|Cushman, Robert - Bob|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 3/5/2012
Publication Date: 7/1/2012
Citation: Echternkamp, S.E., Eborn, D.R., Cushman, R.A. 2012. Reduced fertility in female progeny from beef heifers on dietary restriction during development [abstract]. Journal of Animal Science. 90 (Supplement 3):472 (Abstract #519).
Technical Abstract: Developing replacement heifers on lower energy diets does not affect fertility but may impart epigenetic effects on their progeny. Objective was to determine whether ovarian development or fertility is impeded in female progeny of replacement beef heifers developed on a lower energy diet. At 8 mo of age, Angus (n=40) or composite MARC II (n=40) heifers were assigned by BW and genetic line to be fed either a high (HE) or low (LE) energy diet for 180 d plus the first 22 d of the 47-d breeding period to achieve an ADG of either 0.45 or 0.9 kg/d or 55 vs. 65% of mature BW. Heifers within a line were mated to the same bulls. After breeding, treatment groups were combined and managed on pasture. Female progeny were developed on a standard heifer management protocol and bred at 14 mo of age. Total number of antral follicles (AFC), length and height of both ovaries, and uterine diameter were measured by transrectal ultrasonography in treated heifers (n=72), and subsequently in female progeny (n=32), at first breeding; pregnancy was diagnosed at about 75 d of gestation. At 14 mo of age, LE heifers were lighter (P < 0.01) than HE heifers (344.8 vs. 429.4 ± 7.1 kg). Progeny birth weight (36.4 kg) was not affected by diet or line but Angus progeny were lighter (P < 0.01) at breeding (362.1 ± 7.2 vs. 387.2 ± 5.6 kg). Progeny of LE dams had fewer antral follicles than HE progeny (19.0 ± 1.9 vs. 26.0 ± 1.7; P < 0.01), whereas AFC (22.5 ± 2.8) did not differ between LE and HE dams. Ovarian size (ovarian length x height) was not affected by diet but was greater (P < 0.05) for MARC II vs. Angus heifers in both generations (dams, 301.3 vs. 351.9 ± 3.5 mm2; progeny, 454.4 ± 31.8 vs. 586.3 ± 26.3 mm2, respectively). Uterine diameter (12.1 mm) was not influenced by diet. Pregnancy rate was less (P < 0.05) for progeny from LE vs. HE dams (42.6 ± 15.3 vs. 80.3 ± 10.1%) and for Angus vs. MARC II progeny (39.3 ± 14.3 vs. 80.2 ± 12.1%). Results indicated that environmental effects imposed during early embryonic development in first-parity heifers may affect embryonic gametogenesis and fertility of progeny.