Effects of total replacement of corn silage with sorghum silage on milk yield,composition, and quality

M.Cattani; N.Guzzo; R.Mantovani; L.Bailoni

摘要

Background:In the last years,difficulties occurring in corn cultivation (i.e.,groundwater shortages,mycotoxin contamination) have been forcing dairy farmers to consider alternative silages.Some experiments conducted on lactating cows have proven that the total replacement of corn silage with sorghum silage did not reduce milk yield.However,this kind of substitution involves supplementing sorghum-based diets with grains,to compensate for the lower starch content of sorghum silage compared to corn silage.Change of silage type and inclusion of starch sources in the diet would influence rumen fermentations,with possible effects on milk composition (i.e.,fatty acid profile) and coagulation properties.A worsening of milk coagulation properties would have a negative economic impact in Italy,where most of the milk produced is processed into cheese.This study was designed to compare milk composition and quality,with emphasis on fatty acid profile and coagulation properties,in dairy cows fed two diets based on corn or sorghum silage.Results:The sorghum diet reduced milk yield (P =0.043) but not 4％ fat corrected milk (P =0.85).Feeding sorghum silage did not influence milk contents of protein (P =0.07) and lactose (P =0.65),and increased fat content (P =0.024).No differences emerged for milk concentrations of saturated (P =0.61) and monounsaturated fatty acids (P=0.50),whereas polyunsaturated fatty acids were lower (P ＜ 0.001) for the sorghum diet.Concentrations of n-6 (P ＜ 0.001) and n-3 fatty acids (P =0.017) were lower in milk of cows fed the sorghum diet.Milk coagulation properties did not differ between the two diets,except the "a30" (the curd firmness,expressed in mm,30 min affer rennet addition),that was lower (P =0.042) for the sorghum diet.Conclusions:Feeding a forage sorghum silage,properly supplemented with corn meal,as total replacement of corn silage maintained milk composition and did not influence negatively milk coagulation properties,which have a great economic relevance for the Italian dairy industry.Thus,silages obtained from forage sorghums could have a potential as substitute of corn silages in dairy cow diets.

机译：背景：近年来，玉米种植中遇到的困难（即地下水短缺，霉菌毒素污染）迫使奶农考虑使用其他青贮饲料。一些对泌乳母牛进行的实验证明，用高粱青贮饲料完全替代了玉米青贮饲料确实不会降低牛奶产量。但是，这种替代方法是在谷物中添加高粱饲料，以补偿高粱青贮饲料中的玉米淀粉含量低于玉米青贮饲料。青贮饲料类型的变化和饲料中淀粉源的添加会影响瘤胃发酵，可能会对牛奶成分（即脂肪酸分布）和凝结特性产生影响。牛奶凝结特性的恶化将对意大利产生不利的经济影响，因为意大利生产的大部分牛奶都加工成奶酪。比较饲喂两种奶牛的奶的成分和质量，重点是脂肪酸谱和凝血特性结果：高粱饲料降低了牛奶产量（P = 0.043），但降低了4％的脂肪校正牛奶（P = 0.85）。饲喂高粱青贮饲料不会影响牛奶中的蛋白质含量（P = 0.07）和乳糖（P = 0.65）和增加的脂肪含量（P = 0.024）。饱和牛奶（P = 0.61）和单不饱和脂肪酸（P = 0.50）的牛奶浓度没有差异，而多不饱和脂肪酸较低（P ＜0.001）高粱饮食的牛奶中n-6（P <0.001）和n-3脂肪酸（P = 0.017）的含量较低。两种饮食之间的牛奶凝结特性没有差异。高粱饲料的“ a30”（凝乳硬度，以毫米表示，加入凝乳酶30分钟后）较低（P = 0.042）。玉米青贮饲料可保持牛奶成分，并且不会对牛奶的凝结特性产生负面影响，因此经济性非常好因此，从饲草高粱中获得的青贮饲料有潜力替代奶牛日粮中的玉米青贮饲料。

Effects of total replacement of corn silage with sorghum silage on milk yield,composition, and quality

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