Effect of protein quality on energy requirements for maintenance in growing rats

Forty 3-week old male Wistar rats (initial weight 45-50 g) were used. After weaning they were fed ad libitum for four weeks (I to IV) on 6 isocaloric and isonitrogenous semisynthetic diets based on soya bean meal (diet SBM) or on ground lupin seed (diet LS) alone or autoclaved (A) or not at 120 degrees C and supplemented with DL-methionine (diets ALSm or LSm, respectively) or with DL-methionine + L-lysine (diets ALSm + l or LSm + l). The diets differ in their protein quality and were formulated in order to provide the adequate experimental conditions to determine the biological value (10% crude protein). Then over the fifth and sixth weeks (V and VI) the rats were fed on the same diets but restricted to 60% of the voluntary feed intake. In a parallel experiment, a group of eight rats previously fed ad libitum on diet SBM for four weeks was fasted for 72 h and then fed on the same diet at a level of intake slightly below maintenance. After a 24 h adaptation period, irrespective of the level of intake and type of diet, a series of 24 h gas-exchanges measurements were carried out in open-circuit respiration chambers. Measurements of energy balance were used to calculate ME for maintenance (MEm) and the efficiency of utilization of ME, using a linear regression of energy retention (RE) on ME. The estimates for MEm derived from energy balances of rats fed above maintenance ranged from 564 to 621 kJ/kgW0.75 per d. No significant differences between diets were observed. From pooled data MEm was found to be 599 kJ/kgW0.75 per d, a value not significantly different from that calculated from measurements at fasting and below maintenance levels (598 kJ/kgW0.75 per d). The efficiency of utilization of ME for maintenance was 81.1% and the efficiencies of utilization of ME for RE ranged from 36.6 to 59.9%. It is concluded that no variations in MEm requirements in growing rats attributable to variations in dietary protein quality have been found. Nevertheless, these results should be taken with caution because of limitations inherent of statistical modelling approaches of partitioning ME.     

Energy metabolism of growing rats in relation to the environmental temperature

8 experiments were carried out with 9 albino rats each (Wistar line, bred at the institute) in the live weight range between 70 and 200 g and at environmental temperatures (ET) of 34, 32, 30, 28, 26, 24, 22 and 20 degrees C. In the course of each individual experiment the rats were alternatively fed for maintenance and weight gain (semi ad libitum) with feed mixtures containing 10, 25 and 40% crude protein (3 animals/variant). Energy metabolism was measured according to the method of indirect calorimetry over a total of 780 metabolism periods. In the temperature range studied there was no compensation between thermoregulatory heat and heat from other processes of the metabolism. The partial utilization of metabolizable energy for energy retention in the body was independent of ET and ranged between 73 and 80% for the 7 experiments with ET between 32 and 20 degrees C. Energy utilization depended on the protein content of the feed and decreased from 81 to 79 or 73 resp. when the protein content increased from 10 to 25% or to 40% resp. Energy requirement for protein retention varied between 1.61 and 2.09 kJ metabolizable energy/kJ and was independent of ET. Energy maintenance requirement (measured at 28, 30 and 32 degrees C) increased with the growing protein content from 415 to 439 and 447 kJ/kg LW0.75.d resp. (regression analysis) and from 411 to 420 and 432 kJ/kg LW0.75.d (measuring at maintenance level). The relative weight gain with the increased protein content of the feed largely corresponds to the expected values according to the efficiency of ATP synthesis in the oxidative degradation of nutrients. The relationship between heat production and ET is parabolic. In the live weight range studied the average thermoneutral temperature (TNT) was 32 degrees C. It decreased during the course of development from 34 to 30 degrees C. TNT decreased with the growing protein content of the feed. Thermoregulatory heat production depended on both environmental temperature and the stage of development. Its average value in the development range studied decreased with an increase of the environmental temperature by 2 K each, starting from 20 degrees C and rising to 32 degrees C, in the following linear sequence: 23.3, 21.0, 16.8, 12.5, 8.3, 4.0 and 0.3 kJ/kg LW0.75.d.K.     

Energy metabolism of growing broilers in relation to the environmental temperature

7 experiments with 6 chickens each (origin Tetra B) in the live weight range between greater than 100 and less than 300 g and up to 1800 g were carried out at environmental temperatures (ET) of 35, 30, 25 (2 experiments) 20 (2 experiments) and 15 degrees C. In the course of each experiment the chickens alternatively received feed mixtures containing 20 and 40% crude protein (3 animals/variant) for maintenance and weight gain (semi ad libitum). Energy metabolism was measured according to indirect calorimetry over a total of 645 metabolism periods. In the temperature range studied there was no compensation between thermoregulatory heat and heat from other metabolic processes. The partial utilization of metabolizable energy for energy retention in the body was independent of ET and remained in the limits between 71 and 73%. Energy utilization was dependent on the protein content of the feed. It decreased from 75 to 69% with the increase of the protein content from 20 to 40%. Energy requirement for protein retention varied between 1.67 and 1.89 kJ metabolizable energy/kJ and was independent of ET. Energy requirement (metabolizable energy) for the maintenance of the energy balance was independent of the protein content of the feed. It increased from 433 kJ/kg LW0.75.d at 35 degrees C to 693 kJ/kg LW0.75.d at 15 degrees C ET. The relationship between heat production and ET is parabolic. The thermoneutral temperature decreased from 35 to 25 degrees C in the course of development. In the live weight range of 300-500 g thermoregulatory heat production had its maximum with 19 kJ/kg LW0.75.d.K and decreased in the further development to 10-13 kJ/kg LW0.75.d.K.     

雉鸡育成后期能量代谢参数及其需要量的研究

采用梯度饲养试验、代谢试验和比较屠宰试验 ,结合营养化验和统计分析 ,对 9～ 14周龄育成后期雉鸡的能量代谢参数及能量需要量进行了全面测定研究。结果表明 ,雉鸡育成后期维持代谢能需要量为每千克代谢体重每天 4 6 2 0 0kJ ;雉鸡育成后期生长代谢能的利用效率 (Kpf)为 4 2 18% ,每克增重需要代谢能2 2 86kJ;雉鸡育成后期随着采食量的增加 ,其体蛋白能沉积量、体脂肪能沉积量和体脂肪沉积能占总净能的比例均相应提高 ,但体蛋白沉积能占总净能的比例随着采食量的增加而逐渐降低     

Effects of factors of nutrition and husbandry on the heat production of rats and broilers. 1. Heat production of growing broiler chicks kept in groups depending on the environmental temperature

In 2 experiments with young broiler chickens, origin Tetra B, heat production was measured in dependence on ambient temperature indirectly and with the gas exchange both over 24 h and in 20-minute periods beginning on their 5th day of live. The chickens, divided into 2 X 2 groups according to sex, were constantly kept in a climatic chamber changed in to a respiration chamber during the 8- or 11-week-long experiments. The maximum variation of the temperature was between 5 and 35 degrees C. In the periods of 24-h measurements over 4 days each, the ambient temperature was changed from day to day in steps of 5 degrees C. Heat production was influenced by the age of the chickens, energy intake and ambient temperature. The results of the measurements at the same age and the same energy intake and a temperature variation between 5 and 35 degrees C can well be described by polynomes of the 3rd degree up to the 8th week of live. The thermoregulatory conditioned heat production per 1 degree C below the critical temperature decreased with the age of the chickens. In the first few weeks of life it was 20 kJ, in the 6th and 7th weeks of life 10-15 kJ and then decreased to 4-5 kJ/kg life weight 0.75.d. degrees C. Based on the temperature of minimal heat production, the heat production of 16- to 30-day-old chickens increased to 60-80% at an ambient temperature of 5 degrees C; the metabolism of chickens older than 7 weeks was only increased by about 20%. For the first 2 weeks 35 degrees C were ascertained as critical temperature, for the 3rd to 6th weeks 30 degrees C and for the 7th and 8th weeks 25 degrees C.     

Continuous measuring of heat production during the course of the day in fully grown rats at different nutrition levels and different environmental temperatures

The heat production of 4 rats was measured by means of indirect calorimetry over 20 h/d at intervals of 4 min at ambient temperatures of 30, 25, 20 and 15 degrees C and feed intakes of 0, 4, 8 and 12 g/d. When the rats were hungry, their heat production was reduced by between 8 and 44 kJ/kg LW0.75.d. Feed intake increased heat production by between 54 and 102%. In the temperature range between 20 and 30 degrees C the rats required 0.36 kJ or 2.4% resp. of the metabolizable energy for the intake of 1 g feed. At 15 degrees C the corresponding values were 0.48 kJ or 3.2% resp. The activity-conditioned quota of heat production was estimated as 31 +/- 10%. In the temperature range of between 30 and 25 degrees C thermoregulatory heat production amounted to 5 and that in the temperature range between 25 and 15 degrees C to 20 kJ/kg LW0.75.d.K. No compensation of thermoregulatory heat by heat from increase of energy intake could be proved in the temperature range between 15 and 30 degrees C.     

Consequences of nutritional and husbandry factors on the heat production of rats and broilers. 2. Effect of environmental temperature on the heat production of fully grown broilers and rats

In an experiment with broilers (origin Tetra B) and with rats (albino, Wistar line) with 2 animals each, heat production was ascertained by measuring CO2 production and O2 consumption over 20 minutes after their feeding 18 h and 1 h before the beginning of measuring at ambient temperatures of 30, 25, 20, 15 and 10 degrees C. Every variant was followed through over 6 h/d in 12 measuring sections. The feed amount/ánimal and day was adapted to energy maintenance requirement. At the beginning of the experiments the broilers and rats were 14 and 21 weeks old resp. and weighed 2.2 kg and 220 g resp. The variation of the ambient temperature did not influence the heat production of the broilers. In contrast to this, the time of feeding in relation to the beginning of measuring had a distinct effect on heat production. Whereas a heat production of 342 +/- 34 kJ/kg LW0.75.d was ascertained in the postabsorptive state 18 h after the last feed intake, it increased by 11% to 393 +/- 32 kJ/kg LW0.75.d when measuring began 1 h after feeding. The very act of feed intake increased heat production by 75%. Rats showed a distinct increase of heat production caused by a decreasing ambient temperature. In the temperature range of 30-25 degrees C the increase was shallower than in the range of 25-10 degrees C. Per 1 degrees C below 25 degrees C heat production increased by 30 kJ/kg LW0.75.d. The increase was independent of the metabolism level, which was influenced by the feeding variants. The results are discussed in connection with Rubner's theory of heat compensation.     

Modelling energy utilisation in broiler breeder hens

1. The objective of this study was to determine a metabolisable energy (ME) requirement model for broiler breeder hens. The influence of temperature on ME requirements for maintenance was determined in experiments conducted in three environmental rooms with temperatures kept constant at 13, 21 and 30 degrees C using a comparative slaughter technique. The energy requirements for weight gain were determined based upon body energy content and efficiency of energy utilisation for weight gain. The energy requirements for egg production were determined on the basis of egg energy content and efficiency of energy deposition in the eggs. 2. The following model was developed using these results: ME = kgW0.75(806.53-26.45T + 0.50T2) + 31.90G + 10.04EM, where kgW0.75 is body weight (kg) raised to the power 0.75, T is temperature ( degrees C), G is weight gain (g) and EM is egg mass (g). 3. A feeding trial was conducted using 400 Hubbard Hi-Yield broiler breeder hens and 40 Peterson males from 31 to 46 weeks of age in order to compare use of the model with a recommended feeding programme for this strain of bird. The application of the model in breeder hens provided good productive and reproductive performance and better results in feed and energy conversion than in hens fed according to strain recommendation. In conclusion, the model evaluated predicted an ME intake which matched breeder hens' requirements.     

Energy metabolism of growing broiler chickens kept in groups in relation to the environmental temperature. 1. Feed intake, heat production and energy utilization]

In 5 experiments with young broiler chickens kept in groups at environmental temperatures (ET) of 35, 30, 25, 20 and 15 degrees C feed intake, live weight development and heat production were ascertained between their 5th and 57th days of life. Feed intake and live weight were ascertained separately according to sex. With live weight being the same, feed intake increased with decreasing ET. There was no maximum feed intake up to the 57th day of life at between 20 and 25 degrees C. At the end of their 57th day of life the male and the female chickens had achieved the following live weights (in the sequence of decreasing ET 35-15 degrees C): 1342; 2014; 2829; 2946; 2374 and 1367; 1900; 2512; 2496 and 2200 g/animal resp. The highest live weight gain of the chickens was achieved at between 25 and 20 degrees C with 60-70 g/d for male and with 50-60 g/d for female animals. Heat production (HP) increased progressively with age. The highest HP was registered at 20 degrees C ET.     

Energy and nitrogen metabolism of diseased chickens: interaction of Ascaridia galli infestation and vitamin A status.

1. Effects of Ascaridia galli infection on the energy and nitrogen (N) metabolism were studied on groups of 5 cross-bred cockerels aged about 5 weeks and given a diet deficient or adequate in vitamin A at two levels of feeding in respiration chambers. 2. Metabolisability of dietary energy was 67% and N retention 33% in infected chickens compared with 71 and 41% respectively, in uninfected chickens. 3. Maintenance energy requirement of vitamin A-deficient birds was 882 kJ/kgW d compared with 998 kJ/kgW d for normal birds. N balance of the deficient chickens was also less when compared at the same energy balance. Infection did not affect maintenance energy requirement nor N balance. 4. Starvation heat production of infected chickens (619 kJ/kgW d) was higher than that of uninfected controls (586 kJ/kgW d). When infection treatments were combined, vitamin A-adequate chickens had a higher heat production (615 kJ/kg d) than the vitamin A-deficient (580 kJ/kgW d). Endogenous N excretion (mg/gW) was less in vitamin A-deficient than in adequate, starved birds. 5. Deficient chickens had undetectable liver reserves of vitamin A and only very low plasma concentrations. There was a difference in the length of larvae (17 d after infection) associated with vitamin A status, and with level of feeding.     

Nutrient dependence of energy preservation requirements in rats. 2. Effect of the protein level of feed and the environmental temperature on the energy preservation requirement and heat production in fully-grown rats

The influence of protein in exchange for carbohydrates on the energy maintenance requirement was studied with nearly fully-grown rats at ambient temperatures between 33 and 21 degrees C. The levels of the crude protein content were 10, 25, 40 and 70%. At an ambient temperature of 33 and 30 degrees C energy maintenance requirement increased with the growing protein content in the feed. At a temperature of 30 degrees C the following values of energy maintenance requirement were measured in the sequence of the protein levels mentioned: 330 +/- 11, 347 +/- 18, 360 +/- 15 and 399 +/- 15 kJ metabolizable energy/kg live weight 0.75 X d. The occurring changes largely coincide with the expected values calculated from the efficiency of the ATP synthesis in the oxidative catabolization of protein and carbohydrates. At ambient temperatures of less than 30 degrees C, thermogenous effects after the exchange of protein versus carbohydrates could only be observed partly or not. 30 degrees C in feeding on the maintenance level and 33 degrees C in the state of hunger are estimated as the lower critical temperatures. Below the critical temperatures down to 24 degrees C heat production increased less per 1 degree C temperature decrease both in hungry and fed rats than in the temperature range between 24 and 21 degrees C. By the decrease of the ambient temperature from 24 to 21 degrees C the heat production of the hungry or fed rats increased by 39 or 33 kJ/degrees C X kg live weight 0.75 X d.     

Nutrient dependence of energy conservation requirements in rats. 4. The influence of protein levels of food on energy conservation requirements of rats during growth and after conclusion of the intensive growth phase

Albino rats bred in the institute (Wistar line) divided into 3 groups of 9 animals each received, beginning at the age of 4 weeks, feed mixtures with 10, 40 and 70% protein in the rations over a period of 24 weeks divided into 14 subperiods of study. The feed mixture changed cyclically for the groups of animals after each sub-period. Every period was divided into a growth period (8 days) with the rats kept in metabolism cages and a period of feeding on maintenance level (4 days) with the rats kept in respiration chambers. In both periods the temperature was kept constant at 30 degrees C. On 3 days of feeding on the maintenance level the metabolism parameters of energy, C and N metabolism were measured and energy maintenance requirement was ascertained. Both the energy maintenance requirement of the growing rats (up to 200 g live weight) and that of the nearly fully grown and fully grown rats resp. (greater than 200 g live weight) significantly depended on the nutrient composition of the feed mixtures supplied. It increased with the increasing protein and simultaneously decreasing carbohydrate quotas in the feed. On an average of the studies the rats had, in the sequence of 10, 40 and 70% protein content, an energy maintenance requirement of 383 +/- 31 (n = 105), 415 +/- 31 (n = 106) and 459 +/- 36 kJ metabolizable energy/kg LW0.75.d (n = 102). Energy maintenance requirement behaved relatively like 100:108:120. Based on the fact that energy maintenance requirement may be considered the requirement of ATP, relative expectancy values for energy maintenance requirement can be calculated with the energetic efficiency of the ATP synthesis (kJ metabolizable energy/Mol ATP gain) in nutrient catabolism from the relation of the experimentally ascertained nutrient metabolism at a variant supply of protein of 100:110:118. The hypothesis that the efficiency of ATP synthesis in the catabolism of the main nutrients supplying energy can be considered a relative measure of the dependence of the energy maintenance requirement on nutrient composition has been confirmed in this experiment. Different findings in earlier experiments raise the question if those findings were influenced by adaptation effects. An experimental solution of this question is considered important.     

Energy metabolism of groups of broiler breeders in open-circuit respiration chambers

Energy metabolism of broiler breeders housed in groups was measured in large open-circuit respiration chambers. The design, function and calibration of the chambers are described. Each of the three chambers has a capacity for 24 pullets or adult layers, or 16 adult broiler breeders. Control of ventilation rate is by calibrated choked-flow nozzles. Before experiments were started the system was assessed by CO2 infusion and recovery and ethanol combustion studies. Percentage CO2 recoveries were greater than 98 of infused and the mean (+/- SD) quotient of CO2 produced to O2 consumed from the combusion of ethanol was 0.67 (+/- 0.02). Forty-eight broiler breeder hens in lay were placed in the respiration chambers (16 per chamber) and fed at different rates from around maintenance to about twice this value. The energy required for maintenance (MEm) was 365 kJ/kgW0.75 d and the efficiency of utilisation of metabolisable energy (ME) for production (kp) was 0.70. Starvation heat production was about 350 kJ/kgW0.75 d and was shown to affect the derived values of the energetic parameters when included in the relationship between retained energy and metabolisable energy intake. Published results were recalculated and found to support this.     

肉鸭不同季节、不同月份代谢能需要量及析因模型比较研究

研究结合生产实践,采用大群生产试验方法,对标准化饲养的8 540栋鸭舍,健康同源樱桃谷商品鸭苗3 094.4万只,按统一饲养方式和管理程序进行生产试验,结果表明,樱桃谷肉鸭地面平养饲养模式下,春、夏、秋、冬四个季节的代谢能维持需要为每千克代谢体重455.1、305.5、342.8、541.7 kJ,每增重1 kg需要代谢能为16.97、19.86、19.65、15.95 MJ。各季节之间代谢能维持需要量为冬季>春季>秋季>夏季;代谢能增重需要量为夏季>秋季>春季>冬季。按照月份统计,樱桃谷肉鸭代谢能维持需要8月份最低,5月份最高;增重需要8月份最高,5月份最低。研究结果表明,樱桃谷肉鸭地面饲养模式下,夏季代谢能维持需要最低,冬季最高;冬季代谢能增重需要最低,夏季最高。不同季节代谢能需要量可以用以下析因模型预测:春季:MER=16.97BGW+0.455W0.75;夏季:MER=19.86BGW+0.305W0.75;秋季:MER=19.65BGW+0.343W0.75;冬季:MER=15.95BGW+0.542W0.75。式中:MER为肉鸭代谢能需要量(MJ/d);BGW为活体增重(kg);W0.75为代谢体重(kg)。     

Studies on nitrogen retention in growing pigs

Nitrogen retention (RN) was measured in 60 barrows of Danish Landrace and a total of 470 balance periods was carried out during the growth period from 20 to 85 kg live weight. In the first serie (Expt A) six different feed compounds of high biological value (HBV) were fed to 48 barrows, while in the second serie (Expt B) 12 barrows were measured on feed compounds of HBV or low biological value (LBV). Three different levels of gross energy were used in Expt B. Individual differences of 10-20% in the pigs capability for nitrogen retention were observed. Nitrogen retention increased from 12 to 21 g N/d on the HBV-compounds and was not influenced by increasing nitrogen or energy intake. Nitrogen retention was curvilinear in relation to metabolic live weight (kg0.75) in both series. A parabolic function on kg0.75 gave the best fit to the data with the following regression equations: Expt A + B: RN, g/d = 1.48 LW, kg0.75 - 0.027 LW, kg1.50 (HBV) Maximum = 20.5 g RN/d at 84 kg LW Expt B: RN, g/d = 1.03 LW, kg0.75 - 0.013 LW, kg1.50 (LBV) Maximum = 20.4 g RN/d at 133 kg LW     

The energy metabolism of swine at a feed level of "live weight equilibrium"

10 castrated pigs each of a live weight (LW) of 35 kg and 115 kg were fed over 28 and 40 days resp. in a way that a live weight equilibrium was achieved. The pigs were kept individually and at a low mobility on perforated floors of zinc-plated sheet iron at an air temperature of 19 degrees C. The weighing 35 kg received 668 kJ ME/kg LW 0.75 per day and one half of the animals weighing 115 kg 635 kJ ME/kg LW 0.75 in a diet consisting of barley and bran. The other half of the animals weighing 115 kg received 514 kJ ME/kg LW 0.75 per day in a ration consisting barley, bran and dried skim milk. The crude protein content of the rations was 12.6 and 17.1% resp. of the DM, the crude fibre content amounted to 8-10% of the DM. Energy excretion in faeces and urine was calorimetrically measured. Up to the end of the experiment LW and the weight of the empty body (without ingesta) remained unchanged. For the measuring of energy retention, 4-5 zero animals each were analysed before the experiments. The pigs weighing 35 kg showed a daily loss of 39 g fat in the course of the 40-day experiment. The calculation of the energy balance showed that an intake of 790 kJ ME/kg LW 0.75 was necessary. This maintenance requirement, rather high in comparison with values from literature, can be explained with the emission of body heat on sheet iron floors and a crude fibre content of 9% in the rations. The pigs of the two groups of 115 kg LW were at an energy equilibrium at both nutrition levels. The lower maintenance requirement of the group fed with dried skim milk cannot exclusively be explained by the higher energetic utilization of the milk protein in the ration. The reason should be the more advanced age of the animals of the milk group. Although they had nearly the same live weight, their empty bodies contained 41% fat, the pigs of the barley/bran group, however, only 34%, both before and after the experiment.     

Interaction between the temperature of the surroundings, performance and level of feed for growing pigs

Investigations of the performance of growing pigs in the live weight range of 30 to 60 kg kept individually and in groups with ad libitum and rationed feeding were carried out in two air-conditioned rooms. The air temperature in the individual experiments was 20 degrees C, 10 degrees C and 5 degrees C, the relative atmospheric moisture in all experiments was between 70 and 80%. A diminished growth of 24 g per day per degrees C below 20 degrees could be ascertained for pigs kept individually. The diminishing of the growth can be compensated by an increase of the feed intake of 1.3 g per kg live weight, day and degrees C resp. the intake of metabolisable energy of 4 kcal per kg live weight, day and degrees C until the capacity of feed consumption is reached.     

Influence of high ambient temperatures on performance of multiparous lactating sows.

Multiparous Large White sows (n = 63) were used to investigate the effects of five ambient temperatures (18, 22, 25, 27, and 29 degrees C) and two dietary protein contents on their lactation performance. At each temperature treatment, ambient temperature was maintained constant over the 21-d lactation period. Dietary protein content was either 14 or 17% with essential amino acids levels calculated not to be limiting. The animals had ad libitum access to feed between the seventh and the 19th day of lactation. Diet composition did not influence lactation performance. Over the 21-d lactation, feed intake decreased from 5.67 to 3.08 kg/d between 18 and 29 degrees C. Between d 7 and 19, the corresponding values were 7.16 and 3.48 kg/d, respectively. This decrease was curvilinear; an equation to predict voluntary feed intake (VFI) from temperature (T, degrees C) and body weight (BW, kg) is proposed: VFI = -49,052 + 1,213 T - 31.5 T2 + 330 BW - .61 BW2 (residual standard deviation: 1,018). Skin temperature increased regularly with increased ambient temperature (34.6 to 37.4 degrees C between 18 and 29 degrees C), whereas udder temperature reached a plateau at 25 degrees C (38.3 degrees C). The gradient of temperature between skin and rectum was minimal (2 degrees C ) at 27 degrees C and remained constant at 29 degrees C. This constancy coincides with the marked reduction of feed intake. The respiratory rate increased from 26 to 124 breaths/min between 18 and 29 degrees C, and this indicates that the evaporative critical temperature was below 22 degrees C. The BW loss increased from 23 to 35 kg between 18 and 29 degrees C, but its estimated chemical composition remained constant. Pig growth rate was almost constant between 18 and 25 degrees C (241 g/d) and was reduced above 25 degrees C (212 and 189 g/d at 27 and 29 degrees C, respectively). In conclusion, temperatures above 25 degrees C seem to be critical for lactating sows in order to maintain their performance.     

Methodologic studies on protein metabolism and bioenergetics of protein deposition in growing animals. 4. Energy metabolism in chickens in connection with measurement of parameters of protein metabolism

In connection with the measuring of parameters of the protein metabolism in parallel experiments, the energy metabolism of 6 chickens (origin Tetra B) in the live weight range between approximately 100 and 1,800 g was determined under conditions of restricted energy supply. 3 animals each received a feed mixture containing 20% (animal group 1) and 38% (animal group 2) crude protein. The amount of feed was daily increased by 1.5 g DM. The digestibility of energy and nitrogen was independent of the age. 66.3 +/- 3.3% and 64.0 +/- 5.0% resp. of the metabolisable energy were utilised for protein and fat retention. The energy maintenance requirement, determined at a live weight of 2,000 g, was independent of protein supply and averaged in the two animal groups 434 +/- 40 kJ metabolisable energy/kg live weight 0.75 . d. The result of multiple regression was, for the growth period investigated, an energy maintenance requirement of 403 +/- 32 kJ metabolisable energy/kg live weight 0.75 . d. 1.77 and 1.38 J metabolisable energy resp. were required for 1 J protein or fat retention. The energy requirement for protein retention was independent of the degree of protein supply. The results from the measuring of energy metabolism are discussed in connection with the kinetic parameters of protein metabolism ascertained in parallel experiments.     

Dependence of energy maintenance requirements on nutrients in rats. 3. Effect of the protein levels of food on the energy maintenance requirements of growing rats

In addition to earlier experiments with growing rats on the protein levels 10, 25 and 40% crude protein in the dry matter of the feed (Hoffmann et al., 1982 a), two groups of nine male Wistar rats each received feed mixtures with 6 or 25% crude protein resp. and energy metabolism on the energy maintenance level in an N equilibrium or with a positive N balance resp. were measured on 6 levels of live weight between 65 and 250 g and additionally also at subsequent fasting day. Energy maintenance requirement on average of the 6 periods amounted to 381 and 377 kJ metabolizable energy/kg W 0.75 X d on a low or middle protein level resp. and thus did not show changes at the decrease of N retention to values of about zero even with regard to different ATP formation capacities of the nutrients.