| This experiment was devoted to study the effect of rumen-protected lysine (RPLys) conjugated linoleic acid (CLA) and N-carbamyl glutamic acid (NCG) on production performance, meat quality, digestion and metabolism and blood biochemical index in Stabling Tan Sheep by feeding trial, slaughter experiment, digestion and metabolism experiment,aimed to selecting an optimal additive that could improved both production performance and meat quality.The experiment was dividesd into four parts:Experiment 1:The effect of different additives on production performance in Stabling Tan Sheep32 Tan sheeps with healthy and weight similarity were chosen and divided into 4 groups randomly. Each group had 8 sheeps (3 rams and 5 ewes). The control group was fed basal dietGroup I was fed basal diet and 8g/d RPLys. Group Ⅱ was fed basal diet and 2%CLA. Group III was fed basal diet and 0.2%NCG. In the whole testing period (60d), each group of the body weight and body size index was measured at the beginning and the end of experiment, while recording the daily feed intake. The results showed that:there were no significant difference among RPLys (group I), CLA (group II) and NCG (groupⅢ) at the body height, body length and confining growth of Stabling Tan Sheep (P> 0.05). RPLys and CLA could significantly improve bust growth with rams (P<0.05), while highly significant improved bust growth with ewes (P<0.01). The average dry matter intake of group Ⅱ was 900.48 g/d, that was the highest in the whole testing period and followed by group Ⅰ.Then the control group was the lowest. Except average daily gain of group II was significantly improved (P<0.05), group I and groupⅢ had no effect on average daily gain (P>0.05)Experiment 2:The effect of different additives on meat quality in Stabling Tan SheepAfter feeding trial,3 rams in each group were selected and proceeded slaughter experiment with meat quality analysis above the condition of diet. The results showed that:there was no significantly effect in dressing percentage, carcass meat rate and meat-bone ratio by using RPLys, CLA, NCG, but it changed the body muscle and fat ratio. Comparing with the control group, groupⅡ could highly significantly improved the carcass lean meat (P<0.01), also groupⅢ could significantly improve that (P< 0.05), but there was a tendency to reduce in group I. Eaech goup had no significantly effect in eye muscle area, GR values, muscle pH, water loss rate, rate of cooked meat, marbling score and conventional index for meat. Meanwhile, compard with group I, the back fat thickness of group II was significantly below (P> 0.05); b* values and L* value of fleshcolor among different treatment groups had no significant difference (P> 0.05), but CLA could significantly improve the a* values of meat color (P< 0.05), while NCG had a tendency to increase (P> 0.05). Group II was highest in intramuscular fat content, significantly higher than control group and group I (P< 0.05), groupⅢ was significantly higher than group I (P<0.05). Utilizing headspace solid phase microextraction (HS-SPME) and gas chromatography-mass (GC-MS), the control group, group Ⅰ, group Ⅱ and group Ⅲ had respectively identified 55,64,66 and 66 kinds of volatile flavour compounds. In this test, there were 26 kinds of same volatile flavour compounds for the treatment group, including hexanal relative content in group I and group III were higher than control group, that wasn’t conducive to improve the meat quality. The hexanal relative content of group II was 1.201%, lower than the control group. Therefore, in the certain extent CLA can reduce the bad flavor substance.Experiment 3:The effect of different additives on digestion and metabolism in Stabling Tan Sheep3 rams in each group were selected and adopted single tie-down breeding, then carried on digestion and metabolism experiment and measured the apparent digestibility and the nitrogen metabolism nutrient of the feed rate after collecting feces, urine and remaining feed. The results showed that:the group II highly significantly increased crude fat apparent digestibility (P< 0.01), and highly significantly reduced the apparent digestibility of the neutral detergent fiber and acid detergent (P<0.01), group I and group Ⅲ had no significantly effect apparent digestibility of each feed nutrients (P> 0.05); the three additive groups had improved nitrogen apparent metabolic rate in a certain extent.Nitrogen apparent metabolic rate of Group I was significantly higher than control group (P< 0.01), group II and group Ⅲ were significantly higher than the control group (P> 0.05).Experiment 4:The effect of different additives on blood biochemical index in Stabling Tan SheepAt the same diet condition with experiment 1, the blood of each goup were collected at the beginng of experiment in Od,15d,30d,45d and 60d. Then taken serum and measured the blood biochemical index after standing. The results showed that:there were no significant effect in serum total protein content and serum triglyceride content after using RPLys, CLA and NCG (P> 0.05). But, in the late test, the blood sugar levels of group I had significant risen (P> 0.05).Serum total cholesterol of group II decreased with continuous feeding time, and to maintain relatively stable blood sugar levels.In summary, the CLA had double effects on improving production performance and meat quality in Tan Sheep. It was the the optimal additive for efficient breeding and production of high-grade mutton. |
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