Reduced access to resources because of increased stocking density may have a detrimental effect on the behavior of the lactating dairy cow. The objective of this study was to determine the short-term responses in behavior, productivity, fecal cortisol metabolites, and udder and leg hygiene of lactating Holstein dairy cows housed at stocking densities of 100 (1 cow per freestall and headlock), 113, 131, and 142%. Multiparous cows (n=92) and primiparous cows (n=44) were assigned to 1 of 4 pens (34 cows per pen) in a 4-row freestall barn. Pens were balanced for parity, milk production, and days in milk. Stocking densities were imposed for 14 d using a 4 × 4 Latin square design. Time spent feeding and time spent ruminating were quantified by 24 h of direct observation of focal cows (n=12 per pen) beginning at 0800 h on d 11 of each period. Data loggers recorded lying behavior (time and bouts) from the same focal cows per pen at 1-min intervals during the final 5 d of each period. Fecal cortisol metabolites were quantified from samples collected on d 13 and 14 of each period from the same focal cows. Displacements from the feed barrier were recorded on a pen basis after 9 milkings over the last 4 d of each period. Productivity was assessed on a pen basis from milk yield (recorded from d 10 to 14 of each period) and milk components (quantified from composite samples collected on d 12 of each period). Milk composition was further analyzed for milk fatty acid profiles, which were determined from a subset (n=6 per pen) of the focal cows. Data were analyzed using the MIXED procedure of SAS, with the pen (n=4 per treatment, except displacements where n=3 per treatment) as the experimental unit. Feeding and ruminating (h/d) did not differ among treatments. Lying time was reduced at stocking densities of 131 and 142%, relative to 100 or 113%. Lying bouts were not affected by treatment. Stocking densities of 131 and 142% reduced the percentage of time cows spent ruminating within a freestall relative to 100%. Displacements from the feed bunk increased linearly across treatments. Fecal cortisol metabolites, udder hygiene score, milk yields, milk composition, and milk fatty acids did not differ among treatments. Decreased lying time and increased aggression at the feed bunk suggest that an alteration of the time budgets of lactating dairy cows may occur at higher stocking densities, but it is unclear at what point these changes might have further biological consequences.

The primary objective of this study was to evaluate short-term responses in lying behavior and hygiene of Holstein dairy cows housed at a stocking density of 100 (1 cow per stall and headlock) or 142% imposed by 1) the denial of access to freestalls and headlocks, 2) the denial of access to freestalls, headlocks, and 26.6 m(2) of alley space, or 3) the addition of a rotating group of 14 cows to the resident group of 34 cows. The secondary objective was to determine the bioequivalence of the 3 methods of experimentally increasing stocking density. Cows (n=136) were assigned to 1 of 4 pens in a 4-row freestall barn and treatments were allocated using a 4×4 Latin square with 14-d periods. Lying time (h/d) and number of bouts/d for 12 focal cows per pen were determined using dataloggers recording at 1-min intervals during the final 5 d of each period. Dry matter intake (DMI) was established from the pen mean over the final 4 d of each period. Feeding and rumination activities on focal cows were determined by direct observation at 10-min intervals for 24h on d 11. Hygiene of focal cows was assessed from the difference in the scores after the legs and udder were cleaned on d 2 of each period and those on d 14. Lying time was greater for 100% stocking density (13.0 h/d) than the 142% stocking density treatments (11.8 h/d), which did not differ. Lying bouts (12.3/d) and bout duration (64.8 min/bout) did not differ among treatments. Short-term responses in DMI (24.6 kg/d) did not differ in response to the treatments. The 3 stocking density treatments decreased, or tended to decrease, the time spent feeding compared with 100% (4.4 versus 4.2 h/d). The stocking density treatments decreased the percentage of rumination occurring within a stall (92.3 versus 85.3%). A treatment effect on udder and leg hygiene scores was not evident on d 14 of each period or in the change from d 2 to 14 of each period. With the exception of rumination time (h/d), the 3 methods for experimentally imposing stocking density were bioequivalent for responses in behaviors, DMI, and hygiene. Future stocking density experiments in 4-row barns should simply deny resting and feeding space to simulate overcrowded housing conditions for lactating dairy cows because it is bioequivalent to more complicated, and potentially confounding, research models.