A COW'S MILK YIELD.

Hauraki Plains Gazette, Volume XXXVI, Issue 4870, 28 August 1925, Page 1

A COW'S MILK YIELD.

VARIATION WITH AGE. / RESULTS OF TESTS. Dairy farmers arc fully aware that a cow's yield varies with her age ; but in comparing animals of different ages it is important to know not only exactly what thfe variation is, but also its- extent. The effect of age on milk production has been worked out statistically by s'eVeral workers from large masses of data ; and although, of course, their results are not exactly the same, they arc in very close agreement. Dr. Pearl, in America, stated that ■“a. cow’s yield increases at a decreasing rate from the age of two years up to about eight years, lend then decreases at an increasing rate” ; and with that everyone will agree.

In working out the variation, however, two points must be taken into account, because, although intrinsically they may be of little interest, they will affect the result. The flns.t is that in practice the worst cows are being continually weeded out—that is, as soon as the farmer is ifuite satisfied that a particular animal will never make a good milker (according to what he considers an economical limit) she is fattened and sent to the butcher. Consequently we must only consider the same individuals throughout, as otherwise the yields we get for the later ages will only be those of selected, and hence superior, animals.

• The second point fe that first-'calv-ers are often left unserved for a family long time, in order to get better growth ; and consequently thej have

a longer lactation. With the next few calves this interval between calving. and the next service is shorter ; until after about the fifth or sixth calf it gets ocnsider'ably longer again—speaking, of course, of averages. It may be that in early life growth, and jn later life the onset of sensility, leaves less vitality for reproduction, but whatever the cause, this fact will affect our results and must be allowed for.