Modifying the NRC weight gain model to estimate daily gain for stockers grazing bermudagrass in the southern United States

Abstract The energy requirements, feed intake, and performance of grazing animals vary daily due to changes in weather conditions, forage nutritive values, and plant and animal maturity throughout the grazing season. Hence, realistic simulations of daily animal performance can be made only by the models that can address these changes. Given the dearth of simple, user-friendly models of this kind, especially for pastures, we developed a daily gain model for large-frame stockers grazing bermudagrass [Cynodon dactylon (L.) Pers.], a widely-used warm-season perennial grass in the southern United States. For model development, we first assembled some of the classic works in forage-beef modeling in the last 50 years into the National Research Council (NRC, 1984) weight gain model. Then, we tested it using the average daily gain (ADG) data obtained from several locations in the southern United States. The evaluation results showed that the performance of the NRC model was poor as it consistently underpredicted ADG throughout the grazing season. To improve the predictive accuracy of the NRC model to make it perform under bermudagrass grazing conditions, we made an adjustment on the model by adding the daily departures of the modeled values from the data trendline. Subsequently, we tested the revised model against an independent set of ADG data obtained from eight research locations in the region involving about 4,800 animals, using 30 years (1991-2020) of daily weather data. The values of the various measures of fit used, namely the Willmott index of 0.92, the modeling efficiency of 0.75, the R 2 of 0.76, the root mean square error of 0.13 kg d -1, and the prediction error relative to the mean observed data of 24% demonstrated that the revised model mimicked the pattern of observed ADG data satisfactorily. Unlike the original model, the revised model predicted more closely the ADG value throughout the grazing season. The revised model may be useful to accurately reflect the impacts of daily weather conditions, forage nutritive values, seasonality, and plant and animal maturity on animal performance.

Download Full-text

Animal performance, production, and quality of Tanzania grass fertilized with nitrogen

Semina Ciências Agrárias ◽

10.5433/1679-0359.2017v38n6p3861 ◽

2017 ◽

Vol 38 (6) ◽

pp. 3861 ◽

Cited By ~ 3

Author(s):

Ulysses Cecato ◽

Josmar Almeida Junior ◽

Fabíola Cristine de Almeida Rego ◽

Sandra Galbeiro ◽

Wagner Paris ◽

...

Keyword(s):

Weight Gain ◽

Chemical Composition ◽

Crude Protein ◽

Average Daily Gain ◽

Live Weight ◽

Neutral Detergent Fiber ◽

Stocking Rate ◽

Animal Performance ◽

Live Weight Gain ◽

Daily Gain

This study aimed to assess forage production, animal performance, and the chemical composition of Tanzania grass pasture fertilized with 50, 100, 200, and 400 kg ha-1 of nitrogen. The variables analyzed were: leaf mass, daily accumulation rate, leaf/stem ratio, average daily gain, stocking rate, live weight gain per unit of area crude protein, neutral detergent fiber, and in vitro dry matter digestibility of leaves. The pasture management maintained the pasture height at 50 cm by using a continuous grazing method with the adjustment of stocking rate. The experimental design was a randomized block with three replicates. The leaf mass increased linearly in response to nitrogen, with an increase of 1003 kg (34%) observed between a nitrogen content of 50 and 400 kg ha-1. Nitrogen did not affect the average daily gain, but increased the stocking rate and live weight gain ha-1. The value of crude protein and neutral detergent fiber were higher with increased nitrogen levels, whereas the leaf digestibility did not affect nitrogen use. The comparison of 50 and 400 kg ha-1 levels indicated that there was an average increase of 19.2% in the leaf crude protein. The increased application of nitrogen fertilizer in Tanzania grass improved the chemical composition and animal performance; with regard to studied variables, the dose of 200 kg ha-1 resulted in the greatest improvement.

Download Full-text

Post-hurricane forest management responses in the southern United States

Journal of Emergency Management ◽

10.5055/jem.2009.0038 ◽

2009 ◽

Vol 7 (6) ◽

pp. 35

Author(s):

Pete Bettinger, PhD ◽

Krista L. Merry, MS ◽

Jeffrey Hepinstall, PhD

Keyword(s):

United States ◽

Forest Management ◽

Forest Health ◽

Storm Surges ◽

Weather Conditions ◽

The United States ◽

Southern United States ◽

Service Needs ◽

Strong Winds ◽

Social Recovery

Although people living along the southeastern and Gulf coasts of the United States may have limited experience dealing with major hurricane damage, hurricanes are imminent and pose potentially dire consequences to forest resources. In addition to understanding the physical and biological reactions of forests to extreme weather conditions, there are a number of managerial responses that should be considered based on this past experience. This article presents a summary of the more pertinent forest management responses, and where appropriate, highlights situations where these were beneficial to the overall (economic, ecological, social) recovery effort. Management responses address not only the immediate needs for clearing roads and restoring basic service needs, but also the longer-term issues related to timber salvage, reforestation, forest health, and fire danger. The damage from strong winds and storm surges may also result in serious consequences for ecological values. However, challenges and issues related to the restoration of forests and forest-related values may require several years to address. Therefore, the objective of this review article is to provide a summary of the experiences of forest land managers, researchers, and emergency planners who have directly responded to severe storms affecting the southern United States.

Download Full-text

Effects of grazing system on production and parasitism of dairy breed heifers and steers grazing wet marginal grasslands

Animal Science ◽

10.1079/asc200520 ◽

2006 ◽

Vol 82 (2) ◽

pp. 201-211 ◽

Cited By ~ 3

Author(s):

T. Kristensen ◽

S. M. Thamsborg ◽

H. R. Andersen ◽

K. Søegaard ◽

A. L. Nielsen

Keyword(s):

Organic Matter ◽

Weight Gain ◽

Live Weight ◽

Live Weight Gain ◽

Grazing Season ◽

Pasture Quality ◽

Marginal Areas ◽

Grazing System ◽

Parasite Infections ◽

Daily Gain

AbstractProduction and endoparasitism of first grazing season Holstein heifers and steers were investigated over two grazing seasons. Studies were conducted on low-lying peaty soil. In year 2000, 40 animals were included in a 2×2 factorial, replicated experiment with two sexes (steers v. heifers) and two stocking rates (SR): normal v. low (840 v. 420 kg live weight per ha at turn-out) in a set stocking grazing system. Mean grass heights over the entire season were 6·3±4·8 cm (mean±s.d.) at normal SR and 9·8±6·1 cm at low SR. Mean daily live-weight gain during grazing was significantly (P<0·001) lower at normal SR (256±147 g) compared with low (468±142 g) but sex did not significantly affect the daily gain. Serum pepsinogen levels, indicating uptake of gastric nematodes, were higher at normal SR and consistently higher in steers compared with heifers, although not significantly. In 2001 the experiment included 80 animals in a 2×2 factorial experiment with two sexes (steers v. heifers), two grazing systems (set stocking and two-paddock rotation) and four replicates. Pasture quality was low, 570 g digestible organic matter per kg organic matter and 139 g crude protein per kg dry matter on average, independent of grazing system. Mean daily live-weight gain was not significantly affected by grazing system. A tendency (P=0·07) to lower daily gain for the heifers than for steers was observed (427±161 g v. 474±138 g). Lower levels of pasture contamination with parasites were observed in the paddocks without grazing up to mid July but otherwise rotation did not prevent parasite infections. It is concluded that first grazing season steers and heifers have the same potential for growth when grazing marginal areas with low pasture quality. Set stocking or the two-paddock rotation scheme did not affect productivity or level of parasite infection at the end of season. Parasite infections became a problem at high SR. SR is an important factor for both daily live-weight gain per animal and total production per ha. However, due to the very heterogeneous structure of marginal areas there is a need for other indicators than kg live weight per ha at turn-out in order to define a clear relationship between stocking rate and production.

Download Full-text

Evaluation of Sequential Fungicide Spray Programs for Control of Soybean Rust

Plant Health Progress ◽

10.1094/php-2009-0402-01-rs ◽

2009 ◽

Vol 10 (1) ◽

pp. 23 ◽

Cited By ~ 5

Author(s):

Edward J. Sikora ◽

Dennis P. Delaney ◽

Mary A. Delaney ◽

Kathy S. Lawrence ◽

Malcomb Pegues

Keyword(s):

United States ◽

Relative Effectiveness ◽

Weather Conditions ◽

Soybean Rust ◽

Yield Potential ◽

Southern United States ◽

Crops Yield

Soybean rust (SBR), caused by the fungus Phakopsora pachyrhiza, has been a recurring problem for soybean growers in the southern United States. In some cases, growers in this region have followed a fungicide spray program consisting of two fungicide applications to protect their crop from the disease. Our study was conducted to determine how various sequential fungicide spray programs perform under the relatively high SBR pressure found in Alabama. Results from this study suggest that there are significant differences in the relative effectiveness of a program based on products used and the sequence in which they are applied. Factors such as recent weather conditions, proximity to sources of SBR, cost of available products, and an estimate of a crops yield potential should be considered when choosing a fungicide program. Accepted for publication 10 February 2009. Published 2 April 2009.

Download Full-text