Prediction of responses of indigenous Boschveld chickens to probiotic-yeast additive levels using a quadratic optimisation model

This experiment was performed to determine the nutrient content of yeast ( Saccharomyces cerevisiae ) and effect on carcass characteristics, relative internal organ weights, digesta pH, and lengths and weights of the different segments of the gastrointestinal tract (GIT) of indigenous Boschveld chickens. Six hundred-day-old unsexed Boschveld chicks were divided into six groups of 100 birds with each group replicated five times. Birds were fed broiler starter from 1 to 49 days and grower diet from 50 to 91 days. Each group was allotted to commercial broiler mash diet supplemented with yeast designated 0 g kg −1 feed (T0), 2.5 g kg −1 feed (T1), 5.0 g kg −1 feed (T2), 7.5 g kg −1 feed (T3), 10.0 g kg −1 feed (T4) and 12.5 g kg −1 feed (T5) in a completely randomised design. Proximate composition of yeast was assessed using the standard method. Live weight, carcass characteristics, organ weights, digesta pH and the lengths and weights of the different segments of the digestive tract were measured and analysed statistically. Probiotic-yeast levels for optimal productivity were determined using a quadratic optimisation model. Results revealed that probiotic-yeast is rich in crude protein (496.0 g kg −1 ), ash (61.60 g kg −1 ) and moderate in crude fibre (29.0 g kg −1 ). Birds in groups fed with diets supplemented with yeast at 7.5 and 10.0 g kg −1 feed gave the best ( p