COMPARISON OF GROWTH-PERFORMANCE AND NUTRIENT RETENTION OF WEANER PIGS GIVEN DIETS BASED ON CASEIN, FREE AMINO-ACIDS OR CONVENTIONAL PROTEINS

In two experiments the potential value of diets based on casein or fre e amino acids (FAA) for amino acid utilization experiments were examin ed, In Expt 1 the optimum dietary electrolyte balance (dEB) for a case in-based diet was estimated by supplemention with 10 or 20 g NaHCO3/kg , to produce diets containing 64, 183 or 302 mmol/kg., In addition, pi glet growth performance and efficiency of nutrient deposition of pigle ts given the casein diets were compared with two multiple protein sour ce diets; Supercreep, a commercial multiple protein source diet or CFS (casein-fish-soyabean-sugar) or a FAA-based diet. Expt 2 was designed to compare piglet response to FAA diet stored at -15 degrees with twi ce daily feeding, with FAA diet stored at ambient temperature (13-30 d egrees) and offered ad libitum. A CFS diet was used as a positive cont rol and the experiment was conducted over the 10-20 kg growth phase, E xpt 1 used forty-eight piglets weaned at 20-22 d of age and allocated to one of six treatments formulated to contain at least 0.84 g lysine/ MJ digestible energy in a randomized block design, Piglets given the C FS and Supercreep diets produced superior growth rates (518, 491 g/d) to those given a FAA diet (353 g/d) or casein diet containing 0, 10 or 20 g NaHCO3/kg respectively (365, 417, 390 g/d) between 5 and 20 kg l ive weight, Piglets given the casein and FAA diets had higher amino ac id digestibilities than those given the Supercreep and CFS diets, The increase in the dEB of the casein diet from 64 to 183 mmol/kg improved piglet growth performance between 5 and 20 kg by 14 %. All piglets gi ven casein diets had similar ileal and faecal digestibilities, empty-b ody compositions, nutrient deposition rates and retention ratios, The results of Expt 2 showed that there was no beneficial effect on piglet performance of storing the FAA diet at -15 degrees and feeding twice daily, Based on the results of these two experiments, neither the case in (0, 10, 20 g NaHCO3/kg) nor FAA diets were suitable for estimating amino acid utilization by the piglet, There remain unidentified factor s which limit the growth performance off piglets given the casein and FAA diets.