The effects of a quillaja and yucca combination on performance and carcass traits of coccidia-vaccinated broilers exposed to an enteric disease challenge.

A series of 6 floor pen trials was conducted to determine the effects of a quillaja and yucca combination product on the performance and carcass traits of growing broiler chickens vaccinated for coccidiosis at the hatchery. In each of the trials graded levels (0, 250, and 500 ppm) of a quillaja and yucca combination (QY) were fed to Ross 708 broilers for the duration of each 42 d test. Trials were arranged in completely randomized block designs involving a minimum of 11 blocks per trial. At the start of each trial, pens contained 55 broilers. In order to provide each bird with an enteric disease challenge, 5 kg commercial broiler litter containing 104 CFU Clostridium perfringens per gram was placed in each pen. In addition, the sporulated oocysts of Eimeria acervulina and E. maxima were added to each pen at the outset of each test. At d 21 of the trials, coccidial lesion scores, mortality and performance were determined; final performance and total mortality were assessed at 42 d. At the completion of each test, 10 birds of average body weight per pen were selected for carcass evaluations; whole and chilled carcass yield were determined, and pre- and post-chill breast measurements were made. A combined analysis of the results of the 6 trials (75 replications per treatment) was used to determine treatment effects and each variable was assessed by linear regression analysis. Results indicated that QY significantly reduced mortality and coccidial lesions scores at d 21 (P < 0.05). Performance was significantly improved by both levels of QY at 21 and 42 d, and significant linear effects were observed for these variables (P < 0.05). All carcass characteristics were significantly improved by QY administration and significant linear responses were observed for each carcass variable (P < 0.05). These results indicate that by reducing intestinal disease challenge, QY provided linear improvements in performance. In addition, QY positively affected carcass parameters as each variable responded linearly to QY feeding (P < 0.05).

Concurrent use of saponins and live coccidiosis vaccines: the influence of a quillaja and yucca combination on anticoccidial effects and performance results of coccidia-vaccinated broilers.

A series of studies was conducted to determine the effects of a quillaja and yucca (saponin) combination (QY) product on postvaccination oocyst production, development of coccidial immunity, and final bird performance of broilers administered live coccidiosis vaccines. In all, 3 groups of tests were carried out. Study 1 evaluated the effects of QY (0 and 250 ppm) on oocyst per gram of feces (OPG) following vaccination at day-of-age; OPG were measured from 5 to 12 d postvaccination. Study 2 determined the effects of QY (250 ppm) in the presence of 3 commercial coccidiosis vaccines in floor pens. OPG were measured weekly for birds receiving each vaccine and for each corresponding vaccine group fed QY. To determine whether QY influenced the development of coccidial immunity induced by the 3 vaccines, 5 birds were removed from each pen at 28 d and challenged with pathogenic levels of Eimeria spp. At 6 d post challenge, lesion scores were used to evaluate the effects of QY on immune protection provided by each vaccine. In addition, comparisons of final bird performance were made between birds given each vaccine and their corresponding vaccinates fed QY. Study 3 comprised a meta-analysis of 15 floor pen trials in which 21- and 42-d body weight, feed conversions, and total mortality were compared between coccidiosis-vaccinated broilers and similarly vaccinated broilers fed QY (250 ppm). Results of these experiments indicated that feeding QY to vaccinated broilers did not significantly affect OPG from days 5 through 12 postvaccination (P > 0.05). For each vaccine tested in study 2, OPG values were the highest at 14 and 21 d postvaccination. QY significantly reduced OPG at 14 d postvaccination for 2 of the vaccines tested, and produced a similar effect in 1 vaccine at 21 d postvaccination. The remaining vaccine was not affected by QY in the postvaccination OPG results. Despite these changes in OPG, significant differences in lesion scores following the Eimeria challenge were not observed for any vaccinated groups receiving QY. Irrespective of the vaccine, both interim and final feed conversion values were significantly improved when QY was fed (P < 0.01). Similarly, results of a 15-trial meta-analysis indicated that QY-fed vaccinated broilers had higher body weights, improved feed conversions, and lower mortality than their vaccinated controls. Results show that while QY may induce changes in OPG following vaccination, coccidia-vaccinated broilers fed QY develop immunity equivalent to that of controls and show significant improvements in performance and mortality.

Effect of mannan-endo-1,4-beta-mannosidase on the growth performance of turkeys fed diets containing 44 and 48% crude protein soybean meal.

Soybean meal (SBM) contains heat-resistant mannans. Domesticated turkeys are sensitive to mannans because of the high inclusion rate of SBM in their diets, causing increased chyme viscosity, wet droppings, and reduced feed conversion. Three experiments of similar design were conducted to determine the effect of mannan-endo-1,4-f'-mannosidase supplementation of corn-SBM diets on market turkeys. Experiment 1 was conducted at North Carolina State University using Nicholas hens raised from 1 to 98 d of age. Experiments 2 and 3 were conducted at PARC Institute Inc. using Large White turkey toms raised from 1 to 126 d of age. In each experiment, birds were randomly assigned to litter floor pens. Each pen was assigned to one of four experimental treatments in 2 x 2 factorial arrangement of two basal diets containing 44% CP and 48% CP SBM (SBM-44 and SBM-48, respectively) with or without 100 million units (MU) Hemicell/tonne (1 MU = 106 enzyme activity U). Birds fed SBM-44 had lower final BW (14.9 vs. 14.56 kg 18 wk BW / tom; 7.66 vs. 7.46 kg 14 wk BW/hen, P < 0.05) and higher final cumulative feed/gain than those fed the SBM-48. Hemicell supplementation generally improved performance of all birds, with a greater response in birds fed SBM-44. Hemicell improved BW and feed/gain by 1% (P = 0.779) and 3% (P = 0.377) in hens and 2.5% (P = 0.0016) and 4% (P = 0.0001) in toms, respectively. The results of these experiments indicate that some of the adverse effects of antinutritional factors of SBM of on turkey growth performance can be alleviated by dietary mannan-endo-1,4-beta-mannosidase supplementation.

Safety of 25-hydroxyvitamin D3 as a source of vitamin D3 in layer poultry feed.

A target animal safety study investigated the effects of providing 25-hydroxyvitamin D3 (25-OH-D3) in laying hen feed at levels ranging from 0.5 to 10 times the level commonly used for vitamin D3 supplementation in the poultry industry. Following a 28-day preconditioning period, 5 groups of laying hens were fed commercial diets containing 68.9 micrograms of vitamin D3/kg feed (control) or 41.25 (0.5x), 82.5 (1x), 412.5 (5x), or 825 (10x) micrograms of 25-OH-D3/kg feed. The study compared the effects of the control level of vitamin D3 and the various test levels of 25-OH-D3 on health, performance, hematology, and 25-OH-D3 tissue concentrations in laying hens from 0 to 112 d of treatment and on health, performance, gross pathology and histopathology from 113 to 224 d of treatment. Gross pathologic and histopathologic examination of selected tissues after 224 d revealed no lesions attributable to vitamin D toxicity at any level of test material. Concentrations of 25-OH-D3 in edible tissues at 112 d were similar for birds in the control and 1x groups. On the basis of all variables monitored, including body weight gain and feed conversion, the 10x level of 25-OH-D3 produced clear toxicity (but no mortality), the 5x level caused limited threshold toxicity, and the 1x level induced no toxicity. These results indicate that 25-OH-D3 is safe for use in laying hen feed as a source of vitamin D3 at 82.5 micrograms/kg feed (1x), with a margin of safety of approximately 5x between the proposed 1x level and the 5x level (412.5 micrograms/kg feed) that constitutes threshold toxicity in layers.

Evaluation of sodium bicarbonate, chloride, or sulfate with a coccidiostat in corn-soy or corn-soy-meat diets for broiler chickens.

During the period from January to June, combined-sex broiler chickens were inoculated with coccidia via drinking water at 14 d of age. In a completely randomized design (eight replicate pens; 88 chicks per pen) using built-up litter, experimental diets contained monensin plus 0.20% dietary sodium bicarbonate (SBC), which provided 0.054% sodium and 0.144% bicarbonate. Treatment with SBC significantly improved coccidial lesion score, 45-d body weight, and feed efficiency compared with monensin alone. In a 2 x 5 factorial trial using built-up litter pens (eight replicate pens; 88 chicks per pen) vs. each ionophore alone, 0.20% dietary SBC with monensin significantly improved body weight, uniformity, and feed efficiency; 0.20% SBC with halifuginone, lasalocid, monensin, or salinomycin significantly reduced mortality; and 0.20% SBC with lasalocid, monensin, or salinomycin significantly increased breast meat yield. In a 2x4 factorial trial (12 replicate pens; 88 chicks per pen) on built-up litter, corn-soy and corn-soy-meat diets (higher potassium, lower chloride) with monensin were evaluated using 0.054% sodium from SBC, NaCl, or sodium sulfate decahydrate (SSD). With both diet types, SBC (0.20%) or NaCl (0.139% extra) significantly improved weight uniformity, feed efficiency, mortality, and breast meat yield; however, the SSD results were closer to controls. In a 21-d battery brooder test using similar diets and design (2x4 factorial; 4 replicate pens; 10 chicks per pen), SBC and NaCl significantly reduced coccidial lesion scores; SSD produced a significant, but weaker effect. Extra NaCl significantly increased water intake (approximately 37%), water excretion (approximately 27%), and litter moisture (approximately 22%) with both diet types. The SSD did not affect water intake.

Safety of 25-hydroxyvitamin D3 as a source of vitamin D3 in turkey rations.

A target animal safety study investigated the effects of providing 25-hydroxyvitamin D3 (25-OH-D3) as a replacement for vitamin D3 in pelleted turkey feeds. Five groups of turkeys were fed diets containing vitamin D3 at 68.9 micrograms/kg feed (control) or 25-OH-D3 at concentrations of 49.5 (0.5x), 99 (1x), 495 (5x) or 990 (10x) micrograms 25-OH-D3/kg feed. The effects of 25-OH-D3 or vitamin D3 on performance, health, hematology, gross pathology and tissue concentrations of 25-OH-D3 in female and male turkeys were compared at 112 days of feeding. There was no significant difference from control in pen body weight in any of the groups. When feed conversion was calculated without taking into account body weights of birds that died during the study, there was no significant difference from control in any of the groups. When feed conversion was corrected for mortality, the only significant effect was that females at the 5x level (495 micrograms 25-OH-D3/kg feed) had improved feed conversion. Significantly increased mortality occurred during the study in the 10x (990 micrograms 25-OH-D3/kg feed) male group only. No histomorphologic tissue alterations attributable to dietary administration of 25-OH-D3 were observed in tissues examined at any dietary level of 25-OH-D3. 25-OH-D3 did not adversely affect animal health at the proposed use level of 99 micrograms/kg feed when replacing vitamin D3 in turkey rations. The proposed use level also provides at least a 5-fold margin of safety.

Effect of betaine on the growth performance of chicks inoculated with mixed cultures of avian Eimeria species and on invasion and development of Eimeria tenella and Eimeria acervulina in vitro and in vivo.

At 7 d postinoculation (DPI) with a mixed culture of avian Eimeria species, 21-d-old chicks maintained in batteries and floor pens on a diet containing 0.15% (3 lb/ton) betaine plus 66 ppm (60 g/ton) salinomycin were significantly heavier and had significantly lower feed conversion ratios and mortality than chicks fed diets containing 0.15% betaine or 66 ppm salinomycin alone, or the control diet. At 31 DPI, when the chicks were 45 d old, the differences between the diet groups were not as great as at 7 DPI. In vitro, except at high concentrations, betaine was nontoxic to sporozoites of Eimeria tenella or Eimeria acervulina and had little effect on their invasion and development in cultured cells. In vivo, invasion by E. tenella and E. acervulina sporozoites was significantly reduced in all chicks fed diets containing betaine or salinomycin compared with that in control chicks. There was a significant interaction between betaine and salinomycin that impacted on invasion by both species. Overall development of E. tenella did not appear to be adversely affected by addition of betaine to diets containing salinomycin. Conversely, development of E. acervulina was reduced in chicks fed diets containing 0.075% (1.5 lb/ton) betaine plus 66 ppm salinomycin as compared with that in chicks fed salinomycin alone.

Comparison of dietary 25-hydroxycholecalciferol and cholecalciferol in broiler chickens.

We conducted a series of 10 feeding trials involving over 36,000 broilers. The effects of various dietary levels of cholecalciferol (vitamin D3) or 25-hydroxycholecalciferol (25-OH-D3) were compared using a "basal" dosage level of 69 micrograms/kg feed, as well as levels ranging from .5 to 1.5 times the basal level. For all 10 studies, average body weight increased by an average of .042 +/- .03 kg (P < .001) and adjusted feed efficiency decreased (improved) by an average of .026 +/- .0046 kg/kg (P < .001) in birds fed 25-OH-D3 in comparison to those fed vitamin D3 at the basal level. Changes in mortality were not detected. Evaluation of different dietary levels of 25-OH-D3 revealed a significant dose-response relationship, with maximal effects on weight gain, feed efficiency, and breast meat yield being observed in the range of 50 to 70 micrograms/kg feed. Preliminary studies with different levels of vitamin D3 suggested no additional benefits on weight gain or feed efficiency with higher dietary levels of vitamin D3. Serum 25-OH-D3 concentrations increased more rapidly in birds fed 25-OH-D3 than in birds fed vitamin D3. There were significant correlations with body weight, feed conversion, and serum 25-OH-D3 concentrations, with no correlations observed between serum 1,25-(OH)2D3 concentrations and these variables.

Delay of onset of oviposition in pullets promoted by 6-methoxybenzoxazolinone.

Single Comb White Leghorn pullets were used to determine the effects of 6-methoxy-2-benzoxazolinone (6-MBOA) and photoperiod on sexual maturity and egg production. Pullets were maintained on a constant 11L:13D photoperiod until 18 weeks of age and then were divided into two light-controlled chambers. Half the pullets in each chamber received a standard layer mash and the other half received the same diet supplemented with 6-MBOA (MB). Over the ensuing 21 days, the photoperiods were increased to 15L:9D in one chamber and 12L:12D in the other. Consumption of MB resulted in delayed sexual maturity and lower average egg production of those pullets when compared with pullets in the 15L:9D chamber. No significant difference between MB and C pullets was noted in the 12L:12D chamber. These results are similar to those obtained with pinealectomized quail and chickens.

Response of broiler chickens to dietary energy and lysine levels in a warm environment.

Two trials were conducted to determine the response of 23- to 47-day-old broiler chickens to dietary lysine and energy levels when reared in a 26.7 C environment. Broiler finishing diets, which contained 3100, 3175, 3250, or 3325 kcal ME/kg of feed were fed in combination with either .308 or .322% lysine/Mcal (kg) with a constant 18.7% dietary protein. Male and female body weights were not statistically different (P less than .05) among dietary energy levels when both sexes were fed .308% lysine/Mcal (kg). When the male chicks were fed .322% lysine/Mcal (kg), body weights increased with increasing dietary energy level. Feed utilization also increased with increasing dietary energy level when broilers were fed either .308 or .322% lysine/Mcal (kg). These data suggest that the body weight response to dietary energy level when broilers were reared in a warm environment will occur only when adequate amino acid levels are employed. The dietary energy requirement is at least 3250 kcal ME/kg of feed when 23- to 47-day-old broilers are fed .322% lysine/Mcal (kg) and reared in a hot environment but appeared to be lower when broilers were fed .308% lysine/kg of feed.

The effect of dietary energy level and broiler body weight on abdominal fat.

Utilizing a moderate rearing temperature regimen, two trials were conducted to determine the effect of dietary energy level on the amount of abdominal fat deposited when broilers are grown to equal body weight by varying growth time. The most abdominal fat (2.29% average of live weight for male and females) was produced by broilers offered a diet calculated to contain 3325 ME kcal/kg. The least amount of abdominal fat (1.92% average of live weight for male and females) was produced by broilers offered diets calculated to contain 3100 and 3175 metabolizable energy (ME) kcal/kg. In one additional day (48 vs. 47 days) the growth of the broilers offered diets calculated to contain 3100 and 3175 ME kcal/kg equalled that of broilers offered diets calculated to contain 3250 and 3325 ME kcal/kg. Feed conversion (g feed/g live weight) significantly decreased as dietary energy level increased. Three additional trials were conducted to determine when abdominal fat is deposited in relation to age and weight. It was found that male broilers offered diets calculated to contain 3325 ME kcal/kg had as much abdominal fat when expressed as a percent of body weight at 40 days of age as they did at 53 days of age.

Effects of dietary nutrient density on broiler performance at low and moderate environmental temperatures.

Three broiler finishing rations with calculated metabolizable energy values (ME) of 3175, 3250, and 3325 kcal/kg and constant lysine and sulfur-bearing amino acid: energy ratios were evaluated at two environmental temperatures. Broiler chickens were reared from 3 to 7 weeks in either an 18.3 or 26.7 C temperature. At the 18.3 C temperature, 7-week body weights increased linearly 3.1% as energy level increased from lowest to highest level. Feed:gain ratio decreased linearly 5.0% as energy level increased from lowest to highest. At the 26.7 C temperature, no significant differences were found in 7-week body weights due to energy level of the diet. Feed:gain ratio decreased 3.2% as energy level increased from lowest to highest, but the response was not linear. Energy intake increased as dietary energy was increased in the cool temperature; energy intake was less in the warm temperature and did not change appreciably as dietary energy changed. Because lysine and methionine plus cystine were tied to dietary energy by a fixed ratio, the pattern for intake of these amino acids was the same as for energy. It appears that the procedures used to formulate the diets do not give uniform results for the range of environmental temperatures and energy levels tested.

Dietary energy requirements of broilers reared in low and moderate environmental temperatures. 1. Adjusting dietary energy to compensate for abnormal environmental temperatures.

Four trials were conducted to determine the feasibility of replacing fossil fuel energy with dietary energy to meet the 23- to 48-day-old broiler chicken's energy requirements during abnormal cold exposure. Sexed broilers were fed 3250 or 3500 kcal metabolizable energy (ME)/kg in a 21.1 C environment (a normal management situation), and 3250 or 3125 kal ME/kg in a 26.7 C environment. Body weights and feed utilizations increased when broilers were exposed to a 15.6 C environmental temperature and fed 3375 kcal ME/kg dietary energy as compared to feeding a 3250 kcal ME/kg dietary energy in the same environment. When broilers were reared in a 10.0 C environment, maximum body weights were not obtained by increasing the dietary energy from 3250 to 3500 kcal/kg dietary energy. Broiler males, fed 3250 kcal ME/kg and reared in either a 21.1 or a 26.7 C environment, were larger than males reared in 10.0 C environment. No significant differences were found in broiler female weights reared in a 10.0, 15.6, or 21.1 C environment and fed 3250 kcal ME/kg in each temperature regimen. Feed utilizations were the same broilers were reared in a 15.6 C environment and fed 3375 kcal ME/kg compared to broilers reared in a 21.1 C environment and fed 3250 kcal ME/kg. These results indicate that maximum performance of 23- to 48-day-old broilers may be achieved in a 15.6 C environment by feeding a high energy diet (3375 kcal/kg). Results also showed that dietary energy may replace fossil fuel energy that would normally be supplied in a 21.1 C environment.

Effect of calcium carbonate particle size on the available phosphorus requirement of broiler chicks.

Sixteen hundred broiler strain cockerels housed in battery brooders 1 to 21 days of age were used to determine the effect of feeding different commercially available particle-sized calcium carbonate (CaCO3) on the phosphorus requirement. Five replicates of 8 chicks each were fed corn-soy type diets consisting of either 12 to 20, 20 to 60, or 100 to 200 (passed-retained basis) United States Bureau of Standards (USBS) sieve-sized CaCO3. Each particle-sized CaCO3 was fed in diets containing either .20 to .30% (Experiment 2), or .20 to .45% (Experiment 3) available phosphorus (AP) with .05% increments. Supplementary phosphorus was added as sodium phosphate monobasic. Tibia ash and body weight were greater when the USBS 20 to 60 particle-sized CaCO3 was fed then when either the USBS 12 to 20 or 100 to 200 particle-sized CaCO3 was fed. 90% dietary calcium was fed to broiler chicks, the phosphorus requirement was either .35% AP with the USBS 20 to 60 particle-sized CaCO3 or at least .45% AP with either the USBS 12 to 20 or 100 to 200 particle-sized CaCO3. Blood alkaline phosphatase, which indicates bone calcification, was inversely correlated (r = -.65) with bone ash. Blood calcium and blood phosphorus increased, and blood alkaline phosphatase decreased with increasing dietary phosphorus. These data show that the 21-day-old broiler chick's available phosphorus requirement is less in corn-soybean meal diets containing a USBS 20 to 60 particle-sized CaCO3 than in diets containing either the USBS 12 to 20 or 100 to 200 particle-sized CaCO3.

Effects of dietary ascorbic acid, aspirin, lysine, and thiouracil on thyroid activity.

Broiler chickens were reared in batteries and fed diets designed to determine the effects of either ascorbic acid, aspirin (acetylsalicylic acid), lysine, or thiouracil on thyroid weight and serum thyroid hormone concentrations. Thyroxine (T4) and 3,5,5'-triiodothyronine (T3) concentrations in serum were determined by radioimmunoassay. Neither ascorbic acid nor lysine affected T3 or T4 concentration, but thiouracil significantly reduced T3 concentration after 1 day and reduced T4 concentration after 3 days. After 3 days or more of thiouracil feeding, relative reduction was greater for T4 than T3. Dietary aspirin significantly reduced T3 concentration at 7 of 16 sampling times but significantly reduced T4 concentration at only 1 of 16 sampling times. After 11 days of the dietary treatment, chickens fed thiouracil had significantly heavier thyroids than the controls but ascorbic acid, aspirin, and lysine had no effect on thyroid weight.

Effect of dietary Fe to Cu ratios on hematological and growth responses of broiler chickens.

A total of 2,640 broiler strain cockerels were used in three experiments to determine the interrelationships between Fe and Cu requirements of 1- to 21-day old broiler chicks. In each experiment, a starch non-fat milk basal diet was fed to chicks maintained in battery brooders beginning at 1 day of age. Maximum hemoglobin levels and packed cell volumes (PCV) of 21-day old chicks were found by feeding 80 parts per million (ppm) of dietary Fe and 8 ppm of dietary Cu from 1 to 21 days of age. The heaviest 21-day old chicks were found by feeding 80 ppm dietary Fe. Variations were found among experiments in the copper requirement based on body weight. The Cu requirement ranged from 8 to 16 ppm as indicated by 21-day old chick weights. A 10:1 dietary Fe to Cu ratio with an Fe requirement of 80 ppm appeared to maximize hemoglobin levels and PCV's of 21-day old broiler chicks; whereas, a 5:1 dietary Fe to Cu ratio, rather than a 10:1, 15:1, or 20:1 ratio, maximized 21-day old chick weights. Iron requirements for hematological and growth responses are essentially the same; however, the copper requirement may be slightly different for the two criteria.

Effect of dietary fiber on egg yolk, liver, and plasma cholesterol concentrations of the laying hen.

Two experiments were conducted to determine the effect of dietary fiber source and level on egg yolk, liver, and plasma cholesterol concentrations of White Leghorn laying hens. Initially, dietary fiber levels of 2.05, 4.41, 6.68, and 8.79% furnished mainly by sunflower meal were fed to laying hens for 140 days. In the second experiment, alfalfa meal, ground whole oats, sunflower meal, rice mill feed, or wood shavings was added to a corn-soybean meal basal diet to furnish 2.00% added crude fiber and fed to laying hens for 84 days. Yolk cholesterol decreased 4.39, 10.38, and 13.29% by feeding crude dietary fiber levels of 4.41, 6.68, and 8.79%, respectively, to hens as compared to a corn-soybean meal basal diet containing 2.05% crude fiber. Egg yolk cholesterol was significantly decreased by feeding alfalfa meal, oats, sunflower meal, rice mill feed, or wood shavings to laying hens when compared to yolk cholesterol of hens fed the basal diet. The greatest reduction in egg yolk cholesterol was found by feeding either oats or wood shavings. No significant differences were found in plasma cholesterol due to dietary fiber level. Plasma triglycerides decreased and liver cholesterol increased as dietary fiber level increased in diets fed to laying hens. When laying hens were fed alfalfa meal, oats, rice mill feed, or wood shavings, plasma cholesterol significantly decreased. Liver cholesterol increased when hens were fed either alfalfa meal or rice mill feed as the primary fiber source.

Lysine requirement of broilers as influenced by environmental temperatures.

Two experiments were conducted to determine the influence of 15.6 and 29.4 degrees C. environmental temperatures on 2- to 4-week broiler lysine requirements. Weights for 4-week-old cockerels were maximum when either 1.10% dietary lysine in the 15.6 degrees C. environment or 1.00% dietary lysine in the 29.4 degrees C. environment were fed. Feed was used more efficiently by 4-week old cockerels fed either 1.10% dietary lysine in the 15.6 degrees C. environment or 0.95% dietary lysine in the 29.4 degrees C. environment. Plasma free lysine concentrations from 4-week-old cockerels increased as dietary lysine increased. Total plasma free amino acid concentrations from chicks grown in a 15.6 degrees C. environment were approximately 25% greater than from chicks grown at 29.4 degrees C. Total plasma free amino acids for 4-week-old cockerels peaked when 1.05% dietary lysine in the cool environment and 0.95% dietary lysine in the warm environment were fed.

A comparison of iron bioassay diets.

Two broiler chick experiments wer conducted to evaluate four basal diets for iron bioassay suitability. The test basal diets, identified according to their principal ingredients and iron content, were: (1) starch-skim milk - 15 p.p.m., (2) degerminated corn-skin milk - 18 p.p.m. (3) degermianted corn-fish meal-isolated soy - 45 p.p.m., and (4) degermianted corn-fish meal-dehulled soy - 59p.p.m. Significant differences between an iron source with known low availability (ferric oxide) and a highly available iron source (ferrous sulfate) were not detected with the degerminated corn-fish meal-isolated soy or the degerminated corn-fish meal-dehulled soy diets. Likewise, there were no significant differences found between supplemental iron levels, 10 and 20 p.p.m. The corn-skim milk and starch-skim milk diets were both found to be satisfactory for iron bioassays. However, the sample size needed to estimate the population mean was almost twice as great for the starch-skim milk fed groups, than was needed for the corn-skim milk fed groups which indicates the corn-skim milk diet obtained greater sensitivity in testing iron sources and levels. Mortality was excessively high in the starch-skim milk fed group. Ferrous sulfate was superior to ferric oxide as a source of iron.