This study explored the effects of different supplementation strategies in the dry and rainy seasons in the tropics on the carcass traits, meat quality, and economic viability of Nellore cattle produced under grazing conditions. For this purpose, twenty-eight non-castrated male animals (18 months) with an initial body weight of 327.93 ± 4.22 kg were used. The animals were equitably distributed in a randomized complete design thorough four supplementation strategies as follows: i) mineral supplementation (MS) in both dry and rainy seasons (MS/MS), ii) MS in the dry season and concentrate supplementation (CS) in the rainy season (MS/CS), iii) CS in the dry season and MS in the rainy season (CS/MS), and iv) CS in both dry and rainy seasons (CS/CS). Thereafter, carcass traits, primary carcass cut yields, meat quality traits, chemical composition of meat, and economic viability of cattle production across different supplementation strategies were determined. Data revealed that animals under CS/CS showed the greatest (P < 0.01) hot carcass weights among the other supplementation strategies evaluated. Conversely, supplementation strategy did not affect (P > 0.05) carcass traits (the ribeye area, final pH, and forequarter), meat quality traits (shear force, myofibrillar fragment index, sarcomere length, and color), and meat chemical composition (crude protein, fat, and moisture) of the animals. The effective operational cost, total cost, gross revenue, and profit of animals under CS/CS showed the greatest values, whereas the lowest ones were obtained for the animals under MS/MS. In conclusion, data suggest that concentrate supplementation during at least one season (dry or rainy) produces similar meat quality traits and chemical composition of meat, but different hot carcass weight, backfat thickness and hindquarter proportion to those observed when animals were supplemented with concentrate in both seasons. Additionally, CS/CS animals, despite having a higher total cost, have greater profitability when raised in tropical pasture.
This study was divided into two experiments. The first experiment with the use of fat-soluble vitamins (ADE) and/or water-soluble vitamins (biotin, niacin and thiamine) via diet in Nellore cattle. The second experiment with the use of vitamins AE and microminerals (Se, Mn, Zn and Cu) injected in crossbred cattle (¾ Angus, ¼ Nellore). Each of the two experiments originated a chapter of this thesis, totaling two chapters. In the first chapter, the effect of supplementation with a mix of B vitamins (biotin, niacin and thiamine), mix of vitamins (ADE) or a combination of these mixes on oxidation parameters, antioxidant status and quality of beef was evaluated. Nellore. Forty Nellore bulls, with a mean age of 8 ± 1 month and mean body weight of 261 ± 27.3 kg, were randomly assigned to four treatments: (a) without vitamin supplementation (Control); (b) vitamin B (B) mix supplementation; (c) mix supplementation of fat-soluble vitamins (ADE); and (d) combination of mixes (ADE + B). At the end of the 140-day period, the longissimus lumborum muscle was collected for analysis of meat quality, antioxidant enzyme activities and lipid oxidation at 1h, 24h, 196h and 360h postmortem. Supplementation with ADE and ADE+B increased intramuscular fat content, oxymyoglobin (OMb) and decreased metmyoglobin (MMb) at 196h and 360h postmortem, and decreased deoxymyoglobin (DMb) 196h postmortem, increased the Myofibrillar Fragmentation Index (MFI) 24h, 196h and 360h postmortem. In addition, ADE supplementation increased superoxide dismutase (SOD) and Ferric Antioxidant Reducing Power (FRAP), decreased glutathione peroxidase (GPx) and nitric oxide 24h postmortem, increased catalase and FRAP 196h postmortem, and increased FRAP and decreased malondialdehyde (MDA) 360 hours postmortem. In the second chapter, the effects of injectable supplementation of vitamins A and E and micro-minerals (Se, Mn, Zn and Cu) applied at weaning (D), castration (C) and pre- slaughter (PA) or their combination on meat quality, antioxidant status and lipid oxidation of crossbred cattle (¾ Angus ¼ Nellore). One hundred and twenty crossbred cattle, with a mean age of 7 ± 1 month and mean body weight of 304.58 ± 33 kg, were randomly assigned to six treatments: (N=20): (i) 000-Control (saline solution (SS) on D , C and PA; (ii) DCA - Vitamin- mineral complex (MVC) in D, C and PA; (iii) DC0 - MVC in D and C + SS in PA; (iv) D0A - MVC in D + SS in C + CVM in the PA; (v) 00A - SS in the D and C + CVM in the PA; (vi) 0CA– SS in the D + CVM in the C and PA. At the end of the period of 250 days, the collection was performed for the analyzes of meat quality, antioxidant enzyme activities and lipid oxidation in longissimus thoracis and lumborum muscle 1h, 24h, 196h and 360h postmortem. 192h and 360h postmortem. The shear force variable showed a difference 24h and 192h postmortem. Antioxidant activity (CAT and FRAP) and MDA showed a difference 1h postmortem. SOD and FRAP 24h postmortem, FRAP and MDA 192h postmortem and CAT and FRAP 360h postmortem. In the longissimus lumborum muscle, the Hue, MMb and OMb variables were different 24 hours postmortem. The variables a*, chroma and OMb showed a difference 192 hours postmortem and the variables a*, b* and chroma showed a difference 360h postmortem. FRAP showed difference 24h and 360h postmortem, GPx and SOD 360h postmortem. The use of CVM at least in PA reduces the oxidation of OMb to MMb and provides greater antioxidant status and decreased lipid oxidation. Keywords: Antioxidants. Colour. Myoglobin. Oxidation.
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