Effects Of Different Proportion Of Sorghum Grain Diets On Performance And Digestive Metabolism Lamb Production

This thesis aims to study the effect of substitution of maize with different proportions sorghum in diets on growth performance, digestion and metabolism of lambs. Five experiments were included in the thesis.Experiment2.1, The influence of substitution of maize with different proportions sorghum in diets on growth and feed intake of sheep. Twenty-four male German merino weaned lambs (16.19±2.05kg BW) were randomly divided into four treatments using a completely randomized design. The diets for four treatments contained450g/kg of corn (group A), sorghum (containing1.15%tannin)(group D), or2:1(group B) and1:2(group C) mix of corn and sorghum respectively. The whole experiment included10days of adaptation period and57days of formal feeding experiment. Diets offered and refused were recorded daily. Lambs weight was recorded at the formal start and every two weeks before the8:00a.m. The results showed that average daily weight gain and total gain significantly increased (P<0.05) in D group than that of group A, but no significant difference was found with group B and D. This means that maize as energy feed can completely or partly replace with sorghum corn in the diet of lambs.Experiment2.2, The influence of substitution of maize with different proportions sorghum in diets on rumen fermentation. Rumen fluid was collected by negative pressure method from mouth on8:00,10:00,12:00,14:00in the end of growth experiment. The results showed that (1) there was no significant difference was found for PH of A, B, C and D group;(2) The highest concentrations of acetic acid, propionic acid and total VFA was found for group C, the lowest was group D, but no significant difference was found among four treatments;(3)A group had the lowest Butyric acid concentration, C group was the highest, no significant differences existed between any treatment.(4)The average concentration of ammonia nitrogen in group C was significantly higher than that of group B (P<0.05), but no significant difference with group A and D. This result indicate that no negatively effect on rumen fermentation when substitution of maize with different proportions sorghum in diets, however, two thirds of maize replaced with sorghum had a tendency to promote the rumen fermentation.Experiment2.3, The influence of substitution of maize with different proportions sorghum in diets on nutrients apparent digestibility and the nitrogen utilization. Each lamb was assigned to an individual metabolic cage. The metabolism experiment was conducted during the feeding experiment, feces and urine were collected for5consecutive days. The results showed that the apparent digestibility of dry matter in group B was significantly (P<0.05) higher than that of group D, the apparent digestibility of crude protein in A and B groups significantly was (P<0.05) higher than that of group C and D. There was no significant difference for nitrogen utilization among the four experimental groups. This result indicats that sorghum as energy feed has some negative impacts on digestibility of nitrogen when two-thirds and all maize were replaced with sorghum.Experiment2.4, The influence of substitution of maize with different proportions sorghum in diets on biochemical indicators and hormones in the blood. The results indicated that no significant effect was found for four groups’blood biochemical index and hormone level. The activity of SOD of group was significantly (P<0.05) higher than the other three groups. This result indicats sorghum, as energy feed, has no negative effect on blood biochemical indexes and hormones.Experiment2.5, The influence of substitution of maize with different proportions sorghum in diets on mutton quality, meat color and lipid peroxidation during storage. The result indicated that the carcass weight of group B and group D were significantly (P<0.05) higher than that of group A after24hours slaughter, the pH24in C and D group significantly (P<0.05) lower than that of group A. there was a positive effect on stability of meat color in D group based on the changing trend of meat color during120hours storage, the TBARS value in D group was also lowed than other group. This results show that sorghum can stabilize meat color and delay lipid oxidation.In conclusion, Different proportions of sorghum instead of corn in lamb diets have the positive effect on the daily gain and feed efficiency, best performance was found for group D when sorghum entirely replacing maize, and the sorghum partially or completely replacing maize can stabilize meat color and delay lipid oxidation during storage. The disadvantage aspect is that sorghum instead of maize decreased the apparent digestibility of nitrogen of the lamb, but because of sorghum containing higher percentage of crude protein than maize, the final result is that no significant effect was found for nitrogen utilization. Hence, this experiment showed that the sorghum instead of maize plays a positive role on the lamb growth, its internal mechanism needs further discussion.