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The effects of partial replacement of corn (Zea mays L.) with dried cashew nut (Anacardium occidentale L.) testa on energy utilization, nutrient digestibility, growth performance, and carcass characteristics of finishing pigs
Dissertation Abstract:
Three studies were conducted to determine the nutrient composition of dried cashew nut testa (DCNT) and its effects on nutrient digestibility, gut morphology, growth performance, economic return, and carcass characteristics in finishing pigs. On a DM basis, DCNT contained 5,111 kcal/kg GE, 14.1% CP, and 64.9 g/kg condensed tannins. In Study 1, 16 barrows with an initial BW of 54.6 ± 0.8 kg were used to measure the digestible (DE) and metabolizable (ME) energy concentration in DCNT. Pigs were randomly allotted into two treatments using a completely randomized design with eight replicate pigs per treatment. The first diet was a corn-soybean meal basal diet whereas the second diet contained 75% of the basal diet and 25% of DCNT. The ATTD of GE and N of pigs fed the basal diet were greater (p < .01) than those fed the DCNT diet. On a DM basis, the DE and ME of DCNT were 778 and 733 kcal/kg. In Study 2, DCNT was soaked in distilled water (1:10 w/v) for 0 h (DCNT-0), 24 h (DCNT-24), and 48 h (DCNT-48) to determine if water soaking can reduce the concentration of condensed tannins in DCNT. The butanol-HCl was used to evaluate condensed tannins. Soaked DCNT for 24 h reduced (quadratic, p < .01) the concentration of condensed tannins by 26.2%, however, there was no further reduction between DCNT-24 and DCNT-48. Treatments DCNT-0 and DCNT-24 were selected for Study 3. In this study, 48 finishing pigs (24 barrows and 24 gilts; initial BW of 82.1 ± 2.1 kg) were used. Four experimental diets were prepared. The first diet was a corn-SBM diet whereas the next three diets were the corn-SBM diet with 5% unsoaked DCNT, 5% unsoaked DCNT+fat, and 5% soaked DCNT. The DCNT replaced corn in all the diets. The ATTD of DM, CP, GE, EE, NDF, and ADF was evaluated from the 24 barrows using a randomized complete block design. Pigs fed the corn-SBM diet had greater (p < .05) ATTD of CP, GE compared with those fed the unsoaked DCNT diets. The ATTD of EE in pigs fed unsoaked DCNT+fat was greater (p < .01) than the pigs fed the other diets. A part of duodenum and jejunum was collected from three pigs from each diet at the last day of slaughtering to measure small intestinal morphology. There were no (p > .05) differences in villus height, crypt depth, and villus height : crypt depth among pigs fed the different diets. Growth performance of all 48 pigs was evaluated using a 4 × 2 factorial arrangement of treatments in a randomized complete block design. Diet and gender were the factors. No interactions were observed on growth performance and caloric efficiency. However, barrows were heavier (106.1 kg; p < .05) and had greater (1.04 kg/d; p < .01) ADG than gilts (97.9 kg and 0.87 kg/d, respectively). Barrows also tended (p = 0.10) to have better caloric than gilts. The price of the unsoaked DCNT diet was cheapest but the margin over feed cost of soaked DCNT diet gave the highest profits. There were no interaction and diet effects on carcass characteristics and relative organ weights except kidney weight which was greater (p < .05) in pigs fed the corn-SBM diet. However, barrows had heavier (80.0 kg; p < .05) hot carcass weight than gilts (73.8 kg). Back fat thickness at P2 and LSQ of gilts (2.10 cm; p < 0.05 and 0.13; p < .01) were better than barrows (2.48 cm and 0.17). Likewise, the relative kidney weight of gilts was greater (p < .05) than barrows.