ENDOCRINE RESPONSES IN COWS FED PONDEROSA PINE NEEDLES AND THE EFFECTS OF STRESS, CORPUS-LUTEUM REGRESSION, PROGESTIN, AND KETOPROFEN

Pregnant cows were fed pine needles (PN, 2 kg.cow(-1).d(-1)) mixed wit h the diet to determine factors that affect abortion response. In Exp. I, treatments were used to determine the effects of experimental stre ss and pelleting of pine needles. Pelleting needles and experimental s tress delayed abortion response (P < .01). Stress-induced delay was as sociated with abnormal patterns of progesterone and cortisol (P < .01) . In Exp. 2A and 2B, the role of the corpus luteum (CL) in abortion re sponse to PN consumption was investigated by regressing the CL with pr ostaglandin F-2 alpha. Regression of the CL and PN feeding reduced int erval to parturition, but the effect of PN feeding was less when the C L was regressed (PN x CL, P < .01). The progesterone increase in respo nse to experimental stress was decreased by CL regression (P < .01). I n Exp. 3, melengestrol acetate (MGA) was fed (0, 2, or 4 mg.cow(-1).d( -1)) in addition to PN. Parturition was blocked more effectively as do se of MGA increased (P = .075), but only parturition was blocked rathe r than the effects of PN. In Exp. 4, CL regression was blocked by feed ing ketoprofen. Ketoprofen delayed response to PN, but the effect was only temporary (P < .01). Our conclusions are that 1) experimental str ess delays abortion response to PN by increased concentrations of prog esterone, 2) pelleting PN decreases their abortifacient activity, and 3) abortions caused by PN can be blocked by feeding a progestin or a p rostaglandin inhibitor, but these compounds do not block the primary a bortifacient effects of PN.