Among farm variation in heifer BW gains

Area of Science:

• Animal Science
• Dairy Cattle Management
• Reproductive Biology

Background:

• Body weight (BW) of replacement heifers is a critical indicator of future productivity but is infrequently measured on commercial farms.
• Lack of consistent BW measurement impedes the assessment of calf growth management strategies and their impact on heifer development.

Purpose of the Study:

• To characterize the variability in Holstein heifer BW across commercial farms.
• To investigate the relationship between heifer BW variations and farm management practices.
• To develop a method for estimating heifer growth using a single measurement.

Main Methods:

• Utilized heart girth circumference to estimate BW in 576 Holstein heifers aged 48–70 weeks across 33 farms in British Columbia.
• Employed regression analysis to establish a linear relationship between BW and age (BW (kg) = 116 + 5 × age (weeks)).
• Calculated farm-specific average residuals from the regression to identify deviations in heifer BW relative to age-predicted values.

Main Results:

• A significant linear correlation was observed between heifer BW and age.
• Farm average residuals for BW ranged from -54 kg to 72 kg, indicating substantial inter-farm variability.
• Heifers on farms with higher residual BW also exhibited higher rates of gain during the pre-weaning period.

Conclusions:

• Management practices influencing pre-weaned calf growth rates have a direct and significant impact on replacement heifer BW at breeding age.
• Effective management of milk-fed calves is a crucial factor in optimizing overall replacement heifer development and productivity.
• Heart girth circumference offers a practical method for estimating heifer BW and assessing growth performance on commercial farms.