Evaluation of beef sire breed and beef QTL effects on growth and carcass traits of beef x dairy crossbred animals
Date
2021-08
Authors
Lucas, Kayla Marie
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Koltes, James E
Saatchi, Mahdi
Liu, Peng
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Abstract
To enhance the value of calves sold off the farm, dairy producers have selectively mated low genetic females to beef sires. Crossbreeding beef sires to dairy dams has helped to improve growth rates and carcass yield traits compared to purebred dairy beef; however, beef x dairy crossbred performance has been unexpectedly variable in performance. A theorized reason for this is the lack of selection pressure on beef sires. Current selection strategies revolve around cheap, black-hided bulls with little to no consideration of beef type traits. Moreover, no genetic tools have been developed for the specific use of selecting beef sires for use on dairy females to maximize beef production. Thus, the objectives of this study were to assess various beef sire breeds through the performance of their crossbred beef x dairy offspring and evaluate if pleiotropic, large-effect beef quantitative trait loci (QTL) could be useful in genomic selection of beef sire candidates.
Growth data (n=81,039) consisted of crosses from Brown Swiss (BS), Holstein (HO), and Jersey (JE) dams bred to Limousin (LM) or Simmental (SM) beef sires while carcass data (n=73,183) were available on crosses consisting of HO and JE dams mated to LM and LimFlex (LA; Limousin-Angus hybrid) sires. Growth and carcass traits were affected by sire breed such that the percentage of SM in an animal’s pedigree (SM%) had the greatest impact on 205d adjusted weaning weights (+0.65lbs./SM%) and 365d adjusted yearling weights (+0.97lbs./SM%) across dairy breeds. Carcass weights (CW) were not different between LM and LA sired HO crosses (P>0.9), but LA x JE crosses had 8.71 lbs. heavier CW (P<0.0001) than LM x JE crosses. Further analysis of carcass traits indicated that LM x dairy crosses had larger ribeye areas (REA; P<0.0001), less back fat (BF; P<0.0001), and lower USDA marbling scores (MARB; P<0.0001) than LA x dairy crosses.
Additionally, 418 total genotyped SM, LM, and LA sires had 7,988, 46,490, and 9,992 beef x dairy offspring, respectively, with recorded growth and carcass trait data. Offspring phenotypes were evaluated by sire genotype for 5 large-effect, pleotropic QTL previously associated with growth and carcass traits in U.S. beef cattle. The Limousin-specific QTL on BTA2 accounted for an estimated 0.78% and 3.48% of the phenotypic variance in WWadj and YWadj. The positive effects on carcass traits suggests selection of homozygous BB sires can enhance production from dairy-influenced animals. Further, results of this study indicate selection of sires homozygous for the favorable allele at the QTL on BTA6 could increase productivity. These markers were estimated to account for >1% of the phenotypic variance in REA and BF of Limousin and LimFlex sired offspring and for >1% of the phenotypic variance in MARB of LimFlex sired offspring. The estimate of the effects for the QTL on BTA6 where in the positive direction for all carcass traits. There is evidence selection of the QTL on BTA7 could influence REA and MARB of Limousin sired animals (>1% of the phenotypic variance); however, selection for the favorable allele for REA has a negative effect on MARB at this locus. Selection of the favorable allele for the QTL on BTA14 may positively influence growth and carcass traits; however, there is a significant dairy breed effect. Lastly, the QTL on BTA20 had inconsistency in favorable allele for carcass traits, indicating difficulty in utilization of this locus for selection within Limousin and LimFlex beef sires.
In conclusion, beef sire breed and beef QTL genotype impacted beef x dairy crossbred offspring beef production for various growth and carcass traits. These phenotypic and genotypic results can be readily integrated into current beef sire selection strategies by dairy producers who desire to increase the beef production capabilities, and thus, profitability of their surplus calves.
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