Duration of regrowth of ryegrass (Lolium perenne) effects on grazing behavior, intake, rumen fill, and fermentation of lactating dairy cows

Citation
P. Chilibroste et al., Duration of regrowth of ryegrass (Lolium perenne) effects on grazing behavior, intake, rumen fill, and fermentation of lactating dairy cows, J DAIRY SCI, 83(5), 2000, pp. 984-995
Citations number
41
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Food Science/Nutrition
Journal title
JOURNAL OF DAIRY SCIENCE
ISSN journal
0022-0302 → ACNP
Volume
83
Issue
5
Year of publication
2000
Pages
984 - 995
Database
ISI
SICI code
0022-0302(200005)83:5<984:DOROR(>2.0.ZU;2-H
Abstract
The relative importance of duration of sward regrowth and fill and fermenta tion in the rumen on the control of grazing time and intake rate during the first grazing session of the day was studied. Four lactating dairy cows we re allowed to graze ryegrass (Lolium perenne) swards, with five different r egrowth periods after mowing (6, 9, 16, 22, and 30 d). The cows were allowe d to graze until they stopped voluntarily (cessation of grazing activity fo r at least 15 min). Before and after grazing the rumen contents were evacua ted, weighed, sampled, and returned to the animals. Samples of rumen liquid were taken immediately before rumen evacuation and approximately 30, 60, 1 20, and 240 min after the grazing session was finished. Grazing time and in take rate did not follow a significant trend with period of regrowth. Bite rate did not change significantly with duration of regrowth with cows exhib iting high rates of biting for all the sward conditions. Rumen pools sizes of dry matter, neutral detergent fiber, and volatile fatty acids (VFA), mea sured after grazing, increased significantly with days of sward regrowth, e ven though the changes over days were small. Concentration of VFA followed a significant quadratic trend with a maximum concentration observed at appr oximately 110 min after cessation of grazing. In this study, rumen fill, VF A (either total or major components), ammonia, pH, and osmotic pressure as individual variables were not correlated with grazing time or dry matter in take.