Effects of genotype, wilting, and additives on the nutritive value and fermentation of bermudagrass silage.

Bermudagrass is the main warm-season grass species used for livestock production in the southeastern United States; however, when it is ensiled, the silage fermentation parameters are often less than desirable. The objective of this study was to investigate the effects of management practices on the nutritive value and fermentation characteristics of bermudagrass silage. In Exp. 1, treatments were the factorial combinations of 2 bermudagrass genotypes, 'Jiggs' () and 'Tifton 85' ( sp.), 4 additives, and 2 DM concentrations at ensiling. The additives were 1) untreated control (deionized water), 2) Ecosyl, 3) B500, or 4) sugarcane molasses. The 2 DM concentrations at ensiling were low DM (22% DM) or high DM (53% DM). Treatments were replicated 3 times in a completely randomized design. Silage treated with molasses had a lesser ( < 0.05) pH and greater ( < 0.01) lactate concentrations than the control, Ecosyl, and B500 in silage with low DM concentrations and greater ( < 0.01) in vitro true digestibility (IVTD) and lesser ( < 0.01) ADF concentrations than the other treatments at either DM concentration. Silage treated with B500 had the greatest ( < 0.01) aerobic stability, whereas that treated with molasses had the least aerobic stability. However, all treatments presented long aerobic stability (≥150 h). Jiggs had lesser ( < 0.01) ADF and NDF and NDF digestibility (NDFD) concentrations than Tifton 85 and Tifton 85 had greater ( < 0.01) IVTD than Jiggs in the silage with a high DM concentration. In Exp. 2, Jiggs silage treated with either molasses (20 g molasses [DM]/kg forage [as-fed basis]) or nothing (control, untreated silage) was fed to 16 beef heifers ( sp.) in individual drylot pens in a completely randomized design with 8 replicates for voluntary DMI, in vivo apparent DM digestibility, and NDFD evaluations. There were no differences ( = 0.36) among treatments in NDFD; however, there was a trend ( < 0.08) for greater in vivo apparent DM digestibility and DMI in heifers fed the molasses-treated silage. Microbial inoculants had decreased effects on Jiggs and Tifton 85 bermudagrass silage ensiled at a low DM concentration; however, adding molasses was an effective management practice to improve its nutritive value and fermentation characteristics.

Stocking rate and monensin supplemental level effects on growth performance of beef cattle consuming warm-season grasses.

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.

Performance of beef cows and calves fed different sources of rumen-degradable protein when grazing stockpiled limpograss pastures.

Two experiments evaluated the effects of different sources of RDP on forage characteristics, animal performance, and ruminal and blood parameters of beef cattle grazing stockpiled limpograss (Hemarthria altissima) from January to May 2011 and 2012. In Exp. 1, 24 mature lactating beef cows and their respective calves were allocated to 8 stockpiled limpograss pastures (3 pairs/pasture). Treatments were 2 different sources of RDP, urea or cottonseed (Gossypium spp.) meal (CSM), distributed in a completely randomized design with 4 replicates. Feather meal and corn (Zea mays) meal were added to the urea treatments to balance RUP and energy. Treatments were mixed in sugarcane (Saccharum officinarum) molasses, which resulted in 3 kg DM/cow per day of supplement. There were no differences (P > 0.10) in herbage mass (HM; 3,200 ± 400 kg DM/ha), herbage allowance (HA; 1.9 ± 0.2 kg DM/kg of BW), CP (5.2 ± 0.2%), and in vitro digestible organic matter (IVDOM; 47 ± 0.5%) concentrations. There was a decrease (P < 0.10) in HM (from 4,100 to 2,600 kg/ha), IVDOM (from 46 to 39.9%), and HA (from 2.5 to 1.4 kg DM/kg BW) from January to March. Cow ADG (0.23 ± 0.08 kg/d), BCS (4.6 ± 0.2), milk yield (7.0 ± 0.4 kg/d), and plasma urea nitrogen (PUN; 16.1 ± 0.8 mg/dL) and calf ADG (0.71 ± 0.05 kg/d) were similar (P > 0.10) among treatments. Sixteen cow-calf pairs were moved to 8 drylot pens after Exp. 1, maintained on the same treatment, and evaluated for forage and total DMI. There was no difference in forage (P = 0.16; 2.1 ± 0.1% BW) and total DMI (P = 0.12; 2.5 ± 0.1% BW) between treatments. In Exp. 2, 2 rumen-cannulated steers were used in a 2 × 2 Latin square design, replicated in 2011 and 2012, to test the effects of the same treatments on rumen fluid and blood parameters. There was no difference (P > 0.10) in ruminal NH3-N (12.9 ± 0.3 mg/dL), pH (6.5 ± 0.1), propionic acid (25 ± 2.2 mol/100 mol), acetic acid (69.2 ± 2.9 mol/100 mol), and butyric acid (4.5 ± 0.5 mol/100 mol) as well as branched-chain VFA (1.3 ± 2.2 mol/100 mol) concentrations in the rumen. In addition, there was no difference (P = 0.91) in PUN (7.9 ± 0.3 mg/dL) concentration between treatments. Therefore, urea can be as effective as CSM as the main source of RDP in the molasses-based supplement offered to mature lactating beef cows grazing stockpiled limpograss pastures.