High yielding cows require high quality diets to sustain milk yields and to minimise weight loss, metabolic disorders and fertility problems. Traditionally, these diets have contained fishmeal and soyabean meal, both widely regarded as good sources of high quality, digestible undegraded protein (DUP). However, there is increasing concern over the sustainability of world fish stocks and the BSE scare has increased public awareness to the extent that feeding animal protein to herbivores may become unacceptable in me future. This in turn has driven up the price of high quality imported vegetable proteins, such as soyabean meal. The aim of this study was to investigate whether fishmeal and soyabean meal could be replaced in the diet of high yielding cows, with protein sources grown in the UK

In a 12 week randomised block design experiment, 60 muciparous Holstein cows, on average 28 days calved at the start of the study, were fed total mixed rations based on grass silage and one of five protein mixtures. These were either 0.5 kg DM fishmeal + 0.7 kg DM soya + 2.5 kg DM rapeseed (PC), 1.3 kg DM soyabean + 2.3 kg DM rapeseed (PI), 3.8 kg DM lupins + 2.3 kg DM heat treated rapeseed (P2), 3.6 kg DM linseed + 1.4 kg DM rapeseed (P3) or 5.8 kg DM rapeseed (P4). Each diet was formulated to supply sufficient energy and metabolisable protein for maintenance + 43 litres and 0.75kg/d weight loss and to contain similiar levels of DUP (AFRC, 1993).