Frequency of concentrate supplementation for cattle fed barley straw. 2. Ruminal dilution rates, pH and metabolite concentrations

Abstract

[467][468][469][470][471][472][473][474][475][476][477][478][479]. Five ruminally cannulated crossbred steers (474 ± 30 kg) were fed diets containing 70% barley straw and 30% concentrate in an unbalanced 5 × 5 Latin square design experiment to investigate the effects of frequency of feeding concentrate (daily, alternate days or every third day) with different dietary protein concentrations (7.9 and 11.5%) on ruminal liquid and particulate dilution rates, pH and metabolite concentrations. Dilution rates of cobalt-ethylene diamine tetraacetic acid (Co-EDTA) and chromium-mordanted fibre did not differ when low-and high-protein concentrates were fed. Supplemental protein increased (P < 0.05) mean ruminal ammonia concentrations (3.3 vs. 1.6 mM), but had no influence on ruminal concentrations of organic acids. Frequency of concentrate feeding had no influence on dilution rate of digesta markers, pH or on mean ruminal concentrations of ammonia, lactic acid, propionic acid, isobutyric acid, valeric acid and isovaleric acid. Mean concentrations of total volatile fatty acids, acetic acid and butyric acid were, however, reduced (P < 0.05) when steers were fed concentrates on alternate days. The reduced (P < 0.01) ruminal acetic:propionic acid ratios observed in steers fed concentrates on alternate days were consistent with reduced heat productions. Positive relationships (P < 0.05) were obtained between heat production of steers and ruminal concentrations of isobutyric and valeric acids. It was concluded that the low-protein diet did not provide sufficient protein to meet microbial requirements and that under controlled feeding conditions cattle can be fed concentrate on alternate days or every third day without the occurrence of lactic acidosis. Additional research is warranted to examine the relationships between reduced heat production of steers fed concentrates on alternate days and ruminal concentration and production of organic acids. expérience en carré latin 5 × 5 non équilibré qui devait préciser les effets de la fréquence à laquelle un concentré à teneur variable en protéines (7,9 et 11,5 %) était servi (tous les jours, un jour sur deux ou aux trois jours) sur les fluides, le taux de dilution des particules, le pH et la concentration des métabolites dans le rumen. Le taux de dilution du cobalt-EDTA et des fibres mordancées au chrome ne varie pas avec la teneur en protéines du concentré. Le supplément protéique accroît (P < 0,05) la concentration moyenne d'ammoniaque dans le rumen (3,3 c. 1,6 mM), mais n'influe pas sur la concentration des acides organiques. La fréquence à laquelle on sert le concentré n'agit pas sur le taux de dilution des marqueurs des digest, sur le pH ni sur la concentration moyenne d'ammoniaque, d'acide lactique, d'acide propionique, d'acide isobutyrique, d'acide valérique et d'acide isovalérique dans le rumen. Toutefois, on remarque une baisse (P < 0,05) de la concentration moyenne des acides gras volatils, de l'acide acétique et de l'acide butyrique quand on donne le concentré aux bouvillo...

Frequency of concentrate supplementation for cattle fed barley straw. 1. Effect on voluntary intake, ruminal straw disappearance, apparent digestibility and heat production

“…Frequency of feeding concentrate had no influence on the digestibility of DM, NDF, ADF, and energy (Table 4), a result which may be explained by ruminal ammonia concentrations (Tellier et al 2004). This result is similar to that obtained by Coleman and Wyatt (1982) and Collins and Pritchard (1992).…”

“…In this study, however, protein supplementation did not increase voluntary intake of straw. This was surprising since the intake of rumen degradable protein was below requirements (Tellier et al 2004) and rate of disappearance of straw in the rumen 1.14 0.24 0.04 z Range in gross energy digestibilities for straw in all diets, low-protein diets and high-protein diets were 29 to 59, 29 to 47 and 35 to 59%, respectively. Corresponding ranges in digestible energy contents were 5.3 to 10.9, 5.3 to 8.8 and 6.4 to 10.9 MJ kg -1 .…”

“…It was concluded that concentrate can be fed every second day without any negative impact on intake and digestibility, with a possible benefit of a reduction in energy lost as heat. More research, however, is required to study the feasibility of feeding concentrate every third day.Key words: Cattle, straw, protein, feeding frequency, digestion, heat production Tellier, R. C., Mathison, G. W., Okine, E. K., McCartney, D. et Soofi-Siawash, R. 2004. Fréquence des apports de concentré pour les bovins nourris de paille d'orge.…”

“…Key words: Cattle, straw, protein, feeding frequency, digestion, heat production Tellier, R. C., Mathison, G. W., Okine, E. K., McCartney, D. et Soofi-Siawash, R. 2004. Fréquence des apports de concentré pour les bovins nourris de paille d'orge.…”

“…Additional information concerning liquid and particulate dilution rates in the rumen and ruminal metabolites was also obtained (Tellier et al 2004). …”