INTERACTIONS OF ENERGY LEVELS OFFERED TO HOLSTEIN COWS PREPARTUM AND POSTPARTUM .I. PRODUCTION RESPONSES AND BLOOD COMPOSITION CHANGES

Digestible energy levels of 115% (low-prepartum) and 160% (high-prepartum) of maintenance requirements were provided for groups of 32 Holstein cows during the last six to eight weeks of gestation. All 64 cows were factorially assigned to two energy levels postpartum. One group was fed concentrates sufficient to maintain body weight through a complete lactation (high-postpartum). The second group was fed according to the energy requirements of lactation recommended by the National Research Council in 1958 (low-postpartum). Unadjusted 305-day yields of milk, fat, protein, and lactose plus minerals were 5,600, 193.6, 190.4, 298.2 (low-prepartum-low-postpartum); 7,002, 223.0, 233.6, 367.2 (low-prepartum-high-postpartum); 6,223, 210.9, 208.6, 327.7 (high-prepartum-low-postpartum); 6,534, 210.9, 220.9, 337.2 kg (high-prepartum-high-postpartum), respectively. Prepartum energy levels did not significantly (P < .05) affect milk or milk component yields, but the higher postpartum level increased (P < .05) production of milk, protein, and lactose without affecting (P < .05) percentages of milk components. Oleic acid was increased (P < .05) in milk (Weeks 3 to 4) from cows receiving the high prepartum level and palmitic acid was significantly higher (P < .05) from cows offered the high postpartum level (Weeks 15 to 16). Clinical ketosis and elevated blood ketones were more prevalent (P < .05) in cows offered the high prepartum level, and were most pronounced in the high pre-low-postpartum sequence. An average of 1.86 megacal of digestible energy was required per kilogram of solids-corrected milk to maintain a relatively constant body weight through a complete lactation. © 1969, American Dairy Science Association. All rights reserved.