RESUMO
This study was conducted to compare efficacy of treatments with EB or GnRH and different quantities of exogenous progesterone (P4) for synchronization of time of ovulation on follicular growth and pregnancy in lactating dairy cows. In Experiment 1, 40 cows were treated with EB or GnRH and 1.9 or 3.0 g of P4 via progesterone-containing intravaginal devices (IVPD; D0), two doses of PGF2α on D7, GnRH on D9, and TAI on D10. In Experiment 2, 1,440 cows were treated with EB or GnRH and 1 g IVPD on D0, cloprostenol, eCG and EB on D7. Cows in estrus by 48 h were AIDE, and non-estrous cows were administered GnRH and TAI 60 h after IVPD removal. Non-estrous cows were AIDE 72 h after IVPD removal. In Experiment 1, P4 was greater on D7 for cows treated with GnRH than those treated with EB. The dominant follicle was larger for cows treated with GnRH than those treated with EB. In Experiment 2, for estrous cows, pregnancy per AI was greater in cows AI at 48 h compared to 60 h after IVPD removal for cows treated with GnRH, and greater with AI at 60 h after IVPD removal compared to 48 h in EB-treated cows. In non-estrous cows, there was no effect on pregnancy. In conclusion, treatment with GnRH compared with EB resulted in increased P4 regardless of amount of exogenous P4, and there were differential proportions of estrous cows pregnant depending on time of AI after IVPD removal.
Assuntos
Bovinos/fisiologia , Estradiol/farmacologia , Hormônio Liberador de Gonadotropina/farmacologia , Lactação/fisiologia , Folículo Ovariano/efeitos dos fármacos , Progesterona/farmacologia , Administração Intravaginal , Animais , Estradiol/administração & dosagem , Feminino , Hormônio Liberador de Gonadotropina/administração & dosagem , Inseminação Artificial/veterinária , Paridade , Gravidez , Progesterona/administração & dosagemRESUMO
The objective was to assess the effect of biostimulation by the male presence and social organization on the interval from calving to resumption of ovarian cyclicity (ICR). Thirty Angus cows were allocated according parity into three groups (10 per group); two groups were exposed to bulls, and a third group not exposed to bulls served as a control. Dominance values (with subsequent arc-sin transformation) were calculated from daily recorded agonistic interactions and later organized into dominance order comprising three social categories as follows: dominant (D), intermediate (I), and subordinates (S). The ICR was established by determining presence of luteal tissue and a rise of blood progesterone concentration above 1 ng/mL using ultrasonography and a solid-phase, nonextraction radioimmunoassay (Coat-a-Count; Diagnostics Products Corporation, Los Angeles, CA, USA), respectively. The effect of biostimulation, dominance order, and treatment by dominance order on ICR was statistically analyzed applying ANOVA using PROC GLM of SAS (2010). The ICR was influenced by biostimulation (P < 0.002) and dominance order (P < 0.004). The ICR increased as dominance order decreased (D = 34.5 ± 6 days; I = 45.0 ± 6; S = 53.1 ± 4 days; P < 0.01). However, when comparing cows within social categories, ICR was reduced in the group exposed to bulls (D = 26.3 ± 8.2 days; I = 42.0 ± 6.4 days; S = 46.1 ± 4.1 days) compared with those not exposed to bulls (D = 43.0 ± 8.2 days; I = 48.0 ± 10.1 days; S = 60.2 ± 6.4 days) cows. In conclusion, biostimulation and social dominance influenced the ICR.
Assuntos
Bovinos/fisiologia , Ciclo Estral/fisiologia , Período Pós-Parto , Predomínio Social , Animais , Corpo Lúteo/crescimento & desenvolvimento , Feminino , Masculino , Progesterona/sangue , Comportamento Sexual Animal , Comportamento SocialRESUMO
The objective was to describe the relationship between concentration of serum nonesterified fatty acids (NEFAs) at calving and the incidence of periparturient disorders in Chilean Holstein dairy cows (Bos taurus). The study was conducted at two dairies (central Chile) with 700 milking cows each and similar management. Between July 2006 and March 2007, 350 cows were selected, and concentrations of serum NEFAs were determined at calving. The incidence of milk fever (MF), retained fetal membranes (RFMs), metritis, and clinical mastitis from calving to 100 d in lactation were consistently recorded. The relationship between concentration of serum NEFAs at calving and the incidence of periparturient diseases was determined using logistic regression. The main explanatory variable was concentration of serum NEFAs at calving. The incidence of MF, RFM, metritis, and mastitis was 5.4%, 15.6%, 10.8%, and 14.4%, respectively. There was no association between concentration of NEFAs at calving and the incidence of these conditions when the median value of NEFAs (0.9 mEq/L) was used as a cutoff. However, when the 75th percentile (1.2 mEq/L) was used as the cutoff, cows with values <1.2 mEq/L were 0.45 and 0.32 times as likely to develop clinical mastitis and MF, respectively, compared with cows with values >or=1.2 mEq/L. When the 90th percentile (1.6 mEq/L) was used as a cutoff, cows with values <1.6 mEq/L were 0.25 times as likely to develop clinical mastitis compared with cows with values >or=1.6 mEq/L. As a continuous variable, for every 0.1 mEq/L increment in NEFAs at calving, cows were 1.11 times more likely to experience clinical mastitis. In conclusion, cows with NEFA concentrations >or=1.2 mEq/L had a higher incidence of clinical mastitis and MF than that of cows with values <1.2 mEq/L.
Assuntos
Doenças dos Bovinos/sangue , Ácidos Graxos não Esterificados/sangue , Animais , Bovinos , Doenças dos Bovinos/epidemiologia , Feminino , Incidência , Mastite Bovina/sangue , Mastite Bovina/epidemiologia , Complicações do Trabalho de Parto/sangue , Complicações do Trabalho de Parto/epidemiologia , Complicações do Trabalho de Parto/veterinária , Paresia Puerperal/sangue , Paresia Puerperal/epidemiologia , Parto , Gravidez , Análise de Regressão , Fatores de RiscoRESUMO
Pregnancy per artificial insemination (AI) was evaluated in dairy cows (Bos taurus) subjected to synchronization and resynchronization for timed AI (TAI). Cows (n=718) received prostaglandin F(2alpha) (PGF) on Days -38 and -24 (Days 39 and 53 postpartum), gonadotropin-releasing hormone (GnRH) on Day -10, PGF on Day -3, and GnRH and TAI on Day 0. Between Days -10 and -3, cows received a progesterone intravaginal insert (CIDR group) or no CIDR (Control group). Between Days 14 and 23, cows received a CIDR (Resynch CIDR group) or no CIDR (Resynch control group), GnRH on Day 23, with pregnancy diagnosis on Day 30. Cows in estrus (between Days 0 and 30) were re-inseminated at detected estrus (RIDE). Nonpregnant cows received PGF on Day 30 and GnRH and TAI on Day 33. Plasma progesterone was determined to be low or high on Days -24 and -10. Pregnancy rates were evaluated 30 and 55 d after AI. The CIDR insert included in the Presynch-Ovsynch protocol did not increase overall pregnancy per AI for first service (36.1% and 33.6% for CIDR; 34.1% and 28.8% for Control) but did decrease pregnancy loss (7.0% for CIDR and 15.6% for Control). The CIDR insert increased pregnancy per AI in cows with high progesterone at the time the CIDR insert was applied. Administration of a CIDR insert between Days 14 and 23 of the estrous cycle after first service did not increase overall pregnancy per AI to second service (24.7% and 22.7% for Resynch CIDR; 28.6% and 25.3% for Resynch control). For second service, RIDE cows had lower pregnancy rates in the Resynch CIDR group than in the Resynch control group. Cows with a CL (corpus luteum) at Day 30 had higher pregnancy rates in the Resynch CIDR group than those in the Resynch control group.
Assuntos
Bovinos/fisiologia , Inseminação Artificial/métodos , Lactação , Animais , Ciclo Estral , Feminino , Hormônio Liberador de Gonadotropina/farmacologia , Gravidez , Taxa de Gravidez , Progesterona/administração & dosagem , Progesterona/sangue , Progesterona/farmacologia , Prostaglandinas/farmacologiaRESUMO
The objectives were to characterize the estrus detection risk (HDR), conception risk (CR), and pregnancy rate (PR) of postpartum (pp) Holstein cattle from the central area of Chile. The study used records of 2269 lactations from six dairy farms in central Chile (Mediterranean-type climate) during 2004. Three 21-d periods for estrus detection were considered (50-70, 71-91, and 92-112d pp). Estrus detection risk, CR, and PR at the first, second, and third periods were analyzed by logistic regression, whereas overall PR at the end of the 63-d study (112d pp) was assessed with survival analysis. The overall HDR was 51.1%. The HDR, CR, and PR were 48.4, 42.2, and 17.3%, respectively, during the first period; 52.8, 41.8, and 20.5% during the second period; and 52.9, 39.2, and 19.7% during the third period. The HDR was lower during Period 1 than during Periods 2 and 3 (P< or =0.05). Conception risks were not different among periods (P>0.05); however, PR was lower during Period 1 than during Periods 2 and 3 (P< or =0.05). Overall PR over time differed among parities, but was not significantly different among seasons. There were no significant interactions among parity, season and herd for HDR, CR and PR for the three 21-d periods. Parity 1 had higher CR and PR than Parity 2 and 3+ during Period 3. Overall, survival curves for the risk of non-pregnancy among parities (1, 2, 3 or greater) were different over time (P< or =0.05). Cows of Parity 1 became pregnant earlier than cows of Parity 2, and Parity 3 or greater. Survival curves for the risk of non-pregnancy among seasons (summer, fall, winter, and spring) were not different over time (P>0.05).