Effect of phytase and protease supplementation on growth performance, protein digestibility and gizzard and pancreas development of broilers fed with low-protein diets

Abstract

The objective was to evaluate the effect of a phytase, a protease and a combination of both on the productive performance, organ development and crude protein digestibility of broilers fed low-protein diets. The experiment involved five experimental diets: adequate crude protein level (Control), low crude protein (Low) and the low crude protein diet supplemented either with phytase (Low+F, 2800 FTU), protease (Low+P, 6500 Anson units/kg) and both enzymes simultaneously (Low+F+P), fed during the starter (7–21 d), grower (22–32 d) and finisher (33–37 d) phases. Overall, during the 7–37 d period, the average daily feed intake of the birds that consumed the diets containing phytase (Low+F and Low+F+P) and the Control was higher (P = 0.005) than that of the birds that consumed the Low and the Low+P diets. In addition, the average daily gain was highest for the Low+F and Control diets compared to the rest of the experimental diets (P = 0.02). No differences in feed conversion ratio were found between the birds for the 7–21, 22–32, 33–37 or the overall 7–37 d periods (P > 0.05). The apparent ileal digestibility of crude protein of the Low diet was lower than that of the rest of the diets (P = 0.01). During the 7–37 d period, the ENR of the birds that consumed the Low+F diet was highest (64.6%), followed by the Low+P (60.9%), Low+F+P (59.0%) and Low (58.5%) diets, with the lowest results obtained for the Control diet (54.7%, P < 0.05). Overall, the orthogonal contrasts indicate that including phytase in low-protein diets can be beneficial for the performance of the animals. The relative gizzard weight of the birds that consumed the control diets were lower than the rest of the low-protein diets (P = 0.007). In conclusion, whilst phytase supplementation improves the average daily feed intake, average daily gain, and the ENR of broilers fed low-protein diets, no effects were noticed for the supplementation of an exogenous protease or the combination of both enzymes.