Hens of a commercial strain of SCWL hens were subjected to a molt and allowed to resume production before being placed on test diets consisting of a nutritionally complete basal diet supplemented with three sources of sodium (sodium chloride, sodium bicarbonate, and sodium sulfate) at three levels of added sodium (0.10, 0.20, 0.30%) with three levels of nonphytate phosphorus (0.25, 0.45, and 0.65%) in a complete factorial arrangement.When non-chloride sources of sodium were used the diet was supplemented with 0.12% Cl from calcium chloride.A reference group of hens within each level of nonphytate phosphorus was fed a diet with no supplemental sodium or chloride.Each of the thirty resulting dietary treatments was assigned to eight groups of hens, with a replicate group consisting of five 30.5 x 45.7 cm cages with one hen per cage fed from a common feed container.After allowing the hens to acclimate to the test diets for 28 d data were collected for a second 28 d period on rate of egg production, feed intake, egg weight, shell breaking force, and shell deformation time.Results of the study indicate that no more than 266 mg/d of nonphytate P was adequate for egg production.Increasing the dietary P level greater than 0.45% nonphytate P resulted in a significant reduction in egg shell strength.A dietary sodium intake of 128 mg/d appeared adequate to support optimum performance.Use of sodium bicarbonate or sodium sulfate in place of sodium chloride appeared to have no benefits in regard to egg shell strength in this study.

Two studies were conducted in which variable levels of calcium and phosphorus were fed in morning (04:00 to 12:00 hr) and afternoon (12:00 to 04:00 hr) feeds. In the first study, reducing the afternoon nonphytate phosphorus (NPP) content significantly reduced hen-day egg production, increased feed required to produce an egg, had no effect on egg weight, and reduced shell strength. Calcium effects were related primarily to total Ca intake. There were no Ca effects on egg production or feed utilization; however, morning Ca affected egg weight; afternoon Ca and NPP x Ca interaction affected shell strength.The second study, used a different set of morning and afternoon levels of Ca and NPP. Results were similar to the first experiment, indicating that total Ca and NPP intake levels had a greater influence on hen performance than time of day consumed. The hens' wide range of ovulation times inhibited potential advantages of feeding different diets at different times of the day to accommodate the egg formation cycle. However, simultaneous presentation of diets differing in nutrient content may prove beneficial.

Nine consecutive flocks of SCWL pullets were started at 13-wk intervals and housed in individual laying cages. Beginning with the fourth flock, four different age groups of hens from the same genetic line were housed in the same environment and fed the same experimental diets to test the hypothesis that the methionine and total sulfur amino acid (TSAA) requirements of hens vary with age and stage of production. For the last eight weeks of each 13-wk period, estimates were made of methionine and TSAA requirements for maximum egg production, egg weight, and egg mass. Results indicate that the methionine and TSAA requirements do not diminish with age and stage of production. Requirements were greater for the middle and final quarters of production than for the initial quarter. Peak daily requirements for methionine were 384, 380, and 402 mg/day for egg production, egg weight, and egg mass, respectively. These results indicate that the application of a phase feeding program based upon a reduction in protein or amino acid requirement as hens age has no scientific basis. Adjustments should be made in dietary amino acid levels to compensate for changes in daily feed intake as influenced by environmental changes, feather covering, or other factors in order to maintain a constant amino acid intake, but adjustment based on age or stage of production is not justified.

Six trials were conducted at different locations to examine the response of broiler chickens to roxarsone and bacitracin in the form of bacitracin methylene disalicylate (BMD) in the presence of the anticoccidal narasin. All diets contained narasin (80 mg/kg) and were fortified with a factorial arrangement of roxarsone (0 to 50 mg/kg) and BMD (0 or 55 mg/kg). Broilers were grown to market weights with narasin and roxarsone removed from the diets for the final 5 days. Addition of both roxarsone and BMD resulted in significant (P less than .05) improvements in body weight and feed utilization. Response to roxarsone for feed utilization was influenced to some extent by the presence or absence of BMD. Although the response to roxarsone was always positive, the degree of response was lessened by the presence of BMD. This resulted in a significant (P less than .10) interaction between roxarsone and BMD for feed utilization but not for body weight.

Studies were conducted at six locations over a 7-yr period to evaluate the response of broiler chickens to bacitracin methylene disalicylate (BMD) and roxarsone in the presence of diets containing 3 ppm halofuginone/kg feed. Treatments consisted of a 2 x 2 factorial arrangement with 0 or 55 mg BMD and 0 or 50 mg roxarsone/kg feed. These additives were fed beginning with day-old chicks and were removed 6 days before termination of the study, which varied in length from 48 to 56 days among locations. Body weights were significantly improved (P less than .05) by the addition of either BMD or roxarsone with a significant interaction (P less than .05) between BMD and roxarsone. Roxarsone improved body weights only in the presence of BMD. Feed utilization was significantly (P less than .05) improved by addition of either BMD or roxarsone, with no interaction between the two products.

Three experiments were conducted by sampling a total of 15,705 eggs from Leghorn hens fed diets varying in methionine, Na, and Ca content. In Experiment 1, birds of four different ages were housed in a common environment and fed diets containing between .233 and .383% methionine. In Experiment 2, birds of five different ages were housed in a common environment and fed diets containing .15, .30, and .45% Na and .25, .45, and .65% nonphytate phosphorus (NPP). In Experiment 3, eggs were sampled from 42 to 62 wk of age in 4-wk intervals from hens fed diets containing from 3 to 9% Ca in increments of 1.5%. Feeding lower levels of methionine (.233%) produced significantly lower egg weights and greater shell strength but at the expense of a decline in egg production at early ages. Reducing the NPP level from .65 to .25% produced lower egg weights and greater shell strength. A corresponding drop in production was not observed except at the .45%-Na level. No significant effects of Na on shell strength were observed. Higher Ca levels produced greater shell strength and had variable effects on egg weight. Increasing the Ca level beyond 6% resulted in a significant decline in production. Regression analyses indicated that within a population, the relationship between egg weight and shell strength is positive. In some instances, the relationship was curvilinear, where the positive association between egg weight and shell strength decreased with increasing egg weights.

Addition of the hypocholesteremic agent Probucol ((4,4′-isopropylidine dithio)-bis(2,6-di-t-butyl-phenol)) to the diet of laying hens at up to 1% significantly reduced egg yolk cholesterol content (mg/g yolk) without impairment of rate of egg production, egg weight, shell strength, albumen quality, or other production related parameters. Dietary concentration of .1% Probucol significantly reduced yolk cholesterol within 2 weeks after feeding. Higher concentrations did not further reduce yolk cholesterol. Probucol at .025% reduced egg yolk cholesterol within 4 weeks after feeding, but after 8 weeks of feeding, eggs from hens fed .025% Probucol did not differ significantly in yolk cholesterol from those fed the basal unsupplemented diet. This suggests possible adaptation in cholesterol synthesis by the laying hen.

Five trials were conducted at various locations to determine the response of broiler chickens to the addition of zinc bacitracin to diets containing both salinomycin and roxarsone. Results indicate that when a combination of salinomycin and roxarsone is used as an anticoccidial, the addition of zinc bacitracin at 33 or 55 mg/kg diet will improve growth rate and feed utilization by broiler chickens. Regression of body weight and feed utilization on dietary levels of zinc bacitracin indicated that each milligram of zinc bacitracin in the diet increased the 49-day weight of broiler chickens by .92 g and reduced the feed required per gram of gain by .0012 g.

Studies in this report examined the possibility of utilizing soybean meal processed to a higher urease value for broiler chickens. Such meals might be produced with lower energy costs and possible savings to the feed manufacturer. Untoasted, solvent-extracted dehulled soybean flakes were subjected to differing cooking times in an autoclave and in a steam-jacketed mixer with steam sparging to produce flakes with a range of urease values.

Four experiments were conducted to examine the response of broiler chickens to different levels of niacin. Practical-type diets, calculated to contain from 20.7 to 23.7 mg niacin per kg from intact ingredients, were fortified with a complete vitamin mixture which provided 33 mg supplemental niacin per kg of diet, in excess of the National Research Council (1977) suggested requirement of 27 mg per kg through 6 weeks of age. A niacinamide supplement was used to provide additional levels of 0, 33, or 66 mg per kg. Diets differed in content of added fat and energy levels in two of the experiments and in the presence or absence of animal protein sources in two others. The addition of niacinamide at 33 and 66 mg per kg to a diet already supplemented with 33 mg per kg from a complete vitamin premix, calculated to exceed the present NRC suggested requirement, resulted in improved body weight gains with sex differences noted in some experiments. Feed utilization was improved in some studies. There was no effect on the amount of abdominal fat or carcass dressing percentage. The results of these studies indicate that the modern rapidly growing broiler chick may require niacin levels greater than those generally recommended by the National Research Council (1977), which are based largely on studies where performance was considerably lower than obtained with the modern strains of broilers.

Seed from two species of amaranth (Amaranthus cruentus and A. hypochondriacus) were incorporated into diets at 20 and 40% in raw and autoclaved form. Weight gains of chickens fed diets with 20% amaranth did not differ significantly from that of chickens fed a corn-soybean meal control diet, whether grain was fed raw or autoclaved. Feed intake was reduced slightly at this level of inclusion. Weight gains and feed intake of chickens fed diets containing 40% amaranth were significantly reduced. Reduction in performance was more severe in chickens fed hypochondriacus species and was partially alleviated by autoclaving. Results indicate that amaranth grain may be utilized by broiler chickens, but further work is necessary to determine means to overcome growth depression associated with higher usage levels and to assess possible species differences.