Bull selection and use in northern Australia: 4. Calf output and predictors of fertility of bulls in multiple-sire herds
On 10 northern Australian properties, the number of calves sired (calf output) by individual bulls in multiple-sire matings was measured by DNA typing for paternity. There were 235 bulls (92 Santa Gertrudis, 25 5/8 Brahman and 119 Brahman) from 37 multiple-sire mating groups. Number of bulls in grou...
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Veröffentlicht in: | Animal reproduction science 2002-05, Vol.71 (1), p.67-79 |
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Zusammenfassung: | On 10 northern Australian properties, the number of calves sired (calf output) by individual bulls in multiple-sire matings was measured by DNA typing for paternity. There were 235 bulls (92 Santa Gertrudis, 25 5/8 Brahman and 119 Brahman) from 37 multiple-sire mating groups. Number of bulls in groups ranged from 2 to 25 and ages of bulls ranged from 2 to 5 years. Mating periods were for 3–12 months and bull mating percentages were 2.5–6%. In all, there were 4251 calves tested and the resolution of paternity ranged from 92.5 to 100% and averaged 97.7% across all sites. This included 9.9% of calves with no potential sires in any of the mating groups. Of the 235 bulls mated, 58% sired 10% or less calves in each of their respective mating groups with 6% not siring any calves. In contrast, 14% sired over 30% of the calves in each of the respective mating groups. When bulls were mated in groups of 8–24, the maximum percent of calves sired by individual bulls was 26±7% (mean±S.D.) with a range 11–36%. However, when bulls were mated in groups of 2–7, the maximum percent of calves sired by individual bulls was 59±19% with a range 24–94%. Calf output of bulls was moderately repeatable across years at four of five sites. Multiple regression models relating pre-mating measures of physical, seminal and behavioural traits to calf output were developed for the three breed groups. In all, only 138 of the 235 bulls were included in the models (40 Santa Gertrudis, 24 5/8 Brahman and 74 Brahman). Sheath and testicular traits, such as scrotal circumference and testicular tone, were generally not related to calf output, the exceptions being sheath depth in Brahman bulls which was negatively related (
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ISSN: | 0378-4320 1873-2232 |
DOI: | 10.1016/S0378-4320(02)00026-X |