4 April 2011

2 minute read

This is just one of the interesting findings of a study, carried out by researchers in Northern Ireland, the results of which were presented to delegates at this year’s British Society of Animal Science’s annual conference, held at Queen’s University, Belfast.

The integration of dairy heifers into the main herd during the post calving period can have negative effects on the heifer’s welfare and productivity and this appears to be related to the fact that heifers attain low social status when entering the milking herd and therefore are subjected to increased levels of bullying and aggression.

The aim of this study was to assess if the time of day, in other words after morning or afternoon milking, when freshly-calved heifers are introduced to a group containing mature cows influences the heifers’ welfare and performance,” said the Agri-Food and Biosciences Institute’s Alastair Boyle, explaining the rationale behind his team’s work. A total of 28 Holstein Friesian heifers were used in the study, with heifers introduced into a group containing mature cows between approximately 24 and 36 hours post calving.

Animals were housed in cubicle pens with solid floors. Two treatments were examined, with heifers introduced either after morning milking or after evening milking.

Treatments were replicated five times, with treatments balanced for genetic merit, body weight, condition score and sire. In each replicate a resident group, containing 12 cows and six non-experimental heifers, was established at least seven days prior to the introduction of the first experimental heifer.

The social and exploratory behaviour of each heifer was recorded directly during a two-hour period immediately after introduction to the group on day one. These behaviours were observed for each experimental heifer during four five-minute continuous observations at 30-minute intervals during the two-hour post-feeding period on one day each week for one month post introduction.

“And we saw that on the first day animals in the ‘morning’ treatment received more threats and butts than those in the ‘afternoon’ treatment,” said Mr Boyle.

“There was a tendency for heifers introduced at in the morning to be chased more than those introduced in the afternoon and heifers introduced to the group in the afternoon were more socially cohesive than those in the morning treatment.

“No significant treatment effect was found for total hours lying, with heifers in both treatments lying for an averaged 7.5 hours/day. During the first day heifers in both treatments lay for fewer than 4 hours/day,” he added.