Invited Review: Current areas of research of feeding practices for lactating goats1

Dietary concentrate level, forage quality, and production system can have a great effect on tissue loss and gain by lactating goats in addition to milk yield and composition. Opportunities for enhanced performance with high concentrate levels are greater in early than late lactation, with high milk production potential, although there might be an advantage in efficiency of energy use in late lactation when tissue is often replenished. Effects of by-product and alternative feedstuffs on conditions such as ruminal methane emission, milk fat content and fatty acid (FA) composition, and antioxidant status depend on major and minor constituents and what they are substituted for. Research on minor dietary ingredients such as probiotics and plant secondary metabolites is likely to increase with decreased use of synthetic antimicrobials, although specific components responsible for effects are sometimes unclear. In addition to the FA profile of feedstuffs, conditions including dietary concentrate level, supplemental FA sources, and levels of plant secondary metabolites can influence bioactive ruminal biohydrogenation intermediates that decrease de novo FA synthesis in the mammary gland. Supplementation with sources of conjugated linoleic acid has been studied, but use is not common, probably because of less change in milk fat content and FA composition compared with cattle, different considerations regarding tissue mobilization in early lactation with appropriate feeding management practices, and limited or no benefit from low-fat milk. However, inclusion of moderate dietary levels of oils and other fat sources for purposes such as increased energy density, improved palatability, and decreased dustiness is widespread.