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Calving Ease Proofs Rate Sires For Calving Performance

10 May 2011

Animal Bytes

Calving ease proofs will help to reduce calving difficulties and their cost, although the heritability is low.

Having calving ease proofs available will help dairy producers to identify bulls that are genetically good (or bad) for calving performance. And this may be of particular importance when choosing bulls to use – or avoid – on heifers to reduce the number of difficult calvings and cut the costs associated with losses in production, fertility and potentially cow/calf losses.

So said the SAC’s Eileen Wall, when she presented the findings of her team’s project, to develop routine national calving ease evaluations for UK dairy cattle, to delegates at the 2010 British Society of Animal Science’s annual conference, held at Queen’s University, Belfast.

The ease of calving influences the economics of a cow/calf enterprise through increased calf death loss, increased labour and vet costs, reduced subsequent reproductive performance of the cow, potential loss of the cow, and reduced milk production. It’s estimated that a slightly difficult calving costs approximately £110 and a seriously difficult calving costs between £350 and £400. “So a national calving ease evaluation would be a huge step forward for the UK dairy industry,” said Dr Wall, explaining the rationale behind her work.

The project took data from UK milk recording organisations, and included producer-recorded calving ease (CE) data, as well as data collected as part of the progeny test scheme. Genetic parameters for CE were estimated, considering a direct and indirect effect.

Fixed effects in the model include herd year, month of calving, lactation number, calf sex and interaction between lactation number and calf sex. Age and percentage Holstein were fitted as linear regressions. And a random effect of service sire was fitted to estimate direct CE predicted transmitting ability (PTA) and random effect of maternal grandsire fitted for indirect CE PTA, with a covariance between the two effects also fitted.

“The data spanned 15 years, but the majority of the data falls after 1999,” said Dr Wall. “Overall, 84 per cent of calvings were classed as ‘easy calving’. For first calving cows a total of 74 per cent calvings were classed as ‘easy’ and 85 per cent of later calvings,” she added.

The genetic analysis showed that the heritability for calving ease was low (0.066 and 0.040 for direct and indirect effects respectively with a genetic correlation of -0.685). And there was no evidence of a genetic trend in either direct or maternal CE PTAs.

The across country genetic correlations for the multiple-trait across country evaluations (MACE) run for direct and maternal CE were in line with other countries and suggest that UK CE PTAs would be suitable for an international MACE evaluation. The genetic correlations between countries for the direct calving trait averaged of 0.80 and ranged from 0.619 (with Hungary) to 0.944 (with Canada).

The genetic correlations between countries for the maternal calving trait was a little lower with an average of 0.69 and ranged from 0.561 (with Hungary) to 0.839 (with France). These correlations with other countries are good, particularly for such low heritability traits.

May 2011

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