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This Article Full Text Full Text (PDF) All Versions of this Article: jas.2008-1424v1 87/9/2985    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Scholljegerdes, E. J. Articles by Moss, G. E. PubMed PubMed Citation Articles by Scholljegerdes, E. J. Articles by Moss, G. E.

Effects of feeding high-linoleate safflower seeds on postpartum reproduction in beef cows^1,2

Department of Animal Science, University of Wyoming, Laramie 82071

⁴ Corresponding author: gm{at}uwyo.edu

Two experiments were conducted to evaluate reproductive responses to supplemental high-linoleate safflower seeds in postpartum beef cows. In Exp. 1, 18 primiparous, crossbred beef cows (411 ± 24.3 kg of BW) were fed Foxtail millet hay starting 1 d postpartum at 1.68% of BW (DM basis) and a low-fat control (control: 63.7% cracked corn, 33.4% safflower seed meal, and 2.9% liquid molasses; DM basis) at 0.35% of BW (n = 9) or a supplement (linoleate) containing 95.3% cracked high-linoleate (79% 18:2n-6) safflower seeds and 4.7% liquid molasses (DM basis) at 0.23% of BW (n = 9). Beginning 1 d postpartum, blood was collected every 3 d for sera. Cows were slaughtered at 37 ± 3 d postpartum for collection of hypothalami, anterior pituitary glands, liver, ovarian follicles, and uterine tissue. By 37 ± 3 d postpartum, dietary treatment did not influence ovarian follicular development (P 0.17), hypophyseal concentrations of LH (P = 0.14), or concentrations of IGF-I in liver (P = 0.15). In contrast, anterior pituitary glands from linoleate cows contained more FSH (P = 0.02) than control cows and linoleate cows had less IGF-I in the medial basal hypothalamus (P = 0.05), preoptic area (P = 0.06), and in follicular fluid (P 0.03) from follicles less than 15 mm in diameter. In Exp. 2, twenty-four 3-yr-old multiparous beef cows (initial BW 473.9 ± 9.2 kg) were fed chopped bromegrass hay at 2.1% of initial BW starting 1 d postpartum and a low-fat supplement (control) fed at 0.6% of initial BW or a high-linoleate supplement (linoleate) fed at 0.4% of initial BW until 80 d postpartum. Cows were observed for estrus twice daily from d 30 to 80 postpartum and treated with GnRH between 40 and 45 d postpartum. Seven days after GnRH administration cows were given PGF₂ and were checked for estrus and artificially inseminated until 80 d postpartum. The magnitude of GnRH-induced release of LH (P = 0.82) or FSH (P = 0.86) did not differ between treatments. However, peak serum concentrations of estradiol during proestrus after treatment with PGF₂ were less (P = 0.04) in linoleate than control cows. In conclusion, fat supplementation with high-linoleate safflower seeds did not improve the development of ovarian follicles and detrimentally affected early postpartum fertility possibly because of a reduction in IGF-I concentrations in tissues essential to reproduction.

Key Words: cow • fat • reproduction