Ovarian changes in dairy cows intramuscularly injected with LH-RH analogue in the postpartum inactive period of the ovary.
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概要
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Seventeen dairy Holstein cows diagnosed as bearing postpartum inactive ovaries by repeated rectal palpations were divided into 4 groups. Three cows each of Groups I and II and 5 cows of Group III were treated by a single intramuscular injection with 200μg of LH-RH analogue ([Des-Gly-NH<SUB>2</SUB><SUP>10</SUP>, Pro-ethylamide<SUP>9</SUP>]-LH-RH; LH-RH-A) on Day 7, on Day 13-14 and on Day 21-22 (Day 0 being the day of parturition), respectively. Six cows of Group IV were served as untreated controls. Changes in the ovary after treatment were examined by rectal palpation at intervals of one or two days. Plasma progesterone concentrations were determined by radioimmunoassay in blood samples collected by jugular vein puncture every two days.<BR>Following results were obtained. <BR>1. Ovulation was induced over a period from 24 to 48h after LH-RH-A treatment in 2 cows each of Groups I and II and 4 cows of Group III; i.e. eight (72.7%) of the 11 cows in total. Ovarian func-tion became active in these 8 cows after induced ovulation. <BR>2. The responsiveness of the ovary to LH-RH-A treatment was better on Day 21 than on Day 14 or 7, judging from the results of induced ovulation that was followed by ovarian activation. <BR>3. A normal ovarian cycle recurred by at least two processes after induced ovulation. 1); The corpus luteum (CL), formed after induced ovulation, was subnormal in size and began to degenerate as early as 7 days after ovulation. A follicle became palpable about 2 days after ovulation grew up and ovulated about 10 days after induced ovulation. During this time span, progesterone increased slight by 2ng/m<I>l</I> even at the peak. 2); The CL was normal in general and began to degenerate about 15 days after induced ovulation. So, a follicle became palpable about 11 days after ovulation ovulated about 20 days after induced ovulation. Progesterone increased after induced ovulation and remained at a high level for about 15 days. The same two processes were also recognized after 1st ovulation in the 6 untreated controls. <BR>4. Estrous signs were generally obscure at the time of the 1st ovulation induced by LH-RH-A or occurred spontaneously, but they became obvious in most cases at the 2nd and 3rd ovulation after parturition. <BR>These results indicated that a single intramuscular injection with 200μg of LH-RH-A was effec-tive enough to induce an ovarian cyclic activity in postpartum dairy cows in which the ovaries were still inactive on Day 21 after parturition.
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