MILK YIELD AND AGE

Wanganui Chronicle, Volume LXXXII, Issue 19368, 27 July 1925, Page 8

MILK YIELD AND AGE

RESULTS OF TESTS. Dairy farmers are fully aware that U cow’s yield varies with her age; but. in comparing animals of different ages, it is important to know not only exactly what this variation is, but also its extent. The effect of age on milk production has been worked out statistically by several workers from large masses of data; and although. of course, their results are not. exactly the same, they arc in very close agreement. Dr. Peal, in America, stated thiat “a cow's yield increases at a decreasing rate from the age of two years up to about eight years, '.ind then decreases at an increasing rate;” and with that everyone will agree. In working out the variation, however, two points must be taken into laccount because, although intrinsically they may be of little interest, they will effect the result. The first is that in practice the worst cows are being continually weeded out —that is, as soon as the farmer is quite satisfied that a particular animal will never make a good milker (according to what he considers an economical limit) she is fattened kind sent to the butcher. Consequently wo must only consider the same individuals throughout, as otherwise the yields wo get for the later ages will be those of seclctcd, and hence superior animals. The second point is that first-calvers arc often left unserved for a fairly long time, in order to get better growth; land consequently they 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 considerably longer again—speak-, ing, of course, of Averages. It may be that in early life growth, and in later life the onset of senility, leave less vitality for reproduction, but what ever the cause, this fact will affect our results and must he allowed for.