The Effect of milk production on reproductive performance in the high producing and BST supplemented dairy cow

Abstract

Higher-yielding dairy cows have reduced reproductive efficiency compared lower-yielding herdmates. This relationship is likely to be seen whether increased production is achieved through superior genetics or somatotropin (GH) supplementation. Increased days open in the high-yielding cow are most probably related to a slight delay in return of cyclic ovarian activity and reduced 1st service conception rates. Reduced fertility in the high-yielding cow is not directly related to increased milk yield but rather to loss of body wt and body condition. The magnitude of the negative impact of milk production on reproduction depends on the cumulative negative energy balance in early lactation. High-yielding cows can achieve optimal reproductive efficiency if they are given adequate energy and protein to support high levels of milk production in early lactation, and replenish adequate body condition in late lactation and the dry period. While GH-supplemented cows are similar to higher-yielding, genetically superior cows in that total milk is increased for the lactation, they may differ in the patterns of milk production over the lactation. Depending on the time of initiation of GH supplementation and the duration of administration, the GH-supplemented cow may have a greater persistency of the lactation curve. Subsequently, the GH-supplemented cow will produce a higher percentage of total milk in the latter part of lactation, changing the rate of profit accumulation. With more milk being produced in late lactation, the importance of maintaining a minimal calving interval may be reduced. The voluntary waiting period prior to mating may be intentionally extended, thereby reducing the pressures of early post-partum remating, when 1st service conception rates are often low in high-yielding cows. Maintaining profitable levels of milk production for longer lactation cycles will allow for later post-partum mating and reduce culling for reproductive failure. Reduced calvings per yr may actually extend herd life by reducing the number of disorders associated with the early post-partum period.