Genetic parameters for pre-calving feed intake

Abstract Text: The objective of this study was to estimate genetic parameters for dry matter intake (DMI) measured during lactation and the dry period in Holstein cows. Daily individual feed intake data collection started approximately 30 days before the expected calving date, and continued through the first half of lactation. Pre-calving DMI traits were defined as average DMI on d -17 through -15 (cows) or d -10 through -8 (heifers) relative to parturition (DRYDMI), average DMI for d -1 through -3 relative to parturition (CALVEDMI), and the slope of the regression line fit through the last 14 (cows) or 7 (heifers) days prior to parturition (DECLINE). These traits were compared to DMI during lactation, defined as average DMI for 100 through 102 days in milk (LACDMI).  The final data set included 242 and 214 primiparous and multiparous cows, respectively. Genetic parameters were estimated by mixed model analyses using a 5-generation pedigree.  Fixed effects included lactation, year by season of calving, age at calving, sex of calf (male, female or twin), and  status of calf (live or dead). Heritability estimates were 0.37, 0.60, 0.28, and 0.41 for DRYDMI, CALVEDMI, DECLINE, and LACDMI, respectively. Genetic correlations between all traits except DECLINE and LACDMI were significantly greater than zero. The correlation between DRYDMI and DECLINE was 0.37, but all other correlations were greater than 0.70.  In particular, the genetic correlation between DRYDMI and LACDMI was 0.93. Results from this study demonstrate that DMI measured during the dry period or lactation is a moderately heritable trait. The high genetic correlation between DRYDMI and LACDMI was unexpected because DMI during lactation is also highly influenced by milk production. However, results of this study suggest the genetic regulation of DMI during the dry period and lactation is very similar. This result has potential implications to the measurement of feed intake for the purpose of calculating feed efficiency because in some situations, measurement of feed intake during the dry period is more feasible than measurement during lactation. However, this study is based on a relatively small number of cows and would benefit from verification in a larger population.

Keywords: Holstein cow, heritability, pre-calving intake