Seasonal Body Condition Score and Yield Dynamics of Normande Crossbreds Compared with Purebreds and Other Crossbreds and Telomere Length in Purebred and Crossbred Cattle

Open Access
Brown, Dustin Edward
Graduate Program:
Animal Science
Master of Science
Document Type:
Master Thesis
Date of Defense:
June 29, 2012
Committee Members:
  • Chad Daniel Dechow, Thesis Advisor
  • Wansheng Liu, Thesis Advisor
  • Kevin John Harvatine, Thesis Advisor
  • Kathy Jo Soder, Thesis Advisor
  • Crossbreeding
  • Telomere
  • Normande
  • Grazing
  • Body Condition Score
The objectives of this study were to evaluate body condition score (BCS), milk production, reproductive performance and how performance changes across seasons and system (grazing, non-grazing) among animals sired by Normande, Ayrshire, Holstein, Jersey, and other breeds and also evaluate telomere length among crossbred and purebred cattle. Six herds with Normande crossbreds were visited once each during January, May, August, and October during 2011 to represent different seasons. Milk production and pedigree information was collected for all herds. One herd in Minnesota also provided pedigree and milk production information, but no BCS information. Cattle from one herd with Normande crossbreds provided blood for DNA extraction and telomere length analysis. Purebred Holsteins from the Penn State dairy research center, crossbred and purebred beef animals from the Penn State beef research center and a commercial Pennsylvania beef farm also provided blood for telomere length analysis. Multiple trait mixed-models were used to analyze BCS, milk yield, fat yield and percentage, protein yield and percentage, somatic cell score, and calving interval among Normande crossbreds and their herd mates sired by Ayrshire, Holstein, Jersey and other breeds. Normande sired cattle had greater body condition than animals sired by Ayrshires, Holsteins, Jerseys and other breeds. Daily milk yield, fat yield, and protein yield were all influenced by season in herds that utilized greater amounts of pasture and were lowest during the summer months of July through August. Normande cattle were able to mobilize more body reserves during the summer season, when pasture growth was expected to be low, than cows sired by other breeds; however, differences with Ayrshire, Holstein, and Jersey sired cattle were not significant. Decreases in fat yield were lower for Normande (-0.08 kg/d) during the summer months when compared to Holstein sired animals (-0.11 kg/d). Cows sired by bulls of unknown origin, crossbred sires, or breeds other than Ayrshire, Holstein, Jersey or Normande had larger declines in milk, fat and protein yield during summer months in grazing herds. This reinforces the need to use proven sires, even in grazing systems that incorporate crossbreeding. Mixed models were used to estimate telomere length for individual animals, herd, and breeds. Dairy and beef cows were evaluated separately because there was no breed overlap between herds to facilitate evaluation of breed versus herd effects. Herd was highly significant within both beef and dairy analyses (P< 0.001). There was a significant decline in telomere length as age increased in dairy cattle (P<0.05), but the decline was not significant for beef cattle (P>0.05). Adding breed to the model was not significant for dairy (P = 0.71) or beef (P = 0.92) animals, indicating that there was no difference in telomere length between crossbred and purebred animals. Results suggested wide variation among animals in telomere length at any given age. There was no evidence that longer telomere length explained the improved survivability reported for crossbred dairy cattle.