Yoshihiro Kaneda

Improvement of pregnancy rate in Japanese Black cows by administration of hCG to recipients of transferred frozen-thawed embryos.

Japanese Black primiparous and multiparous beef cows (n = 120) were selected as recipients and randomly divided into three groups (A, B, and C) of 40 recipients each. Group A received an intramuscular (i.m.) treatment of 1500 IU human chorionic gonadotropin (hCG) on day 1 (day 0 = onset of estrus), while Group B received an i.m. treatment of hCG on day 6. Group C received an i.m. treatment of 5 ml saline on day 6 as a control. On day 7, frozen-thawed embryo transfer was conducted in all groups, and pregnancy was diagnosed by palpated per rectum 40-50 days after the transfer. Twelve recipients were randomly selected from each group. Plasma progesterone (P) and estradiol-17beta (E2) concentrations were determined in these recipients on days 6, 7 and 14, and at the time of pregnancy diagnosis, and their ovaries were examined for a corpus luteum and follicles by palpated per rectum. The pregnancy rate in Group B was higher (67.5%. P < 0.05) than the rate in Group C (45.0%) and in Group A (42.5%). The plasma P concentration on day 14 tended to be higher although not significantly in Group B than in Groups C and A. At the time of pregnancy diagnosis, the blood P concentration of pregnant recipients in Group B was higher (P < 0.05) than that of those in Groups C and A. The plasma E2 concentrations on days 7 and 14 were lower (P < 0.05) in Group B than in Groups C and A. These results showed that administration of hCG 6 days after estrus improved the pregnancy rate for non-surgical frozen embryo transfer 7 days after estrus by enhancing luteal function and depressing E2 secretion.

Fasting-induced suppression of pulsatile luteinizing hormone secretion is related to body energy status in ovariectomized goats

The effect of energy status on the response of luteinizing hormone (LH) pulse frequency to acute short-term energy deficiency created by fasting in estradiol-treated ovariectomized Shiba goats was studied in two experiments. In experiment 1, eight goats whose mean body weight (BW) was 25.6 +/- 5.8 (mean +/- S.D.)kg were fed 500 g hay cubes daily for 1 week. Then they were fasted for 3 days. Blood samples were collected for 4 h at 6 min intervals on the last day of feeding, first, second and third day of fasting for LH analysis. The goats were divided into light (<24 kg, n = 4) and heavy (> or =24 kg, n = 4) groups for data analysis. There was no difference in LH pulse frequency between the last day of feeding and each day of fasting in the heavy group. LH pulse frequency was significantly (P < 0.05) suppressed on the second day (3.3 +/- 1.3 pulses/4 h) and on the third day (2.3 +/- 1.9 pulses/4 h) relative to the day prior to fasting (4.8 +/- 1.5 pulses/4 h) in the light group. In experiment 2, BW plus a body mass index (BMI (body weight (kg)/withers height (m)/body length (m))/10 [corrected]) were measured to define energy status. Nine goats (BW, 25.6 +/- 5.8 kg) were fed 500 g hay cubes daily for a week and then fasted for 3 days. Then they were divided into two groups offered either a maintenance (n = 4) or a restricted (n = 5) level of feeding for 4 weeks. The restricted level of feeding was 30% of maintenance requirement based on the BW recorded weekly. The feeding level was then adjusted to maintain BW for a further week followed by 3 day fasting for restricted animals. Blood samples were collected for 6 h at 10 min intervals on the day prior to fasting and on third day of fasting before and after the dietary manipulation. BW (26.6 +/- 2.2 to 26.8 +/- 3.8 kg) and gBMI (8.4 +/- 0.4 to 7.8 +/- 0.3) remained constant over the period prior to fasting for the maintenance animals but were significantly lower (P < 0.05) after 4 weeks for the restricted goats (BW, 26.3 +/- 2.1 to 21.5 +/- 2.4 kg; gBMI, 8.4 +/- 0.9 to 6.9 +/- 0.7). There was no significant difference in the LH pulse frequency between feeding and fasting day in both sampling periods in the maintenance group. In the restricted group, LH pulse frequency was not suppressed by fasting in the first sampling period (6.8 +/- 2.9 to 5.2 +/- 2.5 pulses/6 h), whereas it tended to be suppressed (4.8 +/- 3.1 to 1.6 +/- 2.3 pulses/6 h; P < 0.06) and was significantly (P < 0.05) correlated to body weight (r = 0.70) and gBMI (r = 0.81) after the dietary manipulation. These results suggest that the suppressive effect of short-term energy restriction (fasting) on pulsatile LH secretion is related to body energy status.

Synchronization of estrus and ovulation in graz-ing cows with intramuscular injection of prosta-glandin F2α; in the case of administration of synthetic LH-releasing hormone, or human chori-onic gonadotropin followed

黄体期の牛86頭に対してPGF2α10 mgを筋肉内注射し,黄体退行の認められた65頭のうち51頭に合成LH-RH-1200μg(A群)またはHCG 1,000~2,000 i.u.(B群)をPGF2α投与後42~47時間(A-I群8頭,B-I群11頭),57~60時間(A-II群8頭,B-II群7頭),72~74時間(A-II群9頭,B-III群8頭)に筋肉内注射して,これらの発情発現と排卵状況及び受胎性をPGF2α単一処置(C群14頭)のそれと比較検討して,つぎの成績を得た。1. PGF2α投与後37~84時間における発情発現率は,A, B両群のI群ではそれぞれ25.0%,27.3%,II群では37.5%,42.8%であり,C群の71.5%と比べて低かったが,III群では66.7%,62.5%で大差なかった。2. PGF2α投与後84時間以内に発情発現がみられなかった牛は,すべて120時間以内に無発情排卵した。3. PGF2α投与後排卵までの平均(±S.D.)時間は,A,B両群のI群ではそれぞれ74.5(±6.7),79.5(±6.9)時間,II群ではそれぞれ88.0(±3.7),87.0(±4.6)時間,III群ではそれぞれ98.7(±8.2),94.0(±9.8)時間であり,排卵誘起剤の投与時期が早いほど短かった。なお,C群のそれは89.9(±13.3時間)であった。4. PGF2α投与後3~5日の間の授精による受胎率は,A, B両群のI群ではそれぞれ37.5%(3/8頭),12.5%(1/8頭),II群では37.5%(3/8頭),42.9%(3/7頭)でC群の50.0%(7/14頭)に比べて低かったが,III群では55.6%(5/9頭),50.0%(4/8頭)でC群のそれとほぼ同率であった。5. 以上の成績から,PGF2αと合成LH-RHまたはHCGの併用により排卵を効果的に同期化することが可能であり,PGF2α投与後これら薬剤を投与するまでの時間間隔が長いほど処置後の発情発現率は高く,同期化した発情時の受胎成績が良い傾向が認められた。

Effects of intrauterine injection of PGF2α on progesterone levels in peripheral blood plasma of the cow

牛において,排卵後2日ないし15日の黄体期にPGF2αを連日2回(1回用量0.5~1.0 mg)あるいは1回(用量3~6mg),黄体の存在する卵巣と同側の子宮角に注入して,処置後の黄体の変化にともなう末梢血中progesteroneの消長を追求して,次の成績を得た。1) 排卵後2~4日の黄体初期の早い時期に処置した8頭中4頭は処置後8~14日目に排卵した。処置後の血中progesterone値は,A)正常性周期におけるそれとほぼ同様のもの,B)処置後一時減少するが,ふたたび増加して以後A)と同様に維持されるもの,C)処置後暫時増加の傾向を示すが,結局早期に低下するもの,D)処置後いったん低下したのちふたたび増加するが結局早期に低下するもの,などの消長型を示した。2)排卵後4日および5日の黄体初期に連日処置した2頭の牛は,処置後4日目に排卵した。血中pro-gesteroneは処置後急激に減少して,2回目の処置後24時間には処置前の1/3の値を示した。3)排卵後9~11日の黄体開花期に処置した3頭の牛は,いずれも処置後4日目に排卵した。血中pro-gesteroneは処置後3時間にすでに減少の傾向を示し,24時間後には処置前の値の1/2~1/6に減少した。4) 排卵後15日目の黄体後期に処置した2頭の牛は,処置後4日および6日目に排卵した。処置後24時間の血中progesteroneは処置前の値のそれぞれ1/2および1/8以下に減少した。5)血中progesteroneの消長は触診による黄体の形状変化とほぼ一致した。6)以上の成績から,PGF2αの黄体退行作用は排卵後5日以降の黄体期の牛ではきわめて顕著であるが,排卵後4日までの間の牛では弱いことが明らかにされた。