To study the effect of isolation of lambs on serum cortisol concentration, 2 pairs of twin lambs were weaned at 90 days of age, and isolated by dividing the paddock with a wire screen at 97 days of age. In addition, at 100, 130 and 160 days of age, they were visually isolated from each other with a solid plywood fence. Blood samples for cortisol analysis were collected from jugular vein at 30 minutes before and after each of the occasion. Results were as follows : 1) The weaning or at physical isolation has no significant effect (P > 0.05) on the serum cortisol concentration with a tendency of an increased level of concentration after weaning and the isolation. It is, therefore, assumed that taking ewes out of the flock or setting up of wire fence may not cause an appreciable stress on weaned lambs. 2) At 100 days of age, the visual isolation caused a significant increase in serum cortisol concentration at 30 min. after the isolation (P < 0.05). The cortisol level then returned to the previous level at 30 min. after the visual isolation was released by removing the plywood fence. 3) At 130 and 160 days of age, however, the visual isolation produced no appreciable change in the serum cortisol concentration of lambs. It is speculated that no response may be caused by the experience at 100 days of age and the sensory input other than the sight. It is not possible, however, to show clear evidence in the present study.

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Three rumen cannulated sheep offered corn silage (CS) and chopped timothy hay (TH) ad lib. were used to examine the effect of an altered rumen fluid outflow rate on microbial nitrogen (MN) yield. Four levels (0, 1, 2 and 3l/d) of artificial saliva was infused into the rumen of sheep offered the two diets. The intraruminal infusion level had little effect on the rate constant of rumen fluid outflow and rumen fluid volume in sheep offered the two diets. The rate constant of rumen fluid outflow tended to be higher in TH group than CS, while rumen fluid volume was higher (P<0.05) in CS than TH group. Rumen fluid outflow (l/d) did not differ (P>0.05) across the treatments. The MN yield was markedly greater (P<0.05) in TH than CS group. The effect of saliva infusion level on MN was not detected. Available energy and N supply were higher for TH compared with CS feeding, this resulted in an increase in MN yield.

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Two trials were conducted to investigate the effects of two different superovulation methods (simple superovulation method using a single injection of porcine follicle-stimulating hormone (pFSH) combined with equine chorionic gonadotropin (eCG) vs. multiple injections of pFSH + eCG) and the breeds of ewes (prolific breed vs. non-prolific breed) on the endocrine profiles of E₂ and LH, the ovarian responses and the embryo qualities during non-breeding season.
The ewes were treated with a vaginal sponge containing synthetic progestogen for 12 days in both trials. Twelve Suffolk ewes were used as a non-prolific breed in Trial 1 (conducted in 1995) and 18 Booroola-Dorset cross breed ewes as a prolific breed in Trial 2 (conducted in 1996). They received a single injection of 20 mg pFSH +500 IU eCG (F1+P) or a multiple injections pFSH + 500 IU eCG (F6 + P). The single injection of pFSH and eCG were conducted on Day-2 (Day 0, was the day of sponge removal). The multiple injections of pFSH were conducted during Day 2 to Day 0 in decreasing doses (5, 5, 4, 4, 3, 3, mg). One hundred micrograms of gonadotropin-releasing hormone analogue (GnRH) was administered on Day 1. All ewes in Trial 1 and 3 ewes in Trial 2 were received twice intrauterine artificial inseminations with frozen-thawed semen using a laparoscope. In Trial 2, 8 ewes were received twice intrauterine-cervical inseminations with fresh-diluted semen, and 5 ewes with fresh semen. Embryos were recovered on Day 7 or Day 8. The blood samples were collected from 4 ewes for each group and E₂ and LH were determined by EIA.
Differences in the endocrine profiles, superovulatory responses and embryo qualities between the breeds and the treatments were observed. All ovulated ewes in prolific breed were superovulated (>3), while 4 out of 8 non-prolific breed ewes were multiply ovulated (≤3). Good fertilization rates were obtained for non-prolific breed (F1 + P 75.0%, F 6+P 100.0%), but the rates of normal embryos was lower in F 6+P (66.7%) and lowest in F 1 +P (20.0%). In prolific breed, the quality of fertilized eggs and the rates of fertilization with fresh semen (87.7%) were good, though the rates of fertilization with frozen-thawed semen and fresh-diluted semen were low (10.5%, 23.2%). The increase of E₂ concentration around estrus for the prolific breed was the same as during the breeding season, while for the non-prolific breed was different with 5 out of 7 ewes showing an early peak of E₂ concentration, and then subsequently decreased.
In conclusion, abnormal E₂ profile around estrus, low ovarian response and quality of embryos were observed in Suffolk ewes treated by the simple superovulation method, while the better results were obtained with the multiple injection method. The more successive stimulation with gonadotropin may yield better result for superovulation of anestrous Suffolk ewes. On the contrary, normal E₂ profiles, good rate of ovulation and quality of fertilized embryos were obtained for anestrous prolific ewes with both simple and multiple superovulation methods. Further investigation is needed to determine an appropriate time for insemination with frozen-thawed semen in anoestrus prolific ewes.

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Carcass characteristics and carcass class were compared in 24 entire male (ram) and 14 female (ewe) Suffolk lambs. Lambs were fed concentrate and hay in confinement, and slaughtered at 18 weeks of age. The means (±s. d.) for body weight at slaughter of ram and ewe were 57.2±3.5 and 48.6±3.1 kg, respectively. Carcass class were assessed by the lamb carcass classification of Japan Sheep Breeders Association.
Although cold-carcass weight of ewe were lower than that of ram (24.2±2.5 v. 27.0±2.1 kg; P<0.01), dressing percentage of ram was lower than that of ewe (52.0±1.7 v. 53.6±2.1%; P<0.05). Kidney fat percentage of ewe was higher than that of ram (2.9±0.8 v. 2.0±0.7%; P<0.01), but no significant difference was seen in back fat depth between sexes. Longissimus dorsi area of ram was higher than that of ewe (17.1±1.7 v. 15.5±1.4 cm²; P<0.01).
In the ewe carcasses, 8 out of 14 (57%) were classified into M2, the most desired class in Japan, ranged in carcass weight from 20 to 25 kg and in backfact depth from 4 to 7 mm. Five out of 14 ewe carcasses (36%) were classified into thicker backfat depth class. In contrast with ewe, 4 out of 24 ram carcasses (17%) were classified into M2. Although 13 out of 24 ram carcasses (54%) were classified into desired backfat depth class, 19 out of 24 (79%) were classified into heavier carcass weight class.

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