Fast-growing broiler chickens use pen-space heterogeneously and have low activity levels, related in part to leg problems. The aim of this study was to test the effects of the addition of string and sand trays to rearing pens on the use of space, levels of activity and leg problems. Broiler chickens were reared in 12 pens (40 birds per pen). Drinkers and feeders only were present in the six control pens (C group), whereas the six other pens were enriched (E group) with two sand trays and string. Behaviour was recorded by scan and focal sampling on days 2-3, 13-14, 23-24 and 34-35. Bodyweight, the occurrence of tarsal deformities and the composition of tibiotarsi were measured on day 37. Chickens from the E group spent more time and stood more often in the area enriched with sand than did the g group birds. ghickens in the E group foraged in the sand throughout the rearing period, and their foraging activities were greater than those of the C group birds. They had little interest in the strings. Locomotor activity during standing bouts was enhanced in the E group on days 2-3 only. Bodyweight at day 37, the occurrence of tarsal deformities and the composition of tibiotarsi were not significantly different between groups. These results indicate that sand could attract chickens into areas that are usually rarely used, which may reduce problems resulting from their heterogeneous distribution. However, the results also indicate the difficulty of stimulating locomotion.

The maximum efficiency requirements in poultry include management, health, nutrition and environment. However, the interaction of these factors is not always met, generating malfunctions in the metabolism, physiology and anatomy. The incidence of leg weakness in rapidly growing birds has become a major concern in the poultry sector, not only due to poor performance and condemnation in processing plants, but also to compromised animal welfare. This article aims at reviewing the main nutrition-based diseases affecting the locomotor system of broiler chickens.

Feeding broilers by alternating different diets for 1 or 2 days is known as sequential feeding, and it possibly reduces leg problems since it slows down early growth and may enhance general activity. The present study compared continuous feeding with a standard diet (C: metabolisable energy = 12.55 MJ/kg, crude protein = 190 g/kg) with alternations of a high-energy/low-protein diet (E+P−:+7% ME; −20% CP) and a low-energy/high-protein diet (E−P+: −7% ME,+20% CP) and investigated its effects on growth, behaviour and gait score in 352 male Ross broiler chickens. Sequential feeding was carried out during ten 48-h sequential-feeding cycles from 8 to 28 days of age. Three treatments were compared: complete diet (C) and two alternations of diets varying in protein and energy contents (S1: E+P− followed by E−P+; and S2: E−P+ followed by E+P−). Chickens received the same feed during the starter and finisher periods (0 to 7 and 29 to 38 days of age). Body weight (BW), feed intake, general activity and gait score, bone quality and carcass conformation were measured to evaluate leg condition and general performance. Sequential feeding significantly reduced BW at 28 days of age (S1: −9.1%; S2: −3.7%/C group; P < 0.05) and S1 were lighter than S2. In both sequential groups, time spent standing increased (C: 28%; S1:33%; S2: 35%; P < 0.05) and leg abnormalities decreased (mean gait score: C: 2.61; S1: 2.45; S2: 2.38; P < 0.02). This improvement was not related to changes in bone quality. BW at slaughter was impaired in Group S1 only, and the feed conversion ratio throughout the rearing period was not significantly impaired by sequential feeding. However, abdominal fat was higher in the S2 group. Sequential feeding using diets varying in energy and crude protein can be a useful method of reducing leg problems in broilers since it improves gait score without impairing growth performance when used as early as 8 days of age and up to not less than 8 days before slaughter in order to compensate for reduced growth. This improvement can be explained by reduced early growth and enhanced motor activity. However, it appears that the low-energy diet should be given first in order to avoid a reduction in BW at slaughter.

Selection for fast early growth rate and feeding and management procedures which support growth have lead to various welfare problems in modern broiler strains. Problems which are directly linked to growth rate are metabolic disorders causing mortality by the Sudden Death Syndrome and ascites. Fast growth rate is generally accompanied by decreased locomotor activity and extended time spent sitting or lying. The lack of exercise is considered a main cause of leg weakness, and extreme durations of sitting on poor quality litter produces skin lesions at the breast and the legs. Management factors which slow down early growth alleviate many welfare problems. Alternatively it may be considered to use slow growing strains which do not have the above mentioned welfare problems. Since growth is a main economical factor, there are problems of acceptability of these measures in the commercial broiler production. Stocking density is a central issue of broiler welfare. It is evident, that the influence of stocking density on growth rate and leg problems acts through its influence on litter and air quality. High moisture content of the litter enhances microbial activity, which in turn leads to increase of temperature and ammonia in broiler houses, and thus, high incidence of contact dermatitis. High stocking density impedes heat transfer from the litter surface to the ventilated room. This restricts the efficacy of conventional ventilation systems in alleviating heat stress. Lighting programmes with reduced photoperiods are considered essential for the stimulation of locomotor activity and the development of a circadian rhythm in the birds. Extended dark periods, however, reduce growth when applied in the first weeks of age. Compensation occurs when the time of the production cycle is substantially increased. Various methods to enrich the environment have shown only moderate effects on the behaviour and physical conditions of broilers.