RESUMEN
The mode of action of bismuth subnitrate in teat sealant formulations as a preventative for intramammary infections during the dry period is unknown. Although previous studies proposed an action mechanism-creating a physical barrier in the teat canal to prevent bacterial invasion-it has not been proven experimentally. We hypothesized that bismuth subnitrate has an inhibitory effect on bacterial growth, in addition to its barrier effect. The objective of this study was to assess the effect of bismuth subnitrate on bacterial growth of major mastitis-causing agents. A strain of Streptococcus uberis (SR115), 2 strains of Staphylococcus aureus (SA3971/59 and SA1), and a strain of Escherichia coli (P17.14291) were tested in vitro for their ability to grow in the presence or absence of bismuth subnitrate. Disk diffusion testing, impedance measurement, and evaluation of bacterial growth in shaking conditions were the methods used to test this hypothesis. A reduction of growth in the presence of bismuth subnitrate occurred for all the strains tested. However, we observed strain and species variations in the extent of growth inhibition. These results suggest that an inhibitory effect on bacterial growth by bismuth subnitrate could partially explain the efficacy of bismuth-based formulations for preventing intramammary infections over the dry period. Further research is required to test the effect of teat sealant formulations on bacterial growth.
Asunto(s)
Bismuto/farmacología , Escherichia coli/efectos de los fármacos , Mastitis Bovina/prevención & control , Leche/microbiología , Staphylococcus aureus/efectos de los fármacos , Streptococcus/efectos de los fármacos , Animales , Bovinos , Escherichia coli/crecimiento & desarrollo , Femenino , Glándulas Mamarias Animales/microbiología , Mastitis Bovina/microbiología , Staphylococcus aureus/crecimiento & desarrollo , Streptococcus/crecimiento & desarrolloRESUMEN
AIMS: To determine the prevalence of failure of passive transfer (FPT) of maternal antibodies, to identify management factors associated with FPT, and to determine the relationship between interval from the start of calving and calf management practices on concentrations of total protein in the serum of calves, from a sample of spring-calving dairy herds in the Manawatu region of New Zealand. METHODS: This was an observational study involving 11 dairy farms in the Manawatu region serviced by Massey University Farm Services Clinic. Blood samples were collected from calves <1-week-old during August and September 2012 and concentration of total protein in serum was assessed by refractometry. FPT was defined as concentrations of total protein in serum ≤50â g/L. A questionnaire on early calf rearing practices was completed on each farm. Linear mixed and generalised linear mixed models were used to determine associations with concentrations of total protein in serum and risk of FPT. RESULTS: The mean concentration of total protein in serum for the 230 samples collected was 60.6 (SE 0.93) g/L and 57/230 (24.8 (95% CI=19.3â30.9)%) calves were diagnosed with FPT. Two variables, days from planned start of calving to when the calf was sampled, and reportedly feeding colostrum for the first 4 days post-partum, were associated with increased concentrations of total protein in serum (p<0.05). There was also an association between the odds of FPT for calves sampled in a particular week and the proportion of the total herd calving in that same week (p<0.005). CONCLUSIONS AND CLINICIAL RELEVENCE: Feeding colostrum for 4 days from birth and increasing days from planned start of calving to calf sampling were associated with increased concentrations of total protein in serum. FPT on the surveyed farms appeared to be associated with an inability to adequately manage the total number of new born calves during the busiest period of calving.
Asunto(s)
Animales Recién Nacidos/inmunología , Bovinos/inmunología , Inmunidad Materno-Adquirida , Animales , Proteínas Sanguíneas/análisis , Industria Lechera/métodos , Femenino , Nueva Zelanda , Embarazo , Encuestas y CuestionariosRESUMEN
A study was designed to compare the effects of a conventional (4 days) versus a lengthened (7 days) superstimulation protocol on follicle dynamics and to test the hypothesis that superstimulatory treatment only rescues small follicles within the wave. Nonlactating beef cows received a progesterone-releasing intravaginal device [PRID] and were superstimulated with 400-mg FSH on the day of follicle ablation-induced wave emergence (Day 0). The control group (n = 5) received FSH over 4 days, whereas the long group (n = 5) received FSH over 7 days. PGF was administered twice on Day 2 (control group) or 5 (long group), and PRIDs were removed 24 hours after the first PGF. Cows received 25-mg LH 24 hours after PRID removal. The cows chosen for the present study represented a subset from a larger group of 24 cows in which superovulation results were obtained and published. Cows in the present study were those with the lowest antral follicle counts at the time of wave emergence in order to facilitate tracking of individual follicles. Daily ultrasonographic examinations monitored follicle diameters and numbers. A reduction (P < 0.01) in the number of 1- to 2-mm follicles from Day 0 to the end of the superstimulatory treatment was associated with a progressive shift to the next size category in both groups. On the day of LH treatment, the number of follicles in any size category did not differ between groups. The number of follicles of diameter 5 mm or less decreased during superstimulation (i.e., no continuous recruitment of small follicles; P < 0.001), and the number of follicles of diameter 1 mm or greater at the end of superstimulation did not differ from that at the beginning of superstimulation (P = 0.739). However, the total number of follicles of diameter 3 mm or greater at the end was greater than the number of follicles of diameter 3 mm or greater at the beginning of superstimulation because of growth of the 1- to 2-mm population during treatment (P < 0.001). Follicle growth was slower in the long group than in the control group. Results support the hypothesis that both 4-day and 7-day superstimulatory protocols rescue small antral follicles present at the time of wave emergence; there was no evidence for continuous recruitment of new follicles. Results also provide rationale for the hypothesis that a lengthened treatment protocol is associated with greater follicle maturation and capacity to ovulate.
Asunto(s)
Bovinos/fisiología , Folículo Ovárico/efectos de los fármacos , Inducción de la Ovulación/veterinaria , Superovulación/efectos de los fármacos , Animales , Transferencia de Embrión/veterinaria , Sincronización del Estro/efectos de los fármacos , Femenino , Hormona Folículo Estimulante/farmacología , Folículo Ovárico/diagnóstico por imagen , Inducción de la Ovulación/métodos , Factores de Tiempo , UltrasonografíaRESUMEN
The study was designed to formulate intravaginal devices that provide biologically active circulating concentrations of an aromatase inhibitor for a minimum of 4 days, and to determine their physiologic effects in cattle. Three compounds with estradiol inhibitory capability (letrozole, anastrozole and fenbendazole) were tested in vitro using bovine granulosa cell culture. Letrozole was found to be the most efficient and potent inhibitor. A wax-based vehicle was selected for further development of a letrozole intravaginal device based on its steady release rate. Cycling heifers were assigned randomly to be given an intravaginal device containing wax plus gel coat (n=4), wax formulation (n=4), no formulation (blank device, control, n=4). Intravaginal devices were inserted on Day 3 (Day 0=ovulation) and kept in place for 8 days. The addition of a letrozole-containing gel coating hastened the initial increase on plasma concentrations, while the letrozole-containing wax-based vehicle maintained prolonged delivery from the intravaginal device. The dominant follicle diameter profile was larger in heifers treated with the wax plus gel coat device (P<0.04), and the interwave interval was prolonged in heifers in the letrozole-treated groups compared to controls (P<0.001). Plasma estradiol concentrations were reduced significantly in the letrozole-treated groups. Plasma progesterone concentrations were lower in the wax letrozole-treated group (P<0.02). We concluded that wax base plus gel coat intravaginal devices are suitable for the development of a letrozole-based protocol for the synchronization of ovulation in cattle. It effectively reduced estradiol production resulting in prolonged dominant follicle growth and lifespan, without adversely affecting progesterone production.
Asunto(s)
Inhibidores de la Aromatasa/farmacología , Bovinos/fisiología , Administración Intravaginal , Animales , Inhibidores de la Aromatasa/administración & dosificación , Relación Dosis-Respuesta a Droga , Estradiol/sangre , Sincronización del Estro , Femenino , Inhibición de la Ovulación/efectos de los fármacosRESUMEN
This study determined if lengthening the superstimulation protocol from 4 to 7 days would result in an increase in the superovulatory response with no adverse effects on oocyte/embryo competence in beef cows. Follicular ablation was performed, a progesterone-releasing intravaginal device (PRID) was inserted, and cows were assigned to one of two treatment groups 5 to 8 days after ovulation: Control (4 days of follicle stimulating hormone (FSH)) or Long (7 days of FSH; n=12 per group). The FSH treatments were initiated 1.5 days later (Day 0). A dose of 400 mg NIH-FSH-P1 (Folltropin-V) was distributed equally over 8 (Control) or 14 (Long) im injections at 12-h intervals. Prostaglandin F2α (PGF) was administered twice, 12 h apart, on Day 2 (Control) or Day 5 (Long), and PRID were removed 12 h after the second PGF. Both groups were given 25 mg pLH (lutropin-V) im 24 h after PRID removal and AI was done 12 and 24 h later. Ova/embryos were collected 7 days after the pLH injection. The mean (±SEM) number of ≥9 mm follicles at the time of first AI did not differ (P=0.24) between groups, but more ovulations (30.9±3.9 vs. 18.3±2.9, P=0.01) and CL (27.2±2.1 vs. 20.8±2.2, P=0.04) occurred in the Long group. A higher proportion of the ≥9 mm follicles ovulated between 12 and 36 h after pLH in the Long group (93 vs. 69%; P=0.001). Although numerically higher in the Long group, mean numbers of total ova/embryos, fertilized ova, transferable or freezable embryos did not differ. In conclusion, a lengthened superstimulatory treatment protocol resulted in more follicles acquiring the capacity to ovulate with an increased number of ovulations, and without a decrease in oocyte/embryo competence.