Published online by Cambridge University Press: 02 September 2010
In the national pig progeny test stations one diet is given up to about 55 kg live weight and another, with less protein, is given from then until slaughter. These diets were compared with four ‘single’ diets, similar in digestible-energy content, but containing either 15·6, 17·4, 18·7 or 22·1% crude protein, and each given unchanged from 18 to 93 kg live weight. There were twenty groups of one castrate and one gilt on each treatment.
Pigs given the lowest protein levels had the poorest growth rates and feed conversion efficiency up to 57 kg live weight, but the best from 57 to 93 kg. Hence there were no differences in overall feed efficiency, and overall growth rate was only slightly less with the lowest protein level than with other treatments.
Carcass leanness rose with protein level in the ‘single’ diets over the range 15·6·18·7% crude protein, but a further increase to 22·1% reduced leanness.
Pigs given the progeny test diets had carcasses intermediate in composition to those of pigs on the ‘single’ diets with 17·4% and 18·7% protein.