Efeito da castração (física ou imunológica), manejo alimentar e ractopamina sobre o desempenho de suínos

Abstract

In order to evaluate the effects of the type of castration (physical or immunological), food management and inclusion of ractopamine (RAC) in pigs’ diet, four experiments were carried out using a total of 420 animals. In the first experiment, 160 pigs were used, 80 whole males (WH) and 80 castrated males (CM ), from the 7th to the 19th week of age. The animals were distributed in four treatments, factorial arrangement 2 x 2 (sexual category x nutritional plan), 10 repetitions. CM consumed a greater amount of feed (p <0.0001) and obtained worse feed conversion (FC) (p <0.0001). CM pigs submitted to the low density nutritional program (BD), had their growth rate compromised. There was less (p <0.05) fat deposition in the CM carcass. Aiming to compare the effect of sexual category and RAC inclusion in the diet on performance, carcass characteristics and meat quality of pigs fed ad libitum (AL) and restricted (RT) for four weeks before slaughter, the second and third experiments were carried out. In the second evaluation, 40 pigs (20 CM and 20 immunocastrated males (IC)) were distributed entirely at random, in a 2 x 2 factorial arrangement (sexual category x inclusion of ractopamine (RAC) in the diet), four treatments, five repetitions. These animals were fed ad libitum (AL). The third assessment was identical to the second, except for the food management that occurred in a restricted way (RT). In the second experiment, it was observed that IC pigs had better performance (p <0.05) and worse carcass yield (CY) (p <0.05) than CM pigs. The inclusion of RAC in the diet increased the shear strength on the pork steak. In RT feed management, IC pigs obtained less (p <0.05) fat deposition in the carcass. The inclusion of RAC in the diet provided higher (p <0.05) growth rate and a higher AOL for the pigs. Finally, aiming, mainly, to compare the performance between pigs WM / IC and CM , as well as the use of RAC in the final termination period, an experiment was carried out using 120 pigs (60 pigs WM / IC and 60 pigs CM ). The animals were randomly distributed in a 2 x 2 factorial arrangement (sexual category x inclusion of RAC in the diet), four treatments, five repetitions. At 23 weeks of age, RAC was included in the diet of half of the IC pigs and half of the CM pigs. In the total period evaluated, pigs WM / IC consumed less feed (p = 0.013), obtained better feed conversion (FC ) with similar weight gain (p> 0.05) to that of CM . After the second immunization, there was no difference (p> 0.05) in performance between the sexual categories. The RAC improved the CA of swine. At the time of slaughter, IC pigs had a lower fat thickness (-9%; p = 0.003) and less loin depth (9-6%; p <0.0001) than CM. In conclusion, these results show that WM pigs need a different diet to express their potential, and both immunocastration and inclusion of RAC in the diet contribute to better performance of pigs, reduce the deposition of fat in the carcass and that RT compromises growth rate, however, it can be partially offset by the inclusion of RAC.