Broilers are nearing their genetic potential and nutritional strategies are the primary means to improve their performance. Improving raw material quality, especially soybean meal, could improve broiler performance, health and welfare. Inadequate processing of soybean meal leads to high residual anti-nutritional factors (ANF) which has a negative influence on broiler performance. High trypsin inhibitor content in low- quality soybean meal causes decreased protein digestion and absorption. The main aim of this study was to evaluate the optimal quality of soybean meal for commercial use to promote performance and welfare parameters of broiler chickens. Ten dietary treatments were formulated to the same nutritional specifications, but with different soybean meals that ranged from very high-quality (Treatment 1) to the lowest quality (Treatment 10). The quality of soybean meal was determined using Table 2.1 as target values for each soybean meal quality parameter. Soybean meal quality was evaluated using urease levels (pH change), TIA (trypsin inhibitor activity), Evonik TIA, KOH (potassium hydroxide solubility), Evonik KOH, Evonik PDI (protein dispersibility index) and Evonik PCI (processing conditions indicator). The treatment diets were fed to 4800 broilers that were randomly allocated to 80 pens, each with 60 birds and eight replicates. Over a 35-day growth trial, broiler performance, welfare and physiological traits were measured on a weekly basis.
Overall, improved performance was observed with higher-quality soybean meal outperforming the lower-quality soybean meal. High-quality soybean meal showed significantly better feed conversion ratio’s (FCR) and European performance efficiency factor (PEF) throughout the 35-day period, and significantly higher average daily gain (ADG) up until day 21. Bodyweight (BW), feed intake (FI) and mortality showed no significant differences irrespective of soybean meal quality. No significant differences were found in physiological traits namely: pancreas weight as a percentage of bodyweight, pancreas length to bodyweight ratio, gizzard and proventriculus weight as a percentage of bodyweight and gizzard erosion score, (PW%BW, PL:BW, GPV%BW, GE score) irrespective of soybean meal quality. High quality soybean meal showed lower incidence and lower severity of rapid feed passage (RFP) and foot pad dermatitis (FPD).
Evonik PCI and urease levels (pH change) showed the strongest correlation to broiler performance, health and welfare. This study suggests using soybean meal with the following quality parameters: urease levels of around 0.05, TIA levels of below 4mg/g, KOH levels of 78-80%, PDI levels of around 15 and PCI levels of around 11. The Evonik PCI and urease (pH change) analyses for soybean meal quality was found to be the easiest and cheapest method and can be recommended as the primary quality assays for commercial feed companies in the future.
Dissertation (BSc (Agric) Animal Science)--University of Pretoria, 2020.