Protein remains one of the most expensive nutrients to deliver in the pig diet. Theoretical benefits of supplementing protease enzymes include formulating diets with lower crude protein levels, using alternative raw materials with lower digestibility values, eliminating anti-nutritional factors, improving gut health, reduced protein fermentation in the hindgut and decreasing nitrogen excretion in manure and urine. Research studies to substantiate the theoretical advantages of protease enzyme supplementation in pig diets did not show the same repeatability found in broiler trials. The aim of this study was to determine if exogenous protease supplementation (Cibenza DP100) in grower and finisher pig rations would yield any improvement in production, slaughter and gut health parameters.
A completely randomised block design experiment was conducted at the University of Pretoria's experimental farm. One hundred and seventy four male pigs (from Topigs 40 sow line) of 30 kg (+/- 7 kg) were allocated to 4 dietary treatments (positive control; negative control; negative control + 250 mg/kg Cibenza DP100; Negative control + 500 mg/kg Cibenza DP100). The feeding programme of the trial consisted of 3 phases (grower 1, grower 2 and finisher rations). Production parameters (average daily gain, feed intake, feed conversion ratio, body weight and backfat thickness) were measured in each phase. Slaughter parameters (carcass weight, carcass length) and gut health parameters (villi length, crypt depth, ammonia) were quantified for each group of pigs slaughtered at the end of the second grower phase (115 days of age) and the finisher phase (137 days of age).
Significant effects were observed with Cibenza DP100 protease enzyme supplementation after the second grower phase on body weight, body weight gains, feed conversion ratio and reduced backfat thickness. The same trend of increased body weight and body weight gains, reduced feed conversion ratio and reduced backfat thickness was observed when considering the overall grower phase (70-115 days of age). Significant differences were found between the negative control diet and supplemented diets, in warm carcass mass, cold carcass mass and carcass length after the finisher phase. Diets supplemented with 250 mg/kg performed equally well compared to diets supplemented with 500 mg/kg protease enzyme. Data to demonstrate significant effects on gut health parameters were not conclusive.
The results of this trial concluded that protease supplemented at 250 mg/kg to diets of grower and finisher pigs, between 96 and 137 days of age, could reduce backfat thickness, improve feed conversion ratio and average daily gain in growing pigs and improve carcass mass at slaughter in finishing pigs. These enzymes should especially be considered under circumstances where underprocessed soymeal is used or alternative protein sources with lower digestibility are included in the diet.
Dissertation (MSc (Agric))--University of Pretoria, 2017.