The effect of formalin-treated soya bean meal upon the performance of lactating cows

Abstract

ABSTRACTFour concentrate mixtures were given with grass silage to 52 cows in early lactation in an 8-week randomized block production trial. A further eight cows were used to measure apparent digestibilities of the total diets in a double 4 × 4 Latin-square trial.The concentrates contained varied proportions of barley, soya bean meal (soya) and formaldehyde-treated soya bean meal (treated soya) together with fixed proportions of wheatfeed and molasses. Crude protein (CP) concentrations in the concentrate mixtures and sources of supplementary protein were 133 g/kg air-dry concentrate, soya (A); 130 g/kg, treated soya (B); 187 g/kg, soya (C); 169 g/kg, soya plus treated soya (D). In the production trial, 9 kg concentrates were given daily together with silage ad libitum, whilst in the digestibility trial the daily ration was 7·6 kg concentrates and 6·6 kg silage dry matter (DM). The silage contained 462 g DM per kg and 140 g CP per kg DM with an in vitro digestibility of DM of 0·7.The digestibilities of DM, organic matter and energy showed similar trends. Cows given treatments A and B had significantly lower digestibilities of energy than did those given treatments C and D.Nitrogen digestibility was highest for cows given treatment C and lowest for those given treatments A and B. Silage DM intake and live-weight change were unaffected by treatment during weeks 1 to 8, all treatment groups being in positive live-weight balance in this period.Milk yields during weeks 1 to 8 were 18·8 (A), 19·6 (B), 20·3 (C) and 20·7 (D) kg/day. Yields for cows given treatments C and D were significantly higher than those for cows given treatment A. There were no differences between treatments for any constituent of milk, but protein concentration in milk tended to be lower for cows given treatment D. During weeks 9 to 20, there were no significant residual effects of treatment upon milk yield or composition.Parallel regression analysis of milk yield and yields of milk constituents upon CP concentration in the concentrate indicated significant effects of CP concentration on yield of milk, milk fat, protein and lactose during weeks 1 to 8. When examined during weeks 1 to 20 the responses to increased CP concentration were non-significant. The analysis showed a significant positive milk-yield response to formaldehyde treatment during weeks 1 to 8 and 1 to 20. The response in lactose yield was also significant during weeks 1 to 8 and 1 to 20. There was a trend, though not significant, towards an increased milk-fat yield during weeks 1 to 8 for the formaldehyde treatment, whilst protein yield was unaffected.