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.     

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 broiler chickens kept in groups in relation to the environmental temperature. 2. Heat production, thermoregulatory heat production and thermoneutral temperature (short term measurement)]

In 5 experiments the weekly rhythm of the heat production of growing young broiler chickens kept in groups between their 5th and 57th days of life was measured according to the method of short-time measuring (30-minute measuring periods) in dependence on environmental temperature (ET) between 40 and 5 degrees C in stages of 5 K by means of gas exchange and indirect calorimetry. The keeping temperature ranged from one experiment to the other from 35, 30, 25, 20 to 15 degrees C. The dependence of heat production on ET is parabolic in the medium and high ranges of temperature. As a rule, heat production increases progressively with very low ET. Thermoneutral temperature depends on both, the age (live weight) of the chickens and environmental temperature. Thermoregulatory heat production decreases with growing age. It changed from 24 kJ/kg LW0.75.d.K at the beginning to 8 kJ/kg LW0.75.d.K at the end of the experiments.     

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.     

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.     

Continuous measuring of heat production and activity during the course of the day in hungry growing rats

Heat production (indirect calorimetry) and motor activity were measured continuously with 4 repetitions at 8 male albino rats (24 h fasting) over 21 h (4 minute cycle of measured value registration). The average difference between maximum and minimum heat production in a 4-minute measuring period amounted to 82 +/- 14% (68 to 139%). There was a significant connection between heat production and activity. 7.9 +/- 1.2% of the heat production of the hungry rat could be ascribed to activity. In the course of the day of fasting (24 h) an average metabolism reduction of 15 kJ/kg LW0.75 could be observed.     

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.     

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.     

Circadian variation in heat production and respiratory quotient in growing broilers maintained at different food intakes and ambient temperatures.

1. Circadian variations in heat production (HP) rate and respiratory quotient (RQ) were measured in growing broilers maintained at 5 ambient temperatures (14 degrees, 17 degrees, 22 degrees, 27 degrees and 32 degrees C) and at 5 rates of feeding [ad libitum intake and 75%, 50%, 25% and 0% (fasting) of ad libitum intake]. 2. In most cases, the HP rate decreased from 10.30 h just after food was given) until 00.30 h (the 1-h dark period), showed an overshoot just after the 1-h dark period and then changed little. 3. Circadian variation in RQ, except in the fasted group, showed a similar pattern, which consisted of increase, decrease and constant phases. 4. Food intake affected the pattern of circadian variation in RQ, although ambient temperature had little effect. Possible effects of food intake on the pattern of circadian variation in HP rate were discussed.     

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.     

Influences of wet feeding and supplementation with ascorbic acid on performance and carcass composition of broiler chicks exposed to a high ambient temperature.

In two experiments was investigated whether feeding with an air-dry feed mixed with different amounts of water and/or supplemental ascorbic acid affect performance and carcass compositions of broilers exposed to a high ambient temperature (35 to 37 degrees C for 8 h/d and thermoneutral for 16 h/d). In the first trial, 64 one-week-old male broiler chicks were fed ad libitum in four dietary treatment groups for a 6-week period. Experimental mash diets were prepared by mixing a maize-soybean based standard broiler starter or finisher with tap water in the ratios of 0.0:1.0, 0.5:1.0, 1.0:1.0 and 1.5:1.0 (water:air-dry feed, w/w). More water in the diet increased BWG, DMI, abdominal fat and carcass weight, carcass CP, crude fat, but it deteriorated DM conversion efficiency. In the second experiment, 64 one-week-old male broiler chicks were given air-dry or wet (water:feed, 1.5:1) starter or finisher diets without or with ascorbic acid supplementation (0 and 250 mg/kg air-dry feed, resp.) ad libitum for a 6-week period. Ascorbic acid supplementation increased BWG, carcass weight and carcass CP significantly, while reducing carcass crude fat content. However, feeding broilers with a diet mixed with water in a ratio of 1.5:1.0 increased BWG, DMI, carcass weight and carcass lipid markedly, but deteriorated DM conversion efficiency. There was also a significant interaction between ascorbic acid and wet feeding, whereby ascorbic acid supplementation induced a significant reduction in carcass lipid contents of broilers fed on air-dry diets but not on wet diets. It is concluded that wet feeding, especially an addition of 150% water to produce a porridge like consistency, improved growth performance by increasing fat, ash and protein deposition in the body, while reducing DM conversion efficiency. It is also concluded that under heat stress supplemental ascorbic acid in air-dry diets stimulates broiler performance but not in wet diets.     

Diurnal rhythm in heat production and oxidation of carbohydrate and fat in pigs during feeding, starvation and re-feeding

Diurnal rhythm in heat production (HE), oxidation of carbohydrate (OXCHO) and fat (OXF) was calculated from daily measurements of gas exchange in 12 pigs [20-40 kg live weight, (LW)] during 6 days of near ad libitum feeding, followed by 4 days of starvation and 4 days of re-feeding. All measurements, divided in five times intervals from 12.00 to 8.00, showed the highest values of HE, reflecting the animals' energy requirements, between 12.00 and 16.00 gradually declining to the lowest values between 4.00 and 8.00. The values measured in the interval 4.00-8.00 were considered as a basal metabolic rate (BMR), being in all measurements 25% lower than during 12.00-4.00. The lowest BMR was measured on the fourth day of starvation (21.7 kJ/h.kg(0.75)). By transition from feeding to starvation, OXCHO declined gradually, but was for 16 h able to cover the energy requirement with no contribution from OXF. The decline in OXCHO proceeded for 40 h and reached zero between 4.00 and 8.00 on the first day of starvation with the energy requirement being covered by OXF. The HE during starvation was 25-30% lower than during feeding caused by absence of feed-induced thermogenesis and by the transition from OXCHO to OXF. Immediately after re-feeding dietary carbohydrates were oxidized, however, there was still a substantial OXF, proceeding until the next feeding. From the second day of re-feeding the contribution of substrates to the total HE was re-established with no OXF and the same level of HE as during feeding.     

Effects of temperature treatments on the heat production of starving chickens

1. Heat production was measured for about 24 h at six temperatures from 2 to 35 degrees C on individually starved broilers that had been subjected to four treatments; these were acclimated or unacclimated to these temperatures, or to these temperatures for 12 h and to 22 degrees C for 12 h (alternated) during each 24-h period. 2. Response curves relating heart production and environmental temperature for the four different treatments differed significantly. Only the unacclimated birds subjected to the alternated temperatures increased heat production at 35 degrees/22 degrees C. Major effects of acclimation were observed mainly in the cold. 3. The relationship between daily endogenous nitrogen (N) excretion and heart production (mg N/kJ) was constant at the different temperatures, but acclimation and alternating temperature increased N excretion. 4. Evaporative heat loss was reduced by alternating temperature at the high temperatures, and by maintaining temperature constant in the cold.     

Effect of Vitamin C on pulmonary hypertension and muscularisation of pulmonary arterioles in broilers

1. Three hundred and eighty 1-day-old Arbor Acres broilers were divided into control (A) and experimental (B, C, D, and E) groups. 2. After 14 d of age the experimental groups were subjected to a cool temperature challenge by lowering the temperature 1 to 2°C per day down to 12°C, and maintaining this temperature until 7 weeks of age. 3. At the same time, l.5 mg/kg 3,3,5-triiodothyronine (T 3 ) was added to the diet of groups D and E, and 500mg/kg ascorbic acid (vitamin C) to the diet of groups C and E. 4. The incidence of pulmonary hypertension syndrome (PHS), body weight gain and feed intake were measured weekly. Lung and blood samples were collected weekly from 10 birds per group beginning on d 14, and the percentage of thick-walled peripheral lung vessels (%TWPV) and packed cell volume (PCV) were determined. 5. The lower ambient temperature and diets supplemented with T 3 increased PHS incidence and % TWPV and decreased body weight gain. 6. There was an increase in PCV after 5 weeks of age under lower ambient temperature 3 and the PCV values 14 were also significantly increased by T 3 . 7. Vitamin C supplementation reduced PHS incidence and % TWPV but did not change packed cell volume, body, weight gain, feed intake, or feed conversion. 8. It is concluded that vitamin C reduced PHS and the associated muscularisation of pulmonary arterioles induced by exposing broilers to cool environmental temperatures and feeding them with T 3 .     

The effect of the protein level of feed on the energy maintenance requirement of rats during the course of growth and after the conclusion of the intensive growth phase using different feeding regimens

In two experiments with male Wistar rats energy metabolism was measured on the feeding level of maintenance in the course of growth and in various adult periods after the application of feed mixtures with various protein-carbohydrate quotas (10, 40 and 70% crude protein) according to two different feeding regimes. While there was a change of protein levels between the animal groups in periods 1 to 3 and 8 to 10 from one period to the other, the protein levels in periods 4 to 7 and 11 to 13 remained the same for each animal group. Irrespective of the feeding regime, a dependence of the energy maintenance requirement on the nutrients according to the expected values was measured, which result from the different efficiency of ATP synthesis in the oxidative degradation of the nutrients. On an average of the periods maintenance requirement amounted to 357 +/- 21, 399 +/- 16 and 443 +/- 28 kJ/kg LW0.75.d (experiment 1) and 350 +/- 29, 383 +/- 34 and 442 +/- 30 kJ/kg LW0.75.d (experiment 2) for 10, 40 and 70% crude protein in the feed. The relation between the maintenance requirement values was 100:112:124 and 100:109:126. This contrasts with the relative expected values of 100:108:115 and 100:109:116.     

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.     

Effects of exposure to high ambient temperature and dietary protein level on sow milk production and performance of piglets.

The effects of high ambient temperature and level of dietary heat increment on sow milk production and piglet performance over a 28-d lactation were determined in 59 multiparous crossbred Large White x Landrace pigs kept at a thermoneutral (20 degrees C) or in a hot (29 degrees C) constant ambient temperature. Experimental diets fed during lactation were a control diet (NP; 17.6% CP) and two low-protein diets obtained by reduction of CP level (LP; 14.2% CP) or both reduction of CP and addition of fat (LPF; 15.2% CP); the NE:ME ratio was 74.3, 75.6, and 75.8% for NP, LP, and LPF diets, respectively. All diets provided 0.82 g of digestible lysine/MJ of NE, and ratios between essential AA and lysine were above recommendations. Creep feed was provided after d 21 of lactation. Reduction of CP level did not influence (P > 0.10) milk production, milk composition, or piglet performance. Despite higher nursing frequency (39 vs 34 sucklings per day), milk production decreased (P < 0.01) from 10.43 to 7.35 kg/d when temperature increased from 20 to 29 degrees C. At d 14, DM (18.6 vs 18.1%) and energy (4.96 vs 4.75 MJ/kg) contents in milk tended (P = 0.09) to be higher in sows kept at 29 degrees C. Over the 28-d lactation, piglet BW gain and BW at weaning decreased (P < 0.01) from 272 to 203 g/d and 9.51 to 7.52 kg, respectively, when temperature increased from 20 to 29 degrees C. Daily creep feed intake over the 4th wk of lactation was higher (P < 0.01) at 29 degrees C than at 20 degrees C (388 vs 232 g/litter, respectively), which was reflected in a greater increase in BW gain between wk 1 to 3 and wk 4 at the higher temperature (147 vs 130%); BW gain between weaning and d 14 postweaning was higher (P < 0.05) for piglets originating from sows kept at 29 degrees C (280 vs 218 g/d). In connection with their lower growth rate, DM (31.2 vs 33.0%), protein (15.5 vs 16.0%), lipid (12.3 vs 13.9%), and energy (8.39 vs 9.09 kJ/g) contents in weaned, slaughtered piglets were lower (P < 0.01) at 29 than at 20 degrees C. In conclusion, modification in the CP:NE ratio in order to decrease dietary heat increment did not affect milk production and piglet performance in thermoneutral or hot climatic conditions. Our results confirm the negative effect of high ambient temperatures on milk yield and emphasize the importance of creep feed supply to improve pre- and postweaning growth of piglets in these conditions, especially when weaning occurs after 3 wk of age.     

Effects of enzymatically treated Artemisia annua L. on growth performance and some blood parameters of broilers exposed to heat stress

To evaluate the effects of enzymatically treated Artemisia annua L. (EA) on growth performance and some blood parameters of broilers exposed to heat stress (HS), 320 22‐day‐old Arbor Acres male broilers were randomly allotted into five groups with eight replicates of eight birds each. Broilers in the control group were housed at 22 ± 1°C and fed the basal diet. Broilers in the HS, HS‐EA_0.75, HS‐EA_1.00 and HS‐EA_1.25 groups were reared under HS (34 ± 1°C for 8 h/day and 22 ± 1°C for 16 h/day), and fed basal diet with 0, 0.75, 1.00 and 1.25 g/kg EA, respectively. The experiment ended at 42 days. Dietary 1.00 and 1.25 g/kg EA decreased blood pH and elevated body weight gain, feed intake and carcass yield compared to the HS group. Broilers fed EA diets had lower serum concentrations of malondialdehyde and corticosterone and activities of alanine aminotransferase and aspartate aminotransferase, and higher serum total superoxide dismutase activity, tri‐iodothyronine concentration and tri‐iodothyronine/thyroxine than the HS group. Serum catalase activity in HS‐EA_1.00 and HS‐EA_1.25 groups and activity to inhibit hydroxyl in the HS‐EA_1.00 group were higher than the HS group. In conclusion, dietary 0.75–1.25 g/kg EA addition alleviated HS induced impairments in broilers.