Modelling of Herbage Intake and Milk Production by Grazing Dairy Cows

Key-points Models predicting intake and performance of grazing ruminants from animal, sward, grazing and supplements characteristics are rare, but they are now included in several decision support systems (DSS). An evaluation of the performance and accuracy of published models are rarely undertaken by their authors, but this is proposed in this paper. There is still a need for experimental research but also for the development of generic and dynamic models to predict intake and performance over a wide range of grazing conditions

Foraging behavior and ruminal fermentation of dairy cows grazing ryegrass pasture alone or with white clover

The objective of this work was to evaluate the influence of pasture composition and regrowth age on the relationship between feeding behavior and ruminal fermentation in dairy cows grazing perennial ryegrass with or without white clover. The experiment was carried out in a 2x2 factorial arrangement, with two sward types and two ages of regrowth. Swards of perennial ryegrass sown alone (PRG) and of perennial ryegrass mixed with white clover (GC) were evaluated. Twelve late‑lactation Holstein cows, fistulated at the rumen, were distributed in a 4x4 latin square experimental design with four 12‑day periods. Daily distribution of grazing was similar in the PRG and the GC swards, but the concentration of rumen volatile fatty acids (VFA) was higher and the proportion of propionate was lower on mixed swards during the day. Daily distributionof grazing was similar in pastures of different ages. However, in the oldest swards, rumen fluid pH increasedand VFA concentration decreased after evening milking. Time spent grazing does not influence ruminalfermentation, which depends on the changes that occur as different sward layers are grazed.The objective of this work was to evaluate the influence of pasture composition and regrowth age on the relationship between feeding behavior and ruminal fermentation in dairy cows grazing perennial ryegrass with or without white clover. The experiment was carried out in a 2x2 factorial arrangement, with two sward types and two ages of regrowth. Swards of perennial ryegrass sown alone (PRG) and of perennial ryegrass mixed with white clover (GC) were evaluated. Twelve late‑lactation Holstein cows, fistulated at the rumen, were distributed in a 4x4 latin square experimental design with four 12‑day periods. Daily distribution of grazing was similar in the PRG and the GC swards, but the concentration of rumen volatile fatty acids (VFA) was higher and the proportion of propionate was lower on mixed swards during the day. Daily distribution of grazing was similar in pastures of different ages. However, in the oldest swards, rumen fluid pH increased and VFA concentration decreased after evening milking. Time spent grazing does not influence ruminal fermentation, which depends on the changes that occur as different sward layers are grazed. azevém perene consorciado com trevo branco (TB) – e duas  idades de rebrota. A distribuição diária do pastejo foi semelhante nos pastos AZ e TB, mas a concentração ruminal de ácidos graxos voláteis (AGV) foi maior e a proporção de propionato foi menor nos pastos em associação, ao longo do dia. A distribuição das atividades de pastejo foi semelhante nos pastos com idades diferentes. Entretanto, nos pastos mais velhos, o pH ruminal aumentou e a concentração de AGV diminuiu após a ordenha da tarde. O tempo de pastejo tem pouca influência sobre a fermentação ruminal, a qual depende de alterações que ocorrem à medida que os diferentes estratos são pastejados

Forage Intake and Nitrogen Retention in Wethers Fed Ryegrass Haylage Supplemented with Maize Silage

Many decision support tools have been developed to predict herbage intake with herbivore ruminants indoors (Faverdin 1992) or at grazing, both using short-term (Baumont et al. 2004) or daily scale input variables (Heard et al. 2004; Delagarde et al. 2011). However, the ingestive and digestive interactions when diets with more than one type of forage are used have not been sufficiently studied. The aim of this study was to assess the effects of maize silage supplementation to wethers receiving ryegrass haylage on OM intake, OM digestibility, microbial protein synthesis and N retention