Net Energy Requirements Research Articles

Exigências de energia de borregas mestiças alimentadas com níveis crescentes de concentrado na dieta

RESUMO Objetivou-se estimar as exigências energéticas de borregas mestiças confinadas, alimentadas com níveis crescentes de concentrado na dieta. Foram avaliadas 36 borregas, com peso corporal inicial de 23,7±3,67kg. Seis animais foram abatidos no início do experimento para obtenção dos valores do grupo referência. Os demais (30 animais) foram distribuídos em cinco tratamentos: mantença (alimentação restrita com feno de capim Tifton) e suplementados com níveis crescentes de concentrado (20, 40, 60 e 80%) em base de matéria seca (seis animais por tratamento). As borregas foram abatidas quando atingiram 37,70±9,89kg. Os níveis de concentrado influenciaram a eficiência de utilização da energia metabolizável para mantença (km) e consequentemente as exigências diárias de energia metabolizável para mantença. A exigência de energia líquida para mantença de borregas mestiças em crescimento é 57 kcal/PCJ0,75/dia, em que PCJ é o peso corporal em jejum. As borregas com 20kg apresentaram exigência de energia líquida para 100g de ganho de peso diário de 465kcal/dia. As borregas com 40kg de peso corporal exigiram 930kcal/dia de energia líquida para o mesmo ganho. A exigência líquida para mantença de borregas pode ser estimada pela equação: ELm (Mcal/dia) = 0,057* PCJ0,75. A exigência líquida de energia para ganho de borregas mestiças (Mcal/dia) pode ser estimada a partir da equação: ELg = 0,524 x PVJ0,75 x GPCVZ1,21, em que GPCVZ é o ganho de peso do corpo vazio. As dietas influenciam as eficiências de usos da energia metabolizável para mantença (km) e ganho (kg).

Energy and protein requirements of weaned male and female Saanen goats.

The objective of this research was to estimate the energy and protein requirements for maintenance and growth in male (castrated and intact) and female Saanen goat kids between 15 and 30kg BW. To determine the net energy requirements for maintenance (NEm ) and the net protein requirements for maintenance (NPm ), 75 goats (25 castrated and 26 intact males and 24 females) were used. Twenty-one goats (seven castrated and eight intact males and six females) were randomly assigned for slaughter to estimate the initial empty body composition. The 54 remaining animals (18 castrated and 18 intact males and 18 females) were randomly assigned in a split-plot design using a 3×3 factorial arrangement with three sexes and three levels of intake (adlibitum and restricted feed to 75% or 50% of the adlibitum intake). Within each sex, six blocks (three goats per block) were formed and one goat was randomly assigned to each level of intake. The 75% and the 50% of adlibitum rationing were determined daily, based on the DMI of the animal fed adlibitum on the previous day. All animals within block were slaughtered when the animal fed adlibitum reached 30kg BW. The net energy requirements for gain (NEg ) and the net protein requirements for gain (NPg ) were obtained using 58 animals (20 castrated and 20 intact males and 18 females). The animals were fed adlibitum and slaughtered at targeted BW (15, 23 or 30kg). Sex did not affect NEg and NPm (277.8kJ/kg0.75 BWday and 2.98gCP/kg0.75 BWday respectively), as well as NPg (180.9±6.48 g/kgEBW gain) in Saanen goat kids. However, castrated males and females had similar NEg (varied from 12.6±0.424 to 17.9±1.38MJ/kg EBW gain), greater than intact males (varied from 9.74±0.420 to 10.7±0.984MJ/kg EBW gain), as the BW increased from 15 to 30kg.

Using glycerol for hydrogen production via sorption-enhanced chemical looping reforming: Thermodynamic analysis

Sorption enhanced-chemical looping reforming (SECLR), which combines a chemical looping reforming method (CLR) and a sorption-enhanced reforming method (SER) in a single-stage process, is proposed for the hydrogen production from glycerol. The model of the SECLR process using a solid oxygen carrier and CO2 absorbent is developed using a flowsheet simulator. The comparison between chemical looping reforming (CLR) with/without CaO sorbent is investigated. The results show that the addition of CaO sorbent provides an increase in a hydrogen concentration. The SECLR process is then deeply analyzed by considering the effect of the primary parameters on its performance in terms of hydrogen production, carbon formation and net energy requirements. The parametric analysis indicates that operating the SECLR at a steam-to-glycerol molar ratio higher than two and a sufficient calcium oxide-to-glycerol molar ratio of three can inhibit the formation of carbon. The hydrogen yield increases significantly upon increasing the reforming temperature. The required energy of the process varies with the amount of nickel oxide used as a solid oxygen carrier. The exergy analysis is considered to identify the optimal operation for self-sufficient energy and the results show that the operation of the SECLR at the nickel oxide-to-glycerol molar ratio of 1.87 is sufficient to be the most optimal condition with regard to both energy and exergy considerations.

Net energy and protein requirements for pregnancy differ between goats and sheep1

Current feeding systems for goats estimate the energy and protein requirements for pregnancy using data from sheep. The objective of this study was to predict the NE and net protein requirements for pregnancy in goats carrying single and twin fetuses and to compare these requirements with those of sheep. Data were compiled from 2 studies with dairy goats and 3 studies with sheep. These studies measured the energy content (EC) and protein content (PC) of the gravid uterus and of the mammary gland using the comparative slaughter technique. The current study was performed as a meta-analysis using an exponential model, comparing species (sheep versus goats) and litter size (single versus twin) from 50 to 140 d of pregnancy. Total EC and total PC in the gravid uterus were similar in goats and sheep carrying a single fetus. Energy and protein contents of the gravid uterus of sheep carrying twins were, on average, 29% greater than that of goats with twins from 80 to 140 d of pregnancy. During pregnancy, EC and PC of the mammary gland in goats carrying singles and twins were, on average, greater than those of sheep by 9 and 24%, respectively, for EC and by 25% for PC for both litter sizes. In conclusion, the gravid uterus and the mammary gland of goats and sheep require different amounts of energy and protein. Sheep carrying twins have the greatest daily NE and net protein requirements for pregnancy followed by goats carrying twins and both species carrying a single fetus. Therefore, it is inappropriate to adopt data from sheep to predict the net pregnancy requirements of goats, and the results found in this study could be relevant to the nutritional management of dairy goats.

Energy and protein requirements of crossbred cattle in feedlot

The objective of this study is to predict the energy and protein requirements of crossbred dairy cattle in feedlot. The study was conducted at the Unidade Acadêmica de Serra Talhada, Universidade Federal Rural de Pernambuco, Brazil with 30 bulls with a body weight of 339.1 ± 35.4 kg. Five animals were slaughtered at the end of the adaptation period to serve as the reference group; the remainder of the animals was slaughtered after 112 days. The latter group was randomly allocated to receive five treatments: 0, 17, 34, 51 and 68% of concentrate in the feed using a completely randomized design. The dietary intake of the animals that were not given concentrate was restricted to 1.5% of their body weight; these animals composed the group fed for maintenance. The body composition and empty body weight (EBW) were estimated by means of the comparative slaughter method and full dissection of a half-carcass. The results showed that for crossbred dairy bulls in confinement, the net and metabolizable energy requirements were 86.49 and 138 kcal EBW-0.75 day-1, respectively, and the efficiency of use of metabolizable energy for maintenance and gain were 62.67% and 31.67%, respectively. The net energy (NEg) and net protein (NPg) requirements for gain can be estimated using the following equations, respectively: NEg= 0.0392*EBW0.75*EBWG1.0529 and NPg= 242.34 x EBWG - 23.09 x RE. The efficiency of use of metabolizable protein for gain was 25.8%, and the protein requirement for maintenance was 2.96 g EBW-0.75 day-1. The rumen degradable protein can supply 62.44% of the crude protein requirements of feedlot dairy crossbred bulls with a body weight of 450 kg while gaining 1 kg day-1.

Energy requirements of early‐weaned Dorper cross‐bred female lambs

The net and metabolizable energy (NE and ME) requirements of Dorper cross-bred female lambs with BWs of 20-35kg were assessed in a comparative slaughter trial. Thirty-five Dorper×thin-tailed Han cross-bred female lambs weaned at ~50days of age (20.3±2.15kg BW) were used. Seven randomly selected lambs were slaughtered at the start of the trial (baseline group). An intermediate group consisting of seven randomly selected lambs fed adlibitum was slaughtered when the lambs reached an average BW of 28.5kg. The remaining 21 lambs were allotted randomly to three levels of dry matter intake: adlibitum or restricted to 70% or 40% of the adlibitum intake. All the lambs were slaughtered when the sheep fed adlibitum reached a BW of 35kg. Total body energy, nitrogen, fat, ash and moisture content were determined. In a digestibility trial, an additional 15 Dorper×thin-tailed Han cross-bred female lambs (28.7±1.75kg BW) were housed in metabolism cages and used in a completely randomized design experiment to evaluate the ME value of the diet at the three feed intake levels. The maintenance requirements for NE and ME were 245.5 and 380.3kJ/kg metabolic shrunk body weight (SBW0.75 ) respectively. The partial efficiency of energy use for maintenance was 0.645. The NE requirements for growth ranged from 1.18 to 5.18MJ/d for the lambs gaining 100-350g/d from 20 to 35kg BW. Partial efficiency of ME for growth was 0.44. In conclusion, the current study suggests that the NE requirement for maintenance and growth of Dorper early-weaned cross-bred female lambs is lower than the current AFRC and NRC recommendations.

Fatty acid profiles of intramuscular, intermuscular, external and internal fat in Polish Holstein-Friesian × Hereford bulls and steers fed grass silage-based diets supplemented with concentrates

This paper determined the impact of gender and feeding intensity on the profile of fatty acids in different types of fat deposits. The studies were conducted with 20 young bulls and 20 steers, which were Polish Holstein-Friesian and Hereford crossbreds fattened intensively – grass silage ad libitum and concentrate covered 50% of the net energy requirement in fattened cattle or semi-intensively – concentrate covered 30% of the net energy. The fatty acid profile in intramuscular, intermuscular, external and internal fat was determined. The content of intramuscular fat was lower (P < 0.001) in the longissimus muscle in the bulls (1.74%) than in the steers (3.71%). In fat of steers, the proportion of monounsaturated fatty acids was higher whereas in fat of bulls, the content of polyunsaturated fatty acids was higher. Generally the impact of the location of fat depots on the profile of fatty acids was statistically significant (P < 0.001) but there was no effect of feeding intensity.

Combining Ability of Ginning Rate and Net Ginning Energy Requirement in Upland Cotton

Combining ability describes the breeding value of parental lines to produce hybrids. The objectives of this study were to estimate specific (SCA) and general combining ability (GCA) for ginning rate and net ginning energy requirement in a set of upland cotton (Gossypium hirsutum L.) germplasm. Ginning efficiency was based on measurements of ginning energy (watt hour [Wh] kg−1 lint) and ginning rate (g lint s−1). There is little information in the scientific literature on this topic. Crosses were made in a 5 × 8 factorial design between five female and eight male diverse cotton genotypes. The experiment was conducted in a randomized complete plot design. Analysis of variance was performed using a mixed model of the GLM procedures. Even though the study indicated the presence of both additive (GCA) and nonadditive (SCA) genes controlling these traits, a preponderance of the GCA effects was evident. The cotton genotype MD 25 had the highest GCA effect for ginning rate, and AR 9317‐26 had the highest significant negative GCA effect for net ginning energy. For lowering fuzz percentage, any of the seminaked seed lines (AR 9317‐26, Tejas NS, SC 9023 NS) can be exploited. This study and other previous studies showed significant positive correlation of fuzz percentage with net ginning energy. For cultivar development, cross JJ 1145ne × SC 9023 NS may be used for improving ginning rate, crosses FM 832 × Tejas NS and JJ 1145ne × SG 747 can be used for reducing fuzz percentage, and the hybrid Phytogen 72 × TAM 98‐99ne can be exploited for improving all three traits.

Effect of dietary net energy concentration on dry matter intake and energy partition in cows in mid-lactation under heat stress.

This study aimed to determine the net energy requirement of Holstein cows in mid-lactation under heat stress. Twenty-five multiparous Holstein cows were randomly allocated to five groups corresponding to five isonitrogenous total mixed rations, with net energy for lactation (NEL ) content of 6.15 (NE-6.15), 6.36 (NE-6.36), 6.64 (NE-6.64), 6.95 (NE-6.95), 7.36 (NE-7.36) MJ/kg of dry matter (DM), respectively. Throughout the experimental period the average temperature humidity index at 07.00, 14.00 and 22.00 hours was 72.1, 88.7, and 77.6, respectively. DM intake decreased significantly with the elevated dietary NEL concentration. Fat corrected milk increased quadratically, and milk fat content and milk energy (MJ/kg) reached the greatest in the NE-6.95 group with increasing dietary NEL content. Strong correlations were found between dietary NEL content and: (i) DM intake; (ii) NEL intake; (iii) milk energy (El ); (iv) El /metabolizable energy intake (MEI); (v) El /NEL intake, as well as between NEL intake and fat corrected milk yield (FCM). The suitable net energy required for dairy cows producing 1 kg FCM ranged from 5.01 to 5.03 MJ, was concluded from the above-stated regressions. Correlation between heat production (HP) and MEI could be expressed as: Log (HP) = -0.4304 + 0.2963*MEI (n = 15, R2 = 0.99, Root Mean Square Error (RMSE) = 0.18). Fasting HP was 0.3712 MJ/kg0.75 when extrapolating MEI to zero.

Body composition and energy and protein nutritional requirements for weight gain in Santa Ines crossbred sheep.

This study was conducted to evaluate the body composition and net energy and protein requirements for weight gain in Santa Ines crossbred sheep. Thirty woolless, 4-month-old, castrated male sheep with an initial body weight (BW) of 19.77 ± 1.99kg were used. Six animals (reference group) were slaughtered after the adaptation period to estimate empty body weight (EBW) and initial body composition. The remaining 24 animals were randomly distributed among four treatments (experimental diets) and slaughtered when they reached 30.24 ± 0.78kg BW. The body composition ranged from 162.88 to 160.4g protein/kg EBW, from 59.49 to 164.23g fat/kg EBW and from 1.54 to 2.46Mcal energy/kg EBW for animals ranging between 20 and 30kg BW. The net energy requirement for Santa Ines crossbred sheep linearly increased when BW increased from 20 to 30kg. Within that same weight range, the net protein requirement for weight gain in sheep was constant, ranging from 12.61 to 12.42g/day to 100g daily weight gain.

Estimation of the maintenance energy requirements, methane emissions and nitrogen utilization efficiency of two suckler cow genotypes

Seventeen non-lactating dairy-bred suckler cows (LF; Limousin×Holstein-Friesian) and 17 non-lactating beef composite breed suckler cows (ST; Stabiliser) were used to study enteric methane emissions and energy and nitrogen (N) utilization from grass silage diets. Cows were housed in cubicle accommodation for 17 days, and then moved to individual tie-stalls for an 8-day digestibility balance including a 2-day adaption followed by immediate transfer to an indirect, open-circuit, respiration calorimeters for 3 days with gaseous exchange recorded over the last two of these days. Grass silage was offered ad libitum once daily at 0900 h throughout the study. There were no significant differences (P>0.05) between the genotypes for energy intakes, energy outputs or energy use efficiency, or for methane emission rates (methane emissions per unit of dry matter intake or energy intake), or for N metabolism characteristics (N intake or N output in faeces or urine). Accordingly, the data for both cow genotypes were pooled and used to develop relationships between inputs and outputs. Regression of energy retention against ME intake (r2=0.52; P<0.001) indicated values for net energy requirements for maintenance of 0.386, 0.392 and 0.375 MJ/kg0.75 for LF+ST, LF and ST respectively. Methane energy output was 0.066 of gross energy intake when the intercept was omitted from the linear equation (r2=0.59; P<0.001). There were positive linear relationships between N intake and N outputs in manure, and manure N accounted for 0.923 of the N intake. The present results provide approaches to predict maintenance energy requirement, methane emission and manure N output for suckler cows and further information is required to evaluate their application in a wide range of suckler production systems.

Economic impact of nutritional grouping in dairy herds

This article evaluates the estimated economic impact of nutritional grouping in commercial dairy herds using a stochastic Monte Carlo simulation model. The model was initialized by separate data sets obtained from 5 commercial dairy herds. These herds were selected to explore the effect of herd size, structure, and characteristics on the economics and efficiency of nutrient usage according to nutritional grouping strategies. Simulated status of each cow was updated daily together with the nutrient requirements of net energy for lactation (NEL) and metabolizable protein (MP). The amount of energy consumed directly affected body weight (BW) and body condition score (BCS) changes. Moreover, to control the range of observed BCS in the model, constraints on lower (2.0) and upper (4.5) bounds of BCS were set. Each month, the clustering method was used to homogeneously regroup the cows according to their nutrient concentration requirements. The average NEL concentration of the group and a level of MP (average MP, average MP+0.5SD, or average MP+1SD) were considered to formulate the group diet. The calculated income over feed costs gain (IOFC, $/cow per yr) of having >1 nutritional group among the herds ranged from $33 to $58, with an average of $39 for 2 groups and $46 for 3 groups, when group was fed at average NEL concentration and average MP+1SD concentration. The improved IOFC was explained by increased milk sales and lower feed costs. Higher milk sales were a result of fewer cows having a milk loss associated with low BCS in multi-group scenarios. Lower feed costs in multi-group scenarios were mainly due to less rumen-undegradable protein consumption. The percentage of total NEL consumed captured in milk for >1 nutritional group was slightly lower than that for 1 nutritional group due to better distribution of energy throughout the lactation and higher energy retained in body tissue, which resulted in better herd BCS distribution. The percentage of fed N captured in milk increased with >1 group and was the most important factor for improved economic efficiency of grouping strategies.

Energy requirements of Dorper×thin-tailed Han crossbred ewes during non-pregnancy and lactation

This experiment was conducted to investigate the energy requirement of Dorper×thin-tailed Han crossbred ewes during non-pregnancy and lactation. Fifteen ewes after parturition were randomly assigned to three treatments: ad libitum (100%) feed intake and 80 or 60% ad libitum intake, and another nine non-pregnant ewes were assigned to a blank control group. Digestibility trials were performed in the non-pregnant ewes and in the lactating ewes on the 20th, 50th, and 80th d of lactation. In parallel with the digestibility trial, a respirometry experiment was conducted to determine the methane and carbon dioxide production with an open-circuit respirometry system that was equipped with respiratory chambers. The net energy (NE) and metabolizable energy (ME) requirements for maintenance and growth were calculated using the carbon and nitrogen balance method. The results revealed that the carbon (C) and nitrogen (N) excretions and energy losses at faeces and urine, as well as the output of methane and CO2, increased significantly with decreasing feed intake (P<0.01). The apparent digestibilities of C in the stages of non-pregnancy and early, middle and late lactation were 55.8–58.3%, 62.5–73.8%, 64.8–71.3%, and 61.7–65.0%, respectively, and the apparent digestibilities of N were 45.2–51.3%, 73.7–82.7%, 72.8–80.5%, and 73.6–76.5%, respectively. The corresponding energy apparent digestibilities were 52.0–56.3%, 60.7–76.6%, 61.0–68.8%, and 61.4–67.7%, respectively. The ME/DE (digestible energy) values were 79.5–85.9%, 79.4–83.5%, 81.0%–85.3% and 78.6–82.9%, respectively. The maintenance requirements of NE, ME, and the efficiencies of ME utilisation for maintenance during the stages of non-pregnancy and early, middle and late lactation were 215.5, 253.1, 247.7, and 244.7 kJ kg−1 BW0.75 d, and 372.4, 327.1, 320.9, and 362.0 kJ kg−1 BW0.75 d, and 0.58, 0.77, 0.77, and 0.68, respectively. The ME requirement for the growth of non-pregnant ewes was 31.3 MJ kg−1 BW gain.

Inter-relationships among alternative definitions of feed efficiency in grazing lactating dairy cows

International interest in feed efficiency, and in particular energy intake and residual energy intake (REI), is intensifying due to a greater global demand for animal-derived protein and energy sources. Feed efficiency is a trait of economic importance, and yet is overlooked in national dairy cow breeding goals. This is due primarily to a lack of accurate data on commercial animals, but also a lack of clarity on the most appropriate definition of the feed intake and utilization complex. The objective of the present study was to derive alternative definitions of energetic efficiency in grazing lactating dairy cows and to quantify the inter-relationships among these alternative definitions. Net energy intake (NEI) from pasture and concentrate intake was estimated up to 8 times per lactation for 2,693 lactations from 1,412 Holstein-Friesian cows. Energy values of feed were based on the French Net Energy system where 1 UFL is the net energy requirements for lactation equivalent of 1kg of air-dry barley. A total of 8,183 individual feed intake measurements were available. Energy balance was defined as the difference between NEI and energy expenditure. Efficiency traits were either ratio-based or residual-based; the latter were derived from least squares regression models. Residual energy intake was defined as NEI minus predicted energy to fulfill the requirements for the various energy sinks. The energy sinks (e.g., NEL, metabolic live weight) and additional contributors to energy kinetics (e.g., live weight loss) combined, explained 59% of the variation in NEI, implying that REI represented 41% of the variance in total NEI. The most efficient 10% of test-day records, as defined by REI (n=709), on average were associated with a 7.59 UFL/d less NEI (average NEI of the entire population was 16.23 UFL/d) than the least efficient 10% of test-day records based on REI (n=709). Additionally, the most efficient 10% of test-day records, as defined by REI, were associated with superior energy conversion efficiency (ECE, i.e., NEL divided by NEI; ECE=0.55) compared with the least efficient 10% of test-day records (ECE=0.33). Moreover, REI was positively correlated with energy balance, implying that more negative REI animals (i.e., deemed more efficient) are expected to be, on average, in greater negative energy balance. Many of the correlations among the 14 defined efficiency traits differed from unity, implying that each trait is measuring a different aspect of efficiency.

Effects of diet forage proportion on maintenance energy requirement and the efficiency of metabolizable energy use for lactation by lactating dairy cows

The objective of the present study was to examine the effect of dietary forage proportion (FP) on metabolizable energy (ME) requirement for maintenance (MEm) and the efficiency of ME use for lactation (kl) in lactating dairy cows. Data used were derived from 32 calorimetric chamber experiments undertaken at our institute between 1992 and 2010, including data from 818 Holstein-Friesian cows (HF), 50 Norwegian Red cows, and 62 crossbred cows (Jersey × HF or Norwegian Red × HF). Animals were offered forage-only rations (n=66) or forage and concentrate rations (n=864) with FP ranging from 18 to 100% (dry matter basis). The effect of FP was evaluated by dividing the whole data set into 4 groups according to the FP ranges, categorized as FP <30%, FP=30 to 59%, FP=60 to 99%, and FP=100%. The MEm for individual cows was calculated from heat production minus energy losses from inefficiencies of ME use for lactation, energy retention and pregnancy, and kl was obtained from milk energy output adjusted to zero energy balance (El(0)) divided by ME available for production. Increasing FP significantly reduced ME intake and milk energy output, although the differences between the 2 low FP groups were not significant. However, increasing FP significantly increased the ratio of heat production over ME intake and MEm (MJ/kg0.75), with the exception that the increases did not reach significance in heat production/ME intake between FP <30% and FP=30 to 59%, or in MEm between FP=60 to 99% and FP=100%. However, the FP had no significant effect on the kl values, which were similar among the 4 groups of cows. The effect of FP was also evaluated using the linear mixed regression technique relating El(0) to ME intake. The results demonstrated that with a common regression coefficient (slope), the regression constants (intercepts) taken as net energy requirement for maintenance significantly increased with increasing FP. However, the increase between the 2 high FP groups did not research significance. It is concluded that increasing diet FP had no effects on kl but significantly increased maintenance energy requirement (MJ/kg0.75). These results indicate that using the current energy feeding systems to ration dairy cows managed under low input systems may underestimate their nutrient requirements, because the majority of feeding systems adopted globally do not differentiate the maintenance energy requirements between low and high forage input systems.

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.

Nutritional requirements and energy efficiency of beef cows

Review studies related to nutritional and energy efficiency of cow Nellore, data reporting requirements of the fractions of energy and protein for these animals during gestation and lactation. Little is known about the nutritional requirements of beef cows raised in tropical conditions, many data are still based animal research in European temperate conditions, under or over estimating the values that could possibly be found in Brazilian conditions. With this, we used the equations obtained by studies conducted in Brazil to produce tables with the net energy requirements, energy metabolizable, total digestible nutrients for maintenance and gain weight, based on cows in different stages of pregnancy, lactation and size body. As for the protein fractions. Based on the data obtained it is concluded that in the last third of gestation is the significant increase in demand for energy and protein, and lactating cows have a demand that exceeds their ingestive capacity, for a gain of 1 kg / day with CMS around 2% of body weight.

Sistema de cria x exigências nutricionais: fêmeas de corte e bezerros do nascimento ao desmame

Objective was to evaluate the studies on the nutritional requirements of cows and calves Nellore, seeking data requirements of energy and protein fractions for these animals from birth to weaning. There are few publications that seek nutritional requirements of cows and beef calves raised in tropical conditions. There is variation between the reported requirement for energy and protein for animals of European origin and zebu. We used the equations obtained by studies conducted in Brazil to produce tables with the net energy requirements, energy intake, total digestible nutrients for maintenance and gain weight, based on cows in different stages of lactation and body size. For lactating calves different rates of gain and body weights.As for the protein fractions. Based on the data obtained it is concluded that cows with CMS approximately 2% of body weight can not gain 1 kg / day weight, since the demand for nutrients exceeds the ingestive capacity. Calves are weaned at about 7 months and weight around 200 kg should receive supplementation from the 2nd month of life.

Effects of excessive energy intake and supplementation with chromium propionate on insulin resistance parameters, milk production, and reproductive outcomes of lactating dairy cows

This experiment compared insulin resistance parameters, milk production, and reproductive outcomes in: (1) lactating dairy cows consuming adequate or excessive energy, and (2) lactating dairy cows consuming excessive energy and receiving or not Cr-propionate supplementation. Seventeen primiparous and multiparous, non-pregnant, lactating Holstein cows (initial days in milk=76±2) were assigned on d 0 to: (1) concentrate intake to meet their requirements of net energy for lactation (NEL) without Cr supplementation (MAN; n=5), (2) concentrate intake to exceed their NEL requirements without Cr supplementation (HIGH; n=6), and (3) HIGH with 2.5g/d of Cr propionate (HIGHCR; n=6). Throughout the experiment (d 0 to 210), cows were offered corn silage for ad libitum consumption, and individually received a corn-based concentrate twice daily. Concentrate intake was formulated to allow diets to provide 100% of daily NEL requirements of MAN, and 160% of daily NEL requirements of HIGH and HIGHCR cows. Cow BW, BCS, and milk production were recorded weekly. Blood samples were collected weekly, prior to and at 2 and 4h after the morning concentrate feeding. Six glucose tolerance tests (GTT) were performed, every 42d, by infusing cows with 0.5g of glucose/kg of BW. Follicle aspiration for in vitro embryo production was performed via transvaginal ovum pick-up 2d after each GTT. Increase in BCS from d 0 to 210 was greater (P≤0.04) in HIGH and HIGHCR vs. MAN. Milk production was similar (P=0.92) between treatments. Within weekly samples, serum non-esterified fatty acids concentration were greater (P≤0.05) for MAN vs. HIGH and HIGHCR. Serum insulin concentrations and insulin:glucose ratio were often greater (P≤0.05) for HIGH, intermediate for HIGHCR, and lesser for MAN (treatment×day interaction, P<0.01). During the GTT, serum insulin concentrations and insulin:glucose ratio were greater (P≤0.05) for HIGH compared with HIGHCR and MAN from 10 to 60min relative to the time of glucose infusion. Proportion of embryo produced per oocyte collected was greater (P≤0.02) for MAN vs. HIGH and HIGHCR, and similar (P=0.59) between HIGH and HIGHCR. In conclusion, lactating cows consuming excessive concentrate and NEL experienced increased insulin resistance and reduced proportion of embryo produced per oocyte collected compared with cows consuming adequate amounts of energy, whereas Cr-propionate supplementation was effective in alleviating insulin resistance caused by excessive NEL intake.

Energy requirements for growth of pubertal female Saanen goats.

Previous research on energy requirements of female Saanen goats, using the factorial approach, has not considered the specific requirements for maintenance and growth during the pubertal phase. Thus, the purpose of this study was to estimate energy requirements for maintenance (Trial 1) and growth (Trial 2) of non-pregnant and non-lactating female Saanen goats at the pubertal phase from 30 to 45kg. In Trial 1, the net energy requirements for maintenance (NEm ) were estimated using 18 female Saanen goats randomly assigned to three levels of intake: adlibitum, and 70% and 40% of adlibitum intake. These animals were pair-fed in six slaughter groups, each consisting of one animal for each level of intake. In Trial 2, the net energy requirements for growth (NEg ) were estimated using 18 female Saanen goats, which were fed adlibitum and slaughtered at targeted BW of 30, 38 and 45kg. The NEm was 52kcal/kg(0.75) of BW. The NEg increased from 3.5 to 4.7Mcal/kg of BW gain as BW increased from 30 to 45kg. Our results suggest that the guidelines of the major feeding systems for the entire growth phase may not be adequate for females at pubertal phase.