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Notes:
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A retrospective study involving 2756 pregnancies from two commercial dairy herds in northeastern
Spain determined relationships between management, production and reproductive data, and
high fertility (conception before 90 days in milk) in high-producing dairy cows. High fertility was
registered in 989 (35.9%) cows. The following data were recorded for each animal: herd, repeated
animal (cows included two or more times within the study in which data were obtained from different
lactational periods), parity (primiparous versus multiparous), previous twinning, reproductive
disorders following calving (retained placenta, primary metritis) and at postpartum gynecological
examination (incomplete uterine involution, pyometra and ovarian cysts), days in milk at conception,
previous estrous synchronization and season of calving and conception. In order to evaluate the
possible effect of high production during the peak milk yield on subsequent fertility, daily milk
production at Day 50 postpartum was also recorded and cows were classified as high ( 50 kg) and
low (<50 kg) producers. Logistic regression analysis indicated no significant effects of herd, repeated
animal, previous twinning, reproductive disorders such as primary metritis, incomplete uterine
involution, pyometra and ovarian cysts, previous estrous synchronization and season of calving and
insemination. Based on the odds ratio, the likelihood of high fertility increased in high-producer cows
by a factor of 6.8. High fertility was less likely for multiparous cows (by a factor of 0.35) and for cows
suffering placenta retention (by a factor of 0.65). High fertile cows produced a mean of 49.5 kg milk
at Day 50 postpartum, in contrast to that 43.2 kg milk of the remainder cows. These findings question
The authors thank Paqui Homar for assistance with data collection. García-Ispierto was supported by a FPU grant from the Ministerio de Educación y Ciencia, AP-2004-4279. |
