Effects of stocking density during the dry period on dairy cow physiology, metabolism and behaviour

The effects of high stocking density during the dry period on dairy cow physiology, behaviour and welfare were investigated. Holstein Friesian cows (n=48, calving over a seven month period) were dried-off 60±4 days before their expected calving date, and allocated to either high (H) or low (L) stocking density groups. Cows were housed in cubicles from dry-off to 21 days before calving and then moved to straw yards until calving. In cubicle pens, H and L cows had 0.5 vs 1.0 feed yokes/cow and 1.0 vs 1.5 cubicles/cow, respectively, and in straw yards, 0.3m vs 0.6m linear feed-face space and 6m2 vs 12m2 lying space, respectively. Video observations of feeding behaviour during the 3 hours after feed delivery (3 days/week) and agonistic interactions at the feed-face during peak feeding (2 days/week) were made. Daily lying proportion was measured using an accelerometer device throughout the dry period. Concentrations of faecal glucocorticoid metabolites (FGCM) at dry-off, d7 and d35 after dry-off, and 21 and 7 days before calving and the change in energy metabolites (glucose, NEFA, BHB) from dry-off to 7 days before calving were measured. H cows were less likely to start feeding within 5 minutes of feed delivery and spent less time feeding compared to L cows, but they engaged in displacements more frequently and spent more time standing in the feed alley. Irrespective of the treatment groups, FGCM concentrations significantly increased from dry-off to d7 and remained higher during the dry period. Stocking density did not affect daily lying proportion, energy metabolites during the dry period and milk yield during subsequent lactation. This study found that whilst high stocking density during the dry period increased competition at the feed-face and altered feeding behaviour, it did not affect stress responses, energy metabolism or subsequent milk yield. 
Dairy cow management during the prepartum period is important, not only due to subsequent influences on postpartum performance, but also for the welfare of cows at this critical time. Cows often undergo dramatic changes in management practices during the last one or two months of gestation (i.e. dry period), including cessation of milking, changes in diet, housing systems and social environment, which can be stressful to dry cows. Dynamic social re-grouping (i.e. the regular entry of new cows and removal of cows to other groups) is a common practice for dry cows on UK dairy farms (Fujiwara et al. 2018), but frequent regrouping of prepartum cows has been shown to increase agonistic social interactions at the feed-face (Schirmann et al. 2011; Lobeck-Luchterhand et al. 2014). Talebi et al. (2014) suggested that reduced stocking density can attenuate the negative impact of regrouping, but overstocking of dairy cows may be common especially on large farms to maximise profit while reducing cost (Estevez et al. 2007).
Overstocking of dairy cows results in altered feeding behaviour, increased feed competition, and decreased lying time (e.g. Huzzey et al. 2006; Fregonesi et al. 2007; Proudfoot et al. 2009) and can induce physiological stress responses (Huzzey et al. 2012; Fustini et al. 2017). Therefore, it is important to provide adequate space for prepartum dairy cows, especially where dynamic social grouping is unavoidable.
This study aimed to investigate the effect of overstocking during the entire dry period in an industry-relevant setting. We hypothesised that, during the dry period, high stocking density would result in more frequent agonistic social interaction, altered feeding and lying behaviour, the activation of physiological stress response and negative energy balance in cows.