Nutrients, digestion and absorption: Fiber digestion in pasture-based cows

Abstract

There is a growing interest in pasture-based dairying internationally, and contemporary pasture systems in industrialized countries are increasingly characterized by higher quality pastures, higher dry matter intakes, and higher milk yields. These changes bring new challenges to the nutrition of pasture-based cows. The role of dietary fiber in pasture-based cows has traditionally been defined from the body of research investigating rumen function and animal responses to fiber in total mixed ration systems. However, this research is, in many important respects, highly specific to total mixed ration systems and there are notable difficulties in extrapolating the methods of fiber assessment and the practical conclusions generated to pasture-based systems. This is supported by the limited research available in the field, which also suggests that the responses to supplementary fiber are markedly different and less advantageous in pasture-based cows when compared with cows fed total mixed rations. In particular, supplementary fiber does not appear to be as effective in eliciting additional chewing responses in the pasture-based cow, suggesting that fiber may not be as dominant an influence in altering rumen function compared with cows fed total mixed rations. Further specific research into fiber nutrition in pasture-based systems is required to better understand both the synchronies and limitations of the existing body of research in guiding nutrition in grazing cows.