723. The effect of level of concentrate feeding and type of roughage on milk production

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Abstract
1. In a short-term winter feeding trial using eight Ayrshire cows, a concentrate with a nominal starch equivalent of 68 was fed at 2 lb. and 4 lb./gal. of milk with either 16 lb. hay or 16 lb. dried grass. Silage (40 lb. per day) was also fed.2. The weight of dry matter from grass products eaten per day was similar on all four treatments. Differences in total daily dry-matter consumption were very largely attributable to differences in the consumption of concentrate dry matter.3. The daily dry-matter consumption as a percentage of live weight increased from 2·5 on the rations that included hay and 2 lb. concentrates per gal. to 3·2 on the rations that included dried grass and 4 lb. concentrates per gal.4. Milk yield was significantly increased from an average of 33·5 to 37·3 lb./day when the amount of concentrates fed increased from 2 to 4 lb./gal. and also significantly increased from 33·9 to 36·9 lb./day when dried grass was fed in place of hay.5. There was an increase of 0·9 lb. milk for each 1 lb. increase of starch equivalent plus 0·2 lb. digestible crude protein intake as a result of either increasing the rate of concentrate feeding, or of feeding dried grass instead of hay.6. The fat content of the milk was similar on all four rations, whereas the solids-not-fat varied from 8·42% on the ration that included hay +2 lb. concentrates/gal, to 8·59% on the ration that included dried grass +4 1b. concentrates/gal. This change in S.N.F. was almost entirely in the protein fraction of the milk.7. There was a gradation in live-weight change from -0·74 lb./day on the hay +2 lb. concentrates/gal, to +0·34 lb./day on the dried grass +4 lb. concentrates/gal.8. After a consideration of profit margins, milk quality and live-weight changes it was concluded that both treatments B (dried grass +2 lb./gal.) and C (hay +4 lb./gal.) gave optimum and almost identical results.

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