The concentration of oestradiol-17beta was measured by radioimmunoassay in the milk and blood of lactating buffaloes after insemination. The concentration of oestradiol-17beta in milk was observed to be two to three times higher when compared with that in plasma samples. Major peaks of oestradiol-17beta in milk coincided with similar but smaller peaks occurring in plasma samples. In animals which were not pregnant, the major peak of oestradiol-17beta was recorded on the day of oestrus.

Changes in progesterone concentration of blood and milk were measured by radioimmunoassay in 10 Murrah buffalo up to 40 days after insemination. Progesterone concentration in blood plasma at estrus was .1 ng/ml which rose to a peak of 3.6 ng/ml on day 13. It continued to increase in animals that conceived but dropped to .6 ng/ml on 3 days before next estrus in those that failed to conceive. The average concentration of progesterone in milk was .5 ng/ml at estrus; it increased to 18 ng/ml on day 15, and thereafter it declined to 4.4 ng/ml 3 days preceding next estrus in nonpregnant animals. In pregnant animals, it was maintained and elevated further to 24.8 ng/ml on day 37. Progesterone in milk was four to five times higher than in blood plasma.

No abstract

IntroductionThe occurrence of symptoms of oestrus during gestation is common in cattle and buffaloes. Its incidence has been reported to be 14.4 and 20.3 O / o in buffaloes and cows, respectively and it can occur at any stage of gestation, ranging from 22 to 308 days in buffaloes, but with the highest probability between 181 and 210 days (CHAUHAN et al., 1976). Hormonal factors seem to be responsible for manifestation of oestrus behaviour during gestation. A number of authors (CHOUDHARY et al., 1964;LUKTUKE et al., 1968;DONOHO and RICHARD, 1955;PAHLMANN and MEAD, 1958) have studied the incidence of this phenomenon in cattle and buffaloes. No information appears to be available on the hormonal interplay accompanying gestational oestrus. It seemed pertinent, therefore, to determine the levels of progesterone and oestradiol in the blood plasma of animals showing gestational heat. Material and MethodsBlood samples (20ml. heparinized) were taken from the jugular vein of two pregnant buffaloes showing oestrus at days 112 and 130 of pregnancy. Oestrus was detected by the parading of a teaser bull in the herd of pregnant buffaloes. The animals were followed for blood collection up to day 40 from the onset of "pseudooestrus". One normal cycling buffalo was also followed as a control up to day 40 after its insemination. The blood was cooled rapidly in ice and centrifuged within an hour after collection. Thc plasma was stored at -20 O C pending hormonal analysis.The concentrations of progesterone and oestradiol-17 , 4 were determined by the modification of the radioimmunoassay technique described by Aso et al., 1975. Duplicate plasma samples (0.2 ml. and 5 ml.) were extracted with 2 ml. and 15 ml. of redistilled diethyl ether for progesterone and oestradiol-17 b, respectively. The ether was dried under a current of nitrogen at 40 O C and the residue was subjected to radioimmunoassay using antisera against N. D. R. I. Publication No. 78-160. U. S. Copyright Clearance Center Code Statement: 0300-871 1/79/2606-0502$02.50/0 Proesterone and oestradiol-17 j3 in buffaloes showing gestational oestrus 503 progesterone and oestradiol-17 8. The sensitivity of progesterone and oestradiol-17 j3 assay was 5 and 3.8 pg, respectively. The coefficients of inter and intra-assay variation were 14.6 and 15.1 o/o for progesterone and 17.7 and 19.0 o/o for oestradiol-17 8, respectively. The specificity of antisera has been reported earlier for progesterone (ARORA et al., 1979) and oestradiol-17 / 3 (BACHLAUS et al., 1979) from this laboratory. Results and DiscussionThe concentration of oestradiol-17 , B in the serum of buffaloes showing gestational oestrus (No. 105 and 967) was hi hest on the day of "pseudowhich was maintained during the rest of the period under study. The progesterone concentration was high on the day of "pseudooestrus" and comparable to that of pregnant buffaloes (unpublished data from this laboratory), whereas in the control animal the progesterone concentration was lowest on the day of oestrus. However, the oestradiol-17 p c...

Sci., 38, 347-353. 13. MCCRACKEN, J. A., M. F. GLEW, and R. J. SCARAMUZZI, 1970: Corpus luteum regression induced by prostaglandin F-2 a.