Effects of weekly regrouping of prepartum dairy cows on metabolic, health, reproductive, and productive parameters

The objectives of the current experiment were to determine the effect of 2 prepartum grouping strategies on the health, metabolic, reproductive, and productive parameters of dairy cows. Jersey cows enrolled in the experiment at 253 ± 3 d of gestation (d 0 = calving) were balanced for parity and projected 305-d mature equivalent and assigned to 1 of 2 treatments. Cows assigned to the traditional (TRD; n = 6 replicates with a total of 308 cows) treatment were moved to the study pen as a group of 44 cows and weekly thereafter groups of 2 to 15 cows were moved to the study pen to reestablish stocking density. Cows assigned to the all-in-all-out (AIAO; n = 6 replicates with a total of 259 cows) treatment were moved to the study pen in groups of 44 cows, but no new cows entered the AIAO pen until the end of the replicate. At the end of each replicate, a new TRD and AIAO group started but pens were switched. Cows were milked thrice daily and monthly milk yield, fat and protein contents, and somatic cell count data were recorded up to 305 d postpartum. Plasma nonesterified fatty acid concentration was measured weekly from d −18 ± 3 to 24 ± 3 and plasma β-hydroxybutyrate was measured weekly from d 3 ± 3 to 24 ± 3. Cows were examined on d 1, 4 ± 1, 7 ± 1, 10 ± 1, and 13 ± 1 for diagnosis of uterine diseases and had their ovaries scanned by ultrasound on d 39 ± 3 and 53 ± 3 to determine resumption of ovarian cycles. Average stocking density was reduced for the AIAO (71.9%) treatment compared with the TRD (86.9%) treatment. Treatment did not affect the incidences of retained fetal membranes (TRD = 10.9, AIAO = 11.6%), metritis (TRD = 16.7, AIAO = 19.8%), and acute metritis (TRD = 1.7, AIAO = 3.6%). Concentrations of nonesterified fatty acids (TRD = 80.4 ± 8.2, AIAO = 62.9 ± 8.5 µmol/L) and β-hydroxybutyrate (TRD = 454.4 ± 10.9, AIAO = 446.1 ± 11.1 µmol/L) were not different between treatments. Percentages of cows that resumed ovarian cycles by d 39 ± 3 (TRD = 70.8, AIAO = 63.1%) and 53 ± 3 (TRD = 90.1, AIAO = 90.2%) were not different between treatments. Similarly, treatment had no effect on rate of removal from the herd {TRD = referent, AIAO [(adjusted hazard ratio (95% confidence interval)] = 0.85 (0.63, 1.15)} or rate of pregnancy [TRD = referent, AIAO = 1.07 (0.88, 1.30)]. Finally, treatment did not affect energy-corrected milk yield (TRD = 34.4 ± 0.6, AIAO = 34.3 ± 0.7 kg/d). In conditions of adequate feed bunk space, the AIAO treatment did not improve health, metabolic, reproductive, or productive parameters compared with the TRD treatment.