title: The effect of pasture nitrate concentration and concentrate intake after turnout on embryo growth and viability in the lactating dairy cow.
abstract: This study investigated the effects on embryo growth and survival rate of feeding heavily-fertilised spring grass, containing high levels of quickly-degradable nitrogen, to pregnant cows. Forty-eight lactating Holstein cows between 2 and 8 weeks pregnant were turned-out, after a one-week transition period onto high- or low-nitrate pasture and fed a high- or low-concentrate supplement. Cows grazing the High nitrate pasture had significantly higher milk and plasma urea concentrations than cows grazing the Control pasture, while cows which were fed less concentrate had a notably higher plasma ammonia. However, there was no evidence that an increased quickly-degradable nitrogen (QDN) intake from pasture affected embryo survival or growth from 20 days onwards. This suggests that the impact of turnout on fertility mainly affects ovulation, fertilisation and/or the early embryo.
authors.affiliation: VSC Dumfries, St Mary's Industrial Estate, Dumfries, UK. r.laven@ed.sac.ac.uk
authors.forename: R A
authors.initials: RA
authors.lastname: Laven
authors.forename: H J
authors.initials: HJ
authors.lastname: Biggadike
authors.forename: R D
authors.initials: RD
authors.lastname: Allison
mesh_terms: D000641:Ammonia / Q000097:blood; D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D001823:Body Composition; D001835:Body Weight; D002417:Cattle / Q000196:embryology* / Q000502:physiology; D005314:Embryonic and Fetal Development / Q000187:drug effects; D005260:Female; D005308:Fertilizers / Q000032:analysis; D005313:Fetal Death / Q000139:chemically induced; D005865:Gestational Age; D007774:Lactation; D008431:Maternal-Fetal Exchange; D008892:Milk / Q000737:chemistry; D009566:Nitrates / Q000008:administration & dosage* / Q000009:adverse effects / Q000032:analysis; D006109:Poaceae; D011247:Pregnancy; D011374:Progesterone / Q000032:analysis; D014508:Urea / Q000032:analysis / Q000097:blood
chemical_list: D005308:Fertilizers; D009566:Nitrates; D011374:Progesterone; D000641:Ammonia; D014508:Urea