The effects of dietary supplements of fish meal on the voluntary food intake of store lambs

Abstract

AbsstractThirty-six male and thirty-six female lambs (mean live weight 31·6 kg) were used to investigate the effect of fish-meal supplementation upon voluntary intake of NaOH-treated straw in a 3 × 3 factorial experiment with three levels of fish meal (0, 45 and 90 g/day) and three allowances of concentrate (57, 10·0 and 14·3 g/kg live weight) (experiment 1). The fish meal × concentrate allowance interaction was significant (P < 0·05) for straw dry matter (DM), total DM and metabolizable energy (ME) intake. Thus, as concentrate allowance increased, straw DM intake remained largely unchanged when fish meal was included in the diet whereas concentrate progressively substituted for straw DM intake when fish meal was not included in the diet. Increasing concentrate levels increased total DM intake linearly for all levels of fish meal but the rate of increase was positively associated with level of fish meal.In experiment 2, 24 castrated male lambs (mean live weight 40·7 kg) were used to measure apparent digestibilities and nitrogen (N) balance on four of the diets used in experiment 1. The overall effects of concentrate and fish-meal levels upon voluntary intake were similar to those found in experiment 1 but the interaction term was not significant either for intake or for the digestibility coefficients. Increasing fish-meal level increased apparent digestibility of DM, organic matter (OM) and aciddetergent fibre (ADF) (P < 0·01) while increasing concentrate allowance increased apparent digestibility of DM (P < 0·001) and OM (P < 0·01) but decreased that of ADF (F < 0·01). Nitrogen (N) retention was improved by the inclusion of fish meal in the diet (P < 0·001) and by high allowance of concentrate (P < 0·001).The voluntary intake response observed in experiment 1 could not be explained by the digestibility and N balance results obtained in experiment 2.