Dietary Ingredients and Nutritional Management Impact Fertility in Dairy Cattle

Nutrition has an important impact on the reproductive performance of dairy and beef cattle. Energy is the major nutrient required by adult cattle. Inadequate energy intake has a detrimental effect on reproductive activity of female bovine. Cows under negative energy balance have lowered plasma glucose, insulin and IGF-I, reduced peak frequency of LH pulses, lowered plasma progesterone, and impaired ovarian activity. Incidence of postpartum anestrus and reduced fertility is magnified by losses of body condition during the early postpartum period. Inadequate, as well as excessive prepartum BCS extends postpartum anestrus and reduces conception and pregnancy rates during the breeding period. The effects of energy balance on fertility of cattle seem to be associated with metabolic and endocrine changes, as well as with reduced viability of the oocyte to be fertilized. Dietary manipulations that alter the supply of energy to high producing cows may ameliorate their reproductive performance. Feeding diets that promote higher plasma glucose and insulin may improve the metabolic and endocrine status of cows. Addition of supplemental fat to the diet improves energy intake, alters PGF2α secretion by the uterus, affects ovarian dynamics, enhances luteal function, and improves fertility. Although cottonseed feeding and gossypol intake seem to not affect lactation performance of dairy cows, it may affect fertility when the resulting plasma gossypol concentrations are excessive. Excessive intake of dietary crude protein or ruminally degradable protein increases urea nitrogen concentration in blood and milk and alters uterine function, which may impair conception rates. Although evidence suggests that protein may interfere with reproduction, dietary changes should not be made in detriment to production and profitability. INTRODUCTION Relationships between nutrition and reproduction in dairy and beef cattle have been extensively reviewed. The impact of nutrition on fertility of dairy herds may be caused by direct and indirect effects of nutrients on reproductive tissues. As the demands for milk synthesis increase, reproductive functions may be depressed when no compensatory intake of nutrients is achieved. Numerous recent studies have reported that reproductive performance is compromised by the nutrient demands when high levels of production are obtained. The peak milk yield occurs 4 to 6 weeks prior to the peak of dry matter intake (DMI) and high yielding cows will experience some degree of negative balance of energy and other nutrients during the early postpartum period. 1 Santos, J.E.P. 2001. Dietary ingredients and nutritional management impact fertility in dairy cattle. In Proc. 36 Pacific Northwest Animal Nutrition Conference. Boise, ID. pp. 189-219.