title: Reproductive performance of dairy cows is influenced by prepartum feed restriction and dietary fatty acid source.
abstract: The objective of this study was to determine the effects of feed restriction and source of dietary fatty acids during the close-up dry period on postcalving reproductive performance of dairy cattle. Thirty-four days before expected calving, pregnant Holstein cows (n = 72; parity 1 to 5) were randomly assigned to 1 of 6 treatments. Treatments were ad libitum (AL) or 24% feed restriction (FR) in combination with 1 of 3 oilseed supplements at 8% of diet dry matter: canola, linola, or flax to enrich the rations with oleic, linoleic, or linolenic fatty acids, respectively. After calving, cows were fed a common lactation diet that contained no oilseeds. Measurements of uterus, corpus luteum, and follicles were obtained by ultrasonography twice weekly from 7 +/- 1 d after calving until the first ovulation. Cows (n = 66) were subjected to timed artificial insemination (TAI), and pregnancy was determined 32 d later. Feed-restricted cows had lower dry matter intake and lost more body weight prepartum. Energy balance (Mcal/d) was negative in FR cows prepartum but they had a less severe negative energy balance postpartum. The dietary source of fatty acid did not affect energy balance. Cows fed AL had a higher incidence of uterine infections (10/37 vs. 2/35) but tended to have fewer ovarian cysts (2/37 vs. 7/35) than FR cows. Mean (+/-SE) interval from calving to uterine involution did not differ among dietary treatments (26.8 +/- 1.8 d). Interval from calving to first ovulation was longer in cows fed canola than in those fed either linola or flax (34.7 +/- 3.1 vs. 23.7 +/- 3.2 and 21.0 +/- 3.1 d, respectively). A greater percentage of cows fed AL conceived to the first TAI (47.1 vs. 18.8) and tended to have fewer mean days open (157 +/- 10.8 vs. 191 +/- 10.1) than cows fed FR. In summary, FR cows had a lower incidence of uterine infections, but they were less fertile as reflected by a lower percent pregnancy to first TAI and increased days open. Cows fed diets enriched in linoleic or linolenic fatty acids had a lesser incidence of ovarian cysts and ovulated sooner with no effect on energy balance or fertility.
authors.affiliation: Dairy Research and Technology Centre, Alberta Agriculture and Rural Development, Edmonton, Alberta, T6H 5T6, Canada.
authors.forename: M G
authors.initials: MG
authors.lastname: Colazo
authors.forename: A
authors.initials: A
authors.lastname: Hayirli
authors.forename: L
authors.initials: L
authors.lastname: Doepel
authors.forename: D J
authors.initials: DJ
authors.lastname: Ambrose
mesh_terms: D000818:Animals; D001824:Body Constitution; D001835:Body Weight; D031204:Caloric Restriction / Q000662:veterinary*; D002417:Cattle; D003612:Dairying / Q000379:methods*; D004032:Diet / Q000662:veterinary*; D004041:Dietary Fats / Q000008:administration & dosage*; D004435:Eating; D004734:Energy Metabolism; D005227:Fatty Acids / Q000008:administration & dosage*; D005260:Female; D006728:Hormones / Q000097:blood; D007774:Lactation / Q000502:physiology; D011247:Pregnancy; D011897:Random Allocation; D012098:Reproduction / Q000502:physiology*; D013997:Time Factors
chemical_list: D004041:Dietary Fats; D005227:Fatty Acids; D006728:Hormones