title: Effects of dietary fat and season on steroid hormonal profiles before parturition and on hormonal, cholesterol, triglycerides, follicular patterns, and postpartum reproduction in Brahman cows.
abstract: Spring-calving Brahman cows (S) artificially inseminated to Brahman, Angus, or Tuli sires and fall-calving Brahman cows (F) naturally bred to Brahman were allotted randomly to receive 3.74% (LF; n = 9 S and 6 F), 5.20% (MF; n = 8 S and 6 F), or 6.55% dietary fat (HF; n = 8 S). Diets were formulated to contain differing fatty acid concentrations and to be isocaloric and isonitrogenous. Cows were bled and fed twice daily from 2 wk before expected calving date through d 21 after calving. Ultrasonography was performed on d 14 and 21 after calving. From d 21 to 90 after calving a sterile bull equipped with a chin-ball marker was placed with the cows to aid in estrus detection. In both seasons progesterone decreased (P < .01) and estradiol-17 beta increased (P < .01) as parturition approached. Cows receiving MF and HF had increased (P < .01) total numbers of follicles compared to LF cows, and cows receiving MF had larger (P < .01) follicles. During the spring, cows receiving HF and cows bred to Brahman or Tuli sires had longer (P < .01) gestation lengths. Progesterone concentrations before calving were affected (P < .01) by treatment x sire and estradiol-17 beta by a time x treatment interaction (P < .01). Cholesterol after calving was higher (P < .01) in HF cows than in LF or MF cows. In the fall, LF cows had heavier (P < .01) calves than cows receiving MF. Birth weight was also affected (P < .01) by treatment x sex of calf. Progesterone was affected (P < .01) by treatment x sex of calf. Estradiol-17 beta was affected (P < .01) by sex of calf and treatment x sex of calf. Across seasons, by d 90 after calving, 9 of 15 (60%) LF and 11 of 15 (73.3%) MF cows showed estrual behavior. Cows in the spring had increased (P < .01) numbers and larger follicles compared to the fall. In conclusion, dietary fat may influence steroid hormone concentrations before calving, calf birth weight and postpartum follicular populations; furthermore, follicular populations may also be influenced by season.
authors.affiliation: Texas Agricultural Experiment Station, Overton 75684, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Lammoglia
authors.forename: S T
authors.initials: ST
authors.lastname: Willard
authors.forename: J R
authors.initials: JR
authors.lastname: Oldham
authors.forename: R D
authors.initials: RD
authors.lastname: Randel
mesh_terms: D000818:Animals; D001724:Birth Weight / Q000187:drug effects / Q000502:physiology; D001835:Body Weight / Q000187:drug effects / Q000502:physiology; D002417:Cattle / Q000097:blood* / Q000502:physiology*; D002784:Cholesterol / Q000097:blood*; D004041:Dietary Fats / Q000494:pharmacology*; D004958:Estradiol / Q000097:blood*; D005260:Female; D007743:Labor, Obstetric / Q000097:blood* / Q000502:physiology; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000494:pharmacology; D008297:Male; D019301:Oleic Acid / Q000494:pharmacology; D006080:Ovarian Follicle / Q000502:physiology*; D049590:Postpartum Period / Q000502:physiology*; D011247:Pregnancy; D018873:Pregnancy Rate; D011270:Pregnancy, Animal / Q000097:blood* / Q000502:physiology; D011374:Progesterone / Q000097:blood*; D011897:Random Allocation; D012621:Seasons; D012727:Sex Characteristics; D014280:Triglycerides / Q000097:blood*
chemical_list: D004041:Dietary Fats; D008041:Linoleic Acids; D014280:Triglycerides; D019301:Oleic Acid; D011374:Progesterone; D004958:Estradiol; D002784:Cholesterol; D019787:Linoleic Acid