Response of Dietary Restriction of Oat Hay on Ruminal Fermentation Parameters of Tibetan Sheep and Estimation of Maintenance Requirement of Nitrogen
The objective of this study was to evaluate the effects of dietary restriction of oat hay on ruminal fer-mentation parameters of Tibetan sheep, and to estimate maintenance requirement of nitrogen.Five 20-month-old castrated male Tibetan sheep with similar body weight [ ( 45 ±2 ) kg] were selected in a feeding trial and a fasting metabolism trial.Five sheep were randomly divided into four groups ( two sheep in one of the groups as replicate) in the feeding trial using a 4 ×4 Latin square design.Four dietary restriction levels were set, which were 90%, 70%, 50 and 30%of voluntary intake, respectively.Feces, urine and rumen fluid (after 0, 2,4, 6 and 8 hours of feeding) were collected to measure the indices of digestion and metabolism of nutrients and rumen fermentation metabolic parameters.Feces and urine were collected to measure daily output of fecal and urinary nitrogen in the fasting metabolism trial.The results showed as follows:1 ) dietary restriction level had no significant effects on rumen fluid pH, the contents of acetate, propionate, isobutyrate, valerate and isovalerate, and acetate/propionate (P>0.050), but had significant effects on butyrate content and total vola-tile fatty acid concentration ( P<0 .050 or P<0 .001 ) .2 ) Dietary restriction level had no significant effects on the digestibility of dry matter ( DM) , organic matter ( OM) , crude protein ( CP) , neutral detergent fiber (NDF) and acid detergent fiber (ADF) (P>0.050).3) With the increase of fasting time, fecal nitrogen showed a tendency of being firstly decreased and then balanced, and urinary nitrogen and total nitrogen output both showed a tendency of being firstly decreased and then balanced.In conclusion, dietary restoration level does not affect nutrient digestibility of Tibetan sheep.Nitrogen maintenance requirement during regular feeding period is 0.12 g/(kg BW0.75· d), and that during fasting period is 0.15 g/(kg BW0.75· d).
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维普
