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.     

The energy maintenance requirement of growing pigs of different sexes given normal and high protein diets. 1. Experiments in castrates

Energy retention was measured alternately at 12 barrows, fattening hybrids of line 150 (150 X (L X E], at maintenance level (4 periods) and growth feeding (5 periods) in the live weight range between 32 and 134 kg, 6 animals each received rations with 17 and 45% crude protein resp. during the complete experimental period. The nutrition level did not have a significant influence on the digestibility level of the feed. The experiments carried out at maintenance level showed that the maintenance requirement of metabolizable energy in the experiments with 17% crude protein in the ration was 941, in the experiments with 45% crude protein in the ration 913kJ ME/kg LW0.62 and on average 927 kJ ME/kg LW0.62. Including the experiments with growth feeding one can conclude from a regression analysis, largely in agreement with the measured values, that 955 kJ ME/kg LW0.62 is the energy maintenance requirement. These values of maintenance requirement are by 50% higher than those derived from previous measurings. In contrast to expectations, the increase of protein concentration in the ration did not result in a higher energy maintenance requirement. The utilization of metabolizable energy for retention amounted to 74% for rations with a normal protein content and to 65% for those with a high protein content. The multiply regressive evaluation showed a utilization of metabolizable energy for fat retention of 79% and for protein retention of 53%.     

Joint research on the precise determination of the energy and protein requirements of fattening pigs. 3. The energy requirement of hybrid swine

The energy requirement for hybrid pigs ((large white X land race pig) X line 150) in the live weight range between 35 and 120 kg is derived from 242 measurings of the total metabolism as the sum of energy requirement for maintenance and energy requirement for live weight gain. Energy requirement is estimated by means of the following equation: (Formula: see text). Energy maintenance requirement, energy content per 1 kg live weightgain in dependence of the daily gain and the derived energy requirement for growth and fattening are compared with corresponding results from investigations with pigs of the species large white and land race pig. Essential differences concerning parameters of energy metabolism determining the requirement could not be detected.     

Joint research on the precise determination of the energy and protein requirements of fattening pigs. 2. Energy and nitrogen metabolism of fattening hybrids in the fattening range of 30 to 120 kg

In 3 experiments a total of 242 total metabolism experiments with ad libitum feeding (experiment 1), 75% (experiment 2) and 62% (experiment 3) of the energy level of the 1st experiment and approximately equal protein and amino acid doses in experiments 1-3 were carried out with 8 castrated male fattening hybrids each (large white X land race pig) X line 150) in the live weight range between 30 and 120 kg. On average, feed intake over the whole live weight range was 2.24; 1.79 and 1.50 kg/animal and day, the corresponding daily live weight gain was 729, 533 and 396 g. With regard to the digestibility of the energy and the nutrients and the metabolisable energy in % of the gross energy there was no relation to the development of the animals. The intake of metabolisable energy per kg live weight decreased with ad libitum feeding and with the advancing development at the end of the experiment in contrast to the beginning of the experiment to 53%, energy retention to 56%. The utilisation of metabolisable energy for body energy retention, taking account of a maintenance requirement of 450 kJ/kg live weight 0,62 on the average of the 3 experiments was 68.4 +/- 1.9, 70.3 +/- 2.0 and 64.3 +/- 2.6%. Energy retention in experiments 1 to 3 amounted to 8.6, 6.8 and 5.3 MJ at the beginning and to 18.1, 12.2 and 8.0 MJ per animal and day at the end of the experiment. Protein energy retention of the pigs (live weight 40 kg) was 26% of the total energy retention in experiments 1 and 2 and 49% in experiment 3. In experiments 1 and 3 protein retention decreased to 15% of the total energy retention, in experiment 2 protein retention remained constantly at 22% between 60 and 110 kg live weight and then decreased to 18%. Consequently, the N-balances were 23-16 g, 16-20 g and 16-9 g/animal and day. The chemical composition of the carcasses was strongly influenced by the level of nutrition. At the beginning of the experiment the protein content averaged between 49 and 57% and the total fat content between 31 and 38% of the dry matter. At the end of the experiment the carcasses of the animals from experiments 1-3 had crude protein contents of 28, 33 and 42% and total fat contents of 66, 61 and 50% of the dry matter.     

The energy metabolism of growing swine in the liveweight range of 10-50 kg. I. Study design, feed intake and digestibility

Studies of the energy metabolism at maintenance and growth levels after the feeding of rations with a crude protein content of 17-24% and 44-47% resp. were carried out with hybrid pigs of line 150 in the live weight range between 10 and approximately 50 kg. This paper gives information on the methods and the outlay of the experiment and presents results concerning feed intake, live weight development and digestibility. Feed intake increased on average with growing live weight by 30-35 g DM/kg live weight. Feed conversion ranged from 1.2 to 1.8 kg DM/kg live weight gain in the first period and from 2.3 to 3.2 kg DM/kg live weight gain in the last period. The digestibility of the energy in the rations with a crude protein content of between 17 and 24% averaged 80% and that of the rations with a crude protein content of 44-47% averaged 86%. In the course of ontogenetic development the digestibility increased up to about 30 kg LW. The influence of the nutritional level on the level of digestibility was unequal in the experiments. In one experiment a decrease (1% unit) and in two experiments an increase (1-3% units) of the digestibility after the feeding of growth level in contrast to maintenance level could be observed. The change of rations with a varying protein content did not result in an influence on the digestibility level in comparison with the constant feeding of one ration.     

Energy requirement for the maintenance and utilization of energy convertible to protein and fat deposits in piglets

In respiration experiments with 16 piglets the effect of feeding level on energy metabolism was studied with the aim of estimating energy requirement and costs of protein and fat deposition. Four groups of 4 animals each were fed on different levels of digestible protein and metabolisable energy (ME). Group 1 was fed intensively, whereas the piglets of group 2, 3 and 4 received 92, 76 and 55% respectively of the amounts given to group 1. In the group 1-4 mean daily weight gain was 457, 437, 360 and 205 g respectively. As a consequence the rearing period increased from 44 days to 46, 56 and 98 days. The variation in feed intake affected not only significant differences in energy deposition but also changes in gain composition. In the groups 1-4 the average energy deposition was 4.2 MJ, 4.0 MJ, 3.0 MJ and 1.4 MJ per day and protein gain exceeded fat gain in all groups. Estimations of energy requirement for maintenance were carried out by means of multiple regression analysis using different models. As a result a value of 428 MJ ME per kg live weight 0.75 was obtained and the models used have hardly shown any influence. It seems that higher values for maintenance requirement, as formerly published, are due to different conditions of livestock management, such as temperature. For all groups the average efficiency of ME-utilisation for growth was 0.77, ranging from 0.73 to 0.82. The variation can be attributed to the changes in protein and fat formation. The groups with a higher proportion of protein in the accretion utilised metabolisable energy more efficiently than the intensively fed group 1 with the highest proportion of fat, the difference between the groups being in the range from 0.73 to 0.82. The efficiency of ME-utilisation for protein deposition was calculated to be 0.83 and for fat deposition 0.73. As a higher coefficient for fat formation may be expected in the light of the high fat content in the ration, calculations with an assumed coefficient from 0.75 and 0.80 had been carried out, showing that the efficiency of ME-utilisation for protein gain would only decrease to 0.79 and 0.73 respectively. According to these results the statement must be called in question, that the energetic efficiency of protein deposition of about 50 to 55% - as measured in numerous experiments mainly with older pigs - can generally be accepted.     

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.     

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.     

The energy metabolism of growing swine in the body weight range of 10-50 kg. 2. Nitrogen and energy metabolism

Investigations were carried out about nitrogen and energy metabolism feeding rations with 17-24 and 44-47% crude protein content on maintenance and growing level to castrated male hybrid pigs of line 150. In growing periods the N deposition amounted to 10 g/animal.d (15 kg live weight), 18 g/animal.d (30 kg LW) and 21 g/animal.d (greater than 40 kg LW) on lower protein feeding level. In experiments with higher protein feeding level the corresponding results were 17, 22 and 22 g N deposition/animal.d. The partial utilization of metabolizable energy for deposition amounted to 70% for the rations with 17-24% protein content and to 59% for the rations with 44-47% protein content, without correlation to the animals development and the alternation in the protein feeding level. The results of regression analysis about maintenance requirement were 814, 775 and 806 kJ metabolizable energy/kg LW0.62.d in trials feeding rations with 17-24% crude protein content as well as 764, 846 and 818 kJ metabolizable energy/kg LW0,62.d in trials feeding rations with 44-47% crude protein content. 1,5-1,8 MJ metabolizable energy were used per MJ protein energy deposition and 1,3-1,4 MJ per MJ fat energy deposition respectively. The energy deposition per kg live weight gain amounted to values between 9 (10 kg LW) and 18 MJ (60 kg LW).     

The energy maintenance requirement of growing pigs of different sexes given normal and high protein diets. 3. Experiments in boars

Six fattening boars each, hybrids of line 150(150 X (L X E] received rations with 17 and 45% crude protein. In the live weight range of 36 to 167 kg, 5 periods of growth feeding alternated with 4 periods of maintenance feeding. Compared with maintenance level the nutrition level of 2.7 did not have an influence on digestibility. Nitrogen retention was only insignificantly influenced by the level of protein supply. The maintenance requirement of the animals used was by 50% higher than in previous experiments made by our work team. On average it amounted to 1,017 KJ metabolizable energy per kg LW0.62, i.e. to 1,063 for those animals fed with rations containing 17% crude protein and to 986 for those animals receiving 45% crude protein in their rations. The utilization of metabolizable energy for energy retention amounted to 75% for rations with 17% crude protein and to 70% for rations with 45% crude protein. The partial utilization of metabolizable energy for fat retention was ascertained as 90% and for protein retention as 53% by means of multiply regressive assessment.     

Use of limited daily access to food in measuring the heat production associated with food intake in laying hens

1. Two experiments were carried out to determine the heat production associated with food intake in laying hens allowed access to food for one (experiment 2) or two hours (experiment 1) daily. 2. In experiment 1, heat production in the fed state was measured for two successive days after 46 h of food deprivation. The rate of heat production in the fasting state was measured from 47 to 69 h after feeding. 3. In experiment 2, heat production was measured at 4 fixed food intakes: 100, 70, 40 and 0 g/bird. Heat production associated with food intake, eating activity, net availability of ME and maintenance ME requirement was estimated. 4. Heat production after 46 h of food deprivation did not differ from that after 22 h of deprivation. In the hens receiving 100 g of food, heat production reached the pre-feeding level by 20 h after eating; the hens with lower food intakes reached the pre-feeding level more rapidly. It is suggested that the heat production associated with feeding had been eliminated by 22 h after eating. 5. Heat production associated with feeding was 16% of ME intake. Because the total energy cost of eating activity was only 0.8% of ME intake, the heat production associated with food intake in the limited-access hens came mainly from the effects of digestion, absorption and metabolism of the ingesta. 6. The net availability of ME was estimated to be 0.84. The estimated maintenance ME requirement was 569.6 kJ/kgW0.75 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 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.     

Sensorial quality and bone strength of female and male broiler chickens are influenced by weight and growth rate

1. An experiment was conducted with 98 male and 98 female broiler chickens (Ross 308) to study the effect of growth rate, induced by different dietary means, sex and live weight (1500?g and 2000?g) at slaughter on production parameters, bone strength and sensorial characteristics of the breast meat.

2. The birds were divided into four groups and individually fed a standard commercial diet, a high energy diet or low energy diet from d?11 to slaughter at between d 28 and 39. Three groups were fed ad libitum and a further group was fed a restricted amount of the high energy feed. Half of the birds in each group were slaughtered at approximately 1500?g and the other half at 2000?g live weight.

3. The diets resulted in different growth rates. The chickens fed the high energy and the commercial diet had the highest growth rate at both live weights at slaughter. The restricted fed chickens had lower bone strength than the chickens fed the low energy diet.

4. Breast meat from male broilers was juicer, more tender and less hard than breast meat from females. Chickens slaughtered at 2000?g live weight were juicer than those slaughtered at 1500?g. Chickens given the high energy feed ad libitum and restricted had different growth rates, but the sensory parameter related to texture showed no difference.

5. It was concluded that an increased slaughter weight might improve meat quality due to improved juiciness.     

The energy maintenance requirement of growing pigs of different sexes give normal and high protein diets. 2. Experiments in sows

Six animals each out of 12 female fattening hybrids (150 X (L X E] were given rations containing 17 or 45% crude protein resp. 4 periods of growth feeding alternated with 5 periods of maintenance feeding in the live weight range between 33 and 146 kg. The feeding level did not have an influence on the level of digestibility. From the experiments with 17% crude protein in the ration 1004 and from those with 45% crude protein 947, on average 977 kJ metabolizable energy per kg LW0.62 in the maintenance periods and 980 in the growth periods were derived as maintenance requirement of metabolizable energy. These values for maintenance requirement are by 50% higher than those in previous experiments of our work team. In contrast to expectations, energy maintenance requirement did not grow due to the increase of the protein content of the rations. The utilization of metabolizable energy for retention was 73% for rations with a normal protein content and 66% for those with a high protein content. The partial utilization of metabolizable energy for fat retention was ascertained as 83% and as 49% for protein retention by means of multiply regressive evaluation.     

Lysine requirement of fattening sows depending on their performance. 2. Relations between energy consumption and live weight increase

105 growing sows in the live weight range were fed with 7 test rations with graduated energy and amino acid levels. The growth intensity was very much influenced by the daily energy consumption. On the basis of regression analysis the following linear relation between daily weight increase (y in g per kg live weight0,75) and the daily energy consumption (x in energetic feed units for pigs per kg live weight0,75) was calculated: y = -13,79 + 0,7037 x (r = 0,84, sb -0,0295). The interpolation with regard to live weight balance resulted in a maintenance requirement of 19,8 energetic feed units for pigs resp. 70 kcal net energy fat for pigs per kg live weight0,75. The methods of assessment chosen showed an increase of the energy requirement per 100 g additional live weight increase per day of a constant amount, independent of the live weight, of 142 energetic feed units for pigs resp. 497 kcal net energy fat for pigs.     

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.     

Effects of temperature and level of feeding during rearing on carcass and reproductive traits in pigs

A total of 315 crossbred females (gilts) ranging in weight from 14 to 68 kg was split between pole-type and a closed piggery (cold and moderate environments, respectively One third of the pigs in each piggery was fed a growing ration ad libitum, the remaining pigs were restrictively fed 80% of the amount consumed by the first group. Data on ultrasonic backfat probe, estimated market index, and age were taken on the pigs at 90 kg live weight. Results indicated that the effect of environmental temperature was very small on backfat thickness and carcass index, but was significant on age. The pigs fed ad libitum had 10.2% thicker backfat, were 4 points inferior in index, but were 13 days younger at 90 kg (P < 0.01) than those restrictively fed. When the gilts exhibited their first oestrus after 90 kg live weight, half of the pigs restrictively fed were flushed by feeding them ad libitum for one oestrus cycle. All gilts were bred at the second oestrus. The gilts raised in a cold environment were 4 kg lighter, farrowed litters 0.2 larger and 0.5 kg heavier than those raised in the moderate environment. Gilts restrictively fed, then flushed gained 3 kg on flushing and farrowed litters averaging 10.7 pigs, 0.2 and 0.8 pigs larger than those of the gilts fed ad libitum and not flushed respectively. Significant differences between crosses were observed in all the traits studied except gestation length and litter size. There was little effect on the different traits of the initial weight at which the gilts were exposed to the treatment.     

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.     

The energy requirements of Holstein-Friesian heifers during rearing and pregnancy under the tropical conditions of Cuba. 2. Generalization of the results and derivation of the energy requirements

Experimental results of an individual feeding experiment with 48 Holstein-Frisian heifers were generalized with regard to live weight development and energy intake by means of the Janoschek function and the extended e-function resp. The requirement of metabolizable energy was derived from the results of energy intake on dependance on live weight and live weight gain. In comparison with the data of the NRC (1978) a requirement by 10% lower was the result. Due to adding a 10% deficiency supplement at present required under Cuban conditions of production the use of the NRC recommendations (1978) is still justified. Without the addition of the deficiency supplement the results showed good agreement with requirement data of INRA 1978.