Evaluation of corn distillers dried grains with solubles as an alternative ingredient for broilers.

The effects of graded levels of corn distillers dried grains with solubles (DDGS) were investigated as a partial replacement for sources of protein, energy, and other nutrients for broilers when the digestible amino acid balance was maintained. Zero, 8, 16, and 24% DDGS were incorporated into isonutritive diets at the expense of corn, soybean meal, and dl-Met. Poultry oil, l-Lys, and l-Thr additions increased with increasing levels of DDGS. Diets were each fed to 36 Cobb 500 straight-run broilers in 6 floor pens in 2 experiments. In experiment 1, broilers fed ≥8% DDGS showed increased BW gain compared with those fed the control diet during the 0- to 18-d starter period (P = 0.0164) but were almost identical in BW at 42 d (P = 0.9395). The only difference at 42 d was in the carcass fat composition of female broilers: percentage of fat pad decreased with increasing DDGS level (P = 0.0133). Corn DDGS reduced the pellet durability index. However, the pellet durability index was not related to growth or feed utilization. In experiment 2 at 42 d, broilers fed all levels of DDGS showed increased BW gain compared with those fed the control diet. Broilers may perform well when fed properly balanced feeds containing up to 24% DDGS despite reduced pellet quality.

The effect of breeder age and egg storage time on phosphorus utilization by broiler progeny fed a phosphorus deficiency diet with 1alpha-OH vitamin D3.

Two experiments were conducted to determine that variation in broiler P utilization is due to breeder age and egg storage time. Experiment 1 was conducted with chicks hatched from eggs laid by Ross x Ross 308 breeders (27 vs. 61 wk old) and stored for 0 or 10 d. The age of breeders had significant effects (P < 0.05) on 0 to 16 d chick growth (379 +/- 18 vs. 308 +/- 19 for 27- and 61-wk-old breeders, respectively). The longer egg storage time of chicks from older breeders resulted in higher P rickets scores and incidence, but longer egg storage time of chicks from younger breeders resulted in lower P rickets score and incidence (significant interaction, P = 0.0455). The longer egg storage time of chicks from older breeders resulted in lower bone ash (%), and the longer egg storage time of chicks from younger breeders resulted in higher bone ash (%). Experiment 2 was conducted with chicks hatched from eggs laid by Ross x Ross 308 breeders (26 vs. 60 wk old) and stored for 0 or 10 d. The diets were P deficient and with or without 5 microg/g of 1alpha-OH cholecalciferol (1alpha-OH vitamin D(3)). Breeder age had significant effects (P = 0.0003) on 0 to 16 d chick growth (272 +/- 7 vs. 339 +/- 8 for 26- and 60-wk-old breeders, respectively) and chick mortality (P = 0.0134). The P rickets score increased with breeder age (P = 0.0186) and egg storage time (P = 0.1057). The factors influencing the incidence of P rickets in broilers should include breeder age and egg storage time as well as genetics and dietary levels of Ca, P, and vitamin D activity of the P-deficient diets.

Performance of different broiler genotypes fed diets with varying levels of dietary crude protein and lysine.

Two experiments were conducted to determine if a 3-way interaction among genotype, dietary lysine, and CP is an important influence on dietary responses. The genotypes were Ross 308 and Cobb in experiment 1 and Ross 508 and Arbor Acres Classic in experiment 2. The experimental designs were completely randomized with an incomplete 2 x 2 x 3 factorial arrangement of treatments. On d 7 of experiment 1, 4 replicate pens of 6 chicks each were fed 1 combination of dietary lysine and CP (17% CP with 0.6, 0.7, and 0.8% lysine and 23% CP with 0.7, 0.8, and 0.9% lysine) until d 21. On d 17 of experiment 2, 4 replicate pens of 35 chicks each were fed 1 combination of dietary lysine and CP (17% CP with 0.7, 0.8, and 0.9% lysine and 23% CP with 0.8, 0.9, and 1.0% lysine) until d 42. On d 43 of experiment 2, 3 birds per pen were processed. Regression analysis showed differences (P < 0.05) due to genotype for body weight gain (BWG), feed intake, and feed conversion ratio (FCR) in experiment 1, and BWG, carcass yield, breast fillet and tender yields, and abdominal fat pad percentage in experiment 2. Increasing dietary CP decreased abdominal fat pad percentage in both experiments; however, increasing dietary lysine only decreased this parameter in the starter-phase chicks. In both experiments, Ross broilers had a greater response to supplemental lysine when 17% CP was fed, but less response to supplemental lysine when 23% CP was fed for both BWG and FCR (3-way interaction). Three-way interactions between dietary CP and lysine levels and genotype were observed for BWG (P < 0.01), feed intake (P < 0.01), and FCR (P < 0.02) in experiment 1 and for feed intake (P < 0.06) and FCR (P < 0.03) in experiment 2. The 3-way interactions demonstrate that quantitative differences exist between genotypes in response to increasing dietary levels of CP and lysine.

The effect of feeding calcium- and phosphorus-deficient diets to broiler chickens during the starting and growing-finishing phases on carcass quality.

There is considerable data on the effect of reducing inorganic Ca and P in broiler finisher diets on carcass quality. However, there is limited information on the effect of reducing dietary Ca and P during the different phases of growout. Two experiments were conducted from 0 to 35 d in floor pens. In both experiments, at least 4 replicates per treatment (50 chicks per replicate) were used. Corn-soybean meal and soybean oil-based diets deficient in Ca and P were fed. During the starter phase (ST), from 0 to 18 d, chicks were fed a 23% CP diet containing 0.60% Ca and 0.47% total P (tP). During the grower-finisher phase (GF), from 19 to 35 d, birds were fed a 19% CP diet containing 0.30% Ca and 0.37% tP. A combination of 1,000 phytase units/kg of Natuphos phytase and 5 microg/kg of 1alpha-hydroxycholecalciferol (P + 1alpha) was supplemented to some of the feed during the ST and GF. Diets containing adequate Ca and P were also fed during the ST (0.90% Ca and 0.68% tP) and GF (0.80% Ca and 0.67% tP). The level of tibia ash and the incidence of bone disease were measured at 18 and 35 d. At the end of the experiments, birds were processed and evaluated for muscle hemorrhages and broken bones. In both experiments, broilers fed diets that were not P + 1alpha supplemented demonstrated poor bone mineralization, considerable leg problems, and a high incidence of broken bones after processing. Broilers fed P + 1alpha throughout had more broken clavicles and femurs compared with birds fed the adequate diets. Day-18 tibia ash was significantly correlated to broken tibias and femurs during processing. Day-35 tibia ash was better correlated to bloody breast meat than to broken bones. It is concluded that carcass quality depends on the levels of Ca and P fed and the age of the bird. Tibia ash, traditionally used as an indication of bone strength, was better correlated to the incidence of bloody breasts.

The effect of maternal dietary vitamin D3 supplementation on performance and tibial dyschondroplasia of broiler chicks.

A series of experiments was conducted to investigate the effects of maternal dietary vitamin D3 supplementation at 4 different times during the laying cycle, on the performance and bone quality of broiler chicks fed a diet that induced tibial dyschondroplasia (TD) or an adequate diet. Ross x Ross broiler breeder hens were fed a corn-soy diet with various levels of vitamin D3 from 24 to 66 wk of age. Eggs were collected at 39, 44, 53, and 64 wk of age and hatched. Chicks from hens fed 250 IU of D3/kg (low maternal D3 or LMD3) and 2,000 IU of D3/ kg (high maternal D3 or HMD3) levels were placed in battery brooders and fed the diets from 0 to 16 d. At 16 d, the chicks were weighed and killed; the left tibias were used for bone ash determinations, and the right tibias were used to score the incidence and severity of TD (0, 1, 2, or 3, where 3 is the most severe). Body weight gain and feed intake were significantly lower for the LMD3 chicks at wk 44 and 64, although there was no difference in weight at hatch. For the first 2 hatches (wk 39 and 44), the LMD3 and HMD3 chicks demonstrated high average TD scores (2.03 and 1.57 vs. 2.05 and 1.75 for the LMD3 vs. HMD3 chicks, respectively) and high average incidences of severe TD (50 and 35% vs. 45 and 34% for LMD3 vs. HMD3 levels, respectively). However, results from the last 2 hatches (wk 53 and 64) showed that HMD3 chicks, compared with LMD3 chicks, had reduced average TD scores (1.39 and 1.47 vs. 1.01 and 0.44 for LMD3 vs. HMD3 levels, respectively) and severe TD incidence (36 and 40% vs. 17 and 8% for the LMD3 vs. HMD3 levels, respectively). In this experiment, as egg production declined toward the end of the laying cycle, hens fed the HMD3 might have been able to deposit sufficient quantities of vitamin D3 in the egg to maintain excellent body weight gain at 16 d of age and reduce the incidence and severity of TD. Hens fed the LMD3 diet were unable to produce similar improvements.

Correlated responses to divergent selection for phytate phosphorus bioavailability in a randombred chicken population.

The current study was undertaken to evaluate the correlated responses to 3 generations of divergent selection for phytate phosphorus bioavailability (PBA) in the Athens-Canadian randombred chicken population. The traits studied were BW at 4 wk of age, BW gain (BWG), feed consumption (FC), and feed conversion ratio (FCR) during a period of 3 d. The first evaluation criterion was the cumulated divergent correlated response (CR(C)), which was calculated as the line difference of the least square means of phenotypic values for each trait at a given generation after adjustment for sex and hatch effects. The results showed a consistent correlated response in BW across generations. The CR(C) at generation G3 was 26.8 g (P < 0.01). The chickens in the low PBA line (L line) had higher BW than the high PBA line (H line). The CR(C) for BWG, FC, and FCR were significant (P < 0.05) only at G3. The second evaluation criterion was the average best linear unbiased prediction estimated breeding value (EBV). The results showed asymmetric genetic trends in BW, BWG, and FC, and the correlated responses were mainly due to the genetic changes that occurred in H line because little genetic change occurred in L line across generations. At G3, the line differences of EBV were close to the CR(C) values for all the traits except FCR. This suggested that CR(C) and EBV criteria would tend to be consistent with the increase across generations. However, at G1 and G2, the line differences of the EBV actually deviated from the CR(C) values for BWG and FC. The inconsistency could be attributed to experimental errors and genetic drift that were not accounted by the fixed model for obtaining CR(C).

Genetic analysis on the direct response to divergent selection for phytate phosphorus bioavailability in a randombred chicken population.

The current study was undertaken to evaluate the direct response to 3 generations of divergent selection for phytate P bioavailability (PBA) in the Athens-Canadian randombred chicken population. Cumulated divergent response (R(C)) was measured as the line difference in PBA at a given generation after adjusting for hatch and sex effects. Results showed a significant response at generation (G)1. The R(C) was unchanged from G1 to G2 and increased (1.62%) from G2 to G3 (P < 0.01) due to the application of best linear unbiased prediction (BLUP) selection in the line selected for high PBA at G2. The average BLUP estimated breeding values were used to estimate the genetic trend for the selected trait across generations. The results showed that the genetic trend was symmetric at G1 and G2 but asymmetric at G3. The application of mixed model methodology was effective in separating the environmental component from phenotypic change. When the data of the high (H) line or the low (L) line in the selected generations (G1 to G3) were combined with the data from the base population (G0), the heritability estimates for PBA were 0.07 +/- 0.02 and 0.09 +/- 0.02, respectively. The line selected for high PBA showed gain, and the line selected for low PBA showed a decrease in estimated breeding values across the generations. The results demonstrated that modest progress could be obtained by incorporating PBA into selection programs. However, other correlated traits of economic importance need to be evaluated before any decision to incorporate selection of PBA into breeding schemes be initiated.

Economically optimal dietary crude protein and lysine levels for starting broiler chicks.

An experiment was conducted to quantify the growth response of broiler chicks to cumulative dietary lysine and CP intakes. From d 7 to 17, chicks were fed one combination of dietary lysine and CP (17, 20, 23, and 26% CP and 3.5, 4.0, 4.5, and 5.0 g lysine per 100 g of CP) in a diet containing 3,200 kcal/kg ME. There were significant linear and quadratic effects of dietary CP intake and quadratic effects of dietary lysine intake on body weight gain (BWG), confirming that a diminishing response (marginal BWG decreased as intake of dietary lysine increased) existed (R2 = 0.92 and 0.95, respectively). A significant interaction between dietary CP and lysine for BWG complicates economic modeling because responses must be considered together. A quadratic growth response equation describing BWG as a function of dietary lysine and CP intake was used to develop and demonstrate a quadratic programming model. In general, increasing the price of soybean meal (SBM) decreased the dietary CP concentrations that gave maximum BWG and the concentration of dietary lysine decreased proportionally. In SBM-based diets, the concentration of dietary lysine that maximized BWG was less than or equal to the concentration reached by the proportions of corn and SBM needed to meet dietary CP constraints. Savings from using maximum-profit vs. least-cost formulation models could approach 637,000 dollars per year for a single model poultry complex under some economic situations for the starter diet alone.

Calcium requirements of the modern broiler chicken as influenced by dietary protein and age.

Two experiments were conducted to examine the calcium requirements of broiler chickens fed corn-soybean meal diets. Experiment 1 used a 6 x 2 x 2 factorial arrangement and was conducted with broilers in floor pens during the grower phase (19 to 42 d). Diets were mixed with 6 levels of dietary Ca (0.325, 0.4, 0.475, 0.55, 0.625, and 0.9%) and 17 or 23% CP and fed to males and females separately. Experiment 2 was a 6 x 2 factorial design conducted using Petersime battery brooders during the starter phase (0 to 16 d). The same 6 levels of dietary Ca used in experiment 1 were fed separately to each sex, but only at the 23% level of CP. The diets used in both experiments were formulated to contain 0.45% nonphytin phosphorus. In experiment 1, grower chickens did not demonstrate significant body weight gain (BWG) or feed conversion ratio (FCR) response (g of feed per g of gain) to the different levels of Ca at either level of protein. The percentage tibia ash did not respond to increasing Ca levels beyond 0.625% Ca at either protein level. In experiment 2, BWG increased linearly up to 0.55 and 0.625% dietary Ca for males and females, respectively. Feed conversion ratio decreased linearly with increasing dietary Ca up to 0.625% Ca, and tibia ash was highest at 0.9% Ca for both sexes. These results suggest that the current NRC Ca requirements for the broiler starter (1.0%) are sufficient for maximum bone ash, but that Ca requirements for grower birds (0.9%) may be excessive for optimum BWG, FCR, and tibia ash.

Phytase and 1alpha-hydroxycholecalciferol supplementation of broiler chickens during the starting and growing/finishing phases.

Supplemental 1alpha-hydroxycholecalciferol (1alpha-OHD3) has been shown to have qualitatively similar and quantitatively additive effects to exogenous phytase. Two experiments were conducted from 0 to 35 d in floor pens to determine the additive effect of phytase and 1alpha-OHD3 when supplemented to Ca- and P-deficient diets. In both experiments, at least 4 replicates per treatment (50 chicks per replicate) were used. Corn-soybean-meal-and soybean-oil-based diets were fed and birds were raised in a house impervious to ultraviolet light. During the starter phase (ST), from 0 to 18 d, chicks were fed a 23% CP diet containing 0.60% Ca and 0.47% total P (tP). During the grower/finisher phase (GF), from 19 to 35 d, birds were fed a 19% CP diet containing 0.30% Ca and 0.37% tP. A combination of 1,000 phytase units/kg of Natuphos phytase and 5 microg/kg of 1alpha-OHD3 (P+1A) was supplemented to some of the feed during the ST and GF. Diets containing adequate Ca and P were also fed during the ST (0.90% Ca, 0.68% tP) and GF (0.80% Ca, 0.67% tP). Performance characteristics and the incidence of rickets and tibial dyschondroplasia were measured at 18 and 35 d. In experiment 1, unsupplemented chicks performed well but had considerable leg problems. Chicks fed P+1A during the ST or GF did not perform as well as birds fed P+1A throughout. Birds fed P+1A throughout performed as well birds fed the adequate diets without any indication of leg problems. In experiment 2, unsupplemented birds performed similarly to unsupplemented birds in experiment 1. However, chicks fed the supplements or the control diets did not perform as well or accumulate as much bone ash as birds in experiment 1, although the diets were formulated identically in both experiments. Diets with as little as 0.30% Ca and 0.37% tP appear to be adequate for broilers older than 18 d if supplemented with the correct amounts of phytase and 1alpha-OHD3. However, there are unknown variables that may limit the potential of broilers in terms of bone mineralization and bone pathology, even when adequate diets are fed.

Effects of calcium and nonphytate phosphorus concentrations on phytase efficacy in broiler chicks.

Phytase supplementation over a range of different levels of dietary Ca and nonphytate phosphorus (NPP) was investigated by comparing surface response curves from regression equations generated with (experiment 1) and without (experiment 2) phytase using various performance and bone quality parameters. Cobb x Cobb broiler chicks were raised from 0 to 16 d in 2 experiments using corn-soybean meal based diets. Experiment 1 used a 4 x 4 factorial arrangement with diets formulated to contain combinations of 4 levels of Ca: 0.38, 0.58, 0.78, and 0.98% and 4 levels of NPP: 0.2, 0.3, 0.4, and 0.5%. Experiment 2 used a composite rotatable design in which rations were formulated to contain dietary Ca levels of 0.38, 0.47, 0.68, 0.89, and 0.98% and NPP levels of 0.20, 0.24, 0.35, 0.46, and 0.50%. An extra point was included in the design to contain the lowest Ca and lowest NPP levels (0.38% Ca and 0.20% NPP). All combinations of Ca and NPP were fed with 657 phytase units/kg Natuphos 5000 phytase, plus 4 combinations (0.38% Ca and 0.20% NPP, 0.47% Ca and 0.24% NPP, 0.68% Ca and 0.35% NPP, and 0.89% Ca and 0.46% NPP) were fed without phytase to determine the suitability of comparing multiple regression response surfaces for particular variables among experiments. Comparison of surfaces, with and without phytase, showed that growth and bone quality responses to phytase were greatest at low NPP levels and high Ca levels, and these decreased when the Ca level was reduced or when the NPP level was increased. A third experiment confirmed that phytase elicits a greater response at higher Ca levels and lower NPP levels (0.86% Ca and 0.20% NPP) versus low Ca levels and low NPP levels (0.47% Ca and 0.24% NPP). The data demonstrated why it is impossible to determine a single NPP equivalency value for phytase supplements.

Pathology and histology of dietary tryptophan deficiency in broiler chicks.

The purpose of this experiment was to characterize a lesion of the rhamphotheca associated with tryptophan (TIRP) deficiency, search for other histological abnormalities,and determine whether bird size and housing conditions are contributing factors to these lesions. Day-old broiler chicks (Ross X Ross 308) were placed in either floor pens with fresh pine shavings or Petersime battery brooders with two pens of 10 chicks each per treatment. Broiler chicks from 0 to 21 days of age were fed adequate (0.24%) and deficient (0.09%) levels of TRP in diets based on corn, corn gluten meal, and gelatin. Separate groups of control chicks were pair fed daily with the deficient chicks. Deficient chicks grew less efficiently than did the pair-fed controls. Upon gross examination, a lesion of the maxillary rhamphotheca in the vicinity of the nares was observed in 61% of TRP-deficient birds housed in the battery and 13% of the birds housed in floor pens. A similar gross lesion was only observed in one control bird. These lesions were located along the upper portion of the beak between the nares and appeared as a crusty or scab-like area on gross examination, composed of detritus, heterophils, and plasma protein. Inflammation occasionally was observed at the dermoepidermal junction. The incidence of lesions was reduced in floor pens compared to battery brooders, but similarly sized birds did not exhibit the lesion. The number of lesions seen grossly and histologically in TRP-deficient birds, as compared to control birds, supports the hypothesis that TRP deficiency is the primary cause of these lesions around the nares of broilers. Secondary environmental factors, perhaps coprophagy, also influence the incidence of the lesion.

Estimation of the composition of broiler carcasses from their specific gravity.

An experiment was conducted to quantify the relationships between broiler carcass specific gravity and chemical composition (percentage moisture, percentage lipid, percentage protein). Carcasses of widely varying compositions were produced by feeding several dietary protein and energy combinations (52 to 64% moisture, 0.6 to 2.5% ash, 1.6 to 11.7% lipid, and 4.9 to 8.0% nitrogen). Very strong relationships were found between percentage moisture and percentage lipid (r = -0.969) and percentage moisture and percentage N (r = 0.968). Strong relationships were found between specific gravity and percentage lipid (r = -0.872) and specific gravity and percentage N (r = 0.857). Specific gravity is recommended as a means to estimate carcass fat in broiler chickens.

Studies on the feeding of cupric sulfate pentahydrate and cupric citrate to broiler chickens.

Male commercial broiler strain chickens were fed either a control diet (based on corn and soybean meal) or the control diet supplemented with cupric sulfate pentahydrate or cupric citrate in seven experiments (six in floor pens, one in wire-floored batteries). In Experiment 1, feeding 125 or 250 mg/kg copper increased growth (4.9%) and decreased feed conversion ratios (3.4%), total plasma cholesterol (40.2%), and breast muscle cholesterol (37.0%). Feeding 375 mg/kg copper was without further beneficial effect. In Experiment 2, withdrawing growth promoting supplements of copper from the feed for the last 7 d caused a significant (P < 0.05) increase in breast muscle cholesterol at 42 d of age: 57.2, 48.0, and 43.2 mg/100 g meat for birds supplemented for 0, 35, or 42 d, respectively. Feeding 10 vs 260 mg/kg copper caused only small increases in tissue copper levels: 0.36 vs 0.41 mg/kg for breast meat, and 0.48 vs 0.60 mg/kg for thigh meat, respectively. Litter copper accumulations in these experiments were similar to those of earlier reports. Breast muscle cholesterol was reduced by feeding 125 mg/kg supplemental copper from cupric citrate (27.84 mg/100 g) or 125 mg supplemental copper from cupric sulfate pentahydrate (25.32 mg/100 g) compared to broilers fed the control diet (43.92 mg/100 g). Cupric citrate was efficacious for growth promotion at lower copper levels than cupric sulfate pentahydrate, resulting in reduced litter copper.

Studies on the effect of feeding cupric sulfate pentahydrate to laying hens on egg cholesterol content.

Two experiments were conducted to test the hypothesis that pharmacological levels of dietary Cu could reduce egg cholesterol content. White Leghorn hens 30 to 39 wk of age were fed corn and soybean meal diets with 0, 125, or 250 mg supplemental Cu/kg diet from cupric sulfate pentahydrate (basal diet = 6.74 mg Cu/kg). Body weight, feed consumption, egg weights, egg specific gravity, and Haugh Units were not consistently affected during the 8-wk feeding trials. Egg production was significantly increased (P < 0.05) in the second 4-wk period by supplemental Cu in both experiments. Egg yolk cholesterol concentrations were decreased by feeding 125 mg Cu/kg diet (11.7 vs 8.6 mg/g, average of two experiments); feeding 250 mg Cu/kg resulted in further declines in egg cholesterol but the differences were not significant (7.9 mg/g). Changes in plasma cholesterol concentrations were similar to those of yolk cholesterol. Small but significant amounts of Cu accumulated in the yolks and shells of eggs from Cu-supplemented hens; however, most of the Cu fed was found in the excreta.

Determination of the methionine requirement of male and female broiler chicks using an indirect amino acid oxidation method.

The methionine requirement of 250-to-300-g broiler chicks was estimated from the oxidation of L-[1-14C] phenylalanine of chicks given meals containing graded levels of DL-methionine. L-[1-14C] phenylalanine was used as an indicator amino acid for amino acid oxidation and, indirectly, protein synthesis. Four experiments were conducted using an incomplete block design with three replications each. Chicks were crop intubated with semifluid diets at a ratio of 1 g of diet per 45 g of bird weight. Two feedings 2 h apart were used to reduce variability, and the sample collection period was 3 h after the second feeding. Regression analysis of 14CO2 release from L-[1-14C] phenylalanine was used to estimate the methionine requirement. The model was as follows: response = max + rc x (req - x) x I, where max = plateau, rc = rate constant, req = requirement, and I = 1 when x < req, otherwise I = 0. The methionine requirements of Ross x Ross chicks were 0.57 +/- 0.03% and 0.52 +/- 0.08% for male and female chicks, respectively in Experiment 1 and 0.55 +/- 0.05% and 0.52 +/- 0.04%, respectively, in Experiment 2. In the third experiment (Arbor Acre High-Yield), phenylalanine oxidation stabilized at a low rate when dietary methionine levels reached 0.54 +/- 0.03% and 0.53 +/- 0.04% for males and females, respectively. In a growth trial covering a longer period (Experiment 4), the methionine requirements of male and female Ross x Ross chicks, based on feed conversion, were 0.52 +/- 0.05% and 0.45 +/- 0.02%, respectively, and based on body gain were 0.54 +/0.09% and 0.48 +/- 0.04%, respectively. The results suggested that the methionine requirement of male chicks tended to be higher than that of females in both strains. However, differences were small and not significant.

The influence of labile dietary methyl donors on the arginine requirement of young broiler chicks.

Two experiments were conducted with Ross x Ross boiler chicks in battery brooders from 1 to 14 d of age to determine the influence of dietary methyl donors on the Arg requirement of young broiler chicks. Experiment 1 had a 6 x 2 factorial design, with six levels of Arg supplementation (0, 0.1, 0.2, 0.3, 0.4, and 0.5%) and two levels of DL-Met supplementation (0 and 0.2% of the diet). The design of Experiment 2 was identical to Experiment 1, except that a second source of labile methyl groups was added, 0.2% betaine (6 x 3 factorial arrangement). Both experiments had four replicate pens of 10 chicks each per treatment. The basal diet was based on corn (34.52%), whey (26.96%), corn gluten meal (16.53%), soybean meal (11.74%), and poultry fat (23% CP and 3.20 kcal/g of ME). At 14 d, three chicks per replicate were randomly killed, and breast muscle was collected and pooled for creatine analysis. The broken-line linear model was used to estimate the Arg requirements of the chicks. There were no differences in Arg requirements due to methyl source so the data were pooled. In Experiment 1, the Arg requirements were 1.17 +/- 0.04% for gain, 1.23 +/- 0.03% for feed conversion ratio (FCR), and 1.18 +/- 0.03% for muscle creatine, when the diet contained 0.45 or 0.65% Met. In Experiment 2, the Arg requirements were 1.20 +/- 0.05% for gain, 1.23 +/- 0.03% for FCR, and 1.26 +/- 0.02% for muscle creatine. There was no apparent difference in the Arg requirement of young broilers due to methyl donor supplementation.

Performance of broiler chicks fed various levels of dietary lysine and crude protein.

An experiment was conducted to establish a basal diet deficient in both protein and lysine. The responses of broiler chicks to graded levels of lysine at two levels of CP were measured in diets mixed by two experimental methods (diet dilution and graded supplementation). Experiment 1 had a 2 x 3 factorial arrangement of treatments with three dietary CP levels (17, 20, and 23%) and two levels of lysine per CP level (35 and 48 g lysine/kg CP). Dietary CP and lysine levels had significant (P < 0.001) effects on body weight gain (BWG), feed intake, and feed conversion ratio (FCR). In exp. 2, the lysine requirement of chicks (9 to 18 d of age) was estimated at two levels of CP in diets mixed by the diet dilution method. The requirements for lysine at 17% CP (as a percentage of CP) were estimated to be 4.45 +/- 0.18% for BWG (R2 = 0.83) and 4.33 +/- 0.16% for FCR (R2 = 0.81). Similarly, the requirements at 23% CP were 4.34 +/- 0.16% for BWG (R2 = 0.84) and 4.35 +/- 0.13% for FCR (R2 = 0.89). In exp. 3, the lysine requirement of chicks (10 to 18 d of age) was estimated at two levels of CP in diets mixed by the graded supplementation method. The requirements for lysine at 18.5% CP were 5.17 +/- 0.25% for BWG (R2 = 0.80) and 4.26 +/- 0.15% for FCR (R2 = 0.85). Similarly, the requirements at 23% CP were 4.59 +/- 0.17% for BWG (R2 = 0.83) and 4.71 +/- 0.16% for FCR (R2 = 0.88). Results of a t-test show that the requirements were not significantly different between the two CP levels for BWG in experiments 2 and 3 (P < 0.05). It is concluded that the amino acid requirements of broilers are a constant proportion of CP levels at least in the range of CP levels commonly fed.

Dietary copper in excess of nutritional requirement reduces plasma and breast muscle cholesterol of chickens.

Male commercial broiler strain chickens were fed from hatching to 42 d of age either a control diet (based on corn and soybean meal) or the control diet supplemented with 250 mg copper/kg diet from cupric sulfate pentahydrate (for 35 or 42 d). Hypocholesterolemia (11.8% reduction) and decreased breast muscle cholesterol (20.4% reduction) were observed in copper-supplemented birds. There was a slight increase (P > .05) in breast muscle copper (14.5%), and all levels were very low (< .5 mg/kg). Feeding copper for 42 vs 35 d resulted in lower levels of cholesterol in the plasma (12.9 vs 10.8% reduction) and breast muscle (24.6 vs 16.2% reduction). Very similar results were found in two additional experiments in which hypocholesterolemia and reduced breast muscle cholesterol were associated with reduced plasma triglycerides and blood reduced glutathione. It is well known that hypercholesterolemia is a symptom of dietary copper deficiency. The data presented here indicate that blood and breast muscle cholesterol are inversely related to dietary copper in excess of the dietary requirement for maximal growth. The cholesterol content of the edible muscle tissue of broiler chickens can be reduced by approximately 25% after feeding a supranormal level of copper for 42 d without altering the growth of the chickens or substantially increasing the copper content of the edible meat.

Modulation of cholesterol levels in broiler meat by dietary garlic and copper.

Male Ross x Ross 208 chickens were fed from hatching to 21 d of age either a control diet (based on corn and soybean meal) or the control diet supplemented with 0, 1.5, 3.0, and 4.5% of a commercial garlic powder in Experiments 1 and 2. Once the dose-response relationship was established, 3% garlic powder or 63 or 180 mg/kg copper as cupric citrate or cupric sulfate pentahydrate were supplemented to the diet (Experiments 3, 4, 5, and 6). In the first two experiments, reductions of plasma cholesterol (P = 0.006) and triacylglycerols (P = 0.013) and liver (P = 0.012) and breast muscle (P = 0.165) cholesterol were observed in garlic-supplemented birds. Feeding either garlic powder or copper (63 and 180 mg/kg) resulted in reduced levels of plasma cholesterol, liver cholesterol, blood reduced glutathione, and breast and thigh muscle cholesterol. Differences were significant at P < 0.05 in at least one experiment. 3-Hydroxy-3-methylglutaryl reductase activity was decreased due to dietary garlic (P = 0.0369), but not by pharmacological levels of dietary copper (P = 0.982). The activity of fatty acid synthetase was decreased in birds fed copper (P = 0.035). Both garlic and copper supplements decreased cholesterol 7 alpha-hydroxylase activity (P = 0.024 and P = 0.022, respectively). The results of these trials confirm the findings that garlic and copper alter lipid and cholesterol metabolism. However, they do not work by the same mechanism. Feeding dietary garlic or copper for 21 d reduced cholesterol levels of broiler meat without altering growth of the chickens or feed efficiency.