Plasma oestradiol and progesterone during early pregnancy in the cow and the effects of treatment with buserelin |
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| Institution: | 1. Division of Animal Sciences, University of Missouri, Columbia, MO, 65211, USA;2. College of Veterinary Medicine, University of Missouri, Columbia, MO, 65211, USA;3. Division of Plant Sciences, University of Missouri, Columbia, MO, 65211, USA;1. University of Mohaghegh Ardabili, Faculty of Agriculture and Natural Resources, Department of Animal Sciences, Ardabil, Iran;2. Agricultural Research Education and Extension Organization (AREEO), Animal Science Department, Kermanshah Agricultural and Natural Resources Research and Education Center, Kermanshah, Iran;3. Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma del Estado de México, Mexico;1. Biology Department, University of Nebraska at Kearney, Kearney, NE 68849 USA;2. School of Biological Sciences, University of Nebraska at Lincoln, Lincoln, NE 68588 USA;2. Department of Dairy Science, University of Wisconsin-Madison, Madison 53706;3. MofA Global, International Center for Biotechnology, Mt. Horeb, WI 53572;4. Department of Animal Sciences, University of Sao Paulo-VRA, 05508 São Paulo, SP Brazil;2. Department of Animal Science, University of Connecticut, Storrs 06269 |
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| Abstract: | We have monitored plasma concentrations of oestradiol and progesterone after insemination in dairy cows, and investigated the effects of injection with 10 μg of the gonadotrophin-releasing hormone (GnRH) analogue buserelin, a treatment known to result in an improvement in conception rate. Animals were injected intramuscularly on Day 12 after insemination with 2.5 ml of either control saline (n = 29) or buserelin (n = 26). Blood samples were collected from Day 8 to Day 17 and milk samples from the day of insemination until Day 30. On the basis of milk progesterone profiles, in the control group 15 cows remained pregnant (control pregnant) and 11 underwent luteolysis (control not pregnant), whereas in the treated group 13 cows remained pregnant (treated pregnant) and 13 underwent luteolysis (treated not pregnant). Three cows were excluded from the control group owing to high progesterone at insemination or failed ovulation. In both the control and treated groups mean plasma progesterone concentration was significantly (P < 0.05) lower in non-pregnant cows than in pregnant ones from Day 12 post-insemination. However, no significant effect of buserelin treatment on plasma progesterone concentration was detected. In the control group the plasma oestradiol concentration was similar in the pregnant and non-pregnant cows. In the treated group, plasma oestradiol concentration in the non-pregnant cows was similar to that in the control group, whereas in the treated pregnant cows the plasma oestradiol concentration showed a significant (P < 0.05) decline after treatment. As oestradiol is known to stimulate the development of the luteolytic mechanism at this time, we suggest that buserelin is acting to reduce the strength of the luteolytic drive in some cows, thus improving the chance of the embryo being able to prevent luteolysis. |
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