Relationships among faecal egg counts, anti‐parasite antibodies and milk yields in an experimental Friesian herd

Abstract

Two studies were carried out to measure variation in faecal nematode egg count (FEC) or serum anti‐nematode antibody (Ab) concentration in Friesian cattle, and correlations between these traits and subsequent milk yield traits. In Study 1, FEC and Abs were measured in 9‐month‐old calves and 21‐month‐old heifers (1996 and 1995 calf crops, respectively), and correlations with the subsequent first‐lactation yield traits were estimated in herds calving in late winter (July/August). In Study 2, Abs were measured in mixed‐age cows during lactation in each of four groups (summer, autumn, winter, and spring calving mobs), and correlations were estimated between Abs and yield in the current lactation. In Study 1, concentrations of the six different Abs (adult and/or third larval stages of four nematode parasite species) were moderately correlated with each other (average correlations of 0.57 in calves and 0.65 in heifers). In Study 2 the average correlation among Abs was 0.74. In Study 1, the average FEC values were 142 and 56 eggs/g in April and June samples collected from calves, and 14 and 28 eggs/g from heifers. Repeatability of FEC over time was moderate in the calves (0.45), but much lower in the heifers (0.13). Correlations between FEC and Ab were low but favourable in sign, averaging ‐0.24 in calves and ‐0.12 in heifers, while those between FEC as a juvenile and first‐lactation milk or milk‐component yields were close to zero, averaging ‐0.05 for calves and ‐0.02 for heifers. Correlations between Abs to Cooperia oncophora or Ostertagia L3 antigens and milk or milk‐component yields averaged 0.23 and 0.07, for the two age groups in Study 1, respectively, and 0.06 in Study 2. Correlations between these Abs and liveweight averaged 0.14 for calves and 0.17 for heifers. It is concluded that, under the routine herd management conditions applied, concentrations among all Abs studied were consistently correlated, FEC was repeatable in calves, and those calves with a higher Ab response to Cooperia oncophora or Ostertagia L3 antigens tended to show slightly higher first‐lactation yields.