A study was conducted with an exogenous monocomponent protease added to corn-soybean meal diets fed to straight-run Ross 708 broilers from 7 to 22 d of age. Broilers were randomly placed into 42 battery pens (5 birds/pen) and allocated to 6 treatments with 7 replicates. A positive control diet (PC; 22.5% CP) and a low protein basal diet (20.5% CP) were formulated. Low protein diets (LP) comprised 98.67% of low protein basal diet and 1.33% Celite (indigestible marker and filler; Celite Corp., Lompoc, CA). Protease [75,000 PROT units/g; 1 PROT unit is defined as the amount of enzyme that releases 1 µmol of p-nitroaniline from 1 µM of substrate (Suc-Ala-Ala-Pro-Phe-p-nitroaniline per minute at pH 9.0 and 37°C] was added at the expense of Celite (0 mg/kg, LP0; 100 mg/kg, LP100; 200 mg/kg, LP200; 400 mg/kg, LP400; and 800 mg/kg, LP800) to create the LP diets (20.25% CP). At 22 d of age, ileal contents were collected from all birds for apparent CP and amino acid (AA) digestibility determinations. Broilers fed the PC diet were 7.5% heavier (P < 0.05) compared with those fed the LP0 diet. Birds fed the LP diets containing protease regardless of concentration grew as well as the birds fed the PC diet. Feed conversion was impaired (P < 0.05) in birds fed the LP0 and the LP100 diets compared with those fed the PC diet, but no difference was found between birds fed the PC diet and those fed diets containing more protease (LP200, LP400, and LP800). Digestibility of CP was increased (P < 0.05) in broilers fed the LP-supplemented diets compared with those fed either the PC or LP0 diets, but it was similar between those fed LP diets with any protease concentration. Digestibility of AA was not different between the PC and LP0 diets. The protease used in this study restored live performance and digestibility of CP (6.1%). When benefits in AA digestibility occurred, they were similar at all protease inclusions and averaged as follows: Arg, 3.5%; Ile, 3.2%; Lys, 5.4%; Thr, 7.8%; Asp, 6.5%; His, 3.3%; Cys, 4.6%; and Ser, 5.5%. Methionine was increased only at 400 and 800 mg/kg (6.5%) and Val was increased only at 200 and 800 mg/kg (5%).

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The weight of hatching eggs can influence broiler live performance regardless of hen age. Egg composition is altered with egg weight, but such alterations do not seem to have major effects on broiler growth and processing yields. The chick hatches with a yolk sac which provides nutrients for the transition to independent feeding. Alterations in egg weight and composition do not affect the proportion of yolk sac to body weight as much as its composition, particularly with eggs from very young hens. The contents of the yolk sac are high in fat and protein but very low in carbohydrate, which could lead to ketosis with prolonged fasting. Enhancing the first feed with either carbohydrate or gluconeogenics such as propionic acid may alleviate this ketosis and help early development. The digestive system of the chick is physically complete at hatching but is not fully competent at nutrient retrieval as many enterocytes are orientated to immunoglobulin uptake. Villi length and enzymatic activity increases with feeding, reaching maturity within a few weeks. Access to food and water after hatching varies, and long delays until placement are common. These delays cause losses in live performance. Loss in body weight due to late placement or undernutrition may also affect early muscle development. These adverse effects extend to marketing age and reduced meat yield. Factors that affect early chick development are gaining interest as the length of time to market progressively decreases and the chick's first days represent an increasing proportion of the total time for production. ReferencesALLBROOK, D.B., HAN, M.F. and HELLMUTH, A.E. (1971) Population of muscle satellite cells in relation to age and mitotic activity. Pathology 3: 233-243 AMBROSEN, T. and ROTENBERG, S. (1981) External and internal quality and chemical composition of hen eggs as related to hen age and selection for production traits. Acta Agricultura Scandinauica AUSTIC, R.E. (1985) Development and adaptation of protein digestion. Journal of Nutrition 115: BAKHUIS, W.L. (1974) Observations on hatching movements in the chick (Gallus domesticus). Journal of Comparative Plzysiology and Psychology 8 7 997-1003 BARANYIOVA, E. (1972) Influence of deutectomy, food intake and fasting on liver glycogen content in chickens after hatching. Actn Veterinaria Brno 41: 149-159 BARANYIOVA, E. and HOLMAN, J. (1976) Morphological changes in the intestinal wall in fed and fasted chickens in the first week after hatching. Acta Veterinaria Brno 45: 151-158 BELLAIRS, R., BACKHOUSE, M. and EVANS, R.J. (1972) A correlated chemical and morphological study of egg yolk and its constituents. Micron 3: 328-346 BEST, E.E. (1966) The changes of some blood constituents during the initial post-hatching period in chickens. 11. Blood total ketone bodies and the reduced glutathione/ketone body relationships. British Poultry Science 7 23-28 BIELORAI, R., TAMIR, M., ALUMOT, E., BAR, A. and HURWITZ, S. (1973) Digestion and absorption of protein along the intestinal tract of chicks fed raw and heated ...

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Two experiments were conducted to evaluate the prevalence and severity of white striping (WS) and wooden breast (WB) in breast fillets from broilers fed diets with increasing digestible Lysine (dLys) from 12 to 28 d (Exp. 1) and from 28 to 42 d (Exp. 2). Trials were sequentially conducted using one-d-old male, slow-feathering Cobb 500 × Cobb broilers, both with 6 treatments and 8 replicates. Increasing dLys levels were equally spaced from 0.77 to 1.17% in Exp. 1 and from 0.68 to 1.07% in Exp. 2. The lowest dLys diet was not supplemented with L-Lysine (L-Lys) in either one of the studies and all other essential amino acid (AA) met or exceeded current commercial recommendations such that their dietary concentrations did not limit broiler growth. Four birds per pen were randomly selected from each replication and processed at 35 and 42 d in Exp. 1 and Exp. 2, respectively. Deboned breast fillets (Pectoralis major) were submitted to a 3 subject panel evaluation to detect the presence of WS and WB, as well as to provide scores of WS (0-normal, 1-moderate, 2-severe) and WB (0-normal, 1-moderate light, 2-moderate, 3-severe). Increasing the level of dLys had a positive effect on BW, carcass, and breast weight, as well as breast yield. White striping and WB prevalences were 32.3 and 85.9% in Exp. 1 and 87.1 and 89.2% in Exp. 2. Birds fed diets not supplemented with L-Lys had the lowest average WS and WB scores (0.22 and 0.78 in Exp. 1 and 0.61 and 0.68 in Exp. 2). White striping and WB presented linear responses to performance variables in Exp. 1, whereas quadratic responses were observed for all variables in Exp. 2. In conclusion, increasing the level of dLys improved growth performance and carcass traits as well as induced the occurrence and severity of WS and WB lesions.

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An experiment with 1,440 male Cobb 500 and 1,440 male Ross 308 broilers (14 to 35 d of age) was conducted to investigate the effects of diets having 4 levels of digestible methionine plus cysteine (SAA) on various performance criteria at 2 dietary protein levels (20.5 and 26.0%). Two corn-soybean meal/poultry by-product basal diets were formulated to contain 3,060 kcal/kg MEn and either 20.5 or 26.0% balanced protein, and 1.12 and 1.46% digestible (according to table values) lysine, respectively. Except for SAA, the ratios between essential amino acids were kept identical in both diets according to the ideal protein concept. The ratio between digestible SAA and digestible Lys was 50%. All remaining nutrients met or exceeded NRC (1994) recommendations. Graded levels of SAA were supplemented to obtain digestible SAA to Lys ratios of 62, 69, and 77%, with 77% representing an optimized amino acid balance. Increasing the protein level clearly improved weight gain, feed conversion, breast meat yield, and abdominal fat content. Increasing SAA levels resulted in strong nonlinear or linear dose responses at both protein levels and for both strains. Regression analysis suggested that reducing digestible SAA in a balanced protein (diets with SAA:Lys of 77%) impairs performance, and that optimum SAA:Lys ratio for growing broilers might be higher than 77%, although ANOVA revealed no significant improvement with an SAA:Lys ratio higher than 69%. Responses provide evidence that optimum dietary SAA level depends on dietary protein level and should therefore be related to the protein content.

Broiler chicks from one incubator hatch within long periods of time, which leads to dehydration and reduction in yolk sac reserves of those chicks that have hatched earlier and potentially impairs early performance. The present research investigated the hatching distribution at intervals of incubation using eggs of different weights within one breeder age or eggs from widely different breeder ages. Eggs from breeders at 27 and 59 weeks of age (54 and 69 g) and from breeders at 40 weeks of age, which were graded as light (58 g) and heavy (73 g), were placed in a commercial incubator. There were a total of 1,184 eggs distributed in four treatments and eight replicates: eggs from 27-week-old breeders (27B), eggs from 59-week-old breeders (59B), light eggs from 40-week-old breeders (40BL) and heavy eggs from 40-weekold breeders (40BH). Replicates were comprised of 37 eggs that were placed in each incubator tray. The treatments were physically separated from each other using a plate. Eggs were transferred to a hatcher after 432 hours of incubation and the first chick hatched at 449 hours of incubation. Afterwards, the number of completely hatched chicks from each replicate was recorded at six-hour intervals until 503 hours of incubation, when the hatchings stopped. Hatched chicks were removed from the trays after each measurement. Data were submitted to an analysis of variance with repeated measures. There was a significant interaction between breeder age and incubation length. The hatching onset of eggs from the old breeders was later compared to young breeders. Hatchability (%incubated eggs) was lower for the old breeders; however, differences in hatchability as a percentage of the hatched eggs were not so evident. Complete hatchability occurred only at 503 hours of incubation; however, more than 90% eggs had hatched 18 hours earlier.