USE OF MILK PROGESTERONE PROFILES FOR THE STUDY OF FERTILITY IN THE POSTPARTUM PERIOD OF DAIRY COWS

บทคัดย่อ

The present study focused on the onset of ovarian function and occurence of oestrus of 83 cross bred cows (Native x Holstein-Friesian) from village farms, in Chiang Mai Province. Milk samples were collected every three or four days beginning from day 14 postpartum to anylyze for progesterone content by Radioimmunoassay technique. By using progesterone profiles, cows were classified in four groups: cows with normal oestrous cycles (42.2%), short oestrous cycles followed by normal cycles (33.7%), anoestrus (20.5%) and abnormal oestrous cycles (3.6%). The period from parturition to first and second oestrus were 29.5 + 12.79 and 50 + 12.47 days, respectively. Nineteen, 39.7, 15.9, 127, 11.1 and 1.6 percent of cows exhibited first oestrus at under 20, 21-30, 31-40, 41-50, 51-60 and 61-70 days after parturition. These results suggest several area for future investigation, including reduction numbers of short oestrous cycle, anoestrus and prolongation of oestrus exhibition to improve reproductive efficiency of the animals.