Holloway J W, Butts W T
J Anim Sci. 1983 Apr;56(4):960-71. doi: 10.2527/jas1983.564960x.
Forage intake, milk production, calf growth and efficiencies of milk production and calf growth were estimated for 198 lactations of 91 mature Angus cows grazing fescue-legume or fescue pastures. Cows calved January through March and calves were weaned in October in each of the 5 yr of the experiment. Cows grazing fescue-legume consumed 1.7 kg/d more (P less than .01) dry matter (DM) that was 4.6 percentage units more (P less than .01) digestible than cows grazing fescue. Cows grazing fescue-legume produced .4 kg/d more (P less than .01) milk and weaned 23.8 kg more (P less than .01) calf than cows grazing fescue. This increased production required an additional intake/cow-calf unit of 2.3 kg of digestible DM for each additional kilogram of calf weaned. Cows grazing fescue-legume were less efficient in calf production at least partially because they gained 33.3 kg more (P less than .01) weight and 1.82 mm more (P less than .01) fat cover at the 12th rib during lactation than cows grazing fescue. Cows producing relatively large amounts of milk consumed more digestible DM, weaned heavier calves, and were more efficient producers of milk and weaned calf regardless of pasture type grazed. The influence of milk production on these variables was more dramatic for cows grazing fescue than for those grazing fescue-legume. Cow type favoring maximum conversion of digestible DM intake by cow and calf to calf gain was different for the two types of pasture. For cows grazing fescue, those having either small amounts of fatness or having small structural sizes, regardless of milk production, were the most efficient. Structural size was not related to efficiency for cows grazing fescue-legume. Fatness had little influence on efficiency of low milking cows. The relationship of structural dimension and efficiency for cows grazing fescue was due to interrelationships of structural dimension, change in cow weight and fatness during lactation, and calf weaning weight: cow weight ratio. Relationships between efficiency and fatness could not be attributed to these variables.
对91头成熟安格斯母牛在198个泌乳期内放牧于羊茅 - 豆科或羊茅牧场的情况进行了采食量、产奶量、犊牛生长以及产奶效率和犊牛生长效率的评估。在为期5年的试验中，母牛于1月至3月产犊，犊牛于10月断奶。与放牧羊茅牧场的母牛相比，放牧羊茅 - 豆科牧场的母牛每天多采食1.7千克（P < 0.01）干物质，且可消化干物质含量高出4.6个百分点（P < 0.01）。放牧羊茅 - 豆科牧场的母牛每天多产奶0.4千克（P < 0.01），断奶时犊牛体重比放牧羊茅牧场的母牛重23.8千克（P < 0.01）。每多断奶1千克犊牛，每头母牛 - 犊牛单位的可消化干物质摄入量需额外增加2.3千克。放牧羊茅 - 豆科牧场的母牛在犊牛生产方面效率较低，至少部分原因是在泌乳期，它们比放牧羊茅牧场的母牛体重增加了33.3千克（P < 0.01），第12肋骨处的脂肪层厚了1.82毫米（P < 0.01）。无论放牧何种牧场类型，产奶量相对较高的母牛消耗更多可消化干物质，断奶时犊牛体重更重，产奶和断奶犊牛的效率更高。对于放牧羊茅牧场的母牛，产奶量对这些变量的影响比对放牧羊茅 - 豆科牧场的母牛更为显著。两种牧场类型中，有利于母牛和犊牛将可消化干物质摄入量最大程度转化为犊牛增重的母牛类型有所不同。对于放牧羊茅牧场的母牛，无论产奶量如何，脂肪含量少或体型小的母牛效率最高。对于放牧羊茅 - 豆科牧场的母牛，体型与效率无关。脂肪含量对低产奶牛的效率影响不大。放牧羊茅牧场的母牛体型与效率的关系是由于体型、泌乳期母牛体重和脂肪含量的变化以及犊牛断奶体重与母牛体重之比之间的相互关系。效率与脂肪含量之间的关系不能归因于这些变量。
