Nutritive value of poultry by-product meal. 1. Metabolizable energy values as influenced by method of determination and level of substitution.

Experiments were conducted to determine the metabolizable energy (MEn) of eight poultry by-product meal (PBPM) samples. Samples averaged 5.44% moisture, 4.84 kcal gross energy (GE)/g dry matter (DM), 61.2% crude protein, 13.38% ether extract, 16.1% ash, 5.14% calcium, and 2.36% phosphorus. Samples of PBPM were substituted in the diet at levels of 20 and 40%. Values of ME were calculated with substitution for the diet (Matterson's method) and for glucose (Hill's method) and by the fasted cockerel method. Values of PBPM MEn were 7.9% greater when substitution was for diet as compared with substitution for glucose; values were 2.95 and 2.74 kcal/g DM, respectively. Using Matterson's method with three samples, MEn values were determined to be 12.1% greater when PBPM was substituted at the rate of 20% than at 40%; values were 3.33 and 2.97 kcal/g DM, respectively. Differences in MEn between the best and poorest samples (3.79 and 2.77 kcal/g DM) could be attributed to differences in gross energy (5.00 and 4.49 kcal/g DM) and percentage of gross energy metabolized (75.7 and 61.7%). Metabolizable energy was more closely related to body weight gains than the amount of feed consumed. When a modification of Sibbald's fasted cockerel technique was used, true MEn of the eight samples averaged 3.35 kcal/g DM and 69% of GE metabolized. For the three samples assayed by both methods, Matterson's method gave values averaging .97% higher than Sibbald's (+4.3, +.8, and -2.2%). Differences in MEn were mostly highly correlated with ash (-.89), calcium (-.85), and GE (.78) contents of the diets. Projections from relationships found between ME and nutrient compositions of these samples to the average sample used by the poultry industry in the Southeast indicate an average of 3.57 kcal ME/g DM of PBPM (3.39 kcal/g as is).

Correlation of protein content of feedstuffs with the magnitude of nitrogen correction in true metabolizable energy determinations.

The relationship between the protein content of feedstuffs and the magnitude of difference between corresponding true metabolizable energy (TME) and nitrogen-corrected TME ( TMEn ) was investigated. Fifty-two samples of feed ingredients, mixtures of ingredients, and mixed feeds were assayed for TME and TMEn . A positive relationship was observed between the protein content of the feed samples and the magnitude of difference between determined TME and TMEn values. The regression equation describing this relationship is Y = . 122X + 3.724, where X equals percent protein and Y the percent difference between TME and TMEn . The corresponding r2 was .60.

Comparison of heat production of chickens measured by energy balance and by gaseous exchange.

An open-circuit respiration calorimeter suitable for chickens or other small animals has been constructed. The system contains two animal chambers and is capable of determining heat production of two animals or groups of animals independently and simultaneously with gas collection apparatus for continuous sampling of chamber gases. The operation of the system was tested in two experiments by determining heat production of two groups of 10-week-old, full-fed cockerels over a 4-day period both by energy retention (body balance) and gaseous exchange. Heat production (kilocalories per bird per 24 hours) as determined by energy balance versus gaseous exchange was 359 versus 348 in one experiment and 395 versus 393 in the other. The agreement was sufficiently close to support the use of respiration calorimetry to measure heat production of chickens under experimental conditions in this laboratory without killing the experimental subjects. On the basis of metabolic body weight (in kilograms, W0.75) heat production measured in this manner was 161 and 173 kcal (day . W0.75) in experiments 1 and 2, respectively.

True metabolizable energy of fats at low level dietary inclusion.

When assayed at a 2.5% level of inclusion in a corn-soybean meal basal diet with 40 replications per treatment, no significant differences could be demonstrated between the true metabolizable energies (TME) of corn oil and two samples of tallow varying in stearic acid (18:0) content. All values were in excess of the gross energy of fat, suggesting an improvement in the absorption of other dietary constituents. When assayed at a 15% level in a purified basal diet, the TME of corn oil was significantly higher than that of the tallows; all values were below the gross energy of fat. Use of the practical corn-soybean meal basal improved the TME of the fats by 22.4% (corn oil), 34.9% (low 18:0 tallow), and 43.0% (high 18:0 tallow). A portion of the improvement in the TME of the tallows is presumed to be accounted for by an interaction with fatty acids in the practical basal ingredients that may be obscured at higher levels of inclusion. It is concluded that with adequate replication it is feasible to assay the TME of fats at low levels of dietary inclusion. A comparison of fatty acid absorption in Single Comb White Leghorn roosters during a TME study and in 8 to 9 week broilers on a full-feed regimen suggests that the conditions imposed during a TME assay provide a satisfactory model for evaluating the fat absorption of chickens reared under normal conditions.

Additive toxicity of aflatoxin and dietary tannins in broiler chicks.

In two experiments graded levels of either aflatoxin and tannic acid (experiment 1) or aflatoxin and a high-tannin variety of grain sorghum (BR-64) (experiment 2) were incorporated into broiler chick starting diets in a factorial design. When present singly, aflatoxin and both tannic acid and high tannin sorghum significantly depressed chick growth. When present in combination, and deleterious effects of aflatoxin and either tannic acid or high tannin sorghum on chick growth and feed conversion ratios were found to be additive.

The influence of widely fluctuating temperatures on heat production and energetic efficiency of broilers.

Broiler chicks 4 and 4.5 weeks of age were subjected to the following temperature regimens for the experimental periods which ranged from 18 to 24 days in three experiments: cyclic cold temperature (1.7 to 12.8 C), cyclic hot temperature (23.9 to 35 C), cyclic normal temperature (12.8 to 23.9 C), and "changing" temperature. The birds of the "chaning" temperature regimen were rotated from the hot to the cold room and back allowing three days at each temperature on each cycle so that the overall mean temperature was similar for the birds of the changing and the normal regimens during experimental periods. In one experiment three diets with different energy and protein levels were used. The metabolizable energy per kilogram and percent protein were s follows: 3200 and 20 (control diet), 3200 and 17 (low protein diet), and 2800 and 20 (low energy diet). In two other experiments either the control diet or both the control and low energy diets wereused. The response to the different diets was similar at all temperatures so that no diet X temperature interaction occurred. Heat production as a percentage of metabolizable energy intake was least for birds kept at the normal temperature, intermediate for birds subjected to the changing temperatures, and greatest for birds of the cold and hot temperatures. Also, energy gain as percentage of metabolizable energy intake was greatest for birds housed at the normal temperature. The lower energetic efficiency of birds in the changing temperature as compared to birds in the normal temperature suggested an increase in energy cost for maintaining body temperature when chicks were subjected to a widely fluctuating temperature.

Additivity of true metabolizable energy values as measured with roosters, broiler chicks and poults.

True metabolizable energy (TME) values were determined for five feed ingredients (yellow corn, dehulled soybean meal, corn gluten meal, menhaden fish meal, and poultry byproduct meal), and three combinations of these ingredients, using Single Comb White Leghorn roosters, 6-week-old broiler males (Cobb), and 6-week-old male turkey poults (Large White). There was generally good agreement in th TME values between roosters, broilers, and poults although the values for broilers tended to be slightly lower than for roosters or poults. Values for the ingredient combinations as assayed with the three classes of birds showed differences of 3% or less between "predicted" and "determined" in seven of nine comparisons, indicating a satisfactory degree of additivity of TME values for these ingredients.

Effect of diet composition on feed intake and growth of chicks under heat stress. II. Constant vs. cycling temperatures.

Broiler chicks 5 to 7 weeks of age were subjected to a constant cool (14 +/- 1 C) or hot (31 +/- 1 tc) environment and fed diets varying in fat level and energy and nutrient density. Chicks gained significantly (P less than or equal to .01) more body weight in the cool than in the hot environment. In both environments chicks fed high fat or high fat-high density diets gained more weight than those fed diets low in fat, and there was no diet X temperature interaction. When temperatures were cycled diurnally (cool, 14 to 22 C; hot, 22 to 33 C), as would occur under natural conditions, the growth depression due to heat stress was less in chicks fed the diets high in fat. The special benefit of fat at high temperature was probably the result of reduced heat increment. Under constant temperature conditions, chicks in the cool environment, pair-fed at the same level of feed intake as those in the hot environment, gained significantly (P less than or equal to .05) more weight than the latter. These data indicated that factors other than reduced feed intake contributed to the growth depression associated with high temperature. Thyroid size was significantly (P less than or equal to .05) reduced in chicks held at constant high temperature and slightly but not significantly reduced in chicks subjected to cyclic heat stress. This decrease in thyroid size suggested there is a practical limit on overcoming by nutritional means the deleterious effects of heat stress in broilers.

Some mechanisms of reduction of carotenoid levels in chickens infected with Eimeria acervulina or E. tenella.

The levels of plasma carotenoids were markedly reduced in broiler cockerels infected with Eimeria acervulina or E. tenella. The mechanisms of this depigmentation differed between the two species, being primarily associated with interference of absorption of xanthophyll (carotenoids) from the intestinal lumen with E. acervulina infection and with leakage through the damaged wall of the cecum with E. tenella infection. Chicks reared on an essentially carotenoid-free diet and inoculated with E. acervulina showed no detectable levels of carotenoids in the blood 48 hours after being changed to a diet containing 30 mg of xanthophyll/kg. Conversely, uninoculated chicks and chicks inoculated with E. tenella showed significant and similar increases in plasma levels of carotenoids. Chicks reared on a diet containing xanthophyll and inoculated with E. tenella showed a more rapid decrease in plasma carotenoids than did uninoculated controls when changed to a xanthophyll-free diet. In chicks fed high xanthophyll diets containing chromic oxide, no indication of malabsorption was seen in chicks infected with E. tenella compared with uninoculated controls, whereas chicks inoculated with E. acervulina showed significantly less xanthophyll absorption. Conversely, a marked increase in the xanthophyll : Cr2O3 ratio was observed in the cecal contents of chicks inoculated with E. tenella compared with uninuoculated controls or those inoculated with E. acervulina. Studies of uninoculated chicks pair-fed with chicks inoculated with E. acervulina or E. tenella indicated that the decrease in plasma carotenoids and increases in intestinal pH are not associated with the reduced intake of feed associated with infection. The studies involving uninoculated birds with reciprocal chagnes between high and low xanthophyll diets indicated that plasma carotenoids are a more rapid and sensitive means of measuring changes in pigmentation levels than are visual skin scores carotenoid levels from the skin.

The effect of methionine and lysine levels on the arginine requirement of the chick.

Two breeds of commercial broiler chicks were used to investigate possible breed differences and to determine the effect of methionine and lysine on arginine requirements. Graded levels of arginine were added to a glucose-casein diet with or without added methionine and to a corn-soybean meal diet with and without added lysine and/or methionine. The arginine requirement of chicks receiving the glucose-casein diet with and without supplemental methionine was found to be 1.46 per cent and 1.55 per cent of the diet, respectively. No breed differences were found. When arginine was added to a corn-soy diet containing 1.53 per cent arginine, with or without supplemental methionine, no response was obtained indicating that this level of arginine was adequate. When this diet was supplemented with lysine to bring it up to the lysine level of the casein diet, a growth depression occurred which was overcome by the addition of 0.20 and 0.25 per cent arginine, respectively, in the absence and presence of supplemental methione. These levels of arginine exceeded the requirements determined for chicks fed the glucose-casein diet. In chicks fed the glucose-casein diet, muscle creatine increased with each level of added arginine with or without supplemental methionine. Creatinine excretion also increased with each level of added arginine in the absence of supplementary methionine but when methionine was added creatine excretion reached a plateau at the level of arginine which satisfied the chick's growth requirement.