While several studies in cattle have confirmed the improved performance achievable from selection on total merit indexes, these studies have solely been confined to specific-purpose beef or dairy total merit indexes. Validation studies of total merit indexes used to select beef sires for use on dairy females are lacking. The objective here was to fill this void by quantifying the performance of beef × dairy progeny where the sire excels in either a total merit index encompassing calving performance and beef performance traits (dairy-beef index; DBI) or excels in a subindex based solely on calving performance (CLV); for comparative purposes, these beef × dairy progeny were also compared with dairy × dairy progeny. A total of 123,785 calving records from 101,773 dairy cows calving in 3,065 dairy herds were used; of these, 48,875 progeny also had carcass information. The beef sires were stratified into 5 equally sized groups based separately on their DBI or CLV. Linear and threshold mixed models were used to compare calving and carcass performance of all 3 sire genotypes. Of the 415 sires that ranked in the highest of the 5 strata on the CLV subindex, only 52% of them ranked in the highest stratum for the DBI. The percentage of primiparae requiring any assistance at calving was 2 to 3 percentage units greater for the higher DBI sires relative to both the higher CLV beef sires and the dairy sires (not ranked on anything); no difference existed in multiparae. The extent of calving difficulty in primiparae was, however, less in higher DBI beef sires relative to both the higher CLV beef sires and the dairy sires, although the differences were biologically small. Perinatal mortality was greatest in the beef sires relative to the dairy sires, but no difference existed between the high CLV or high DBI beef sires. No difference in progeny gestation length was evident between the high DBI or high CLV beef sires, although both were >2 d longer than progeny from dairy sires. The higher DBI sires produced progeny with heavier, more conformed carcasses relative to the progeny from both high CLV beef sires and dairy sires. No differences existed between the progeny of the beef sires ranked highly on the CLV versus those ranked highly on the DBI for the probability of achieving the specification for carcass weight (between 270 and 380 kg) or fat score; the higher DBI animals, however, had a 4 to 10% greater probability of achieving the minimum carcass conformation required. In all instances, the beef sires had a greater probability of achieving all specifications relative to the progeny from the dairy sires with the difference for conformation being particularly large. Results indicate that more balanced progeny can be generated using a DBI, helping meet the requirements of both dairy and beef producers. Ignoring market failure across sectors, using higher DBI sires could increase dairy herd profit by 3 to 5% over and above the status quo approach to selection in dairy (i.e., CLV subindex).

中文翻译：

---

观察到的后代表现证明了将遗传优良的牛肉公牛交配给奶牛雌性的好处。

尽管有几项关于牛的研究证实，通过选择总优点指数可以提高性能，但这些研究仅局限于专用牛肉或乳制品总优点指数。缺乏用于选择供母乳牛使用的牛肉品种的总价值指标的验证研究。此处的目的是通过量化牛肉x乳品后代的表现来填补这一空白，在此情况下，父亲在包括产犊表现和牛肉表现特征的总优点指数（乳牛-牛肉指数； DBI）方面表现优异，或者在仅基于以下指标的子指数方面表现优异产犊表现（CLV）; 为了比较，将这些牛肉×乳品后代与乳品×乳品后代进行比较。使用了3,065头牛群的101,773头奶牛的123,785条产犊记录；其中48 875后代也有car体信息。牛肉父亲根据其DBI或CLV分为5个大小相等的组。线性和阈值混合模型用于比较所有3个父本基因型的产犊和cas体性能。在CLV子索引的5个层次中排名最高的415个父系中，只有52％的父亲在DBI中排名最高。与较高的CLV牛肉和奶牛（没有排名）相比，DBI较高的犊牛在产犊时需要任何帮助的百分比要高出2-3％。多参数没有差异。尽管较高的CLV牛肉和乳品公牛，初产妇的产犊困难程度均低于较高DBI的牛公牛，尽管生物学上的差异很小。相对于乳品公母，牛肉公母的围产期死亡率最高，但是高CLV或高DBI母公母之间没有差异。高DBI或高CLV牛种之间的后代妊娠期长度没有明显差异，尽管两者均比乳品种的后代长2 d以上。相对于高CLV牛肉和奶牛后代，较高的DBI父亲产生的后代具有更重，更顺应的car体。在CLV上排名靠前的牛肉后代与在DBI上排名靠前的牛肉后代之间，在达到for体重量（270至380公斤）或脂肪评分规范方面没有差异。然而，较高DBI的动物达到所需最小car体构象的可能性要高4％至10％。在所有情况下 相对于来自奶牛后代的后代而言，牛肉后代具有更大的可能性达到所有规格，构象差异特别大。结果表明，使用DBI可以产生更均衡的后代，有助于满足奶牛和牛肉生产者的需求。忽略跨部门的市场失灵，使用较高的DBI父本可以使乳牛群利润比常规乳制品选择方法（即CLV子指数）提高3％至5％。