PSV-A-8 Reduced Daylength pre-Calving Increases Milk Production Post-Calving

Abstract Exposing Holstein dry cows to short-day (SD) photoperiod of 8 hours per day can improve milk production post-calving by 3.2 kg day, compared exposed long-day (LD) 16 during the same period. To date, no studies have evaluated effect altered period on in Jersey cows. Our objective was study LD and SD both breeds. (n=33) dried off 60 days prior their due date were either (n=9 Holstein, n=8 Jersey) or (n=8 at 18.3 °C until calving. After calving, returned ambient data collected for 15 weeks. Lactation number, replicate, feed intake treatment recorded. Data analyzed using PROC MIXED SAS 9.4. Overall average differed breed (P< 0.01), with Holsteins producing more (72.9 ± 6.2 kgs) than Jerseys (66.1 7.3 kgs). Treatment (P=0.02) (71.0 6.9 (68.1 6.7 interaction significantly differed. Long-day produced 73.9 kgs which not different (P >0.10) from (72.1 6.4 Neither nor (P=0.16, P=0.60) 70.0 7.4 kgs. averaged least 62.3 all other groups 0.01). This suggests Jerseys’ responds similarly previous reported data. Factors causing unexpected could be elevated temperature-humidity index values post-calving, despite industry standard heat abatement.