ABSTRACT

Background and Aim: Ketosis is a prevalent metabolic disorder in dairy cows during the transition period, resulting in reduced productivity, impaired reproductive performance, and significant economic losses. Propylene glycol (PG) is widely used as a gluconeogenic precursor to mitigate negative energy balance and control ketosis. However, variations in farm-level health programs lead to inconsistent outcomes. This study aimed to comparatively evaluate the effectiveness of different PG-based health programs implemented across multiple commercial dairy farms. 

Materials and Methods: A multi-farm observational study was conducted on 480 multiparous Holstein cows from four commercial dairy farms in Heilongjiang Province, China. Data were collected at six time points from 7 days prepartum to 80–100 days postpartum. Parameters assessed included body condition score (BCS), milk yield, reproductive performance, disease incidence, and blood biochemical indicators such as glucose, β-hydroxybutyric acid, and insulin. Statistical analyses were performed using linear mixed models and Chi-square tests, with significance declared at p < 0.05. 

Results: Significant differences were observed among farms in metabolic status, production performance, and disease incidence. Farm A, which applied a targeted PG administration strategy based on ketosis diagnosis, maintained optimal BCS (~3.4), achieved the highest milk yield (46.3 kg/d at 80–100 days postpartum), and exhibited stable glucose and insulin concentrations. The incidence of ketosis in Farm A (28.9%) was lower than that in Farm D (>35%), which showed poorer metabolic control, higher disease incidence, and reduced reproductive performance. Farm B demonstrated the lowest ketosis incidence (20.0%) but relied on blanket PG administration. Economic analysis revealed that Farm A achieved the highest total economic benefit (¥166,823.69). 

Conclusion: Targeted and time-specific PG administration is more effective than blanket or inconsistent strategies in controlling ketosis and improving productivity in dairy cows. The PG health program implemented in Farm A represents a practical and economically efficient model for commercial dairy systems. Further controlled studies are required to validate these findings and optimize long-term PG application strategies. 

Keywords: body condition score, dairy cows, ketosis, metabolic disorder, negative energy balance, production performance, propylene glycol, transition period.