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Controlled trial of the effect of negative dietary cation-anion difference on postpartum health and culling of dairy cows.

R. Couto Serrenho


Controlled trial of the effect of negative dietary cation-anion difference on postpartum health and culling of dairy cows.
R. Couto Serrenho*1, T. C. Bruinje1, E. I. Morrison1, T. J. DeVries2, T. F. Duffield1, S. J. LeBlanc1. 1Department of Population Medicine, University of Guelph Guelph, ON, Canada, 2Department of Animal Biosciences, University of Guelph Guelph, ON, Canada.

The objective of this study was to assess the effects of a negative dietary cation-anion difference (DCAD) dry cow diet on postpartum health and culling. Cows from 4 commercial dairy farms in Ontario, Canada were enrolled in a randomized controlled trial from November 2017 to April 2019. Close-up pens (1 per farm) with cows 3 wk before expected calving were randomly assigned to a negative DCAD (TRT; −100 mEq/kg DM; target urine pH 6.0—6.5) or a control diet (CON; +95 mEq/kg DM with a placebo supplement). Each pen was fed TRT or CON for 3 mo (one period) then switched to the other treatment for the next period, with 4 periods per farm. Body condition score (BCS) was measured at enrollment and urine pH was measured weekly until calving. Data from 1086 animals (TRT: n = 681; CON: n = 405) that received the assigned diet for >2 wk were included. The incidence of milk fever (MF), retained placenta (RP), metritis, ketosis (blood BHB >1.2 mmol/L, measured weekly in wk 1 and 2), clinical mastitis <30 DIM (CM), displaced abomasum (DA), purulent vaginal discharge (PVD, assessed once at wk 5), ≥ 1 disease (DIS) or culling by 35 DIM were analyzed with logistic regression models with treatment, parity, BCS, and their interactions, accounting for pen-level randomization and clustering of animals within farm with random effects. There were no interactions of treatment with parity or BCS for any outcome. There were only 43 cases of MF, allowing only univariable analysis. The incidence of MF was 5 � 3% in CON and 1 � 1% in TRT (P = 0.18). There were no treatment effects (CON vs TRT, LSM � SE) on RP (7 � 3%; 6 � 2%; P = 0.71), metritis (11 vs 12%; SE = 4; P = 0.83), ketosis (21 vs 23%; SE = 4; P = 0.59, PVD (13 vs 12%; SE = 3; P = 0.51), or DIS (44 vs 41%; SE = 7; P = 0.41). Cows fed TRT had lesser incidence of CM (4 vs 2%; SE = 1, P = 0.09) and DA (3 vs 1%; SE = 1, P = 0.05). Culling <35 DIM tended to be greater in CON (7 � 2%) than TRT (5 � 1%, P = 0.11). Under commercial herd conditions, a negative DCAD fed 3 wk before parturition improved some but not all health outcomes assessed.

Keywords: milk fever, transition cow, nutrition.

Biography: Dr. Rita Couto Serrenho is a DVSc candidate at the Department of Population Medicine at the University of Guelph. She grew up in Portugal, completing both her DVM and MSc in Bovine Mastitis at the Faculty of Veterinary Medicine at the University of Lisbon in 2015. Her MSc research focused on the economics of mastitis and management practices for mastitis control. In 2016, Rita joined a farm animal practice in South Wales in the UK, working primarily in dairy cattle services. At the University of Guelph, Rita works for the Ruminant Field Services, OVC while completing her DVSc program with Dr. LeBlanc on transition cow diseases.