11 September 1998

Extend lactations to cut lifetime health concerns

By Simon Wragg

EXTENDING lactations so cows calve once every 18 months instead of every 12 could theoretically cut fertility and health concerns by a third, but Scottish trials proved otherwise.

Chris Knight, Hannah Research Institutes head of animal research, told delegates at last weeks Nottingham Cattle Fertility conference that most health and fertility problems in dairy cows occurred around calving to peak lactation.

"Where a high yielding cow has three 12-month lactations in a lifetime changing to two 18-month lactations, health concerns would be cut by one-third," said Prof Knight.

But MAFF-funded trials found extended lactation cows had poorer fertility. Each cow required 2.5 services to conceive, compared with 1.9 services a conception for cows on a 12-month lactation cycle. Conception to first service was also poorer, with only 22% of extended lactation cows conceiving, compared with 40% of the 12-month cycle cows.

"Conception rate was lower for extended lactation cows; 40% compared with 55%," said Prof Knight. "There is nothing to suggest extended lactation breeding is easier. Problems tend to be different – such as more cystic ovaries – but should be easier to solve."

No significant differences were found in extended lactation cows on spring or autumn calving patterns, and low or high production feeding regimes.

But results of the small trial should not be taken as conclusive proof that extended lactations wont work he said. Prof Knight. Evidence from the US suggests it is feasible, albeit with the aid of BST. But better reproductive management would be essential, said Prof. Knight.

CONFERENCEPOINTERS

&#8226 Beef cattle fewer concerns.

&#8226 Fertility indices?

&#8226 Extended lactation difficulties.

The Hannah Institutes Chris Knight voiced extended lactation fears.