Personne :
Laforest, Jean-Paul

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Université Laval. Vice-rectorat aux ressources humaines
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  • Publication
    Uterine morphology and reproductive phenomena in relation to number of embryos, at different stages of gestation in prolific sheep
    (Elsevier, 2003-09-30) Fahmy, M. H.; Laforest, Jean-Paul; Castonguay, François
    Forty prolific ewes of which half were superovulated with 800 IU PMSG were slaughtered on either d 30, d 70 of gestation or d 3-5 post-partum. At each slaughter date, the ewes were balanced for number of ovulations ( 1 to > 3 at d 30) or embryos ( 1 to 4 at d 70 and d 3-5 post-partum). Uterine length, width, surface and dry matter (DM) ; embryonic weight and DM; plasma progesterone at d 15 and 30 of gestation; and protein concentration in allantoic fluids were measured. Superovulated ewes averaged 5.8 CL vs. 3.1 CL for the control. On d 15 of gestation, plasma progesterone concentration increased from 4.87 ng/ml in ewes with 2 CL to 8.02 ng / ml for those with > 7 CL. The corresponding figures at d 30 were 4.19 and 9.44 ng / ml, respectively. Embryonic losses increased from 16.5% in ewes with 2 CL to 67.9% in those with > 7 CL. Length of uterine horns increased by 9.2, 7.7 and 4.1 cm for each increase in number of embryos present at the three slaughter dates, respectively. On d 30, only embryo DM showed a significant (P <0.05) increase with increased number of embryos present. On d 70, length, width and uterine surface increased linearly with increase in number of embryos, however, little difference was observed between ewes carrying three and four embryos. Ewes slaughtered after they had lambed one, two or three lambs had significantly smaller and narrower uteri than those with four lambs. It is concluded that, in prolific as in non-prolific sheep the space available seems to be adequate for development of all embryos surviving the critical first 30 days of pregnancy.
  • Publication
    Effects of intramuscular administration of folic acid and vitamin B 12 on granulosa cells gene expression in postpartum dairy cows
    (Elsevier, 2015-11-01) Khan, Daulat Raheem; Laforest, Jean-Paul; Girard, Christiane; Gagnon, Annie; Richard, François J.; Sirard, Marc-André
    The fertility of dairy cows is challenged during early lactation, and better nutritional strategies need to be developed to address this issue. Combined supplementation of folic acid and vitamin B12 improve energy metabolism in the dairy cow during early lactation. Therefore, the present study was undertaken to explore the effects of this supplement on gene expression in granulosa cells from the dominant follicle during the postpartum period. Multiparous Holstein cows received weekly intramuscular injection of 320 mg of folic acid and 10 mg of vitamin B12 (treated group) beginning 24 (standard deviation = 4) d before calving until 56 d after calving, whereas the control group received saline. The urea plasma concentration was significantly decreased during the precalving period, and the concentration of both folate and vitamin B12 were increased in treated animals. Milk production and dry matter intake were not significantly different between the 2 groups. Plasma concentrations of folates and vitamin B12 were increased in treated animals. Daily dry matter intake was not significantly different between the 2 groups before [13.5 kg; standard error (SE) = 0.5] and after (23.6 kg; SE = 0.9) calving. Average energy-corrected milk tended to be greater in vitamin-treated cows, 39.7 (SE = 1.4) and 38.1 (SE = 1.3) kg/d for treated and control cows, respectively. After calving, average plasma concentration of β-hydroxybutyrate tended to be lower in cows injected with the vitamin supplement, 0.47 (SE = 0.04) versus 0.55 (SE = 0.03) for treated and control cows, respectively. The ovarian follicle ≥12 mm in diameter was collected by ovum pick-up after estrus synchronization. Recovered follicular fluid volumes were greater in the vitamin-treated group. A microarray platform was used to investigate the effect of treatment on gene expression of granulosa cells. Lower expression of genes involved in the cell cycle and higher expression of genes associated with granulosa cell differentiation before ovulation were observed. Selected candidate genes were analyzed by reverse transcription quantitative PCR. Although the effects of intramuscular injections of folic acid and vitamin B12 on lactational performance and metabolic status of animals were limited, ingenuity pathway analysis of gene expression in granulosa cells suggests a stimulation of cell differentiation in vitamin-treated cows, which may be the result of an increase in LH secretion.