PROBLEM OF TEMPORARY STERILITY OF DAIRY COWS IS IMPORTANT SAYS HERD RECORDING OFFICER

Bay of Plenty Beacon, Volume 13, Issue 31, 10 December 1948, Page 5

PROBLEM OF TEMPORARY STERILITY OF DAIRY COWS IS IMPORTANT SAYS HERD RECORDING OFFICER

(By W. H. Mandeno, Consulting Officer, Herd Recording Department, New Zealand Dairy Board) During November the bull has for sterility, and many bulls reserved at the Bull Sales are disposed of to worried owners of apparently sterile sires—but suspicion moves to the cow in December. Most cows are in calf, but a few return again and again

It is perhaps consoling to know - that this is a common occurrence throughout New Zealand.' Where cows calve at all times of the year as in America and Europe, the temporary sterility dn cows is not so important as in our country where, for maximum economic production, the cows should all calve within ■ two months during the early spring. The latest report of the Herd Re- < cording Department of the New Zealand Dairy Board * (which is available on application from the ; Herd Improvement Association) contains detail of interest t regarding this problem. On a survey embracing over 20,P00 cows through- ■ out the country it was found that ' 7 per cent remained empty at the ■ end of the season. Fertile Cows Fertile cows are not, however, all •successfully mated at the beginning of the season. The percentages of these fertile cows holding to first, second, third and fourth or later .services were 68, 21, 7, 4 respectively. This is an average picture and is made up of course, by some herds having a particularly successful mating and by others which caused their owners a great deal of <concern. It does, however, show that it is unusual to have no cows : returning late in December and .January. The subsequent history of these •empfy cows is worthy of comment. Of those not culled, four out of five were successfully mated in the following season. This confirms other opinions that permanent sterility is not nearly so serious a problem as temporary infertility. Further it has been shown that over 75 per •cent of sterility is due to abnormalities of the cows and that bulls generally maintain a reasonable level' of fertility till nine years of age. Late Cal vers If there are to be some cows not in calf by Neyr Year their probable performance on late calving should he considered. It has been shown that cows calving after September " 15 lose about 20. per cent of normal production. This is due to the fact that there is only a short period whilst the impulse to secrete milk is strongest before the grass dries up and in the autumn the tendency (actuated by usual feed conditions) is to go dry about the same time as the majority of early calvers. ■Other considerations-make the late calves rather a nuisance. Even under good conditions late calves are difficult to rear and are often too small for mating the next year. It is also very difficult to work back late calvers to get them in early in subsequent years. For these reasons a commonly adopted principle is that of stopping bull service at Christmas of New Year. -This will mean empty cows on hand.. Long Periods Of Milking It is reported from Alaska that •cows are bought in milk from Canada and are maintained for three -years at an economnc level of milk production. As conditions of housing and feeding are not similar to those in New Zealand such a practice is not used here. It does, however, show that cows can milk for long periods—if they are cared for without the annual stimulus of calving. Thus it is recommended that good cows are carried through -the winter on good feed and they will probably produce economically in the second season. Under normal conditions the reduced production of a 4001bs fat cow may be 150 lbs fat, but this drop is considerably reduced by feeding of good grass in the winter. There are of •course many cases where cows have •shown no appreciable reduction in the second year of lactation. For pig enthusiasts the skim milk from •carry-overs is of great value for •early sows and weaners. Where there is a demand in the autumn for winter milkers it often pays to dispose pf these cows after mating to calve in March and April where high prices are offered. Producers Below Average

at the freezing works were actually in calf although some were in season within a month of slaughter. The practice of spaying cull cows to save trouble with bulls and hasten fattening is not recommended by members of the veterinary profession. Such animals would complicate the winter feed position by the tendency of farmers to hold them for the high prices ruling late in winter. Although the operation is comparatively simple and casualties over large numbers are not large there is the chance of losing, by blood poisoning, all those done on one farm. Disposal Of Bulls From now on there is a tendency to dispose' of the older and slower bulls to save carrying them through the year. This generally cannot be too strongly deprecated. Until New Zealand farmers as a whole realise the value of proven bulls as the foundation for their herds there can be but little hope for better herds. Extension of such services as Artificial Insemination depend on a supply of proven bulls. Once the technique has been established ready for commercial expansion it will rest with the farmers themselves to provide the necessary bulls.

Producers below the herd average need a lot of redeeming features to prevent their sale to the butcher when the monthly test sheets show that available feed should be utilised only by the bet--ter cows. An interesting feature of a study of Dr McMeekan (whose successful application of modern grassland practice has recently been featured in the N.Z. Herald) of cows -sold to the works as “empty” was that 23 per cent of those examined