Protein supplementation of rations based on whey for growing pigs

Abstract

An experiment is described in which energy and nitrogen digestibility and nitrogen retention were determined when pigs weighing 25, 40, and 55 kg were fed diets comprising meal mixtures of varying protein content (12 to 18%) provided at the constant daily rate of either l1/2 or 21/2 lb/pig as supplements to lactic casein whey. A total of 14 castrated male pigs of Large White × Landrace origin were involved, 2 being allocated to each treatment. Differences between the apparent digestibility of energy of diets containing quite widely varying proportions of barley meal, buttermilk powder, and whey were in accordance with the respective total digestible nutrient contents of these three foods. Pigs fed 21/2 lb meal daily, compared with those receiving 11/2, consumed slightly but significantly less apparent digestible nitrogen per 5 days (p < 0.10) and yet retained both a greater weight and percentage of nitrogen per 5 days (p < 0.10). pie apparent digestible energy intakes of the two groups were almost identical. As the proportion of protein concentrate increased in the meal supplements fed at either the higher or lower rate, nitrogen retention (g/5 days and g/5 days/kg live weight) improved considerably, but differences between treatment means failed to reach significance (p > 0.10). Apparent digestibility of energy increased linearly as the pigs aged (p < 0.005); nitrogen retention (g/5 days) was similar for pigs weighing 25, 40, or 55 kg, and consequently both the percentage of nitrogen retained and the weight retained/kg/5 days decreased linearly as the experiment progressed (p < 0.005).