Nutrition plays a key role in the maintenance of animal reproductive performance. Reduced reproductive efficiency can decrease the profitability of dairy production by increasing days open, calving interval, the number of services per conception, culling rate, and veterinary services. Nutritional requirements increase rapidly with milk production after calving, but an improper diet plan could result in a negative energy balance (NEB). NEB delays the time of first ovulation through uncoupled hormones production. A diet high in fat could prevent the NEB state by increasing the energy status of animals. Protein supplementation supports high production but can also have severe effects on the reproductive performance of the animal. Deficiency of minerals can also alter the reproductive performance of the animal. This article has generally focused on the effects of various nutrients on reproductive efficiency of dairy cattle.
The aim of this study was to evaluate the reproduction results of mink females, selected for the number of kits weaned in their first reproductive season. The analysis of the reproductive efficiency in two following years indicates that such criterion of mink females selection was apparently ineffective. Slightly increased litter size in the second year was followed by significant decrease in the third cycle of reproduction.