The influence of dietary sodium chloride, arginine:lysine ratio, and methionine source on apparent ileal digestibility of arginine and lysine in acutely heat-stressed broilers.

The present study was carried out to determine the ileal digestibility of Arg and Lys in acutely heat-stressed broilers using diets varying in Arg:Lys ratio, NaCl concentration, and Met Source. Male broilers were maintained at 22 degrees C from 21 to 33 d of age and then at 32 degrees C from 33 to 38 d of age. From 28 to 38 d of age, birds were fed a diet with an Arg:Lys ratio of 1.05 and 3 g of supplemental NaCl/kg of diet with or without L-arg free base to increase the Arg:Lys to 1.35, and with or without 3 g/kg of additional NaCl. Methionine was supplied as equimolar amounts of DL-Met or 2-hydroxy-4-(methylthio)-butanoic acid in a 2 x 2 x 2 design. At 38 d of age, digesta were collected from the terminal ileum, and amino acid analyses were conducted on feed and digesta samples and compared with acid-insoluble ash (dietary celite) to calculate the apparent ileal digestibilities of Lys and Arg. Increasing the NaCl concentration and the presence of HMB significantly decreased the digestibility of both Arg and Lys, whereas increasing the Arg:Lys ratio increased the digestibility of only Arg but did increase BW gain (P = 0.08). An interaction between dietary NaCl and Arg:Lys ratio as well as the 3-way interaction suggested that dietary NaCl could affect the apparent ileal digestibility of Arg and Lys at certain Arg:Lys ratios and the response may be influenced by the Met source.

Challenges of accurately defining the nutrient requirements of heat-stressed poultry.

The number of factors that influence the nutrient requirements of heat-stressed poultry, through alterations in metabolism and biological responses, are much greater than those that influence the nutrient requirements of poultry at thermoneutral temperatures. Therefore, multiple dietary nutrient specifications adjusted for different intensities of heat stress experienced in different geographical locations, and for different management options used to combat such conditions, are likely to be required by poultry nutritionists. Financial constraints on the construction of suitable research facilities have limited the accumulation of knowledge concerning dietary nutrient specifications for heat-stressed poultry. Thus, input from commercial enterprises has contributed significantly to the accumulation of existing knowledge. Knowledge of the energy and amino acid requirements of birds during heat stress are best known, whereas vitamins and trace minerals remain among the least-researched groups of nutrients.

The influence of drinking water containing sodium chloride on performance and eggshell quality of a modern, colored layer strain.

Hubbard ISA IsaBrown pullets were purchased from a commercial supplier at 16 wk of age and kept at a constant 18 C or a constant 30 C in temperature-controlled rooms. The purpose of our experiment was to determine the effect of ambient temperature on the eggshell quality responses of laying hens receiving saline drinking water with or without simultaneous supplementation of the diet with ascorbic acid or Zn methionine. Four treatments were investigated: 1) a basal layer diet (C) and local drinking water, 2) diet C and local drinking water containing 2 g NaCl/L, 3) diet C containing 200 mg ascorbic acid/kg and local drinking water containing 2 g NaCl/L, and 4) diet C with 360 mg Zinpro 100 (Zn methionine)/kg and local drinking water containing 2 g NaCl/L. The local drinking water contained <1 mmol Cl/ L. The pullets received a continuous daily photoperiod of 16 h from fluorescent lighting, and production measures were made between 20 and 60 wk of age. Production and eggshell quality were significantly reduced at 30 C compared with 18 C but were not significantly affected by the dietary and water treatments. The results indicated that the IsaBrown hens were relatively insensitive to intakes of NaCl from the drinking water at concentrations of 2 g/L. This lack of sensitivity in eggshell quality contrasts with the majority of published reports, including earlier work with local Australian layer strains. It is suggested that this contrasting sensitivity may relate to the concentration of dietary NaCl used during the selection of layer genotypes.

Sodium bicarbonate and potassium bicarbonate supplements for broilers can cause poor performance at high temperatures.

1. Supplements of between 2 and 8 g of sodium bicarbonate (NaHCO3)/l in drinking water provided between 21 and 49 d of age to broilers at 31 degrees C increased growth after 35 d of age and food intake after 42 d of age compared to unsupplemented controls. The most consistent responses were observed with 2 g NaHCO3/l. 2. Differences in weekly water intakes with different concentrations of NaHCO3 in the drinking water did not equate with variations in weekly food intake and growth. 3. Unexpected high mortality from dehydration and nephrosis was observed with a 10 g NaHCO3/l supplement. This mortality was associated with major changes in blood acid-base balance and plasma electrolyte concentrations. 4. Dietary supplements of NaHCO3 gave significantly better food conversion and numerically better growth in broilers at 31 degrees C than supplements of potassium bicarbonate (KHCO3) providing similar dietary concentrations of bicarbonate. 5. Supplements of NaHCO3 were more toxic to broiler chickens when supplied in the drinking water than in the diet. This appeared to be related to the intake of sodium and alterations to cellular membrane ionic potential.

Optimum dietary arginine:lysine ratio for broiler chickens is altered during heat stress in association with changes in intestinal uptake and dietary sodium chloride.

1. The effects of varying the dietary arginine:lysine (Arg:Lys) ratio for broiler chickens at thermoneutral and high temperatures was studied in a series of 5 experiments which measured intestinal epithelial transport or evaluated growth and food efficiency with practical diets or diets supplemented with L-arginine free base. 2. The growth studies showed that increasing the Arg:Lys ratio at high temperatures produced consistent improvements in food conversion without any loss in growth. 3. Increasing dietary sodium chloride concentration reduced the Arg:Lys ratio necessary for optimum food conversion. 4. Food conversion responses were improved whether L-arginine free base was used as a dietary supplement in place of an inert filler or practical diets with differing ingredients were used to vary the Arg:Lys ratio. 5. In the presence of an equimolar concentration of lysine the uptake of arginine by the intestinal epithelium of heat-stressed broilers was reduced significantly compared with that of broilers at thermoneutral temperatures. 6. The results indicate that the ideal amino acid balance for broilers varies with ambient temperature.

Improving eggshell quality at high temperatures with dietary sodium bicarbonate.

Two experiments were conducted that confirmed the hypothesis that a dietary bicarbonate supplement will improve eggshell quality in hens at high temperatures as long as feed is consumed during the period of eggshell formation. End-of-lay hens were maintained on continuous light at temperatures of 30 and 35 C. Individual egg weights and shell quality measures for each hen were calculated as a proportion of the initial values determined during an acclimatization period at 25 C. Improvements in shell breaking strength in both experiments were observed as a result of supplementing control diets with 1% sodium bicarbonate (NaHCO3). This response to NaHCO3 was not a reflection of a reduced rate of lay or egg mass output, as these were similar or inferior on the control diets. Similar feed intakes on the control and NaHCO3 diets indicated that the response was not related to differences in calcium intakes. Supplements of zinc methionine and ascorbic acid proved to be inferior to NaHCO3. Improvements in egg weight were associated with the introduction of continuous lighting.

Influence of temperature during growth on responses of hens to high or low temperatures during lay.

1. Commercial pullets were grown at cool (10 degrees -20 degrees C) or hot (25 degrees -35 degrees C) temperatures to similar bodyweights at 18 weeks of age. Between 18 and 50 weeks the birds were either kept at the same temperatures as during growth or transferred to the alternate temperature. 2. Birds kept at the cool temperatures throughout life ate most food and gave the best production during lay. Minimum food intake and poorest performance were obtained with birds kept at the hot temperatures throughout life. 3. Performance in the hot environment during lay was improved by rearing birds in the cool environment, the response being related to an increased food intake. Food intake in the cool environment during lay was reduced, with only minor effects on performance, in birds which had been reared in the hot environment. 4. The results of the present study show that production responses during lay are affected by the temperatures experienced by hens during both growth and lay.

Phosphorus requirements of laying hens fed on wheat-based diets.

1. Three experiments were carried out to determine the phosphorus (P) requirements of laying hens aged 34 to 58 weeks (experiment 1), 59 to 70 weeks (experiment 2) and 22 to 50 weeks (experiment 3) given diets containing wheat, sorghum and soyabean meals as the main ingredients. Dietary total P (Pt) varied between 3.2 and 7.3 g/kg (experiment 1), 3.2 and 4.6 g/kg (experiment 2) and 3.0 and 6.6 g/kg (experiment 3). Hens were housed at either 18 degrees or 30 degrees C (experiments 1 and 2) and uncontrolled temperature (experiment 3), and in experiment 2 diets were fed without or with a phytase supplement of 500 units/g. 2. Dietary Pt had no significant effect on production measures in any experiment. Increases in dietary Pt adversely influenced egg shell quality although uterine calcium (Ca), ATPase and carbonic anhydrase activities were unaffected. 3. A 3-d-feeding trial in experiment 1 gave maximum Pt retentions of 228 mg/d at 18 degrees C and 204 mg/d at 30 degrees C. These were obtained with diets containing, respectively, 4.6 and 6.0 g Pt/kg. 4. Plasma inorganic P (Pi) increased consistently with increases in dietary Pt at all temperatures but plasma total Ca, and tibia Ca and P, were unaffected. 5. The inclusion of the phytase supplement in diets containing 3.2 and 4.6 g Pt/kg had an adverse effect on egg production at both temperatures in experiment 2. 6. A dietary Pt concentration of 3.2 g/kg, providing a calculated 1.2 g available P (Pav)/kg, with a dietary phytase activity of less than 200 units/kg, satisfied the P requirements of the hens used in these studies. However, the data from experiment 3 suggest that the Pt requirement of some flocks fed on wheat-based diets may be lower than 3.2 g/kg.

Effects of dietary mineral supplementation on the performance and mineral retentions of broilers at high ambient temperatures.

1. The relationship between broiler performance and two dietary mineral balance equations was investigated at a high constant ambient temperature (30 degrees C) using a range of 11 salt supplements given to male broiler chicks from 21 to 42 d of age. 2. No relationship was found between broiler performance and either of the two balance equations. 3. Re-evaluating these equations using retained, rather than dietary, mineral concentrations did not improve the relationship although changes in mineral retentions associated with the supplements indicated that dietary concentrations were not a good indicator of the impact of the diet on the bird's acid-base homoeostasis. 4. Evidence was found that metabolisable anions supplemented in association with mineral cations may have a significant effect on broiler performance.

Research note: responses of laying hens on saline drinking water to dietary supplementation with various zinc compounds.

Production variables, eggshell defects, eggshell quality, the concentration of calcium-binding protein (CaBP), and the activity of carbonic anhydrase (CA) in the shell gland mucosa were determined in hens receiving town water (10 mg Na/L), or town water supplemented with 2 g NaCl/L (796 mg Na/L). Five treatments were examined. Control hens received town water and a proprietary layer mash containing .17% Na. The remaining four treatments received the water containing NaCl (2 g/L). Hens of Treatment 2 were fed the proprietary layer mash and those of Treatments 3, 4, and 5 received, respectively, the layer mash containing supplements of Zn-methionine (Zinpro-200; .5 g/kg), Zn sulfate (ZnSO4.7H2O; .46 g/kg), or chelated Zn-EDTA (.54 g/kg) to supply the same concentration of Zn (.1 g/kg). The treatments were applied for 6 wk. Hens receiving the saline drinking water without any dietary Zn supplement produced significantly (P < .05) more eggs with shell defects than hens receiving the town water. This increase in the incidence of eggshell defects was associated with significant reductions in eggshell breaking strength, the concentration of CaBP, and the activity of CA. Supplementing the saline drinking water with any of the three Zn compounds significantly reduced the incidence of eggshell defects and in some cases improved shell breaking strength, the concentration of CaBP, and the activity of CA.

Calcium and carbonate supply in the shell gland of hens laying eggs with strong and weak shells and during and after a rest from lay.

The concentration of calcium-binding protein (CaBP) and the activities of calcium adenosine triphosphatase (Ca(2+)-ATPase) and carbonic anhydrase (CA) were determined in the shell gland mucosa of hens in two experiments. In Experiment 1, laying hens on a proprietary layer mash were compared with hens rested from lay by the feeding of whole grain barley. In Experiment 2 comparisons were made of laying hens fed the proprietary layer mash and producing eggs with either strong or weak shells. These latter comparisons were also made when the shell gland was quiescent or active with respect to daily eggshell formation. Feeding whole grain barley reduced egg production to zero after 11 days. This reduction in rate of lay was accompanied by significant reductions in all three markers, the effect on Ca(2+)-ATPase and CaBP being less than for CA. Control values were regained between 10 and 16 days after the barley was replaced with the layer mash. Relative shell strength and the physiological status of the shell gland with respect to time of daily eggshell formation had no significant effect on any marker in Experiment 2.

Dietary zinc methionine effect on eggshell quality of hens drinking saline water.

In two experiments individually caged 60-wk-old laying hens were exposed to daily temperatures ranging between 18 and 35 C and given various dietary and drinking water treatments. In Experiment 1 these were: 1) basal diet and town water; 2) basal diet and town water supplemented with 2 g NaCl/L; 3) basal diet supplemented with .2 g zinc methionine (Zinpro-200)/kg diet and town water; or 4) basal diet supplemented with .2 g zinc methionine/kg and town water supplemented with 2 g NaCl/L. In Experiment 2, Treatments 1 and 2 were the same as in Experiment 1. Birds on Treatments 3 and 4 received the town water supplemented with 2 g NaCl/L and the basal diet supplemented with either .5 g zinc methionine/kg (Treatment 3) or .28 g ZnSO4H2O/kg to approximate the same dietary zinc concentration in Treatment 3 (Treatment 4). In both experiments, dietary zinc methionine plus 2 g NaCl/L in the drinking water significantly improved shell breaking strength over those birds on the 2 g NaCl/L with no zinc methionine supplementation. This same pattern occurred for shell weight, shell weight per unit of surface area, and percentage of shell defects. There were no improvements in the parameters measured from the supplementation of ZnSO4. The zinc methionine compound apparently was effective in overcoming the negative influence of the added 2 g NaCl/L of town water.

Influence of temperature, dietary energy, nutrient concentration and self-selection feeding on the retention of dietary energy, protein and calcium by sexually-maturing egg-laying pullets.

1. On a daily temperature cycle of 25 to 35 degrees C and during the onset of lay, gross energy in droppings were increased significantly by 3 to 5%. There were no changes in energy metabolisability. Overall, less energy was excreted and energy metabolisability was improved on higher energy diets. 2. Crude protein and calcium losses decreased and their retention efficiencies increased with the onset of lay. Less protein and calcium were lost at the high temperature with corresponding increases in retention. Less protein and more calcium were lost on the higher energy diet. 3. Crude protein excretion was increased and calcium excretion reduced with self-selection feeding. Energy metabolisability and crude protein retention efficiency were reduced by this feeding practice.

Reproductive performance of artificially inseminated hens receiving saline drinking water.

Laying hens were selected at random and placed in individual cages in a commercial type layer shed. One hundred hens received town water and one hundred received town water supplemented with 2 g NaCl/L. Half the hens on each water treatment were inseminated every 7 days with mixed semen collected from six cockerels of a commercial table egg strain maintained on town water. The remaining hens were inseminated with semen from six cockerels receiving town water supplemented with 2 g NaCl/L. Eggs were collected and stored at 12 C over a 7-day period before eggs with defective shells were identified and removed. All remaining eggs were incubated and candled at 7 and 18 days of incubation to detect infertile eggs and embryonic deaths. Data from six consecutive hatches were analyzed. The incidence of eggs with defective shells doubled in hens receiving the saline drinking water. These hens had a significantly (twofold) higher incidence of embryonic deaths and a significantly lower (13%) hatchability of fertile eggs. For every 100 eggs laid the numbers of settable eggs and chicks hatched were significantly reduced in hens receiving the saline drinking water. The saline water reduced the numbers hatched by 20% for every 100 eggs laid. The water treatment given to the cockerels had little effect on reproductive performance.

Use of ascorbic acid to prevent the decline in eggshell quality observed with saline drinking water.

Three experiments were carried out to determine the value of ascorbic acid in overcoming the poor eggshell quality problem associated with the use of saline drinking water. Laying hens were supplied with either town water or town water supplemented with NaCl, ascorbic acid, or a combination of NaCl and ascorbic acid. Supplementing the drinking water lf laying hens with NaCl (2 g/L) significantly increased the incidence of eggshell defects and significantly decreased eggshell quality. Simultaneous supplementation of the saline drinking water with ascorbic acid (1 g/L) prevented these detrimental effects. This response to ascorbic acid was dependent upon concentration. Ascorbic acid acted as a preventive rather than a remedial treatment: hens producing eggs with defective shells as a result of receiving saline drinking water failed to show any improvement in eggshell quality or any reduction in the incidence of eggshell defects when the saline water was supplemented with ascorbic acid.

Egg shell quality responses of pullets given saline drinking water at different ages.

1. Saline drinking water given to pullets before sexual maturity had no effect on their subsequent egg shell quality. 2. Hens receiving saline drinking water from or after laying their first egg produced significantly more egg shell defects than hens receiving town water. 3. The production of eggs with defective shells occurred more rapidly when saline drinking water was given to 40-week-old hens than to hens during the first few weeks of lay. 4. The high incidence of egg shell defects resulting from the use of saline drinking water was reduced to control levels when hens in early lay were given town water for 5 weeks. This response was not observed with 40-week-old hens.

Responses in egg shell quality to sodium chloride supplementation of the diet and/or drinking water.

1. Supplementing the drinking water of 50-week-old laying hens with sodium chloride (NaCl) concentrations between 0.5 and 2 g/l for 7 weeks significantly increased the incidence of egg shell defects and significantly decreased egg shell quality. Dietary NaCl concentrations between 0 and 2 g/kg had little effect on this response. 2. At similar total NaCl intakes egg shell defects were much greater when the NaCl was obtained from the drinking water rather than from the diet. 3. Hens producing eggs with defective shells as a result of receiving saline drinking water failed to recover the ability to lay eggs with good shells after 8 weeks on normal water. 4. The increased incidence of shell damage was not related to decreased food intake or increased egg weight or production.

Responses of sexually-maturing pullets to self-selection feeding under different temperature and lighting regimens.

1. Pullets allowed to self-select nutrients from a protein concentrate and either a separate complete diet or cereal-based, energy-rich mixture showed preferences for protein and energy which varied in relation to the time of their onset of lay. 2. The selected protein:metabolisable energy (ME) intake ratio increased from 14 g protein per MJ of ME 2 to 3 weeks before sexual maturity to approximately 19 g protein per MJ of ME at and after sexual maturity. 3. This response to self-selection feeding was consistent with different temperatures, lighting patterns and dietary manipulations. 4. Egg mass output was improved by self-selection feeding at hot (25 degrees to 35 degrees C) temperatures in experiments 1 and 2 and at ambient temperatures in experiment 3. No beneficial response in egg mass from self-selection feeding was observed at cold (6 degrees to 16 degrees C) temperatures in experiment 1. 5. Providing 2 h of additional light during the dark (cool) part of the day, with or without 2 h of darkness in the middle of the extended light (hot) period, had no effect on the egg mass output of pullets at hot (25 degrees to 35 degrees C) temperatures.

Physiological changes associated with the production of defective egg-shells by hens receiving sodium chloride in the drinking water.

1. Supplementing the drinking water of laying hens with 600 or 2000 mg sodium chloride/l induced large increases in egg-shell defects without corresponding changes in egg production, egg weight or food and water intakes. A supplement of 2000 mg NaCl/l resulted in a high incidence of shell-less eggs. 2. The increased incidence of egg-shell damage in hens receiving the NaCl was associated with a decrease in egg-shell quality measured objectively. These responses persisted even after the NaCl was removed from the drinking water. 3. The NaCl treatment had little effect on blood acid-base balance and electrolytes, but significant reductions were observed in the carbon dioxide tension, and bicarbonate and calcium concentrations in the fluid surrounding the egg in the shell gland. 4. The poor shell quality appeared to be associated with a reduced supply of bicarbonate, rather than with an effect on Ca, in the lumen of the shell gland, although a reduced residence time of eggs in the shell gland may also have contributed to the problem.

Influence of dietary energy, nutrient density and environmental temperature on pullet performance in early lay.

1. Alterations in dietary metabolisable energy (ME) concentration had a limited influence on food and nutrient intakes and egg mass output of hens in early lay kept at the prevailing air (10 degrees to 24 degrees C), cold (6 degrees to 16 degrees C) or hot (25 degrees to 35 degrees C) temperatures. 2. Energy intakes were not improved by increasing the dietary concentrations of nutrients other than energy. 3. At prevailing air and cold temperatures all dietary ME-nutrient density combinations allowed hens to meet the recommended daily protein intake but only hens fed the most concentrated diets were able to meet this recommendation at hot temperatures. 4. Even the highest intakes of ME and protein achieved at hot temperatures failed to increase egg mass output to the values attained on any diet at cold temperatures.