Influence of Feed upon the Composition of Milk. II. Low versus High Fat Rations

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Abstract
Two lots of cows each (3 Holstein and 2 Jersey) were selected for a 12-week mild weather switch-back feeding trial. Ration B with no added fat served as control; Ration M contained 6% Marcol B-75, a commercial product consisting primarily of the methyl ester of cottonseed foots, whereas Ration T contained 6% stabilized prime tallow. Milk from both breeds produced on Ration T was significantly higher in per cent fat, but was significantly lower in both per cent solids-not-fat (S. N. F.) and S. N. F.-lactose with the Holsteins when compared with Ration B. Milk from Holsteins produced on Ration M was significantly lower in both per cent S. N. F. and lactose when compared with Ration B. Also 75% of all Holstein milk samples produced on Ration M were below 3.25% fat, as compared with 39% from Ration B and 9% from Ration T. The per cent of all milk samples with less than 8% S. N. F. was: 70, 61 and 43 for Ration M, T and B respectively. Two other lots of cows (5 Holstein and 5 Jersey) when placed on a 13-week mild weather continuous feeding trial on control Ration H (similar to Ration B above) and Ration T respectively, produced milk on Ration T significantly lower, in per cent fat, S. N. F. and S. N. F.-lactose with the Holsteins, but a milk fat significantly higher in per cent alcohol-soluble portion for the Jersey as compared with Ration H.