Understanding the role of diets enriched in long chain fatty acids on postpartum reproductive function and embryo development in dairy cows

• Author / Creator

  Salehi Karashk, Reza

• The objectives of this work were to investigate the influence of diets enriched in long chain fatty acids on feed intake, calf birth weight, maternal and neonatal fatty acid profiles, milk production, postpartum reproductive function, early embryonic development and its transcriptome profile in dairy cows. In previous research, the interval from calving to first ovulation was longer in cows given prepartum diets supplemented with canola (high oleic acid) seed than in those fed diets supplemented with linola (high linoleic acid) or flax (high α-linolenic acid) seed. A longer interval from calving to first ovulation is associated with reduced postpartum fertility. Since canola is a common ingredient in dairy cow rations in western Canada, it was important to further investigate the reported detrimental effect of a canola-based diet on the interval from calving to first ovulation in dairy cows. My first study was designed to understand the mechanisms by which first ovulation was delayed in canola fed cows. I hypothesized that luteinizing hormone (LH) pulsatility and pituitary responsiveness to gonadotropin releasing hormone (GnRH), early postpartum, would be reduced in cows fed canola prepartum. Results of the first study did not support my hypothesis. In the second study, the effects of prepartum supplemental fat (no-oilseed vs. oilseed) and the source of fat (canola vs. sunflower seed) on gestation length, calf weight, milk production and postpartum reproductive function were evaluated. Prepartum oilseed supplementation reduced dry matter intake during pre and postpartum periods in multiparous cows with an associated decrease in milk yield. It also increased gestation length, female calf birth weight and postpartum reproductive disorders without affecting ovarian function including the interval from calving to first ovulation postpartum, and fertility. In the third study, I evaluated the effects of dietary fat (oilseeds vs. control) and the type of supplemental fat (canola vs. sunflower) during late gestation on maternal and neonatal plasma fatty acids, and expression of fatty acid transporter genes in placental cotyledonary tissue. Maternal LCPUFA, neonatal total n-3 fatty acids, eicosapentaenoic (EPA) and docosahexaenoic (DHA) were reduced following fat supplementation prepartum. Additionally, fatty acid protein transporter 4 (FATP4) and fatty acid translocase (FAT/CD36) mRNA expression was also lower in cotyledonary tissues of cows fed supplemental fat than control. I concluded that reduced total n-3 fatty acids, EPA and DHA in plasma of neonates born of dams fed fat prepartum was likely due to reduced expression of placental FATP4 and FAT/CD36. In the final study, I investigated the effect of dietary long-chain fatty acids on the development and gene expression of in vivo- and in vitro-derived embryos. Feeding cows a diet supplemented with flax seed reduced the proportion of degenerated embryos than those fed canola or sunflower possibly through altered expression of up to 175 genes, of which, many were involved in cell survival and viability. Supplementation of serum harvested from cows fed flax or sunflower seed to embryo culture medium in vitro, did not affect embryo development. Hence, I concluded that the reduced proportion of degenerated embryos seen in cows fed flaxseed likely resulted from enhanced oocyte competence than post-fertilization embryo development. In summary, a canola-based prepartum diet did not have any detrimental effects on postpartum ovarian function. Prepartum dietary oilseed supplementation not only reduced dry matter intake and milk production in multiparous cows but also increased birth weight, reduced essential fatty acids in newborn calf blood and increased postpartum reproductive disorders. Feeding cows a diet enriched in n-3 polyunsaturated fatty acids (flax seed) during the breeding period reduced the proportion of degenerated embryos likely by altering the expression of embryonic genes improving cell survival and viability.

• Subjects / Keywords

  • Placenta
  • Dairy cows
  • Embryo
  • Flax
  • Calf
  • Reproduction
  • Oilseed
  • Fatty acids
  • Canola
  • Sunflower

• Graduation date

  Spring 2016

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3377610S

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.