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Marco Winters Head of genetics, DairyCo
he importance of genetics in dairy cow performance is undeniable and has been well accepted for production and conformation traits for some time. But over the last decade its contribution to fitness and fertility has also been recognised, resulting in these indices now being firmly embedded into the breeding decisions of all major AI companies and dairy producers alike.
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The UK Fertility Index (FI) is calculated from six pieces of information (see box opposite), and from this analysis combines the Predicted Transmitting Abilities (PTAs) for Calving Interval and Non-Return Rate into a single FI. This means that selection on FI improves both conception rate and calving interval at the same time. The relationship between the FI and
Since the introduction of the Fertility Index in 2005, significant genetic progress has been made and the reward is being seen in the performance of the national dairy herd today, as Marco Winters, head of genetics for AHDB Dairy, reports.
its subcomponents is depicted in graph 1. Graph 1 shows that on average each point FI improves the daughter calving interval by -0.6 days and simultaneously improves Non-Return Rate at 56 days (NR56) by 0.25% per generation. Therefore, a +10 FI bull compared to a -10 FI bull has a substantial advantage of a 12 day shorter calving interval and 5% higher conception rates in one generation. Remember that as with all genetic improvement, these gains are permanent and cumulative over subsequent generations. What’s more, these benefits of improved fertility can be made without the need to compromise significantly on any of the important traits of interest. Taking PTA Milk kg and the daughter FI as two extreme examples, we can
see from graph 2 how the Holstein breeding industry has successfully managed to select for improvements in both production and fertility since 2007.
The graph illustrates two important points: 1. Daughter fertility
deteriorated at the time when the major selection focus was on production (period 1990 to 2000). When selection for milk yield slowed down, the genetics of fertility similarly stopped deteriorating at the same rate. Remember at this time, no information on daughter fertility was available to select on, and both traits have a strong negative genetic association which caused the decline. 2. With the introduction of the UK Fertility Index in 2005 and its significant contribution as part of the revised Profitable Lifetime index (£PLI) in 2007, the automatic link between production and fertility was firmly broken and breeders were able to select for bulls that improved both daughter fertility and production at the same time.
Graph 1: Relationship between the Fertility Index (x-axis) and its two sub-components; Calving Interval and Non-Return Rate (source AHDB Dairy – Aug15 genetic evaluations)
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