Effect of strain of Holstein–Friesian and feed system on calving performance, blood parameters and overall survival

The objective of the present study was to quantify the effect of strain of Holstein–Friesian and pasture-based feeding system on calving performance, blood parameters and overall survival within a seasonal calving milk production system. The three strains of Holstein–Friesian compared were high production North American (HP), selected entirely for milk production, high durability North American (HD), selected based on milk production, fertility and muscularity traits, and New Zealand (NZ) selected from a seasonal calving pasture-based system. The three feed systems compared were a high grass allowance feed system typical of spring calving herds in Ireland (MP; control); an increased stocking rate system (HS) and an increased concentrate supplementation system (HC). Data comprised up to 585 lactations on 240 cows. Data were analysed using linear mixed models, generalised estimating equations and survival analysis. Strain of Holstein–Friesian had no significant effect on calving difficulty or rate of stillbirths while the effect of feed system on calving difficulty and rate of stillbirths approached significance. Strain of Holstein–Friesian had no significant effect on plasma metabolite or hormone concentrations around parturition, with the exception of urea concentration. At the beginning of the breeding season the NZ strain had lower plasma concentrations of NEFA (0.20 mmol/l) and higher IGF-I (86.8 ng/ml) than the HD (0.24 mmol/l and 66.9 ng/ml, respectively) and HP (0.26 mmol/l and 64.0 ng/ml, respectively) strains. The higher IGF-I concentration of the NZ strain was maintained during the breeding season. The NZ and HD strains survived longer than the HP strain with median survival days post-first calving of 1372, 1367 and 1033 respectively, while feed system had no significant effect on overall survival rate over the study period.