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Bull selection and use in northern Australia. 1. Physical traits

McGowan, M.R. and Bertram, J.D. and Fordyce, G. and Fitzpatrick, L.A. and Miller, R.G. and Jayawardhana, G.A. and Doogan, V.J. and De Faveri, J. and Holroyd, R.G. (2002) Bull selection and use in northern Australia. 1. Physical traits. Animal Reproduction Science, 71 (1). pp. 25-37.

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Article Link(s): http://dx.doi.org/10.1016/S0378-4320(02)00023-4

Publisher URL: http://www.elsevier.com

Abstract

A systematic breeding soundness examination, including assessment of serving capacity was conducted on 5/8 Brahman, Brahman and Belmont Red bulls, most aged 2–4 years, at 12 different cattle properties across northern Australia. A subset of bulls (n=235) were subsequently mated in various groups, as multiple-sires, to cows and heifers at bull:female ratios of 2.5–6%. The number of calves sired by individual bulls (calf output) was determined by DNA typing for paternity. Overall, the incidence of physical abnormalities that were judged likely to result in reduced reproductive performance was low (5.6–12% of bulls). Measures of key physical traits scrotal circumference, sheath depth (vertical distance from ventral abdominal wall to preputial orifice), and sheath score were moderately to highly repeatable. Except in Belmont Red bulls, liveweight was positively correlated with scrotal circumference (r=0.36–0.78; P<0.01), and both traits increased with age. In 2-year-old Brahman bulls only, percent normal spermatozoa was correlated with scrotal circumference (r=0.34; P<0.05). However, 12 and 15% of Santa Gertrudis and Brahman bulls, respectively, with greater than or equal to the recommended threshold values for scrotal circumferences, had less than 50% morphologically normal spermatozoa. Size and conformation of the umbilicus was associated with conformation of the sheath, and influenced mating ability in 2-year-old Brahman and 3-year-old Santa Gertrudis bulls. In 2-year-old Brahman bulls umbilical cord thickness was positively related (r=0.36; P<0.05) to sheath depth, and negatively related (r=-0.65; P<0.05) to number of mounts and serves in a serving capacity test. In 3-year-old Santa Gertrudis bulls navel (external umbilical scar) score was negatively related to the number of serves (r=-0.53; P<0.01) in a serving capacity test. None of the physical traits measured were consistently included in the final regression model for calf output for each breed.

Item Type:Article
Additional Information:© Elsevier Science B.V.
Keywords:Cattle-male reproduction; Bos indicus; physical traits; scrotal circumference; sheath; fertility.
Subjects:Science > Biology > Reproduction
Animal culture > Cattle
Deposited On:26 Feb 2004
Last Modified:15 Jun 2011 23:35

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