"Optimal" Length for Bull Tests

[MikeC]

Optimum postweaning test for measurement of growth rate, feed intake, and feed efficiency in British breed cattle
J. A. Archer, P. F. Arthur, R. M. Herd, P. F. Parnell and W. S. Pitchford
NSW Agriculture, Agricultural Research Centre, Trangie, Australia.

The optimum duration of test for measurement of growth rate, feed intake, feed conversion, and residual feed intake was examined using postweaning feed intake and weight data from 760 Angus, Hereford, Polled Hereford, and Shorthorn heifer and Angus bull progeny from 78 sires. Variance components, heritability, phenotypic and genetic correlations, and the efficiency of selection using shortened tests compared with a 199-d test were used as criteria to assess the optimum test length. The results indicated that a 35-d test was sufficient for measurement of feed intake, whereas a 70-d test was required to measure growth rate, feed conversion, and residual feed intake without compromising the accuracy of measurement. When a 70-d test is used to measure growth rate, feed conversion, and residual feed intake there is minimal loss in accuracy when weights are collected every 2 wk instead of weekly, but a further increase in the interval between weights to 5 wk caused a decline in the accuracy of the test. Therefore a 70-d test with cattle weighed every 2 wk seems to be optimal for measuring these traits in British breed cattle.

 

[Frankie]

You should send this info onto the BIF; they're still recommending 112 days. I'm sure they're very interested. :roll:

 

[KNERSIE]

growth tests here are all 84 days, whether intensive feedlot test or the semi extensive veld test. There is usually a 28 day adaption period before the intensive feedlot test.

 

[MikeC]

You should send this info onto the BIF; they're still recommending 112 days. I'm sure they're very interested. :roll:

They are not "recommending" any length. In case you didn't know........they disbanded the bull test committee. There's no one working on updating the bull test procedure pages.

 

[MikeC]

growth tests here are all 84 days, whether intensive feedlot test or the semi extensive veld test. There is usually a 28 day adaption period before the intensive feedlot test.

That's the way it is here, too. Plenty of time.

 

[Badlands]

It is actually more difficult to get a handle on gain that it is on intake.

The constraints for gain are what is keeping the test up at the 70 days. It doens't take that long to get a handle on intake.

So, the way they handle it is to take weights more often than just once a month.


I think the BIF may re-visit the feeding period issue, if not this year, then next MikeC. Your point is correct.



Badlands