title: Effects of dietary rice bran, lasalocid, and sex of calf on postpartum reproduction in Brahman cows.
abstract: To determine the effects of dietary lasalocid and increased dietary fat on reproduction, multiparous Brahman cows (n = 68), body condition score (BCS) of 6.2 +/- 0.7 and BW of 500.9 +/- 42.6 kg, were randomly assigned within sex of calf to receive one of four rations. All treatment groups grazed Coastal bermudagrass overseeded with rye-ryegrass and were given ad libitum access to hay and water. The control (n = 17) group received 4.17 kg x d(-1) x cow(-1) of 4:1 corn:soybean meal. The rice bran (n = 17) group received 4.35 kg x d(-1) x cow(-1) of 3:1:1 corn:soybean meal:rice bran (5.2% dietary fat). The lasalocid (n = 17) group received the Control diet with the addition of 200 mg of lasalocid x d(-1) x cow(-1). The rice bran-lasalocid (n = 17) group received the rice bran diet with the addition of 200 mg of lasalocid x d(-1) x cow(-1). Diets were fed once daily from d 1 after parturition through the detection of first estrus. Weight and BCS of cows and BW of calves were recorded at 14-d intervals from d 1 after parturition through detection of first estrus and at weaning. Cows were bled on d 1, 3, 5, 7, and 14 and at weekly intervals until estrus and on d 7 and d 10 after estrus. Ovarian follicular populations were monitored by transrectal ultrasonography weekly from d 14 after parturition through detection of first estrus. Plasma 13-14-dihydro-15-ketoprostaglandin-F2alpha (PGFM) and progesterone (P4) concentrations were quantified using RIA. Concentrations of PGFM from d 1 to 7 and P4 concentrations on d 7 and 10 after estrus were not influenced (P > 0.10) by diet or sex of calf. Changes in BW and BCS were not affected (P > 0.10) by diet. The number of medium-sized follicles tended to be greater (P < 0.06) in Controls than in cows on lasalocid or rice bran + lasalocid treatments on d 21. Cumulative return to estrus with a functional corpus luteum by d 60 postpartum was greater (P < 0.02) in the rice bran (70.6%) and lasalocid groups (76.5%) than in Controls (52.9%) or the group given rice bran + lasalocid (25.0%). Normal first estrous cycles were less likely (P < 0.07) to be exhibited in cows given rice bran + lasalocid than in other groups. Intervals from calving to corpus luteum formation, functional corpus luteum, and first P4 > or = 1 ng/mL were longer (P < 0.02) in cows given rice bran + lasalocid than in other cows. Combining increased dietary fat (5.2%) with lasalocid lengthened the time to reproductively important events.
authors.affiliation: Texas Agricultural Experiment Station, Overton 75684, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Webb
authors.forename: A W
authors.initials: AW
authors.lastname: Lewis
authors.forename: D A
authors.initials: DA
authors.lastname: Neuendorff
authors.forename: R D
authors.initials: RD
authors.lastname: Randel
mesh_terms: D000821:Animal Feed; D000818:Animals; D001835:Body Weight; D002417:Cattle / Q000502:physiology*; D004041:Dietary Fats / Q000008:administration & dosage*; D004972:Estrus Detection; D005260:Female; D006728:Hormones / Q000097:blood; D007476:Ionophores / Q000008:administration & dosage*; D007832:Lasalocid / Q000008:administration & dosage*; D008297:Male; D012275:Oryza; D006080:Ovarian Follicle / Q000502:physiology; D010938:Plant Oils / Q000008:administration & dosage; D049590:Postpartum Period / Q000187:drug effects / Q000502:physiology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000187:drug effects / Q000502:physiology*; D011897:Random Allocation; D012098:Reproduction; D000073879:Rice Bran Oil; D012737:Sex Factors
chemical_list: D004041:Dietary Fats; D006728:Hormones; D007476:Ionophores; D010938:Plant Oils; D000073879:Rice Bran Oil; D007832:Lasalocid