Studies were conducted to evaluate growth-promoting effects of testosterone in male turkeys by using castration and testosterone repletion. In three experiments, factorial arrangements with two main effects, testosterone implants and gonadal status, were incorporated, and body weights, shank length, feed consumption, and serum testosterone concentrations were measured until 20 weeks of age. Testosterone was implanted as cholesterol-based pellets at ages of 9 weeks (15.0mg/kg body weight), 13 weeks (15.6mg/kg body weight), or 11 weeks (10.1 and 20.0mg/kg body weight) in Experiments 1, 2, and 3, respectively. Castration was performed about 10 days before implants were placed. The release of testosterone from the pellet into blood circulation was immediate with a half life of 2.8 days. When implanted at 9 weeks of age (Experiment 1), the rate of weight gain was increased (P≤0.05) by testosterone, during the period of 9 to 12 weeks and decreased (P≤0.05) by castration during the period of 16 to 20 weeks. When implanted at 13 weeks of age (Experiment 2), the rate of weight gain during the period of 13 to 16 weeks was increased (P≤0.05) by testosterone. When testosterone was given at graded doses (Experiment 3), the rate of weight gain was increased quadratically (P≤0.05) by testosterone during the first 3-week period and decreased (P≤0.05) by castration during the period of 16 to 20 weeks. The overall rate of wieght gain, from 11 to 20 weeks, was increased quadratically (P≤0.05) by testosterone and decreased (P≤0.05) by castration. The feed: gain ratio was improved (P≤0.05) by testosterone treatment for the first three weeks, but not for the entire experimental period.

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Effects of castration and testosterone implants on carcass yield, carcass conforma-tion, body composition, and chemical composition of edible meats in male turkeys were determined. A2×2 factorial arrangement of treatments with testosterone implant and castration was incorporated in experimental design. Male turkeys were castrated at 9.5 weeks of age and implanted with testosterone pellets at 20mg/kg body weight at 11 weeks of age. Six turkeys from each treatment were killed at 21 weeks of age to determine the carcass quality and the chemical composition. The yield of eviscerated carcasses was increased (P≤0.05) by testosterone treatment (T), but not affected by castration (C). Abdominal fat was reduced (P≤0.05) by T, but not affected by C. The amount of skin was incresed (P≤0.05) by T and decreased (P≤0.05) by C. The wing yield was reduced (P≤0.05) by T and increased (P≤0.05) by C. The part and lean yields were not affected by either T or C with the following exceptions. The lean yield of breast was increased (P≤0.05) by T and the part and lean yields of drumsticks were reduced (P≤0.05) by C. Body composition was affected (P≤0.05) by T, but not by C. The moisture content was increased (P≤0.05) by T. The chemical composition of breast, thigh, and drumstick was not affected by either T or C with an exception that the moisture content of breast meat was increased (P≤0.05) by T.

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To determine the effects of testosterone and 17β-estradiol on female turkey growth, 36 female turkeys were ovariectomized and 36 female turkeys were sham-operated at 11 weeks of age in Experiment 1 and at 15 weeks of age in Experiment 2. One week after surgery, turkeys were implanted with pellets containing either placebo, testosterone or 17β-estradiol at the dose of 8.2mg/kg body weight at 12 weeks (Experiment 1) or 10.8mg/kg body weight at 16 weeks (Experiment 2). Turkeys were weighed weekly and body composition was determined at 21 weeks of age. Ovariectomy increased (P≤0.05) the growth rate when performed at 15 weeks, but not when performed at 11 weeks. 17β-Estradiol had no effects on the growth rate, whereas testosterone decreased the growth rate when implanted in turkeys at 16 weeks of age. Steroid implants interacted with ovariectomy to affect body composition in Experiment 1, in which 17β-estradiol reduced (P≤0.05) the moisture content and increased (P≤0.05) the fat content in intact female turkeys, but not in ovariectomized turkeys. Results in this study related 17β-estradiol only to body fat accumulation and ovarian development to the growth pattern characteristic to female turkeys.

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The rapid growth pattern of ovarian follicles in laying quail was examined during the period from 2 to 10 months of age by the use of three kinds of the fat soluble dye. The rapid growth period length was longest at 2 months of age and shortest at 4 months of age. The period then tended to lengthen slightly with age. A continuous increase in follicular volume at the time of ovulation was found as age progressed. The number of growing follicles in ovary was relatively small from 2 to 6 months of age, then the number increased at 8 months of age. The total amount of daily yolk deposition increased from 2 to 8 months of age.
To clarify relation between the follicular growth pattern and the laying performance, quail were classified into three types according to their laying patterns. In both of type A, exhibiting relatively short clutches, and type B, showing long clutches, the growth period was longest at 2 months of age. On the other hand, the number of growing follicles in ovary remained a constant level in type A while increased gradually in type B as age progressed. The birds of type C laid their eggs around the clock regardless of the lightdark cycle with relatively long clutches. The growth period in this type increased basically with age, but the number of growing follicles continued to decrease until 6 months of age. The follicular volume at ovulation and the total amount of daily yolk deposition tended to increase as age advanced in all the laying types. The follicular growth period and the follicular volume at ovulation in the quail of type B were less than those of type A at the all ages examined. However, the total amount of daily yolk deposition in type B was large comparing with type A and C.

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Four mathematical models (compartmental (C), modified compartmental (MC), Wood (W), and Adams-Bell (AB)) were fitted to different patterns of egg production data in laying hens to compare the fits of these models.
The egg production data were obtained from the two lines which were founded on a basis of divergent selection for egg quality traits. Egg production data of individual hens were classified in six patterns. The average hen-day rates of lay were calculated for every 10 days from the first egg for each pattern. The comparison of fits was based on the R2 adjusted for degrees of freedom and Akaike's information criterion (AIC).
The fits of C, MC and AB models were similar for the egg production data showing a general pattern of curve. However, the model parameters could not be estimated by these three models for the data whose patterns showed abrupt decreases after the peak of egg production. The data in which the period from the first egg to the peak of egg production was short and linearly decreased after reaching the peak showed poor fits of the models. The parameters of all patterns could be estimated by the W model, but the fits were lower than those of the others.

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Genetic parameters for body weight at 256 days (BW), age at first egg (SM), egg weight at 252 days (EW) and egg production efficiencies between 169-280 days (EPA) and between first egg and 280 days (EPB) were estimated in five layer chicken lines selected at the National Livestock Improvement Center, Okazaki Station, between 1986 and 1994. The lines were three White Leghorn lines (E1, E4 and S46), one recessive White Rock line (L17) and one Rhode Island Red line (Y8). Parameters were estimated by restricted maximum likelihood procedure under the expectation maximization algorithm using multiple trait animal models. The model included year and house as fixed effects, inbreeding as a covariate and random additive genetic effects.
Estimates of heritability differed slightly between lines and, for BW, SM, EW, EPA and EPB were between 0.51-0.65, 0.35-0.47, 0.51-0.60, 0.13-0.19 and 0.20-0.27 respectively with weighted average heritabilities of 0.58, 0.44, 0.56, 0.17 and 0.23 respectively. Genetic correlations between EPA and EPB were expectedly high at between 0.80 and 0.93 while the genetic correlations between these two traits and the other traits were low and negative except with BW where the correlations were low but positive. Estimated heritabilities and, especially, the correlations were different among lines and from those assumed at the station for making the desired gain indices which indicates the importance of estimating variance and covariance components in each line for use in making selection decisions.

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The effect of cecal ligation on nitrogen (N) utlization (N balance/N intake) and N excretion was investigated in chickens fed on a 10% protein diet or a 10% protein diet plus urea. Daily intake of dietary protein and added urea were 560 and 280N mg per kg body weight, respectively. The ligation of ceca tended to increase N utilization in chickens fed on a 10% protein diet but to decrease it in those fed on the 10% protein diet plus urea. In the ceca-ligated chicken uric acid excretion and ammonia excretion significantly decreased in both dietary groups (P<0.05), but urea excretion increased in chickens fed the 10% protein diet plus urea (P<0.05) to more than 4 times control level (P<0.05) and tended to do so in those fed the 10% protein diet. Blood ammonia, urea and uric acid concentrations were not affected by cecal ligation in either chickens fed the 10% protein diet or the 10% protein diet plus urea. The results suggest that the Ligation of ceca affects N utilization and N excreetion in chickens fed a moderate protein diet in similar manner to those fed a low protein diet except the utilization of dietary urea.

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The growth and production of meat in 3 breeds of ducks, i.e. Mallard, Cherry valley and their crossbred (F₁) were compared in order to select breeds more profitable for paddy rice cultivation using ducks. Three paddy fields were used for this study and 8 ducklings on the 1 st day posthatching were allocated to each paddy field (4.5a) at the 1 st week after rice-planting. The animals were kept until 11 weeks of age in the paddy fields, and then fattened with feed formula for layer in pens until 20 weeks of age. Three control groups (3 breeds) each consisting of 8 ducks were housed and provided with the same feed formula as above. The results obtained were as follows:
1. Final body weight at 20 weeks of age tended to be greater in the order, Mallard, F₁, Cherry valley for both free-ranged and housed ducks.
2. Free-ranged Cherry valley had a tendency to be slower in overall growth rate than housed animals, however the overall growth rates of free-ranged Mallard and F₁ did not differ from those of housed animals.
3. There were no significant differences in dressing percentage of ducks among breeds and between free-ranged and housed conditions. Abdominal fat showed a tendency to be more in the order, Mallard, F₁, Cherry valley.
4. The results of sensory test suggested that F₁ meat was most palatable and Cherry valley least.
5. The results of the present study suggested that F₁ meat was most profitable in the 3 breeds of ducks for paddy rice cultivation using ducks

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