| Lamb havenutritional value of high protein, low fat and low cholesterol, buthigh-quality lamb gradually become consumption concept with the improving of living standard. According to the growth rule of Tan sheep, we implemented lamb fattening by stages and feed different energy and protein levels of diet at every stage to observe fattening effect, then the dressed lamb carcass to detect the effect of the proportion of highquality cutting.To determine the appropriate level of dietary protein can provide a theoretical basis for the production of high-quality lamb meat.112 lambs(4 months old) were randomly assigned to four treatments, each treatment comprises 4 replicates including 2 male and 2 female replicates. In each replicate, 7 lambs were used. This study was performed among 3 growth periods: 22~28 kg, 29~35 kg and 36~40 kg. According to the feeding standard of meat sheep(NY/T816-2004), it was set up84%, 96%, 108% and 120% of the standard nutrition diet for each treatment and used the same energy-protein ratio at the same stage, but energy and protein level of diet was divided into 4 groups. 16 animals were slaughtered to investigate the slaughter performance and meat quality at the end of each period. The results showed that:1. After the fatting of thetrial, the final weight, dressing percentage, GR value and tail weight of Tan sheep showed the same tendency among three phases: Group I<Group II <Group III<Group IV. At the first stage, The final weight and average daily gain in Group IV were significantly higher than that in Group II(P<0.05), while no significant difference was found in group III(P>0.05).At the second stage, average daily gain in Group IV were significantly higher than that in Group I(P<0.05), while no significant difference was found in group I, II, III(P>0.05).At the third stage, average daily gain in Group IV were significantly higher than that in Group II(P<0.05), while no significant difference was found in group III(P>0.05).2. At the first stage, compared with Groups I, the dressing percentage in Group IV was increased by 10.75%(P<0.05). The lamb in Group IV belongs to medium body condition because GR value reached 12.30 millimeter, while no significant difference was found in group III(P>0.05). The tail weight in four groups was non-significant difference(P>0.05).At the second stage, the dressing percentage in Group IV which reached 54.38% was higher as compared to Group II and III decreased by 7.30%(P<0.05) and 2.95%(P>0.05). At the third stage, the lamb in Group IV belongs to fat body condition because GR value reached 18.71 millimeter, and increased by 16.87%(P<0.05) compared with Group III. In Group IV the tail weight which reached 2.23 kilogram could account for 8.92% of carcass weight, and increased by 26.01%(P<0.05) compared with Group III, while in Group III the tail weight only increased by 1.70%(P<0.05) compared with Group II.3. At the first stage, Marbling scoring and ether extract content in Group IV were significantly increased by 52.58% and 28.49%(P<0.05) compared with Group I. Meat tenderness in Group IV was significantly lower than that in other groups(P<0.05). At the second stage, Marbling scoring and ether extract content in Group IV were significantly increased by 37.50% and 21.80%(P<0.05) compared with Group II, while no significant difference was found in group III(P>0.05).At the third stage, Marbling scoring in Group III was significantly higher than that in Group II(P<0.05), while no significant difference was found in group IV(P>0.05). Water losing rate in Group III was significantly lower than that in Group I and II(P<0.05).4. At the first stage, Essential amino acid content in Group IV was significantly increased by 6.18% compared with Group I. The total amino acid content in four groups was significant difference(P<0.05). At the second stage, Essential amino acid content in Group IV was significantly lower than that in group I, II, III(P<0.05). In four groups the total amino acid content and the proportion of essential amino acids in total were significant difference(P<0.05). At the third stage, the total and essential amino acid content in four groups were significant difference(P<0.05). In Group III the proportion of essential amino acids in total was non-significant difference compared with Groups IV(P>0.05).5. With domestic and foreign carcass cutting method of lamb carcass, we proposed a set of enterprise standardfor lamb production. The method was possible to meet the aspirations of the people for high-grade lamb and reflected the value of carcass; moreover, it also changed the value of the carcass from the energy and protein levels. In 22 to 28 and 29 to 35 kilogram weight, raising the level of energy and protein diet have contributed to improve the high quality weight and the proportion of it. Therefore, feeding high energy and protein level diet is more advantageous to improve the quality of the carcass. In 36 to 40 kilogram weight, decreasing the level of energy and protein properlyis more advantageous to reduce abdominal depositional and energy waste. Therefore, feeding medium and high energy and protein levels diet is more advantageous to improve the quality of the carcass.It is concluded that Tan-sheep lamb were in these three stages: 22~28 kg, 29~35 kg, 36~40 kg, when fed the digestive energy: 12.30 MJ/kg, 10.65 MJ/kg, 9.53 MJ/kg, crude protein: 15.37%, 13.61%, 11.91%, respectively. Our results will benefit the improvement of fattening performance and meet quality in Tan sheep. |
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