43 (2) : 178 183 1997 A cta Zoologica S inica 3 ( 730070) 17 2 1 5 (216 112) ; 6 17 2 2 015 115 (019 013) ; 17 2 ; 12 15 22 34 36 48 17 2 ( Bos grunniens) 1 400 85 % 2 500 5 000m 1985 17 2 ( Yu et al. 1992b 1993a 1993b 1993c) 17 2 1 111 5 10 2 500 3 500m ; 42 13 1996202212 1997201230 3 (No. 39100096)
2 : 179 : (7 ) (6 ) (8 : 00) (20 : 00) 10 15ml 1 % 0115ml 1 % 0115ml ( - 25 ) 112 : (1992a) L H/ hcg 125 I - hcg hcg 0120 ng/ 8121 % ( n = 10) 15165 % ( n = 5) 96158 % : ( Yu et al. 1993b) 4102 pg/ 102183 % 7165 % ( n = 10) 10123 % ( n = 2) 17 2 : ( Yu et al. 1993b) 5101 pg/ 100105 % 4189 % ( n = 10) 10102 % ( n = 2) 113 ( x) ( SD) Student s t 2 211 21111 : 42 35 1 5 (216 112) ; 7 3 15 512 416 17 2 8 6 2 ( ) : ; 42 33 : 10 (2414 %) 015 17 (4115 %) 1 6 (1416 %) 115 019 013 ; 9 : 6 215 3 3 17 2 ; ; : / 1 3 (115 017) ;
180 43 17 2 21112 7 3 4 0 ( ) 015cm 1 017cm 2 3 ( ) 019 110cm ; 60 72 6 1 2 0 015cm 1 ( ) 019 1cm ; 36 48 212 17 2 6 0122 0109 ng/ ml ; 5 ( - 5) - 2 (1123 0111 ng/ ml) ; - 1 (0 ) 0119 0108 ng/ ml 17 2 12133 4163 pg/ ml ; 8 6 ( - 8-6) ( - 6 27176 9131 pg/ ml P > 0105) - 2 (10141 6153 pg/ ml) ; - 1 (0 ) (24157 11135 pg/ ml) 6197 5176 pg/ ml ( 1) 1 2 17 2 Fig. 2 Changes of plasma luteinizing hormone Fig. 1 Changes of plasma progesterone and concentrations during oestrus in yak 17 2oestradio1 concentrations around oestrus in yak 213 6 2 4141 0128 ng/ ml (0 ) (5149 1117 ng/ ml) ( P > 0105) ; 10 (7189 0187 ng/ ml P < 0101) 11 (4103 1160 ng/ ml)
2 : 181 ( P > 0105) 12 15 ( 14 14130 1142 ng/ ml) ; 17 (5103 1159 ng/ ml P > 0105) 1 (015 1 ) ( Y 46 ) ( 3) 3 3 Y 46 Fig. 3 Changes of plasma luteinizing hormone concentrations during oestrus of yak No. 46 015 3 ( 1981) 2 3 7 8 ( 1980) 019 013 (015 115) ; 215 3 1 5 3 17 2 ( Yu et al1 1993b) (7 10 ) 17 2 17 2 17 2 ( 3 ) Hunter (1986) Webb (1980) (Berardinelli et al. 1980 ; Gonzalez2Padilla et al. 1975) Dodson (1988) 17 2
182 43 ; ( Yu et al. 1993a 1993b) 17 2 14 17 2 ( Walters and Schallenberger 1984) ( Carr 1972) 6 36 48 14 22 34 1980. 2 : 13 15. 1992a. 2 : 99 105. 1981. 4 : 53 55. Berardinelli J. G. R. A. Dailey R. L. Butcher and E. K. Inskeep 1980 Source of circulating progesterone in prepubertal ewes. Bio. Reprod. 22 : 233 236. Carr W. R. 1972 Radioimmunoassay of luteinizing hormone in the blood of zebu cattle. J. Reprod. Fert. 29 : 11 18. Dodson S. E. B. J. Mcleod W. Haresign A. R. Peters and G. E. Lamming 1988 Endocrine changes from birth to puberty in the heifer. J. Reprod. Fert. 82 : 527 538. Gonzalez2Padilla E. J. N. Wiltbank and G. D. Niswender 1975 Puberty in beef heifers. J. A ni m. Sci. 40 : 1 091 1 104. Hunter M. G. J. A. Southee B. J. Mcleod and W. Haresign 1986 Progesterone pretreatment has a direct effect on GnRH2induced preovulatory follicles to determine their ability to develop into normal corpora lutea in anoestrous ewes. J. Reprod. Fert. 76 : 349 363. Walters D. V. and E. Schallenberger 1984 Pulsatile secretion of gonadotrophins ovarian steriod and ovarian oxytocin during the periovulatory phase of the oestrous cycle in cow. J. Reprod. Fert. 71 : 503 512. Webb R. G. E. Lamming and N. B. Haynes 1980 Plasma progesterone and gonadotrophin concentrations and ovari2 an activity in postpartum dairy cows. J. Reprod. Fert. 59 : 133 143. Yu S. J. Y. M. Huang and B. X. Chen 1992b Postpartum ovarian function in yak cows as revealed by concentra2 tions of progesterone in defatted milk. Recent A dvances in A ni mal Production proceeding of the Sixth A ni mal Science Congress of A A A P. 3 : 93. Yu S. J. Y. M. Huang and B. X. Chen 1993a Reproductive patterns of the yak. I. Reproductive phenomena of the female yak. B r. Vet. J. 149 : 579 583. Yu S. J. Y. M. Huang and B. X. Chen 1993b Reproductive patterns of the yak. II. Progesterone and oestra2 dio1217 1evels in plasma and milk just before the breeding season ; also during normal and short oestrous cycles. B r. Vet. J. 149 : 585 593. Yu S. J. Y. M. Huang and B. X. Chen 1993c Reproductive patterns of the yak. oestradio1217 during pregnancy and the periparturient period. B r. Vet. J. 149 : 595 602. III. Levels of progesterone and
2 : 183 ( Abstract) CHARACTERISTICS OF REPROD UCTION AND RELATED HORMONE CHANGES AROUND OESTRUS IN YAK YU Si2Jiu CHEN Bei2Heng ( Depart ment of Veterinary Medicine Gansu A gricult ural U niversity L anzhou 730070 China) The reproductive characteristics of 42 multiparous yaks around oest rus were examined by clinical observation and rectal palpation. Concent rations of plasma progesterone and oestradiol217 in 6 subjects during this period were measured by radioimmunoassay ( RlA) and luteinizing hormone was analyzed by radioreceptor assay ( RRA). At t he beginning of the breeding season all examined animals showed oestrus2like pro2oestrus signs for 1 5 (216 112) days before they were in heat. The length of oestrus was 015 115 (019 013) days in the animals mated at the beginning of oestrus or in early oestrus (78 %) ; it lasted 215 3 days in those animals which were mated in late oestrus (12 %). Ovulation oc2 curred 36 48 hours from the onset of oestrus. The baseline level of oestradiol217 before the first oestrus was 12133 4103 pg/ ml ; a peak of 26176 8131 pg/ ml occurred 8 6 days before oestrus which was similar to that on the day of oestrus ( 24157 11135 pg/ ml P > 0105) ; it declined to the baseline level at the end of oestrus. The baseline level of pro2 gesterone before the first oestrus was 0122 0109 ng/ ml ; a small peak of 1123 0111 ng/ ml appeared 2 days before oestrus ; it then decreased and maintained at a low level until the end of oestrus. The reason of the temporal increase in oestradio1217 and progesterone before the first oestrus might be a transition to the normal cyclic activity at the beginning of the breeding season. The baseline level of luteinizing hormone plateau appeared 12 15 hours after the onset of oestrus with a maximum of 14134 1142 ng/ ml occurred at 14th hour ; it declined to the baseline level at the 17th hour. Key words Yak Reproductive characteristic Progesterone Oestradiol217 Luteinizing hormone Around oest rus