Development of long bones in broilers subjected to feed restriction and created in different environmental temperature conditions

The intensive production and the large body mass of broilers makes these animals subjected to different diseases and serious changes in the bone tissue. The aim of this study is evaluate the effect of feed restriction and different ambient temperatures on the development of long bones in broilers. In the experiment, 360 male Cobb broilers were distributed in a completely randomised, 3 x 3 factorial design: three feeding programs (ad libitum - control -, 40% feed restricted and 70% feed restricted) and three environmental temperatures (hot, thermoneutral and cold). The feed restriction was made during the second week of development (8^th to 14^th day), followed by refeeding ad libitum until 42^nd day of age. Measurements of weight, length and diameter of leg bones (femur, tibia and humerus) were taken at 14, 28 and 42 days. With Masson Trichrome technique (Junqueira and Carneiro, 1999), we separate the distal region of long bones in 3 regions: cartilaginous epiphysis (CE), growth plate (GP) and metaphysis (MP). Hot temperature decreased the weight of 3 long bones (P<0.01) and diameter of tibia and humerus (P<0.01) in comparison to cold environment at 42 days. At 28 days, broilers created in high temperatures present lower CE (femur; P<0.05), GP (femur and humerus; P<0.01) and MP (tibia; P<0.05). At 42 days, MP of 3 bones decreased (P<0.05) with high temperatures. Regarding feed restriction effects, were verified decrease in length, weight and diameter of femur, tibia and humerus at 14 days (P<0.05). In relation to cartilage regions, were verified decrease in CE, GP and MP (P<0.01) of three bones evaluated at 14 days for feed restricted broilers. These effects were reverted at 42 days, since no significant difference between treatments (P>0.05) were found for variables evaluated. Therefore, we concluded that both feed restriction at environmental temperature affect the growth of long bones, but independently. The effects of feed restriction were reverted at 28 days for cartilaginous structures, and at 42 days for bones sizes, suggesting that growth of bone tissue is coordinated and dependent on cartilaginous structure recovery.