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Responses of Milking Cows to Amounts of Concentrate in Rations¹

Department of Animal Science, University of Minnesota, St. Paul 55108

ABSTRACT

Eight groups of cows were used to evaluate effects of hay quality (early or late cut alfalfa hay fed in combination with corn silage, 1:1.1) and different quantities of concentrate during 230 lactations. Rations were arranged into four pairs; one of each pair included early hay and the other late hay and 507 kg more concentrate per lactation. The increment of concentrates per cow between ration pairs was 350 kg per lactation. Daily amounts of concentrate were independent of milk production and forage consumption but followed distribution patterns similar to the general pattern of milk production expected. Rations were formulated to be adequate in protein. Cows consumed forage to appetite in weighed quantities. Milk produced was measured daily, body weight weekly, milk fat and solids-not-fat contents monthly, and feed and ort analysis every 14 days. Data were compiled for 22 14-day periods.

When rations contained similar percents of crude fiber, those including more concentrate (they also included the lower quality alfalfa hay) allowed cows to consume similar amounts of dry matter and produce more milk than cows fed rations with higher quality hay and less amounts of concentrate.

Each additional kilogram of concentrate dry matter consumed resulted in .58 or .39 kg more 4% fat-corrected milk and .72 or .85 kg less forage dry matter consumed for cows fed rations including early or late alfalfa hay.

Forage intake was affected linearly and quadratically by body weight and interacted with cow's producing ability, increasing with producing ability above mean producing ability and decreasing below the mean. Milk production increased with increased body weight but at a decreasing rate as weight increased.

¹ Scientific Journal Series, Paper No. 11280, Minnesota Agricultural Experiment Station, St. Paul 55108.

² Casilla 124, San Javier, Chile.