Finishing of grazing crossbred steers supplemented with detoxified castor bean meal (Ricinus communis L.) in the rainy-dry transition period.

This study evaluated levels of replacement of soybean meal by castor bean meal in the finishing crossbred steers on Brachiaria brizantha cv. Marandu pasture during the rainy-dry transition period. Forty Holstein-Zebu crossbred steers with an average initial weight of 395.93 ± 10 kg were randomly allocated to four treatment groups that were supplemented with concentrate levels of replacing (0, 290, 613, and 903 g/kg DM of the supplement; at 0.4% body weight [BW]). The experimental period was 120 days. A completely randomized experimental design was adopted; with regression analysis using the computational software package (SAS 9.2, USA). Intake and digestibility of dry matter (DM) and nutrients and animal performance were evaluated. The replacement levels did not influence (P > 0.05) the intakes of DM (kg/day), organic matter (OM, kg/day), neutral detergent fiber (NDF, kg/day and %BW), non-fibrous carbohydrates (NFC, kg/day), or total digestible nutrients (kg/day). However, the intake of crude protein (CP) and ether extract (EE, kg/day) decreased as the replacement levels were increased (P < 0.05). The digestibility of DM, OM, NDF, and EE did not change, whereas CP digestibility decreased linearly and NFC digestibility increased linearly (P < 0.05). The replacement levels did not affect (P > 0.05) final body weight, average daily gain, feed conversion, and carcass yield. Castor bean meal can replace up to 903 g/kg DM of soybean meal in the composition of the supplement without compromising the performance of steers on Marandu pasture during the rainy-dry transition period.

Feeding behavior of post-weaned crossbred steers supplemented in the dry season of the year.

The objective of this study was to evaluate the feeding behavior of grazing steers supplemented in the dry season of the year. Thirty-two castrated crossbred (½ Holstein-Zebu) steers with an average initial weight of 378 ± 7.54 kg, aged 14 months, were distributed into four treatment groups in a completely randomized design with eight replicates. The animals were managed in an area covered with a pasture of Brachiaria brizantha cv. Marandu, in a rotational grazing system. The supplement was formulated so that the animals in the different treatment groups would ingest the same amount of crude protein (CP) daily. Thus, the treatments consisted of increasing levels of supplementation, based on the animals' body weight (BW), as the protein content of the supplement was reduced. The following treatments (dry matter basis) were tested: T2, supplement at 0.2% BW, with 50% CP; T4, supplement at 0.4% BW, with 25% CP; T6, supplement at 0.6% BW, with 16.67% CP; and T8, supplement at 0.8% BW, with 12.5% CP. Forage dry matter intake decreased linearly (P < 0.05), characterizing a substitution effect. The increasing supplementation levels influenced the animals' feeding behavior, especially grazing time, total feeding time, number of grazing bouts, and number of bites per day, which showed a positive quadratic response (P < 0.05), and rumination time, number of rumination bouts, number of cuds ruminated per day, and number of chews per ruminated cud, which exhibited a negative quadratic behavior (P < 0.05). Dry matter and neutral detergent fiber (NDF) feed efficiencies and dry matter and NDF rumination efficiencies responded quadratically (P < 0.05). In conclusion, concentrate supplementation at up to 0.8% BW improves the feeding behavior of grazing steers in terms of the intake of concentrate supplement and forage as well as the feed and rumination efficiencies.

Ingestive behavior of Girolando steers supplemented on tropical pastures.

In this study, we evaluated the feeding behavior of Girolando steers on Brachiaria brizantha cultivar Marandu pastures. Twenty-two animals with an average initial weight of 209.09 ± 8.18 kg were distributed in a completely randomized design in a 3 × 2 factorial arrangement (three seasons and two nutritional plans (NP)) with 11 replicates, as follows: rainy season 1 (NP1, mineral mixture ad libitum, and NP2, nitrogen/energy supplement [2 g.kg‒1 body weight [BW]]); dry season (NP1, nitrogen/energy supplement [1 g.kg‒1 BW], and NP2, nitrogen/energy supplement [2 g.kg‒1 BW]); and rainy season 2 (NP1, mineral mixture ad libitum, and NP2, nitrogen/energy supplement ([1 g.kg‒1 BW]). Total chewing time was longer in NP1 (566.44 vs 528.33 min.day‒1 in NP2) (p < 0.05). The grazing, idle, trough, and total chewing times were affected by the interaction between nutritional plans and seasons. The period expended grazing was longer for the NP1. The idle time was affected by the nutritional plans and was lower for the NP1. Feeding at the trough was not affected by the nutritional plans. The animals of the NP2 showed the highest feed efficiencies in DM and NDF (0.91 and 0.52 vs 0.75 and 0.45 in NP1, respectively). Rainy season 2 had the highest efficiencies. The feeding behavior changes according to the supplementation level. Nutritional plan 2 in the second rainy season presented the best results.