The effect of frequency of feeding and supplementation with sucrose on ruminal fermentation of alfalfa silage given ad libitum or restricted to sheep

Abstract

Eight ruminally cannulated wethers were used in a factorial trial to examine the effect of frequency of feeding alfalfa silage and sucrose supplementation on voluntary intake, digestibility, rumen fermentation and rate and extent of digestion in and passage from the rumen. When diets were fed ad libitum, frequency of feeding had no effect on voluntary intake, apparent digestibility or the postfeeding concentrations of rumen ammonia N, volatile fatty acids (VFA) and pH. Similarly, VFA ratios and fluid kinetics in the rumen were unaffected. Supplementation with sucrose reduced ruminal concentrations of ammonia N at the higher level of feeding but failed to influence any other measured parameters. When intake was restricted (18 g DM kg⁻¹ body weight), increased feeding frequency reduced the post-feeding ruminal ammonia peak and reduced the post-feeding decline in pH; however, sucrose supplementation had no effect. Kinetics of the liquid phase in the rumen, particulate rate of passage and rate of digestion were not affected by feeding frequency or sucrose supplementation. It was concluded that effects observed at a restricted feeding level may not be apparent when feed is available ad libitum and vice versa. Key words: Sucrose, feeding frequency, alfalfa, silage, sheep