Influence of level and composition of concentrate supplements on rumen fermentation patterns of grazing dairy cows.

Abstract

In a 2 x 2 Latin square design trial 6 grazing dairy cows, with rumen cannula, were supplemented with high-starch concentrate, containing starch 248 g/kg DM, or low-starch concentrate (starch 15 g/kg DM). Cows were given daily 1 kg high-starch concentrate (1HS), 7 kg high-starch concentrate (7HS) or 7 kg low-starch concentrate (7LS) in equal meals fed at 0600 and 1600 h. After 3 weeks of adaptation, rumen samples were taken at 4-h intervals in two 24-h periods. In the first 24-h period samples from the swards (80-90% Lolium perenne) were taken immediately before rumen sampling. Total sugar content of herbage increased during daytime with the highest content directly before sunset. Patterns of ruminal pH values were not different between treatment and values were minimum at 2400 h. Volatile fatty acids (VFA) and ammonia peaked at 2400 h. Extra high- or low-starch concentrate decreased ruminal content of ammonia 19, 13 and 12 mmol/litre for treatments 1HS, 7HS and 7LS and also decreased branched-chain VFA. Acetate:propionate and non-glucogenic:glucogenic ratios within VFA and percentage of milk fat were lowest for treatment 7HS. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Milk production and <i>in sacco</i> disappearance of pasture NDF in grazing Jersey cows receiving a barley based concentrate

“…This was due to an increase in acetate and iso-valerate concentrations. Some of the publications reviewed by Bargo et al (2002) supported the fact that supplementation is associated with an increase in total VFA concentrations, yet the majority (Van Vuuren et al, 1986;Sayers, 1999;Reis & Combs, 2000) reported no effect of supplementation on total VFA concentrations even with reductions in pH . and Casper et al (1999) reported that supplementation consistently reduced ruminal NH 3 -N concentrations and that this could be associated with a higher capture of NH 3 from the highly degradable pasture CP.…”

Efectos del momento de asignación diaria de la pastura y del ayuno sobre el comportamiento ingestivo y la productividad de vaquillonas de biotipo carnicero

“…Los procesos metabólicos que ocurren en la planta entre la mañana y el atardecer involucran principalmente una pérdida de agua y una ganancia de fotosintatos (Delagarde et al, 2000). La pérdida de agua durante las horas de luz resulta de una disminución de agua superficial por evaporación y de una pérdida de agua interna debido al balance negativo entre la absorción y la transpiración, que juntamente con la síntesis de carbohidratos determina un incremento en el contenido de MS del forraje (Van Vuuren et al, 1986). La variación en la concentración de MS en el forraje durante el día oscila entre 3.5 y 6 puntos porcentuales dependiendo, entre otros factores, de la estación del año.…”

“…La variación en el porcentaje de PB durante el día es de menor magnitud que la variación en la concentración de CNES (Van Vuuren et al, 1986). Delagarde et al (2000) observaron diferencias significativas de 1.1 unidades porcentuales entre la concentración de PB de la mañana (17.7%) y la tarde (16.6%), lo que representa una disminución del 6.2%.…”

Effects of delayed fat supplementation on post-prandial rumen metabolism, lamb quality and fatty acid composition of rumen effluent

“…The successfulness of these feeding strategies might be affected by diurnal rumen metabolism. Diurnal changes in grazing activity of ruminants in response to environmental temperatures, demand for other activities such as rumination and resting (Rook et al, 1994), diurnal changes in nutrient composition of pasture (Orr et al, 1997) and rumen metabolites (Van Vuuren et al, 1986) can affect diurnal changes in rumen metabolism.…”