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The objectives of this study were to evaluate the effects of feeding 5 different energy and nutrient dense diets to Hy-Line W-36 hens on long-term performance and economics. A total of 480 19 wk old Hy-Line W-36 Single Comb White Leghorn hens were weighed and randomly allocated to 6 replicate groups of 16 hens each (2 adjacent cages containing 8 hens per cage, 60.9×58.4 cm) per dietary treatment in a randomized complete block design. The hens were fed 5 treatment diets formulated to contain 85, 90, 95, 100, and 105% of the energy and nutrient recommendations stated in the 2009 Hy-Line Variety W-36 Commercial Management Guide. Production performance was measured for 52 wk from 19 to 70 wk age. Over the course of the trial, a significant increasing linear response to increasing energy and nutrient density was seen for hen-day egg production, egg weight, egg mass, feed efficiency, energy intake, and body weight (BW). Feed intake showed no significant linear level response to increasing energy and nutrient density except during the early production cycle. No consistent responses were noted for egg quality, percent yolk, and percent egg solids throughout the study. Significant linear responses due to energy and nutrient density were seen for egg income, feed cost, and income minus feed cost. In general, as energy and nutrient density increased, egg income and feed cost per hen increased, but income minus feed cost decreased. Overall, these results indicate that feeding Hy-Line W-36 hens increasing energy and nutrient-dense diets will increase egg production, egg weight, egg mass, feed efficiency, energy intake, BW, egg income, and feed cost, but decrease egg income minus feed cost. However, these benefits do not take effect in early production and seem to be most effective in later stages of the production cycle, perhaps "priming" the birds for better egg-production persistency with age., (© 2015 Poultry Science Association Inc.)

An experiment was conducted using 588 Hy-Line W-36 hens (68 wk of age) to evaluate if laying hens can be successfully molted by ad libitum feeding various levels of 3 sources of distillers dried grains with solubles (DDGS). Treatment 1 consisted of a 47% corn (C):47% soy hulls (SH) molt diet (C:SH) fed for 28 d (positive control). Treatments 2, 3, and 4 were molt diets containing 94% DDGS from the 3 sources fed for 28 d. Treatments 5, 6, and 7 were 32% C: 42% SH: 20% DDGS, from each of the 3 DDGS sources, also fed for 28 d. At the end of the 28-d molt period, all hens were fed a 16% CP corn-soybean meal layer diet. Body weight loss during the molt period was significantly greater (P < 0.05) for hens fed the C:SH diet (26%) than hens fed the diets containing DDGS, and the reduction in BW loss varied among DDGS sources. Feed intake was lower (P < 0.05) for the C:SH control treatment compared with most DDGS treatments. Hens fed the C:SH diet had egg production near 0% during the last 3 wk of the molt period. Hens on the other treatments did not have mean egg production below 17% during the molt period (wk 1 to 4), and the reduction in egg production varied among DDGS sources. Postmolt hen-day egg production (5-41 wk) did not significantly differ among treatments; however, egg mass and egg specific gravity were generally reduced (P < 0.05) for hens fed the 94% DDGS molt diets compared with hens fed the C:SH diet. This study showed that molt and postmolt performance responses varied among DDGS sources; however, none of the molt diets containing 20 to 94% DDGS yielded molt period reductions in BW or egg production similar to a 47% C: 47% SH diet., (Poultry Science Association Inc.)

An experiment was conducted with 672 Hy-Line W-36 Single Comb White Leghorn hens (69 wk of age) to evaluate the effects of feeding varying levels of corn distillers dried grains with solubles (DDGS) with corn, wheat middlings, and soybean hulls on long-term laying hen postmolt performance. The control molt treatment consisted of a 47% corn:47% soybean hulls (C:SH) diet fed ad libitum for 28 d. Hens fed the other 7 treatments were limit fed 65 g/hen per day for 16 d, and then fed 55 g/hen per day for 12 d. Hens on treatments 2 and 3 were fed 49% C:35% wheat middlings (WM) or SH:10% DDGS diets (C:WM:10DDGS, C:SH:10DDGS). Hens on treatments 4 and 5 were fed 49% C:25% WM or SH:20% DDGS diets (C:WM:20DDGS, C:SH:20DDGS). Those on treatments 6 and 7 were fed 47% C:47% DDGS (C:DDGS) or 47% WM:47% DDGS (WM:DDGS) diets. Those on treatment 8 were fed a 94% DDGS diet. At 28 d, all hens were fed a corn-soybean meal layer diet (16% CP) and production performance was measured for 36 wk. None of the hens fed the molt diets went completely out of production, and only the C:SH and C:SH:10DDGS molt diets decreased hen-day egg production to below 5% by wk 4 of the molt period. Postmolt egg production was lowest (P < 0.05) for the C:WM:20DDGS treatment. No differences (P > 0.05) in egg weights were detected among treatments throughout the postmolt period. In addition, no consistent differences were observed among treatments for egg mass throughout the postmolt period. Overall results of this study indicated that limit feeding diets containing DDGS at levels of 65 or 55 g/hen per day during the molt period did not cause hens to totally cease egg production.

An experiment was conducted using 504 Hy-Line W-36 Single Comb White Leghorn hens (69 wk of age) randomly assigned to 1 of 7 treatments. These treatments consisted of a 47% corn:47% soy hulls diet (C:SH) fed ad libitum; a 94% corn diet fed at a rate of 36.3, 45.4, or 54.5 g/hen per day (CORN 36, CORN 45, and CORN 54, respectively); and a 94% corn distillers dried grains with solubles (DDGS) diet fed at the same rates as the previous corn diets (DDGS 36, DDGS 45, and DDGS 54, respectively) during the molt period of 28 d. The intent was to feed the DDGS diets for 28 d; however, all hens on these diets had very low feed intakes and greater than anticipated BW loss. Thus, they were switched to a 16% CP corn-soybean meal layer diet on d 19 of the molt period. At d 28, hens on all treatments were fed the same corn-soybean meal layer diet for 39 wk (73 to 112 wk of age). All DDGS diets and the CORN 36 diet resulted in total cessation of egg production during the molt period and egg production of hens fed the CORN 45, CORN 54, and C:SH diets had decreased to 3 and 4%, respectively, by d 28. Body weight loss during the 28-d molt period ranged from 14% for the CORN 54 diet to approximately 23% for the 3 DDGS diets. Postmolt egg production (5 to 43 wk) was higher for hens fed the DDGS molt diets than those fed the corn diets. There were no consistent differences in egg mass, egg-specific gravity, feed efficiency, or layer feed consumption among molt treatments for the postmolt period. These results indicate that limit feeding corn diet and DDGS diet in non-feed-withdrawal molt programs will yield long-term postmolt performance that is comparable to that observed by ad libitum feeding a C:SH diet.

The molting of commercial layers has been under increased scrutiny by animal rights groups, who have said that this practice is highly stressful and one which negatively affects the welfare of the hen due to the initial period of fasting that has been used to stop egg production. In recent years, there has been a recognized need to develop practical alternatives to molting layers other than the use of fasting. Thus, the University of Illinois, University of Nebraska, North Carolina State University, and the University of California have all researched this area. In all of these studies, the methods involved comparing a normal fasting method (i.e., 5 to 13 d), to feeding low-energy and protein diets using ingredients such as wheat middlings, soybean hulls, and corn or diets with graded levels of added salt and without salt (University of Nebraska, University of California). The molt period (28 d) included full-feeding of these diets. In these studies, postmolt production performance for the nonfeed withdrawal techniques was comparable to the fasting method. Several researchers have also evaluated the behavioral repertoire of laying hens, which includes feeding, drinking, comfort, social, reproductive, and anti-predator behaviors. In addition, related behaviors such as aggression, escape-avoidance, and submission have been of particular interest as potential indicators of welfare during molting. In these studies, genetic selection, strain, density, or molt program do not appear to adversely influence the behavioral patterns during the molt. The behavior patterns displayed during a molt program appear consistent with the response to physiological changes that layers experience and do not appear to compromise the welfare status of the hens. Appetitive behaviors were not affected by strain but were affected by production phase and molting. Strain or production phase did not influence the frequency of aggressive and submissive acts. Thus, the use of alternative nonfeed withdrawal molting methods provide comparable laying hen well-being and may enhance the transition from a productive to a resting state.

In experiment 1 (one cycle), hens were fed diets containing 0.10, 0.115, 0.125, 0.135, 0.15, or 0.45% available P (AP) from 40 to 56 wk of age, with the last diet being a positive control. Egg production, egg mass, and BW were reduced (P < 0.05) by all lower AP levels except 0.15% AP when compared with the 0.45% AP treatment. In the second experiment (two cycles with a molt), hens were initially fed diets containing 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, or 0.45% AP from 21 to 63 wk of age. Diets containing 0.10, 0.12, and 0.14% AP were terminated at 35, 39, and 50 wk, respectively, due to low egg production and increased mortality. Hens fed 0.16% AP also had significantly lower production performance than hens fed 0.45% AP during the first cycle. Hens on the 0.16 to 0.45% AP treatments were induced molted at 64 wk of age by 10 d of feed removal. The hens were then returned to the same AP layer diet they had been fed from 21 to 63 wk. For the 68 to 108 wk postmolt second-cycle period, hens fed the 0.16 to 0.20% AP diets (166 to 209 mg/d) had significantly lower egg production, egg mass, and feed efficiency than hens fed 0.45% AP. The results of our study indicated that first-cycle hens required approximately 0.18% AP or 198 mg AP/hen per day, and molted hens in their second cycle had a requirement that was greater than 0.20% AP or 209 mg AP/hen per day.

The objective of this study was to evaluate several nonfeed removal methods compared with feed removal for induced molting of laying hens. An experiment was conducted using 576 Dekalb White hens (69 wk of age) randomly assigned to 1 of 8 dietary treatments. Two of these treatments consisted of feed removal for 10 d followed by ad libitum access to a 16% CP, corn-soybean meal diet or a 94% corn diet for 18 d. The other 6 treatments provided ad libitum access for 28 d to diets containing 94% corn, 94% wheat middlings (WM), 71% WM: 23% corn, 47% WM: 47% corn, 95% corn gluten feed, and 94% distillers dried grains with solubles (DDGS). At 28 d, all hens were fed a laying hen diet (16% CP), and production performance was measured for 40 wk. The 2 feed removal treatments resulted in total cessation of egg production within 6 d. Egg production of hens fed the 94% WM, 71% WM: 23% corn, corn, corn gluten feed, and 47% WM: 47% corn diets all decreased to 6% or less by d 12, 16, 19, 20, and 28, respectively. Egg production of hens fed DDGS never decreased below 18%. Body weight loss ranged from 10% (DDGS) to 26% (10-d feed removal), with the other treatments being similar at 17%. No consistent differences were observed among treatments throughout the 40-wk postmolt period for egg production, egg specific gravity, egg weight, egg yield, or feed efficiency. No differences were observed among feed removal treatments versus several nonfeed removal treatments for ovary and oviduct weights and blood heterophil:lymphocyte ratios during the molt period. In addition, interactive social behaviors were not different throughout the molt period between hens fed the 94% WM and those deprived of feed for 10 d. Our results indicate feeding WM, corn, corn gluten feed, and WM:corn diets are effective nonfeed removal methods for molting laying hens.

Four experiments were conducted to evaluate the effects of phosphorus nutrition on laying hens exposed to heat stress (HS). Hens were fed their respective diet for at least 3 wk prior to initiation of each experiment to allow the hens fed low-P diets to become P deficient. In most experiments, hens housed in non-HS conditions were pair-fed to the HS hens to maintain equal feed intake. In experiments 1 and 2, two levels of nonphytate P (NPP; deficient at 0.10 or 0.16% vs. control at 0.45%) and two temperatures (constant thermoneutral at 21 degrees C or cyclic HS up to 35 degrees C) were evaluated. Low NPP significantly reduced feed intake and hen-day egg production, but the cyclic heat treatment had no effect on hen performance. Experiment 3 was similar to experiments 1 and 2 except that constant HS was implemented. Both constant HS and low dietary NPP reduced feed intake and egg production, and there was no significant interaction between HS and dietary NPP level. In experiment 4, hens were fed 0.10 or 0.45% NPP diets and exposed to a more severe HS (38 degrees C) for 8 h. Hens fed the deficient NPP level showed a 16% incidence of severe heat distress (unable to stand, unresponsive). Our results generally indicated that there was no interaction between dietary NPP level and HS in laying hens. However, subjecting hens that had been fed a P-deficient diet to an acute HS of 38 degrees C did increase the incidence of severe heat distress.

Four levels of nonphytate P (NPP; 0.2, 0.3, 0.4, and 0.5%; total P = 0.46, 0.56, 0.66, and 0.76%) and two temperatures (25 and 37 degrees C) were evaluated in chicks from 8 to 22 d. In experiment 1, crossbred male chicks (New Hampshire x Columbian) housed at 25 degrees C increased weight gain at all increasing NPP levels, but chicks exposed to 37 degrees C did not show increased weight gain beyond 0.3% NPP. In experiment 2, environmental temperature was not increased until d 15. Weight gain of crossbred male chicks fed the 0.2% NPP diet was similar at both temperatures, but chicks exposed to 37 degrees C had lower weight gains than chicks housed at 25 degrees C for all other NPP levels. On d 22 to 24, chicks that had been housed at 25 degrees C and fed 0.2, 0.3, and 0.5% NPP were moved to the 37 degrees C chamber to evaluate heat stress on older chicks. Chicks fed the 0.2% NPP diet showed 35% mortality within 6 h. In experiment 3, both male commercial (Ross x Ross) and crossbred chicks that had been housed at 25 degrees C and fed 0.2% NPP from 8 to 22 d showed increased signs of severe heat distress when exposed to 37 degrees C on d 22. Our results suggest that the NPP requirement for growth of 8-to-22-d-old chicks may be reduced by high temperature. However, a NPP deficiency may result in increased mortality or severe heat distress in older chicks that are exposed to an acute increase in temperature.

An experiment was conducted using 336 White Leghorn hens (60 wk of age) randomly assigned to one of four treatments that consisted of feed removal for 4 or 10 d or no feed removal with ad libitum access to 95% corn or 95% wheat middlings molt diets that contained supplemental minerals and vitamins. At the end of the 4- or 10-d feed removal period, hens on these treatments were provided with the corn molt diet for 24 or 18 d, respectively. Hens on the corn or wheat middlings treatments were fed the diets for 28 d. At d 28, hens on all treatments were fed a corn-soybean meal (16% CP) layer diet for 40 wk (64 to 104 wk of age). Both feed removal and the wheat middlings treatments resulted in total cessation of egg production within 8 d. Egg production of hens fed the corn molt diet had decreased to 3% by d 28. Body weight loss for hens fed the corn or wheat middlings diet was approximately 15 and 8% at d 28, respectively. Hens fed the wheat middlings diet returned to production slightly faster than hens on the other treatments. Postmolt egg production and egg mass (wk 5 to 44) were generally higher for the wheat middlings and 10-d feed removal treatments than for the corn or 4-d feed removal treatments. There were no consistent differences in mortality, egg weight, egg specific gravity, feed efficiency, and layer feed consumption among treatments. This research indicates that diets with high corn or wheat middlings, particularly wheat middlings, are effective nonfeed removal methods for molting hens.

We used a total of 504 commercial Single Comb White Leghorn hens (69 and 65 wk of age) in each of two experiments, and hens were induced to molt by feed withdrawal only. Feed withdrawal lasted for 12 and 11 d, and hens lost 26 and 25%, body weight in Experiments 1 and 2, respectively. All hens were then weighed, and seven replicate groups of 12 hens each were assigned to molt diet treatments. In Experiment 1, diets consisted of a corn basal diet (7.9% CP) or corn basal diet supplemented with 7.5 or 10% spent hen meal (SHM) each from two different sources. In Experiment 2, the corn basal diet or this diet supplemented with 5 or 10% SHM alone or 5% SHM plus Met, Lys, and Trp was evaluated. A molt diet of 16% CP corn-soybean meal was used as a positive control in both experiments. Molt diets were fed for 15 d in both experiments, at which time all hens were fed a 16% CP layer diet. Performance was measured for 8 wk following the beginning of feeding the layer diet. Feeding the low-protein corn molt diet supplemented with 5 to 10% SHM improved early postmolt egg production performance and body weight gain compared with hens fed the corn basal diet alone. The 7.5 and 10% SHM diets yielded early postmolt performance that was not significantly different (P > 0.05) from that of hens fed the high-protein (16% CP) diet. Supplementing the 5% SHM diet with amino acids generally did not significantly improve performance. The present study thus indicates that improved early postmolt performance may be achieved by supplementation of a low-protein corn molt diet with 5 to 10% SHM.

Data previously obtained from our laboratory indicated that addition of 300 U of phytase/kg diet supported optimal long-term performance of laying hens (20 to 70 wk) fed a corn-soybean meal (SBM) diet containing 0.10% available phosphorus (AP). Our primary objective was to determine if a phytase level lower than 300 units/kg is adequate for a commercial strain of Single Comb White Leghorn laying hens (n = 504) fed a corn-SBM diet containing no supplemental P (0.10% AP). Dietary treatments consisted of the corn-SBM basal diet (0.10% AP, 3.8% Ca, and 17% CP) supplemented with 0, 100, 200, 250, or 300 U of phytase/kg, 0.05% inorganic P (0.15% AP), and a positive control diet containing 0.45% AP. Each of the seven dietary treatments was fed to six replicate groups of 12 hens from 20 to 60 wk of age. No significant differences in performance were observed among treatments during the first 8 wk of the experiment. By 28 wk of age, the 0.10% AP diet, with no supplemental phytase or P, resulted in significantly lower (P < 0.05) egg production and body weight compared with all other dietary treatments. Feed consumption, feed efficiency, and egg yield were subsequently depressed by 32 wk of age in hens fed the 0.10% AP diet. No other significant differences among treatments were observed for performance averaged over the entire 40-wk experimental period. The mean daily AP intake of hens fed the 0.15% AP, 0.45% AP, and 0.10% AP + phytase diets was 155, 474, and 103 mg, respectively. The results of this study indicate that phytase improves the utilization of P in corn-SBM diets for laying hens and that corn-SBM diets containing 0.10% AP + 100 units of phytase/kg diet or 0.15% AP supported egg production performance that was not significantly different (P > 0.05) from that of hens fed a corn-SBM diet containing 0.45% AP.

In the first of two experiments (20 to 70 wk of age), eight treatments consisted of corn-soybean meal diets (0.34% total P, 3.8% Ca, 17% CP, 2,758 kcal ME/kg) containing 0.10, 0.15, 0.20, 0.25, or 0.45% available P (AP), with the three lowest AP diets supplemented with 300 units of phytase/kg of diet. A second experiment evaluated the effect of feeding the 0.10% AP diet with and without phytase on performance and time required for onset of P deficiency in older hens (70 to 76 wk of age). In Experiment 1, the 0.10% AP diet with no supplemental phytase depressed performance by 28 wk of age. No other significant differences in performance were observed among treatments for the entire 20- to 70-wk period except that the 0.15% AP diet with no phytase resulted in body weights and tibia ash that were lower (P < 0.05) than those of hens fed the 0.45% AP diet during the last 30 wk. The mean daily AP intake of hens fed the 0.10% AP, 0.15% AP, 0.45% AP, or 0.10% AP + phytase diets was 94,159, 499, or 108 mg, respectively. Excreta P concentration was decreased by approximately 50% in birds consuming 0.10% AP + 300 U/kg phytase compared with those consuming 0.45% AP. In the second experiment, P deficiency signs occurred within 3 wk of consuming the unsupplemented corn-soybean meal diet (0.10% AP) compared with 8 wk in Experiment 1. The results of this study indicate that phytase improves P utilization in corn-soybean meal diets for laying hens and that a corn-soybean meal diet containing 0.15% AP (159 mg AP/d) or containing 0.10% AP + 300 units of phytase/kg (108 mg AP/d) supported optimal egg production from 20 to 70 wk of age. Additionally, results suggested that older hens may exhibit P deficiency symptoms sooner than younger hens.

Commercial White Leghorn hens (65, 63, or 70 wk of age in Experiments 1, 2, and 3, respectively) were induced molted by feed withdrawal until approximately 28% body weight was lost. All hens were then weighed, and seven replicate groups of 12 hens each were fed molt diets. In Experiment 1, three diets consisted of a corn basal diet (7.9% CP) or this diet supplemented with corn gluten meal (CGM) and Lys or feather meal (FM), Met, and Lys. In Experiments 2 and 3, varying levels of FM and FM with Met and Lys were evaluated. A 16% CP corn-soybean meal diet was used as a positive control in all experiments. The molt diets were fed for 17, 15, and 17 d in Experiments 1, 2, and 3, respectively, and production performance was measured for 8 wk from the beginning of feeding the layer diet. In all experiments, hens fed the 16% CP corn-soybean meal molt diet returned to egg production and regained body weight at a faster rate than did hens fed any of the other diets. In Experiment 1, early egg production of hens fed the corn basal diet supplemented with CGM and Lys or supplementation with FM, Met, and Lys was greater (P < 0.05) than that of hens fed the basal diet alone. In Experiment 2, very early egg production (Week 1) and body weight gain were lower (P < 0.05) for hens fed the corn basal diet than for hens fed the basal supplemented with FM, Met, and Lys. The addition of 5.75 or 8.5% FM or 5.75% FM plus Met and Lys generally increased (P < 0.05) early egg production and postmolt body weight gain compared to the corn basal diet in Experiment 3. The present study thus indicated that improved early postmolt performance may be achieved by supplementation of a low-protein corn molt diet with various combinations of CGM, FM, Met, and Lys.

An experiment was conducted to determine the effect of acute heat stress exposure on amino acid digestibility in laying hens. A total of 30 commercial laying hens were singly housed in an environmentally controlled facility, fed a standard laying ration, and exposed to a constant thermoneutral temperature (21 C) for 12 d. The hens were then randomly fed one of three diets (10 hens per diet) and exposed to three consecutive temperature periods (8 d each), which consisted of: 1) a constant 21 C temperature, 2) a cycling temperature of 35 C for 12 h and 29 C for 12 h, and 3) a constant 21 C temperature. The three isonitrogenous (18% CP) diets fed were: 1) a corn-soybean meal diet, 2) a corn-soybean meal diet containing 15% meat and bone meal, and 3) a corn-soybean meal diet containing 5% alfalfa meal and 20% wheat bran. Excreta were collected from all hens during the last 4 d of each temperature period and apparent amino acid digestibility was determined. There was a significant diet effect (P < 0.05) on amino acid digestibility. Digestibility of amino acids in Diet 2 (corn-soybean meal/meat and bone meal) was higher (P < 0.05) than in the other two diets. In addition, digestibility of amino acids in Diet 3 (corn-soybean meal/alfalfa meal/wheat bran) was significantly lower (P < 0.05) than in Diets 1 or 2. Heat stress generally had no significant effect on amino acid digestibility except for His and Lys digestibility. Histidine digestibility was higher during the heat stress period than during the initial and recovery thermoneutral periods, whereas Lys digestibility was higher during the heat stress period than during the initial thermoneutral period. These results indicated that acute heat stress (8 d) had no adverse effects on dietary amino acid digestibility in laying hens.

Exposure of laying hens to an acute heat stress period (38 degrees C) produced a decrease (P < or = 0.05) in blood plasma magnesium compared with pre-heat stress (23 degrees C) levels. Blood plasma glucose, alkaline phosphatase, total protein, uric acid and creatinine were not changed (P > or = 0.05) by exposure to 38 degrees C compared with the first 23 degrees C exposure. Inorganic phosphorus, calcium, potassium and sodium levels were not affected by acute heat-stress exposure or carbon dioxide addition. These results suggest that acute heat stress had no dramatic effect on plasma enzymes, metabolites and electrolytes of laying hens.

Exposure to heat stress lowered partial pressure of arterial blood carbon dioxide (paCO2), arterial blood bicarbonate ion (HCO3-), but increased arterial blood pH (pHa) and plasma lactate (LA). Increasing ambient carbon dioxide (CO2) to 1.5% increased paCO2 from hypocapnic levels to normocapnic levels, raised HCO3-, lowered pHa and plasma LA to pre-heat stress levels. Following CO2 treatment, respiratory alkalosis conditions returned. It was evident in this study that increasing ambient chamber CO2 to 1.5% was effective in ameliorating acid-base disturbances and reducing elevated levels of plasma LA which normally develops when laying hens are subjected to an acute heat stress exposure.

An experiment was conducted to determine the effects of providing heat-stressed laying hens with carbonated drinking water on production performance and tibia bone breaking strength. A total of 32 commercial laying hens (89 wk of age) were housed in an environmental chamber and exposed to 1 wk of a constant thermoneutral temperature (21 C), followed by 6 wk of a daily heat stress temperature cycle (34 C for 8 h; 21 C for 16 h). One half of the hens received tap water and the other half were provided carbonated water immediately after housing. Following 6 wk of heat stress temperature exposure, all hens were killed by cervical dislocation and left tibia bone strength measurements were taken. Hen-day egg production, egg weight, egg yield, feed consumption, and feed efficiency did not differ between water treatments; however, egg specific gravity was depressed for hens provided carbonated versus tap drinking water. Left tibia bone breaking strength per 100 g body weight was improved (P < or = .05) for hens provided with carbonated drinking water during exposure to heat stress temperatures. These results suggest that carbonated drinking water may enhance bone integrity by increasing tibia bone breaking strength of older laying hens exposed to a short-term heat stress period.

Two experiments were conducted to examine the effects of varying length of feed withdrawal on postmolt laying hen performance. Commercial laying hens (65 wk of age) were fed continuously or fasted for 4 or 10 days in Experiment 1 and fed continuously or fasted for 4, 7, or 14 days in Experiment 2. Egg production performance was evaluated for 35 wk of production following initiation of fasting. Hen-day egg production (Weeks 1 to 35) and egg weight (Weeks 5 to 35) did not differ between treatments in Experiment 1; however, in Experiment 2, egg production was depressed for the 14-day fasted hens compared with the fed hens. Lower egg weight also occurred for the 14-day fasted hens compared with the fed, 4-, or 7-day fasted hens in Experiment 2. Egg yield (grams of egg per hen per day) for Weeks 5 to 35 was lower for fed hens versus the 4- or 10-day fasted groups in Experiment 1, but no treatment differences occurred in Experiment 2. Feed efficiency (grams of egg per gram of feed) for Weeks 5 to 13 was not affected by length of fasting in Experiment 1, but feed efficiency of hens fasted for 14 days was lower (P less than .05) than that of hens on other treatments in Experiment 2. Egg specific gravity was highest for hens fasted for 10 or 14 days and was lowest for fed hens, with egg specific gravity for hens fasted for 4 or 7 days being intermediate (P less than or equal to .05). The results indicated that fasting periods of less than 10 days may yield satisfactory egg production and egg weight but that eggshell quality may be enhanced by using fasting periods of 10 days or longer.

Three experiments were conducted to evaluate the effects of feeding molt diets varying in protein content and supplemental Met on postmolt layer performance. Laying hens (70, 65, or 96 wk of age) were induced to molt by fasting (feed only) until 26 to 28% body weight loss occurred. Six molt diets consisting of 16, 13, or 10% CP with or without .15% supplemental Met were then fed until egg production reached approximately 10%, at which time all hens received a 16% CP layer diet for 30 wk in Experiments 1 and 2 and for 4 wk in Experiment 3. In Experiment 1 (summer), hens regained body weight more rapidly, returned to production faster, and had larger egg weights (Weeks 1 to 4) when fed the 16 or 13% CP molt diets than when fed the 10% CP molt diet. Long-term egg production, egg yield (grams of egg per hen per day) (Weeks 1 to 30), and feed efficiency (Weeks 1 to 8) were greater for hens fed the 16 or 13% CP molt diets compared with those fed the 10% CP molt diet. The Met supplementation had no effect on postmolt performance. In Experiment 2 (winter), the only significant treatment effect was that Met supplementation increased egg weight (Weeks 1 to 30). Molt diet treatments had no consistent effect on egg specific gravity during the last 4 wk of the postmolt production period in Experiments 1 or 2. The effects of the dietary treatments on early postmolt performance in Experiment 3 (early fall) were similar to those observed in Experiment 1. The present study indicated that protein content, but not Met supplementation, in molt diets influenced postmolt performance of hens during the summer and early fall experiments, but not in the winter experiment.

A study was conducted to determine whether water-cooled floor perches would be utilized by commercial broilers exposed to a constant hot ambient environment; and subsequently, whether utilization of these perches would improve performance beyond those provided uncooled floor perches. A total of 330 day-old commercial broiler chicks were randomly allocated to six pens (2.44 m2) in an environmentally controlled facility and maintained in a thermoneutral brooding environment for 16 days. Following this period, 240 birds were selected on a body weight basis and randomly assigned to the six pens. A perch constructed from steel pipe (2.44 m length, 5.0 cm diameter) was then placed diagonally on the litter covered floor of each pen. The birds were first exposed to a thermoneutral period (27.7 C), during which time cooling of the perches in three replicate pens was initiated by circulating tap water. The other three experimental pens received ambient perches. Ambient temperature was then raised to 32.6 C for the following 4 wk. The results of the present study showed that utilization of water-cooled perches by broilers was greater (P less than or equal to .01) than ambient perch utilization throughout the 32.6 C period. Average daily gain was greatest (P less than or equal to .01) for broilers exposed to cool perches. Additionally, they consume more feed (P less than or equal to .05), on a daily basis, than those given ambient perches during the heat-stress period. Broilers exposed to water-cooled perches also had a more efficient gain to feed ratio (P less than or equal to .01). At the completion of the study, final body weight and total body weight gain were greater (P less than or equal to .05) for broilers given water-cooled perches compared with those exposed to ambient perches. Total amount of feed consumed and total feed efficiency were only moderately affected (P less than or equal to .10) by perch treatments. These results indicated that water-cooled perches were beneficial in improving broiler performance during periods of high environmental temperatures.

An experiment was conducted with laying hens to determine effects of feeding excesses of several individual amino acids in a practical layer diet. Single Comb White Leghorn hens, which were in peak production (31 wk of age), were assigned to one of five dietary treatments: a 16% CP corn and soybean meal positive control diet, or this diet fortified with 1% additional L-Lys, 1% additional DL-Met, 1% additional L-Thr, or 1% additional L-Trp. The diets were fed for ad libitum intake for 4 consecutive wk of production. For the entire production period, hen-day egg production, egg yield, and feed intake were not significantly different among any of the treatments. The study indicated that considerable tolerance exists in high-producing laying hens for individual excesses of the amino acids commonly used as supplements in poultry diets.

Three experiments were conducted to evaluate the effects of sodium aluminosilicate (SAS) on performance of chicks and laying hens fed diets varying in nonphytate P (NPP), phytate, and fiber content. In two chick growth experiments a corn and soybean meal diet and a phytate and fiber-free casein-dextrose diet were used. These diets contained .1% NPP and 1.1% Ca and were fortified with 0, .05, or .10% P from KH2PO4 and 0 or .5% SAS. A 3 x 2 factorial arrangement of treatments was used. Sodium aluminosilicate supplementation significantly (P less than .05) depressed growth of chicks fed the corn and soybean meal diets containing 0 or .05% supplemental AP. Sodium aluminosilicate addition decreased (P less than .05) tibia ash and total tibia P (tibia weight x P concentration) in both chick experiments, with the effect being greater for chicks fed the corn and soybean meal diet. In the laying hen experiment, birds were fed corn and soybean meal diets containing NPP levels of .1, .45, or 1.8% and SAS levels of 0 or 1.0%. Egg production and egg yield were depressed (P less than .05) by feeding diets containing .1 or 1.8% NPP, and egg specific gravity was decreased (P less than .05) by feeding 1.8% NPP. Addition of SAS to the .1% NPP diet caused a large reduction (P less than .05) in egg production, egg weight, and feed efficiency, whereas SAS supplementation of the 1.8% NPP diet had no significant effect. Sodium aluminosilicate supplementation increased (P less than .05) egg specific gravity for hens fed the .1 and 1.8% NPP diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Production, physiological, and behavioral data were collected simultaneously on commercial hens housed for 10 months of lay in housing alternatives of cages, deep litter floor pens, and outside range pens. Treatments consisted of housing 1, 2, or 3 hens in small cages 3, 4, 5, or 6 hens in large cages, floor pens housing 51 hens each at three densities, and range pens with 50 hens at .74 m2 (8 ft2) per hen. Egg production rates were greater for all caged hen treatments than for any floor or range groups. Egg numbers favored 2 hens per cage, but economic benefits favored 5 hens per cage. Viability was highest for 1 hen per cage and range pen groups. Feed efficiency was poorer in floor and range groups; however, body weight was generally greater for caged hens. Plasma corticosterone levels did not differ among any cage or range groups, but floor pen hens had significantly elevated levels. Behavioral data for walking and object pecking showed clear differences between cage and floor management alternatives. Preening, standing, and drinking activities were different between some treatments but not clearly different between management alternatives. Feeding activity did not differ among any groups. Although correlations between stress and well-being have not been well elucidated, the sum of the stressors of cage confinement appeared to be less than those from floor pens. Therefore, it was concluded that the well-being of hens in cages was equal to or better than that for free ranging hens or those in floor pens.

Plasma corticosterone was measured as a stress indicator of laying hens in different management conditions. Laying hens housed in cages and floor pens were sampled repeatedly in the morning and the afternoon. Plasma corticosterone concentrations of afternoon samples of hens from floor treatments were significantly higher than those from cage treatments, but morning values were not different. These results suggest that management systems, producing subtle adverse conditions for laying hens, are associated with elevated baseline corticosterone levels during the nadir of the diurnal response, whereas peak values may not be affected.

To compare the effects of using continuous (C) vs. intermittent (I) photoperiods with normal (24 hr) and a long but decreasing light-dark cycle (LDLDC) on production performance and egg quality, 240 White Leghorn hens of the University of Missouri-Columbia strain were individually caged in light-controlled rooms. Treatments applied at 21 weeks of age were light-dark cycles (LDC) of 25 hr gradually reduced to 23.5 hr with C or I photoperiods, and 24-hr LDC (controls); C or I photoperiods were gradually increased from 13.75 to 16 hr for the 25- to 23.5-hr LDC, and from 13.75 to 15 hr for the 24-hr LDC. Data were obtained on hen-day egg production, egg weight, egg mass, egg specific gravity, Haugh units, feed consumption, and feed efficiency. Hen-day egg production was significantly greater (P less than .01) for the combined C photoperiod treatments, while hens consumed significantly less (P less than .05) feed exposed to the combined I photoperiod treatments. Egg specific gravity was significantly better (P less than .05) for the LDLDC vs. the 24-hr LDC program with the difference being attributed to an increase (P less than .05) in initial egg specific gravity with the use of a 24-hr LDC. Egg weight, egg mass, Haugh units, and feed efficiency were not affected (P greater than .05) by LDC or photoperiod treatments.

Responses of commercial laying hens to 16 management systems were examined for 10 laying periods of 28 days each. Twelve cage treatments consisted of housing three, four, or five hens in deep and shallow cages of different dimensions which provided .035 and .046 m2/hen. Four floor treatments housed 35 hens or 32 hens and three roosters at densities of .094 or .373 m2/bird, in two replicated pens each. Quantitative data were collected simultaneously for 23 production, physiological, and behavioral characteristics throughout the study. When comparing all caged with floor pen hens, caged hens had better (P less than .05) egg production rates (76.3 vs. 73.9%), gained more weight, had better feed efficiency, and had greater egg and egg shell weights than floor hens. All floor pen hens had higher (P less than .01) viability (98.9 vs. 95.0%), higher (P less than .01) plasma corticosterone levels (595.0 vs. 445.4 pg/ml), a greater (P less than .01) response to adrenocorticotropin (ACTH) challenges, and lower (P less than .01) antibody titers to Salmonella pullorum challenges than all caged hens. Caged hens preened, stood, crouched, and feather pecked more than floor hens, while floor hens drank and moved about more than caged hens. This study attempted to quantify production, physiological, and behavioral traits, all on the same flock of hens, in order to separate stressful from nonstressful management environments. Integration of all measurements indicates that properly managed caged hens were subjected to significantly fewer stressors than laying hens housed in floor pens, although the hens' well-being in the two environments could not be quantitatively compared.