Economic values for reproduction traits in beef suckler herds based on a calving distribution model

Economic values for the genetic improvement of gestation length, post partum anoestrus interval, conception rates at first or later post partum oestrus and calving day (relative to the first day of the calving season) in seasonal calving beef suckler herds were estimated. The approach used combines partial budgeting of the economic cost of a barren cow with a model of the herd calving distribution which is driven by assumed levels of reproductive parameters. Economic values for all traits were shown to be highly variable across farms and are also likely to vary across years. For an increase in gestation length and equivalently in post partum anoestrus interval, estimates of economic values ranged between -0.2 and -2.77 £/day with higher values apparent in herds with a wide calving spread. Economic values for conception rates were higher at later (0.25 to 1.28 £ per % increase) than at first (0.1 to 0.7 £ per % increase) post partum oestruses. For calving day, economic values were approximately half of those derived using an alternative method from the literature which assumes calving day to be normally distributed. Implications for establishing selection criteria to choose terminal beef sires and suckler beef cows are discussed.