INTERACTIONS OF ENERGY LEVELS OFFERED TO HOLSTEIN COWS PREPARTUM AND POSTPARTUM .2. REPRODUCTIVE PERFORMANCE

Thirty-two cows were provided with 115% of their maintenance digestible energy requirements (low-prepartum) during the last six to eight weeks of gestation for comparisons with 32 cows fed 160% of their maintenance energy needs (high-prepartum). The 64 cows were factorially assigned to two energy levels postpartum. One group was fed alfalfa hay at 2% of body weight and enough concentrates to maintain relatively constant body weights through a complete lactation (high-postpartum). A second group was fed alfalfa hay at 2% of body weight and enough concentrates to satisfy the National Research Council energy recommendations of 1958 (low post-partum). Average birth weights of 43.6 kg (low-prepartum), and 42.9 kg (high-prepartum) were not significantly different (P < .05). The percentages of the cows’ uteri which had completely involuted by 45 days postpartum were 94 (low-prepartum-low-postpartum), 75 (low-prepartum-high-postpartum), 75 (high-prepartum-low-postpartum), and 88 (high-prepartum-high-postpartum). Days from calving to first estrus and calving intervals were 32.0, 390.0 (low-prepartum-low-postpartum); 46.9, 385.5 (low prepartum-high-postpartum); 47.8, 378.0 (high-prepartum-low-postpartum); and 42.9, 379.0 (high-prepartum-high-postpartum), respectively. Services required per conception averaged 2.1 (low-prepartum-low-postpartum), 1.6 (low-prepartum-high-postpartum), 1.9 (high-prepartum-low-postpartum), and 1.5 (high-prepartum-high-postpartum). None of the above differences was significant (P<.05). © 1969, American Dairy Science Association. All rights reserved.