MINIMUM BUTTERFAT YIELD.

Otaki Mail, Volume 26, 30 June 1919, Page 4

MINIMUM BUTTERFAT YIELD.

i The question of the changes in the c composition ;oi>milk with successive plantation periods'- and particularly the ' / question relative to the percentage of r fat in the milk of the heifer, has been jof great practical importance to the dairyman, as a possible index of what J may be expected from mature animals. The conclusions so far reached from • data compiled by several investigators I have not been entirely uniform. The i following particulars taken from the records of the University of Missouri dairy herd, composed of purebred animals of the .Jersey, Holstein, Ayrshire, and Shorthorn breeds, provide interesting data. These data show that the percentage of fat in the milk of Jersey cows atains its maximum with respect to the average for the entire lactation period during any one of the first three periods, but the chances appear to be greater that this will be attained in the second or third period rather than the first. Holstein cows, on the contrary, al- ■ most invariably show the highest average percentage of fat for the lactation period dining the first period, and the conclusion seems justified that this is a breed eharactistie. Ayrshire cows more frequently show a higher average lactation test during the first: than during subsequent periods but less frequently than in the case of Holstein cows. ' The variations in the average percentage of fat among the first few J lactation periods are not sufficiently ' great to be of much practical importance, but the gradual decline in average test accumulates to a figure of considerable importance as the number of : lactation periods becomes greater, j The fact that certain of the animals iof the Jersey and Holstein breeds whose records are included in the data, comprised an experiment to determine Jthe influence of the plane of nutrition during growth and age of first calving upon the dairy qualities of cows, suggested that the two factors may have contributed to the difference in the character of the data from the two breeds. The data concerning the influence of the plane of nutrition during growth, indicate that this factor may be of importance in connection withtlie average fat test for the .first lactation period. The light-fed Jerseys showed both a lower average test in the first, lactation period and also a less frequent tendency for this period to | show the highest test, while the heavyI fed Jerseys showed exactly the oppo- ] site results.. The strong breed tendency j for the Hohjteins to show a higher aver- ’ ago test in the first lactation period than in any subsequent period was also materially diminished by light feeding during the growth of the animals. ft. must also be considered that the light feeding of the animals for both breeds was by no means extreme, although it was widely different front the heavy feeding ' carried out with the other animals in the experiment.