THE EFFECT OF LIGHT INTENSITY DURING BROODING ON THE PRODUCTIVITY AND HEALTH OF PARACOX-5 VACCINATED BROILERS

Luciano Gobbi and Raffaele Pezzotti
Schering-Plough Animal Health, Milan, Italy.

luciano.gobbi@spcorp.com

Producers often try to increase bird activity during brooding to stimulate water and feed intake, increase growth, reduce early mortality, and improve subsequent flock uniformity.
Some experimental studies show that in young chickens, high intensity light (>70 lux sqm.) significantly increases activity as compared to low lux regimens (<20 lux sqm). To further assess the effects of lighting, a trial was performed in Paracox-5 vaccinated chickens.
Broiler chicks (Ross 508, 20,000 males and 20,000 females) were placed in one of two experimental houses. From placement until 4 days of age, both houses received 23 light hours and 1 dark hour. Lighting in one house was 75 lux and, in the other, 20 lux. After 4 days of age and until slaughter, light intensity for both groups was maintained at 20 lux.
Birds were evaluated at 0, 4, and 7 days of life, and then weekly, until 49 days of life. Statistical analysis was conducted as a one-way ANOVA and, when significant, (p<0.05) means were compared by Duncan’s Multiple Range Test.
Crop palpation to evaluate food and water intake showed that 8 hours after most birds were placed, 98.5% of those on 75 lux were filled compared to 83.0% on 20 lux. Early growth rate, liveability and flock uniformity were increased by higher light intensity, while overall mortality and the incidence of intestine bacterial overgrowth were significantly reduced. There were fewer deaths due to necrotic enteritis in the 75 lux group during the first 4 days of life. Both groups demonstrated standard oocyst shedding, but peaked on day 19 in the 75 lux group as compared to day 27 in the 20 lux group. No coccidiosis outbreaks occurred in either group.
This study provides compelling evidence that high intensity light regimens enhance activity in chicks, which in turn increases feed intake and early growth. Early complete feed consumption appears to enhance endogenous trypsin release, protein digestion, and vaccinal oocyst excystation, which may explain their earlier multiplication and peak shedding. Light manipulation during brooding also appears to minimize factors such as litter eating and dehydration that predispose to intestinal bacteria overgrowth, possibly necrotic enteritis and mortality. These results should be confirmed in additional trials before advising producers to manipulate light intensity.