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Choice of artificial insemination beef bulls used to mate with female dairy cattle
Berry, Donagh Ring, S.C. Twomey, A.J. Evans, R.D.
Berry, Donagh
Ring, S.C.
Twomey, A.J.
Evans, R.D.
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2020-02
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Berry, D. P., Ring, S. C, Twomey, A. J., Evans, R. D. Choice of artificial insemination beef bulls used to mate with female dairy cattle, Journal of Dairy Science, 2020, 103 (2), 1701-1710. doi: https://doi.org/10.3168/jds.2019-17430
Abstract
Understanding the preferences of dairy cattle producers
when selecting beef bulls for mating can help
inform beef breeding programs as well as provide
default parameters in mating advice systems. The
objective of the present study was to characterize the
genetic merit of beef artificial insemination (AI) bulls
used in dairy herds, with particular reference to traits
associated with both calving performance and carcass
merit. The characteristics of the beef AI bulls used
were compared with those of the dairy AI bulls used on
the same farms. A total of 2,733,524 AI records from
928,437 females in 5,967 Irish dairy herds were used.
Sire predicted transmitting ability (PTA) values and
associated reliability values for calving performance
and carcass traits based on national genetic evaluations
from prior to the insemination were used. Fixed effects
models were used to relate both genetic merit and the
associated reliability of the dairy and beef bulls used on
the farm with herd size, the extent of Holstein-Friesian
× Jersey crossbreeding adopted by the herd, whether
the herd used a technician insemination service or do-ityourself,
and the parity of the female mated. The mean
direct calving difficulty PTA of the beef bulls used was
1.85 units higher than that of the dairy bulls but with
over 3 times greater variability in the beef bulls. This
1.85 units equates biologically to an expectation of 1.85
more dystocia events per 100 dairy cows mated in the
beef × dairy matings. The mean calving difficulty PTA
of the dairy AI bulls used reduced with increasing herd
size, whereas the mean calving difficulty PTA of the
beef AI bulls used increased as herd size increased from
75 cows or fewer to 155 cows; the largest herds (>155
cows) used notably easier-calving beef bulls, albeit the
calving difficulty PTA of the beef bulls was 3.33 units
versus 1.67 units for the dairy bulls used in these herds.
Although we found a general tendency for larger herds
to use dairy AI bulls with lower reliability, this trend
was not obvious in the beef AI bulls used. Irrespective
of whether dairy or beef AI bulls were considered, herds
that operated more extensive Holstein-Friesian × Jersey
crossbreeding (i.e., more than 50% crossbred cows)
used, on average, easier calving, shorter gestationlength
bulls with lighter expected progeny carcasses of
poorer conformation. Mean calving difficulty PTA of
dairy bulls used increased from 1.39 in heifers to 1.79
in first-parity cows and to 1.82 in second-parity cows,
remaining relatively constant thereafter. In contrast,
the mean calving difficulty PTA of the beef bulls used
increased consistently with cow parity. Results from
the present study demonstrate a clear difference in the
mean acceptable genetic merit of beef AI bulls relative
to dairy AI bulls but also indicates that these acceptable
limits vary by herd characteristics.