Lynn E. Sollenberger

Feed intake and lactation performance of dairy cows offered napiergrass supplemented with legume hay

Inadequate and low quality feed resources and declining soil fertility limit smallholder dairy production and crop yields in western Kenya. Integrating legumes into mixed crop–livestock smallholder production systems may improve feed resources and soil fertility. Mucuna [Mucuna pruriens var. utilis (L.) DC (Wright) Burck] and lablab [Lablab purpureus L. (Sweet)] are adapted legumes that can serve both functions, but data are limited which assess their use as supplements to cattle diets. The objective was to evaluate the potential benefits to dairy cow performance of feeding mucuna and lablab cv. Rongai hays as supplements to a basal diet of mature napiergrass [Pennisetum purpureum (Schum.) cv. Bana]. Eight multiparous Friesian cows were used in two 4×4 Latin squares. Treatments were (i) napiergrass basal diet fed alone (NG), (ii) napiergrass supplemented with mucuna hay (MH), (iii) napiergrass supplemented with lablab hay (LH), and (iv) napiergrass supplemented with a commercial dairy meal (CDM). The supplements were fed at iso-nitrogenous levels to meet the crude protein (CP) requirement of a 350-kg lactating cow producing 8–10 kg milk day−1. The MH, LH, and CDM treatments increased (P<0.01) total dry matter intake (TDMI) (130, 136, and 142 g kg−1 BW0.75, respectively) compared to NG (108 g kg−1 BW0.75). Supplementation also increased (P<0.01) apparent DM digestibility (587, 625, and 615 g kg−1, for MH, LH, and CDM, respectively) compared to NG (558 g kg−1) and daily yield of 4% fat corrected milk (FCM) (4.20, 4.15, and 5.21 kg, for MH, LH, and CDM, respectively) compared to NG (3.69 kg). Supplements increased mean body condition score, but they had no effect on body weight (BW) gain. Results show that milk production can be increased by supplementing a napiergrass-based diet with mucuna or lablab hay, highlighting the importance of integrating legumes into the low-input, mixed cropping systems in the tropics.

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.

Soil macronutrient distribution in rotationally stocked kikuyugrass paddocks with short and long grazing periods

Abstract Grazing management affects plant growth and animal production and it may influence the redistribution and cycling of nutrients excreted in dung and urine. Unfortunately, the soil component of pasture systems has received little attention in most grazing trials, and when considered has been evaluated on pastures smaller than those used commercially. A naturalized kikuyu (Pennisetum clandestinum Hochst. ex Chiov.) grassland was grazed by heifers (Bos taurus) for 2 yr in Experiment 1 to determine the effects of two rotational stocking methods (short vs. long grazing periods) on soil distribution of extractable nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S) in 4‐ha paddocks with natural shade. Additionally, in Experiment 2, kikuyugrass‐greenleaf desmodium (Desmodium intortum Urb.) paddocks were used to evaluate the effect of distance from waterers on soil nutrient distribution in rotationally stocked paddocks (long grazing periods) without shade in a cooler,...

Experimental approaches for evaluating the invasion risk of biofuel crops

There is growing concern that non-native plants cultivated for bioenergy production might escape and result in harmful invasions in natural areas. Literature-derived assessment tools used to evaluate invasion risk are beneficial for screening, but cannot be used to assess novel cultivars or genotypes. Experimental approaches are needed to help quantify invasion risk but protocols for such tools are lacking. We review current methods for evaluating invasion risk and make recommendations for incremental tests from small-scale experiments to widespread, controlled introductions. First, local experiments should be performed to identify conditions that are favorable for germination, survival, and growth of candidate biofuel crops. Subsequently, experimental introductions in semi-natural areas can be used to assess factors important for establishment and performance such as disturbance, founder population size, and timing of introduction across variable habitats. Finally, to fully characterize invasion risk, experimental introductions should be conducted across the expected geographic range of cultivation over multiple years. Any field-based testing should be accompanied by safeguards and monitoring for early detection of spread. Despite the costs of conducting experimental tests of invasion risk, empirical screening will greatly improve our ability to determine if the benefits of a proposed biofuel species outweigh the projected risks of invasions.

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.

ON-FARM EXPERIMENTS WITH MAIZE-MUCUNA SYSTEMS IN THE LOS TUXTLAS REGION OF VERACRUZ, MEXICO. I. MUCUNA BIOMASS AND MAIZE GRAIN YIELD

SUMMARY Maize (Zea mays)-mucuna (Mucuna pruriens )s ystems have been promoted to the smallholder farmers of the Los Tuxtlas region of southeastern Veracruz, Mexico. To determine on-farm performance, an agronomic assessment was conducted in 1995–97 replicating farmer conditions in four fields. Treatments were firstand second-season maize with first-season mucuna (system Zm-Mp/Zm), first-season maize with first- and second-season mucuna (system Zm-Mp/Mp), second-season maize following first-season mucuna (system Mp/Zm), and first- and second-season maize, no mucuna control. Data on mucuna biomass amount and quality as well as maize yield, yield components, and nutrient status were collected. Highest mucuna biomass was obtained in system Mp/Zm (leaf-stem-mulch biomass in 1996/97, 7.34 t ha−1, 147 kg ha−1 N), followed by systems Zm-Mp/Mp (5.06 t ha−1, 101 kg N ha−1 )a nd Zm-Mp/Zm (2.75 t ha−1 ,5 0 kg N ha −1 ). Second-season maize yield was increased over that of the control by 45–58 % (0.15–0.23 t ha −1 )i n system Zm-Mp/Zm and by 118 % (0.60 t ha −1 )i n system Mp/Zm. Mucuna did not increase first-season maize yield. Climatic constraints make second-season maize production risky and yield increases due to mucuna are low in absolute terms, perhaps not offsetting labour costs (systems Zm-Mp/Zm and Mp/Zm) or loss of first-season maize (Mp/Zm).

MACRONUTRIENT, SOIL ORGANIC CARBON, AND EARTHWORM DISTRIBUTION IN SUBTROPICAL PASTURES ON AN ANDISOL WITH AND WITHOUT LONG-TERM FERTILIZATION

Pasture fertilization affects plant growth and animal production, and it may influence the redistribution and cycling of nutrients excreted in dung and urine. Kikuyugrass (Pennisetum clandestinum Hochst. ex Chiov.) pastures on a high organic carbon (C) Typic Hydrudand soil with and without (control) annual nitrogen (N) and periodic phosphorus (P) and potassium (K) fertilizations were stocked with Hereford and crossbred cattle (Bos taurus) for 33 years. The pastures were divided into 1.2-ha paddocks for rotational stocking after the 15th year. Selected fertilized paddocks that were uniformly managed over the years were paired with control paddocks to determine management effects on soil organic C; soil and plant N, P, and K; and earthworm distribution. Responses were assessed using a zonal sampling procedure based on distance from the waterer because the paddocks lacked shade. Soil organic C, organic N, and organic P did not statistically differ between managements or zones in any horizon. Relative to the control, however, an apparent recovery of 25% of the total N applied to the fertilized paddocks was obtained as soil organic N within the 80 cm profile depth examined. Inorganic N (NH4-N + NO3-N) was greater in the Ap1 and Bw1 horizons of fertilized paddocks, and there was a trend in the Ap1 horizon toward greater concentrations within 15 m of the waterer. Additionally, substantial inorganic P accumulated within 30 m of the waterers in the Ap1 and Bw1 horizons of fertilized paddocks while minimal P accumulation occurred within 15 m of the waterer in control paddocks. The magnitude of K accumulation near waterers was also considerably greater in the Ap1 horizon of fertilized paddocks. It is suggested that fertilization increases the magnitude of P and K accumulation near waterers due to the combination of increased forage P and K concentrations and pasture carrying capacity. Management and zone effects for forage N, P, and K tended to follow patterns relatively similar to the soil Ap1 horizon data for the inorganic forms of these nutrients. Earthworm populations did not differ among zones, but populations in fertilized paddocks were double those of control paddocks.

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.

Grazing management and supplementation effects on forage and dairy cow performance on cool-season pastures in the southeastern United States

Cool-season annual forages provide high-quality herbage for up to 5 mo in the US Gulf Coast states, but their management in pasture-based dairy systems has received little attention. Objectives of this study were to evaluate pasture and animal responses when lactating Holstein cows (n=32, mean DIM=184±21) grazed either N-fertilized rye (Secale cereale L.)-annual ryegrass (Lolium multiflorum Lam.) mixed pastures or rye-annual ryegrass-crimson clover (Trifolium incarnatum L.)-red clover (Trifolium pratense L.) pastures at 2 stocking rates (5 vs. 2.5 cows/ha) and 2 rates of concentrate supplementation [0.29 or 0.40 kg of supplement (as is)/kg of daily milk production]. Two cows paired by parity (one multiparous and one primiparous) were assigned randomly to each pasture. The 2 × 2 × 2 factorial arrangement of treatments was replicated twice in a completely randomized design. Forage mixture and supplementation rate did not affect milk production during three 28-d periods. Greater milk production occurred at the low (19.7 kg/d) than the high (14.7 kg/d) stocking rate during periods 2 and 3, but production was similar during period 1. Despite lower production per cow, milk production per hectare was generally greater at the high stocking rate (81.6 vs. 49.5 kg/ha). Generally, greater pregraze herbage mass on pastures at the lower stocking rate (1,400 vs. 1,150 kg/ha) accounted for greater herbage allowance. Both forage (8.0 vs. 5.9 kg/d) and total (14.1 vs. 11.6) organic matter intake were greater at the low stocking rate. Cows fed less supplement had greater forage organic matter intake (8.0 vs. 6.1 kg/d). Greater herbage mass was associated with the greater intake and subsequent greater milk production. Differences in forage nutritive value, blood metabolites and milk composition, although showing some response to treatments, may not be of sufficient magnitude to affect choice of pasture species or other management practices. Animal performance was not improved by adding clovers to mixed cool-season grass pastures like those in this study. Stocking rate had a major effect on pasture and animal performance. During the cool season, supplementation with concentrates should be planned based on estimated energy intake from forages to achieve optimum milk production and ensure maintenance of body condition.

Managing harvest of 'Tifton 85' bermudagrass for production and nutritive value.

Abstract Harvest management is critical in hay or greenchop systems to sustain high yields of superior nutritive value. ‘Tifton 85’ bermudagrass [ Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy] is a high-quality, high-yielding, warm-season perennial grass that dairy producers are using as hay, haylage, and/or pasture. Morphological features of this plant compared to other grasses used in the region suggest the adoption of a more conservative harvest stubble may be needed. During 2007 and 2008, different harvest intervals (21, 24, 27, and 35 days) and stubble heights (3 and 6 inches) were compared using established Tifton 85 bermudagrass fields. Results suggest that highest yields occur with larger interval between harvests (35 days) and when shorter stubble heights (3 inches) are used. Nevertheless, shorter stubble heights (3 inches) were associated with greater weed encroachment and are generally not recommended. Data show that greater nutritive value can be achieved with defoliation at 24- to 27-day intervals to a 6-inch stubble.