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=...