Effects of density on perching behavior of broiler chickens

Exercise through perching has been suggested as a way to reduce the impact of leg problems in broiler chickens. It is possible that higher stocking densities may motivate birds to perch more, and perhaps reduce some of the detrimental effects to broiler health seen with high stocking densities. The goal of this research was to investigate the effects of density (10, 15, and 20 birds/m(2)) and perch design on the frequency of perch utilization. Mixed sex broilers were assigned to 36 pens in a four perch treatment x three density factorial with three replications for each treatment/density combination in a randomized complete block design. Pens were assigned to one of four perch treatments: control (no perches), horizontal (three horizontal perches), angled (three 10 degrees angled perches), or mixed angle (one horizontal, one 10 degrees angled, and one 20 degrees angled perch), at each of the three densities. The results show that although the frequency of perch use was low, (2.6% +/- 0.15), significant preferences were clear. Perching frequency was significantly higher when birds were raised at stocking densities of 15 (2.88 +/- 0.303) or 20 birds/m(2) (2.76 +/- 0.211), as opposed to 10 birds/m(2) (2.10 +/- 0.209) as indicated by a marginally significant main effect (p < 0.0597), and a significant linear effect (P < 0.0427). The birds used the horizontal perches the most, followed by 10 degrees angled and mixed angle perch treatments with decreasing frequency. An effect of age was found, in that perching increased during the first 3 weeks, and dropped off significantly at the end of the rearing period for all perch treatments. In general, perches closest to the hallway or outside of the house were used more than perches in the middle of the pen. Preferential use of the highest section of the 10 degrees angled perches was also found. The applied perch treatments or densities did not significantly affect final body weight or feed conversion. Percent mortality due to heat stress showed a significant increase with density, while mortality not caused by heat stress did not change with perch treatment or density. (C) 2001 Elsevier Science B.V. All rights reserved.