Dry Matter Intake in Dairy Heifers. 1. Factors Affecting Intake of Heifers under Intensive Management

Abstract

Effects of body weight, body weight gain, ration acid detergent fiber, neutral detergent fiber, bulk density, and ambient temperature on intake of dry matter and digestible energy were examined using 118 Holstein heifers weighing 100 to 400 kg. Animals grouped according to body weight (100, 200, 300 kg) were fed total mixed rations (corn silage, ground hay, high moisture corn, soybean meal) once daily for 28 d. Rations were balanced to mean body weight according to National Research Council recommendations for protein, vitamins, and minerals and to 85, 95, 105, and 115% of recommended total digestible nutrients. Second order polynomial regression of ration fiber content and density explained 20 and 21% of variation in dry matter intake and 46 and 45% of digestible energy intake. Dry matter intake increased linearly with increasing body weight and gain. Dry matter intake correlated −.42, −.42, and .39 with acid detergent fiber, neutral detergent fiber, and bulk density when neutral detergent fiber was greater than 42% of dry matter and .03, −.03, and −.02 when less than 42%. Predictions of dry matter intake should include body weight, gain, and polynomial terms of ration fiber or ration energy to account for changing metabolic systems controlling intake. © 1986, American Dairy Science Association. All rights reserved.