BUTTERFAT TEST IS INHERITED BY INDIVIDUAL COWS
(By A. H. Ward, Supervisor of Herd Improvement, N.Z. Dairy Board) A particular level of butterfat test for a complete lactation is a strong characteristic of any individual cow. (It is important to distinguish in all these comparisons the essential difference between the seasonal variation in butterfat test “within” a lactation, as compared with the average butterfat test for a complete lactation—it is to this latter only that this comment refers). That, alone, is good evidence that butterfat test is strOngly inherited, but, fortunately, more direct evidence is available from the results of sire surveys. From these it was found that the daughters inherited only between 15 and 20 per cent of the total butterfat production differences of their dams, but for butterfat test the inheritance value was approximately 45 per cent. An example will make this clearer.
A sample of 72 final surveys containing at least 14. daughter-dam pairs in each survey was taken, and the dams divided into a lower and an upper half according to butterfat production. The daughters from the lower half differed from the daughters in the upper half by approximately 15 per cent of the butterfat difference between the two groups of dams. On the other hand, whilst the two groups of dams differed by .21 in the butterfat test, the two groups of daughters differed by 0.10. If butterfat test were completely inherited, the difference between the two groups of daughters should have been about 50 per cent of the difference between the two groups of dams (the sire being the same for each group of daughters). The difference was actually 46 per cent; again bearing out previous work showing evidence of high heritability of butterfat percentage.
These inheritance values are based on only one sidy—or one half—of the pedigree, i.e., the female side; and if the influence of the male is approximately equal (as we believe), the total inheritance Values become 30 to 40 per cent for total butterfat production and 80 per cent to 90 per cent for butterfat test.
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Bay of Plenty Beacon, Volume 13, Issue 94, 1 June 1949, Page 3
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346BUTTERFAT TEST IS INHERITED BY INDIVIDUAL COWS Bay of Plenty Beacon, Volume 13, Issue 94, 1 June 1949, Page 3
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