PHOTOPERIOD MANIPULATION DURING THE DRY PERIOD: EFFECTS ON GENERAL HEALTH AND MASTITIS OCCURRENCE

摘要

Photoperiod has a practical use on the dairy farm as its manipulation can increase milk production in dairy cows. When cows are subjected to long day photoperiod (16 h light: 8 h dark; LDPP) during their lactation, they have a 2 to 3 kg/day increase in milk yield compared to their cohorts on a natural photoperiod. This increase is substantial and cost-effective. Recent studies have also shown that a short day photoperiod (8 h light: 16 h dark; SDPP) during the dry period increases milk production ofmultiparous dairy cows in their subsequent lactation (1). Interestingly, photoperiod research in other species, rodents in particular, has shown that short day photoperiod treatment has the potential to enhance function of immune cells compared to long day photoperiod treatment (2). In addition, the periparturient period is generally recognized as a time when immune defense systems are at the lowest in dairy cattle (3). Therefore, the possibility that photoperiod, a non-invasive management tool, may beused to enhance the immune system, needs to be investigated. The objective of this study was to determine the effect of photoperiod manipulation on general health and mastitis susceptibility during the dry period and around the time of calving.