Studies on levels of luteinuzing hormone and prolactin In serum of cycling and anoestrous cows

Abstract

Vlakke van luteiniserings hormoon (LH) in serum gedurende die estrus-siklus en die post partum periode is deur middel van radio immunologiese bepaling in 14 Brangus en 5 Fries koeie bepaal. Met die uitsondering van die periodes tydens die pre-ovulasie golf, het die basale vlakke van LH tussen 0,2 en 5,0 ng LH/ml serum gevarieer. Hierdie basale vlakke van LH, het net soveel tussen diere as binne diere of tussen die rasse gevarieer. Gedurende die pre-ovulasie golf het die LH vlakke verhoog tot tussen 8,0 en 60,0 ng LH/ml serum. In 16 van die 21 gevalle waar ovulasie gepaardgegaan het met estrus, het die verhoging in LH serum met die dag van estrus saamgeval. In 4 gevalle het die toe-name in LH 1,2 of 3 dae na estrus plaasgevind en in een geval 2 dae voor estrus. n Hoe voorkoms van ovulasie sonder estrus is gevind. Geen standhoudende veranderings in die prolaktien vlakke van die serum is in twee van die koeie gedurende die estrus siklus waargeneem nie.

SUMMARY

Blood levels of luteinizing hormone (LH) were measured, using a radioimmunossay, during the post-partum period in 14 Brangus and 5 Friesland cows. Except during pre-ovulatory surges, basal blood levels of LH ranged between 0,2 and 5,0 ng LH/ml serum. These basal levels of LH varied more between animale than either within animals or between breeds. During the pre-ovulatory surge. LH levels increased to between 8,0 and 60,0 ng LH/ml serum. In 16 of the 21 cases when ovulation was associated with oestrus, the LH surge was detected on the days of oestrus. In 4 instances, the LH surge was detected 1,2 or 3 days after oestrus and in one instance, 2 days before oestrus. A high incidence of ovulation without oestrus was noted. No consistent changes were detected in levels of prolactin in the serum of two of these cows during the oestrous cycle.