| The objective of this study was to explore the effect of restricting feed intake for 30 days and subsequent compensatory growth for 60 days of Small Tail Han sheep rams on their productivity and metabolism. Forty 3-month age sheep with mean body weight of 19.77±1.34 kg were randomly split into four groups, the control group with feed ad libitum, and the other three treatment groups with different ME and CP diet levels according to different average daily gain (ADG) 500 g/d,400 g/d,300 g/d by NRC (2007). After 30-day feed restriction phase, the 60-day realimentation phase was started with feed ad libitum for all the experimental sheep. The results showed:1) In the feed restriction phase, the nutrient intake decreased with the increase of feed restriction level. As a result, the ADG was significantly decreased (P<0.05), and feed conversion ra|e was also reduced with the increase of feed restricting level. The ADG and feed conversion rate in the realimentation phase was contrary to the restriction phase. Analysis of the compensation index showed that all of the experimental groups presented compensation rates between 99.6% and 104.4%. Significant differences (P<0.05) among different restriction levels were observed.2) The control (I) group had similar body weights with treatment II during the end of feed restricted period (P>0.05). And both were higher than treatment IV (P<0.05). The bodyweight of III group was only lower than the control group (P<0.05). The apparent digestibility of DM, NDF, ADF decreased with the increase of feed restriction level during the end of feed restriction period. No significant differences were found for OM and CP digestibility (P>0.05). However, during the end of the realimentation period, the apparent digestibility of all nutrients and bodyweights showed no differences among the four groups (P>0.05).3) The nitrogen intake, nitrogen retention, nitrogen retention decreased with the increase of feed restriction level for the treatment groups during the end of the feed-restriction period (P<0.05). However, the ratio of urine nitrogen to nitrogen intake increased with the increase of feed restriction level (P<0.05). No significant differences of fecal and urine nitrogen among the four groups were found during this period (P>0.05). During the end of the realimentation period, there were no significant differences of the nitrogen balance variables among the four groups (P<0.05). Therefore, the present results indicated that short-term moderate feed restriction, and then with a feed realimentation period is not harmful for the growth performance, digestion and metabolism of small Tail Han sheep.4) The rumen pH value, and concentration of propionic acid and butyric acid concentration showed no significant difference at the end of feed restriction period (P>0.05), the control group was significantly higher than the other groups on the ruminal acetate concentration at the end of feed restriction phase (P<0.05). There was no significant difference on rumen pH, the concentration of acetic acid, propionic acid, and butyric acid concentration at the end of realimentation phase (P>0.05).5) There were no significant difference on Plasma insulin,3.5.3-triiodothyronine (T3), thyroxine (T4), non esterified fatty acid (NEFA) and growth hormone concentration through the whole experimental period (P>0.05). There were difference on growth hormone (GH), but did not reach significant level (0.05≤P<0.1)in different dietary restriction levels. The insulin-like growth factor-1(IGF-1) concentration were significantly higher in Ⅱ and Ⅲ groups than IV group (P<0.05). There were no significant differences among the other indicators, such as glucose (GLU), beta hydroxy butyric acid (β-HB), cortisol (COR). |
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