Optimising the use of home-grown oilseeds and pulses as protein sources in feeds for table chickens

Abstract

The UK broiler industry depends upon imported soya. Other protein sources are used with caution because of risks to performance and litter quality, or of meat taint. A better understanding of the young chicken's intake and growth responses to these ingredients would enable a more flexible approach to their use in broiler diets and would assist UK arable growers in the development of home markets.

This project examined the broiler's intake and growth responses to increasing dietary concentrations of UK grown rapeseed meal (Study 1A), whole rapeseed (Study 1B), field peas (Study 2A) and field beans (Study 2B). In Study 3, the effects of increasing substitution rates of a soya protein mix (SPM) with a non-soya protein mix (NSPM), including UK grown rapeseed, peas and beans, on intake and growth responses were examined.

The protein mixes were calculated to have similar nutrient contents. In all studies the diets were formulated to be iso-energetic and iso-nitrogenous. The dietary treatments were applied separately to males and females and each diet x sex treatment combination was replicated. A controlled environment facility with 72 pens, each pen housing 22 day-old (age 0 days) chicks was used.

Rapeseed meal fed at up to 60 g/kg between day-old and 42 days of age did not depress performance. Broilers fed up to 160 g/kg rapeseed meal in the starter (0 to 21 days of age), followed by 0 g/kg rapeseed meal in the finisher (22 days to 42 days of age) performed similarly to broilers fed 0 g/kg to 42 days of age. Whole rapeseed fed at up to 100 g/kg linearly depressed weight gain, probably through reduced feed intake. The possibility that this was due to an antinutritional effect of glucosinolates could not be ruled out.

In broilers having atypically variable performance, peas could be fed up to 200 g/kg between day-old and 42 days of age, and field beans could be fed up to 160 g/kg from day-old to 21 days of age, followed by up to 120 g/kg from 22 days to 42 days of age, without depressing performance.

Broiler live weight at 42 days of age was reduced by feeding 0% and 100% SPM and maximised when feeding between about 50% and 75% SPM. Feed intakes to 42 days of age were similarly affected. Feed conversion efficiency (FCE) to 42 days of age was maximised by feeding 100% SPM. Birds fed 0% and 100% SPM were poorly feathered at 42 days of age. Although the possibility that antinutritional factors depressed performance in birds fed a low %SPM cannot be ruled out, it is thought that amino acid deficiencies and imbalances reduced performance at both 0% and 100% SPM. 

It is possible to substitute soya with a mix of UK proteinaceous ingredients to quite high levels (up to 75% substitution with the protein mix reported, which was rich in rapeseed meal (372.0 g/kg NSPM)) without reducing live weight. FCEs might be reduced however, and so this approach will depend on the relative prices of ingredients and the value of chicken meat.