| This paper studied the effect of grazing on milk performance of dairycow and further discuss the substitution rate of the herbage as well as the optimumgrazing periods under the condition of traditional feeding dairy cows model in Henanprovince.1.The effect of grazing on body weigh gain and productive performance for dairycowsChose 12 healthy, 10 weeks after parturition Holstein dairy cows which had resemble body weigh, age,parity, and milk yield, then divided them into experiment group(EG) and control group(CG) at random. There were six dairy cows in each group. The dairy cows of CG were fed with roughage and concentrate, the dairy cows of EG, besides feeding with roughage and concentrate (the formulation is the same as CG), grazed in the mixed sward of perennial ryegrass and white clover every mornings and afternoons. The experiment was conducted from April to November, 2002. Individual body weigh was measured before and after test, and individual roughage intake, concentrate intake, herbage intake, milk yield and composition of milk were measured every month respectively.Form this experiment, it can be concluded that during the experiment period, body weights increased in both groups, the average body weight gain of EG and CG are 69 and 73kg respectively, and there was no significant difference between them (P>0.05). This suggests that grazing don't have significant effect on the body weigh gain.The total milk yield during experimental period for EG were 4421.17kg/cow, slightly higher than that for CG cows (4395.00 kg/cow), there was no significant difference between them (P>0.05). During the test period, the milk yield of EG is also significant higher than that of CG in April and May (P<0.05), whereas the resultwas adverse between them in July. The milk yield for EG and CG don't have significant effect in June, August, September, October, and November (P>0.05).The milk fat percentage of EG is significant higher than that of CG (P<0.05); The milk protein percentage of EG in July is significantly higher than that of CG(P<0.05), but in the rest test period, there is no significant difference between them(P>0.05). In addition, the milk protein percentage of EG have little change and there is no significant difference among the test periods, whereas the milk protein percentage of CG changes greatly, especially the result of July and September differs significantly(P<0.05), which indicates that the milk protein percentage of EG is steady.During the test periods, there is no significant difference of milk density between EG and CG(P>0.05);The milk lactose percentage of EG is slightly lower than that of CG, and there is no significant difference between them(P>0.05), which suggests that grazing has little effect on milk density and milk lactose percentage. 2.the supplement herbage intake and the substitution rate of herbage were measured , and thus indicate the optimum grazing periodsThe nutritive content of herbage changes with its growth period. The CP content of herbage has two summits along with its growth period. From April to June, The CP is increasing and get the first summit in June (15.73%), then has the lowest point in July (12.24%). From August, The CP is increasing again and get the second summit in October (21.04%). From November, the CP content of herbage quickly decreases to 13.04%.The ADF of herbage also has two summits along with its growth period. From April to July, the ADF is increasing and get the first summit in July (24.0%). After July, it begins to decreasing and get its lowest point in September(12.4%), then rise from September to October, and get the second summit in November (21.8%).The herbage intake of grazing reduces month by month, but in July it reduces suddenly and get its lowest point. In August, because of the temperature decreasing and plenty of white clover available, the herbage intake increases again, but decrease in September, October and November with the herbage decaying and milk yield decreasing.The substitution rate of her... |
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