This study was conducted to examine fertility in out-of-seasonal breeding using practical treatments available to sheep farm.
Thirty-three Suffolk ewes were supplemented artificial light (L, n =18) or maintained on natural daylength (N, n =15) during perinatal period (February to March). All ewes gave birth to lambs. After weaning, Seasonally anestrous those ewes were divided into following 3 groups :
Group A (L : n = 5, N : n = 6), ewes were introduced fertile ram for 38 days from May 26 ;
Group B (L : n =7, N : n =4), ewes were introduced ram similarly to group A, and given an injection of PMSG at May 26 followed 13 days later (June 8) by an injection of PMSG and PGF _2α ;
Group C (L : n = 6, N : n = 5), ewes were introduced fertile ram for 25 days from June 8, and given hormonal injections similarly to group B.
Returns to service were monitored for three consecutive cycles and this was facilitated by changing the raddle colour every 13 days.
The incidence of estrus in groups A, B and C was 45%, 82% and 36%, respectively. The incidence of estrus in group B was higher than that of group C (P < 0.05). The conception rate was identical between group A and B (45%), but that in group C was 9%. The incidence of estrus in ewes supplemented artificial light during perinatal period was higher than that in ewes maintained on natural daylength (78%, 14/18 vs. 27%, 4/15, P < 0.01). The conception rate in ewes supplemented artificial light was higher than that in ewes maintained on natural daylength (50%, 9/18 vs. 13%, 2/15, P < 0.05).
The present results suggested that Suffolk ewes raised in Hokkaido, supplemented artificial light during perinatal period (February to March), were responsive to 'male effect' in late May, and the additional hormonal treatment using PMSG and PGF₂α induced cyclic estrous activity in these ewes, which could be one of the out-of-seasonal breeding systems in practice.

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Changes in serum cortisol and serum IgG concentration were determined in the course of weaning in 7 pairs of ewes and lambs to evaluate whether early weaning is a stressor for them. Weaning for 4 pairs was carried out at lamb' age of 3.5 mo. (control) and that for 3 pairs at lamb' age of 1.5 mo. (early weaned). Determinations of serum cortisol and serum IgG were done at 30 min. before and after weaning, and thereafter, 2, 3, 6 days and 1, 3 and 6 weeks after weaning. Results were as follows : 1) For lambs, there were no significant differences in serum cortisol and IgG concentration between control and early weaned groups, and nor among periods for determination except for serum IgG at 6 weeks after weaning in early weaned lambs. This change was inferred to be caused by the establishment of immune system in early weaned lambs. 2) Ewes also showed no significant changes in serum cortisol and IgG concentration between groups and among periods except for serum cortisol concentration before weaning for ewes in control group. Results in the present study failed to explain the exact cause for this change. 3) From changes of serum cortisol and IgG concentration obtained in the present study, it is concluded that early weaning is not a stressor for ewes and lambs.

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Effects of feeding fish meal on growth, carcass characteristics and feed utilization in growing and finishing lambs during summer season were investigated. Eight cross-bred lambs composed of four castrated male and four female lambs (initial body weight : 28 kg) were used for a growth trial over 12 weeks (experiment 1). Lambs were fed grass silage (ad libitum) and concentrate diets containing rolled corn with soybean meal or fish meal at 2.5% of the body weight from middle of June to beginning of September. Castrated male lambs fed fish meal tended to grow faster and have more lean body mass than those fed soybean meal. Within the female lambs, however, there was no difference in the growth performance between lambs fed soybean meal and those fed fish meal. Other three female lambs were used for a metabolism trial in order to investigate the digestibility and nitrogen balance (experiment 2). Lambs were fed four concentrate diets (2.5% of body weight) containing soybean meal, fish meal, or soybean meal plus fish meal with glass silage (1.6% of body weight). Inclusion of fish meal in the concentrate diets did not affect the digestibility of dry matter, crude protein, acid detergent fiber and gross energy of the ration and nitrogen balance in lambs. These results indicate that feeding fish meal may improve the growth performance of castrated male lambs in summer season.

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This experiment was carried out to examine the preference of feed supplemented butyric acid and lactic acid by an applied method of a two-choice preference test and paired preference test, as a model of low and high quality in silage. Castrated sheep were fed with Italian ryegrass (at the length of 2 cm) supplemented acids of concentrations at the nine steps from 0.0375% to 9.6% (experiment 1) and at the seven steps from 0.6% to 38.4% (experiment 2). The test rations fed stepwise the concentrations from low to high with nonsupplemented ration. The percentage intake of the test rations in regard to total ration in each concentration was defined as a preference index. Preference indexes were defined under 40% as a rejection zone, from 40% to under 60% as a nondiscrimination zone, from 60% to under 80% as a weak preference zone and above 80% as a strong preference zone, respectively. In case of the test supplemented butyric acid, the preference indexes changed around at discrimination zone by supplements from 0.0375% to 2.4% of butyric acid, but ones increased by supplements of above 4.8%. The maximum preference indexes were obtained 97% at supplement of 9.6% in experiment 1 and 86% at supplement of 19.2% in experiment 2, respectively. In case of the test supplemented lactic acid, on the other hand, the preference indexes were shown weak preference at supplements of 4.8% in experiment 1 and 2, but ones changed around at discrimination zone under supplements of 19.2%. In the supplement of 38.4%, however, preference index decreased to 25% in weak rejection zone. Increase of butyric acid concentration in silage suggested not to cause the decline of preference in feed.

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Within the sheep discrimination systems adopted by Mongolia nomads, the age determination method by teeth observation was especially studied. Nomads have discriminated their own individual sheep according to their experience, and at the same time, determined the age and sex of individual sheep by means of the appearance. Beside, when discriminating individual sheep, nomads sometimes have determined the age of the sheep by observing the teeth. The age determination method of sheep adopted by nomads has been that by observing incisors of the lower jaw. The results of age determination method of sheep by teeth observation adopted by West Mongolian nomads agreed with those of the method adopted in Japan for all ages except for the age of the third and fourth calendar year.

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