Factors associated with colostrum quality and passive transfer status of dairy heifer calves on U.S. dairy operations

Abstract Text:

Passive transfer of immunity is essential for the short- and long-term health of dairy calves. The objective of this study was to evaluate colostrum quality and passive transfer status of U.S. dairy heifer calves. This study was conducted as part of the calf component of the National Animal Health Monitoring System’s Dairy 2014 study, which included 104 dairy operations in 13 states. This longitudinal study focused on dairy heifer calves from birth to weaning and was conducted over an 18-mo period. Data analysis included 1,972 Holstein calves. The mean colostrum IgG was 74.4 g/L (SE 0.72), with 77.4% of samples having colostrum IgG levels above 50 g/L. The mean serum IgG was 21.6 g/L (SE 0.25), and 73.3% of calves had serum IgG levels above 15 g/L. Backward elimination model selection in Proc Mixed of SAS® was used to determine which factors were most important (P<0.05) for determining colostrum IgG levels. The final model for colostrum IgG included the source of the colostrum (P<0.001) and the temperature and humidity index (THI) for the month prior to calving (P<0.001). Colostrum IgG was highest for third or higher lactation dams (84.2 g/L) and lowest for commercial colostrum replacers (39.5 g/L). For every 10-unit increase in THI, the colostrum IgG increased 1.4 g/L. Factors most important for predicting serum IgG levels were also evaluated using a backward elimination model selection in Proc Mixed after univariate screening (P<0.2). The final model for serum IgG included source of the colostrum (P<0.001), timing to the first feeding (P<0.001), total amount of colostrum fed in 24 h (P=0.010), the age of the calf at blood sampling (P<0.001), colostrum IgG (P<0.001), and THI for birth month (P=0.026). Serum IgG was highest for calves from first lactation dams (23.4 g/L) and lowest for commercial colostrum replacer (14.5 g/L). For every hour following birth that colostrum was administered, serum IgG decreased 0.37 g/L. For every 1 L of colostrum administered in the first 24 h after birth, the serum IgG increased 0.56 g/L. For every 10 g/L increase in colostrum IgG, serum IgG increased 1.1 g/L. For every 10-unit increase in birth month THI, the serum IgG increased 0.32 g/L. These results indicate that prompt feeding of high-quality colostrum in appropriate amounts following birth and THI are crucial to the passive transfer status of dairy calves.

Keywords:

dairy heifer calves; colostrum quality; passive transfer