1449
Effect of periconceptual growth hormone injection on feed intake and early fetal development in ewes
Researchers have reported improved birth weight and numbers of lambs from ewes treated with growth hormone (GH) at the time of breeding. Therefore, our hypothesis was that the administration of GH at time of breeding could increase DMI which consequently could result in greater early development of the fetus. Thirteen individually-penned ewes (mean BW = 69.8±3.14 kg and BCS = 3.2±0.13 [1-5 scale]) were fed a pelleted diet (CP 12.88%, ash 6.48%, fat 1.69%, NDF 37.86%, ADF 23.83% of DM) for ad libitum intake. Estrus was synchronized by administering 2 doses of prostaglandin F2α(PGF) 11 d apart. At the second dose of PGF, six ewes were injected IM with GH (500 mg) and seven ewes with saline solution (control). The ewes in both treatments were exposed to the same ram at 0700 and 1900 and allowed to breed. Doppler ultrasound measurements were taken on days 25, 30, 40, and 50 of gestation for fetal length, fetal width, kidney length, kidney width, placentome size, biparietal distance and umbilical blood flow (BF; at day 50 of gestation). Data were analyzed in Proc Mixed (SAS; 2011) to test for the effects of treatment, day and treatment × day. No differences between treatments were observed for BW (P = 0.16), BCS (P = 0.54) and DMI (P = 0.84) after injection of GH. There was a day effect (P < 0.05) for fetal length, fetal width, kidney length, placentome size, and biparietal distance with all increasing as gestation advanced. No difference (P > 0.05) was observed between treatments for any ultrasound measurements. Growth hormone administration did not influence DMI or conceptus development as measured using ultrasonography. It is still unknown how periconceptual GH treatment could enhance growth and development of the conceptus, or umbilical BF, after d 50 of gestation when exponential growth of the fetus occurs.
Keywords:
Ewe; Growth Hormone; Ultrasound