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The objective of this experiment was to characterize the relationship between growth and skeletal development in commercial broilers as a function of both age and BW. From hatch through 43 d, birds were randomly selected weekly from the same commercial flock for measuring BW, tibia, and femur characteristics. Final BW was 1.8 kg for females and 2.1 kg for males. The fat-extracted weight of the tibia and femur increased proportionately with BW through 43 d of age. Length and width measures as a proportion of their final values at 43 d increased more rapidly than relative changes in BW. The length of the femur as a function of BW reached a plateau at 1.5 kg (35 d of age), whereas the length of the tibia did not plateau through 43 d of age. Differences in width measures between the two long bones were not apparent as BW increased through 43 d of age. The ash percentage of the diaphyseal region (mid-10% of bone) was consistently greater in the tibia than the femur from 15 to 43 d (P < or = 0.05). Differences in mineralization rates and growth characteristics suggest that the functionality and integrity of the femur should not be assumed solely from tibia measurements.

Previous research has shown that a line (F) of turkeys selected long-term for increased 16-wk BW was more susceptible to challenge with washed Pasteurella multocida (PM) than a randombred control line (RBC2), the base population of the F line. Published research indicated that the mortality of the F line following challenge with PM was similar to that of two commercial sire lines. The purpose of the present study was to determine the influence of reducing BW of the F line to that of the RBC2 line by nutrient restriction on resistance to PM. Four challenge trials were conducted over a 2-yr period. The BW of a group of F line birds was restricted to that of the RBC2 line by limiting access to feed from 1 to 6 wk of age. The F line restricted birds and full-fed RBC2 and F line birds were challenged with a field isolate of washed PM (1.2x10(7) organisms/bird of capsular serogroup A and somatic serotype 3, 4) at 6 wk of age. Birds were checked twice daily for 14 d. Resistance to PM was measured by days to death of those that died and percentage mortality. The BW of the restricted group of the F line did not differ from full-fed RBC2 birds for males or females. In males, the restricted F line birds had similar mortality (48.0%) to the full-fed RBC2 line birds (44.3%), and the mortalities in both groups were significantly lower than that observed for the full-fed F line birds (81.3%) following challenge with PM. The mortality following challenge in females did not differ significantly among groups, even though mortality of the full-fed F line birds (64.1%) and restricted F line birds (63.3%) was more than 9% higher than that (54.2%) observed for the full-fed RBC2 line birds. Days to death was not a sensitive indicator of resistance to PM, as no differences among the three groups of birds were observed for either sex.

Turkey hens from two BW groups (which averaged 11.8 and 12.9 kg, Normal and Heavy, respectively) were photostimulated at either 29 or 31 wk of age to determine how changes in egg weight and egg component weights with hen age affect subsequent embryonic growth and yolk sac lipid mobilization. At 2-wk intervals during the first 10 wk of lay, all eggs were collected, individually weighed, and incubated. A subsample of eggs from each photostimulation (PS) age and BW group were randomly selected for yolk and albumen weight determinations and embryo weight, liver weight, and yolk sac measurements at 21 and 25 d of incubation. Yolk and yolk sac lipid measurements were done on similar sized eggs selected at 4 to 6 and 12 to 14 wk after PS. Yolk-free embryo weight, liver weight, and yolk sac weight at 21 and 25 d of incubation increased during the first 10 wk of lay. Neither hen age nor BW at PS had any consistent effects on yolk-free embryo weight, liver weight, or yolk-sac weight. When similar-sized eggs (80 to 85 g) were selected for analyses, yolk lipid content did not change with hen production age. The lipid content of the yolk sac was 0.97 g greater in 21-d embryos from hens 12 to 14 wk after PS than from hens 4 to 6 wk after PS. Differences in yolk sac residual lipid and lipid subclass characteristics were not evident after 25 d of incubation. In conclusion, hen BW at PS or age at PS had minimal affects on embryonic growth during the last week of incubation, and most differences in embryonic growth were attributed to differences in yolk sac lipid mobilization between hen production ages independent of egg size.

Turkeys from two BW groups (which averaged 11.8 and 12.9 kg, Normal and Heavy, respectively) were photostimulated at either 29 or 31 wk of age to determine what effects age-associated changes in hen carcass characteristics, egg weight, and egg components have on subsequent poult weight at hatching during the first 10 wk of production. Carcass measurements were determined from a subsample of hens 3 wk after photostimulation (PS). Subsamples of eggs from each PS age and BW group were selected for yolk and albumen measurements. All other eggs from these hens were individually weighed and incubated at 2-wk intervals during the first 10 wk of lay (4 to 14 wk after PS). All incubated eggs were reweighed at 25 d (transfer) and poults were individually weighed at hatch. Hen BW at PS had no effect on ovarian weight and follicular size or number 3 wk later. Hens photostimulated at 31 wk had 18.7 g heavier ovaries 3 wk after PS than hens photostimulated at 29 wk (P < or = 0.06), primarily due to one additional follicle of > or = 20 mm (P < or = 0.04). During the first 10 wk of lay, egg weight increased 7.8 g, 4.4 g of which was due to increased yolk weight. Eggs from Normal BW hens weighed significantly less than those from Heavy BW hens only when hens were subjected to PS at 29 wk. Egg weight at transfer relative to egg weight at set was significantly increased from hens 4 to 6 wk after PS compared with the four older production ages (6 to 8, 8 to 10, 10 to 12, and 12 to 14 wk after PS). There was a significant increase in poult weight with increasing hen production age but no changes in poult weight relative to egg weight at set. In conclusion, hen BW at PS had minimal effects on egg component weights and subsequent poult weight at hatching.

The independent effects of age and body weight (BW) on photostimulatory response in turkey breeder hens were studied by measuring changes in plasma luteinizing hormone (LH; ng/mL) before and 3 d after photostimulation. The study was conducted with hens from two BW groups at 24-25, 27-28, and 31-32 wk of age. There was approximately a 1-kg difference in BW between groups within an age. Six hens per BW and age group were cannulated (jugular vein) and serially sampled during each of two 6-hr periods. Samples were collected at 10-min intervals. The two sampling periods were the last 6 hr of the short-day photoperiod (SD) and the same period during the third long day after photostimulation (LD). The photostimulatory response (PR) or difference between the SD and LD baseline LH concentrations was greatest in the 24-25-wk-old hens. The PR was unaffected by hen BW at any age. The baseline LH concentration during the SD photoperiod declined as hens aged. After photostimulation, baseline LH and LH peak amplitude concentrations were higher in 24-25-wk-old hens compared with the older ages. The number of LH peaks increased after photostimulation, but there were no significant effects attributable to age or BW within an age. In conclusion, the PR was affected by hen age but not hen BW or BW within a particular age.

The objective of this experiment was to study age and diet effects on serial growth of economically important carcass parts of Nicholas (NIC) and Hybrid (HYB) toms. At approximately 14-d intervals from 16 to 82 d, BW and the weight of selected carcass parts were compared in toms from both commercial strains. There were no overall strain differences in BW, although NIC toms were heavier from 31 to 72 d, which resulted in a significant strain by age interaction (P < or = 0.021). The absolute weight of the Pectoralis major (PMAJ; P < or = 0.022) and tibia plus associated muscles (Drum; P < or = 0.051) were increased in NIC toms. The relative weight of the PMAJ (P < or = 0.004) and abdominal fat (72 and 82 d; P < or = 0.023) also were heavier in NIC toms. The relative weight of the drum and Gastrocnemius muscle (GAS-TROC) was heavier in HYB toms, however (P < or = 0.001). A separate set of HYB poults was fed a diet deficient in protein or lysine (PD) from 0 to 8 wk and their growth and carcass development were compared with those fed a Control diet (NRC, 1984). Comparisons also were made at approximately 14-d intervals from 16 to 125 d. The PD diet from 0 to 8 wk significantly reduced BW and absolute breast muscle and leg portion weights. The relative weight of the PMAJ and Pectoralis minor (PMIN) were also reduced in toms fed the PD diets but the thigh and drum (125 d) were increased.

Body weight and carcass components were measured from 14 to 145 d in Nicholas (NIC) and Hybrid (HYB) strain turkey hens. At most ages, BW of HYB hens was greater than that of NIC and there were small but significant differences in the weight of the Pectoralis minor (PMIN). The relative weight of the PMIN increased in HYB hens from 98 to 145 d. No strain differences in either the absolute or relative weights of the Pectoralis major (PMAJ) were observed. The absolute and relative weights of the tibia plus associated muscles (DRUM) and femur plus associated muscles (THIGH) were significantly heavier in HYB hens. The same was true for the Gastrocnemius muscle (GASTROC). The relative weight of the abdominal fat pad (ABFAT) was significantly increased in NIC hens compared with HYB hens from 70 to 145 d. There was a linear relationship between the relative weight of the PMAJ and BW in hens from both strains (NIC, r2 = .69; HYB, r2 = .51). The relationship between the relative weight of the PMIN and BW was best described with a quadratic model but the r2 in both strains was considerably lower than that for the PMAJ (NIC, r2 = .26; HYB, r2 = .36). The linear relationship between BW and the relative weights of the THIGH and DRUM was negative and positive for ABFAT.

Growth and carcass development measures were compared in turkey hens from a line selected for egg production (E line) and a line selected for BW at 16 wk (F line). Hens in both lines reached their maximal BW 4 wk after photostimulation. Maximal BW in F line hens was 20% greater than their respective BW after 89 days of production compared with only a 12% difference in E line hens. In both lines, there was a decline in BW through 49 days of production but no further decreases at 89 days. The same trend was observed for both the absolute or relative weights of the abdominal fat pad. The weight of the oviduct was near maximal size in E line hens near the onset of production, whereas it continued to increase in size in F line hens through 49 days of production. The same was true for liver weight in F line hens, whereas in E line hens liver size continued to increase throughout the experiment. Carcass DM and lipid were higher and carcass protein lower in F line compared with E line hens near the onset of lay. In a second experiment, heavy weight hens were fed the standard Ohio Agricultural Research and Development Center breeder diet or a diet with supplemental fat and increased ME. There were no significant diet effects on BW or egg production, but hens fed the high-fat, high-energy diet did have increased carcass protein (percentage DM; P < .08).(ABSTRACT TRUNCATED AT 250 WORDS)

1. Divergent selection for body weight resulted in significant increases and decreases in body weight and the relative weight of the pectoralis major breast muscle in heavy (HW) and light weight (LW) strains of Japanese quail compared with a randombred control strain (R1). 2. The relative weights of the abdominal fat pad and total carcass lipid were increased in the HW strain, particularly in the females. 3. Sexual maturity was similar in HW and R1 hens but was delayed in the LW hens. HW hens laid significantly more double-yolked eggs.

1. Selection for body weight in Japanese quail has altered the protein requirements for growth and reproductive development in the selected line and randombred control population from which it was developed. 2. In both the selected and randombred lines, the protein requirement for growth is different from that for maximal reproductive development.

Body weight and carcass component weights of turkeys from a growth-selected line (F), a randombred control population (RBC2), and a commercial sire line (C) were compared at hatch, 4, 8, 12, and 16 wk of age. At hatch there were no significant differences in BW between the F and RBC2 lines, but the C line poults weighed significantly less than the F line poults. Total Pectoralis muscle weight of the F line was larger than for Lines C and RBC2 at hatch, but there were no line differences in drum weight or length. The F line was still heavier than the other lines at 4, 8, and 12 wk, but the absolute and relative weights of the Pectoralis major (P. major) muscle were larger in the C line than the other lines at all ages. Selection for BW increased the weight of the P. major in the F line compared with the RBC2, but differences in the relative weight of the muscle were not consistent. The large line differences for the absolute and relative weight of the P. major were not observed for the Pectoralis minor. At all ages, the lengths of the tibia and femur were greater in the F line than the other lines. At 4 and 8 wk, bone length in the C line was greater than the RBC2, but at 12 and 16 wk there were no significant differences between these lines. The fast-growing F and C lines had more abdominal fat than the RBC2 at 16 wk of age.

Broiler breeder cockerels were reared on four feed-restriction programs from 3 to 23 wk of age (Experiment 1). Excessive BW restriction (85% of the controls) throughout rearing significantly decreased fertility at 28 wk of age, but not at 31 or 35 wk of age. There were no carryover treatment effects on BW at 30, 35, or 45 wk of age. Significant peaks occurred in the concentration of the serum luteinizing hormone (Experiment 1, 7.05 ng per mL; Experiment 2, 7.36 ng per mL) at 33 to 35 wk of age.

The relationship between body weight gain, nutrient intake, and skeletal and muscle growth in broiler breeder pullets was studied in two experiments. A total of 720 and 540 pullets were started in Experiments 1 and 2, respectively. In the first study, growing pullets were fed either a 15% protein, 2,885 kcal ME/kg pullet grower diet or a 23% protein, 3,133 kcal ME/kg broiler starter diet from 2 to 16 wk of age. Within each dietary treatment, there were three body weight groupings (light, control, heavy) achieved by manipulating weekly feed allowances. At 8, 12, and 16 wk of age, 12 pullets from each diet and body weight grouping were killed for muscle [pectoralis major] and skeletal (shank, keel, tibia, clavicle) measurements. As body weight increased, so did skeletal growth, but there were no significant differences in skeletal measurements related to diet. At 12 and 16 wk of age, pullets fed the broiler starter diet had significantly larger p. major muscles. In Experiment 2, growing pullets were fed restricted diets: 1) the 15% protein grower diet (control), 2) the broiler starter diet adjusted weekly to the same calculated calorie intake as that obtained with the grower diet (broiler starter calorie), or 3) the broiler starter diet adjusted to the same calculated protein intake as the grower ration (broiler starter protein). At 16 wk, there were no significant differences between body weight or skeletal measurements of the control and broiler starter calorie treatments. Pullets in the broiler starter calorie treatment did have significantly larger pectoralis muscles and less abdominal fat than those fed the 15% grower diet. Pullets in the broiler starter protein treatment were significantly lighter and had shorter bones, less abdominal fat, and smaller p. major muscles than those in the control treatment.

The relationship between dietary energy and protein and their interaction with method of restriction and environment were studied. In Experiment 1, two isocaloric diets (2750 kcal/kg) formulated to contain either 13.5% or 15.5% protein were fed to broiler breeder pullets from hatching through 21 weeks of age. There were no significant differences in body weight due to dietary protein but chicks fed the 13.5% protein ration did require a significantly greater quantity of feed to produce an equivalent body weight. Sexual maturity, peak egg production, and egg size were not affected by the level of dietary protein but total egg production was significantly decreased in pullets fed the 13.5% protein diet. In Experiment 2, 2970 kcal/kg ration containing 15.5% protein was fed to pullets that were reared under two different lighting environments, natural daylength or 24 hr light for the first 7 days and 8 hr light per day thereafter. Pullets housed in the controlled environment and reared on an every-other-day restriction program had significantly improved feed utilization compared with similarly restricted birds kept under natural light. Environmental effects on feed utilization were not as great in the every day restriction treatment. Chicks exposed to natural daylight and fed 15.5% protein diets had similar caloric efficiencies (kcal/g) at 15 weeks of age in both experiments despite dietary density differences of 220 kcal/kg. This supports a hypothesis that above some minimal level of protein intake, caloric intake has the greatest control over body weight gain in restricted pullets, particularly where every-other-day feeding is used during part of the growing period.

An abstract of the article "The effect of selection for body weight along at 16 weeks on the lysine and TSAA requirement of turkeys," by O.C. Aimiuwu and colleagues is presented.