Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2008
Publication Date: 8/8/2008
Citation: Galbreath, C.W., Scholljegerdes, E.J., Lardy, G.P., Olde, K.G., Wilson, M.E., Schroeder, J.W., Vonnahme, K.A. 2008. Effect of feeding flax or linseed meal on progesterone clearance rate in ovariectomized ewes. Domestic Animal Endocrinology. Interpretive Summary: Early embryonic loss accounts for the majority of pregnancy losses that occur and has been attributed to low levels of circulating progesterone (P4) in the dairy cow. The phytoestrogen, secoisolariciresinol diglycoside (SDG), is found within the flax hull and its solvent extraction by-product linseed meal (LSM). Flax also contains high levels of omega-3 fatty acids which can serve as precursors to series-3 prostaglandins. In addition, high fat diets have been shown to increase circulating levels of P4. The objective was to determine the effect of feeding flax, which contains SDG and omega-3 fatty acids, or LSM containing only SDG, on P4 clearance rate in ovariectomized ewes. Ovariectomized ewes were individually fed one of three diets: 1) Control (phytoestrogen-free), 2) Flax containing diet, or 3) linseed meal (LSM) containing diet to investigate the rate of progesterone (P4) clearance. On day 20 of feeding (day 0 = initiation of treatment), a P4 releasing device (CIDR) was placed in the vagina and jugular blood samples were obtained prior to CIDR insertion and 15, 30, 60, and 120 min following CIDR insertion. From this experiment we found that feeding flax and/or LSM to livestock could be potentially beneficial for improved fertility. Specifically, ewes fed LSM had greater absorption of P4 into the circulation from the CIDR. In addition, ewes fed flax tended to have lower clearance rates of P4 compared to LSM fed ewes, which could help decrease early pregnancy losses, particularly in dairy cattle, and thus reduce the costs associated with lost pregnancies.
Technical Abstract: Ovariectomized ewes (n = 22; 68.76 ± 2.34 kg initial body weight; 2.9 ± 0.1 initial body condition score) were individually fed one of three diets: 1) Control (phytoestrogen-free; n = 7), 2) Flax containing diet (n = 8), or 3) linseed meal (LSM) containing diet (n =7) to investigate the rate of progesterone (P4) clearance. On day 20 of feeding (day 0 = initiation of treatment), a P4 releasing device (CIDR) was placed in the vagina and jugular blood samples were obtained prior to CIDR insertion and 15, 30, 60, and 120 min following CIDR insertion. Further, blood samples were obtained daily between days 21 to 24. On day 25, blood samples were retrieved prior to CIDR removal and 2, 5, 10, 15, 30, 60, 120, and 360 min following CIDR removal. There was no difference in initial or final body weight or body condition score and there were no time by diet interactions on P4 clearance. The fractional rate of P4 uptake measured prior to CIDR insertion through day 4 following insertion tended to be greater (P = 0.07) in LSM fed ewes (508.75 ± 71.37 %/min) compared to Flax (295.39 ± 66.76 %/min) and Control fed (287.54 ± 71.37 %/min) ewes. Diet tended (P = 0.10) to influence P4 clearance rate when measured from prior to CIDR removal through 120 min following CIDR removal with LSM fed ewes having a greater (1.26 ± 0.2) fractional rate constant than Flax (0.929 ± 0.09) and Control fed (0.922 ± 0.09) ewes. Flax fed ewes also had more (P < 0.01) omega-3 fatty acids and total fatty acids in plasma. Reports of increased pregnancy rates in dairy cows fed flax may relate to P4 metabolism.