Biorefined grass-clover as protein source for organic broilers: Effect on feed intake, growth, and meat fatty acid profile

The composition of protein extracted from organic grass-clover during biorefining was investigated as were the effects on growth performance and tissue fatty acid composition of substituting traditional feed ingredients with grass-clover protein for organic broilers. The extracted grass-clover protein had a crude protein content of 362 g/kg and a balanced amino acid composition with a methionine content superior to the content in soybean meal. The dietary fiber content was 324 g/kg dry matter with a major fraction being acid insoluble residues (klason lignin). The majority of the fatty acids was constituted by polyunsaturated fatty acids (PUFA), more specific alpha-linolenic acid. A total of 640 one-day old Color Yield chickens were fed diets containing 0%, 8%, 16% or 24 % grass-clover protein until slaughter. The average daily feed intake was not affected by addition of grass clover protein at the three time intervals registered, but overall intake was slightly reduced in broilers on 24% grass-clover protein (106 g/d) compared to the control (114 g/d). The slaughter weight was lower in the broilers receiving 16% and 24% grass clover (2188 g and 2017 g) compared to the control (2367 g), primarily a consequence of depressed weight gain in the young broilers. The feed conversion ratio was consequently higher in these two groups (2.45 and 2.55 vs 2.29). The coverage of essential amino acids was high, and the depressed weight was suggested to be a result of the high inclusion of acid insoluble residues, expected to be present in the extracted grass-clover protein due to endogenous plant enzyme activity. The content of fatty acids in the breast meat, liver and fat tissue reflected the fatty acid composition of the grass-clover protein, where increased dietary addition resulted in increased content of the n-3 fatty acid alpha-linolenic acid in the meat and tissue. In addition of increased content of nutritionally favorable n-3 PUFA in tissues, addition of grass-clover to the diets of organic broilers also increases the need for antioxidants. The study demonstrates extraction of high quality protein from organic grass-clover with a balanced amino acid composition supplying the feed with the commonly limiting sulphur-containing amino acids. Moreover, the study reports great potential in using grass-clover as protein source for organic broilers but also that process optimizations are needed to reduce enzyme activity leading to quality-impairing complex formations