Two studies evaluated the productive characteristics of young Nellore heifers receiving different days on feed (DOF) to determine the biological slaughter endpoint. In Experiment 1 (Exp. 1), fifty-one Nellore heifers [324 ± 19.3 kg of body weight (BW); 16 ± 1 months] were split into three DOF lengths (45, 75, or 105 days), while in Experiment 2 (Exp. 2), thirty-six Nellore heifers (362 ± 25.5 kg of BW; 18 ± 1 months of age) were split into three DOF lengths (45, 90, or 135 days). In both studies, all animals were distributed in complete randomized blocks according to initial BW and stratified via carcass ultrasound. The diet was supplied ad libitum, allowing 3% of refusals. The point at which the animals achieved 25% of ether extract of shrunk body weight (EE_SBW) was defined as the biological endpoint. Thus, relationships were made between some characteristics obtained in both studies. Positive linear relationships were found between backfat thickness (BFT) vs. EE_SBW (p < 0.001, r = 0.84) and BFT vs. body weight (p < 0.001, r = 0.77). Our results suggest that the biological slaughter endpoint for young Nellore heifers is 6.97 mm of backfat thickness or 402 kg shrunk body weight, corresponding to around 75 DOF.

Effects of a blend of live yeast and organic minerals as an alternative to monensin and inorganic trace minerals for beef cattle finished on pasture with high concentrate supplementation, on growth performance, intake, digestibility, liver trace mineral and carcass characteristics were evaluated. Forty-eight Nellore bulls were blocked by initial body weight and randomly assigned to one of the two experimental diets. The animals were raised in an experimental pasture divided into 12 paddocks equipped with an electronic system for monitoring individual feeding behavior and feed intake. Treatments were: (1) Monensin (MON), 30 mg/kg supplement dry matter of sodium monensin and trace minerals supplementation from inorganic sources; (2) AdvantageTM (ADV), 1.6 g/kg supplement DM of a blend of live yeast (Saccharomyces cerevisiae strains) and organic trace minerals. The use of ADV instead of MON led to greater supplement intake and greater intake of dietary components. Bulls fed ADV also had higher digestibility of dry matter, organic matter, crude protein and non-fiber carbohydrates. Bulls fed MON had a greater number of visits to the feeder, however with a shorter time spent feeding per visit. The use of ADV resulted in higher average daily weight gain, and feed efficiency was similar between treatments. In the carcass, ADV tended toward greater Longissimus muscle area. Liver Zn concentration tended to be lower in the ADV treatment. The use of ADV generated higher meat lightness and redness. In summary, the blend of live yeast and organic minerals can be an alternative to monensin and inorganic sources of trace minerals for beef cattle finished on pasture with high concentrate supplementation, without negative effects on supplement feed efficiency and with benefits to animal growth.

The objective of this study was to evaluate four different feeding strategies using an immunomodulatory feed additive for newly weaned Nellore cattle, before and after road transport, on their physiological parameters and performances during the growing phase of pastures. In total, eighty-four young Nellore bulls (initial BW = 174 ± 11 kg; 7 ± 1 months of age) were blocked by their initial body weights 42 days before road transport (d −42) and randomly assigned to one of the four supplementation strategies. The treatments were: (1) Control (CON): no immunomodulatory feed additive (NUTRA) supplementation; (2) NUTRA pre: the inclusion of NUTRA only in the pre-transport period (d −42 to d 0); (3) NUTRA post: the inclusion of NUTRA for 42 days, only in the post-transport period (d 0 to d 42); and (4) NUTRA growth: the inclusion of NUTRA during the whole experimental period (d −42 to d 210). On d 0, the calves were transported on dirty roads in a commercial livestock trailer for 200 km (8 h). There was no effect of the treatments on the animal performance or the physiological parameters in their plasma. However, there were effects on the day of the blood sampling for all the parameters. The highest concentration of cortisol was observed on d 3 post-transport (129 ng/mL) and this decreased over time (22.4 ng/mL; d 210). On the other hand, their glucose peaked at unloading, with lower concentrations on d 7 and d 14. Their total protein concentrations increased from d 0 to d 7. The immunomodulatory feed additive supplementation at 10 g/100 kg BW/day did not modulate the physiological responses in their plasma and did not influence the performance of the Nellore bulls during the growing phase of their pastures.

The study investigated the effects of 48-h water and feed deprivation on blood and the performance of grazing Nellore (Bos indicus) heifers. Twenty-four Nellore heifers (initial body weight [BW] = 238 ± 10 kg; age = 16 ± 2 mo), were ranked by initial BW and age and randomly assigned to one of the two treatments: (1) grazing animals with free access to pasture, water, and mineral-mix (CON; n = 12), or (2) the same grazing conditions but deprived of pasture, water, and mineral-mix for 48 h (DPR; n = 12). The paddocks consisted of Urochloa brizantha cv. Marandu, using a continuous and fixed stocking rate. The experiment lasted 225 d, with the first 14 d considered as the adaptation period (days −14 to −1) and the subsequent 211 d as the evaluation period (days 0 to 211). From days 0 to 2, treatments were applied by keeping the DPR heifers in pens and reintegrating them into the experimental area after a 48-h water and feed deprivation. Individual full BW was recorded on days −14, −13, −1, before (day 0) and after (day 2) treatment application, and on days 6, 11, 12, 41, 42, 210, and 211. Blood samples were collected in the morning on days 0, 2, 6, 12, and 211. A treatment effect was detected (P < 0.001) for shrink BW from days 0 to 2, which was greater (P < 0.001) in DPR vs. CON heifers. Subsequently, DPR animals were lighter (P < 0.001) compared with CON heifers by the end of the deprivation period (day 2). From days 4 to 211, DPR was lighter (P < 0.001) compared with CON heifers after treatment application and for the entire experimental period. In the first 10 d after treatment application (days 2 to 12), DPR heifers showed a partial compensatory average daily gain (ADG; P < 0.001) compared with CON heifers, while no significant differences were observed in ADG between the treatments from days 12 to 42 and 42 to 211 (P > 0.420). Overall ADG (days 2 to 211) was greater (P < 0.001) for DPR vs. CON heifers. All serum variables, except AST, were higher (P < 0.001) in DPR than in CON heifers on day 2 after treatment application. Our study demonstrates that grazing Nellore heifers subjected to 48-h water and feed deprivation experienced significant alterations in their blood metabolites and BW immediately after the stressful event. Although the deprived heifers partially compensated for their BW loss in the early days post-deprivation, they remained 12 kg lighter than the non-deprived animals throughout the production cycle. Routine management practices in beef cattle operations, such as shipping and receiving at feedlot facilities, may cause the animals to go without food and water for extended periods. The findings of this study reveal that Nellore (Bos indicus) heifers subjected to a 48-h water and feed deprivation exhibited substantial changes in their blood metabolites and lost 14.6% of their body weight by the completion of the deprivation period. Although the deprived heifers showed a partial compensatory increase later, they remained 12 kg lighter than the non-deprived heifers throughout the production cycle.

The objective of this study was to evaluate the effects of different trace mineral sources on rumen fermentation parameters and bacterial diversity, liver concentration of Cu and Zn, and performance of grazing Bos indicus Nellore cattle during the dry-to-rainy transition season. In Exp. 1, eight Nellore steers [body weight (BW) = 541 ± 18 kg, and 32 ± 1 mo. old] fitted with ruminal cannula were randomly assigned to eight paddocks in a completely randomized design. In Exp. 2, a total of 120 Nellore bulls (BW = 341 ± 45.9 kg and age = 20 ± 1 mo) were blocked by initial BW and distributed into 12 paddocks (6 paddocks/treatment). Each animal or paddock were supplemented with a protein supplement (5 g/kg of BW daily) containing (1) 40 mg of Cu/kg of supplement from the Cu sulfate source and 148 mg of Zn/kg of supplement from the Zn oxide source (ITM; n = 4), or (2) 40 mg of Cu/kg of supplement and 148 mg of Zn/kg of supplement from hydroxychloride sources (HTM; n = 4; IntelliBond CII, IntelliBond Z, Selko, Indianapolis, IN). The 101-d experiment included an 11-d adaptation period followed by three 30-d periods. Ruminal fluid was sampled at 0, 6, 12, and 18 h post-supplementation on d 24, 52, and 84 (Exp. 1). Body weight was recorded at the start, after adaptation, and every 30 d following a 16-h feed and water withdrawal (Exp. 2). In Exp. 1, no treatment effects were observed (P ≥ 0.13) for total short-chain fatty acid (SCFA) concentration and molar proportion of acetate, propionate, isobutyrate, butyrate, valerate, Ac: Pr ratio, ruminal pH, and N-NH3 concentration. The rumen microbiology analysis revealed that the phylum SR1 was affected by the treatments, with higher abundance in HTM (P = 0.03) than in ITM steers. At the genus level, 13 genera were affected (P ≤ 0.05) by treatments. Animals fed HTM had increased (P ≤ 0.05) ruminal abundance of taxa commonly associated with the fiber and starch and soluble carbohydrate degraders group, whereas steers receiving ITM had higher abundance of Fibrobacter, Butyrivibrio 2, Ruminiclostridium 5, and the Archaea genus Methanobrevibacter. In Exp. 2, HTM bulls had greater BW after 60 d (P ≤ 0.03) of the experiment, with greater ADG between days 30 and 60 (P < 0.03). These results demonstrate that HTM might serve as an effective source of Cu and Zn for grazing Nellore cattle and was associated with improved growth performance during the dry-to-rainy transition, along with concurrent shifts in ruminal microbial diversity.