Interactive Effects of Phytic Acid and Oyster Shell particle size on Physiological, Carcass Traits and Economic Indices in Broiler Chickens.

Abstract

Phytic acid (PA) is an antinutritional factor in poultry diets. The effect of high dietary PA in chicken diets might be exacerbated when the particle size of oyster shell (OS) is too fine. Thus, this study investigated the hypothesis that high PA in the presence of fine OS particle size would increase the chelating of nutrients and impair growth in broiler chickens. Two hundred and eighty (280) Cobb 500 (all females) were assigned to four diets in a 2 × 2 factorial arrangement in a completely randomized design (CRD). The factors were PA (low or high) and OS particle size (fine or coarse) in starter, grower, and finisher diets. The diets were offered ad libitum throughout the starter (d 0 to 28), grower (d 28 to 42), and finisher (d 42 to 56) phases. Feed consumption, body weight (BW), gain, feed conversion ratio (feed: gain), and livability were collected weekly. The data collected at d 28 and 56 were bone (toe, femur, and tibia) dimensions, breaking strength (BS), and ash. On d 56, the breast, empty gizzard, proventriculus, liver, thigh, feet, thigh, and fat pad were weighed and expressed as % of body weight. None of the growth performance parameters in this study were subject to an interaction between OS particle size and PA and thus only main effects were discussed. The OS particle size and PA level as main effects did not affect any of the performance variables (P > 0.05) of birds on d 7. On d 14, coarse OS tended to improve FCR (P = 0.092). Low PA also tended to improve FCR (P = 0.059) compared to high PA on d 14 and feed intake was higher (P < 0.05) in birds fed diets containing high PA compared to birds on low PA. On day 21, high PA increased feed intake (P < 0.05) and tended to increase both gain (P= 0.099) and BW (P= 0.093) compared to low PA. High PA increased both the BW (P < 0.05) and Gain (P < 0.05) of birds compared to low PA on d 28. High PA tended to increase feed intake (P = 0.063), BW (P = 0.054), and Gain (P = 0.056) compared to low PA on d 49 and 56. High PA improved livability on d 49 (P < 0.05) and d 56 (P < 0.05) compared to low PA. In birds fed coarse OS, the crop and ileal pH were reduced (P < 0.05) by high PA. There was no main effect of OS, PA or their interaction on the calcium digestibility. There was an OS × PA interaction detected for tibial diameter (P = 0.064) on d 28 indicating that in birds fed fine OS, high PA increased tibial diameter. On d 56, OS × PA interaction was detected for tibial weight, % bodyweight (P < 0.05) indicating that it was only in birds fed coarse OS did high PA reduce tibial weight, % bodyweight. Also, an OS × PA interaction was detected for femur weight, % bodyweight (P = 0.086) indicating that low PA increased femur weight in birds fed coarse diets. On d 56, OS × PA interaction was detected for femur BS indicating that only in birds fed fine OS did high PA reduced femur BS (P < 0.05). At day 56, high PA as a main effect increased liver weight, % bodyweight (P = 0.071) but reduced feet weight, % bodyweight (P = 0.081). Low PA as a main effect increased thigh weight, % bodyweight (P < 0.05) compared to high PA. Overall, the study showed that high PA and coarse particle size of OS improved the production performance of broilers. There was no consistency in the effect of OS or PA on bone and carcass traits. But the general outcome suggests that a low PA and coarse OS may be preferred by broilers.