Abstract
Three experiments were conducted to determine the effects of non-ionic surfactant (NIS) supplementation on ruminal fermentation, nutrient digestibility and performance of beef steers fed high-roughage diets. The objective of experiment 1 was to investigate the effects of NIS supplementation on in vitro ruminal fermentation of cultures administered with corn and barley as grain substrate and rice straw and timothy hay as roughage substrate. The in vivo ruminal fermentation, nitrogen balance and digestibility of nutrients were also examined with steers fed a high-roughage diet in experiment 2. The aim of experiment 3 was to determine the responses to NIS of growing steers fed a high-roughage diet. In experiment 1, ammonia nitrogen concentration for NIS supplementation was higher (p<0.05) than for the control with all substrates. However, concentrations of total volatile fatty acid (VFA), acetate, butyrate and valerate of the incubated roughage substrates, rice straw and timothy hay, were higher (p<0.05) for NIS supplementation than for the control whereas VFA concentrations in the cultures of corn and barley were unaffected. These results indicated that effects of NIS on ruminal fermentation are diet dependent, specifically on roughage sources. In experiment 2, ruminal pH of steers supplemented with NIS was lower (p<0.05) than the control. Ruminal concentrations of ammonia nitrogen, acetate, total VFA and urinary concentrations of purine derivatives were increased (p<0.05) by NIS supplementation. In experiment 3, supplementation of NIS increased (p<0.05) intakes of total feed and corn silage, average daily gain, and feed efficiency of growing steers although they varied depending on supplementation level. Due to the roughage-specific feature of NIS effects, NIS appears to enhance ruminal fermentation of fibrous parts of feeds and, consequently, performance of steers fed a high-roughage diet.
Highlights
Roughage sources, such as silage, hay or straw, are fermented in the rumen at a slow rate thereby limiting the efficient use of roughage sources
Valerate was influenced by non-ionic surfactant (NIS) supplementation in the cultures with roughage sources
This result indicates more observations measured within 8 h after feeding were greater extensive fermentation in the cultures grown with a roughage source, which is substantiated by a higher ammonia N concentration in cultures
Summary
Roughage sources, such as silage, hay or straw, are fermented in the rumen at a slow rate thereby limiting the efficient use of roughage sources. Wang et al (2003b) reported that effects of NIS on in vitro volatile fatty acid (VFA) production and gas production were dependent upon the silage type (alfalfa, corn and orchardgrass). On this basis, Wang et al (2003b) suggested that the response of ruminal fermentation to NIS might be diet dependent. The effects of NIS on performance of growing beef steers fed high roughage diets, have not been investigated
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