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A Luteinizing Hormone-Releasing Hormone-Induced Serum Luteinizing Hormone Surge is not Detectable in the Milk of Cows^1,2,

Washington State University^,4 Pullman 99164-6332

Abstract

Six lactating Holstein cows were used to determine whether a serum luteinizing hormone (LH) surge induced by luteinizing hormone-releasing hormone (LHRH) could be detected in milk. A double antibody radioimmunoassay was evaluated for measuring LH in whole milk. Cows (d 10 of the estrous cycle) were injected with saline (time zero), followed by LHRH 12 h later. Blood samples were collected hourly for 12 h via jugular cannula following each injection; milk removal was accomplished every 2 h by a portable milking machine. On d 10 of the next estrous cycle, treatment order was switched, with the same cows receiving LHRH at time zero and saline 12 h later. Approximately 2 h following LHRH treatment, serum LH levels peaked at 29 ng/ml and remained elevated for 5 h. There was no corresponding change in milk LH detected during the 12-h to 24-h period following the induced serum LH surge. Our conclusion is that the measurement of LH in the milk of cows shows little promise for predicting ovulation time in the cow.

¹ Scientific Paper No. 7698. College of Agric. and Home Econ., Res. Center, Washington State Univ., Pullman 99164. This research was supported by a grant from the Washington Dairy Commission, Project 1037.

² The authors gratefully acknowledge NIAMDD for the reference standard NIH-LH-B7; Dr. L. E. Reichert, Jr., Albany Medical College, Albany, N.Y. for the purified ovine LH for iodination; and Ferris Forar for assistance with the animals.

³ Reprint requests: Dr. J. J. Reeves, Dept. of Anim. Sci., Washington State Univ., Pullman, WA 99164-6332.

⁴ Dept. of Anim. Sci.

⁵ Lutalyse, Upjohn Inc., Kalamazoo, MI.