Fish meal supplementation alters uterine prostaglandin F^sub 2[alpha]^ synthesis in beef heifers with low luteal-phase progesterone1,2

• Published in: Journal of animal science 2005-08, Vol.83 (8), p.1832
• Main Authors: Wamsley, N E, Burns, P D, Engle, T E, Enns, R M
• Format: Article
• Language: English
• Subjects: Cattle; Dietary supplements; Fatty acids; Fish; Meals
• ISSN: 0021-8812; 1525-3163

The objective of the current study was to evaluate the effect of ω-3 fatty acids in fish meal on mitigating uterine PGF^sub 2α^ synthesis in heifers with low luteal-phase concentrations of progesterone. Animals were individually fed a corn silage-based diet supplemented with fish meal (5% of DMI; n = 12) or corn gluten meal (6% of DMI; n = 13). Estrous cycles were synchronized using PGF^sub 2α^ beginning on d 25 of supplementation. Random heifers from each supplement group (n = 6 fish meal, and n = 7 corn gluten meal) were given three additional i.m. injections of PGF^sub 2α^ (25 mg) at 12-h intervals beginning at 0600 on d 3 after estrus to induce formation of corpora lutea that secrete lower concentrations of progesterone. Jugular blood samples were collected daily commencing on d 1 and continuing through d 16 of the estrous cycle to determine serum progesterone concentrations. Oxytocin was administered i.v. (100 IU) to heifers on d 16 after estrus to stimulate uterine PGF^sub 2α^ synthesis. Before statistical analyses, heifers were sorted to either normal or low luteal-phase progesterone as determined from serum progesterone on d 9 of the estrous cycle. After sorting, treatment groups consisted of 1) normal luteal progesterone + fish meal (n = 6); 2) low luteal progesterone + fish meal (n = 6); 3) normal luteal progesterone + corn gluten meal (n = 6); and 4) low luteal progesterone + corn gluten meal (n = 7). Serum concentrations of the PGF^sub 2α^ metabolite following oxytocin stimulation tended (P = 0.09) to be greater in heifers with low luteal-phase progesterone compared with heifers with normal luteal-phase progesterone. Fish meal supplementation mitigated this response in heifers with low luteal-phase progesterone (P < 0.05), but had no effect on heifers with normal luteal-phase progesterone. In conclusion, the ω-3 fatty acids in fish meal seem to decrease uterine PGF^sub 2α^ synthesis in heifers with low luteal-phase serum concentrations of progesterone. [PUBLICATION ABSTRACT]