STRONGLY INHERITED

Waikato Independent, Volume XLV, Issue 6233, 2 May 1949, Page 3

STRONGLY INHERITED

| PERCENTAGE OF BUTTERFAT i - , EXCERPTS FROM ADDRESS 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% of the total butterfat production differences of their dams, but for butterfat test the inheritance value was approxiI mately 45%. 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 sire being the same for each group of daughters). The difference was upper half according to butterfat production. The daughters from the lower half differed from the daughters in the upper half by approximately 15% 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 50% of difference between Jhe two groups of dams (the actually 46%; again bearing out previous work showing evidence of high heritability of butterfat percentage. These inheritance values are baeed on only one side—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% for total butterfat production and 80% to 90% for butterfat test. (Excerpt from address by A. H. Ward, Supervisor of Herd Improvement, New Zealand Dairy Board, as appearing in Dairyfarming Annual 1948.)