EFFECT OF ENERGY-INTAKE DURING LATE PREGNANCY ON THE PRODUCTION FROM 2 GENOTYPES OF SUCKLER COW

The effect of energy intake during the final 12 weeks of pregnancy on the production of 59 Blue Grey (Shorthorn × Galloway) (BG) and 56 Hereford × Friesian (HF) cows inseminated with Hereford semen was studied over 2 years. Energy intakes ranged from 34·3 to 78·2 and from 30·3 to 58·2 MJ ME/day for a 500 kg cow in the 2 years respectively. The cows were fed ad libitum for 22 weeks after calving. Plasma 3-hydroxybutyrate concentrations in late pregnancy were closely and inversely related to energy intake. In the first year there was a curvilinear relationship between calf birth weight and pre partum energy intake, maximum birth weights occurring at an intake of about 58 MJ ME/day. Over the lower range of intakes in the second year the relationship was linear and positive; the difference in calf birth weights between extreme levels of intake was 15%. Pre partum energy intake had a small inverse effect on voluntary food intake some 16 to 20 weeks after calving, and a large inverse effect on cow live-weight change throughout lactation, but had no measurable effect on milk production or calf growth rate. HF cows gave birth to heavier calves which grew more quickly in the 2nd year, had higher voluntary food intakes during lactation, and produced more milk than did the BG cows. © 1979, British Society of Animal Science. All rights reserved.