| The experiments were conducted to study the levels of postrumen starch and fat in diets on performance and Energy Balance of heat-stressed dairy cows. Before the feeding trail, we must measured the amount of postruen starch on usual feed, and then adjust the diets for different postrumen starch and fat.Part 1: Three bullock of Limousine×Lu Xi yellow cattle fitted with rumen cannulas were used for the measurement of amounts of postrumen starch in Cracked corn, Intrumescent corn, Steam-flacking corn , wheat,wheat bran,DDGS(corn),apple meal,soybean hull,soybean meal,alfalfa hay,corn silage and grass hay by the nylon bag technique. The results show that the amounts of postrumen starch(g/kg) were: 216.23, 89.14, 121.49, 60.37, 17.98, 9.23, 14.18, 6.13, 18.22, 8.11, 3.78 and 2.77.Part 2: According to the results of Part 1 and the currently diets. Investigate the effect of Postrumen starch and fat on performance and Energy Balance of mid-lactating heat-stressed dairy cows. Fifty-four Chinese Holstein cows (100-200DIM) was divided into three groups according to random block design by milk yield, MID and parity: Low Postrumen starch and High fat(PF101); Middle Postrumen starch and Middle fat(PF131) and High Postrumen starch and Low fat (PF161). ALL diets were formulated to provide similar levels of energy and protein. The average THI was 79.19 during experimental period. There was no difference among groups for DMI, BCS and weight(P>0.05). The milk yield was improved for PF161 compared with PF101; Protein content was higher for PF161 than PF101(P<0.05), and the NEl of PF161 is higher than PF101(P<0.1), but F:P was lower for for PF161 than PF101(P<0.05). The concentration of serum T4 was greater for cows fed PF161 diet than PF101(P<0.05), but PG was lower than PF101 (P <0.1). In conclusion, High Postrumen starch low fat diet can improve the milk protein content, and was benefit to multiparous mid-lactating heat-stressed dairy cows for milk performance and Energy Balance. |
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