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Effect of Previous Ration on Lactation Response to Substituting Corn for Alfalfa According to Net Energy and Total Digestible Nutrient Systems of Estimation¹

Animal Industries Department, Storrs (Conn.) Agricultural Experiment Station, and Statistics Department, University of Connecticut, Storrs

H. L. Lucas, Jr.

Experimental Statistics Department, North Carolina State College, Raleigh

L. A. Moore

Dairy Husbandry Research Branch, USDA, Beltsville, Md.

ABSTRACT

The lactation response to the substitution of 10 lb. alfalfa with 7.0 or 5.7 lb. corn based, respectively, on the TDN or NE system was studied, in a double-reversal trial, with 24 cows previously fed equivalent therms NE per unit of live weight from either of two basal rations: 100% alfalfa or 80% alfalfa plus 20% corn. Basing the substitution on the TDN system resulted in greater energy intake than the NE system, 0.99 therm and 0.94 lb. TDN. Across both basal rations, the TDN basis of substitution resulted in significant increases in average daily milk production, 0.89 lb. milk, 0.025 lb. fat, and 0.73 lb. FCM, and a 0.10 decrease in the fat percentage, over the NE basis. Assessing the advantage of the TDN basis of substitution for each basal ration fed, the cows previously fed the 80% alfalfa plus 20% corn basal ration failed to respond; whereas, those previously fed the 100% alfalfa basal showed the following significant advantages: milk 1.56 lb., fat 0.051 lb., and FCM 1.39 lb. When 10 lb. alfalfa were replaced with equivalent NE from corn, milk production increased 1.55 lb. and FCM 0.94 lb. for the 100% alfalfa basal. No significant changes for the 80% alfalfa plus 20% corn basal were observed and across both basal rations, a slight increase in pounds of milk.

¹ This study was made in part with funds provided by the Research and Marketing Act of 1946, through a contract between the Storrs (Conn.) Agricultural Experiment Station and the Dairy Husbandry Research Branch of the USDA, as well as with funds provided by the Chas. M. Cox Co., Boston, Massachusetts. The data are part of a thesis presented by the senior author to the Graduate School, University of Connecticut, in partial fulfillment of the requirements of the M.S. degree.

² Present address: Gillette Safety Razor Blade Co., Boston, Mass.