Effects of dietary prickly pear (opuntia ficus indica l.) seed cake meal inclusion in a maize-cowpea diet on ROSS 308 broiler performance and carcass characteristics

Abstract

The aim of the study was to investigate the effects of graded inclusion of prickly pear oil seed cake (PPSC) in sprouted cowpea-maize diets for broilers. Diluent (0%PPSC) sprouted cowpea-maize grower and finisher diets, and the respective (10% and 12.5% crude fibre on DM basis) iso-nutrient, PPSC “’summit” grower and finisher diets were formulated and blended to constitute the test diets. Blended grower test diets contained calculated 0, 2.5, 5, 7.5, 8.75 and 10% PPSC, respectively denoted G0, G1, G2, G3, G4, and G5. Blended finisher test diets contained calculated 0, 3.1255, 6.25, 9.375, 10.9375%, 12.5% PPSC, respectively denoted F0, F1, F2, F3, F4, F5. Dietary nutrient profiles were benchmarked to respective commercial grower and finisher maize-soybean positive control (PC) diets. The trial used 504 Ross 308 broiler chicks reared in an open, deep litter house partitioned into 1.5 m long x 1.4 m wide steel framed, mesh wire pens, each holding 18 birds. Chicks fed on the same commercial starter (days 1-24) diet, after which they were assigned to grower (days 25-35), followed by finisher (days 36-42) experimental diets for a completely randomised experiment replicated four times. Birds had free access to feed and water. Feed intake (FI), live weight gain (LWG), and the feed conversion ratio (FCR) were evaluated, along with slaughter weight, carcass characteristics, visceral organ weights, and meat quality. Quadratic regression analysis revealed significant effects of dietary PPSC levels on grower phase intake (P = 0.044) and cumulative grower-finisher live weight gain (P = 0.04). During the grower phase, feed intake increased (P < 0.05) with PPSC inclusion until it matched the control diet at PPSC dietary level G3 and above (P > 0.05). The optimum dietary inclusion of PPSC for feed intake during the grower phase was estimated to be 1.74%. For the finisher phase, broilers on the F0-F2 PPSC inclusion levels had lower final (42-day) live weights compared to the control (P < 0.05). Live weight at and above F3 PPSC dietary inclusion was intermediate, similar to both the lower level PPSC dietary inclusion and the control (P > 0.05). A quadratic estimate of 4.58% dietary optimum PPSC inclusion was predicted for the cumulative live weight gain. Dressed carcass weight increased (P < 0.05) with dietary PPSC inclusion at and above the G3-F3 PPSC feeding regime, matching the control diet (P > 0.05). A quadratic estimate of 3.01% dietary optimum PPSC inclusion was predicted for carcass weight. The dressing percentage increased (P < 0.05) with dietary PPSC inclusion above the G2-F2 PPSC feeding regime, matching the control diet (P > 0.05). A quadratic estimate of 7.58% dietary optimum PPSC inclusion was predicted for dressing percentage. Broilers on the G5-F5 feeding regime had higher (P < 0.05) abdominal fat compared to those on no or lower PPSC feeding regimes, while broilers on the G4-F4 feeding regime had intermediate abdominal fat (P < 0.05). A quadratic estimate of 4.73% dietary optimum PPSC inclusion was predicted for abdominal fat. Quadratic regression analysis also showed significant effects of PPSC levels on scaled gizzard weight (P = 0.007). The optimal dietary inclusion of PPSC for scaled gizzard weight was estimated to be 4.39%. In conclusion, within the limitations of the recommended dietary fibre content, grower-finisher dietary PPSC inclusion upgraded the sprouted cowpea diets to match the standard diet in terms of grower phase feed intake, finisher phase live weight gain, slaughter weight, abdominal fat, and the dressing percentage, with the predicted optimum dietary inclusion level dependent on the broiler response variable. Based on the carcass yield, approximately 3 % was considered optimum dietary PPSC inclusion in sprouted-cowpea based broiler diets.