Freitas A F, Wilcox C J, Costa C N
Empresa Brasileira de Pesquisa Agropecuárua, Centro Nacionel de Pesquisa Gado de Leite, Brazil.
J Dairy Sci. 1998 Aug;81(8):2306-11. doi: 10.3168/jds.S0022-0302(98)75811-4.
Lactation records (n = 2362) of 1402 crossbred cows in 22 cooperating dairy herds in southeastern Brazil were evaluated. Cows were mixtures of Zebu (Gir, Guzera, and unknown) and European breeding (mostly Holstein). Lactation milk yields were expressed as total, 3050-d, or deviated 305-d yields, either adjusted or unadjusted for days in milk (DIM). Mean DIM was 280. Arithmetic means unadjusted for DIM were 1942, 1666, and 5 kg per record. Milk yields of daughters from sires of 6/8 and 7/8 European breeds were higher than yields of daughters from sires of 5/8 European breeds when data were either adjusted or unadjusted for DIM. The differences associated with breed group of sire were only slightly reduced when records were adjusted for DIM. There was no evidence of a decline in milk yield as the fraction of European breeding of the sire increased from 6/8 to 7/8. For a given breed group of sire, whether the grandsire was purebred or crossbred had no detectable effect. These results should be useful in determining strategies for crossbreeding of dairy cows in tropical areas, particularly when crossbred sires are used.
对巴西东南部22个合作奶牛场的1402头杂交奶牛的泌乳记录（n = 2362）进行了评估。这些奶牛是瘤牛（吉尔牛、古泽拉牛和未知品种）与欧洲品种（主要是荷斯坦牛）的混合品种。泌乳奶量以总奶量、305天奶量或偏离的305天奶量表示，对泌乳天数（DIM）进行了调整或未调整。平均泌乳天数为280天。未对泌乳天数进行调整时，每条记录的算术平均值分别为1942千克、1666千克和5千克。当对数据进行泌乳天数调整或未调整时，父本欧洲品种占6/8和7/8的女儿的奶量高于父本欧洲品种占5/8的女儿的奶量。当对记录进行泌乳天数调整时，与父本品种组相关的差异仅略有减小。没有证据表明随着父本欧洲品种比例从6/8增加到7/8，奶量会下降。对于给定的父本品种组，祖父是纯种还是杂交没有可检测到的影响。这些结果对于确定热带地区奶牛杂交策略应是有用的，特别是在使用杂交公牛时。
