Influences of supplemental fat, differing in fatty-acid composition, on performance, plasma fatty-acid content, and reproduction of developing beef heifers

Angus × Simmental, fall-born heifers (n = 120, yr 1, and n = 160, yr 2) were used to determine the effects of supplemental fat, differing in fatty-acid composition, on performance, plasma fatty-acid content, and reproduction of developing beef heifers. At 7 mo of age, heifers were randomly allotted to 1 of 4 supplements containing whole raw soybeans (SY); corn, soybean meal, and OmegaFlax (FLX); corn, soybean meal, and Energy Booster 100 (EB); or corn- soybean meal (CON). The SY, FLX, and EB supplements (FT) were formulated to have the same level of crude fat. The SY-supplemented heifers gained less (P = 0.04) BW than did FLX-supplemented heifers. The FT-supplemented heifers tended (P = 0.06) to gain more BW than did the heifers fed the CON supplement. The SY-supplemented heifers had greater (P < 0.001) humeral concentration of 18:2n-6 cis than did FLX- or EB-supplemented heifers. The FLX-supplemented heifers had greater (P < 0.001) humeral concentration of 18:3n-3. +. n-6 than did the SY-supplemented heifers. There were no differences in percentage of pubertal heifers at 10, 12, or 14 mo of age. The heifers fed the CON supplement tended (P = 0.09) to have higher overall pregnancy rates than did the FT-supplemented heifers. Feeding soybeans to developing heifers increased plasma linoleic acid but did not affect reproductive performance compared with other fat sources. Although fat supplementation tended to improve heifer BW gains, it tended to result in poorer overall pregnancy rates compared with the control supplement.