An economic analysis of heifer rearing and breeding selection in the uk

Dairy farming accounts for approximately 18% of UK agricultural production by value, with 1.9 million cows having an annual production of around 13.3 billion litres of milk. In order to remain profitable and competitive the UK dairy industry has undergone a period of rapid change in recent years. This has involved increasing herd sizes accompanied by modifications to dairy cow genetics and feeding systems to raise average yields. The average cow currently produces about 7000 litres of milk per annum, but only survives in the herd for 3 lactations. This short lifespan threatens national herd sustainability due to limitations in the supply of replacement heifers, reduced profitability and increased environmental footprint. The negative impact of selecting solely on production traits has been recognised by some breeding companies, but there remains a lack of information on the economics of selection and the identification of critical decision points. Furthermore, traits included in UK selection indices only relate to the dairy cow once she has entered the milking herd, so do not account for traits relating to the growth and fertility of dairy heifers which impact on their subsequent survival and performance. The two partners have recently undertaken an observational cohort study to identify the timing and major causes of wastage in the dairy herd. This obtained detailed on-farm data for cohorts of Holstein-Friesian heifers on 19 commercial dairy farms from birth until culling. Data were collected on the individual heifers (growth parameters, metabolic and endocrine status, reproductive performance and milk production), their parentage, and the farm environment. The relative importance of genetic and environmental components during the rearing period in relation to subsequent survival, growth and fertility was determined. Databases generated during this initial study provide a strong basis for examining the true costs of heifer rearing. These will be supplemented with data derived from other recently published UK sources relating to heifer mortality, fertility, milk production and longevity under different management systems. This information will be used to compare the costs of selecting between reproductive efficiency, lactation yields and longevity when developing genetic selection indices. Economic analysis will include the direct and indirect costs of heifer rearing and the farm-level and national impacts of using current genetic selection indices for lactation yield versus longevity. The latter will be examined using a cost-effectiveness framework with the application of different outcomes. The possible benefits of including heifer growth and fertility traits in selection indices will be modelled. Initially a dynamic, deterministic herd model will be developed that will take into account mortality and culling rates, age at first calving, fertility rates and lactation yields. This will be used to estimate milk output from a herd and the ability for a herd to maintain its size without the need to buy in replacements. A decision tree structure will also be developed with node points based on breeding decisions and the outcomes in terms of the traits in the individual animal. The two models will be combined as a basis for the cost-effectiveness analysis. Sensitivity analysis will be performed on the models parameters. Those parameters that influence the outcomes greatly will be made stochastic within the overall model. The project will generate: (i) accurate data on the cost of heifer replacement in different management systems taking into account the costs of animals culled prematurely; (ii) estimation of break-even lactation number to cover the costs of heifer replacement in different management systems and (iii) cost-effectiveness analysis of the best selection trait(s) for lactation yield, longevity and overall herd sustainability. Finally the implications of the findings to national dairy policy will be assessed.