The study aimed to evaluate the effects of three supplementation strategies on intake, apparent digestibility, feeding behavior, performance, carcass traits, proximate composition, and the fatty acid profile of meat from steers on tropical pasture during the post-weaning and finishing stages. The experiment involved 33 1/2 Holstein × 1/2 castrated Zebu steers weighing 335 ± 42.90 kg, aged 22 ± 2 m. The animals were managed on Urochloa brizantha cv. Marandu using an intermittent grazing system with continuous stocking and variable stocking rates for 310 days. The supplementation strategies were as follows: MS/US (mineral salt/urea supplementation): mineral salt in the rainy season and mineral salt with urea in the dry season; US/PS1 (urea supplementation/protein supplementation): mineral salt with urea in the rainy season and protein supplement at 1 g/kg body weight (BW) in the dry season; and PS1/PS2 (protein supplementation 1/protein supplementation 2): protein supplement at 1 g/kg BW in the rainy season and 2 g/kg BW in the dry season. The dry matter intake did not differ significantly (p > 0.05) between strategies. However, the post-weaning PS1/PS2 strategy resulted in higher (p < 0.05) crude protein intake. The final body weight did not differ (p > 0.05) between the strategies, but the average daily gain in post-weaning and finishing was higher (p < 0.05) for MS/US (restricted) animals. Carcass weight, subcutaneous fat thickness, and lipid content in meat were significantly higher (p < 0.05) for steers in the PS1/PS2 group. Steers finished on MS/US produced meat with a higher content of polyunsaturated fatty acids and ω-3 fatty acids (p < 0.05). Concentrate supplementation at 1 g/kg BW during the rainy season and 2 g/kg BW during the dry season is recommended for post-weaning and finishing steers on tropical pasture.

Objective: to evaluate the effects of organic copper (Cu) and selenium (Se) on milk production, milk quality and reproductive parameters of Normande dairy cows. Materials and methods: 36 multiparous cows (BW = 600 ± 32 kg) were used, distributed in completely randomized blocks. Treatments were: T0: without mineral supplementation, T1: inorganic mineral supplementation with Cu and Se, T2: 50% Inorganic supplementation + 50% organic supplementation, with an experimental period of 150 days (30 days before calving and 120 days of lactation). The variables evaluated were milk production and quality (total solids, proteins, fat, somatic cells and MUN), blood metabolites (glucose, betahydroxybutyrate and BUN) and reproductive parameters (open days, days to first service and services per conception). Results: No differences were observed in milk production and quality (P> 0.05). However, open days and services per conception were shorter when cows were supplemented with organic minerals (P <0.05). Conclusions: In this study milk production, milk quality and blood metabolites were not affected by supplementation with Se and Cu. However, the reproductive parameters of the cows improved when supplemented with organic Se and Cu.

Extensive livestock management is a common practice in the dry tropics. However, summer conditions can cause high fiber and low protein concentrations, even in grasses adapted to tropical soils, such as Angleton (Dichanthium spp.), widely used in producing small ruminants. On the other hand, Guacimo (Guazuma ulmifolia) is a tree that overcomes high temperatures and hydric stress. This research evaluated the effect of replacing Angleton with four foliage levels of Guacimo on hair lambs’ intake, digestibility, and blood metabolites. Twelve male hair lambs with an average of 22.0 ± 1.3 kg of body weight were used in an experimental 4 × 4 square design. Treatments were as follows: 100 % Angleton hay; 85 % Angleton hay + 15 % Guacimo foliage; 70 % Angleton hay + 30 % Guacimo foliage, and 55 % Angleton hay + 45 % Guacimo foliage. Dry matter (DM), organic matter (OM), crude protein (CP), and neutral detergent fiber (NDF) intake, as well as CP digestibility and glucose concentrations, increased linearly as the level of Guacimo rose (P > 0.05). Guacimo foliage improves intake, blood metabolites, and in vivo digestibility of DM and can be used to replace part of the hay in lamb rations.

The objective of this study was to determine whether supplementing pregnant beef cows with regular nitrogen or a slow-release nitrogen source at the late gestation could enhance the use of a low protein basal diet and improve the performance of cows and their offspring until weaning. Thirty-five pregnant Brahman cows (556 ± 47 kg and 4.5 ± 1.4 years old) were individually housed in covered pens and randomly divided into three groups. From 180 ± 19 days of gestation until calving, cows were fed either a control (CON, n = 12) low crude protein (CP) basal diet (6% of CP, ad libitum) plus mineral mixture (130 g·cow^-1·d^-1), or the CON treatment supplemented with protein concentrate supplements (40% CP, fed 2 g·kg of BW^-1·d^-1 in the morning) based either on a regular (REG, n = 11) composition (corn, soybean meal, and urea) or on a slow-release N (SRN, n = 12) source (Timafeed Boost, Roullier Group, Saint-Malo, France) which replaced 60% of soybean meal and urea in the supplement composition. The MN, fetal sex (FS), and MN×FS were used as fixed effects in the statistical model, while the number of previous calvings was considered as a random effect. Maternal initial BW was used as a covariate. Statistical differences were declared at P < 0.05. Supplementation with REG and SRN increased total dry matter intake (DMI) and basal diet intake compared with the control treatment (P < 0.01). Protein supplementation allowed the cows to have a higher average daily gain (P < 0.01; 0.177 and 0.193 kg/day, respectively, for REG and SRN) than the CON treatment (-0.255 kg/day). Body condition score (BCS) also increased (P < 0.01) when cows received protein supplementation in late pregnancy, but with no differences between REG and SRN cows (P = 0.31). Interactions between MN and FS were observed for calf birth weight (CBW, P < 0.01) and calves' average daily gain up to 120 days of age (ADG120, P = 0.01), but not at weaning weight (P = 0.69). Male calves born from REG and SRN cows were born heavier and gained more weight up to 120 days after birth than calves born from CON cows (P < 0.05) but did not differ from each other (P = 0.94 and 0.92, respectively, for CBW and ADG120). Female calves had no differences in CBW and ADG120 as a function of maternal dietary treatment during pregnancy. The REG and SRN calves weaned heavier (P < 0.05) than CON calves. In conclusion, supplementing protein to pregnant beef cows during periods of low CP pasture improves maternal and progeny performance. The SRN-based product can replace the major part of soybean and urea in the protein supplement, achieving same level of improvement in forage utilization and animal performance as the regular protein-based supplement.

The aim was to evaluate the fatty acid profile of meat of crossbred cattle grazing under different supplementation strategies. Thirty crossbred steers (1/2 Holstein x 1/2 Zebu) were used in a completely randomized design with three groups of different supplementation strategies (SS) according to the climatic season of the year: SS-1 (mineral salt/mineral salt with urea), SS-2 (mineral salt with urea/protein supplement 0.1% PC), and SS-3 (protein supplement 0.1% BW / 0.2% BW protein supplement). Longissimus dorsi muscle samples were collected, stored, and frozen until analysis of the fatty acid (FA) profile. Data were subjected to analysis of variance (ANOVA), using the Tukey test (P < 0.5) (SAS 2008). Our results exhibited that the oleic acid (C18: 1n9cis) was affected by supplementation strategies, the oleic acid was higher (34.91%) in SS-1. In addition, the content Polyunsaturated fatty acids (PUFA; P <0.05); C18: 3n3 (α – linolenic), C18: 2c9t11 (Rumenic / CLA), C18: 2t10c12 (Trans-10, cis-12-octadecadienic / CLA) and C20: 5n3 (eicosapentaenoic - EPA) also were higher in SS-1. In contrast, in SS-3 the C20: 4n6 (arachidonic) was higher (1.09%). The total PUFA content was influenced (P <0.05), with a higher content in the SS-1 group (3.58%). SS-3 influenced higher levels of AG n-6 (1.86%), and AG n-3 (1.02%) being higher in SS-1, producing a lower n-6: n-3 ratio in SS-1 (P <0.05) of 1.57. Grazing animals with mineral supplementation SS-1 showed meat with a higher composition of polyunsaturated fatty acids, mainly omega-3 and CLA, which provided a reduction in the n-6: n-3 ratio, highly related to human health.