Parametrization of the Davis Growth Model using data of crossbred Zebu cattle.

The system of differential equations proposed by Oltjen et al. [1986, named Davis Growth Model (DGM)] to represent cattle growth has been parameterized with data from Bos taurus (British) and Bos indicus (Nellore) breeds. The DGM has been successfully used for simulation and decision support in the United States. However, the effect of about 30 years of genetic improvement and the use of different breeds may affect the model parameter values, which also may need to be re-estimated for crossbred animals. The aim of this study was to estimate parameter values and confidence intervals for the DGM with growth and body composition data from Zebu crossbred animals. Confidence intervals and asymptotic distribution were generated through nonparametric bootstrap with data from a field experiment conducted in Brazil. The parameters showed normal probability distribution for most scenarios. The rate constant for deoxyribonucleic acid (DNA) synthesis had a minimum increase of 156 % and the maximum of 389 %, compared to the original values and the maintenance requirement had a minimum increase of 126 % and maximum of 160 % compared to the original values. Lower limits of 95 % confidence intervals for the parameters related to maintenance and protein accretion rates were higher than the original estimates of the DGM, evidencing genetic differences of the Zebu crossbred animals in relation to the original DGM parameters

BeefTader (part I): optimal economical endpoint identification using mixed modeling approach decreases greenhouse gases emission and other pollutants for livestock farmers.

The current study is the first from three sequential abstracts based on BeefTrader DSS to maximize profitability of farmers and the meat industry.Coordenador: Roberto Giolo de Almeida. II SIGEE

BeefTrader (part II): optimal economical endpoint identification using nonparametric bootstrapping technique decreases greenhouse gases emission and other pollutants in feedlots.

The current study is the second from three sequential abstracts based on BeefTrader DSS to maximize profitability of farmers and the meat industry.Coordenador: Roberto Giolo de Almeida. II SIGEE

BeefTrader (part III): meat industry opportunity to improve its profitability reducing greenhouse gases emission and pollutants based on optimal economical endpoint identification.

The aim of this study was evaluate the economic and environmental benefits to meat packers based on OEE individual identification.Coordenador: Roberto Giolo de Almeida. II SIGEE

ASAS CENTENNIAL PAPER: Net Energy Systems for Beef Cattle – Cattles, Application, and Future Models

Development of nutritional energetics can be traced to the 1400s. Lavoisier established relationships among O2 use, CO2 production and heat production in the late 1700s, and the laws of thermodynamics and law of Hess were discovered during the 1840s. Those discoveries established the fundamental bases for nutritional energetics and enabled the fundamental entity ME = retained energy + heat energy to be established. Objectives became: 1) to establish relationships between gas exchange and heat energy, 2) to devise bases for evaluation of foods that could be related to energy expenditures, and 3) to establish causes of energy expenditures. From these endeavors, the basic concepts of energy partitioning by animals were developed, ultimately resulting in the development of feeding systems based on NE concepts. The California Net Energy System, developed for finishing beef cattle, was the first to be based on retained energy as determined by comparative slaughter and the first to use 2 NE values (NEm and NEg) to describe feed and animal requirements. The system has been broadened conceptually to encompass life cycle energy requirements of beef cattle and modified by the inclusion of numerous adjustments to address factors known to affect energy requirements and value of feed to meet those needs. The current NE system remains useful but is empirical and static in nature and thus fails to capture the dynamics of energy utilization by diverse animals as they respond to changing environmental conditions. Consequently, efforts were initiated to develop dynamic simulation models that captured the underlying biology and thus were sensitive to variable genetic and environmental conditions. Development of a series of models has been described to show examples of the conceptual evolution of dynamic, mechanistic models and their applications. Generally with each new system, advances in prediction accuracy came about by adding new terms to conceptually validated models. However, complexity of input requirements often limits general use of these larger models. Expert systems may be utilized to provide many of the additional inputs needed for application of the more complex models. Additional information available from these systems is expected to result in an ever-increasing range of application. These systems are expected to have increased generality and the capability to be integrated with other models to allow economic evaluation. This will eventually allow users to compute solutions that allow development of optimal production strategies

Forage and grain yields and forage composition of barley, wheat, and oats

Cattlemen's Fate in '78 is known as Cattlemen’s Day, 1978We harvested barley, wheat and oat varieties at the dough stage. Average yields in tons of 65% moisture forage/acre were 9.3 (barley), 10.2 (hard wheat), 9.5 (soft wheat), and 10.0 (oats). Barley variety yields varied most because of winter kill. Barley forages were the most digestible; oats, the least digestible. Crude fiber and grain contents of the forages were highly correlated with digestibility. Barley yielded highest in digestible dry matter, but hard wheat yields were more consistent from year to year

Integration of energy and protein transactions in the body to build new tools for predicting performance and body composition of ruminants

Increased market pressure to improve meat yield and quality require improved methods of predicting body composition in growing animals. Current systems of animal nutrition based on nutrient supply and animal characteristics predict animal growth from nutrient inputs, but, as of yet, do not accurately predict body composition. The present paper explores the evidence and data required to support an existing model of the effects of energy intake on visceral and muscle protein mass and energy expenditure to predict heat production, growth and body composition of sheep. While parameters of the model related to energetic costs of protein in muscle and viscera can be supported by independent studies, parameters associated with energetic costs of protein gain, particularly in viscera, are harder to reconcile with independent measurements. The range of available data on systematic changes in visceral organ mass over time in response to feed intake is limited, which may constrain generalisation of the parameters of the model with regard to the wide range of production situations faced by the sheep and cattle industries. However, sufficient data exist in the literature to test, and if required, revise the current framework

Estimation of the Requirement for Water and Ecosystem Benefits of Cow-Calf Production on California Rangeland

Beef production is perceived as using large amounts of water, and some studies recommend decreasing or ceasing meat consumption to decrease water use. Water footprints include different types of water, including green water (i.e., precipitation used for plant growth), blue water (i.e., drinking water and irrigation water used to grow alfalfa and irrigated pasture), and grey water (i.e., freshwater required for integrating water pollutants to a level accepted by water quality standards). A static model depicting blue and green water use for cow-calf production on California rangeland was developed. In this study, green water, which is sourced from rainfall and not available for another use, contributed the largest component to the total water footprint of cow-calf production at each location. It is important to consider the water use associated with beef production in the context of ecosystem services cattle provide to rangelands, such as preventing grassland conversion to shrub lands or woodlands, and the role that grazing cattle play in management of rangeland. © 2017 The Society for Range ManagementThe Rangelands archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information

Sudangrass, sorghum-sudan, forage sorghum, and corn silages and three protein levels for growing yearling steers

Cattlemen's Fate in '78 is known as Cattlemen’s Day, 1978Sudangrass, sorghum-sudan, forage sorghum, and corn silages were full-fed to yearling steers for 70-or 91-day growing periods. For both periods, steers fed corn silage outperformed steers fed any other silage. In the 70-day period silages from both sudangrass and sorghum-sudan cut at 45- and 60-inch plant heights, respectively, supported performance similar to forage sorghum silage. For both periods steers fed sorghum-sudan (dough) silage gained slowest and least efficiently. For the 91-day period, rations containing 12.0% crude protein supported better performance than rations containing 10.5 or 9% protein and 10.5% protein rations supported better performance than 9% protein rations