title: Genetic parameters of three methods of temperament evaluation of Brahman calves.
abstract: The objective of this study was to estimate the heritability of 3 measures of temperament in Brahman and Brahman-influenced calves (n = 1,209). Individual animal pen scores (PS) were determined by a trained observer who evaluated groups of 5 or 4 calves at a time for willingness to be approached by a human. Exit velocity (EV) was the rate (m/s) at which each calf exited a squeeze chute. Temperament score (TS) was calculated individually as (PS + EV)/2. Temperament was evaluated at 5 different times of record (28 d preweaning, weaning, 28 d postweaning, 56 d postweaning, and yearling). Contemporary groups (n = 34) comprised calves of the same sex born in the same season of the same year. There were an average of 36 calves per contemporary group and group size ranged from 3 to 78 calves. Average weaning age (186 d) ranged from 105 to 304 d. Calves were born from 2002 through 2012. Random effects included additive genetic and the permanent environmental variance. The fixed effects analyzed were age of dam, sex of calf, contemporary group, fraction of Brahman (2 levels: 1 and 0.5), age of calf at record, and weaning age. At weaning, the mean PS was 2.68 ± 0.1, the mean EV was 2.41 ± 0.1, and the mean TS was 2.48 ± 0.1. The PS was affected by fraction of Brahman (P = 0.034) and tended to be affected by age of dam (P = 0.06). The EV was affected by contemporary group (P < 0.001) and tended to be affected by weaning age (P = 0.074). Contemporary group affected TS (P < 0.001). All 3 methods of temperament evaluation were affected by time of record (P < 0.001). The regression coefficients for PS, EV, and TS were 0.0023 ± 0.0014, 0.0022 ± 0.0012, and 0.0015 ± 0.0012 m·s(-1)·d(-1) of age, respectively. Estimates of maternal genetic effects were always 0 and omitted from final models. Estimates of heritability were 0.27 ± 0.1, 0.49 ± 0.1, and 0.43 ± 0.1 for EV, PS, and TS, respectively. Estimates of permanent environmental variances as proportions of phenotypic variance were 0.33 ± 0.1, 0.23 ± 0.1, and 0.33 ± 0.1 for EV, PS, and TS, respectively. There appears to be sufficient additive genetic variance for selective improvement of temperament characteristics in Brahman cattle.
authors.affiliation: Texas A&M AgriLife Research and Department of Animal Science, Texas A&M University, College Station 77843.
authors.forename: S E
authors.initials: SE
authors.lastname: Schmidt
authors.affiliation: Texas A&M AgriLife Research, Overton 75684.
authors.forename: D A
authors.initials: DA
authors.lastname: Neuendorff
authors.affiliation: Texas A&M AgriLife Research and Department of Animal Science, Texas A&M University, College Station 77843.
authors.forename: D G
authors.initials: DG
authors.lastname: Riley
authors.affiliation: Mississippi Agricultural and Forestry Experiment Station-Brown Loam Branch Experiment Station, Mississippi State University, Raymond 39154.
authors.forename: R C
authors.initials: RC
authors.lastname: Vann
authors.affiliation: Department of Animal and Dairy Sciences, Mississippi State University, Mississippi State 39762 Department of Biochemistry and Molecular Biology, Mississippi State University, Mississippi State 39762.
authors.forename: S T
authors.initials: ST
authors.lastname: Willard
authors.affiliation: Texas A&M AgriLife Research and Department of Animal Science, Texas A&M University, College Station 77843 Department of Veterinary Integrative Biosciences, Texas A&M University, College Station 77843.
authors.forename: T H
authors.initials: TH
authors.lastname: Welsh
authors.affiliation: Texas A&M AgriLife Research, Overton 75684 r-randel@tamu.edu.
authors.forename: R D
authors.initials: RD
authors.lastname: Randel
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000235:genetics / Q000523:psychology*; D002417:Cattle / Q000235:genetics / Q000523:psychology*; D005260:Female; D008297:Male; D011581:Psychological Tests; D019655:Quantitative Trait, Heritable; D013694:Temperament
keywords: Brahman calf; heritability; temperament