Because heifers are still growing, even when calving at 24 months, they need a diet rich in protein but moderate in energy to avoid getting too fat.
It’s no secret that good reproductive performance on dairies involves a variety of factors, but often components of reproductive programs get blamed when cows don’t get pregnant – which may be the wrong thing to focus on.
“People often focus on just the reproductive part of a program at one point in time, such as synchronizing cows,” says Pedro Melendez, DVM, PhD, College of Veterinary Medicine, University of Florida. “They focus on GnRH, prostaglandin, timed AI, etc., but aren’t looking at what were the situations surrounding parturition and before that, such as did she have difficulty calving, how was the transition and pre-partum period management, what was the incidence of retained fetal membranes, hypocalcemia, ketosis, etc. We blame reproductive management, but we often don’t look at the other factors that occurred before this time.”
Jose Santos, DVM, PhD, Veterinary Medicine Teaching and Research Center, University of California, believes it is very important that producers, veterinarians and nutritionists evaluate reproductive problems not only by paying attention to the reproductive management but also to other aspects, such as nutrition. “When cows experience excessive metabolic problems after calving, that will influence subsequent fertility and response to the reproductive program implemented in the herd,” he says.
Inadequate feeding of transition and early lactation cows that leads to more ketosis, hypocalcemia, displaced abomasum, etc., normally reduces subsequent fertility. In addition, it has been demonstrated that mastitis, which is prevalent early postpartum and can be influenced by nutrition, is negatively associated with conception and pregnancy maintenance in dairy cattle. “Unless these problems are corrected,” says Santos, “it is unlikely that the reproductive program will be successful.”
Melendez agrees and says studies relating calving-related disorders to fertility found that cows with hypocalcemia or milk fever were six times more likely to develop a retained fetal membrane and probably three times more likely to develop metritis. And indirectly, those cows are more likely to develop ketosis. “Finally, we end up with an animal that is cycling very late, so it’s very important to pay attention to the basic concept and look back to see what’s going on in the transition period,” says Melendez.
Nutrition can influence fertility at all stages of the reproductive cycle, but the period between late gestation and first postpartum insemination is probably the most critical. Santos says this is when a cow experiences most of the diseases during the entire lactation cycle and what happens to her in this period will determine how successful the subsequent breeding will be.
Melendez echoes that point of view. “Starting in the dry-off and transition period, the last 21 days before and after calving are the most important time periods for nutrition. The more deficiencies we have at that time, the more infertility we’re going to have in the herd. If we have a dry-off and dry period in bad shape, the transition period won’t improve anything.”
Pedro Melendez, DVM, PhD, says nutrition in the transition period has a significant effect on later fertility.