Effects of varying the energy and protein supply to dry cows on high-forage systems

Abstract

A total of 57 Holstein–Friesian dairy cows were used to investigate the effect of dry period energy and protein intake on performance in the early part of the subsequent lactation, when animals were given a single diet based on low-quality grass silage. Animals were balanced for parity across four dietary treatments for the last 5 weeks of gestation. Four dietary treatments were offered in factorial arrangement of high and low energy forages offered ad libitum with or without a high protein supplement. The two forage treatments were a ryegrass silage only and a mix of the same silage and barley straw (60:40 on a dry matter basis), and the protein supplement was 0.5 kg/day high protein maize gluten meal. Dry period diet forage intake was significantly higher for silage diets than for silage and straw mix diets but was not affected by the protein supplement. At 3 weeks before calving, N balance was significantly greater on the silage diets, and was significantly increased by the protein supplement. A period of 1 week before calving, there was no difference between treatments in body weight or body condition score. After calving, there were no residual effects of dry period treatment on feed intake, although milk and protein yields were significantly higher for the first month of lactation from animals previously offered the two silage-based diets; there was no effect of protein supplement. Subclinical ketosis in the animals may have limited all animals, production capabilities, which was lower than expected for the genetic potential of the animals, due to poor early lactation diets. It is concluded that improved dry period nutrition cannot compensate for poor early lactation diets to enable cows to achieve good production levels.