The objective of this study was to evaluate the effects of monensin supplementation on animals receiving warm-season grass with limited supplementation. In Exp. 1, treatments were a factorial combination of 2 stocking rates (1.2 and 1.7 animal unit [AU] [500 kg BW]/ha) and supplementation with monensin (200 mg/d) or control (no monensin) distributed in a complete randomized design with 3 replicates. Thirty Angus × Brahman crossbred heifers (Bos taurus × Bos indicus) with initial BW of 343 ± 8 kg were randomly allocated into 12 bahiagrass (Paspalum notatum) pastures and supplemented with 0.4 kg DM of concentrate (14% CP and 78% TDN) daily for 86 d. Herbage mass (HM) and nutritive value evaluations were conducted every 14 d, and heifers were weighed every 28 d. There was no effect (P ≥ 0.97) of monensin on HM, herbage allowance (HA), and ADG; however, animals receiving monensin had greater (P = 0.03) plasma urea nitrogen (PUN) concentrations. The stocking rate treatments had similar HM in June (P = 0.20) and July (P = 0.18), but the higher stocking rate decreased (P < 0.01) HM and HA during August and September. Average daily gain was greater (P < 0.01) for the pastures with the lower stocking rate in August but not different in July and September (P ≥ 0.15). Gain per hectare tended to be greater on pastures with the higher stocking rate (P ≤ 0.06). In Exp. 2, treatments were 3 levels of monensin (125, 250, and 375 mg/animal per day) and control (no monensin) tested in a 4 × 4 Latin square with a 10-d adaptation period followed by 5 d of rumen fluid collection and total DMI evaluation. Blood samples were collected on d 4 and 5 of the collection period. Ground stargrass (Cynodon nlemfuensis) hay (11.0% CP and 52% in vitro digestible organic matter) was offered daily. The steers received the same supplementation regimen as in Exp. 1. Total DMI was not different among treatments (P = 0.64). There was a linear increase (P ≤ 0.01) in propionate and a tendency for decreased acetate (P ≤ 0.09) concentrations in the rumen with increasing levels of monensin; however, there was no effect (P ≥ 0.19) of monensin levels on ruminal pH and ruminal concentrations of butyrate and ammonia. In addition, there was no effect (P ≥ 0.73) of monensin levels on plasma concentrations of glucose, insulin, IGF-1, and PUN. In summary, monensin supplementation effects were not detected at either stocking rate and may not be effective in increasing performance of beef cattle grazing low-quality warm-season grasses with limited supplementation.

The aim of this work was to evaluate the nutritional value of four sorghum-sudangrass hybrids harvested at four different stages of maturity. The hybrids evaluated were BR800, BRS810 (bmr), BRS802 and 156x2784. Hybrids were harvested at 52, 61, 67 and 74 days after seeding. BRS802 and BRS810 (bmr) are sorghum-sudangrass hybrids isogenic pairs that are distinguished only by the presence of bmr-6 mutation on BRS810. Samples were analyzed for dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF) and acid detergent lignin (ADL) content and in vitro DM and NDF digestibility (IVDMD and IVNDFD). Interaction between hybrid and stage of maturity was observed for NDF, ADF, IVDMD and IVNDFD. A linear increase in DM content was observed with increasing stage of maturity. A quadratic effect was observed for CP content with increasing stage of maturity, and the maximum CP value was estimated to be with 55.8 days. The hybrid BR800 had the highest CP content (12.5%) and the hybrids BRS 802 and 156x2784 the lowest CP content (9.7 and 10.3%, respectively) for all stages of maturity evaluated. A quadratic effect in NDF content was observed with increasing stage of maturity for the hybrids BR800, BRS810 (bmr) and BRS802 with the maximum values estimated to be with 62.0, 61.7 and 60.4 days after seeding respectively. With 52 and 67 days after seeding the hybrid BRS810 (bmr) had the lowest NDF content (64.2 and 66.4%, respectively). The isogenic pair, hybrids BRS802 and BRS810 (bmr), had a linear decrease in ADF content with increasing stage of maturity, and with 52, 61 and 67 days after seeding the bmr hybrid had lower ADF content compared to its counter pair (BRS802). No linear or quadratic effect with increasing stage of maturity was observed for ADL content. The hybrids BRS802 and 156x2784 had the highest ADL content (4.42 and 4.16%, respectively) regardless of the stage of maturity. BRS810 (bmr) had the lowest ADL content (2.49%) and intermediate value was observed for BR800 (3.69%). The hybrid BRS810 (bmr) had higher IVDMD and IVNDFD than its isogenic pair (BRS802) for all stages of maturity evaluated. The bmr-6 mutation increased the nutritional value of the sorghum-sudangrass hybrid through reduction in the NDF, ADF and ADL content and increases in CP, IVDMD and IVNDFD. Comparing the normal hybrids (non bmr), the hybrid BR800 stood out because of its lower ADF and ADL content and higher IVNDFD.

Brazilian crops are strongly affected by the root-knot nematode Meloidogyne incognita, which compromises food production and causes serious economic losses around the world. Synthetic nematicides are still some of the main control strategies for this pathogen, despite the high risk to human health and the environment. Therefore, sustainable biotechnology represents a viable alternative for nematode control. Plants of the Solanaceae family are present in several biomes and are a source of secondary metabolites of various chemical classes. In this context, the nematotoxic effect of crude aqueous root extracts (CAREs) of three Solanum species was investigated: Solanum americanum, S. subinerme and S. lycocarpum. CARE showed high nematicidal activity (94.6&plusmn;9.2% mortality, p &le; 0.001) against second-stage juveniles (J2) of M. incognita, even after heating to 50 &deg;C. These CAREs also inhibited hatching of juveniles (98.4&plusmn;0.7% of mortality, p &le; 0.001) in addition to presenting a mean lethal dose of 336 &mu;g ml-1. No toxic activity was observed against non-target organisms, such as fungi (Trichoderma harzianum and Trichoderma asperellum), yeast (Candida maltosa), nitrogen-fixing bacteria (Bradyrhizobium diazoefficiaens, B. japonicum), two strains of Azospirillum brasilense, AbV 5 and AbV 6 and Bacillus [2538 Ba]. Bioassay performed in a greenhouse demonstrated that CAREs of these species were effective in reducing the number of egg masses and galls (&gt; 85%, p &le; 0.0001), and did not show a phytotoxic effect on soybean seedlings. Our findings indicate that CAREs from plants of the Solanaceae family, especially S. lycocarpum, demonstrated nematotoxic activity on J2 and inhibited the hatching of Meloidogyne incognita eggs, representing an ecologically appropriate tool to control nematode infection in crops worldwide.