Warm-season grasses require N fertilization to achieve their full production potential; however, increased costs have limited the use of N by beef cattle (Bos spp.) producers. Th e objective of this study was to test the eff ects of two grazing frequencies (2 and 4 wk) on production, nutritive value, and persistence of 'Argentine' (tetraploid), 'Pensacola', 'Tift on 9', and 'UF Riata' (diploids) bahiagrass (Paspalum notatum Flügge) cultivars fertilized with 60 kg N ha -1 yr -1 . Th e study was conducted in Ona, FL, from January 2010 to December 2011. Treatments were eight factorial combinations of two grazing frequencies (2 and 4 wk) and four bahiagrass cultivars. Th e four cultivars were grazed by beef cows (505±30 kg) for approximately 8 h to a 7.5-cm stubble height at 2-or 4-wk intervals. Diploid cultivars had greater herbage accumulation (HA) in the spring; however, Argentine had greater annual HA in 2010 and 2011. Plots grazed at 4 wk had approximately 50% greater HA than 2-wk grazing frequency. Argentine and Pensacola had greater root and rhizome mass than Tift on 9 and UF Riata when grazed every 2 wk, while Argentine had greater cover than any of the diploids when grazed at the 2-wk frequency. Results show that Argentine is a productive and persistent bahiagrass for beef cattle producers using limited N fertilization and frequent grazing in Florida. Decreasing grazing frequency is an eff ective management practice to increase bahiagrass HA and persistence, particular the upright-growing Tift on 9 and UF Riata.
This study evaluated the nutritional interrelationship between the growing and finishing phases of crossbred cattle in determining their performance. One hundred and eight animals were used (8 months old, body weight [BW] 211 ± 20 kg). During the dry season, the animals received one of the following supplements: a mineral plus urea supplement (ad libitum, MSD), a protein supplement (1 g/kg BW per day, PR1), or a protein-energy supplement (5 g/kg BW per day, PE). During the rainy season, the animals received one of the following supplements: a mineral without urea supplement (ad libitum, MSR), a protein supplement (1 g/kg BW per day, PR2), or PE (5 g/kg BW per day). The experimental design was completely randomized using a 3 × 3 factorial scheme (for the rainy season) and a 3 × 3 × 2 factorial scheme (for the finishing phase). The supplementation and finishing systems were considered to be the treatments, and the animals were considered to be the experimental units. Dry season supplementation did not affect the average daily gain (ADG) during the rainy season (P = 0.12) or the finishing phase (P = 0.73). An increase in the level of rainy season supplementation reduced ADG by 12% during the finishing phase (P < 0.06). Providing PE during the dry and rainy seasons led to the animals being slaughtered 17 (P = 0.06) and 30 (P < 0.01) days earlier, respectively. Our results indicate that supplementation during the dry season (under poor-quality pasture conditions) does not affect the performance during the rainy season or the finishing phase. Furthermore, while providing PE during the rainy season can reduce ADG during finishing, the higher BW at the beginning of the finishing phase is sufficient to reduce the time of the finishing period.
-The objective of this study was to verify the effect of low-intake supplementation on performance of Nellore young bulls kept on Marandu grass pasture. The experiment was divided in two periods: the dry and rainy seasons. Treatments during the dry period were composed of mineral salt with urea and mineral supplement enriched with true protein and additive. In the rainy period treatments were mineral salt and enriched mineral supplement only. Pastures were evaluated and animals were weighed in both evaluation phases. The variables studied were evaluated in a completely randomized design in a split-plot arrangement, where plots were treatments and subplots were the periods within each phase, considering the types of supplementation as treatments. During the dry season there was no effect of supplement type in the first and second periods of assessment on weight gain of animals, which was of 0.307 and 0.113 kg/day, respectively. In the third period of this phase there was effect of the type of supplementation on animal performance; animals which received enriched mineral supplement gained 0.600 kg/day vs. 0.517 kg/day for those which received mineral salt with urea. In the rainy season, animals receiving enriched mineral supplement gained more weight than animals receiving mineral supplement: 0.800 and 0.696 kg/day, respectively. Mineral supplementation with addition of protein and additives provides increases in the weight gains of animals kept at a grazing regime of 15%.
The objective of this survey was to identify what mycotoxins were present in ingredients used in diets offered to beef cattle in feedlots and their concentrations. The survey covered 30 Brazilian feedlots located in the five major beef-producing states. Samples of total mixed ration (TMR) and ingredients were collected and analyzed for mycotoxin using ultra-performance liquid chromatography coupled to tandem mass spectrometry. Mycotoxin concentrations were further interpreted according to known species-specific sensitivities and normalized according to the principles of toxic equivalent factors (risk equivalent quantities-REQ) expressed in µg kg −1 of aflatoxin B1-equivalent. Forty percent of the visited feedlots had apparent fungi in TMR. However, only one feedlot (3%) used a mycotoxin adsorbent. On the other hand, diets with high contamination presented no apparent fungi. One hundred percent of TMR was contaminated. All samples presented at least one mycotoxin contamination, with 65.5% considered low contamination, 27.6% medium contamination, and 6.90% high contamination. The toxins identified in TMR were fumonisins (most frequently), trichothecenes A, trichothecenes B, fusaric acid, aflatoxins, and ergot (mean concentration values: 2,330, 104.3, 79.5, 105, 10.5, and 5.5 µg kg −1 , respectively). According to the contamination of TMR samples per region, Mato Grosso do Sul state presented the highest contaminations. Peanut meal was the most contaminated ingredient. One hundred percent of TMR in Brazilian feedlot is contaminated. Fumonisins were the mycotoxin most frequent and at highest concentrations in TMR samples. Moreover, mycotoxin concentrations have a distinct pattern among ingredients, TMR, and feedlots (local).
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