ABSTRACT
Deficiencies of most required nutrients, as well as some excesses and imbalances, have been shown to adversely affect reproductive performance. Several extensive general reviews have newly been published on nutritional effects on reproduction in dairy cattle. Consequently, unless new formulation techniques or feeding stra tegems can be devised to increase energy intake postpartum, the magnitude of energy deficit in early lactation will increase, and considerable evidence suggests that negative energy balance is detrimental to conception. Modest quality grass hay would provide the energy requirement and might be deficient only in phosphorus, sodium, and a couple of trace elements. The objective is to move the cow from the high-forage prepartum diet to the high-concentrate postpartum diet as quickly and smoothly as possible. In addition to its main function as an energy supplement, the concentrate mixture usually serves as a carrier of supplemental protein, minerals, and vitamins. Most trace elements function as cofactors or activators of enzymes.
