Metabolizable Energy For Gain Research Articles

California net energy system for Bos taurus indicus.

The California net energy system (CNES) was the reference for the development of most energy requirement systems worldwide, such as Nutrient Requirements of Beef Cattle (NASEM, Nutrient requirements of beef cattle, 8th Revised ed, 2016) and Brazilian Nutrient Requirements of Zebu and Crossbred Cattle (Valadares Filho, S. C., L. F. C. Silva, M. P. Gionbelli, P. P. Rotta, M. I. Marcondes, M. L. Chizzotti, and L. F. Prados, BR-CORTE: nutrient requirements of zebu and crossbred cattle, 3rd ed, 2016). This review aimed to compare methods used by NASEM and BR-CORTE to estimate the energy requirements for beef cattle. The net energy requirements for maintenance (NEm) of BR-CORTE is based on empty body weight (EBW), whereas NASEM uses shrunk body weight (SBW), but the Bos taurus indicus presents 10% to 8% lower NEm than Bos taurus taurus. We have compared animals with different EBW and SBW but with same equivalent empty body weight/standard reference weight ratio (0.75), as both systems have suggested different mature weights. Both systems predicted similar net energy requirements for gain (NEg) for animals with 1.8 kg of daily gain. However, estimated empty body gain was lower for NASEM estimations when the same metabolizable energy for gain is available. For pregnancy and lactation of beef cows, the NEm and net energy requirements for pregnancy (NEp) of a Zebu cow estimated by BR-CORTE were lower than the values estimated by NASEM. Furthermore, the magnitude of differences between these systems regarding NEp increased as pregnancy days increase. The NASEM and BR-CORTE systems have presented similar values for energy requirement for lactation (0.72 and 0.75 Mcal/kg milk, respectively).

Energy requirements in early life are similar for male and female goat kids.

Little is known about the gender differences in energetic requirements of goats in early life. In this study, we determined the energy requirements for maintenance and gain in intact male, castrated male and female Saanen goat kids using the comparative slaughter technique and provide new data on their body composition and energy efficiency. To determine the energy requirements for maintenance, we studied 21 intact males, 15 castrated males and 18 females (5.0±0.1 kg initial body weight (BW) and 23±5 d of age) using a split-plot design with the following main factors: three genders (intact males, castrated males, and females) and three dry matter intake levels (ad libitum, 75% and 50% of ad libitum intake). A slaughter group included three kids, one for each nutritional plane, of each gender, and all three animals within a group were slaughtered when the ad libitum kid reached 15 kg in BW. Net energy requirements for gain were obtained for 17 intact males, eight castrated males and 15 females (5.1±0.4 kg BW and 23±13 d of age). Animals were fed ad libitum and slaughtered when they reached 5, 10, and 15 kg in BW. A digestion trial was performed with nine kids of each gender to determine digestible energy, metabolizable energy and energy metabolizability of the diet. Our results show no effect of gender on the energy requirements for maintenance and gain, and overall net energy for maintenance was 205.6 kJ/kg0.75 empty body weight gain (EBW) (170.3 kJ/kg0.75 BW) from 5 to 15 kg BW. Metabolizable energy for maintenance was calculated by iteration, assuming heat production equal to metabolizable energy intake at maintenance, and the result was 294.34 kJ/kg0.75 EBW and km of 0.70. As BW increased from 5 to 15 kg for all genders, the net energy required for gain increased from 9.5 to 12.0 kJ/g EBW gain (EWG), and assuming kg = 0.47, metabolizable energy for gain ranged from 20.2 to 25.5 kJ/g EWG. Our results indicate that it is not necessary to formulate diets with different energetic content for intact male, castrated male and female Saanen goat kids weighing from 5 to 15 kg.

Energy, protein and amino acid requirements for maintenance and efficiency of utilization for growth of Atlantic salmon post-smolts determined using increasing ration levels

Ration levels were used to determine the digestible protein (DP) and amino acids as well as digestible (DE) and metabolizable energy (ME) requirements of Atlantic salmon post-smolts for maintenance and the efficiency of utilization for gain above maintenance. The salmon (96 g) were held in seawater at a temperature of 10 °C and were fasted for 28 days or fed incremental ration levels of a fishmeal-based diet for 51 days. The composition of gain was determined by the comparative slaughter technique. The relationships between intake of digestible or metabolizable nutrients or energy and gain of those nutrients or energy were linear ( R 2 ≥ 0.98) between zero intake and maximum voluntary intake. The DE and ME requirements for maintenance were 31.5 and 30.6 kJ kg − 0.8 d − 1 , respectively, and the efficiency of utilization of DE and ME for gain were 0.80 ± 0.01 and 0.82 ± 0.01, respectively. The efficiency of utilization for gain of DP was 0.64 ± 0.01 and that of the sum of digestible amino acids 0.57 ± 0.02. The efficiency of utilization of the individual amino acids for gain varied from 0.45 for tryptophan to 0.65 for histidine. The maintenance requirement for DP was 117.5 mg kg − 0.7 d − 1 and for digestible sum of amino acids 204.0 mg kg − 0.7 d − 1 . The maintenance requirements for the individual amino acids varied from 4.3 mg kg − 0.7 d − 1 for methionine and tryptophan to 20.9 mg kg − 0.7 d − 1 for leucine. The results suggest more emphasis should be directed towards determining the maintenance requirements and the efficiency of utilization for gain above maintenance for the individual amino acids and the sum of amino acids rather than for crude protein.

Energy and protein value of lupin seed as a production ration or as a supplement for sheep fed chaffed wheaten hay

Lupin seed was evaluated as a supplement to cereal hay and as the sole component of a production ration, by measuring energy, nitrogen (N), and carbon balances in 4-6 adult wether sheep. Seven diets of different combinations of lupin seed and chaffed wheaten hay were fed in sequence to 4 sheep. The hay was offered as a restricted ration of 800 g/day with and without 100 g lupin seed/day, and ad libitum with and without 2 levels of lupin seed (100, 400 g/day). In addition, lupin seed alone was offered at near maintenance and ad libitum to 6 sheep. The dry matter (DM) content of the wheaten hay contained 7.7 g N/kg DM and 572 g cell wall organic matter (CWOM), and its gross energy (GE) value was 18.1 MJ/kg DM. The GE was 49% digestible, and its metabolisable energy (ME) value was estimated at 6.4 MJ/kg DM at ad libitum intake levels. Corresponding values for the lupin seed fed alone were 49 g N, 199 g CWOM, 20.1 MJ GE, 86% digestible energy, and 15.7 MJ ME/kg. Ad libitum intakes of wheaten hay were below that required to sustain energy maintenance, but total DM intake was increased substantially with 100 g/day of lupin seed supplement. At higher levels of supplementation some substitution did occur, although the response was variable. Methane production was reduced by increasing the level of lupin seed in the ration, but ME and heat (both expressed in relation to DE) and energy balance (expressed in relation to ME) could each be effectively described by single rectilinear relationships, suggesting that the energy value of lupin seed was similar if used as a production ration or as a supplement. Energy values of lupin seed fed alone compared favourably with published values for other leguminous seeds and some cereal grains. Net availability of ME for gain was estimated to be 61%. Urinary N loss, in terms of apparently digested N or available energy, was very high when lupin seed was fed alone, indicating that protein retention was low compared with legume forages of similar N and cereal grain (e.g. oats). Therefore, although leguminous seeds have rely high levels of protein and obvious potential as energy and N supplements, it may not be valid to presume they are ipso facto important sources of amino acids for ruminants. High energy availability and a low potential for protein deposition would imply a significant diversion of energy into fat with such diets.

Energy exchanges of broilers, selected for fatness and leanness, on diets with and without a repartitioning agent

1. Two experiments were undertaken for 3 or 5 d in respiration chambers, on two experimental lines of broiler chickens (aged 25-38 d) selected for leanness and fatness. Diets were without or with 0.4 mg cimaterol per kg. 2. The lean line with sexes combined (experiment 1), or with females only, had a significantly greater heat production than the fat line. Net availability of metabolisable energy for gain (kg) was 0.54 for the lean birds and and 0.84 for the fat birds. 3. Cimaterol did not have an effect on any of the variables examined.

Energy and protein values of four forages, including a comparison between tropical and temperate species

Artificially dried grass of 2 tropical species (Setaria spacelata and Digitaria decurnbens) from which most of the stem had been removed, and a temperate grass (Loliurn perenne) grown under the same subtropical conditions, were compared for energy and protein value. Data for a temperate clover hay (Trifolium resupinatum) that was tested concurrently are included because they provide useful contrasts. Each was evaluated by measuring energy, nitrogen (N) and carbon balances in 4 adult sheep at 2 levels of intake (ad libitum and near energy maintenance) and during fasting. The 3 grasses had similar leaf content (76-83%) and the clover much less (60%). The tropical forages had similar chemical composition but they contained less crude protein (10%) than the ryegrass (L. perenne) (1 5%) and more cell wall constituents (63-66% v. 58%). The clover had the most crude protein (19%) and the least cell walls (38%); it also was highest in carbohydrates, pectin and heat of combustion. Voluntary intakes of the setaria, pangola (D. decumbens) and ryegrass were similar and 20-30% lower than the intake of clover. Digestibilities of dry matter (DM), organic matter (OM) and energy were similar for the grasses and 8 percentage units lower than for the clover whereas digestibility of crude protein differed between the tropical and temperate species, the latter having digestibilities 12-15 units greater. Digestibility of cell walls did not vary. The metabolisable energy (ME) values of the grasses at maintenance were 8.3-8.5 MJ/kg DM while that of clover was 10.1; at maximum intakes, corresponding ME values were 7.9 and 10.0 MJ/kg DM. Net availability of ME for gain was 0.42 for the tropical grasses and the persian clover and 0.36 for the ryegrass. By contrast, the tropical forages supported higher gains of N relative to N supply than did the temperate forages because urinary N loss was not affected by intake of the tropicals; these differences in N gain were drastically reduced when gain was expressed in relation to ME. These results do not support the contention that forages of tropical species have a lower energy value per kg than temperate forages of similar composition. Indeed, the tropical species tested here appear to have had an ideal balance of energy and protein insofar as efficiency of use of digestible N was close to 100% and their energy values were commensurate with their chemical composition.

PARTITIONING METABOLIZABLE ENERGY UTILIZATION IN RUMINANTS TO INCLUDE A FACTOR FOR ASSIMILATION OF FOOD INTAKE AND ITS APPLICATION FOR EVALUATING ENERGY REQUIREMENTS OF GROWING-FATTENING CATTLE

A mathematical analysis of heat production by growing ruminants was used to assess the physiological importance of assimilation and digestion of dry matter intake. Energy retention (ER) was calculated according to National Academy of Sciences-National Research Council (NAS-NRC) (1984) for 300- and 600-kg cattle fed hay or corn silage with approximately 0, 25, 50 and 75% oat or corn grain. Protein synthesis was calculated for each ER using NAS-NRC (1984) standards for medium- and large-frame bulls, steers and heifers. Fat retention was then estimated by removing the caloric value of protein from ER and dividing the result by the caloric value of fat. Heat production (Y, MJ), obtained as the difference between metabolizable energy (ME) intake and energy retention, was related to the animal's metabolic weight (X1, kg), to the protein (X2, kg) and fat (X3, kg deposited and to the dry matter intake (X4, kg):[Formula: see text]This equation explained 99.9% of the variation of individual heat productions predicted by the California net energy system (NAS-NRC 1984). Heat production per kilogram dry matter intake (3.85 MJ) ranged from 38% at maintenance to 48% above maintenance of the total heat produced, which is similar to values reported in the literature from physiological studies. Metabolizable energy efficiency for fasting, gain of protein and gain of fat was respectively 102, 63 and 64%, whatever feed-stuffs were used. The proposed energy system can be summarized and used as follows: ME requirement = ME for fasting + ME for gain of fat + ME for gain of protein + ME for dry matter intake. In this form, ordinary ME values for feedstuffs are used. Key words: Ruminant, growth, protein fat efficiency, system, intake energy

A comparison of the energy and nitrogen metabolism of fed ducklings and chickens.

1. Energy measurements were made over 4 d on groups of three ducklings (aged from 5 to 22 d), and three broiler chickens (aged from 11 to 32 d) offered high- or low-energy diets. 2. Food, metabolisable energy (ME) and water intakes were significantly higher for ducklings than for chickens. The ratio of water:food was 4-2:1 and 2-3:1 for ducklings and chickens, respectively. The food conversion ratio differed between diets but not species. Performance was generally better for both species on the high-energy diet. 3. Heat production, energy, fat and protein retentions were higher for ducklings than chickens, and ducklings retained 0.44 of their energy as fat compared with 0.37 for chickens. Overall the ratio of protein (g) to fat (g) retention was 2.2:1 and 2.8:1 for ducklings and chickens respectively. 4. For ducklings, metabolisability of the high-energy diet declined from 0.774 to 0.747, and to a lesser extent of the low-energy diet, as they aged. There was no such decline for chickens. Net efficiency of utilisation of ME for gain was 0.64 for ducklings compared with 0.50 for chickens. 5. Fractional retention of dietary nitrogen (N) was 0.62 for ducklings and 0.55 for chickens. Gaseous ammonia-N was 4.5 and 2.2%, respectively, of N retained. 6. In a second experiment groups of ducklings only, were offered high- and low-protein diets from 12 to 22 d of age. Comparisons among four diets showed that food and energy intake was lower on the low-protein diet than on the other three. Energy retention on the high-energy diet was greater (P less than 0.05) than on the other three diets. 7. It was concluded that a high-energy diet is important for ducklings and chickens for maximum biological performance during the first 4 weeks of life.