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 metabolism of growing broiler chickens kept in groups in relation to the environmental temperature. 3. Moderated model description of the efficiency of the utilization of variable energy for body energy retention

An attempt is made on the basis of extensive studies on the energy metabolism of growing broilers to describe as a model the efficiency of the energetic utilization of the feed. The following parameters are components of the model: metabolizable energy, energy maintenance requirement, thermoneutral temperature, thermoregulatory heat production, heat production from the partial utilization of metabolizable energy for body energy retention, heat production (total), energy retention, utilization of metabolizable energy (total), live weight, environmental temperature. At environmental temperatures of 35, 30, 25, 20 and 15 degrees C resp. the model statement for the total utilization of metabolizable energy amounts to 32.4, 39.4, 39.6, 37.3 and 36.2% resp.     

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.     

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.     

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.     

The influence of environmental temperature, age and sex on the digestibility of amino acids in growing broiler chickens

The ability of the broiler chicken to metabolise energy and to digest and absorb amino acids increased from 30 to 50 d of age. Although sex had no major effect on metabolisable energy or amino acid digestibilities at these ages, the influence of environmental temperature on amino acid digestibilities appeared to be sex-related, there being decreased digestibilities of most amino acids at higher temperatures in female but not male birds.     

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.     

Modelling the static and dynamic responses of total heat production of broiler chickens to step changes in air temperature and light intensity

1. The objective of this work was to explore the possibilities of modelling the static and dynamic responses of total heat production of broiler chickens to step changes in temperature and light intensity (light-dark alterations) using compact dynamic model structures. 2. Seventy-seven experiments were performed in an open-circuit respiration chamber to measure the dynamic response of heat production to step variations in temperature and light (on/off). The animal responses were modelled using transfer function model structures. 3. It was demonstrated that the complex process of the dynamic response of heat production of broiler chickens to step changes in air temperature and light-dark alterations can be modelled assuming 1st order dynamics. The coefficient of determination between measured and simulated heat production was on average 0.83 for responses to air temperature and 0.93 for responses to light-dark alterations.     

High carbon dioxide tension (PCO2) and the incidence of cardiac arrhythmias in rapidly growing broiler chickens.

The purpose of this investigation was to determine whether two-week-old rapidly growing broiler chickens with high metabolic activity have an increased risk of the development of heart failure three to five weeks later. The incidence of cardiac arrhythmias was assessed in broiler chickens with either a relatively high carbon dioxide tension (PCO2) or a low PCO2 in their venous blood. Their electrocardiograms (ECGS) were measured when the birds were between five and seven weeks old by means of a biotransplant which allowed them to move freely. Premature ventricular beats were observed in all the birds, but the largest numbers were observed in birds that had had a high PCO2 when they were two weeks old.     

Bioefficacy of L-lysine.H2SO4 relative to L-lysine.HCl in broiler chickens, estimated by slope-ratio model

1. A broiler experiment was conducted to assess the effectiveness of L-lysine.H2SO4 relative to L-lysine.HCl. Four concentrations of L-lysine.H2SO4 and L-lysine.HCl (0.9, 1.8, 2.7 and 3.6 g/kg diet) were each added to a basal diet that met the nutrient requirements of broilers except for lysine. 2. Birds responded significantly to the supplements in daily gain, feed intake, feed conversion efficiency, nitrogen retention and plasma urea nitrogen during each period (d 4 to 21, d 22 to 42 and d 4 to 42). 3. Regression analysis showed that the bioefficacy of L-lysine.H2SO4 relative to L-lysine.HCl was 0.93, 0.86 and 0.95 for daily gain, feed conversion efficiency and nitrogen retention, respectively, during the starter period (d 4 to 21), and was 1.01, 1.36 and 1.06, respectively, during the grower period (d 22 to 42). It was 0.99, 1.07 and 1.03, respectively, for the overall period (d 4 to 42), when the bioefficacy of L-lysine.HCl was set at 1.0. 4. The bioefficacy of L-lysine.H2SO4 differed with different response criteria. The average bioavailability of L-lysine.H2SO4 relative to L-lysine.HCl was 1.03 on an equimolar basis in the present study. In conclusion, L-lysine.H2SO4 and L-lysine.HCl are equally efficacious to broiler chickens.     

Overshoot and high equilibrium in body temperature responses of rats to ambient heat: relation to thermoregulatory ability and improvement in estimation of survival time in a hot environment.

Physiological significance of body temperature responses to ambient heat (BTRAH) with high overshoot or a high equilibrium phase was studied in relation to thermoregulatory ability. Subsequently, an attempt was made to predict survival time (ST) by measuring the period required to attain a colonic temperature (Tco) of 42.0 degrees C (t42.0), whereas ST hitherto having been calculated on the basis of a period until Tco attains 42.5 degrees C (t42.5). Tco of rat was monitored continuously with a Cu-Co thermocouple during exposure to an ambient temperature (Ta) of 42.5 degrees C. The lower the overshoot temperature (Tos) or the equilibrium temperature (Teq), the longer the rats survived in a hot environment. The present findings further suggest that these two types of BTRAH are immature variations of the typical triphasic BTRAH which is characteristic of heat resistant individuals. A new regression line of ST (Y) as a function of the t42.0 (X) was obtained for most rats as follows: Y = 0.963X + 43.85 (male); and Y = 0.973X + 39.10 (female). This equation enabled to calculate ST without thermal death. However, the former approach based on t42.5 must be applied yet in small number of rats which showed the irregular BTRAHs with Tos or Teq higher than 42.0 degrees C. Delayed influence on survival and fecundity at a Ta of 24 degrees C were not found during one year following this hyperthermia up to 42.5 degrees C.     

Determination of kinetic parameters of protein metabolism in growing rats in conjunction with measurement of energy metabolism. 1. Determination of kinetic parameters of protein metabolism in relation to body weight and protein content of the feed

The digestibility, the N balance, the rate of protein synthesis and other parameters, characterising the protein metabolism in dependence on live weight, protein- and energy supply are estimated on Wistar rats (4-5 animals/group). These experiments were done in 5 alternating consecutive growth and energy maintenance periods at 4 different levels of protein (6, 10, 17, 26% CP) during the live weight period of 70 to 230 g. The rate of protein synthesis was calculated from the course of renale 15N excretion by means of the end product method after giving a single dose of a mixture of 17 15N labelled amino acids. N deposition, rate of protein synthesis and flux rate increased with the protein level of the ration. During maintenance these data were much lower, but showed the same dependence on the protein level. The absolute protein synthesis (g/d) increased up to the live weight of 130... 180 g and decreased afterwards according to the age. The reutilization rate varied between 44 and 87% and decreased with increasing dietary protein level by 27% and during proceeding age by 8 ... 12%. In contrast to the absolute metabolism rates (g/d) the fractional rates (%/d) clearly decreased with the age of the animals. The stimulation of these rates by the dietary protein level resembled that for the absolute rates of synthesis. The protein deposition showed the typical course of a growing curve according to the N intake and the protein synthesis showed practically the same course but on a higher level. The break down remained constantly (approximately 140 mg N/d) up to an N intake of about 360 mg and afterwards it increased too.     

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.     

Variation in seed protein digestion of different pea (Pisum sativum L.) genotypes by cecectomized broiler chickens: 2. Relation between in vivo protein digestibility and pea seed characteristics, and identification of resistant pea polypeptides

Eight pea genotypes characterized for their major protein fractions were used to investigate the effect of seed protein composition variability on protein digestibility in poultry. These genotypes of various pea types, were also variable in other seed components. They showed variations in their carbohydrate (insoluble fibre compounds, soluble fibre, soluble carbohydrates) and trypsin inhibitor (TI) contents. To exclude the effect of tannins and of particle size, the seeds were dehulled and micro-ground. They were incorporated as the only protein source in isoproteinaceous diets with similar metabolisable energy content and fed to cecectomized chickens. The average amino acid digestibility (apparent and true) and endogenous amino acid excretion were related with pea diet characteristics (protein composition, carbohydrate composition and TI activity). This allowed to precise which of the diet characteristics affect protein digestibility and endogenous excretion. Average apparent digestibility of amino acids was negatively correlated with insoluble fibre components (R = − 0.71 to − 0.72; p < 0.05) and TI activity (R = − 0.93; p < 0.001). Average endogenous losses of amino acids were positively correlated with soluble carbohydrate content (R = 0.77; p < 0.05) and TI activity (R = 0.84; p < 0.01). Average true digestibility of amino acids was positively correlated with the PA2 albumin level (R = 0.71; p < 0.05), and negatively with the legumin level (R = − 0.72; p < 0.05). Resistant peptides extracted from chicken excreta were analysed through electrophoresis and identified by immunodetection. Intensity of detected resistant peptides showed variation among genotypes. However, for the 8 pea genotypes, the pea proteins, which persisted at the end of the digestive tract, were mainly albumin PA1b and lectin. Other minor peptides were also detected: vicilin, albumin PA2 and legumin peptides which migrated at the same level as β-subunits.