| Two experiments were conducted for this trial.First, one experiment was conducted to study the suitable combination ratio of rice straw, corn silage and alfalfa in vitro, in addition, it also study the effect of different ratios of the three roughage on the growth performance, blood indicators of cows in summer.Tral 1:this experiment was to study the effect of combination of rice straw, corn silage straw and alfalfa on the gas production and rumen fermentation parameters.A compound forage mixture (CR) is formulated by corn silage and rice straws with the ratio of 50:50 (dry matter as basis).CR was mixed with alfalfa according to the ratio of 0:100 (CR0),40:60 (CR40),75:25 (CR75) and 100:0 (CR100) to constitute roughage.Those four mixed roughage were then combined with concentrate by the proportion of 70:30 to constitute four complete diets.Ruminal fluid was obtained from Holstein cows fed twice daily on a mixed diet of alfalfa hay and mixed concentrates (7:3,w/w).Syringe system was conducted to investigate, the gas production was recorded at 2,4,6,8,12,24,36,48,72h of incubation, After 12,24,36,48h incubation the gas production mixed fermentation medium was used for analysis of ammonia nitrogen, volatile fatty acids (VFA), pH and microbial crude protein (MCP). The results showed that:1.The GP of each group at all incubation times increased with the level of alfalfa, after 24h incubation, GP of CRO,CR40 and CR75 appeared higher than CR100 (P<0.05).2.Before 12h incubation MCP concentration increased with the level of alfalfa(P <0.05),CR75 had the highestat MCP(80.39mg/dl) at 48h, and appeared higher than CR100 and CR40(P<0.05).3.As the level of alfalfa, there had different extent to enhance VFA concentration, but CR75 compared with CR40 and CRO, appeared higher concentration of TVFA, acetate and propionate(P<0.05).4.Combination of different quality roughage had a positive associative effect, furthermore, CR75 is higher than CR40 at all time points.Tral 2:To study combination of different ratios of rice straw, corn silage and alfalfa on performance of dairy cow, blood biochemical parameters and blood indexes. 15 lactating Holstein cows were divided into 3 groups(control group, experiment group CR40 and CR75).Corn silage and alfalfa in the control group for rice straw, corn silage and alfalfa in the treatment groups by equal dry matter quantity. The proportion of roughage combined with concentrate is 70:30 of each treatment,CR40 group alfalfa block:maize-rice (maize silage:rice straw=1:1)is 6:4, CR75 group alfalfa block:maize rice the ratio is 25:75.The results showed:1.The difference of milk yield and DMI in all experimental groups was not significant (P>0.05), but FCM of CR75 and CR40 appeared higher than control group(P<0.05),increased respectively 5.14% and 3.86%, and there had no significant different between CR75 and CR40(P>0.05).2.With the increasing of alfalfa, SCC in milk of each group declined, and the SCC in CR40 and C75 groups were lower than control group (P<0.05).3.Combination of different-quality roughage significantly reduced BUN of CR75 and CR40 (P<0.05), CR75 and CR40 was no significant difference between (P>0.05).4. Compared with control group, both CR75 and CR40 enhance PO2 and Ca2+ in blood (P<0.05), pH of each treatment is stable and base excess and standard bicarbonate no significant differences (P>.0.05).5.CR75 group of the highest gross profit, compared with the control group increased 0.51 yuan/head·days, compared with an increase of 2.69 yuan CR40 group/head days.These works indicate that low-quality roughage of rice straw and corn silage stalks combination with alfalfa can produce positive associative effects.In this experiment, the effect of rice straw, corn silage stalks and alfalfa silage mixed as the ratio of 3:3:2 better than the ratio of 1:1:3.In summer, rice straw, corn silage stalks and alfalfa combined as the ratio of 3:3:2 had no effect on dairy intake, but improved the FCM production and reduced SCC of cows in milk. Furthermore, it also improved health of dairy cows and reduced the cost of production.
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