Adsa Logo White Adsa Title White

Manipulating the circadian rhythms through controlled light-dark phases in the prepartum period on cow performance in the next lactation.

A. Rauton

Abstract:

5
Manipulating the circadian rhythms through controlled light-dark phases in the prepartum period on cow performance in the next lactation.
A. Rauton*, J. Bohlen. University of Georgia Athens, GA.

Circadian rhythms, derived from the Greek “circa” meaning about and “dian” meaning day, describe a cycle over a 24-h period, which dictate sleep and wake cycles in most biological organisms. Although many aspects of these rhythms are genetically determined, it has been proven that they can be manipulated by means of food availability, temperature and light. Studies involving circadian rhythms in the dairy cow began with correlations between day length and milk production but have since expanded to include the impact these rhythms have on metabolic parameters, daily activity and hormone production. Since that first development of the positive impact of 16 h of light and 8 h of dark on milk production, most studies have focused their work on impacts during lactation. However, little is known regarding the role of circadian rhythm cycles from the end of a lactation to the beginning of the next. This transition period in dairy cattle means major hormonal shifts and changes in metabolism in an effort to accommodate the energetically demanding onset of lactation. Recent studies have shown that using a phase shifted model of the standard light dark period has the ability to positively impact these changes. This stimulation pattern involves shifting the light and dark phases by 6 h periodically throughout the treatment period. This shift, combined with circadian rhythm timing and synchrony, has been shown to alter many animal processes to include attenuation of melatonin production as well as body temperature. More consistent melatonin levels throughout the transition period prompt the animal to spend more time resting as opposed to being more active while attenuation of body temperature decreases the amount of energy used for heating and cooling throughout the day. Ultimately these culminate in a decrease in energy spent in the time before calving which results in an improvement in milk yield and fat content during the next lactation. These results indicate that by interrupting a cow's naturally occurring rhythm during the transition period, a producer may be able to alter that cow's performance in her next lactation. These novel insights into the manipulation of circadian rhythms during the transition period offer a new and innovative way to care for lactating cows before the start of lactation.

Keywords: circadian rhythm, transition, lactation performance.