title: Pregnancy, bovine somatotropin, and dietary n-3 fatty acids in lactating dairy cows: I. Ovarian, conceptus, and growth hormone-insulin-like growth factor system responses.
abstract: The objective was to examine effects of bovine somatotropin (bST), pregnancy, and dietary fatty acids on reproductive responses in lactating dairy cows. Beginning at approximately 17 d in milk (DIM), a comparison was made of isoenergetic diets comprising supplementary lipids of whole cottonseed vs. calcium salts of fish oil enriched lipid (FO). Ovulation was synchronized in cows with a presynchronization plus Ovsynch protocol, and cows were inseminated artificially by appointment or not inseminated (d 0 = time of synchronized ovulation; 77 +/- 12 DIM). On d 0 and 11, cows received bST (500 mg) or no bST. All cows were slaughtered on d 17. Number of cows in each group was as follows: control diet had 5 bST-treated cyclic (bST-C), 5 non-bST-treated cyclic (no bST-C), 4 bST-treated pregnant (bST-P), and 5 non-bST-treated pregnant (no bST-P) cows; and cyclic cows fed FO diet had 4 bST-treated (bST-FO) and 5 non-bST-treated cyclic (no bST-FO-C) cows. Feeding FO increased milk production, number of class 1 follicles (2 to 5 mm), and decreased insulin during the period before d 0 compared with control-fed cows. The bST increased milk production, pregnancy rate [83% (5/6) vs. 40% (4/10)], conceptus length (45 vs. 34 cm), and interferon-tau in the uterine luminal flushings (9.4 vs. 5.3 microg) with no effect on interferon-tau mRNA concentration in the conceptus. Treatment with bST increased plasma growth hormone (GH) and insulin-like growth factor (IGF)-I. Among control-fed cows (cyclic and pregnant), bST decreased progesterone concentration in plasma. Cows fed FO had less plasma insulin than control-fed cyclic cows, and FO altered the plasma GH (bST-FO > bST-C) and IGF-I (bST-C > bST-FO-C) responses to bST injections. Endometrial IGF-I mRNA was reduced in pregnant cows and tended to decrease in those fed FO. The IGF-II mRNA was increased in the endometrium of pregnant and bST-treated cows fed the control diet. Cows fed FO had increased concentrations of IGF-II mRNA, when bST was not injected. The insulin-like growth factor binding protein-2 (IGFBP-2) mRNA was increased in bST-P cows, whereas bST decreased the IGFBP-2 mRNA in all cyclic cows. In summary, bST and FO seemed to modulate reproductive responses that may be beneficial to the developing conceptus and pregnancy rate.
authors.affiliation: Department of Animal Sciences, University of Florida, Gainesville, Florida 32611, USA.
authors.forename: T R
authors.initials: TR
authors.lastname: Bilby
authors.forename: A
authors.initials: A
authors.lastname: Sozzi
authors.forename: M M
authors.initials: MM
authors.lastname: Lopez
authors.forename: F T
authors.initials: FT
authors.lastname: Silvestre
authors.forename: A D
authors.initials: AD
authors.lastname: Ealy
authors.forename: C R
authors.initials: CR
authors.lastname: Staples
authors.forename: W W
authors.initials: WW
authors.lastname: Thatcher
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000818:Animals; D002417:Cattle / Q000196:embryology / Q000502:physiology*; D003612:Dairying; D004032:Diet / Q000662:veterinary; D004041:Dietary Fats / Q000494:pharmacology*; D004622:Embryo, Mammalian / Q000187:drug effects; D005260:Female; D005395:Fish Oils / Q000008:administration & dosage; D013006:Growth Hormone / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D006728:Hormones / Q000097:blood; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000187:drug effects*; D007774:Lactation / Q000187:drug effects; D010053:Ovary / Q000000981:diagnostic imaging / Q000187:drug effects / Q000502:physiology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D011374:Progesterone / Q000097:blood; D012044:Regression Analysis; D012098:Reproduction / Q000187:drug effects; D013997:Time Factors; D014463:Ultrasonography; D014599:Uterus / Q000187:drug effects / Q000502:physiology
chemical_list: D004041:Dietary Fats; D005395:Fish Oils; D006728:Hormones; D007328:Insulin; D011374:Progesterone; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone