Effect of Different Alfalfa and Rice Straw Proportion on Associative Effects of Sheep's Diets

This experiment was conducted to investigate the effects of the proportion of alfalfa and rice straw on associative effects (AE) of diets in vitro. Rice straw:alfalfa were 60:0, 50:10, 40:20, 30:30, 20:40,10:50,0:60 when concentrate-roughage ratio (C:R) was 40:60, and rice straw:alfalfa were 70:0, 60:10,50:20, 40:30,30:40,20:50,10:60,0:70 when C:R was 30:70. Gas production (GP) was recorded at 2, 4, 6, 9, 12, 24, 36, 48, 72 and 96 h. The AE was defined as the difference between the observed in vitro GP_{24 h} and the predicted value from individual feed fermented alone. The results showed as follows:① GP_{24 h} of the group 50:10 was extremely significantly greater than the group 10:50 (P<0.01), and GP_{24 h} of the groups 40:20 and 60:0 were significantly greater than the groups 10:50 (P<0.05) when C:R was 40:60. The AE of all groups were positive and there were no significant difference among them (P>0.05). When C:R was 40:60, the GP_{24 h},b,a+b of group 50:10 were the greatest and it's AE was the best.②GP_{24 h} of the groups 60:10, 70:0 and 50:20 were significantly greater than the group of 0:70 (P<0.05) and groups 40:30 and 20:50 were greater than the group 0:70 (P=0.063, P=0.064) when C:R was 30:70. The AE of all groups had no significant difference (P>0.05). When C:R was 30:70, the GP_{24 h},b,a+b of group 40:30 was the greatest and it's AE was the best, followed by the groups 20:50 and 10:60. It is concluded that the AE of the groups of 50:10 (C:R was 40:60), 40:30, 20:50 and 10:60 (C:R was 30:70) were greater.