A modern, but robust dairy cow is something producers are increasingly requiring and according to a study carried out at SAC, assessing fertility with milk progesterone profiling could help identify such cows.

Milk samples were collected three times a week from newly-calved cows on SAC’s Crichton Royal Estate for the first four months of lactation.

The herd comprises 200 cows in two genetic lines – a selection line bred for high milk solids and an unselected control line – managed on either a high concentrate or high forge-based systems, explained Geoff Pollott.

Milk samples were analysed and progesterone levels recorded with routine observations of heats, services and pregnancy diagnoses also taken.

Results showed selection for high milk yields and high concentrate feed input both affected cow fertility.

“These groups had lower fertility in early lactation compared with non-selected cows and those on the high forage system.”

However, oestrus cycle characteristics were not affected by genetic group, but varied by feeding system, he added.

“Use of progesterone profiling in these instances allows a more accurate picture of cow fertility rather than farm measurements alone.”

A further study into relationship of body energy traits and functional traits in dairy cows showed differences between how some sires’ daughters grow and use body energy in their first lactation.

This could indicate how animals use body reserves to maintain lactation, added SAC’s Eileen Wall.

“Early lactation growth in heifers showed a negative correlation with production, consequently slowing growth rate and reducing levels of production.”

Animals with higher energy content had shorter calving intervals, she added.

chrissie.lawrence@rbi.co.uk