1274
Effect of beta agonist and immunocastration on meat characteristics Nellore cattle
Beta agonists (BAA) have been used to improve feedlot performance and carcass yielding, but some negative effects on meat quality. Immunocastration could be an alternative because increasing fat deposition. Therefore, this work was developed to evaluate the effect of BAA and immunocastration on meat quality traits of feedlot finished Nellore cattle. Ninety-six males (409±50 kg LW; 20 mo old) were divided in two groups and half of the animals received two doses of immunocastration vaccine (Bopriva®) within 30 days interval. Animals were fed during 70 days a common diet containing 76% concentrate and 24% roughage (corn silage). Each of these groups were them splitted in three groups and fed during 30 days: control diet without BAA (CON); CON diet plus 80mg/day zilpaterol hydrochloride (Zilmax®) (ZIL); CON diet plus 300mg/day of ractopamine hydrochloride (Optaflexx®) (RAC). After 100 days of feeding animals were slaughtered and four samples of LM was collected between 12/13thribs and aged for 0, 7, 14 or 21 days. Following ageing samples were analyzed for L*, a*, b* color, cooking loss (CL), Warner-Bratzler shear force (WBSF). Data was analyzed as repeated measurements in a block (initial BW) complete randomized design with a 2 x 3 factorial arrangement, considering sex condition, treatment, ageing period and first and second order interactions as fixed effects. Immunocastrated males showed higher values (P<0.001) of L* (36.4 vs 33.3), a* (14.9 vs 13.9) and b* (10.0 vs 8.1) compared to non-castrated. Sex condition did not affect CL (22.2%) or WBSF (4.1 kg). There was a significant sex x ageing period interaction (P=0.0053) for WBSF that, different from expected, non-castrated males showed smaller WBSF than immunocastrated for non-aged (time 0) samples (5.2 vs 6.3 kg; P=0.0131). There was no sex difference for samples aged for 7, 14 or 21 days (4.4, 3.2 and 3.1 kg). Treatments had no effect on L* (34.9) but treatments CON and RAC showed higher a* values (14.8 and 14.6) than ZIL (13.7; P<0.05). CON had higher b* value than ZIL (9.5 vs 8.6; P=0.0271) but they did not differ from RAC (9.0). CL was not significantly affected by treatments. The WBSF was greater for ZIL (4.4 kg) than to RAC (4.0 kg) and CON (3.8) treatments. Sex condition affects meat color but has no impact on CL or WBSF. Use of BAA alter color attributes and WBSF of meat from Nellore cattle.
Keywords:
feedlot, color, maturation