J. M. B. Vendramini

Effects of preshipping management on measures of stress and performance of beef steers during feedlot receiving

Over 2 yr, a total of 96 steers (approximately 7 mo of age) were allocated to 1 of 4 weaning management strategies: 1) control: weaned on the day of shipping; 2) creep-fed: allowed free-choice access to concentrate before weaning and shipping; 3) preweaned: weaned and provided supplemental concentrate on pasture before shipping; and 4) early-weaned: weaned at 70 to 90 d of age and kept on pasture. On the day of shipping, steers were loaded together onto a commercial livestock trailer and transported 1,600 km over 24 h before being received into the feedlot. At the feedlot, steers were penned by treatment (4 pens/treatment) and provided access to free-choice hay and concentrate in separate feeding spaces. Samples of blood were collected on d 0, 1, 4, 8, 15, 22, and 29 relative to shipping. Steer performance was assessed over the receiving period, including DMI of hay and concentrate, ADG, and G:F. Predetermined contrasts included control vs. early-weaned, creep-fed vs. preweaned, and control vs. creep-fed and preweaned. Overall ADG was greater (P < 0.01) for early-weaned vs. control steers (1.39 vs. 0.88 kg). In wk 1, early-weaned steers consumed more concentrate and less hay compared with control steers (P < 0.03), and preweaned steers consumed more concentrate (P < 0.01) but a similar amount of hay (P = 0.75) compared with creep-fed steers. Average DMI was greater for preweaned compared with creep-fed steers (2.84 vs. 2.50% of BW; P = 0.01) and tended to be greater for early-weaned compared with control steers (2.76 vs. 2.50% of BW; P = 0.06). Feed efficiency of early-weaned steers was greater than that of control steers (G:F = 0.17 vs. 0.12; P < 0.01) but similar for preweaned compared with creep-fed steers (P = 0.72). Plasma ceruloplasmin concentrations were less (P < 0.05) in control vs. early-weaned steers on d 0, but increased sharply after shipping and were greater in control vs. early-weaned steers on d 15 and 22 (P < 0.05). Creep-fed steers also experienced greater (P < 0.05) plasma ceruloplasmin concentrations than preweaned steers on d 29. These data suggest that early-weaned steers have improved performance in the feedlot compared with steers weaned directly before transport and feedlot entry. Differences in preshipping management appear to significantly affect measures of the acute phase protein response in steers.

Effects of energy supplementation frequency and forage quality on performance, reproductive, and physiological responses of replacement beef heifers.

The objective of this study was to compare performance, physiological, and reproductive responses of beef heifers consuming forages differing in nutritional quality and offered a low-starch energy supplement at 2 different frequencies. Forty-eight Brahman × British heifers (initial age = 294 ± 3 d) were allocated into 1 of 16 drylot pens (3 heifers/pen) which were randomly assigned to receive, in a 2 × 2 factorial arrangement of treatments: 1) low-quality hay [LQ; stargrass (Cynodon nlemfuensis) with 8% CP and 81% NDF, DM basis] and daily supplementation (S7); 2) LQ and supplementation 3 times weekly (S3); 3) medium-quality hay [MQ; bermudagrass (C. dactylon) with 12% CP and 74% NDF, DM basis] and S7; and 4) MQ and S3. Throughout the study (d 0 to 120), hay was offered in amounts to ensure ad libitum access, and a supplement based on soybean hulls and wheat middlings was offered at weekly rates of 15.8 and 7.9 kg/heifer (DM basis) for LQ and MQ, respectively. Forage and total DMI were evaluated daily, from d 20 to 26, d 34 to 40, and d 48 to 54. Blood samples were collected weekly for determination of plasma progesterone to evaluate puberty attainment. Blood samples were also collected daily, from d 13 to 16, d 27 to 30, d 41 to 44, and d 55 to 58 for determination of plasma urea nitrogen (PUN), glucose, insulin, IGF-I, and NEFA. On d 60, heifers were reallocated by treatment into 4 paddocks and exposed to Angus bulls (1:12 bull:heifer ratio) until d 120. Date of conception was estimated retrospectively by subtracting gestation length (286 d) from the calving date. Heifers receiving S7 had similar (P = 0.52) ADG compared with S3 heifers (0.27 vs. 0.25 kg/d). Heifers provided S7 had less daily variation in hay DMI and plasma concentrations of glucose, NEFA, and IGF-I compared with S3 cohorts (supplementation frequency × day interaction; P < 0.01). Similarly, heifers offered MQ and LQ and receiving S7 had less daily variation in total DMI, energy and protein intake, and plasma concentrations of PUN compared with heifers offered MQ and LQ and receiving S3 (hay quality × supplementation frequency × day interaction; P < 0.01). Attainment of puberty and pregnancy were hastened in S7 heifers compared with S3 heifers (supplementation frequency × week interaction; P < 0.02). Therefore, reproductive development of beef replacement heifers consuming diets based on low- and medium-quality forages are enhanced when low-starch energy supplements are offered daily instead of 3 times weekly.

Nutritive Value and Fermentation Parameters of Warm-Season Grass Silage1

The objective of this study was to investigate the nutritive value and fermentation characteristics of different species of warm-season grass silages not treated or treated with bacterial inoculants in the summer and fall. Nine forage species and cultivars, ‘Merkeron’ elephantgrass (Pennisetum purpureum Schumach.), ‘Mulato’ (Brachiaria sp.), ‘Argentine’ bahiagrass (Paspalum notatum Flugge), ‘Florico’ stargrass (Cynodon nlemfuensis Vanderyst), ‘Tifton 85’ bermudagrass (Cynodon sp.), ‘Jiggs’ bermudagrass (Cynodon dactylon L.), ‘Coastcross-2’ bermudagrass (Cynodon dactylon L.), ‘Florakirk’ bermudagrass (Cynodon dactylon L.), and ‘Floralta’ limpograss [Hemarthria altissima (Poir.) Stapf & C.E. Hubbard], were not treated (control) or treated with a microbial inoculant solution (Si-All, Alltech Inc., Nicholasville, KY) in a split-plot arrangement with 3 replicates. In the summer, NDF concentration was greater for the bermudagrasses than the average of other species (68 vs. 65%). Mulato had the lowest NDF concentration (57%) and the greatest in vitro true digestibility concentration (63%) compared with other treatments. Limpograss silage had the lowest pH (6.5) and the greatest lactic acid concentration (2.6%). Conversely, elephantgrass silage had decreased lactic acid concentration (0.1%) and greater pH (8.3) compared with the other species. Inoculated silages had lesser lactic acid concentrations than the control (0.62 vs. 1.84%). In the fall, elephantgrass had less in vitro true digestibility (60 vs. 65%) and NDF digestibility (44 vs. 52%) than the other species. Elephantgrass silage pH was less (7.2 vs. 8.8) and concentrations of total VFA (4.6 vs. 0.4%), lactic acid (1.5 vs. 0.2%), and acetic acid (2.1 vs. 0.2%) were greater than in the bermudagrasses. There was no effect of the inoculant on the nutritive value and silage fermentation variables in the fall.

Effects of calf weaning age and subsequent management system on growth and reproductive performance of beef heifers.

Brahman × British crossbred heifers (n = 40 and 38 heifers in yr 1 and 2, respectively) were used to evaluate the effects of calf weaning age and subsequent management system on growth and reproductive performance. On d 0, heifers were ranked by BW (89 ± 16 kg) and age (72 ± 13 d) and randomly assigned to a conventional management group that was normally weaned on d 180 (NW; n = 10 heifers annually) or early weaned (EW) on d 0 and 1) limit fed a high-concentrate diet at 3.5% of BW (as fed) in drylot until d 180 (EW180; n = 10 heifers annually), 2) limit fed a high-concentrate diet at 3.5% of BW (as fed) in drylot until d 90, then grazed on Bahiagrass pastures until d 180 (EW90; n = 10 heifers annually), or 3) grazed on annual ryegrass pastures until d 60 (yr 1; n = 10 heifers) or 90 (yr 2; n = 8 heifers), then on Bahiagrass pastures until d 180 (EWRG). On d 180, all heifers were grouped by treatment and rotated on Bahiagrass pastures until d 390. Grazing heifers were supplemented at 1.0% BW until d 180 and at 1.5% BW from d 180 to 390. From d 0 to 90, EW180 and EW90 heifers were heavier (P ≤ 0.02) than NW and EWRG heifers, whereas NW heifers tended (P = 0.09) to be heavier on d 90 than EWRG heifers. In yr 1 and 2, EW180 heifers were heaviest (P < 0.0001) on d 180. In yr 1, EWRG heifers were lightest (P < 0.0001), whereas EW90 and NW heifers had similar BW (P = 0.58). Conversely, EW90, EWRG, and NW heifers achieved similar BW on d 180 of yr 2 (P ≥ 0.18). Positive correlations were detected (P ≤ 0.05) between liver IGF-1 mRNA abundance on d 90 and ADG from d 0 to 90 and between liver IGF-1 mRNA abundance on d 180 and ADG from d 90 to 180. The EW180 heifers were youngest (P ≤ 0.01) at puberty. From d 260 to 340, the percentage of pubertal heifers was greater (P ≤ 0.03) for EW90 vs. NW heifers but did not differ (P ≥ 0.15) between EWRG and NW heifers. The ADG from d 0 to 90 and the plasma IGF-1 on d 90 and 180 explained approximately 34% of the variability in age at puberty. In summary, the EW90 and EW180 heifer management systems evaluated in this study altered the BW at the time of NW and were good alternatives for anticipating puberty achievement compared to NW heifers.

Effects of Supplementation Strategies on Performance of Early-Weaned Calves Raised on Pastures

ABSTRACT The objective of these experiments was to investigate the effects of supplementation and grazing strategies on the performance of early-weaned calves grazing cool-season and warm-season grasses in Florida. In Exp. 1, 40 calves were early-weaned (92 ± 15 d of age) and randomly allocated to 8 ryegrass (Lolium multiflorum) pastures (January to May) and then moved onto 8 stargrass (Cynodon nlemfuensis) pastures (May to August). Two supplement treatments (1.0% BW) were randomly allotted to pastures (4 pastures/treatment), consisting of 1) soybean hulls, or 2) a blend of soybean hulls and cottonseed meal (80:20). Supplement treatment did not impact ADG during ryegrass grazing; however, calves grazing stargrass and receiving supplemental soybean hulls + cottonseed meal had greater ADG than calves receiving soybean hulls alone. In Exp. 2, 24 early-weaned calves (89 ± 20 d of age) were randomly assigned 1 of 2 management treatments from January to April (3 pastures/treatment and 4 calves/pasture). Treatments consisted of 1) bahiagrass (Paspalum notatum) + 2.0% BW supplementation, or 2) ryegrass + 1.0% BW supplementation. Supplements were an 80:20 blend of soybean hulls and cottonseed meal. Herbage mass and allowance were similar among treatments, but ryegrass had greater nutritive value than both the bahiagrass and supplement. Consequently, calves grazing ryegrass had greater ADG. In conclusion, the addition of cottonseed meal to a soybean hull supplement increased performance of early-weaned calves grazing summer warm-season grasses, but not while grazing winter ryegrass. In addition, early-weaned calves grazing warm-season grasses during the winter had decreased performance when compared with calves grazing ryegrass, despite increased supplementation.

Environmental impacts and nutrient recycling on pastures grazed by cattle

Grasslands are being replaced by urbanization and more profitable agricultural activities around the world. Producers may be faced with land constraints and need to consider intensification of the remaining grasslands as a means of maintaining overall production on a decreasing land resource. However, intensification of the grazing system is usually associated with greater nutrient inputs, including those from commercial fertilizers and supplement fed to animals. Excessive loading of nutrients in intensive grazing systems via fertilizer and animal wastes can cause nutrient buildup in the soil and subsequent water quality problems. Surface runoff and leaching of nutrients are the two major process affecting water quality. Nitrogen and P represent major nutrient concerns as related to water quality. Increased nitrate concentrations render groundwater unsuitable for drinking and can cause serious health issues for humans. Excessive N and P concentrations may contribute to eutrophication of streams and lakes. Maximizing efficiency of nutrient recycling through the soil-forage-animal system minimizes off-site nutrient transport and decreases production costs by reducing the quantity of commercial fertilizer needed. Management strategies to reduce soil and water contamination include refining the balance of nutrient inputs from feeds and fertilizers as well as accounting for the nutrients recycled through the decomposition of plant litter and animal wastes. Current interest in the development and adoption of efficient and sustainable agriculture systems has led forage researchers to amplify the scope of grasslands research by increasing multidisciplinary efforts. There is an increased interest in quantifying the impacts of forage-animal management strategies on the environment, with the goal of developing economically viable best management practices that result in optimum forage production and profitability, while protecting the environment. Furthermore, these best management practices will supply reliable information for future environmental policies that may be adopted by governmental agencies.

USING TISSUE ANALYSIS AS A TOOL TO PREDICT BAHIAGRASS PHOSPHORUS FERTILIZATION REQUIREMENT

Tissue analysis in combination with soil testing has been recently incorporated in the fertilization recommendations for bahiagrass in Florida; however, limited research is available to validate the proposed critical tissue phosphorus (P) level. A greenhouse experiment was conducted to identify the critical minimum tissue P concentration below which bahiagrass dry matter (DM) yield is impacted. Treatments consisted of three nitrogen (N) rates (0, 50, and 100 kg N ha−1), four P rates (0, 20, 40, 60 kg P2O5 ha−1) and two clipping intervals (28 and 56 d). Bahiagrass yields and tissue P increased in response to P application. Phosphorus uptake showed a quadratic response to P rates when N was applied. Phosphorus recovery increased linearly as P rate increased. Root mass responded to P, even at the smallest (20 kg ha−1) rate. Data indicated that tissue P concentration of 1.3 (±0.2) g kg−1 can be used as an indicator of bahiagrass P deficiency.

Phosphorus management and water quality problems in grazingland ecosystems.

Phosphorus management in grazingland ecosystems represents a major challenge of agronomic and environmental importance. Because of the extensive acreage occupied by grazinglands, decisions concerning pasture fertilization and nutrient management in forage-based livestock systems are crucial to both farmers and regulatory agencies. The purpose of this paper is to provide an overview of the literature relevant to pasture P fertilization and the potential impacts on water quality. There continue to be uncertainties regarding interrelationships between pasture management and water quality issues. Despite the extensive body of literature on nutrient transport from grazinglands, limited information is available on the relationships between land use, transport potential, water management, and climatic conditions affecting nutrient losses at a watershed scale. As agriculture continues to modernize and intensify, public concerns about the impacts of plant nutrients on environmental quality will likely increase. Managing water quality protection and profitable agriculture will be a major challenge for the next generations.

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.

Management of Perennial Warm-Season Bioenergy Grasses. II. Seasonal Differences in Elephantgrass and Energycane Morphological Characteristics Affect Responses to Harvest Frequency and Timing

Elephantgrass (Pennisetum purpureum Schum.) and energycane (Saccharum spp. interspecific hybrid) are perennial C4 grasses with potential for use as bioenergy feedstocks. Their biomass production has been quantified, but differences in plant morphology and the relationship of morphology with biomass harvested and plant persistence are not well understood. The objective was to quantify monthly changes in morphological characteristics of elephantgrass (cv. Merkeron and breeding line UF1) and energycane (cv. L 79-1002) and relate these changes to biomass accumulation and plant responses to defoliation. All were evaluated monthly during full-season growth or when defoliated once in mid-season. Merkeron and UF1 elephantgrass generally showed similar morphological characteristics. Relative to energycane, elephantgrass had fewer tillers early in the growing season, less seasonal variation in tiller number, greater tiller mass and maximum leaf area index (LAI), and earlier spring development of LAI. Energycane showed slower leaf area development in spring, lower maximum LAI, and shorter period of increasing tiller mass and canopy height during the growing season relative to UF1. Elephantgrass had greater incidence of lodging than energycane when exposed to high wind, likely due to greater elephantgrass tiller mass. Morphological characteristics of tall-growing bioenergy grasses help to explain differences among them in biomass production and plant persistence responses to defoliation.