Desempenho e avaliação nutricional de dietas contendo farelo de mamona para bovinos / Performance and nutritional evaluation of diets containing castor meal to cattle

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The castor bean (Ricinus communis L.) has been traditionally cultivated in some parts of Brazil with an economic and social role. Thus, because of the high potential of productivity that this culture shows, there is a possibility to increase the use of the castor beans by- products as a protein source in ruminant diets. In order to evaluate the use of castor bean meal as a substitute for soybean meal, were developed two experiments. The experiment I, was carried out aiming to evaluate the effect of replacing soybean meal (SM) by castor bean meal treated with 6% of calcium oxide (CMT) or not (CMWT) on nutrients intake, performance, carcass traits and commercial cuts yield of feedlot cattle. Thirty Bos indicus steers with 360 kg 30,27 of initial body weight (BW) were used. From this group, five animals were slaughtered on the beginning of the experiment to be used as a reference group and the 25 animals remaining were blocked into five groups based on initial BW and allotted randomly to one to five treatments (five animals per treatment). The animals were fed with 65% of corn silage and 35% concentrate, in dry matter basis (DM). It was used five diets with four levels of SM replaced by CMT: 0, 33, 67 and 100%, in the DM basis and one treatment with 100% of SM replaced by CMWT. At the end of the experiment, all animals were slaughtered and its viscera cleaned to determine the empty body weight (EBW). There were no significant effects (P>0,05) to the substitution of SM by CMT on the constituents of the diet intake, body weight gain (WG) and empty body weight gain (EBWG). Despite the higher (P<0,05) ricin intake for diets with CMWT (3,06 mg/kgBW) in relation to diet with CMT (0,10 mg /kgBW/day), there were no effect (P>0,05) on the constituents of the diet intake, WG and EBWG. The DM intake and WG were 10,66 and 1,44 kg/day on average. The carcass dressing in relation to body eight was affected and it was observed a linear decrease (P<0,05) with the replacement of SM by CMT. There was no effect (P>0,05) by replacing SM by CMT and the treatment with calcium oxide of the CMWT on the carcass basic cuts yield. CMT prices over 85% of the SM (DM basis) didnt justify its use economically. For prices from 20 to 80% of CMT, 67% was the optimum level of substitution, while prices below 15% of SM, the optimum level was 100% substitution of SM by CMT. The experiment II, was conducted aiming to evaluate the effect of replacing soybean meal (SM) by castor bean meal treated (CMT) with calcium oxide or not (CMWT) on feed intake, total, ruminal and intestinal digestibility diets constituents, ruminal concentrations pH and ammonia, the urinary N-urea excretion, the ruminal degradation kinetics of the protein feed and the estimation of the microbial protein production obtained from the urinary purine derivatives excretion or the purine bases in the abomasum. Five Bos indicus steers were used, with 360 kg 30,27 of initial body weight cannulated in the rumen and abomasum. The experimental design was in Latin Square 5x5, with five animals, five periods and five treatments. Each experiment had duration of 14 days, eight days of adaptation and six to the collections. The animals were fed with a diet containing 65% of corn silage and 35% concentrate, in dry matter basis (DM). It was used five diets with four levels of SM replaced by CMT: 0, 33, 67 and 100%, in DM basis and one treatment with 100% of SM replaced by CMWT. Only the DM digestibility was reduced (P<0,05) by castor bean meal alkaline treatment. With the exception of crude protein ruminal digestibility (CPRD), there was no effect of calcium oxide (P>0,05) on the other digestibility constituents. There was an increase of 24,2% CPRD (P<0,05) for the CMWT on CMT. The intestinal digestibility of diets constituents were not affected by the level of replacement of SM by CMT. However, the alkaline treatment of CMWT reduced (P<0,05) the EE intestinal digestion. There was no interaction (P>0,05) between treatment and time on ruminal pH, but the pH was influenced (P<0,05) by the time of blood collection, and the minimum value observed was 6,23 at 5,8 hours after the feeding. There was an interaction (P<0,05) between treatments and sampling times for N-NHB3 Bconcentrations. There was no difference (P>0,05) for the urinary nitrogennous compounds excretion on the levels of replacement of SM by CMT and alkaline treatment of CMWT. The microorganisms RNA-N: N-total ratio was not affected by levels of CMT, with 0,138 of average. No differences were found (P>0,05) between the two methods of collection to estimate the crude protein microbial production. The castor bean meal treated with 6% of calcium oxide can replace soybean meal fully in the diets of feedlot beef cattle. The castor bean meal without treatment showed satisfactory results, however considering the danger of the presence of ricin, caution should be taken into use.

ASSUNTO(S)

farelo de mamona nutricao e alimentacao animal bovino beef cattle castor meal

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