Cows are often moved between groups in accordance with their management needs. During each move, the cow needs to re-establish her rank within the groups pecking order. The cows’ rank is associated with their age, body size and seniority of the cow i.e. a heifer in her first lactation will be of low rank.
Group changes cause social turmoil, which is a large stress factor for the cow for around 48 hours and causing a reduction in dry matter intake (DMI). With feed intake impacting milk yield, body condition, cow health and overall herd performance, it is important to minimize this stress factor to ensure maximum intakes. A study conducted at The University of British Columbia looked at the impact of group changes on feeding behaviour and rumen health. Their data revealed that during the 48 hours after a regrouping, feed bunk aggression increases and DMI and rumination decrease by 10%.
The reduced DMI attributed to group changes also negatively effects milk yield, thanks to nutritional and social stresses. As early as 1978 researchers have demonstrated that milk production decrease between 2.5-5% when social disturbances occurred. Early lactation cows are more affected by group changes than those in mid lactation, as they experience a larger decrease in DMI and milk production. If a cow’s milk yield drops before she reaches her peak yield, she will recover, but to below her intended peak lactation level. Whilst post peak cows will still drop in milk yield, they are likely to be less effected due to these cows gaining weight and, therefore, more likely to gain a higher rank in the herd.
During the transition period, social turmoil can cause great issues. While this may only account for a short time in the cows’ cycle, this is when the cow is most likely to have the greatest number of group changes. When a cow is added to a stable social group, the entire group is disrupted, with social turmoil occurring until she finds her rank. Figure 1 demonstrates the level of social turmoil that occurs when cows enter the group. Daily group entries will cause continual turmoil, whereas weekly entries reduce turmoil to approximately two days before return to stability.
The cow is already at her most vulnerable during transition, with 50% of metabolic and infectious diseases occurring during this period. At this time, her DMI is at its lowest point – potentially dropping 30% in the last 10 days. A lowered DMI can contribute to increased disease susceptibility, with cows who eat less during transition more likely to suffer from subclinical or clinical metritis (Huzzey et al., 2007). The avoidance of stress, to prevent lowering her DMI further is critical in order prevent production loss during her subsequent lactation.
Figure 1: Social turmoil of new entries. (University of Wisconsin)
To limit the effects of social turmoil on DMI, ensure there is adequate feed space available to the cows - 3ft for transition cows and 2-2 ½ ft for milking cows. This will help to avoid reductions in DMI for the subordinate cows and heifers, by enabling all cows to eat at the same time. Once a transition group has been established, limit the number of new entries into the group and avoid cow movement between 17 - 2 days pre-calving, when DMI is already low. You can also reduce the number of aggressive encounters following a move by housing cows adjacent to one another, limiting proximity and physical contact (Albright & Arave 1997). Social disruption can also be minimised through moving cows in small groups, rather than individually (Albright, 1978).
Whilst each pen move will incur stress, not all moves cause the same level of stress. Remember, cows in transition, early lactation and low-ranking cows are the most susceptible.
References
Konggard SP, Krohn CC. Performance of first-calf heifers in two different grouping systems. Rep Nat Inst Anim Sci. Copenhagen, Denmark. 1978
Albright, J. L. 1978. Social considerations in grouping cows. Pages 757-779 in Large Dairy Herd Management. C. J. Wilcox and H. H. Van Horn, ed. University Press of Florida, Gainesville
Huzzey, J. M., D. M. Veira, D. M. Weary, and M. A. G. von Keyserlingk. 2007. Prepartum behaviour and dry matter intake identify dairy cows at risk for metritis. J. Dairy Sci. 90:3220–3233
Albright, J. L., and C. W. Arave. 1997. Feeding behaviour. Page 106 in The Behaviour of cattle. CAB Int., Wallingford, Oxon, UK
Rachel Gardner
Dairy Specialist (Trainee)
