Effects of total mixed rations with different concentration-roughage ratios on meat quality, serum indices, and intestinal tract development in Hu sheep

Forty healthy Hu lambs with similar body weights and in good body condition were chosen in order to study the effects of different concentration-roughage ratios with equal protein to energy ratios on meat quality, serum indices, and intestinal tract development. Lambs were randomly divided into four groups with 10 sheep per group (5 male and 5 female). Sheep in each group were fed total mixed rations with concentration-roughage ratios of 70∶30 (Group Ⅰ), 60∶40 (Group Ⅱ), 50∶50 (Group Ⅲ), or 40∶60 (Group Ⅳ). The experimental period was 70 days, and consisted of a 14-day pre-experiment and a 56-day experiment. The results were as follows: 1) The serum urea nitrogen content was significantly higher in group Ⅳ lambs than in group Ⅰ lambs (P < 0.05), whereas urea glucose content was significantly lower in group Ⅳ lambs than in group Ⅲ lambs on day 14 of the experiment (P < 0.05). Serum urea nitrogen and serum total cholesterol content were significantly higher in group Ⅳ lambs than in group Ⅲ lambs (P < 0.01 or P < 0.05) on day 35 of the experiment (P < 0.05). The serum urea nitrogen content was significantly higher in group Ⅳ lambs than in lambs from groups Ⅰ and Ⅱ (P < 0.01 or P < 0.05) on day 56 of the experiment, but glucose content showed the opposite pattern. 2) Cooked meat percentage was significantly higher in group Ⅰ lambs than in group Ⅲ lambs, whereas shear force and rate of water loss were higher in group Ⅲ lambs than in group Ⅰ lambs. The percentage of crude fat in the leg muscles of group Ⅰlambs was significantly higher than in group Ⅳ lambs, whereas the meat of group Ⅰ lambs was less yellow than the meat of group Ⅳ lambs. 3) The villus height and the VH/CD of the duodenum were significantly higher in group Ⅳ lambs than in lambs from groups Ⅰ and Ⅲ (P < 0.01). The villus and the cryptic height of the jejunum were significantly higher in group Ⅲ lambs than in group Ⅰ lambs (P < 0.05). The VH/CD of the jejunum was significantly higher in group Ⅳ lambs than in group Ⅰ lambs (P < 0.05). In conclusion, meat quality could be improved by increasing the concentration-roughage ratio of diets with equal protein to energy ratios. However, higher concentration-roughage ratios were detrimental to intestinal development. The total mixed ration with a concentration-roughage ratio of 60∶40 produces the optimal results in this experiment.