The effects of forage supplementation on grazing dairy cows

This thesis first presents a review of the literature on intake from grazed herbage. It reviews animal factors and how theoretical ruminant intake concepts could be used in the grazing situation. The effects of sward conditions on herbage intake and various supplementation strategies and supplementation practices are evaluated. After which the various possible measurement techniques for estimating herbage intake are discussed. A number of experiments are presented, all carried out at the Scottish Agricultural College, Crichton Royal Farm. In the first experiment the n-alkane technique for estimating herbage intake and diet selection in dairy cows offered perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) herbage was evaluated. In a second experiment, the potential use of n-alkanes was evaluated for estimating supplementary grass silage intake. In the first supplementation experiment, two forage supplementation systems were examined over a 15 week period, using a continuous design. Thereafter two experiments are described investigating the effect of ME-content and degradability of the forage supplement on animal performance and total dry matter intake. In these two experiments two groups of grazing lactating dairy cows were offered straw/sugar beet pulp mixtures of different straw and sugar beet pulp content. The final experiment investigated the effect of forage supplement dry matter content and stage of lactation on dairy cow performance and herbage intake response. The different types of supplements did not significantly affect animal performance. The yield of fat and protein corrected milk (FPCM) was significantly (P<0.01) affected by stage of lactation. Forage supplementation resulted in a negative milk production response in late lactation cows and in a positive milk production response in early lactation. However, this response was not significantly different. The increase in FPCM with supplementation was significantly (P