Metabolizable Energy Consumption Research Articles

Construction and Simulation of Biomechanical Model of Human Hip Joint Muscle-Tendon Assisted by Elastic External Tendon by Hill Muscle Model.

Based on the Hill muscle model (HMM), a biomechanical model of human hip muscle tendon assisted by elastic external tendon (EET) was preliminarily established to investigate and analyze the biomechanical transition between the hip joint (HJ) and related muscle tendons. Using the HMM, the optimal muscle fiber length and muscle force scaling variables were introduced by means of constrained optimization problems and were optimized. The optimized HMM was constructed with human parameters of 170 cm and 70 kg. The biomechanical model simulation test of the hip muscle tendon was performed in the automatic dynamic analysis of mechanical systems (ADAMS) software to analyze and optimize the changes in the root mean square error (RMSE), biological moment, muscle moment distribution coefficient (MDC), muscle moment, muscle force, muscle power, and mechanical work of the activation curves of the hip major muscle, iliopsoas muscle, rectus femoris muscle, and hamstring muscle under analyzing the optimized HMM and under different EET auxiliary stiffnesses from the joint moment level, joint level, and muscle level, respectively. It was found that the trends of the output joint moment of the optimized HMM and the biological moment of the human HJ were basically the same, r2 = 0.883 and RMSE = 0.18 Nm/kg, and the average metabolizable energy consumption of the HJ was (243.77 ± 1.59) J. In the range of 35%∼65% of gait cycle (GC), the auxiliary moment showed a significant downward trend with the increase of EET stiffness, when the EET stiffness of the human body was less than 200 Nm/rad, the biological moment of the human HJ gradually decreased with the increase of EET stiffness, and the MDC of the iliopsoas and hamstring muscles gradually decreased; when the EET stiffness was greater than 200 Nm/rad, the increase of the total moment of the extensor muscles significantly increased, the MDC of the gluteus maximus and rectus muscles gradually increased, and the gluteus maximus and hamstring muscle moments and muscle forces gradually increased; the results show that the optimized muscle model based on Hill can reflect the law of human movement and complete the simulation test of HJ movements, which provides a new idea for the analysis of energy migration in the musculoskeletal system of the lower limb.

ФОРМУВАННЯ ПРОДУКТИВНИХ ОЗНАК У ТЕЛИЦЬ ТА НЕТЕЛЕЙ ПІД ВПЛИВОМ ПАРАТИПОВИХ ФАКТОРІВ

The influence of age and live weight at conception on the consumption of metabolizable energy and crude protein during 6 months of pregnancy, processes of their growth and development was studied. The gain of live weight of springer heifers during the first three months of pregnancy was determined to be 67,0±3,66 kg in group I, 65,0±5,26 kg in group II and 49,0±4,40 kg in group III. Studying the growing power of the animals during 0-3 months (92 days) of pregnancy, the springer heifers of groups I and II were found to be superior to the herdmates of the group III by 196g and 174g or 26,9 and 24,4% (p<0,01) in terms of the average daily gain. Comparing the characteristics of the live weight gain at 4-6 months (92 days) of pregnancy, the springer heifers of groups I and II were found to be significantly superior to their analogues in group III by 29.0 and 28.0 kg. The springer heifers of groups I and II outweighed their herdmates of group III by 316 and 305 g or 43,4% and 47,5% (p<0,001) in terms of the average daily gain. It is necessary to underline that animals of groups I and II had higher gain of live weight during the whole experimental period by 47,0 and 43,0 kg or 58 and 53% as compared to the analogues of group III. According to the results of multicriteria analysis, for group I the objective function was determined to be lower and was 0.0359 on the examined criteria, while the objective functions of groups II and III were worse at 1.4 and 12.1 respectively. At the same time, the animals in group II were 8.6 times superior to their analogues in group III. It indicates the superiority of animals in groups I and II with a productive mating age of 14.8-15.3 months and a live weight of 373-414 kg. They had a more intensive gain of live weight during pregnancy and spent less energy and crude protein feed per kilo of gain. The linear, partial quadratic and partial quadratic regressions were developed to describe the correlation between the increase of live weight of heifers and their age and live weight at the time of conceiving and the consumed metabolizable energy and crude protein for 6 months of pregnancy. The season of the year was determined to have no significant impact on the heifers' development during the pregnancy period in the herd and their further milk productivity.

Relationships between digestible energy and metabolizable energy in current feedlot diets.

It is commonplace that metabolizable energy (ME) is calculated from digestible energy (DE) as DE × 0.82. However, recent published literature suggests that the relationship between DE and ME is variable depending on the type of diet used, and is typically > 0.90 when high-concentrate diets are fed. Literature means were compiled from 23 respiration calorimetry studies where total fecal and urine collections were conducted and gaseous energy was measured. The relationship between experimentally observed and predicted ME (DE × 0.82) was evaluated using these previously reported treatment means. Additionally, a previously published linear regression equation for predicting ME from DE was also evaluated using a residual analysis. Published (Hales, K. E., A. P. Foote, T. M. Brown-Brandl, and H. C. Freetly. 2017. The effects of feeding increasing concentrations of corn oil on energy metabolism and nutrient balance in finishing beef steers. J. Anim. Sci. 95:939-948. doi:10.2527/jas.2016.0902 and Hemphill, C. N., T. A. Wickersham, J. E. Sawyer, T. M. Brown-Brandl, H. C. Freetly, and K. E. Hales. 2018. Effects of feeding monensin to bred heifers fed in a drylot on nutrient and energy balance. J. Anim. Sci. 96:1171-1180. doi:10.1093/jas/skx030) and unpublished data (K. E. Hales, unpublished data) were used to develop a new equation for estimating ME from DE (megacalories/kilogram [Mcal/kg] of DM; ME = -0.057 ± 0.022 DE2 + 1.3764 ± 0.1197 DE - 0.9483 ± 0.1605; r 2 = 0.9671, root mean square error = 0.12; P < 0.01 for intercept, P < 0.01 for linear term, and P < 0.01 for quadratic term). To establish a maximum biological threshold for the conversion of DE to ME, individual animal data were used (n = 234) to regress the ME:DE on DE concentration (1.53 to 3.79 Mcal DE/kg). When using experimentally derived data and solving for the first derivative, the maximum biological threshold for the conversion of DE to ME was 3.65 Mcal DE/kg. Additionally, the quadratic regression (equation 1) was used to predict ME from a wide range of DE (1.8 to 4.6 Mcal/kg). The ME:DE ratio was then calculated by dividing predicted ME by DE. The maximum biological threshold for the conversion of DE to ME was estimated by solving for the first derivative and was 3.96 Mcal DE/kg. In conclusion, this review suggests that the relationship between DE and ME is not static, especially in high-concentrate diets. The equation presented here is an alternative that can be used for the calculation of ME from DE in current feedlot diets, but it is not recommended for use in high-forage diets. The maximization of ME in current diets, maximum biological threshold, occurs between 3.65 and 3.96 Mcal DE/kg in the diet, which based on these data is approximately 3.43 to 3.65 Mcal/kg of ME consumption.

Assessment of behavior and feeding intake of dogs fed with soybean hulls

The diet composition can promote satiety and interfere in animal behavior. The aim of this study was to evaluate the behavior of dogs after ingestion of diet without soybean hull (0%SH) and a diet with soybean hulls (16%SH), as well as the daily consumption of food (supplied - leftovers) and metabolizable energy (ME) intake of diets. Twelve Beagle dogs were distributed completely randomly between two treatments, being six dogs consuming the 0%SH diet and six dogs 16%SH diet. The behavioral test consisted of observing the animals during 24 uninterrupted hours at intervals of 10 minutes at the end of 28 days of consumption of the diets. General behaviors were observed such as alert, scratching, stereotypical behavior, sleep, hygiene, walking, idle lying, idle standing, idle sitting and socialization. There was a reduction in scratching behaviors (P 0.05), but the ME intake was lower (P<0.001) in dogs that received a diet with 16%SH. The use of 16%SH in the diet reduces the ME intake and undesirable behavior in dogs.

Metabolizable energy for broilers with different genetic growth potentials under a free-range system

The objective of this study was to evaluate the effects of different levels of metabolizable energy (ME) on performance parameters and carcass characteristics in slow-growing (experiment 1) and fast-growing (experiment 2) broilers in a free-range system. Were evaluated broilers from 35 to 70 days old in experiment 1 and 28 to 49 days old in experiment 2. A completely randomized experimental design was employed in both experiments, with five treatments and four replicates totaling 20 experimental units containing 15 broilers each. The treatments consisted of rations that had increasing metabolizable energy levels obtained by the substitution of soybean oil in the basal diet for the inert sand ingredient. The metabolizable energy levels studied in experiment 1 were 2700, 2800, 2900, 3000 and 3100 kcal/kg, and in experiment 2, they were 2800, 2900, 3000, 3100 and 3200 kcal/kg. In experiment 1, there was a linear (P&lt;0,05) reduction in consumptionwith the increase in the metabolizable energy level, and a quadratic effect (P&lt;0,05) on the feed conversion was observed, which was estimated as 3046 kcal/kg the level that resulted in a better feed conversion of 2.648. In experiment 2, the metabolizable energy level exerted a significant quadratic effect (P&lt;0,05) on the feed intake and metabolizable energy consumption, with a maximum feed intake (3361.27 g) estimated for 2842 kcal/kg, and the maximum energy intake was estimated at 10020 kcal. The feed conversion decreased linearly (P&lt;0,05) with there was an increase in the studied levels. For broilers reared in a free-range system, for better feed conversion, the recommended metabolizable energy levels are as follows: for slow-growing broilers from 35 to 70 days of age, 3046 kcal/kg, and 3200 kcal/kg is recommended for fast-growing broilers from 28 to 49 days of age.

Energy and tannin extract supplementation for dairy cows on annual winter pastures

Energy supplementation can increase the consumption of metabolizable energy and substrate for microbial growth, while condensed tannins aid in increasing the duodenal flow of foodborne metabolizable proteins. The objective of this study was to evaluate the effects of energy supplementation and the inclusion of tannin extract (TE) from Acacia mearnsii (Weibull Black, Tanac S. A., Montenegro, Brazil) on the production performance of dairy cows grazing on winter pastures. Nine multiparous Holstein cows in mid lactation were distributed in a 3 × 3 Latin square experimental design over three periods of 28 days (21 adaptation and 7 sampling). The treatments were: without supplementation (WS), supplementation with 4 kg of corn grain (CG), and corn grain + 80 g of tannin extract (TE). The dry matter (DM) intake from pastures was similar among treatments, but the consumption of DM of the supplement was higher in the CG treatment than that in the TE treatment. The total DM intake was higher for the supplemented animals (17.3 kg?day-1) than that for the unsupplemented animals (14.9 kg?day-1) and in the TE treatment (17.7 kg?day-1) than in the CG treatment (16.7 kg day-1). Milk production increased from the unsupplemented to the supplemented animals (20.9 to 23.5 kg, respectively), while the content of urea N in the milk decreased (12.6 to 10.5 mg?100 mL-1, respectively). There were no differences in milk production or content of milk urea N between the CG and TE treatments. Energy supplementation is a tool for improving the nutritional profile and the performance of dairy cows in mid lactation grazing on annual winter pastures, while tannin extract aids in improving the energy balance.

Fodder resources and feeding of semifree bison (Bison bison) on a steppe pasture in the Western Manych valley

In 2012–2013, the species composition, aboveground phytomass, and nutrition of freely ranging bison were investigated on a natural steppe pasture of the Western Manych valley. The aboveground mass of plants on the investigated pasture varied from 16.1 to 19.4 c/ha. The composition of the plants consumed by bison and their share in the bison’s diet were determined by microscopy of feces. In the snowless season, graminoids was the basis of the bison’s diet (79–87%). The use of forbs varied from 4.7 to 17.5%. Sedges were present in the forage in summer; they amounted to 6.5–15.4%. The quantitative assessment of the food selectivity was determined using the ratio of the share of a plant species in the diet to its portion in the plant community of the pasture. The most selected were Festuca valesiaca (the selectivity is 12.0), Agropyron sp. sp. (1.7), Polygonum patulum (1.2), and Carex sp. sp. (1.1). In other forage plants (Poa bulbojsa, Tanacetum achileifolium, and other forbs), the selectivity was 0.01–0.3. The nutritional value of fodder vegetation and food indexes (daily intake, digestibility of forage, consumption of metabolizable energy) were estimated. The digestibility was determined by the ratio of inert (undigestible) components (silicon, lignin) in the diet to their amount in the feces. The daily intake of forage was calculated based on the mass of released feces and digestibility of forage. In the snowless season, bison consumed from 6.3–7.0 to 9.2–9.9 kg/ind. (dry weight) per day. The maximum consumption (9.9 kg/ind.) was observed in summer. The digestibility of forage changed from 45 to 53% (the average is 50%). The consumption of metabolizable energy in different seasons varied from 0.60 to 0.91 MJ/kg0.75/day, which corresponded to maintenance energy.

ORGANIC TRACE ELEMENT COMPLEX FOR CALVES FEEDING

Trace elements are commonly used in the form of inorganic salts poorly digested by ruminants due rumen microflora, which transits its greater part into indigestible and insoluble form. Trace elements in the form of chelates are supplied with amino acids and peptides, and used by the body much more efficiently. Inclusion of organic trace element complex (OMEK) in compound feed KR–1 in the amount of 10% of the existing standards for trace elements content in typical formulations for growing young cattle for meat has a positive impact on palatability of feeds, morphological and biochemical composition of blood and animals’ performance, economic efficiency of calves fattening. Use of organic trace element complex in compound feeds KR–1 increases concentration of total protein in blood by 8 – 12% (P &lt; 0.05), reduces the amount of urea by 11 – 16% (P &lt; 0.05). Comparative analysis showed that animals in experimental group II used the feeds more efficiently. Metabolizable energy consumption per 1 kg of weight gain made 33.7 MJ against 37.4 MJ in the control group or by 9.9% lower, the same trend is established for digestible protein cost – by 10%. Inclusion of OMEK in compound feed KR–1 for young cattle ensures average daily weight gain increase by 12.3% (P &lt; 0.05), decreased of feed cost per 1 kg of weight gain by 10%. Use of organic trace element complex helps to decrease the cost price of weight gain, by 9.0% and obtain extra profit of $37.2 USD per one animal during the experimental period.

Структура расхода обменной энергии и влияние основного обмена на молочную продуктивность

Структура расхода обменной энергии и влияние основного обмена на молочную продуктивность

Feeding programs and their effects on broiler performance and economic indexes

Different feeding programs were evaluated with the aim of comparing broiler performance and economic indexes. Twelve hundred birds were subjected to a completely randomized experimental design with 5 treatments and 8 replicates with 30 birds per experimental unit. The feeding programs were based on Cobb Vantress manual (T1), NRC values (T2), and previous research by Rostagno (T3, T4) and a modified Rostagno diet (T5). Feed intake, BW, weight gain, feed conversion, viability, energy consumption, caloric conversion, productive efficiency index, and carcass characteristics were evaluated in the period from 1 to 46 d of age. The gross trade margin was calculated for economic analysis. The results were evaluated based on a variance analysis, and the Tukey test was used to compare treatment means. For performance characteristics, metabolizable energy consumption was similar for treatments T1, T3, and T5, but was higher for treatment T2 than T1 and T4. Caloric conversion was higher for treatment T2 than other treatments, and no differences were noted for other performance characteristics. It was concluded that the T1 feeding program, based on the Cobb Vantress manual, resulted in higher trade gross margin ($0.821), whereas T2, based on NRC values, was lower ($0.762). Therefore, the recommendations contained in the Cobb Vantress manual should be used as a means of achieving greater profitability in broiler production.

Maize supplementation of Pelibuey sheep in a silvopastoral system: fodder selection, nutrient intake and resilience against gastrointestinal nematodes

This trial evaluated the effect of maize supplementation on the ingestive behavior, nutrient intake and the resilience against gastrointestinal nematode (GIN) infection of hair sheep in a silvopastoral system containing tropical grasses and legume trees. In addition, it attempted to determine the metabolic cost of the natural GIN infection in supplemented and non-supplemented animals. Twenty-nine 3-month-old lambs (male and female), raised nematode free, were allocated to four groups: I-NS (infected, not supplemented, n = 8), I-S (infected, supplemented with maize at 1.5% live weight (LW), n = 7), T-NS (treated with moxidectin 0.2 mg/kg LW every 28 days, and not supplemented, n = 7) and T-S (treated with moxidectin and supplemented with maize at 1.5% LW, n = 7). During the 70-day trial, fodder intake, fodder selection, LW change (LWC), red blood cell counts (RBC), hemoglobin (Hb), hematocrit (Ht) and eggs per gram of feces (EPG) were measured every 14 days. Supplement consumption was recorded daily. Metabolizable energy (ME) and protein (MP) consumption from the feeds were estimated. Maize supplementation helped to improve the resilience of hair sheep lambs against GIN infections. The I-S and T-NS groups showed similar LWC, RBC, Hb and Ht (P > 0.05) and both were higher than those in the I-NS group (P < 0.05). No difference was found in EPG between the I-NS and the I-S groups (P > 0.05). No effect of sex was observed in the different variables. Although all groups showed low dry matter intake (DMI) (< 2% LW), supplemented groups (T-S and I-S) showed higher total DMI (fodder + maize; P < 0.05), hence higher ME and MP intakes than the non-supplemented groups (T-NS and I-NS). All groups showed similar fodder selection patterns. The estimated metabolic cost of parasitism was ME = 0.70 MJ/day and MP = 9.2 g/day in the I-S animals. Meanwhile, the cost in the I-NS animals was ME = 1.46 MJ/day and MP = 12.71 g/day. Maize supplementation was an economically viable strategy to control GIN compared with no intervention.

Quantitative characteristics of nutrition in free-ranging reindeer (Rangifer tarandus) and musk oxen (Ovibos moschatus) on Wrangel Island

In 2004 to 2006, studies on free-ranging reindeer and musk oxen on Wrangel island were performed to estimate the nutrient value, daily intake, and digestibility of forage in different seasons of the year. Forage digestibility was determined from the ratio between the contents of indigestible components (lignin) in forage and animal feces. Daily forage intake was calculated from data on daily feces excretion and forage digestibility. The amount of feces and parameters of life activity of individual animals were estimated by following their 24-hour tracks. The results show that the daily intake of forage (dry weight) in musk oxen amounts to 7.8 kg in the summer period and decreases to 6.1 kg in the snow period (March–April). Grazing reindeer in the snow period consume 3.9 kg of forage per day. Forage digestibility in reindeer reaches 56% in March to April and decreases to 52% in June. In musk oxen, forage digestibility in different seasons (March, June, September) varies within a similar range (53–57%). Nutrition parameters (diet composition, forage intake rate and digestibility) of reindeer and musk oxen on grazing grounds of Wrangel Island are similar. Metabolizable energy consumption in both animals during the winter period is at the maintenance level (917–930 kJ/kg0.75 body weight). In the summer period, this parameter in musk oxen increases to 1163 kJ/kg0.75 body weight to meet the energy demand of the animals.

Efeito do consumo de energia e óleo vegetal sobre a qualidade de ovos de poedeiras semipesadas

The main objective of this trial was to find out the best metabolizable energy (ME) consumption in order to improve the egg quality. 288 laying hens Hissex Brown aging 30 weeks were randomly assigned in a 3x3 factorial design with nine treatments and four replications each, being respectively 280, 300 and 320 kcal/bird/day and three levels of oil (0.00, 0.75 and 1.5 g/day). Daily feed intake was based on 115, 110 and 105 g/bird/day to achieve the desirable levels of ME and oil. The rations were formulated to furnish the following amounts: protein 18g; Ca 42 g, total phosphorus 0.66; methionine 0.40 g;methionine+cystine 0.73 g and lysine 0.83. No significative statistical differences were detected (P>0.05) for mean egg weight (g) and specific gravity. There was significant quadratic effect of the energy consumption on the egg shell percentage (%), with decrease of the percentage among 280 and 300kcal of ME/bird/day and increase of the same among 300 and 320kcal of ME/bird/day, significant reduction of the albumen percentage (%) and increase of consume and Haught Unit (UH) which decreased as daily the yolk percentage with the increase in the oil consumption energy intake increased (P<0.05). There was a significative interaction between energy and oil KEY WORDS: Egg quality, energy, semi heavy layers, vegetable oil.

Sex‐dependent regulation of hypothalamic neuropeptide Y‐Y1 receptor gene expression in moderate/high fat, high‐energy diet‐fed mice

In this study we investigated whether long-term consumption of a moderate/high fat (MHF), high-energy diet can affect the gene expression of the Y(1) receptor (Y(1)R) for neuropeptide Y (NPY) in the dorsomedial (DMH), ventromedial (VMH), arcuate (ARC) and paraventricular (PVN) hypothalamic nuclei of male and female Y(1)R/LacZ transgenic mice, carrying the murine Y(1)R promoter linked to the LacZ gene. MHF diet-fed male mice showed an increased consumption of metabolizable energy that was associated with a significant increase in body weight as compared with chow-fed controls. In parallel, consumption of a MHF diet for 8 weeks significantly decreased Y(1)R/LacZ transgene expression in the DMH and VMH of male mice whereas no changes were found in the ARC and PVN. Leptin treatment reduced body weight of both MHF diet- and chow-fed male mice but failed to prevent the decrease in Y(1)R/LacZ transgene expression apparent in the DMH and VMH of male mice after 8 weeks of MHF diet intake. Conversely, no significant changes of metabolizable energy intake, body weight or hypothalamic beta-galactosidase expression were found in MHF diet-fed female Y(1)R/LacZ transgenic mice. A gender-related difference of Y(1)R/LacZ transgenic mice was also observed in response to leptin treatment that failed to decrease body weight of both MHF diet- and chow-fed female mice. Results herein demonstrate that Y(1)R/LacZ FVB mice show a sexual dimorphism both on energy intake and on nucleus-specific regulation of the NPY Y(1)R system in the hypothalamus. Overall, these results provide new insights into the mechanism by which diet composition affects the hypothalamic circuit that controls energy homeostasis.

Productive Performance and Digestive Tract Size of Broiler Chicks Fed a Conventional or an all Vegetable Ingredients Diet

Al-Masri, M.R. 2006. Productive performance and digestive tract size of broiler chicks fed a conventional or an all vegetable ingredients diet. J. Appl. Anim. Res., 30: 81–84. Experiments were carried out to study the effect of feeding broiler chicks with added meat-bone meal (conventional diet) or without (vegetable diet) on feed efficiency (FE), metabolizable energy efficiency (MEE) and biological aspects of digestive organs during 1–53 days of chicks' age. The two diets had no significant (P<0.05) effects on FE and MEE. The FE values were positively correlated to the metabolizable energy consumption values (R=0.77). Changing from a diet containing meat-bone meal to an all vegetable ingredients had no negative effect on the biological aspects of broilers' digestive tract (relative weights of crop, proventriculus, gizzard, duodenum, jejunum, ileum, caeca, colon, pancreas and liver). An all vegetable diet is recommended for broiler production.

Productive performance of broiler chicks fed diets containing irradiated meat–bone meal

Experiments were carried out to study the changes in the values of feed efficiency (FE), total protein efficiency (TPE) and metabolizable energy efficiency (MEE) of broiler chicks fed during four age periods (14–21, 21–28, 28–35 and 35–42 days). Five experimental diets were similar in composition but different in the irradiation dose (0, 5, 10, 25 or 50 kGy) applied to the meat–bone meal content of each diet. The results indicated that feeding of broiler chicks on irradiated meat–bone meal (5–50 kGy) had no significant ( P>0.05) effects on FE, TPE, MEE and body weight gain during the four experimental age periods. The average values of the FE (feed consumption/weight gain), TPE (weight gain/total protein consumption) and MEE (metabolizable energy consumption in MJ/kg gain) were 1.96, 2.59 and 23.13, respectively. The values of FE and MEE increased while TPE decreased significantly ( P<0.05) with age. The pooled FE value was 1.60 during the 14–21 days of age and increased to 2.66 from 35–42 days of age. However, the TPE value was 3.01 during the 14–21-day age period and decreased to 1.82 over the 35–42-day age period. The energy consumption value to produce one kg of body weight increased during the 35–42-day period by 7.71–12.72 MJ/kg gain in comparison with that from the other experimental age periods. Weight gain rate decreased significantly ( P<0.05) during the 35–42-day period (66 g/week/bird) when compared with the rate observed during the 14 through 35-day age period.

Net requirements of protein and energy for maintenance of wool and hair lambs in a tropical region

The objective of this work was to evaluate the total endogenous N losses, and protein and energy net requirements for maintenance in growing lambs. Thirty-four castrated lambs, 17 F1 Ideal X Ile de France wool and 17 Santa Inês hair lambs, averaging 20±0.14 kg BW, were used in the experiment. Five animals from each genotype were slaughtered at the beginning of the experiment and taken as controls. Diets (D) were composed of concentrate mix (C) and Cynodon sp. c.v. Tifton 85 hay (R), combined in three different ratios: D1=60C:40R; D2=40C:60R and D3=20C:80R. Animals of each group of three lambs, that showed BW of 20 kg at the beginning of the dietary regimen, were slaughtered when one of them reached 35 kg, what always happened to be the one fed with D1. Total endogenous N losses estimated for wool lambs were 250 mg N/kg BW 0.75. For hair lambs, total endogenous N losses reached 324 mg N/kg BW 0.75. Hair lambs showed higher ( P<0.01) (29.9%) net requirements of protein for maintenance than wool lambs. In contrast, net energy (NE) requirement for maintenance was similar ( P>0.05) for both genotypes (74.27 kcal/kg BW 0.75 per day), the average of the antilog of the two intercept values obtained from the estimated regression equations of heat production for zero metabolizable energy (ME) consumption. Further studies should be done to check if this trend is also true for metabolizable energy and protein in animals exhibiting BW gains in tropical region.

Efeito da inclusão do caroço de algodão sobre o consumo, digestibilidade e balanço da energia em dietas para ovinos

Vinte e cinco carneiros castrados, em delineamento inteiramente ao acaso, foram utilizados para avaliar o efeito de níveis crescentes de inclusão (0, 12, 24, 35 e 45%) de caroço de algodão integral (Gossypium hirsutum) à dieta básica de feno de "Tifton 85" (Cynodon spp.) sobre a digestibilidade aparente da energia bruta, sobre os consumos de energia digestível e metabolizável por unidade de tamanho metabólico, e sobre o balanço energético. O consumo de energia digestível aumentou até o nível de 24% de inclusão de caroço de algodão integral (192,58 Kcal/kg0,75/dia). O balanço energético foi positivo para todas as dietas em virtude do atendimento aos requisitos energéticos de mantença. Os animais que receberam 24% de inclusão do caroço de algodão integral à dieta tiveram maior consumo de energia e melhores digestibilidade e balanço energético.

Eficiência de Utilização da Energia Metabolizável para Mantença e Ganho de Peso e Exigências de Energia Metabolizável e de Nutrientes Digestíveis Totais de Bovinos Nelore Não-Castrados

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%). O consumo de matéria seca (MS) suficiente para manter o equilíbrio de energia foi calculado dividindo-se o consumo de energia metabolizável (EM) suficiente para mantença, de 131,92 kcal/ kg PCVZ0,75, pela concentração de EM (kcal/kg de MS) da dieta, em cada tratamento. A concentração de energia líquida de cada ração para mantença (ELm) foi obtida dividindo-se a produção de calor em jejum, 83,70 kcal/kg PCVZ0,75, pelo consumo de MS, para manter o equilíbrio de energia, expresso em g de MS/kg PCVZ0,75. O consumo de energia metabolizável (EM) suficiente para mantença e a produção de calor em jejum foram obtidos experimentalmente com os mesmos animais deste experimento. A concentração de ELg foi calculada dividindo-se a energia retida por dia, em kcal/kg PCVZ0,75, pelo consumo de MS acima das necessidades de mantença, expresso em g MS/kg PCVZ0,75. As eficiências de utilização da EM (EUEM) para mantença (km) e ganho de peso (kf) foram estimadas a partir da relação entre os teores de energia líquida, para mantença ou ganho, respectivamente, em função da EM da dieta, e a kf também foi estimada como o coeficiente de regressão linear entre a energia retida e o consumo de EM, juntamente com os dados relativos aos animais designados de mantença. Os requisitos de EM para mantença e ganho foram obtidos pelas relações entre as exigências líquidas e as respectivas EUEM. As exigências de nutrientes digestíveis totais (NDT) foram calculadas dividindo-se as exigências de EM por 0,82, obtendo-se as exigências de energia digestível (ED) e, posteriormente, dividindo-se as exigências de ED por 4,409. A eficiência de utilização da EM para mantença (km) foi calculada em 0,63. As eficiências de utilização da EM para ganho (kf) foram estimadas em 0,30; 0,35; 0,38; e 0,43, respectivamente, para as concentrações de EM da dieta de 2,65; 2,84; 2,92 e 2,90 Mcal/kg de MS, obtidas para os níveis de 20, 40, 60 e 80% de concentrado. As exigências de EM, ED e NDT para mantença foram calculadas em 132,9 e 162,0 kcal/ kg PCVZ0,75 e 36,7 g/kg PCVZ0,75, respectivamente.

A study on the variation of feed efficiency in station tested beef bulls

The records of 282 young beef bulls from eight breeds tested from November 1981 to April 1987 at the Ellerslie Bull Test Station, Alberta, Canada, were used to study the variation in feed efficiency among young performance-tested bulls. Considerable variation existed among the animals in both residual metabolizable energy consumption and residual dry matter consumption. The heritability estimates for residual metabolizable energy consumption and residual dry matter consumption were 0.33 and 0.29, respectively. In addition, residual metabolizable energy consumption and residual dry matter consumption were moderately correlated (r = 0.43) with conventional feed-to-gain ratio, indicating that conventional feed-to-gain ratio only accounted for 18% of the variation in residual metabolizable energy consumption or residual dry matter consumption. It was, therefore, worthwhile to use residual metabolizable energy consumption or residual dry matter consumption as separate measures of feed efficiency. For rapid improvement in feed efficiency in beef cattle, selection pressure should be applied to both growth traits and residual energy consumption or residual dry matter consumption. Multi-trait optimum restricted selection indices and similar selection procedures may serve as useful means in balanced selection programs to improve the productivity of beef cattle. Key words: Feed efficiency, residual ME consumption, beef bulls