The effect of total sulfur amino acid levels on growth performance, egg quality, and bone metabolism in laying hens subjected to high environmental temperature

This study evaluated the effects of total sulfur amino acid (TSAA) levels on performance, egg quality, and bone metabolism in laying hens subjected or not to high environmental temperature (HT). HyLine W36 layers (n = 144) were randomly distributed in a 2 × 3 factorial arrangement. Room temperature (control, CR: 21°C/24 h; and high temperature, HR: 32°C/8 h) and diets (70, 85, or 100% of TSAA) were the main factors, with 4 replicates of 6 birds (19 to 45 wk). The TSAA levels were obtained by adding L-Methionine (L-Met) to the basal diet (70% of TSAA) until 85 and 100% of TSAA were reached. At weeks 21, 34, and 45, growth performance, egg production, and egg quality traits were evaluated. At 45 wk, bones were evaluated for collagenous and non-collagenous proteins, bone volume, mineral content, and mineral density from total, cortical, trabecular, and medullary portions. When interactions were found, the increase of TSAA levels (85 and 100%) was able to counteract the negative effects of HT. In general, HT reduced egg production (P < 0.05) and did not significantly affect bone quality. The birds fed 70% of TSAA showed higher feed conversion, lower body weight, egg weight, and egg mass than birds fed 85 and 100% of TSAA in at least one phase. The birds fed 100% of TSAA showed higher egg production and egg mass than the other treatments at 21 wk of age. The cortical and trabecular bone mineral densities were higher for birds fed 100 than 70% of TSAA, whereas the medullary bone mineral content and density were higher for birds fed 70 than 100% of TSAA. In conclusion, HT had negative impact on performance, egg quality and no effect on bone development. The supplementation of L-Met until either 85 or 100% of TSAA levels were reached was enough to assure good performance, egg quality, and bone development in laying hens subjected or not to HT.

Optimal dietary concentration of vitamin E for alleviating the effect of heat stress on egg production in laying hens

1. The effects of different dietary concentrations of vitamin E (alpha-tocopherol acetate) were investigated on laying hens exposed to chronic heat stress at 32 degrees C from 26 to 30 weeks of age. 2. Diets containing 5 dietary concentrations of vitamin E (a control diet containing 10 mg alpha-tocopherol/kg or this diet supplemented to contain 125, 250, 375 and 500 mg alpha-tocopherol/kg) were fed to 335 birds. Half of the birds received the supplemented diets for only 4 weeks before the heat stress period (short supplementation duration, SSD) and were fed on the control diet for a further 12 weeks. The remaining birds were fed on the supplemented diets throughout the experiment, 4 weeks before, 4 weeks during and 8 weeks after the heat stress period (long supplementation duration, LSD). 3. Egg production was significantly higher during (80-6 vs 68.9%, P<0.02) and after (75.3 vs 62.7%, P<0.02) the period of stress in the LSD group fed on the diet containing 250 mg vitamin E/kg compared with the group fed on the control diet. LSD birds given 375 and 500 mg vitamin E/kg also had higher egg production than control birds during heat stress but the differences failed to reach significance (74.6 vs 68.9% and 77.1 vs 68.9% respectively). In the SSD groups, mean egg production of the birds given the diets supplemented with 125 mg vitamin E/kg or more was significantly different from the control group after heat stress (70.3 vs 62.7%, P<0.05). Egg weight and food intake were similar in all the groups. 4. Plasma and liver vitamin E concentrations were proportional to the vitamin E intake before the stress period, dropped during heat stress in the SSD groups but were maintained at concentrations closer to those observed before heat stress in the LSD groups. 5. It is concluded that a dietary supplement of 250 mg vitamin E/kg provided before, during and after heat stress is optimum for alleviating, at least in part, the adverse effects of chronic heat stress in laying hens.

Acute high environmental temperature and calcium-estrogen relationship in the hen

Much is known about the effects of high environmental temperature (HT) on egg production, but very little is understood about the mechanisms that underlie them. Two experiments were conducted to examine the effects of acute heat stress on circulating estradiol, on calcium uptake by gut tissue, on bone resorption, and on the dynamic relationship between estradiol and calcium in the hen during one ovulatory cycle. In one study, hens were moved individually and randomly into a hot [HT: temperature (T) = 35 C, relative humidity (RH) = 50%; n = 18] or a control, thermoneutral (TN: T = 23 C, RH = 50%; n = 18) environment immediately after a mid-sequence oviposition and brachial vein cannulation. Blood samples (2 mL) were collected every 3 h for 21 h for ionized calcium (Ca2+) and pH determinations and from which aliquots were frozen for 17 beta-estradiol (E2), total calcium (TCa), and inorganic P analysis. Excreta and urine were assayed for TCa and hydroxyproline (OHPr), respectively. A second study was conducted to determine the effects of HT (T = 35, H = 50%, 12 h) vs TN (T = 23 C, RH = 50%, 12 h) on the ability of duodenal cells to take up calcium (CaT). Blood pH and calcium responded to HT as expected (pH increased, Ca2+ decreased, and TCa decreased) and the cyclic pattern of Ca2+ in blood was abolished. The ratio of Ca2+:TCa decreased sharply at approximately the onset of shell calcification in control hens, but in HT hens there was no clear change in the ratio of any point in the cycle. The pattern of E2 typical of hens under normal conditions was significantly depressed in plasma of HT hens. Calcium uptake by duodenal epithelial cells of HT hens was lower than in TN hens. There was a clear inverse correlation between blood Ca2+ and urine OHPr in TN hens (r2 = -73, P = 0.0021) but not in HT hens (r2 = -27, P = 0.32). In addition to alterations in acid-base balance and the status of Ca2+, diminished ability of duodenal cells to transport calcium may be a critical factor in the detrimental effects of heat stress on egg production (numbers), eggshell characteristics, and skeletal integrity often documented in the laying hen.

Environmental heat stress does not reduce blood ionized calcium concentration in hens acclimated to elevated temperatures

Changes in blood concentrations of ionized calcium and total calcium were measured in broiler breeder hens (42 wk old) relative to egg cycle and environmental temperatures. Two environmental temperature treatments were used: 1) temperature cycled daily from a low of 10 C at 0300 h to a high of 25 C at 1600 h; and 2) temperature cycled from a low of 21 C at 0300 h to a high of to a high of 39 C at 1600 h. Serial blood samples were collected from five laying hens per temperature treatment via cutaneous ulnar vein cannula beginning at the time of oviposition and every 4 h thereafter until the next oviposition. Neither blood concentration of ionized calcium nor total plasma calcium was affected by temperature. Results suggest that the supply of calcium available in blood for shell deposition is not diminished in hens acclimated to high environmental temperatures.

Interaction of feeding time and temperature and their relationship to performance of the broiler breeder hen

Experiments with broiler breeder hens were undertaken to determine effect of feeding time and environmental temperature on various production variables, body weight, and feed consumption. Two temperature treatments were used: low cyclic temperature (10 to 25 C), and high cyclic temperature (21 to 39 C). The three feeding treatments were: fed one daily meal either at 0700 h (Treatment 1) or 1800 h (Treatment 2), or one-half the daily amount at 0700 h and the other half at 1800 h (Treatment 3). In another experiment, hens were assigned to feeding times of either 0700 or 1800 h. Feeding time and temperature did not markedly affect rate of egg production; however, hens at high temperature fed two meals per day produced the fewest eggs. High temperature caused significant reductions in egg weight, specific gravity, and shell thickness. Feeding time and temperature had no effect on time of oviposition, ovulation, or the transit time of the egg through the oviduct. Significant body weight loss occurred in hens at high temperature and fed at 0700 h. Both high temperature and feeding one-half of the daily feed at 0700 and the other half at 1800 h caused a reduction in feed consumption.

Sample size required for various methods of assessing bone status in commercial leghorn hens

A study was conducted to determine the appropriate sample size required for various methods used to assess tibial bone status in commercial Leghorn hens. The methods used were in vivo bone mineral content (BMC), in vivo bone density (BD), in vitro BMC, in vitro BD, tibia bone breaking strength (TBS), and percentage bone ash (BA). Dietary total P levels of .4, .45, .5, .55, and .7% were used as treatment source of variation. Twenty hens were sampled randomly to represent each dietary treatment. The CV for each bone status comparison method was estimated and was used in a procedure to estimate the sample size requirement for detecting a difference of delta between treatments. The sample size required to detect the difference between treatment means varied depending on 1) the method used to compare bone status 2) the difference between the treatment means to be detected as significant (delta); and 3) the level of significance (alpha) assumed. The sample size required for various methods are tabulated at .01, .05, and .1 level of significance and for 2.5, 5,7.5, 10, 15, and 20% delta. To detect an actual difference of 5% from the mean to be significant, at the .05 level of significance, a sample size of 44, 22, 31, 23, 47, and 85 hens per treatment would be necessary for in vivo BMC, in vivo BD, in vitro BMC, in vitro BD, TBS, and BA methods, respectively. The estimated sample size values would help researchers in designing experiments that involve bone status comparison of commercial Leghorn hens.

Effect of roost temperature on performance of chickens in hot ambient environments

A split-plot experiment was conducted in thermally controlled chambers using Columbian Plymouth Rock chickens to determine the effect of water-cooled roosts on performance in hot ambient conditions. The birds were subjected to 25 +/- 1, 35 +/- 1, and 25 +/- 1 C ambient temperature treatments for 2, 3, and 2 wk, respectively. Roost temperature treatments were either cool (20 +/- 1 C) or air-equilibrated (25 +/- 1 or 35 +/- 1 C). The performance parameters evaluated were percentage hen-day egg production, egg weight, feed intake, feed conversion, fertility, and hatchability. Birds subjected to the water-cooled roost treatment had consistently higher performance than birds using the air-equilibrated roost under all three ambient temperatures. Both ambient and roost temperature treatments significantly influenced percentage hen-day egg production, average daily feed intake, and percentage hatchability (P less than or equal to .05). However, the biggest differences in performance were observed during the heat-stress period. Decreases in performance during the heat-stress period from the thermoneutral control values were: 5.95 and 13.1 percentage points for hen-day egg production, 22.2 and 34.8 percentage points for average daily feed intake, and 5.17 and 15.38 percentage points for hatchability in water-cooled and air-equilibrated roost treatments, respectively. The ambient and roost temperature treatments did not significantly affect egg weight, feed conversion, or percentage fertility. The improved performance with water-cooled over air-equilibrated roost treatments, especially during heat-stress periods, indicates that the water-cooled roosts minimized the deleterious effects of heat stress through conductive heat loss from the birds to the roost.

Effect of sodium aluminosilicate, oyster shell, and their combinations on acid-base balance and eggshell quality

Three experiments were conducted to determine the effect of sodium aluminosilicate (SAS), oyster shell (OS), and their combinations on production performance, eggshell quality, and acid-base balance. Experiments 1 and 2 were conducted during summer and Experiment 3 in winter. In Experiment 1, the effect of two levels of SAS (0 and .75%) and two levels of OS (0 and 50% substitution for pulverized limestone) was studied. In Experiment 2, the effect of SAS (.75%) with or without Na adjustment was investigated. When Na was adjusted, various sources of chloride were used to maintain an adequate level of this mineral. Calcium and available P were maintained at a constant 3.5 and .4%, respectively in Experiments 1 and 2. In Experiment 3, the levels of SAS and OS were similar to those of Experiment 1, but dietary Ca was either 2.8 or 3.5%. Egg production performance was not influenced by dietary treatments in Experiments 1 and 2 (P greater than .05). Egg production, but not egg mass, was reduced due to SAS in Experiment 3 (P less than .05). Dropping moisture increased when SAS was used in the diets with or without Na correction. Shell quality increased (P less than .05) due to SAS in the summer (Experiments 1 and 2) but not in the winter (Experiment 3). The shell quality response due to SAS was independent of Na correction or the source of dietary chloride. The OS increased shell quality in both summer and winter (P less than .05). Combinations of SAS and OS did not have an additive effect on shell quality (P greater than .05). Blood acid-base balance, plasma Ca and P, bone ash, bone Ca, and Ca retention were not influenced by dietary treatments. The results suggest that elevated environmental temperatures may be required in order for SAS to show its optimum effect on shell quality.

Influence of wet and dry feed on laying hens under heat stress

Two experiments were carried out with a split-plot design over time using White Leghorn hens, 161 days of age. The experiments were conducted to determine the effect of two ambient temperatures (21.1 versus 29.4 C in Experiment 1 and 21.1 versus 33.3 C in Experiment 2) on feed and water consumption using four dietary regimens. The day was divided into two feeding periods: a.m. (0600 to 1300 h) and p.m. (1300 to 0600 h the next morning). The four regimens were as follows: dry feed during both a.m. and p.m. periods; dry feed during a.m. period and wet feed (50% moisture) during the p.m. period; wet feed in the a.m. and dry feed in the p.m.; and wet feet during both a.m. and p.m. periods. The hens were maintained on a 14 h light: 10 h dark lighting program. The hens consumed the greatest quantity of DM and water during the p.m. period, regardless of the environmental temperature to which the hens were exposed. Constant heat stress at 29.4 and 33.3 increased (P less than or equal to .05) drinking water intake during the a.m. but not during the p.m. period. The use of wet feed and dry-wet feed provided a 38 and 48% increase (P less than or equal to .05), respectively, in DM intake when compared with the use of dry feed at 33.3 C. Exposure of laying hens to high environmental temperatures (29.4 and 33.3 C) decreased (P less than or equal to .05) albumen and shell weight; yolk weight was depressed only at 33.3 C. The use of wet feed (50% moisture), ad libitum, or in the p.m. stimulated DM intake at 33.3 C.

Effect of dietary fat and environment on lipogenesis by large white breeder turkeys

An experiment was conducted to evaluate the effects of either a low-fat (8% of total calories) or high-fat (47% of total calories) diet on Large White breeder females maintained at a constant (21 C) or a cyclic temperature regimen (12 to 27 C). Each diet was fed to 32 hens individually caged in the cyclic condition and 46 in the constant condition. Energy consumption, reproductive performance, and in vitro lipogenesis were monitored for hens subjected to both temperature and dietary treatments. Hens consumed more (P less than .05) dietary energy when maintained at a constant temperature or when fed the low-fat diet. Hens also produced more (P less than .05) eggs when maintained under cyclic temperature conditions, although this observation was tempered by the fact that fewer hens were broody. More (P less than .05) of the fertile eggs from hens held at the cyclic temperature resulted in live poults. The high-fat diet decreased (P less than .05) in vitro lipogenesis in hens and may also decrease the maintenance energy requirement by providing a preformed fatty acid pool for egg lipids. The high-fat also decreased (P less than .05) liver lipid and the activities of fatty acid synthetase and malic enzyme.

The effect of cyclic and constant ambient temperatures on feed consumption, egg production, egg weight, and shell thickness of hens

Groups of 18 hens, 230 days of age, were housed in each of three climatic chambers with light schedules of 14L:10D. One was maintained at a constant temperature of 23.9 C, the second was cycled between 15.6 and 37.7 C (mean, 26.7 C), and the third was cycled between 21.1 and 37.7 C (mean, 29.4 C). In Experiment 1, the high temperature peaked during the dark period at 0200 hr and in Experiment 2, the high temperature peak was at 1400 hr during the light period. The birds had free access to a commercial breeder feed in these two experiments. The results from three 2-week observation periods indicated no significant differences in percent hen-day production, grams of feed per gram of egg mass, or overall body weight change but feed intake per day, egg weight, and shell thickness were significantly reduced by mean temperatures of 26.7 and 29.4 C in cycling chambers. The pair-feeding of birds in the 23.9 C constant chamber compared with those in the cycling 29.4 C chamber resulted in production of significantly heavier eggs with thicker shells without significantly influencing any of the other parameters. The reductions in egg weight and shell thickness observed at cyclic temperatures were not simply a result of a reduction in nutrient intake at high temperatures but also the direct effect of heat stress on the hens. In the 23.9 C constant temperature chambers, a reduction in AME of the feed for the hens fed ad libitum was observed but not for hens pair-fed to hens in the 29.4 C cyclic chamber.

Dietary self-selection of laying hens inadequate to overcome the effects of high environmental temperature

Two environmental temperatures, 21 and 30 C, were used during a 28-day experimental period. There were two groups of hens in each temperature treatment. The control groups (C) were given a conventional balanced diet and each dietary self-selection group (S-S) was provided, on an individual hen basis, three diets each one being high in energy, protein, or calcium. The S-S groups had significantly reduced egg production, which probably resulted from the significantly reduced protein intake. Egg weight and energy intake were reduced in the S-S group at 21 C while calcium intake and egg shell strength at 30 C were higher as compared to the corresponding C group. Dietary self-selection did not enable hens to regulate nutrient intake for comparable performance to hens provided one balanced diet. Also, the detrimental effects of high environmental temperature were not overcome by dietary self-selection.

Effect of heat stress and diet composition on performance of White Leghorn hens

A total of 192 Single Comb White Leghorn pullets were divided into three groups to study the effect of heat stress and diet composition on feed intake and laying performance at 21, 25, and 33 weeks of age. For each age group all birds were fed a control diet [17.1% crude protein (CP), 2770 kcal metabolizable energy (ME)/kg] for a 7-day period. During this time they were kept at a temperature of 18 C. The temperature was then immediately increased to 35 C, and groups of 16 birds offered either the control diet, a high protein diet (43.5% CP), a high energy diet (3371 kcal ME/kg), or a diet of high nutrient density (28.3% CP, 2842 kcal ME/kg, and 6.5% Ca) for a 3-day period. After the 3-day test period, temperature was returned to 18 C, although birds were still offered the experimental diets for an additional 4 days prior to returning to the control diet. Production parameters were measured for individual birds. Feed consumption, egg production (except for the 21-week-old birds), egg weight, and egg shell thickness decreased (P less than .05) with heat stress. Increases in energy and calcium intake helped partially to maintain normal egg production, egg weight, and egg shell deformation. Egg weight and egg shell deformation returned to pretest levels within an 8-week postexperimental period. With the exception of those birds receiving the control and high nutrient density diets at 21 weeks of age, data collected over the test periods showed that heat stress caused a significant reduction (P less than .05) in liveweight birds.

The effects of sorghum tannin and methionine level on the performance of laying hens maintained in two temperature environments

At the conclusion of a 31-day recovery period following a previous sorghum feeding trial (Sell et al., 1983), 128 White Leghorn hens were used in a subsequent 44-day study to investigate the effects of methionine supplementation of sorghum-soybean meal diets on laying hen performance. The hens were arrayed into four nutritional treatments in each of two constant environments (22 and 28 C) based on their egg production during the last 10 days of the recovery period within a previous treatment and environment so that equal numbers of hens from the previous treatments were represented in the new treatments. Nutritional treatments consisted of either low (RS610) or high (savanna) tannin sorghum-soybean meal diets containing 13% protein and supplemented with either .2% DL-methionine (Met) or an isonitrogenous level of L-glutamic acid (Glu). With both high (HTS) and low tannin sorghum (LTS) diets, Met supplementation resulted in greater egg production, egg weight, feed intake, and less hen weight loss as compared with Glu addition, but with the exception of hen weight loss, the magnitude of the response was much greater with HTS. Hens fed the HTS diet supplemented with Glu showed greatly reduced egg production and feed efficiency as compared with those fed LTS similarly supplemented. In contrast, little difference in egg production and feed efficiency was observed between hens fed HTS and LTS diets supplemented with Met. All parameters studied except hen weight appeared to be reduced slightly by the higher temperature.

The effects of sorghum tannin and protein level on the performance of laying hens maintained in two temperature environments

A study was conducted to investigate the effect of sorghum grain tannins on the performance of laying hens. A total of 144 White Leghorn hens were arrayed according to egg production during a 10-day preexperimental period into eight groups consisting of four nutritional treatments in each of two constant temperature environments (22 and 28 C). The nutritional treatments consisted of low (RS610) and high (Savanna) tannin sorghum grains compared isonitrogenously within a protein level at two protein levels (11.5 and 14.5%) in sorghum-soybean meal diets. These diets were fed for an experimental period of 6 weeks. Egg production and feed efficiency were reduced and weight loss was increased by 11.5% protein as compared with 14.5% protein. Tannin significantly reduced egg production and feed efficiency at both protein levels while egg specific gravity and shell thickness were adversely affected only at the lower level of protein. Egg weight and weight loss of hens were not affected by tannin. Except for weight loss, all parameters were slightly reduced by the higher temperature. At the end of the experiment, all hens were placed on a commercial laying ration for a 31-day period. Recovery from the treatment effects was evidenced by the similar egg production, body weight, egg weight, and shell characteristics among the previous treatments at the end of this period.

Evaporative cooling of laying hens in Hawaii

A study was conducted to determine the effects of evaporative cooling on laying hens in a tropical environment of high relative humidity. Four strains of Single Comb White Leghorn pullets totaling 1,248 birds were housed in two identical enclosed houses except that in one the incoming air was passed through an air wash prior to entering the unit. The maximum temperature averaged 3.0 C lower and the relative humidity 15% higher in the unit cooled by evaporation. No significant differences were noted among any of the production parameters measured, although there was a numerical advantage for the evaporatively cooled unit in egg production, egg size, egg specific gravity, cracked eggs, and mortality. There were no consistent differences among the strains between the two units.

Effects of ambient temperature on sexual maturity in chickens

Ninety-six, 14-day-old Single Comb White Leghorns (48 males and 48 females) in each of two trials were divided into three groups and grown thereafter under one of the ambient temperatures of 21, 29, or 35 C. Age at sexual maturity of males was decreased in both trials as temperature was increased. First semen was produced at 54 and and 56 days of age in Trials 1 and 2, respectively, when the ambient temperature was 35 C and 68 and 63 days at 21 C for Trials 1 and 2, respectively. Sexual maturity of females was significantly delayed at the highest ambient temperature. Semen quality was only slightly affected by the highest ambient temperature. Although egg production was seriously affected at 35 C, fertility and hatchability, except in a few instances, were only mildly affected.

Effect of diet composition on feed intake and growth of chicks under heat stress. II. Constant vs. cycling temperatures

Broiler chicks 5 to 7 weeks of age were subjected to a constant cool (14 +/- 1 C) or hot (31 +/- 1 tc) environment and fed diets varying in fat level and energy and nutrient density. Chicks gained significantly (P less than or equal to .01) more body weight in the cool than in the hot environment. In both environments chicks fed high fat or high fat-high density diets gained more weight than those fed diets low in fat, and there was no diet X temperature interaction. When temperatures were cycled diurnally (cool, 14 to 22 C; hot, 22 to 33 C), as would occur under natural conditions, the growth depression due to heat stress was less in chicks fed the diets high in fat. The special benefit of fat at high temperature was probably the result of reduced heat increment. Under constant temperature conditions, chicks in the cool environment, pair-fed at the same level of feed intake as those in the hot environment, gained significantly (P less than or equal to .05) more weight than the latter. These data indicated that factors other than reduced feed intake contributed to the growth depression associated with high temperature. Thyroid size was significantly (P less than or equal to .05) reduced in chicks held at constant high temperature and slightly but not significantly reduced in chicks subjected to cyclic heat stress. This decrease in thyroid size suggested there is a practical limit on overcoming by nutritional means the deleterious effects of heat stress in broilers.

Effect of diurnal or nocturnal heat stress on egg formation

1. Mature laying hens were subjected to ambient temperatures sufficient to maintain body temperature of 43 degrees C for periods of 6 to 7 h during the day (eight periods) or the night (five periods). This did not reduce total daily food consumption. 2. The effect of heat stress during the day was mostly on egg-shell quality, being adverse and significant. During the night heat stress caused a significant decrease in egg production, its effect during the day was less marked in this respect. 3. Heat stress thus seems mostly to affect the early stages of shell formation, while its effect on egg production seems to depend on the time at which it occurs in relation to ovulation. 4. These results suggest that egg production is directly affected by heat stress; prolonged heat stress probably also acts indirectly, by suppression of food intake.