Metabolizable Protein Requirements For Maintenance Research Articles

Energy and protein requirements for Nellore steers estimated with the deuterium oxide marker

The aim of this study was determine the energy and protein requirements for maintenance and gain of Nellore steers. Thirty six Nellore steers with a average weight and age of 359±13 kg and 20 months at the beginning of the trial were individually fed for 56. The steers were fed the same diet (76.43% TDN and 13.62% CP) in three levels of dry matter (DM) intake, ad libitum, 75 g DM/kg BW0.75 and 60 g DM/kg BW0.75. The initial and final body composition was estimated with the marker deuterium oxide that allowed repeated water estimate in the same animal. Deuterium in blood samples was analyzed by mass spectrometry. The effects of intake levels, comparison of intercept and slope among feeding level, and equations were evaluated by the analysis of variance, adopting P<0.05 as a significant level. The net energy for maintenance was 75 kcal/kg EBW0.75 or 70 kcal/kg BW0.75. The net energy for gain for steers with 350 to 450 kg weight was 5.1 to 6.1Mcal. The efficiency of energy utilization for maintenance, km, was 0.7492 and for weight gain, kg, was 0.3404. The metabolizable protein requirement for maintenance was 4.32 * BW0.75 and the net protein for gain was estimated with the equation NPg = (254.68*EBWG) €“ (29.38*RE). The technique of deuterium oxide marker used to estimate energy and protein requirement for maintenance and weight gain at Nellore steers confirm the hypothesis presented in NRC, that NEm is lower than the requirement for taurine cattle. On the other hand, the reverse was true for the NP requirement for maintenance and for weight gain. We consider that indirect method using D2O for estimate body composition in zebu cattle was suitable to determine nutrient requirements.

Energy and protein requirements of woolless sheep under tropical conditions

The objective of this study was to determine the energy and protein requirements for maintenance and weight gain of growing woolless sheep and, in addition, to estimate the shrunk body weight (SBW) and empty body weight (EBW) of the animals according to their body weight (BW) in the fed state. Data from 150 animals from three comparative slaughter experiments with confined castrated sheep averaging 5 ± 0.96 months of age and similar BW (20.74 ± 2.99 kg) were used. Three models were evaluated to estimate EBW from SBW: linear, linear with intercept and non-linear. The following requirements were estimated: net energy for maintenance (NEm), metabolizable for maintenance (MEm), net energy for gain (NEg), efficiency of use of metabolizable energy for gain, metabolizable protein requirement for maintenance (MPm), net protein requirement for gain (NPg), and efficiency of use of metabolizable protein for gain (k). Fasting losses corresponded to 6.18% of BW and the better model to establish the relationship between SBW and EBW was nonlinear. The NEm and MEm were 70.44 and 109.34 kcal/kg EBW0.75/day, respectively. For NEg, the adjusted model was based on the ratio of the energy retained as a function of the EBW and the desired empty body weight gain (EBG). Considering two lambs weighing 15 kg and 30 kg with a daily gain of 100 g, the estimated NEg is 181 and 360 kcal/kg EBW0.75/day, respectively. The estimated kg was 0.407. For MPm, the value of 3.19 g/kg EBW0.75/day was estimated. The estimated NPg for animals of 15 and 30 kg, with the same gain rate was 13.13 and 13.61 g/day, respectively, which corresponds to the protein concentration in gain of 170 and 161 g/kg EBG, and efficiency of use of the metabolizable protein for gain ranging from 0.66 to 0.41. The nutritional requirements of woolless sheep did not follow the standards assumed by the international feeding systems, except for the energy requirements for maintenance and efficiency of use of the metabolizable energy for maintenance, which did not differ. The losses represented by the gastrointestinal tract (GIT) after fasting and slaughtering periods are higher in woolless sheep compared to those presented by the international feeding systems.

Maintenance and growth requirements in male and female hair lambs

An experiment was conducted to evaluate the energy and protein requirements of intact male, castrated male and female Morada Nova lambs. The animals were distributed in a completely randomized 3×3 factorial design with three sexes (15 intact males, 16 castrated males and 16 females) and three levels of dietary restriction (ad libitum, 30% and 60% feed restriction) with an initial body weight (BW) of 14.50±0.89kg. Four animals per sex were slaughtered at the start of the trial as a baseline group. When the mean BW in the ad libitum treatment reached 28kg, at day 120 of the experiment, all lambs were slaughtered. For all sexes, the net energy requirement for maintenance was 73.0kcal/kg0.75 empty body weight (EBW)/d (P=0.17). The metabolizable energy efficiency for maintenance (km) was 0.58. The metabolizable energy efficiency utilization for gain (kg) was 0.36; 0.25 and 0.28 for intact males, castrated males and females, respectively. The net energy requirement for gain (NEg) differed (P<0.01) between sexes. The NEg was 0.191, 0.198 and 0.276Mcal/kg0.75 EBW/d for intact males, castrated males and females, respectively, with a BW of 20kg and a body weight gain (BWG) of 100g. The net and metabolizable protein requirements for maintenance obtained for lambs were 1.06g/kg0.75 BW/d (P=0.78) and 3.46g/kg0.75 BW/d (P=0.39), respectively. The net protein for gain (NPg) differed (P<0.01) between sexes. For animals weighing 20kg and with an average daily gain of 100g/d, NPg was 7.08, 7.11 and 6.78g/d for intact males, castrated males and females, respectively. The net energy and protein requirements for maintenance of Morada Nova lambs slaughtered between 15 and 28kg did not vary by sex. The net energy for gain increases and the net protein for gain decreased with the increase in body weight in hair lambs.

Energy and protein requirements for maintenance of Southern Yellow cattle fed a corn silage or straw-based diet

Abstract The objective of this study was to estimate the net energy and net protein requirements for maintenance (NEm and NPm) of Southern Yellow cattle in China. A database involving 175 cattle with body weight (BW) ranging from 211 to 454 kg was obtained from a series of calorimetry experiments. The diets offered to cattle consisted of proportionately corn-soybean meal concentrate and roughage containing corn silage, rice straw and wheat straw. Linear regression equations of the logarithm of heat production (HP) and retained energy (RE) against metabolizable energy intake (MEI) were developed to predict the maintenance requirements for metabolizable energy (MEm) and NEm. The combined data indicated that the MEm and NEm were 522 and 348 MJ/kg0.75 of BW d−1, respectively. In addition, the partial efficiency of use of ME for maintenance was 0.66, and the partial efficiency for growth was 0.51. Similarly, there was also a linear relationship between retained nitrogen (RN) and nitrogen intake (NI). The pooled data provided a NPm of 2.63 g/kg0.75 of BW d−1 and a metabolizable protein requirement for maintenance (MPm) of 3.93 g/kg0.75 of BW d−1 for Southern Yellow cattle. In conclusion, our estimate of NEm was extremely similar to the value of the AFRC nutritional system, whereas it was slightly greater than that recommended by the NRC nutritional system. Additionally, the MPm value obtained in the current study was in agreement with the NRC recommendation.

Net protein and metabolizable protein requirements for maintenance and growth of early-weaned Dorper crossbred male lambs

BackgroundDorper is an important breed for meat purpose and widely used in the livestock industry of the world. However, the protein requirement of Dorper crossbred has not been investigated. The current paper reports the net protein (NP) and metabolizable protein (MP) requirements of Dorper crossbred ram lambs from 20 to 35 kg BW.MethodsThirty-five Dorper × thin-tailed Han crossbred lambs weaned at approximately 50 d of age (20.3 ± 2.15 kg of BW) were used. Seven lambs of 25 kg BW were slaughtered as the baseline animals at the start of the trial. An intermediate group of seven randomly selected lambs fed ad libitum was slaughtered at 28.6 kg BW. The remaining 21 lambs were randomly divided into three levels of dry matter intake: ad libitum or 70% or 40% of ad libitum intake. Those lambs were slaughtered when the lambs fed ad libitum reached 35 kg BW. Total body N and N retention were measured.ResultsThe daily NP and MP requirements for maintenance were 1.89 and 4.52 g/kg metabolic shrunk BW (SBW0.75). The partial efficiency of MP utilization for maintenance was 0.42. The NP requirement for growth ranged from 12.1 to 43.5 g/d, for the lambs gaining 100 to 350 g/d, and the partial efficiency of MP utilization for growth was 0.86.ConclusionsThe NP and MP requirements for the maintenance and growth of Dorper crossbred male lambs were lower than the recommendations of American and British nutritional systems.

Determination of energy and protein requirements for crossbred Holstein × Gyr preweaned dairy calves

The objective was to quantify the energy and protein nutritional requirements of Holstein × Gyr crossbred preweaned dairy calves until 64 d of age. Thirty-nine Holstein × Gyr crossbred male calves with an average initial live weight (mean ± SEM; for all next values) of 36 ± 1.0 kg were used. Five calves were slaughtered at 4 d of life to estimate the animals' initial body composition (reference group). The remaining 34 calves were distributed in a completely randomized design in a 3 × 2 factorial arrangement consisting of 3 levels of milk (2, 4, or 8 L/d) and 2 levels of starter feed (presence or absence in diet). At 15 and 45 d of life, 4 animals from each treatment were subjected to digestibility trials with total collection of feces (for 72 h) and urine (for 24 h). At 64 d of age, all animals were slaughtered, their gastro-intestinal tract was washed to determine the empty body weight (EBW; kg), and their body tissues were sampled for subsequent analyses. The net energy requirement for maintenance was estimated using an exponential regression between metabolizable energy intake and heat production (both in Mcal/EBW0.75 per d) and was 74.3 ± 5.7 kcal/EBW0.75 per d, and was not affected by inclusion of starter feed in the diet. The metabolizable energy requirement for maintenance was determined at the point of zero energy retention in the body and was 105.2 ± 5.8 kcal/EBW0.75 per d. The net energy for gain was estimated using the EBW and the empty body gain (EBG; kg/d) as 0.0882 ± 0.0028 × EBW0.75 × EBG0.9050±0.0706. The metabolizable energy efficiency for gain (kg) of the milk was 57.4 ± 3.45%, and the kg of the starter feed was 39.3 ± 2.09%. The metabolizable protein requirement for maintenance was 3.52 ± 0.34 g/BW0.75 per d. The net protein required for each kilogram gained was estimated as 119.1 ± 32.9 × EBW0.0663±0.059. The metabolizable protein efficiency for gain was 77 ± 8.5% and was not affected by inclusion of starter feed in the diet. In conclusion, the energy efficiency for gain of milk is higher than that of starter and the net protein required per unit protein gain increases with empty body weight.

Energy and protein requirements of crossbred Holstein x Zebu steers fed different levels of calcium and phosphorus in the diet

The aim of this study was to determine the energy and protein requirements of crossbred Holstein x Zebu steers fed with or without the supplementation of dicalcium phosphate in the diet. Thirty-two steers with an average initial body weight of 377.5 ± 49.4 kg were used, of which four were initially slaughtered to estimate the empty body weight (EBW) of the animals. Twenty-four steers were fed ad libitum and were distributed in a completely randomized design with two levels of concentrate (30 and 60 %), and diets with or without dicalcium phosphate and four steers were fed at maintenance level, so that the body weight gain was equal to zero. After 84 days the animals were slaughtered. The animal tissues were sampled, and composted by two samples, denominated by “carcass” (bone, muscle and fat) and “non-carcass” (head, limbs, blood, hide, organs and viscera) for determination of the body composition. The net energy requirements (NEm) and metabolizable energy for maintenance (MEm) were obtained while relating heat production (HP) and metabolizable energy intake (MEI); meanwhile, the net energy requirements for gain (NEg) and the net protein requirements for gain (NPg) were obtained as a function of empty body weight (EBW), empty body gain (EBG) and retained energy (RE) in EBW. The daily net and metabolizable energy requirements for maintenance were 76.90 and 119.36 kcal/EBW0.75, respectively. The net energy requirements for gain can be obtained by the following equation: NEg = 0.0568±0.0025 × EBW0.75 × EBG1.095. The efficiencies of use of metabolizable energy for maintenance and gain are 64.4 and 29.68 %, respectively. The metabolizable protein requirements for maintenance are 4.14 g/BW0.75. The net protein requirements for gain can be obtained through the following equation: NPg = 236.36±30.06 × EBG - 19.84±6.14 × RE. We recommend the use of the equations obtained in this experiment to calculate the energy and protein requirements of crossbred Holstein x Zebu steers.

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

This study aimed to determine the protein requirements for females of Nellore, F1 Nellore × Angus and F1 Nellore × Simmental fed on two concentrate levels (30 and 50%). Sixty heifers from three genetic groups with 18 months of age were used: 20 Nellore, 20 Nellore × Angus and 20 Nellore × Simmental. Twelve heifers of the reference group (four of each genetic group) were slaughtered at the beginning of the experiment. Another 12 heifers (four of each genetic group) were fed on the level of maintenance and 36 heifers (12 animals of each genetic group) were kept in power system ad libitum with 30% (six of each group) or 50% (six of each group) dietary dry matter in concentrate. Heifers 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 (three from each genetic group) were used to estimate the apparent digestibility coefficients of food in a parallel experiment. A model was fitted according to the protein retained as function of the gain of empty body weight (EBW) and retained energy (RE) to calculate the protein net requirements. To estimate the metabolizable protein requirements for maintenance the consumption of metabolizable protein was contrasted with EBW. The joint use of the equation net protein gain (NPG) = 197.40 × EBWg - 11.14 × RE is recommended to predict the protein net requirements for weight gain. Protein and metabolizable protein net requirements for maintenance are 1.07 and 3.88 g/EBW0.75/day, respectively. The use efficiency of metabolizable protein for gain of all genetic groups is 37.04%.

Exigências de proteína de animais Nelore puros e cruzados com as raças Angus e Simental

Objetivou-se estimar as exigências de proteína de animais Nelore, Nelore-Angus e Nelore-Simental, assim como a eficiência de uso da proteína metabolizável para ganho. Foram utilizados 69 animais (23 Nelore, 23 Nelore-Angus e 23 Nelore-Simental): 12 (quatro de cada grupo genético) foram abatidos antes do início do experimento, como grupo-referência, e nove animais foram separados para um ensaio de digestibilidade. Os animais restantes foram divididos em três dietas (ofertas de concentrado na base de 1 ou 2% do peso corporal à vontade e 1% do nível de mantença). Ao final do experimento, todos os animais foram abatidos e a composição corporal e o peso de corpo vazio (PCVZ) determinados. O consumo de proteína metabolizável (CPmet) foi estimado pela proteína microbiana verdadeira digestível média somada à proteína digestível não-degradada no rúmen. As exigências líquidas de proteína para ganho foram estimadas pela proteína retida (PR) em função do ganho de PCVZ (GPCVZ) e da energia retida. As exigências de proteína metabolizável para mantença foram estimadas pelo CPmet em função do GMD e as exigências líquidas para mantença pela PR em função do CPmet. O grupo genético influenciou apenas a relação entre os diferentes ganhos, mas não teve efeito sobre as exigências líquidas de proteína para ganho, que podem ser estimadas por meio do modelo PR = GPCVZ × (238,5 - 16,73 × (ER/GPCVZ)). Não há influência de grupo genético sobre as exigências líquidas e metabolizáveis de proteína para mantença, cujos valores são de 1,72 g/PCVZ0,75 e 3,09 g/PC0,75, respectivamente. Também não há efeito de grupo genético na energia retida em forma de proteína, assim como na eficiência de uso da proteína metabolizável para ganho, que é de 37,5%.

Balanço de compostos nitrogenados e estimativa das exigências de proteína de mantença de bovinos Nelore de três condições sexuais

Objetivou-se com este estudo avaliar o efeito de níveis crescentes de PB sobre o balanço de N e as exigências de proteína metabolizável para mantença em bovinos Nelore. Foram utilizados 12 bovinos Nelore, fistulados no rúmen e no duodeno, de três condições sexuais (quatro fêmeas, quatro machos castrados e quatro machos não-castrados), com idade aproximada de 16 meses e peso corporal médio de 254,8; 285,1 e 265,6 kg, respectivamente. Utilizaram-se três quadrados latinos 4 &lt;FONT FACE=Symbol&gt;´&lt;/FONT&gt; 4, compostos de quatro animais, quatro níveis de PB (7, 10, 13 e 15%) e quatro períodos. A produção de MS fecal e os fluxos de MS no duodeno foram estimados com a FDA indigestível. A coleta total de urina de cada animal foi realizada do 13º ao 14º dia de cada período. O N metabólico fecal (NMF) foi estimado por regressão entre o N absorvido (Y) e a ingestão de N (X), expressos em g/kg MS. As perdas endógenas urinárias foram estimadas por regressão entre a excreção urinária de N (Y) e a ingestão de N (X), expressas g/kg0,75. As perdas endógenas totais foram estimadas pela regressão entre o balanço de N (Y) e a ingestão de N (X), expressas em g/kg0,75. Houve efeito da condição sexual apenas sobre o N ingerido, de modo que o consumo foi maior para os machos castrados em relação às fêmeas. A ingestão de compostos nitrogenados, a excreção fecal de N, o N urinário e o balanço de compostos nitrogenados aumentaram linearmente com os teores dietéticos de PB. Foram registrados valores de 6,69 de N/kgMS ingerida para NMF e de 0,133 gN/kg0,75 para o N urinário endógeno. A exigência líquida total de proteína foi estimada em 0,431 gN/kg0,75 ou 2,69 g de proteína/kg0,75. As exigências de proteína metabolizável para mantença, de 4,0 g/kg0,75, não diferiram entre animais Nelore de diferentes condições sexuais.

Metabolizable protein requirements for maintenance and gain of growing goats

A database of 349 treatment mean observations, representing 3404 goats from 73 publications between 1973 and 2003, was used to determine metabolizable protein (MP) requirements for maintenance (MP m) and growth (MP g) of goats. Published CP degradation properties of feedstuffs and proportions of dietary ingredients were used to estimate MP intake (MPI, g/day), which was regressed against ADG, with both variables scaled by BW 0.75. Goats were classified as meat (≥50% Boer; 60 observations), dairy (selected for milk production; 129 observations) and indigenous (160 observations) biotypes. Because of differences ( P<0.01) among biotypes in slopes, separate regressions were initially performed—meat: MPI=2.55( S.E.=0.360)+(0.441( S.E.=0.0276)× ADG) (n=58;R 2=0.82) ; dairy: MPI=2.83( S.E.=0.344)+(0.299( S.E.=0.0238)× ADG) (n=123;R 2=0.57) ; and indigenous: MPI=3.23( S.E.=0.212)+(0.281( S.E.=0.0304)× ADG) (n=152;R 2=0.36) . Intercepts did not differ among biotypes ( P=0.37), but the slope for meat goats differed ( P<0.01) from those for dairy and indigenous goats; therefore, data sets for dairy and indigenous goats were pooled and split into development ( n=150) and evaluation ( n=125) subsets. Using the equation derived from the development data subset for dairy and indigenous goats (i.e., MPI=3.14( S.E.=0.189)+(0.285( S.E.=0.0168)× ADG) (n=144;R 2=0.67) ), MPI for the evaluation subset was predicted; regressing observed against predicted MPI of the evaluation data subset resulted in an intercept and slope not different from 0 and 1, respectively ( P>0.05). The equation from the development subset for dairy and indigenous goats was compared with the equation from the meat goat data set; there was a difference ( P<0.01) in slopes but not in intercepts ( P=0.25). Therefore, a dummy variable ( D=1 for meat goats and 0 otherwise) was used to develop a common intercept equation: MPI=3.07( S.E.=0.165)+(0.290( S.E.=0.0150)× ADG)+(0.114( S.E.=0.0162)×D× ADG) (n=202;R 2=0.75) . In conclusion, based on regression of MPI against ADG, MP m was 3.07 g/kg BW 0.75 for all biotypes of growing goats, and MP g was 0.404 and 0.290 g/g ADG for meat and other (dairy and indigenous) goats, respectively.

The Influence of Body Condition on the Fasting Energy Metabolism of Nonpregnant, Nonlactating Dairy Cows

The objective of this experiment was to investigate the effect of cow body condition score on fasting heat production. Twelve nonpregnant, nonlactating Holstein-Friesian cows were selected from within the dairy herd at the Agricultural Research Institute of Northern Ireland. Six of these animals (group A) had condition scores ≥4.5, and the remainder (group B) had condition scores <2. All cows were offered dried grass pellets at estimated maintenance energy level (0.58 MJ of metabolizable energy/kg0.75) for a minimum of 21 d. The diet also supplied 2.5 times the metabolizable protein requirement for maintenance. Following this, each cow underwent a 5-d fast in open circuit respiration calorimeters during which fasting heat production (FHP) was measured. On completion of measurement, group A was fed to reduce condition score (CS) below 2, while group B was fed to raise each individual condition score above 4.5. When the appropriate condition scores were achieved, dried grass pellets were again offered at maintenance for a minimum of 21 d, and fasting heat production was measured. It was observed that fasting heat production (MJ/kg0.75) was significantly higher for cows with low body condition (<2; ultrasonic fat depth ≤2.9mm) compared with cows displaying high body condition (≥4.5; ultrasonic fat depth ≥8.2mm). A linear relationship between condition score and fasting heat production (MJ/kg0.75) was defined by regression analysis as; FHP (MJ/kg0.75) = 0.501(SE 0.0121) – 0.030CS (SE 0.0035).

Metabolizable protein and amino acid requirements of growing cattle.

Metabolizable protein and amino acid requirements for growing cattle were estimated using data from 11 research trials. A total of 543 steers were individually fed a high-roughage diet supplemented with protein at several levels above a urea supplement control. The mean weight for all animals was 253 kg, with a range in mean initial to final weights of 200 to 316 kg, respectively. Daily gain ranged from -.04 to .89 kg. Metabolizable protein for each treatment group was calculated at the point at which the protein requirement was met. The sum of dietary escape protein (basal and supplemental) and calculated microbial protein represented metabolizable protein supplied per test protein source analyzed in each trial. Daily gain was regressed against calculated metabolizable protein flow using weighted regression analysis (r2 = .69, n = 45) to determine the metabolizable protein requirements for maintenance (3.8 x BW.75 g/d, where BW is expressed in kilograms) and growth (305 g/kg of live weight gain). Calculated metabolizable amino acid requirements as a percentage of metabolizable protein for a 253-kg animal gaining .49 kg/d were as follows: methionine, 3.0%; total sulfur amino acids, 5.8%; lysine, 8.0%; tryptophan, 1.0%; threonine, 5.2%; valine, 5.7%; isoleucine, 5.6%; leucine, 6.9%; phenylalanine, 3.9%; and histidine, 1.6%. The proposed requirements were based on live animal gain and intake of metabolizable protein and should represent the needs of the growing beef animal.