title: Characterization of luteinizing hormone secretion in the primiparous, lactating sow: relationship to blood metabolites and return-to-estrus interval.
abstract: Lactating, primiparous Landrace x Yorkshire sows were used to characterize LH secretion during lactation in sows that experienced an early (less than 9 d; n = 14) or late (greater than 15 d; n = 9) return to estrous postweaning and to evaluate the relationship between LH secretion and blood metabolites. Twenty-three sows were fed one of nine corn-soybean meal diets to achieve a matrix of lysine (15 to 45 g/d) and energy (6.5 to 16.5 Mcal of ME/d) intakes and a range in metabolite concentrations and return-to-estrus intervals. Blood samples for LH analysis were collected every 15 min for 6 h on d 0, 7, 14, 21, and 28 of lactation. Circulating concentrations of glucose, amino acids, insulin, triglycerides, urea N, and nonesterified fatty acids also were measured on d 7 and 21. Mean LH concentrations were .27 and .42 ng/mL at farrowing for sows with an early and late return to estrus, respectively, but decreased (P less than .01) to .12 ng/mL by d 7 in both early and late groups. Mean LH and number of LH peaks per 6 h increased linearly (P less than .01) from d 7 to 28 for early sows. Early sows had a higher LH mean and more LH peaks per 6 h on d 14, 21, and 28 than did late sows (P less than .05). Early sows had higher serum insulin on d 7 (P less than .05) and d 21 (P less than .01) than did late sows. Concentrations of other metabolites did not differ (P less than .10) between early and late sows.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Animal Science, University of Minnesota, St. Paul 55108.
authors.forename: M D
authors.initials: MD
authors.lastname: Tokach
authors.forename: J E
authors.initials: JE
authors.lastname: Pettigrew
authors.forename: G D
authors.initials: GD
authors.lastname: Dial
authors.forename: J E
authors.initials: JE
authors.lastname: Wheaton
authors.forename: B A
authors.initials: BA
authors.lastname: Crooker
authors.forename: L J
authors.initials: LJ
authors.lastname: Johnston
mesh_terms: D000596:Amino Acids / Q000097:blood; D000821:Animal Feed; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001806:Blood Urea Nitrogen; D002149:Energy Intake; D004971:Estrus / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D007328:Insulin / Q000097:blood; D007774:Lactation / Q000097:blood / Q000378:metabolism* / Q000502:physiology; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D008239:Lysine / Q000008:administration & dosage; D012044:Regression Analysis; D013552:Swine / Q000097:blood / Q000378:metabolism* / Q000502:physiology; D014280:Triglycerides / Q000097:blood
chemical_list: D000596:Amino Acids; D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D014280:Triglycerides; D007986:Luteinizing Hormone; D008239:Lysine