RESUMEN
Fertility and productive herd life (time in herd after birth of first calf) are inferior in dairy cows with relatively low compared with intermediate but not high numbers of follicles growing during ovarian follicular waves. The present study, therefore, tested the hypothesis that fertility and productive herd life are lower in dairy heifers with high follicle numbers compared with age-matched herdmates with fewer follicles. To test this hypothesis, 11 to 15 mo old Holstein heifers were subjected to a single ultrasound measurement of the number of follicles ≥3 mm in diameter. Heifers were classified into a high- (≥25 follicles), mid- (16-24), or low-range (≤15) follicle number group (FNG). All heifers not removed from the herd before first calving (n = 408) had the opportunity to start their fifth or sixth lactation after birth of their first calf. During this time, performance and health parameters for each individual were recorded daily by herd managers. Results showed that heifers in the high-range FNG had a 180-d shorter productive herd life, reduced survival rate, and greater probability of being culled after birth of the first calf, as well as fewer lactations compared with heifers in the low-range FNG. Cows in the high-compared with the mid- or low-range FNG also had greater involuntary culling rates, days open, and services per conception, and lower pregnancy rates during the first, second, or third lactations. We concluded that dairy heifers with ≥25 follicles ≥3 mm in diameter have suboptimal fertility and a shorter productive herd life compared with herdmates with fewer follicles.
Asunto(s)
Fertilidad/fisiología , Lactancia/fisiología , Folículo Ovárico/diagnóstico por imagen , Animales , Bovinos , Industria Lechera , Femenino , Folículo Ovárico/anatomía & histología , Embarazo , Índice de Embarazo , Factores de Tiempo , Ultrasonografía/veterinariaRESUMEN
Reliable biomarkers predictive of productive herd life (time in herd after birth of first calf) have heretofore not been discovered in dairy cattle. However, circulating concentrations of anti-Müllerian hormone (AMH) are positively associated with number of follicles or antral follicle count (AFC), ovarian function, and fertility, and approximately 25% of cows have a relatively low AFC and low AMH concentrations. The present study tested the hypothesis that heifers with the lowest AMH concentrations have suboptimal fertility and are removed from a herd for poor reproductive performance at a greater rate, and therefore have a shorter productive herd life compared with age-matched herdmates with higher AMH. To test this hypothesis, 11- to 15-mo-old Holstein heifers (n=281) were subjected to a single measurement of AMH. All heifers not removed from the herd had the opportunity to complete 2 lactations and start their third lactation after calving. During this time, performance and health parameters for each individual were recorded daily by herd managers. Results showed that the quartile of heifers with the lowest AMH concentration also had, on average, a shorter productive herd life (by 196 d), a reduced survival rate after birth of the first calf, the lowest level of milk production (first lactation), the lowest total percentage of cows pregnant (across all lactations), the highest culling rates (first and second lactations and overall), and the highest culling rate for poor reproduction (first lactation) compared with age-matched herdmates with higher AMH. We concluded that a single determination of AMH concentration in young adult dairy heifers may be a simple diagnostic method to predict herd longevity, and AMH may be a useful phenotypic marker to improve longevity of dairy cows.