Energy Requirements For Weight Gain Research Articles

Net protein and energy requirements for weight gain of Santa Inês and Morada Nova sheep

The objective of this study was to determine the body composition and the dietary protein and energy requirements for weight gain of Santa Inês and Morada Nova sheep. A total of 48 intact lambs (24 Santa Inês and 24 Morada Nova), with initial weights of 21.7 ± 1.2 kg and 20.8 ± 0.8 kg and ages of 170 and 190 days, respectively, were used. At the beginning of the experimental phase, six lambs of each breed were slaughtered to determine body composition. The remaining 36 animals were divided into six groups of six animals each, separated by slaughter weights (25, 28 and 31 kg) and genotypes. The comparative slaughter technique was used to determine the nutritional requirements. The respective net requirements for energy gain ranged from 3.07 to 3.42 and 3.40 to 4.08 Mcal/kg gain of empty body weight (EBW), while for protein gain, the requirements ranged from 140 to 132 and 113 to 102 g/kg of EBW gain for intact genotypes lambs weighing between 22 and 31 kg. The Santa Inês sheep had higher net protein but lower net energy requirements for weight gain than the Morada Nova sheep. The body composition and the net requirements of protein and energy gains of genotypes sheep differ from the values reported by the main international committees of nutritional assessments.

Energy and protein requirements of non-descript breed hair lambs of different sex classes in the semiarid region of Brazil.

The aim of this study was to determine the energy and protein requirements of non-descript breed hair lambs (NDB) reared under Brazilian semiarid conditions. Sixty animals from three sex classes (20 intact males, 20 castrated males, and 20 females) with an average initial body weight of 18.1 ± 0.4 kg and an average age of 5 months were used. The nutritional requirements were estimated using the comparative slaughter. The animals in the final slaughter group were distributed in a completely randomized design with a 3 × 3 factorial scheme (three sex classes and three feeding levels: ad libitum feeding (positive energy balance), 70% feed restriction (maintenance level), and 80% feed restriction (negative energy balance)). The net energy requirement for maintenance (NEm) did not differ between sex classes (P > 0.05) and it was 68 kcal/kg of metabolic empty body weight (EBW(0.75))/day (P < 0.05). The coefficients for the nonlinear regression of retained energy (RE) on the empty body weight gain (EBWG) were not different among the different sex classes (P > 0.05). The net energy requirement for weight gain (NEg) was estimated by NEg (Mcal/day) = 0.29 × EBW(0.75) × EBWG(0.86) for all sex classes (P < 0.05). The net protein requirement for weight gain (NPg) was estimated by NPg (g/day) = 224.45 × EBWG - 0.025 × RE for all sex classes (P < 0.05). The NEg increased and the NPg decreased with the increase in body weight of NDB lambs.

Visceral metabolism and efficiency of energy use in animals taurine and zebuine

The relationship between energy intake, retained energy and heat production, along with the separation of maintenance and production, form the basis for discussion of the factors that affect energy requirements and efficiency of use in cattle. The knowledge of the energy efficiency of different species of cattle and their energy requirements for weight gain and for maintenance is important to obtain maximum productivity with minimum cost. The evaluation of the relative size of the organs is of utmost importance due to have a direct influence on carcass yield and the energy requirement for maintenance. The parties do not integrate carcass vary in weight according to race, stage of maturity and nutritional level. The relative size of the internal organs is of paramount importance as it has a direct influence on carcass yield and energy requirement for maintenance. The energy metabolism has direct influence of extrinsic and intrinsic to the animal, including age, weight, race, body composition, sexual condition, production potential, environmental conditions, activity and feeding level. Knowledge of the efficiency of utilization of metabolizable energy of the diet for different biological processes is necessary for the determination of metabolizable energy requirements (from the net requirements). Thus, the generation of information and the volume of publications on comparison of Bos tauros and Bos indicus must increase in order to own nutritional standards and differences in the partition of energy more statements because there is much conflict in the literature even within the same race.

Metabolic determinants of body weight after cats were fed a low-carbohydrate high-protein diet or a high-carbohydrate low-protein diet ad libitum for 8 wk

Overweight and obese conditions are common in cats and are associated with the development of a number of diseases. Knowledge of metabolic determinants and predictors of weight gain may enable better preventative strategies for obesity in cats. Lean, healthy cats were fed either a low-carbohydrate high-protein diet (n 16) or a high-carbohydrate low-protein (n 16) diet ad libitum for 8 wk. Potential determinants and predictors of final body weight assessed were body fat and lean masses, energy required for maintenance, energy requirements above maintenance for each kilogram of weight gain, insulin sensitivity index, fasting, mean 24-h and peak plasma glucose, insulin, and leptin concentrations, and fasting and mean 24-h serum adiponectin concentrations. In cats fed the low-carbohydrate high-protein diet, after adjusting for initial body weight, those with higher energy requirements for weight gain and higher fasting glucose concentration had higher final body weights (P ≤ 0.01). Predicted final body weights using initial body weight, fasting glucose and mean 24-h insulin concentrations (partial R2 37.3%) were imprecise. An equation using just initial body weight and fasting glucose concentration would be of more practical value, but was marginally less precise. In cats fed the high-carbohydrate low-protein diet, those with lower fasting leptin concentration initially had higher final body weights (P = 0.01). Predicted final body weights using initial body weight, energy requirements for maintenance, total body fat percentage and fasting leptin concentration (partial R2 39.2%) were reasonably precise. Further studies are warranted to confirm these findings and to improve the precision of predicted final body weights.

&lt;b&gt;Requirement of energy and protein of beef cattle on tropical pasture&lt;/b&gt; - doi: 10.4025/actascianimsci.v35i4.21143

Protein and energy requirements of beef cattle, aged between 4 and 18 months old, on tropical pastures, were estimated. Forty-six Nellore calves (138.3 ± 3.4 kg BW and 90-150 days old), kept on pasture, were distributed in a maintenance group (restricted feeding) or in nutritional plans, receiving a supplements with different amounts of protein and carbohydrate or non-supplemented. The net energy requirement for weight gain (NE g ) was obtained by linear regression of logarithm of retained energy as a function of logarithm of empty body weight gain. The net energy requirement for maintenance (NE m ) was estimated by the exponential relation between heat production and metabolizable energy intake. Net protein requirement for weight gain (RP) was estimated by multiple linear regression of retained protein in the weight gain of empty body (EBWG) and retained energy. The efficiency of metabolizable energy (ME) used for maintenance and for weight gain was 0.55 and 0.26, respectively. The ME requirement for maintenance was 124 kcal EBW -0.75 . RP decreased in proportion to body weight increase. NE g and RP may be obtained by equations: RE (Mcal kg -1 ) = 0.044 x EBW 0.75 x EBWG 1.1302 and RP (g day -1 ) = -31.45 + 229.69 x EBWG – 8.75 x RE, respectively.

Energy nutritional requirements for females of Nellore, Nellore × Angus and Nellore × Simmental fed on two forage: concentrate ratios

The objective of this study was to determine the energy nutritional requirements for females of Nellore, Nellore × Angus and Nellore × Simmental fed on two levels of concentrate. Sixty heifers from three genetic groups were used: 20 Nellore, 20 Nellore × Angus and 20 Nellore × Simmental. Twelve belonged to the reference group (four of each genetic group) and were slaughtered at the beginning of the experiment. Another 12 heifers (four of each genetic group) were fed on the maintenance level and 36 heifers (12 animals of each genetic group) were kept in feeding system ad libitum with 30 (six in each group) or 50% (six of each group) dry matter concentrate. Animals were randomly assigned to six treatments in a 3 × 2 factorial arrangement (three genetic groups and two diets) with six replicates per treatment. Nine more heifers were used in a parallel experiment to estimate the apparent digestibility coefficients (three from each genetic group). Net energy requirements were estimated by the equation of retained energy as a function of metabolic empty body weight (EBW0.75) and empty body weight gain (EBWg). Requirements of metabolizable and net energy were estimated for maintenance by the equation of heat production as a function of metabolizable energy intake. Using the combined equation RE (retained energy; Mcal/day) = 0.0703 × EBW.75 × EBWg1.128 to predict net energy requirements for weight gain is recommended. The requirement of metabolizable and net energy for maintenance of all groups is 70.55 and 106.53 kcal/kgEBW0.75/day, respectively. Use efficiencies of metabolizable energy for gain and maintenance are 36.41 and 66.23%, for the three genetic groups respectively.

Net requirements of energy, protein and macrominerals for weight gain of grazing beef cattle castrated at different ages, with and without supplementation

The objective of this experiment was to estimate the requirements of energy, protein and macrominerals of grazing crossbreds calves, in Brachiaria decumbens Stapf pasture, castrated at different ages, with and without supplementation. Forty-seven young calves at initial age of 120±30.1 days and 115.3±1.97 kg of live weight were used. To estimate net energy requirements for weight gain, a regression equation between energy retained in the gain and empty body weight gain and metabolic empty body weight was obtained. For estimation of net protein requirements for weight gain, a regression equation was adjusted between protein retained in gain and empty body weight gain and energy content of this gain. Net requirements of Ca, P, Mg and Na for weight gain were determined by the equation Y' = a.b. Xb-1, in which a and b represent the intercept and the coefficient of the alometric equation of macromineral body content prediction, respectively. Neither castration nor concentrate supplementation affects body weight gain net requirements, except the ones of Ca, which were higher for non-castrated animals.

Body composition and energy and protein requirements of grazing Nelore steers

This experimentwas carried out with the objective of determining the energy and protein requirements of grazing Nellore steers. Twenty four Nellore steers (average 371 ± 14 kg of BW and 26 months old) were used. Four steers were slaughtered at the beginning of the experiment (reference group), serving as a reference for the subsequent study. The remaining 20 animals were weighed and distributed in a randomized complete block design with four levels of supplementation offers: 0.0 (mineral mixture - control), 0.3, 0.6 and 0.9% BW, with five replications. The supplements, based on ground corn, soybean meal and/or urea, were previously balanced to achieve an average daily gain of 350, 650 and 850g, respectively, for the different levels of supplementation offers. The protein, fat and energy contents retained in the animal body were determined by regression equations of the logarithm of the protein, fat and energy in the animal body contents, in function of the logarithm of empty body weight (EBW). Net requirements of protein and energy for a gain of 1kg of EBW were obtained by deriving the prediction equations of the animal body content of protein, fat, or energy in function of the EBW logarithm. The net energy requirements for weight gain of Nellore steer can be obtained by the equation: NEg = 0.05764 × EBW0,75 × DEBWG0.8328. The following equation was obtained to estimate the retained protein (RP), in function of the average daily gain (ADG) and retained energy (RE): RP = 28.9199 + 85.7301 FBWG + 8.0669 RE. The net protein requirement for Nellore steers decreased as the body weight increased, with values of 174.62 and 163.10 g/kg EBG for animals of 300 and 450 kg BW, respectively.

Composição corporal e requisitos energéticos de bovinos de corte sob suplementação em pastejo

Objetivou-se determinar as exigências de energia de bovinos de corte em pastagem de Brachiaria decumbens com suplementação. Foram utilizados 28 novilhos anelorados, não-castrados, com 7 meses de idade e 180 kg de peso vivo inicial. Oito animais foram abatidos em diferentes faixas de peso e serviram como referência. Para determinação das exigências líquidas para ganho de peso, foi construída uma equação de regressão entre o log da energia retida (ER) e o log do ganho de peso de corpo vazio (GPCVZ). As exigências de energia líquida para mantença (ELm) foram estimadas por meio do log da produção de calor (PC) em função do consumo de energia metabolizável (CEM). As eficiências de utilização da energia metabolizável para mantença (km) foram estimadas pela relação entre os teores de ELm e a EM da dieta e a eficiência de utilização da energia para ganho de peso (kg) foi estimada como o coeficiente da regressão linear entre a energia retida e o consumo de energia metabolizável. As exigências de ELm de bovinos anelorados sob pastejo foram de 82,4 kcal/PCVZ0,75/dia ou 76,12 kcal/PV0,75/dia. Animais zebuínos não-castrados sob pastejo apresentam exigências líquidas de mantença 5% superiores às de zebuínos em confinamento. As exigências diárias de EMm foram de 149,76 kcal/PCVZ0,75 e a eficiência de utilização da energia metabolizável para mantença (k m) de animais anelorados sob pastejo foi de 55% e para ganho (k g), de 29%.

BMI, body composition, and the energy requirement for body weight gain in patients with anorexia nervosa

Theories abound about the energy requirements for body weight gain in anorexia nervosa (AN). We hypothesized that malnutrition status affects the energy requirements. On admission, 97 AN patients were measured for body composition by dual-energy X-ray absorptiometry. The relationship between body mass index (BMI) and body composition was investigated. In addition, 21 patients who completed our treatment program were tested for energy intake and body weight. The relationship between BMI and both fat-free mass and fat mass (FM) on admission was curvilinear. The weight gain per excess energy was greater in the group of patients with FM < 4 kg or BMI < 14 kg/m(2) than in the group with FM > or = 4 kg or BMI > or = 14 kg/m(2) (p = .037, p = .055, respectively). The energy requirements for weight gain in AN patients are related to the initial FM and BMI.

Body composition and net protein and energy requirements for weight gain of crossbred dairy cattle in grazing

The body composition and net protein and energy requirements for weight gain of 5/8 Hostein-Zebu crossbred cattle raised in Brachiaria decumbens Spaft pasture were evaluated. In total, 16 bulls with 10 months of age and body weight (BW) of 180 ± 19.95 kg were used. The animals were kept with free access to pasture or with restricted grazing (from 6 to 10 h). Four animals were slaughtered at the beginning of the experimental period to estimate the empty body weight (EBW) and the initial body composition of the remaining animals. The other animals were slaughtered at the end of the 84-day trial period. The logarithm equations of the protein and energy body content were adjusted according to the logarithm of the empty body weight EBW. From these equations, the net protein and energy requirements for weight gain were estimated. There was an increase in fat (from 37.17 to 59.08 g/kg EBW) and energy (from 1.68 to 1.94 Mcal/kg EBW) concentrations, with increase in body weight from 150 to 250 kg. The protein and energy requirements for gaining 1 kg of EBW increased with the increase in body weight or empty body weight. The relationship between fat concentration in gain and protein requirements also increased, indicating that as the BW or EBW increase, more fat deposition in the gain is observed.

Composição corporal e exigências de energia para ganho de peso de caprinos Moxotó em crescimento

Utilizaram-se 26 animais da raça Moxotó, machos não-castrados, com peso vivo (PV) médio inicial de 15 kg e 7 a 8 meses de idade, alimentados com dieta contendo 2,6 Mcal de energia metabolizável, com o objetivo de avaliar a composição corporal e as exigências de energia para ganho de peso. Ao início do experimento, seis animais foram abatidos e serviram como referência na estimativa da composição corporal e do peso do corpo vazio (PCVZ) iniciais. O experimento foi conduzido em delineamento inteiramente casualizado, com quatro tratamentos (alimentação à vontade - AV; e 85, 70 ou 55% do consumo observado no grupo com AV) e cinco repetições. Quando o PV dos animais com AV se aproximava de 25 kg, um animal de cada tratamento com restrição alimentar era abatido. Ajustaram-se as equações do logaritmo (log) dos conteúdos corporais de gordura (CCG) e energia (CCE) em função do log do PCVZ. A concentração de água no corpo dos animais experimentais foi baixa, entretanto, as deposições de gordura, proteína e cinzas aumentaram com a maturidade dos animais. Foram observados aumentos de 78,55 para 125,38 g/kg de PCVZ nos conteúdos corporais de gordura e de 1,90 para 2,34 Mcal/kg de PCVZ nos conteúdos corporais de energia com o aumento de 15 para 25 kg no PV dos animais. Verificou-se relação linear positiva entre a composição em energia do ganho em PCVZ (GPCVZ) (Mcal/kg GPCVZ) e o PCVZ. Resposta semelhante foi constatada para os conteúdos de gordura no ganho. Os conteúdos corporais de gordura (g) e energia (Mcal) de caprinos Moxotó aumentam de 14,33 para 22,87 e 0,26 para 0,32 por 100 g de GPCVZ, respectivamente, à medida que aumenta o PCVZ.

Exigência de proteína bruta e energia metabolizável para codornas de corte EV1

Estudou-se a exigência de proteína bruta e energia metabolizável para codornas européias EV1, durante três períodos experimentais, 7-21, 22-42 e 7-42 dias de idade, utilizando-se 576 aves, de ambos os sexos. O delineamento experimental foi inteiramente ao acaso, em arranjo fatorial 4 x 2, quatro níveis de proteína bruta (22, 24, 26 e 28% de PB) e dois níveis de energia (2900 e 3100kcal de EM/kg de ração), com seis repetições de 12 codornas por unidade experimental. O peso corporal e o ganho de peso do sétimo ao 21º dia de idade foram influenciados de forma quadrática pelo nível protéico da dieta. O consumo alimentar diminuiu linearmente com o aumento do nível energético. A conversão alimentar aumentou com o aumento da PB e reduziu com o aumento do nível de EM. O peso corporal no 42º dia, o ganho de peso e a conversão alimentar (7-42 dias) não foram influenciados pelos níveis de EM e PB das dietas. O nível energético 2900kcal de EM/kg propiciou maior consumo em relação à dieta com 3100kcal de EM/kg. O máximo desempenho das codornas de corte EV1 foi alcançado com dietas formuladas com 27% PB e 2900 kcal de EM/kg no período inicial (sétimo ao 21º dia de idade) e 22% de PB e 2900 kcal de EM/kg durante o período total de criação (sétimo ao 42º dias de idade).

Modelling energy utilisation in broiler breeder hens

1. The objective of this study was to determine a metabolisable energy (ME) requirement model for broiler breeder hens. The influence of temperature on ME requirements for maintenance was determined in experiments conducted in three environmental rooms with temperatures kept constant at 13, 21 and 30°C using a comparative slaughter technique. The energy requirements for weight gain were determined based upon body energy content and efficiency of energy utilisation for weight gain. The energy requirements for egg production were determined on the basis of egg energy content and efficiency of energy deposition in the eggs. 2. The following model was developed using these results: ME = kgW 0·75(806·53–26·45T + 0·50T 2) + 31·90G + 10·04EM, where kgW 0·75 is body weight (kg) raised to the power 0·75, T is temperature (°C), G is weight gain (g) and EM is egg mass (g). 3. A feeding trial was conducted using 400 Hubbard Hi-Yield broiler breeder hens and 40 Peterson males from 31 to 46 weeks of age in order to compare use of the model with a recommended feeding programme for this strain of bird. The application of the model in breeder hens provided good productive and reproductive performance and better results in feed and energy conversion than in hens fed according to strain recommendation. In conclusion, the model evaluated predicted an ME intake which matched breeder hens’ requirements.

Exigências energéticas para mantença e para o crescimento de frangos de corte

O trabalho foi realizado com o objetivo de determinar, pelo método fatorial, as exigências de energia metabolizável (EM) de frangos de corte. Foi conduzido um ensaio em câmaras climáticas mantidas às temperaturas de 13, 23 e 32ºC (±2ºC) para se verificar o efeito da temperatura sobre as exigências de energia metabolizável para mantença utilizando-se a técnica do abate comparativo. As exigências de energia metabolizável para ganho de peso foram determinadas com base no teor de energia corporal e na eficiência energética de utilização da EM. As exigências de mantença foram de 159,36; 116,17 e 128,66 kcal/kg0,75/dia para 13, 23 e 32ºC, respectivamente, verificando-se efeito quadrático da temperatura sobre as exigências de mantença (EMm=300,14 - 14,61.T + 0,2876.T², r²=0,90). As exigências de EM para ganho de peso corporal foram de 3,72 kcal/g para machos e 3,98 kcal/g para fêmeas de 1 a 21 dias; 4,21 para machos e 3,93 para fêmeas de 22 a 42 dias; e 4,51 para machos e 7,04 para fêmeas de 43 a 56 dias. Considerando-se as exigências determinadas, foram elaborados modelos de predição das exigências diárias de energia para frangos de corte, nos quais foram considerados o peso corporal, a temperatura ambiente (para estimativa das exigências de mantença) e o ganho de peso (para cálculo das exigências de ganho). Com base nas comparações das exigências determinadas pelos modelos e nas recomendações do manual da linhagem, conclui-se que os modelos elaborados predizem as exigências energéticas dos frangos de corte.

Predicting growth rates of adult working boars in a commercial boar stud (2006)

There is almost no information on ideal growth rates for adult boars, but estimates can be made if the relationship between boar weight and age is known. Therefore, this study was aimed to predict growth rates in adult working boars in a commercial boar stud. A total of 214 adult working boars from two genetic lines in a commercial boar stud were individually weighed on a platform scale. Age of the boar was recorded at the time of weighing. A regression equation to predict boar weight as a function of age was developed by using PROC REG of SAS. The model was used to predict BW on a daily basis, and ADG was derived as the difference between two predicted BW values. Factorial estimates of daily ME requirement and feeding rates were determined. The energy requirement for weight gain was computed by using the predicted ADG as a guide in setting target weight gains. Results showed a positive curvilinear response (P<0.01) to describe the relationship between boar weight and age. Predicted ADG decreased in a curvilinear manner as the boars aged. In conclusion, on-farm growth rates can be predicted effectively by relating weight with age, taken from a representative number of boars in a given farm population. These data can then be used to develop farm specific feeding programs or to set different growth curves for experimental purposes.; Swine Day, 2006, Kansas State University, Manhattan, KS, 2006

Modeling metabolizable energy utilization in broiler breeder pullets

The objective of this study was to determine models for ME requirements for broiler breeder pullets using the factorial method. The influence of the temperature on maintenance ME requirements was determined by experiments conducted in three environmental rooms with temperature kept constant at 15,22, and 30 degrees C, using the comparative slaughter technique. The energy requirements for weight gain were determined based on the body energy content and efficiency of energy utilization for weight gain. Two ME requirement models for each age were developed using the coefficients for maintenance and weight gain. The models for 3 to 8 wk were ME = W(0.75) (186.52 - 1.94T) + 2.47WG, and ME = W(0.75) (174 - 1.88T) + 2.83WG; for 9 to 14 wk, ME = W(0.75) (186.52 - 1.94T) + 2.69WG, and ME = W(0.75) (174 - 1.88T) + 2.50WG; and 15 to 20 wk, ME = W(0.75) (186.52 - 1.94T) + 2.76WG, and ME = W(0.75) (174 - 1.88T) + 3.24WG. In these equations, W is BW (kg), T is temperature (degrees C), and WG is daily weight gain (g). These models were compared to the breeder's recommendations in a feeding trial from 5 to 20 wk of age. Models 1 and 2 provided energy intakes that promoted BW smaller than the breeder's recommendation. However, all breeder pullets had weights above the standard recommendation. Model 2 gave the smallest ME intake and BW close to the standard recommendation and provided the best prediction of ME requirements.

Composição corporal e exigências energéticas e protéicas de bovinos F1 Limousin x Nelore, não-castrados, alimentados com rações contendo diferentes níveis de concentrado

Foram utilizados 50 novilhos F1 Limousin x Nelore inteiros, alocados em dez tratamentos, com cinco níveis de concentrado (25; 37,5; 50; 62,5; e 75%) e duas formas de balanceamento protéico da dieta (uma isoprotéica com 12% de proteína bruta [PB] e outra variando proteína com energia). Avaliaram-se os consumos de matéria seca (MS), matéria orgânica (MO), PB, fibra em detergente neutro (FDN) e nutrientes digestíveis totais (NDT). Após o abate, todas as partes do corpo do animal foram pesadas, amostradas e analisadas para MS, teores de compostos nitrogenados totais e extrato etéreo. Os conteúdos de proteína, gordura e energia retidos no corpo foram estimados por meio de equações de regressão do logaritmo do conteúdo corporal de proteína, gordura ou energia, em função do logaritmo do peso de corpo vazio (PCVZ). As exigências líquidas de proteína e energia, para ganho de 1 kg de PCVZ foram obtidas a partir da equação Y = b. 10ª. Xb-1, sendo a e b o intercepto e o coeficiente de regressão, respectivamente, das equações de predição dos conteúdos corporais de proteína ou energia. A exigência líquida de energia para mantença (ELm) foi estimada como o anti-log do intercepto da equação obtida pela regressão linear entre o logaritmo da produção de calor e o consumo de energia metabolizável. A forma de balanceamento da dieta não influenciou os consumos dos nutrientes. O consumo de MS, em kg/dia, não foi influenciado pelo nível de concentrado (NC), apresentando média de 7,39 kg/dia. O NC das dietas não influenciou o consumo de MO (7,08 kg/dia). Com o aumento do NC, o consumo de FDN reduziu e o de NDT aumentou linearmente. Nas dietas com níveis de proteína variados, o consumo de PB aumentou linearmente. Já as dietas isoprotéicas não foram influenciadas pelo NC, apresentando média de consumo de PB de 0,89 kg/dia. As exigências de energia líquida para ganho de peso de bovinos F1 Limousin x Nelore não-castrados, em Mcal/kg, podem ser obtidas pela equação: ELg = 0,038 x PCVZ0,75 x GDPCVZ0,9896. A ELm para estes animais foi de 76,36 kcal/PCVZ0,75. Foi obtida a seguinte equação para estimativa da proteína retida (PR), em g/dia, em função do ganho de PV em jejum (GPVJ), em kg/dia: PR = 174,14524 x GPVJ.

Composição Corporal e Requisitos Energéticos e Protéicos de Bovinos Nelore, Não-Castrados, Alimentados com Rações Contendo Diferentes Níveis de Concentrado e Proteína

Foram utilizados 40 novilhos Nelore inteiros, com peso vivo médio inicial de 240 kg, sendo quatro novilhos de referência, quatro alimentados para mantença e o restante distribuído em oito tratamentos, com quatro diferentes níveis de concentrado nas dietas (20; 40; 60 e 80%) e dois níveis de proteína bruta (PB) (15 e 18%). Os conteúdos de proteína, gordura e energia retidos no corpo foram estimados por meio de equações de regressão do logaritmo do conteúdo corporal de proteína, gordura ou energia, em função do logaritmo do PCVZ. Derivando-se as equações de predição do conteúdo corporal de proteína, gordura, ou energia, em função do logaritmo do peso de corpo vazio (PCVZ), foram obtidas as exigências líquidas de proteína e energia, para ganho de 1 kg de PCVZ, a partir de equação Y' = b. 10ª. Xb-1, sendo a e b a intercepta e o coeficiente de regressão, respectivamente, das equações de predição dos conteúdos corporais de proteína ou energia. As exigências líquidas de energia para mantença (ELm) foram estimadas como o anti-log da intercepta da equação obtida pela regressão linear entre o logaritmo da produção de calor (PC) e o consumo de energia metabolizável (CEM). As exigências de energia líquida para ganho de peso de zebuínos não-castrados podem ser obtidas pela equação: ELg = 0,0413 x PCVZ0,75 x ganho diário de PCVZ0,978. A ELm, obtida neste experimento, foi de 83,70 kcal/PCVZ0,75, para animais não-castrados pertencentes à raça Nelore. Foi obtida a seguinte equação para estimativa da proteína retida (PR), em função do GMD e da energia retida (ER): PR = - 39,0169 + 200,638 ganho de peso vivo em jejum (GPVJ) + 0,4166 ER. A exigência líquida de proteína de Nelore, não-castrado diminuiu com o aumento do peso vivo, sendo de 183,22 e 173,72 g/kg GPCVZ para animais de 200 e 400 kg de peso vivo, respectivamente.