The effect of monopropylene glycol on milk production, uterine health, and reproductive performance in cows diagnosed with hyperketonemia on 3 pasture-based dairy farms

In housed systems, administration of oral monopropylene glycol (MPG) in postpartum cows increases the likelihood that cows resolve hyperketonemia (HYK), reduces the incidence of clinical ketosis, and improves milk production, uterine health, and reproductive performance. The objective of our study was to investigate the efficacy of MPG as a treatment for hyperketonemia (blood BHB 1.2 to 2.9 mmol/L) and its effects on milk production, uterine health, and reproductive performance in 3 seasonal-calving, pasture-based dairy herds in New Zealand. Cows were tested a maximum of 15 times for HYK (3 times weekly on Monday, Wednesday, and Friday; mean ± SD; 14.9 ± 0.4 tests) from 1 to 35 DIM using a handheld meter. In total, 749 (76.4%) of 980 cows sampled were diagnosed with HYK (blood BHB ≥1.2 to 2.9 mmol/L) or severe HYK (blood BHB ≥3.0 mmol/L) at least once during the first 35 DIM. Cows that never tested above 1.2 mmol/L were classified as non-HYK (n = 231) and were excluded from the study. Cows with HYK that were randomly allocated to the control group (n = 362) were left untreated, whereas those allocated to the MPG treatment group (n = 387) were orally drenched with 300 mL of MPG (equivalent dose 310 g) every time the BHB test was ≥1.2 to 2.9 mmol/L during the first 35 DIM (mean ± SD treatment bouts per cow: 2.0 ± 1.2 bouts). The MPG treatment was repeated once daily until blood BHB was <1.2 mmol/L at subsequent tests. Data from the survival analysis indicated that MPG reduced the time to resolve HYK (blood BHB <1.2 mmol/L) and delayed time to onset of severe HYK. The MPG-treated cows were 52% more likely (hazard ratio [HR] = 1.52, 95% CI: 1.30–1.76) to resolve HYK and 69% less likely (HR = 0.31, 95% CI: 0.17–0.58) to develop severe HYK compared with control cows. However, repeated measures analysis indicated that MPG-treated cows had marginally lower ECM yield in the first 15 wk in milk (24.7 ± 0.24 kg/d) compared with control cows (25.1 ± 0.24 kg/d). Logistic regression was used to determine the effect of MPG on uterine health and reproductive performance. The prevalence of purulent vaginal discharge endometritis (score ≥3) was lower in MPG (n = 9/350) compared with control cows (n = 19/301). There were no overall effects of treatment on risk of submission to artificial insemination (AI) within 21 d of breeding start, confirmed pregnancy to first AI, pregnant within 42 d of breeding start, or the entire seasonally defined breeding period. Treating HYK with MPG improved the likelihood of a cow resolving HYK and reduced the incidence of severe HYK; however, there were minimal benefits for improving uterine health and reproductive performance and a biologically small difference in milk production in cows diagnosed with HYK based on a threshold of 1.2 mmol/L and treated with MPG.