Estimation of the total efficiency of metabolizable energy utilization for maintenance and growth by cattle in tropical conditions

Abstract

-Data of 320 animals were obtained from eight comparative slaughter studies performed under tropical conditions and used to estimate the total efficiency of utilization of the metabolizable energy intake (MEI), which varied from 77 to 419 kcalThe provided data also contained direct measures of the recovered energy (RE), which allowed calculating the heat production (HE) by difference. The RE was regressed on MEI and deviations from linearity were evaluated by using the F-test. The respective estimates of the fasting heat production and the intercept and the slope that composes the relationship between RE and MEI were 73 kcal-42 kcal− and 0.37. Hence, the total efficiency was estimated by dividing the net energy for maintenance and growth by the metabolizable energy intake. The estimated total efficiency of the ME utilization and analogous estimates based on the beef cattle NRC model were employed in an additional study to evaluate their predictive powers in terms of the mean square deviations for both temperate and tropical conditions. The two approaches presented similar predictive powers but the proposed one had a 22% lower mean squared deviation even with its more simplified structure.Key Words: bioenergetics, growth, net energy, ruminants Estimação da Eficiência Total de Utilização da Energia Metabolizável para Manutenção e Crescimento por Bovinos em Condições TropicaisRESUMO -Foram utilizadas 320 informações obtidas a partir de 8 estudos de abate comparativo conduzidos em condições tropicais para se estimar a eficiência total de utilização da energia metabolizável consumida, a qual variou de 77 a 419kcalOs dados também continham informações sobre a energia retida (RE), o que permitiu o cálculo da produção de calor por diferença. As estimativas da produção de calor em jejum e dos coeficientes linear e angular da regressão entre RE e MEI foram respectivamente, d − e 0 ,37. Em seguida, a eficiência total foi estimada dividindo-se a energia líquida para mantença e produção pelo consumo de energia metabolizável. A eficiência total de utilização da MEI obtida e estimativas análogas baseadas no modelo do NRC gado de corte foram empregadas em um estudo adicional para avaliar as predições da energia líquida total para mantença e crescimento em condições de clima temperado e tropical. Os dois modelos apresentaram poder de predição semelhante, mas o quadrado do desvio médio do método proposto foi 22% menor, mesmo com uma estrutura mais simplificada.

Factors affecting feed efficiency in dairy goats

“…The transformation of food energy into products of animal origin, as in any other energy transformation system, is not devoid of losses since there is an efficiency by which the food energy is used for maintenance and production (Henrique et al, 2005). Animal feeding is the biggest factor responsible for the expenditures involved in milk production.…”

Energy partition for maintenance and weight gain in Nellore and crossbred steers finished under grazing

“…The adjustment of non-linear model BW × MEI, with the restrictions proposed by Henrique et al (2005), resulted in estimated values for NE m ME m slightly higher than those obtained by the linear model ( Table 1). The same trend was observed by Siqueira et al (2007).…”

“…In order to estimate the net energy for maintenance (NEm), it was adjusted the linear equation proposed by Lofgreen & Garrett (1968): log 10 HE = α + γ × MEI (equation 1) where NE m = 10 α In order to estimate the ME for maintenance (ME m ) and the efficiency of utilization of ME for maintenance (k m ) and gain (k g ), the following equation was adjusted (Lofgreen & Garrett, 1968): In addition, with the objective of verifying the equivalence of results, the energy efficiency and requirements for maintenance (NE m , ME m and k m ) were also estimated without logarithmic transformation, using directly the nonlinear equation proposed by NRC (1981), applying the constraint ζ + θ × ME m = 0 (Henrique et al, 2005):…”

“…The amount of information has enabled the compilation and analysis of large numbers of results, leading to equations and/or values probably more reliable and representative of the national herd (Fontes, 1995;Henrique et al, 2005). However, almost all the Brazilian studies on the energy requirements of cattle were conducted under confinement conditions, thus exist a great need for informations about grazed animals (Fontes et al, 2005a,b).…”

A model for evaluating beef cattle rations considering effects of ruminal fiber mass

“…The energy and protein requirements were predicted according to parameters estimated under tropical feedlot conditions (Fontes, 1995;Henrique et al, 2005), with the exception of the maintenance protein requirement . The complete set of mathematical expressions related to the presented approach can be found in Henrique (2007).…”