Kress D D, Doornbos D E, Anderson D C, Davis K C
Montana State University, Bozeman 59717, USA.
J Anim Sci. 1996 Oct;74(10):2344-8. doi: 10.2527/1996.74102344x.
The objective of this study was to estimate genetic components for milk production of Hereford (HH), Tarentaise (TT), and Hereford x Tarentaise or Tarentaise x Hereford (HT) cows under range conditions at the Northern Agricultural Research Center, Havre, MT. Milk production of 494 cow-calf pairs was estimated by the weigh-suckle-weigh procedure from 1989 to 1994. Milk production and cow and calf weights were measured at 40 d (early) and 120 d (late) of lactation. The mating scheme was a 3 x 3 design in which HH, HT, and TT cows were mated with HH, HT, and TT sires, producing calves that were varying percentages of Hereford and Tarentaise. Data were analyzed by least squares procedures according to a model that included year, age of cow, sex of calf, linear regression on calf age, and linear regressions on coefficients that coded for various genetic components. These genetic components were breed individual, breed maternal, breed grand maternal, individual heterosis (calf heterosis), and maternal heterosis (cow heterosis). Coefficients for genetic components were such that breed effects estimated TT-HH and regressions on heterosis values estimated the full effect of heterosis. The breed individual genetic component was significant only for calf early and late weights; Tarentaise calves were lighter. Breed maternal was significant for most traits, and these effects were positive for milk production (2.16 and 3.77 kg/d for early and late, respectively) and calf weights but negative for cow weights. Individual heterosis was not significant for early milk production but was significant for late milk production (1.05 kg/d) and calf weights (2.3 and 8.1 kg for early and late, respectively). Maternal heterosis was significant for most traits and increased early milk production (1.25 kg/d), calf weights (4.5 and 5.8 kg for early and late, respectively), and cow weights (18.1 and 6.0 kg for early and late, respectively).
本研究的目的是估计在蒙大拿州哈弗市北部农业研究中心的放牧条件下，赫里福德牛（HH）、塔伦泰斯牛（TT）以及赫里福德×塔伦泰斯或塔伦泰斯×赫里福德（HT）母牛产奶量的遗传成分。1989年至1994年期间，通过称重-哺乳-称重程序对494对母牛-犊牛组合的产奶量进行了估计。在泌乳期的40天（早期）和120天（晚期）测量产奶量以及母牛和犊牛的体重。交配方案为3×3设计，其中HH、HT和TT母牛分别与HH、HT和TT公牛交配，所产犊牛具有不同比例的赫里福德和塔伦泰斯血统。根据一个模型，采用最小二乘法对数据进行分析，该模型包括年份、母牛年龄、犊牛性别、犊牛年龄的线性回归以及编码各种遗传成分的系数的线性回归。这些遗传成分包括品种个体、品种母体、品种祖母体、个体杂种优势（犊牛杂种优势）和母体杂种优势（母牛杂种优势）。遗传成分的系数使得估计的品种效应为TT - HH，杂种优势值的回归估计了杂种优势的全部效应。品种个体遗传成分仅对犊牛早期和晚期体重有显著影响；塔伦泰斯犊牛体重较轻。品种母体对大多数性状有显著影响，这些效应在产奶量方面为正（早期和晚期分别为2.16和3.77千克/天），对犊牛体重为正，但对母牛体重为负。个体杂种优势对早期产奶量不显著，但对晚期产奶量（1.05千克/天）和犊牛体重（早期和晚期分别为2.3和8.1千克）显著。母体杂种优势对大多数性状显著，提高了早期产奶量（1.25千克/天）、犊牛体重（早期和晚期分别为4.5和5.8千克）以及母牛体重（早期和晚期分别为18.1和6.0千克）。
