Management of Breeding Bull Batteries

King, E. H.

doi:10.1002/9781119602484.ch11

Cited by 1 publication

(2 citation statements)

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“…Thus, increasing the number of females serviced by a single sire will likely not impact pregnancy rates on first return to estrus. As previously stated, decreasing the bull:cow ratio to 1:50 or 1:60 would achieve a bull to open cow ratio of 1:25 or 1:30, following recommendations (Healy et al, 1993;Chenoweth, 2015;King, 2015). Provided the bull is proven fertile, decreasing the bull:cow ratio will likely have more economic benefit by reducing the bull associated costs than would be detrimental from any potential decreases in pregnancy rates to first service.…”

Section: Discussionmentioning

confidence: 96%

“…The current recommended bull:cow ratio is 20 to 30 cows in pasture for every one bull (Chenoweth, 2015;King, 2015). The Auburn formula, similarly, recommends the number of cows serviced be proportional to bull age for those less than 36 mo, or proportional to scrotal circumference of bulls greater than 36 cm in a single sire setting (Wenzel et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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58 A retrospective analysis of bull:cow ratio effects on pregnancy rates of beef cows previously enrolled in fixed-time artificial insemination protocols

Timlin

Hungerford

Redifer

et al. 2019

Journal of Animal Science

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This retrospective study analyzed the effect of bull:cow ratio on pregnancy rates of cows returning to estrus after enrollment in fixed-time artificial insemination (TAI). Data were compiled over the course of 6 breeding seasons between 2014 and 2017 from the Virginia Department of Corrections herd containing 15 farms and 141 groups of cows (average 44 cows/group). Multiparous cows aged 2 years and older (n = 6002) were exposed to estrus synchronization. Non-pregnant cows after TAI (n = 3079, average 21 cows/group) were exposed to natural service with bulls diagnosed as fertile by a breeding soundness exam. Percent data were given an arcsine transformation. A one-way ANOVA evaluated TAI rates by season and a linear regression was performed to compare conception rates to the bull:cow ratio. Pregnancy rate to TAI among groups averaged 53% and ranged from 11% to 83%. First bull pregnancy rate of cows returning to estrus was 47% overall, with fall seasons having greater conception rates than spring (51.1% vs. 44.5%, P = 0.03). The ratio of bulls to total number of cows ranged from 1:8 to 1:68 with an average ratio of 1:28. The ratio of bulls to the number of open cows ranged from 1:2 to 1:39 with an average ratio of 1:14. There was no correlation between the bull:cow ratio and return to estrus pregnancy rate (r = -0.12), and there was no correlation between the number of open cows per bull and return to estrus conception rates (r = -0.17). Thus, higher bull:cow ratios (between 1:8 and 1:68) did not effect return to estrus pregnancy rate; producers may consider a lower number of bulls needed for natural service breeding post TAI, decreasing bull related costs and increasing the economic feasibility of adopting TAI protocols

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Section: Discussionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%