title: A prepartum diet supplemented with oilseeds high in oleic or linoleic acid reduced GnRH-induced LH release in dairy cows during second week postpartum.
abstract: BACKGROUND
  The objective was to determine the effect of prepartum diets supplemented with rolled canola seed (high in oleic acid) or sunflower seed (high in linoleic acid) on luteinizing hormone (LH) pulsatility and gonadotropin releasing hormone (GnRH)-induced LH release during early postpartum.
  
  
  METHODS
  Thirty-one pregnant Holstein cows, blocked by body condition score, parity and expected calving date, were assigned to 1 of 3 prepartum diets supplemented with 8 % rolled canola or sunflower seed, or no oilseed (control) during the last 35 d of gestation. Blood samples were collected at Weeks (wk)-3, 0, +1 and +2, relative to calving, to determine non-esterified fatty acids (NEFA), Beta-hydroxy butyric acid (BHBA) and glucose. Additional blood samples were collected during wk1 (n = 5 per treatment) or wk2 (n = 5 or 6 per treatment), for 6 h, to measure LH pulsatility; thereafter, 100 mcg GnRH was administrated i.m., and blood was sampled for 4 h more, to measure GnRH-induced LH release.
  
  
  RESULTS
  Dietary treatment did not affect prepartum energy balance, but cows fed the control diet were in a deeper state of negative energy balance during wk2, than those fed canola (P = 0.03) or sunflower (P = 0.01). Prepartum diets did not influence the mean plasma concentration of BHBA and glucose. However, NEFA concentration during wk2 was greater in control cows than those fed sunflower (P = 0.03) or canola (P = 0.07). Prepartum diets did not affect LH pulsatility (i.e. mean, minimum, maximum concentration, pulse frequency, and amplitude during wk1 and 2). GnRH-induced LH release did not differ among dietary treatments during wk1 but the mean GnRH-induced LH release during wk2 was either greater (P = 0.02) and tended to be greater (P = 0.09) in control cows than in those fed canola and sunflower, respectively.
  
  
  CONCLUSIONS
  Prepartum diets did not affect LH pulsatility and GnRH-induced LH release during the first week postpartum, but cows fed a diet supplemented with oilseeds high in oleic or linoleic acid released less LH than control cows, in response to an exogenous GnRH challenge during the second week postpartum.
authors.affiliation: Department of Agricultural, Food and Nutritional Science, University of Alberta, T6G 2P5, Edmonton, AB, Canada. rsalehi1@ualberta.ca.
authors.forename: Reza
authors.initials: R
authors.lastname: Salehi
authors.affiliation: Livestock Research Branch, Alberta Agriculture and Rural Development, T6H 5 T6, Edmonton, AB, Canada. marcos.colazo@gov.ab.ca.
authors.forename: Marcos G
authors.initials: MG
authors.lastname: Colazo
authors.affiliation: Department of Agricultural, Food and Nutritional Science, University of Alberta, T6G 2P5, Edmonton, AB, Canada. moba@ualberta.ca.
authors.forename: Masahito
authors.initials: M
authors.lastname: Oba
authors.affiliation: Department of Agricultural, Food and Nutritional Science, University of Alberta, T6G 2P5, Edmonton, AB, Canada. divakar.ambrose@gov.ab.ca.|Livestock Research Branch, Alberta Agriculture and Rural Development, T6H 5 T6, Edmonton, AB, Canada. divakar.ambrose@gov.ab.ca.
authors.forename: Divakar J
authors.initials: DJ
authors.lastname: Ambrose
mesh_terms: D000818:Animals; D001786:Blood Glucose; D002417:Cattle; D004032:Diet / Q000662:veterinary*; D019587:Dietary Supplements; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D007774:Lactation; D019787:Linoleic Acid / Q000008:administration & dosage*; D007986:Luteinizing Hormone / Q000097:blood*; D019301:Oleic Acid / Q000008:administration & dosage*; D049590:Postpartum Period / Q000097:blood / Q000187:drug effects*; D011247:Pregnancy
chemical_list: D001786:Blood Glucose; D019301:Oleic Acid; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D019787:Linoleic Acid