farm, cows were blocked by parity and, within block, were assigned randomly to (1) insertion of an intravaginal P4 device (controlled internal drug-releasing device; CIDR) and estradiol benzoate on d -11, PGF2α on d -4, CIDR withdrawal and an injection of estradiol cypionate on d -2, and timed embryo transfer on d 7 (1-PGF; n = 164); (2) the same treatments as 1-PGF, but with PGF2α administered on d -4 and -2 (2-PGF; n = 171); and (3) 2-PGF with the addition of a GnRH treatment on d -11 (GnRH+2-PGF; n = 166). Ovaries were scanned by transrectal ultrasonography on d -11, -4, and 7, and blood samples were collected on d -11, -4, 0, and 7 for P4 determination. Treatment comparisons were performed using contrasts. The proportion of cows with a new corpus luteum on d -4 was greater in GnRH+2-PGF cows. Cows in 1-PGF had a greater P4 concentration on d 0 but lesser P4 on d 7 compared with cows in the other groups. Cows assigned to receive 2-PGF (2-PGF and GnRH+2-PGF) had greater estrus expression, and a greater proportion of cows ovulated to estradiol cypionate. No further contrast effects were observed for follicle diameter, double ovulation rate, pregnancy per embryo transfer (P/ET) on d 32 and 60, or pregnancy loss. As P4 concentration on d -4 increased, P/ET on d 60 tended to increase. Cows with P4 ≥3.66 ng/mL on d -4 had greater P/ET on d 32 and 60 than those with P4 below that threshold. Regardless of treatment, cows with P4 concentration ≥3.66 ng/mL also had a greater pregnancy per synchronized protocol (P/SP) on d 60. Also, a P4 concentration on d -4 (low or high) × follicle diameter (continuous) interaction tendency was observed when evaluating P/ET. Although P/ET did not differ among cows with different follicles sizes with reduced P4 concentration on d -4 (<3.66 ng/mL), it increased in cows with larger follicles exposed to increased P4 concentration (≥3.66 ng/mL). When P4 on d 0 was evaluated, P/ET on d 32 and 60 was greater for cows with low (≤0.09 ng/mL) versus high (>0.21 ng/mL) P4; as P4 concentration on d 0 increased, P/ET linearly decreased. In summary, cows with increased P4 concentrations during growth of the ovulatory follicular wave had improved P/ET. Administering a second PGF2α dose reduced P4 concentration on d 0 and increased ovulatory response to the protocol, but no benefits were observed on P/ET or P/SP.
Assuntos
Hormônio Liberador de Gonadotropina , Progesterona , Gravidez , Feminino , Bovinos , Animais , Hormônio Liberador de Gonadotropina/farmacologia , Lactação , Dinoprosta/farmacologia , Sincronização do Estro/métodos , Estradiol , Ovulação , Transferência Embrionária/veterinária , Inseminação Artificial/veterináriaRESUMO
This experiment evaluated pregnancy rates to fixed-time artificial insemination (FTAI) in Bos indicus beef cows according to their body condition score (BCS) at calving and subsequent change until 30 days after FTAI. Non-pregnant, suckling Nelore cows (n = 593 primiparous, 461 secundiparous, and 893 multiparous) were evaluated for BCS at calving and FTAI, and at 30 days after FTAI when cow pregnancy status was verified. Cow BCS at calving was subtracted from BCS recorded at pregnancy diagnosis, and cows classified as those that lost BCS (L), maintained BCS (M), or gained BCS (G) during this period. Cows that calved with BCS ≥ 5.0 had greater (P < 0.01) BCS throughout the experiment, and greater (P < 0.01) pregnancy rates to FTAI compared with cows that calved with BCS < 5.0 (54.8 vs. 34.2%). Pregnancy rates to FTAI were greater (P < 0.01) for G and M cows compared with L cows (50.0%, 47.5%, and 36.0%, respectively), and similar (P = 0.46) between G and M cows. Moreover, pregnancy rates to FTAI in G cows that calved with BCS < 5.0 were less compared with L (tendency; P = 0.08) and M cows (P < 0.01) that calved with BCS ≥ 5.0 (42.2%, 48.3%, and 58.3%, respectively). In summary, pregnancy rates to FTAI were greater in B. indicus cows that calved with a BCS ≥ 5.0 regardless of parity and post-calving BCS change, and greater in M and G cows within those that calved with BCS < 5.0 or ≥ 5.0.
Assuntos
Sincronização do Estro , Inseminação Artificial , Animais , Bovinos , Feminino , Inseminação Artificial/veterinária , Paridade , Parto , Gravidez , Taxa de GravidezRESUMO
This experiment was designed to evaluate the effects of increasing doses of estradiol cypionate (ECP) on reproductive function of lactating dairy cows during the summer. In Exp. 1, 643 lactating Holstein cows were blocked by parity and assigned to receive 1) an intravaginal P4 device (1.9 g of P4) and 2.0 mg of estradiol benzoate on day -11, 25 mg (i.m.) of dinoprost tromethamine on day -4, 1.0 mg (i.m.) of estradiol cypionate and CIDR withdrawal on day -2, followed by TAI on day 0 (n = 326; ECP-1) or 2) the same synchronization protocol with 2.0 mg of ECP on day -2 (n = 317; ECP-2). In both treatments, cows were TAI on day 0 of the protocol, and cow rectal temperature was measured on days -2, 0, and 7. In Exp. 2, 608 lactating crossbred Holstein × Gir dairy cows were blocked by parity and enrolled to the same treatments as in Exp. 1, but on day 7, cows received one viable embryo into the uterine horn. In Exp. 1, a greater percentage of ECP-2 cows were detected on estrus (81.3 vs. 91.1%, respectively). A treatment × body condition score (BCS) interaction was observed on day 60 pregnancy per AI (P/AI), as ECP-2 cows with a BCS <2.75 had a greater P/AI vs. ECP-1, but an opposite result was observed in cows with a BCS ≥2.75. Regardless of treatment, there were effects of mean rectal temperature and heat stress events on P/AI. Treatment affected the diameter of the ovulatory follicle at TAI (ECP-1 = 15.3 mm vs. ECP-2 = 14.8 mm) and a greater percentage of ECP-1 cows had larger follicles (≥16.5 mm), but ECP-2 resulted in a greater incidence of early ovulatory cows (ovulating before day 0). Therefore, follicle diameter at TAI affected P/AI on day 60 in cows receiving ECP-2 and tended to affect ECP-1 cows. A treatment effect was observed on time to estrus following ECP treatments and a reduced proportion of ECP-2 cows showed estrus at TAI. Regardless of treatment, cows detected on estrus 48 h after ECP administration had a greater P/AI on day 60 vs. cows detected on estrus 24 h. In Exp. 2, a greater percentage of ECP-2 cows were detected on estrus (68.3 vs. 81.4%, respectively). In summary, a greater dose of ECP increased the percentage of animals expressing estrus, but it did not benefit the reproductive function of lactating dairy cows during the summer, regardless if animals were assigned to a TAI or timed-embryo transfer (TET) protocol.
Assuntos
Inseminação Artificial , Lactação , Animais , Bovinos , Dinoprosta/farmacologia , Estradiol/análogos & derivados , Estradiol/farmacologia , Sincronização do Estro/métodos , Feminino , Hormônio Liberador de Gonadotropina/farmacologia , Inseminação Artificial/métodos , Inseminação Artificial/veterinária , Gravidez , Progesterona/farmacologia , Estações do AnoRESUMO
The objective was to investigate effects of progesterone (P4) dose on abundance of luteinizing hormone receptor (LHCGR), aromatase (CYP19A1), 3ß-hydroxysteroid dehydrogenase (HSD3B1), and other steroidogenic mRNA transcripts in granulosa cells from dominant follicles. Nellore heifers were assigned to one of six groups: new, first-use controlled internal drug release device (CIDR1) inserted for 5 days (Large-P4-dose-D5; n = 7) or 6 days (Large-P4-dose-D6; n = 8), prostaglandin (PG)F2α administered on D0 and 1 previously-used CIDR (CIDR3) inserted for 5 days (Small- P4-dose-D5; n = 8) or 6 days (Small-P4-dose-D6; n = 8), CIDR1 inserted on D0 and removed plus PGF2α on D5 (Large-P4-dose-proestrus (PE); n = 7), and CIDR3 and PGF2α on D0 and 1, CIDR3 removed plus PGF2α on D5 (Small-P4-dose-PE; n = 7). Duration of P4 treatment (D5 compared to D6) affected abundances of CYP19A1 mRNA transcripts, with there being greater abundances on D6 than D5 (P ≤ 0.05). Heifers treated with the large dose of P4 had a smaller dominant follicle, less serum and intra-follicular estradiol (E2) concentrations (P ≤ 0.05) and lesser LHCGR, CYP19A1, and HSD3B1 transcript abundances (P ≤ 0.05). Heifers treated to induce PE had a larger follicle diameter (P = 0.09), greater intra-follicular E2 concentrations and larger abundances of CYP19A1 mRNA transcript (P ≤ 0.05) than heifers of the D6 group. Overall, treatment with larger doses of P4 resulted in lesser abundances of LHCGR, HSD3B1, and CYP19A1 mRNA transcripts; thus, potentially leading to development of smaller dominant follicles and lesser E2 concentrations.
Assuntos
Bovinos , Sincronização do Estro/efeitos dos fármacos , Progesterona/farmacologia , Receptores do LH/metabolismo , Animais , Aromatase/genética , Aromatase/metabolismo , Enzima de Clivagem da Cadeia Lateral do Colesterol/genética , Enzima de Clivagem da Cadeia Lateral do Colesterol/metabolismo , Dinoprosta/administração & dosagem , Dinoprosta/análogos & derivados , Dinoprosta/farmacologia , Estradiol/administração & dosagem , Estradiol/análogos & derivados , Estradiol/farmacologia , Feminino , Regulação da Expressão Gênica/efeitos dos fármacos , Células da Granulosa/efeitos dos fármacos , Complexos Multienzimáticos/genética , Complexos Multienzimáticos/metabolismo , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Progesterona/administração & dosagem , Progesterona Redutase/genética , Progesterona Redutase/metabolismo , Receptores do LH/genética , Esteroide Isomerases/genética , Esteroide Isomerases/metabolismoRESUMO
The objective of this study was to compare the effects of different lengths of ovulation synchronization protocols using 2 controlled internal drug release (CIDR) devices on ovarian dynamics and pregnancy outcomes in lactating dairy cows. Lactating Holstein cows (n = 1,979) were randomly assigned to receive timed artificial insemination (TAI; d 0) following 1 of 2 treatments: (1) 9-d protocol (n = 988; 9D) with 2 intravaginal devices containing 1.9 g of progesterone (CIDR) and 2.0 mg of estradiol benzoate on day -11; 25 mg (i.m.) of dinoprost tromethamine (PG) and withdrawal of 1 CIDR on d -4; 1.0 mg (i.m.) of estradiol cypionate, second CIDR withdrawal, and PG on d -2; and TAI on d 0 and (2) 10-d protocol (n = 991; 10D) with 2 CIDR and 2.0 mg of estradiol benzoate on d -12; 25 mg of PG and withdrawal of 1 CIDR on d -4; 1.0 mg of estradiol, second CIDR withdrawal, and PG on d -2; and TAI on d 0. There was no effect of protocol on estrus detection, whereas a greater percentage of cows from 10D had ovulated close to TAI [no corpus luteum (CL) at AI and a CL at d 7] versus cows assigned to 9D protocol. A protocol × heat stress (average cow temperature ≥39.1°C on day of AI and d 7) interaction was observed in a manner that pregnancy per AI (P/AI) was greater in non-heat-stressed 10D versus 9D cows, whereas P/AI did not differ when cows were under heat stress. Furthermore, 10D protocol did not increase P/AI when all cows that received AI were included in the analysis or in cows that ovulated near TAI. However, animals assigned to 9D without any event of heat stress had a reduced P/AI when compared with cows assigned to 10D without heat stress. A protocol × CL presence at the beginning of the protocol interaction was observed and cows with a CL at the beginning of the protocol had a greater P/AI in 10D versus 9D; meanwhile, in cows without a CL, no differences on P/AI were observed. The protocol × CL presence at the beginning of the protocol interaction on P/AI was also observed for cows that ovulated near TAI. A greater percentage of cows assigned to 9D had follicles of medium size (13-15.9 mm), and greater percentage of cows assigned to 10D had larger follicles (>16 mm). Increasing the length of an estradiol with progesterone-based ovulation synchronization protocol (10D vs. 9D) increased the proportion of cows with larger follicles (>16 mm) and increased P/AI in cows without heat stress and in cows with a CL at beginning of the protocol. Moreover, the 10D protocol increased the proportion of cows with ovulation near TAI, demonstrating the effectiveness of this protocol in improving the reproductive performance of lactating Holstein cows.
Assuntos
Bovinos , Dinoprosta/análogos & derivados , Estradiol/análogos & derivados , Estradiol/farmacologia , Inseminação Artificial/veterinária , Progesterona/farmacologia , Animais , Corpo Lúteo/efeitos dos fármacos , Dinoprosta/farmacologia , Liberação Controlada de Fármacos , Estrogênios/farmacologia , Feminino , Inseminação Artificial/métodos , Lactação/efeitos dos fármacos , Ovário/efeitos dos fármacos , Ovulação/efeitos dos fármacos , Gravidez , Fatores de TempoRESUMO
O presente estudo avaliou o efeito da suplementação com OmniGen-AF® na proliferação de linfócitos e títulos de anticorpos após vacinação em bovinos leiteiros. Amostras de sangue periférico foram coletadas de 32 vacas leiteiras para quantificação dos títulos de anticorpos anti-Leptospira, e amostras de sangue periférico de 16 vacas leiteiras foram também coletadas para avaliação da proliferação de linfócitos. Observou-se que a suplementação com OmniGen-AF® aumentou a proliferação basal de linfócitos (sem estímulos) 21 dias após a vacinação (P=0,03), apesar de reduzir a proliferação de linfócitos B quando estimulada com Leptospira borgpetersenii serovar Hardjo inativada pelo calor (P=0,03). Ademais, nenhum efeito da suplementação sobre a proliferação de linfócitos no momento imediatamente anterior à vacinação e nos títulos de anticorpos anti-Leptospira foi encontrado. Além disso, a proliferação de linfócitos estimulada com lipopolissacarídeos foi maior em vacas multíparas que em primíparas 21 dias após a vacinação (P=0,03). Desse modo, o presente estudo demonstra que a suplementação com OmniGen-AF® não afetou de forma robusta a proliferação de linfócitos e os títulos de anticorpos anti-Leptospira após vacinação em vacas leiteiras sadias.(AU)
Assuntos
Animais , Feminino , Bovinos , Vacinas Combinadas/análise , Suplementos Nutricionais/análise , Fatores Imunológicos/administração & dosagem , Linfocitose/veterinária , Lipopolissacarídeos , Leptospira/imunologiaRESUMO
There are multiple factors that contribute to reduced fertility in lactating dairy cows. Recently, a reproductive tract size and position score (SPS) system was developed as a management tool to identify dairy cows with decreased fertility. The aim of this study was to evaluate the association between the SPS on fertility outcomes such as ovulation failure, pregnancy per artificial insemination (P/AI), concentration of pregnancy-associated glycoproteins (PAGs), and pregnancy loss in lactating dairy cows. Primiparous and multiparous lactating Holstein cows (n = 869) were enrolled at two locations. Location 1 (Loc. 1) in Minas Gerais, Brazil (n = 613) and location 2 (Loc. 2) in Agassiz, British Columbia, Canada (n = 256). At the time of AI (d 0), cows were classified as SPS (small [SPS1], medium [SPS2], or large [SPS3] sized reproductive tract) and ovulation failure was determined at 48 h and 7 d post-AI via ultrasonography (Loc. 2 only). Blood samples were collected on d 24 and 31 of gestation for quantification of PAGs and pregnancy diagnosis was performed via ultrasonography at d 31 and 60 post-AI (Loc. 1) and at d 31 ± 3 and 60 ± 3 post-AI (Loc. 2). Cows diagnosed pregnant at d 31 post-AI but not pregnant at d 60 were defined to have undergone late embryonic pregnancy loss. Parity was found to impact SPS (P < 0.01), as primiparous cows had a higher frequency of SPS1 and lower frequency of SPS3 when compared with multiparous cows (SPS1: 42.6 vs. 15.0%; SPS3: 7.0 vs. 22.0%, respectively). Cows classified as SPS3 had greater ovulation failure at 48 h (P = 0.04) and 7 d post-AI (P = 0.05). Cows classified as SPS1 had greater P/AI when compared to SPS2 and SPS3 (45.9 ± 3.3 vs. 37.4 ± 2.6 and 29.1 ± 3.5%, respectively; P = 0.004). There was no interaction between parity and SPS on P/AI. Pregnancy loss between 31 and 60 d post-AI was increased in cows classified as SPS3 compared to SPS2 and SPS1 (24.3 ± 0.05 vs. 11.6 ± 0.02 and 9.4 ± 0.02%, respectively; P = 0.04). Cows classified as SPS1 and SPS2 had greater concentrations of PAGs at 31 d post-AI when compared to SPS3 at both Loc.1 (P < 0.01) and Loc. 2 (P < 0.01). There was no interaction between SPS and pregnancy loss on PAGs at 24 and 31 d post- AI for either Loc. 1 (P = 0.75 and P = 0.76, respectively) or Loc. 2 (P = 0.61 and P = 0.81, respectively). In conclusion, cows that were classified as SPS3 had greater ovulation failure, reduced P/AI, similar concentrations of PAG on d 24, but decreased on d 31, and a greater incidence of pregnancy loss. Thus, size and position of the reproductive tract is associated with fertility and this scoring system could be used to make reproductive management decisions on dairy operations.
Assuntos
Doenças dos Bovinos , Sincronização do Estro , Aborto Animal , Animais , Brasil , Bovinos , Feminino , Fertilidade , Hormônio Liberador de Gonadotropina , Inseminação Artificial/veterinária , Lactação , Paridade , Gravidez , ProgesteronaRESUMO
The objectives of this study were to determine if the utilization of a presynchronization strategy would improve fertility at first artificial insemination (AI) during an E2/P4 ovulation synchronization protocol with or without GnRH administration at the beginning of the protocol. This experiment was conducted using cows (n = 665) at their first postpartum service and the following breeding treatment: CIDR insertion and 2.0 mg of estradiol benzoate (EB) on day -11; 25 mg dinoprost tromethamine (PG) on day -4; PG, CIDR withdrawal, and 1.0 mg of estradiol cypionate (ECP) on day -2; timed-AI on day 0. At 31 ± 3 days postpartum, cows were randomly allocated to one of three treatments on a weekly basis: 1) -P + GnRH: cows assigned to the breeding protocol with 100 µg of GnRH on day -11, 2) P + GnRH: cows assigned to a presynchronization protocol using CIDR insertion +2 mg EB on day -28, PG + ECP and CIDR withdrawal on day -21, and beginning of the breeding protocol plus GnRH (100 µg) on day -11, and 3) +P-GnRH: cows assigned to a presynchronization protocol and the breeding treatment without GnRH on day -11. No treatment effects were observed on P/AI at the pregnancy diagnoses on days 32 and 60, or for pregnancy losses between days 32 and 60 of pregnancy whether analyses included all cows or only cows that ovulated near TAI. Moreover, milk yield negatively affected P/AI. Cows with greater circulating P4 concentrations on day -4 had greater P/AI on day 60. Cows without CL on day -11 had a reduced P/AI and this effect was more significant in cows not treated with GnRH. Cows assigned to -P + GnRH had the lowest circulating P4 concentration on day -4 (3.4 ± 0.16 ng/mL), followed by + P-GnRH (4.56 ± 0.17 ng/mL), and +P + GnRH (5.08 ± 0.17 ng/mL) cohorts. The data of the current study suggest that the combination of a Presynch and GnRH administration at the beginning of a TAI protocol was the most effective way to increase the % of cows with a functional CL and with elevated circulating P4 concentrations at the time of PG treatment.
Assuntos
Bovinos , Estradiol/farmacologia , Sincronização do Estro/efeitos dos fármacos , Hormônio Liberador de Gonadotropina/farmacologia , Progesterona/farmacologia , Animais , Esquema de Medicação , Quimioterapia Combinada , Estradiol/administração & dosagem , Feminino , Fertilidade , Hormônio Liberador de Gonadotropina/administração & dosagem , Lactação , Ovulação/efeitos dos fármacos , Gravidez , Progesterona/administração & dosagemRESUMO
Excitable temperament disrupts physiological events required for reproductive development in cattle, but no research has investigated the impacts of temperament on growth and puberty attainment in Bos indicus females. Hence, this experiment evaluated the effects of temperament on growth, plasma cortisol concentrations and puberty attainment in B. indicus heifers. A total of 170 Nelore heifers, weaned 4 months before the beginning of this experiment (days 0 to 91), were managed in two groups of 82 and 88 heifers each (mean ± SE; initial BW=238±2 kg, initial age=369±1 days across groups). Heifer temperament was evaluated via exit velocity on day 0. Individual exit score was calculated within each group by dividing exit velocity into quintiles and assigning heifers with a score from 1 to 5 (1=slowest; 5=fastest heifer). Heifers were classified according to exit score as adequate (ADQ, n=96; exit score⩽3) or excitable temperament (EXC, n=74; exit score>3). Heifer BW, body condition score (BCS) and blood samples were obtained on days 0, 31, 60 and 91. Heifer exit velocity and score were recorded again on days 31, 60 and 91. Ovarian transrectal ultrasonography was performed on days 0 and 10, 31 and 41, 60 and 70, 81 and 91 for puberty evaluation. Heifer was declared pubertal at the first 10-day interval in which a corpus luteum was detected. Exit velocity and exit score obtained on day 0 were correlated (r⩾0.64, P<0.01) with evaluations on days 31, 60 and 91. During the experiment, ADQ had greater (P<0.01) mean BCS and BW gain, and less (P<0.01) mean plasma cortisol concentration compared with EXC heifers. Temperament × time interactions were detected (P<0.01) for exit velocity and exit score, which were always greater (P<0.01) in EXC v. ADQ heifers. A temperament × time interaction was also detected (P=0.03) for puberty attainment, which was delayed in EXC v. ADQ heifers. At the end of the experiment, a greater (P<0.01) proportion of ADQ were pubertal compared with EXC heifers. In summary, B. indicus heifers classified as EXC had reduced growth, increased plasma cortisol concentrations and hindered puberty attainment compared to ADQ heifers. Moreover, exit velocity may serve as temperament selection criteria to optimize development of B. indicus replacement heifers.
Assuntos
Bovinos/psicologia , Hidrocortisona/sangue , Temperamento , Animais , Brasil , Bovinos/sangue , Bovinos/crescimento & desenvolvimento , FemininoRESUMO
This study compared physiological and productive parameters in 3/4 Holstein × 1/4 Gir dairy cows receiving a prepartum concentrate containing ammonium chloride to reduce urine pH near 7.0 (CON; n = 17), or a commercial anionic supplement to reduce urine pH near 6.0 (SUPP; n = 17). Nonlactating, multiparous, pregnant cows were assigned to receive SUPP or CON beginning 21 d before expected date of calving. Cows were maintained in a single drylot pen with ad libitum access to corn silage, and individually received their prepartum concentrate once daily (0800 h) before calving. Cows from both treatments completely consumed their concentrate allocation within 30 min after feeding. Cow body weight and body condition score were recorded once weekly, urine pH measured every 3 d, and blood samples collected on d -21, -14, -9, -6, and -3 relative to expected calving date. After calving (d 0), cows were moved to an adjacent drylot pen with ad libitum access to water and a total mixed ration, and were milked twice daily (0600 and 1700 h). Cow body weight and body condition score were recorded once weekly and individual milk production was recorded daily until 30 d in milk (DIM). Blood samples were collected before each milking during the first 5 DIM, as well as at 6, 9, 16, 23, and 30 DIM before the morning milking. Based on actual calving dates, cows received SUPP or CON for (mean ± standard error) 19.2 ± 1.2 and 19.0 ± 0.9 d before calving, respectively. Urine pH was less in SUPP versus CON cows during the last 15 d of gestation (6.12 vs. 7.15, respectively). Milk yield during the first 5 DIM and throughout the experimental period was greater in SUPP versus CON cows (by 20 and 14%, respectively), whereas serum Ca concentrations did not differ between treatments during the first 5 DIM. Serum concentrations of fatty acids were greater in SUPP versus CON cows 3 d before and at calving (by 52 and 22%, respectively), whereas SUPP cows had lower serum glucose and cortisol concentration at calving (by 23 and 27%, respectively). Hence, the SUPP treatment decreased prepartum urine pH near 6.0 in Holstein × Gir dairy cows without depressing concentrate intake compared with CON, although total dry matter intake was not evaluated to fully investigate feed intake responses. Moreover, the SUPP treatment transiently affected serum glucose, fatty acids, and cortisol concentrations near the time of calving, and resulted in greater milk yield during the initial 30 DIM compared with CON.
Assuntos
Cloreto de Amônio/administração & dosagem , Bovinos , Lactação/fisiologia , Reprodução/fisiologia , Urina/química , Animais , Dieta , Suplementos Nutricionais , Feminino , Leite , Período Pós-Parto , Gravidez , SilagemRESUMO
This experiment evaluated the impacts of estrus expression and intensity, estimated by physical activity during a timed-AI protocol, on reproductive performance of Bos indicus-influenced beef cows. A total of 290 lactating, primiparous, and multiparous nonpregnant Nelore × Angus cows received a 2 mg injection of estradiol benzoate and an intravaginal progesterone (P4) releasing device (CIDR) on d -11, a 12.5 mg injection of PGF2α on d -4, CIDR removal in addition to 0.6 mg injection of estradiol cypionate and 300 IU injection of eCG on d -2, and timed-AI on d 0. Cows were fitted with a pedometer behind their left shoulder on d -4. An estrus detection patch was attached to the tail-head of each cow on d -2. Pedometer results were recorded on d -2 and 0. Estrus expression was defined as removal of >50% of the rub-off coating from the patch on d 0. Net physical activity during estrus was calculated by subtracting total steps from d -4 to -2 (nonestrus basal activity) from total steps from d -2 to 0 (proestrus + estrus period) of each cow. Cows that did not express estrus were classified as NOESTR. Cows that expressed estrus were ranked by net physical activity; those above the median were classified as HIESTR and the remaining cows as LWESTR. Ovarian ultrasonography was performed on d 0 and 7. Blood was collected on d 0, 7, 20, and 30. Pregnancy status was verified by ultrasonography on d 30. Only data from cows responsive to the estrus synchronization protocol were utilized (NOESTR, n = 59; LWESTR, n = 100; HIESTR, n = 98). Diameter of dominant follicle on d 0, corpus luteum volume on d 7, and plasma P4 concentrations on d 7 were greater (P ≤ 0.05) in HIESTR vs. LWESTR and NOESTR and also greater (P ≤ 0.05) for LWESTR vs. NOESTR. Plasma P4 concentrations on d 0 were greater (P < 0.01) in NOESTR vs. HIESTR and LWESTR and similar (P = 0.93) between HIESTR and LWESTR. Whole blood mRNA expression of myxovirus resistance 2 on d 20 was greater (P ≤ 0.05) in HIESTR vs. LWESTR and NOESTR, and similar (P = 0.72) between LWESTR and NOESTR. Pregnancy rates were less (P ≤ 0.04) in NOESTR vs. HIESTR and LWESTR (52.4%, 68.9%, and 73.5%, SEM = 7.2), and similar (P = 0.57) between HIESTR and LWESTR. Hence, expression of estrus during a timed-AI protocol improved ovarian dynamics and pregnancy success, whereas estrus intensity modulated key biological markers associated with fertility but not pregnancy rates in B. indicus-influenced cows beef cows.
Assuntos
Bovinos/fisiologia , Sincronização do Estro/métodos , Estro/efeitos dos fármacos , Inseminação Artificial/veterinária , Administração Intravaginal , Animais , Dinoprosta/administração & dosagem , Dinoprosta/farmacologia , Estradiol/administração & dosagem , Estradiol/análogos & derivados , Estradiol/farmacologia , Feminino , Fármacos para a Fertilidade Feminina/administração & dosagem , Fármacos para a Fertilidade Feminina/farmacologia , Inseminação Artificial/métodos , Folículo Ovariano , Gravidez , Progesterona/administração & dosagem , Progesterona/sangue , Progesterona/farmacologiaRESUMO
This experiment compared insulin sensitivity, milk production, and reproductive outcomes in dairy cows consuming excessive energy during mid to late lactation and receiving in a 2 × 2 factorial design (1) concentrate based on ground corn (CRN; n = 20) or including 8% (DM basis) of Ca salts of palm oil (CSPO; n = 20), and (2) supplemented (n = 20) or not (n = 20) with 2.5 g/d of Cr-propionate. During the experiment (d 0-203), 40 multiparous, nonpregnant, lactating 3/4 Holstein × 1/4 Gir cows (initial days in milk = 81 ± 2; mean ± SE) were offered corn silage for ad libitum consumption, and individually received concentrate formulated to allow diets to provide 160% of their daily net energy for lactation requirements. From d -15 to 203, milk production was recorded daily, blood samples collected weekly, and cow body weight (BW) and body condition score (BCS) recorded on d 0 and 203. For dry matter intake evaluation, cows from both treatments were randomly divided in 5 groups of 8 cows each, and allocated to 8 individual feeding stations for 3 d. Intake was evaluated 6 times/group. Glucose tolerance tests (GTT; 0.5 g of glucose/kg of BW) were performed on d -3, 100, and 200. Follicle aspiration for in vitro embryo production was performed via transvaginal ovum pick-up on d -1, 98, and 198. Mean DMI, net energy for lactation intake, as well as BW and BCS change were similar across treatments. On average, cows gained 40 kg of BW and 0.49 BCS during the experiment. Within weekly blood samples, CRN cows had lower serum concentrations of glucose, insulin, fatty acids, and insulin-to-glucose ratio compared with CSPO cows, suggesting increased insulin sensitivity in CRN cows. During the GTT, insulin-sensitivity traits were also greater in CRN versus CSPO cows. Supplemental Cr-propionate resulted in lower serum insulin concentrations and insulin-to-glucose ratio within CRN cows only, indicating that Cr-propionate improved basal insulin sensitivity in CRN but not in CSPO cows. During the GTT, however, Cr-propionate supplementation reduced hyperinsulinemia and insulin-to-glucose ratio across CSPO and CRN cows. Milk production, as well as number of viable oocytes collected and embryos produced within each aspiration, were not affected by treatments. Hence, replacing corn by Ca salts of palm oil in the concentrate did not improve insulin sensitivity in Holstein × Gir dairy cows consuming excessive energy during mid to late lactation, whereas Cr-supplementation was effective in improving basal insulin sensitivity in cows not receiving Ca salts of palm oil.
Assuntos
Cálcio/farmacologia , Cromo/farmacologia , Suplementos Nutricionais , Óleo de Palmeira/farmacologia , Propionatos/farmacologia , Reprodução/efeitos dos fármacos , Animais , Glicemia/efeitos dos fármacos , Peso Corporal , Bovinos , Dieta/veterinária , Ácidos Graxos/sangue , Feminino , Insulina/sangue , Resistência à Insulina , Lactação/efeitos dos fármacos , Distribuição Aleatória , Silagem , Zea maysRESUMO
The objective of this study was to assess the impact of mastitis-causing bacteria and somatic cell count (SCC) on pregnancy per embryo transfer (P/ET) in Holstein-Gir crossbred (Girolando) lactating dairy cows. Cows (nâ¯=â¯1397) were subjected to a timed-embryo transfer protocol. Milk samples were collected two days before embryo transfer for SCC and bacteriological culture analyses. Pregnancy diagnosis was performed on days 31 and 66 after timed-embryo transfer. The animals were grouped according to the National Mastitis Council recommendations: Gram-positive environmental (EV+), Gram-negative environmental (EV-), Gram-positive contagious (C+), coagulase-negative staphylococci (CNS) and control (no bacterial growth). Additional analysis was made by categorizing bacteria based on degree of pathogenicity (Major or Minor). Bacterial growth reduced P/ET (Pâ¯<â¯.01) at both 31 and 66 days of gestation. The P/ET was lower (Pâ¯<â¯.05) at 31 days in EV- (30.1%) and EV+ (29.9%) groups and tended (P = .09) to be lower in the C+ group (36.6%) than the control group (44.0%). The P/ET from the Major group at 31 days of gestation was lower (P = .03) compared with the Minor and control groups (32.1 vs 41.1 vs 43.2%, respectively). Cows with SCC > 400,000â¯cells/mL had lower P/ET (Pâ¯<â¯.01) than animals with SCCâ¯<â¯200,000â¯cells/mL at both 31 (30.4% vs 40.8%) and 66 days (24.7% vs 32.2%) of gestation. Pregnancy loss was not different between bacterial isolates and SCC categories. Elevated SCC significantly reduced P/ET, whereas environmental agents and those with Major pathogenicity yielded the greatest reduction in P/ET.
Assuntos
Transferência Embrionária/veterinária , Mastite Bovina/microbiologia , Animais , Bovinos , Feminino , Fertilidade , Infertilidade Feminina/microbiologia , Mastite Bovina/complicações , Leite/citologia , Leite/microbiologia , GravidezRESUMO
Two treatments designed to increase circulating progesterone concentration (P4) during preovulatory follicle development were compared. One treatment used 2 intravaginal P4 implants (controlled internal drug-releasing inserts; CIDR) and the other used a GnRH treatment at beginning of the protocol. Lactating Holstein cows that had been diagnosed as nonpregnant were randomly assigned to receive timed artificial insemination (TAI) following 1 of 2 treatments (n = 1,638 breedings): (1) GnRH: CIDR+ 2 mg of estradiol (E2) benzoate + 100 µg of GnRH on d -11, PGF2α on d -4, CIDR withdrawal + 1.0 mg of E2-cypionate + PGF2α) on d -2, and TAI on d 0; or (2) 2CIDR: 2 CIDR + 2 mg of E2-benzoate on d -11, 1 CIDR withdrawn + PGF2α on d -4, second CIDR withdrawn + 1.0 mg of E2-cypionate + PGF2α on d -2, and TAI on d 0. Milk yield was measured daily between d 0 and d 7. Rectal temperature was measured using a digital thermometer at d 0 and 7, and elevated body temperature was defined as an average rectal temperature ≥39.1°C. Pregnancy diagnoses were performed on d 32 and 60 after TAI. We detected no effect of treatments on pregnancy per AI or pregnancy loss regardless of elevated body temperature, body condition score, parity, milk yield, or presence or absence of a corpus luteum (CL) on d -11 or d -4. Pregnancy per AI at 60 d was reduced [elevated body temperature = 22.8% (162/709), no elevated body temperature 34.1% (279/817)] and pregnancy loss tended to increase [elevated body temperature = 20.2% (41/203), no elevated body temperature 14.4% (47/326)] in cows with elevated body temperature. Various physiological measurements associated with greater fertility were also reduced in cows with elevated body temperature, such as percentage of cows with a CL at PGF2α (decreased 7.9%), ovulatory follicle diameter (decreased 0.51 mm), expression of estrus (decreased 5.1%), and ovulation near TAI (decreased 2.8%) compared with cows without elevated body temperature. A greater proportion of cows (30.2%) had a CL at PGF2α in the GnRH treatment [74.1% (570/763)] than in the 2CIDR treatment [56.9% (434/763)]; however, circulating P4 concentration was greater at the time of PGF2α treatment (d -4) for cows 2CIDR (4.26 ± 0.13 ng/mL) than in cows in GnRH (3.99 ± 0.14 ng/mL). Thus, these 2 protocols yield similar fertility results that might be due to somewhat different physiological alterations. Treatment with GnRH increased the proportion of cows with a CL at PGF2α; however, the 2CIDR protocol increased circulating P4 under all circumstances.
Assuntos
Temperatura Corporal , Hormônio Liberador de Gonadotropina/administração & dosagem , Inseminação Artificial/veterinária , Progesterona/administração & dosagem , Progesterona/sangue , Animais , Benzoatos/administração & dosagem , Bovinos , Corpo Lúteo , Dinoprosta/administração & dosagem , Implantes de Medicamento/administração & dosagem , Estradiol/administração & dosagem , Sincronização do Estro , Feminino , Inseminação Artificial/métodos , Lactação , GravidezRESUMO
This study compared vaginal temperature, physiologic, and productive parameters in lactating dairy cows supplemented or not with Omnigen-AF (Phibro Animal Health, Teaneck, NJ) during the summer months in a tropical environment. Thirty-two lactating, primiparous (n = 16) and multiparous (n = 16) pregnant Holstein × Gir cows were ranked by parity, days in milk, body weight, and body condition score (BCS), and assigned to receive (SUPP; n = 16) or not (CON; n = 16) Omnigen-AF (Phibro Animal Health, Teaneck, NJ) at 56 g/cow daily (as-fed basis). During the experimental period (d -6 to 56), cows were maintained in a single drylot pen with ad libitum access to water and a total mixed ration, and milked twice daily. Cows received Omnigen-AF mixed with 200 g of corn (as-fed basis) after the daily morning milking through self-locking head gates, whereas CON cows concurrently received 56 g of kaolin mixed with 200 g of corn. For feed intake evaluation, cows from both treatments were randomly divided in 4 groups of 8 cows each, and allocated to 8 individual feeding stations for 3 d. Intake was evaluated 4 times per group from d 1 to 56. From d -6 to 0, d 15 to 28, and d 43 to 56, cow vaginal temperature was recorded hourly. Environmental temperature-humidity index (THI) was also recorded hourly from d 15 to 28 and d 43 to 56. Cows were evaluated for body weight and BCS on d -6 and 56, individual milk production was recorded daily from d -6 to 56, and milk samples were collected on d -6, 0, 7, 14, 21, 28, 35, 42, 49, and 56 for analyses of somatic cell count and milk components. Blood samples were collected on d -6, -3, 0, 9, 15, 18, 21, 24, 27, 36, 45, 48, 51, 54, and 56. Results from samples or observations collected from d -6 to 0 were included as an independent covariate in each respective analysis. Environmental THI was 74.2 ± 0.5 and cows were exposed to THI >68 for 633 h within a total of 672 h of evaluation. Cows assigned to CON had greater vaginal temperature on d 28, 43, 45, and from d 48 to 55 (by 0.38 to 0.52%), as well as greater mean somatic cell count (by 97%) and serum haptoglobin concentrations (by 89%) compared with SUPP cows. Cows assigned to SUPP had greater mean dry matter intake (by 7%), BCS on d 56 (by 11%), and mean serum insulin concentrations (by 35%) compared with CON cows. Hence, SUPP ameliorated hyperthermia, improved nutritional status, and modulated systemic and mammary gland immune parameters in lactating dairy cows exposed to heat stress conditions.
Assuntos
Ração Animal , Regulação da Temperatura Corporal/fisiologia , Doenças dos Bovinos/fisiopatologia , Transtornos de Estresse por Calor/veterinária , Imunomodulação , Lactação/fisiologia , Animais , Peso Corporal , Bovinos , Doenças dos Bovinos/sangue , Doenças dos Bovinos/imunologia , Dieta , Suplementos Nutricionais , Feminino , Transtornos de Estresse por Calor/sangue , Transtornos de Estresse por Calor/imunologia , Transtornos de Estresse por Calor/fisiopatologia , Temperatura Alta/efeitos adversos , Umidade , Lactação/imunologia , Leite/metabolismo , Paridade , Gravidez , Vagina/fisiopatologiaRESUMO
This experiment compared insulin sensitivity parameters, milk production and reproductive outcomes in lactating dairy cows consuming excessive energy, and receiving in a 2×2 factorial arrangement design: (1) concentrate based on ground corn (CRN; n=13) or citrus pulp (PLP; n=13), and (2) supplemented (n=14) or not (n=12) with 2.5 g/day of chromium (Cr)-propionate. During the experiment (day 0 to 182), 26 multiparous, non-pregnant, lactating Gir×Holstein cows (initial days in milk=80±2) were offered corn silage for ad libitum consumption, and individually received concentrate formulated to allow diets to provide 160% of their daily requirements of net energy for lactation. Cow BW and body condition score (BCS) were recorded weekly. Milk production was recorded daily and milk samples collected weekly. Blood samples were collected weekly before the morning concentrate feeding. Glucose tolerance tests (GTT; 0.5 g of glucose/kg of BW) were performed on days -3, 60, 120 and 180. Follicle aspiration for in vitro embryo production was performed via transvaginal ovum pick-up on days -1, 82 and 162. No treatment differences were detected (P⩾0.25) for BW and BCS change during the experiment. Within weekly blood samples, concentrations of serum insulin and glucose, as well as insulin : glucose ratio were similar among treatments (P⩾0.19), whereas CRN had less (P<0.01) non-esterified fatty acid concentrations compared with PLP (0.177 v. 0.215 mmol/l; SEM=0.009). During the GTT, no treatment differences were detected (P⩾0.16) for serum glucose concentration, glucose clearance rate, glucose half-life and insulin : glucose ratio. Serum insulin concentrations were less (P=0.04) in CRN supplemented with Cr-propionate compared with non-supplemented CRN (8.2 v. 13.5 µIU/ml, respectively; SEM=1.7), whereas Cr-propionate supplementation did not impact (P=0.70) serum insulin within PLP cows. Milk production, milk fat and solid concentrations were similar (P⩾0.48) between treatments. However, CRN had greater (P<0.01) milk protein concentration compared with PLP (3.54% v. 3.14%, respectively; SEM=0.08). No treatment differences were detected (P⩾0.35) on number of viable oocytes collected and embryos produced within each aspiration. In summary, feeding a citrus pulp-based concentrate to lactating dairy cows consuming excessive energy did not improve insulin sensitivity, milk production and reproductive outcomes, whereas Cr-propionate supplementation only enhanced insulin sensitivity in cows receiving a corn-based concentrate during a GTT.