Date of Award
Master of Science (MS)
Animal, Dairy, and Veterinary Sciences
Norris J. Stenquist
Performance testing data from a registered herd of Hereford cattle in Northern Utah for the years 1974 through 1980 were analyzed in this study. The cattle consisted of a spring calving herd, approximately 440 cows, and a fall calving herd, approximately 120 cows. Five weaning traits (weaning weight, weight per day of age, 205-day weaning weight, 205-dat adjusted weaning weight, weaning index) and four yearling traits (yearling weight, average daily gain, 365-day adjusted yearling weight, yearling index) were computed on the offspring from both herds, for the years mentioned, to test the influence of a performance testing program on the productivity in the test herd.
Weaning weight increased from 346.0 lbs. in 1974 to 404.0 lbs. in 1977, an increase of 58 lbs.. A decline was experienced in the succeeding years 404.0 lbs. in 1977 to 380.2 lbs. in 1980, a decline of 23.8 lbs..
Yearling weight increased from 649.0 lbs. in 1975 to 717.7 lbs. in 1977, an increase of 68.7 lbs. A decline of 29.4 lbs. was observed in 1978 and an increase of 11.2 lbs. from 1978 to 1980.
Other influences on weaning traits and yearling traits such as age of dam, age at weaning, season of birth and heritabilities were also observed.
Age of dam influence was compared to additive adjustment factors recommended by the Beef Improvement Federation and found to be comparable to age nine. Adjustment factors for dams from nine through eleven years of age was recommended to be 12.0, 20.0, and 30.0 pounds respectively for both males and females. Adjustment for 12-year old dams was 40.0 and 42.0 pounds for males and females respectively and for 13-year old dams a 44.0 and 54.0 pound adjustment for males and females respectively.
Age at weaning was found to be most applicable when limited from 160 to 250 days as presently recommended by the Beef Improvement Federation, with 205-day weight as the optimum weight.
Season of birth significantly (p<0.1) favored the spring calving season. Warmer weather and availability of better feed seemed to be the major influencing factors.
Heritabilities for weaning weight, 205-day weaning weight, 2015-day adjusted weaning weight and weaning index were computed to be 0.142, 0.142, 0.136 and 0.113 respectively. Heritabilities for yearling weight, average daily gain, 365-day adjusted yearling weight and yearling index were 0.246, 0.120, 0.252 and 0.244 respectively. These heritabilities are lower than most reported in the literature. Longer calving season, two calving herds and above average range of ages at which weaning and yearling traits were taken could have influenced these heritabilities downward.
Jacobson, Ross A., "The Impact of Performance Testing On Production Selection" (1982). All Graduate Plan B and other Reports. 682.