Effects of ambient temperature and early open-field response on the behaviour, feed intake and growth of fast- and slow-growing broiler strains

Abstract

Increased activity improves broiler leg health, but also increases the heat production of the bird. This experiment investigated the effects of early open-field activity and ambient temperature on the growth and feed intake of two strains of broiler chickens. On the basis of the level of activity in an open-field test on day 3 after hatching, fast-growing Ross 208 and slow-growing i657 chickens were allocated on day 13 to one of the 48 groups. Each group included either six active or six passive birds from each strain and the groups were housed in floor-pens littered with wood chips and fitted with two heat lamps. Each group was fed ad libitum and subjected to one of the three temperature treatments: two (HH; 268C), one (HC; 168C to 268C) or no (CC; 168C) heat lamps turned on. Production and behavioural data were collected every 2 weeks until day 57. For both strains, early open-field activity had no significant effects on their subsequent behaviour or on any of the production parameters measured, and overall, the slow-growing strain was more active than the fast-growing strain. Ambient temperature had significant effects on production measures for i657 broilers, with CC chickens eating and weighing more, and with a less efficient feed conversion than HH chickens, with HC birds intermediate. A similar effect was found for Ross 208 only for feed intake from 27 to 41 days of age. Ross 208 chickens distributed themselves in the pen with a preference for cooler areas in the hottest ambient temperature treatments. In contrast, the behaviour of the slow-growing strain appeared to be relatively unaffected by the ambient temperature. In conclusion, fast-growing broilers use behavioural changes when trying to adapt to warm environments, whereas slow-growing broilers use metabolic changes to adapt to cooler ambient temperatures.

Neuronal tracing of oral nerves in a velvet worm—Implications for the evolution of the ecdysozoan brain

“…Hence, the last common ancestor of Panarthropoda most likely possessed a bilaterally symmetric, dorsal, ganglionic brain rather than a circumoral/circumpharyngeal, collar-shaped brain, which is a characteristic feature of cycloneuralians, including priapulids, loriciferans, kinorhynchs, nematodes and nematomorphs (Bullock and Horridge, 1965; Nielsen, 2012). Since we did not find any indication of such a circumoral ring in Onychophora, and since this feature does not occur in any other animal group, our findings support the hypothesis that the circumoral, collar-shaped brain is a synapomorphy of the cycloneuralian taxa (Ahlrichs, 1995; Nielsen, 2012). Thus, the last common ancestor of Ecdysozoa (Figure 1) most likely possessed a panarthropod-like, paired, ganglionic brain, which was modified in the cycloneuralian lineage.…”

“…Representatives of priapulids, kinorhynchs, nematodes and allies possess a circumoral, collar-shaped brain, with anterior and posterior rings of perikarya separated by a ring-like neuropil, hence the name Cycloneuralia for the clade including these taxa (Bullock and Horridge, 1965; Ahlrichs, 1995; Nielsen, 2012). In contrast, members of the second major clade of Ecdysozoa, the Panarthropoda (Onychophora + Tardigrada + Arthropoda), exhibit a typical ganglionic, bilaterally symmetric brain situated dorsally within the head (e.g., Homberg, 1991; Strausfeld et al, 2006a; Mayer et al, 2010, 2013a,b).…”

“…Trichotomies indicate unresolved relationships. Phylogenetic relationships combined after Mayer and Whitington (2009b) and Nielsen (2012). Abbreviations: C, Cycloneuralia; E, Ecdysozoa; N, Nematoida; P, Panarthropoda; S, Scalidophora.…”

Performance of chicks subjected to thermal challenge

“…Nielsen (2012) stated that heat dissipation has an important effect on bird WI and growth. Under warm/ hot environments, the WI by birds is greater because it is essential to the cooling mechanisms (increased latent heat loss) involved in thermoregulation (Cordeiro et al, 2010).…”

Possible improvement of measures within the principle ‘appropriate behaviour’ of the Welfare Quality® boiler assessment protocol

“…Thus, the touch test should either be validated, which has not yet been done for broiler chickens, replaced by another measure of fearfulness, or, alternative variables related to fearfulness and unaffected by walking ability should be identified. Furthermore, the expression of fear can differ between genetic lines (Nielsen, 2012;Mignon-Grasteau et al, 2017). So, it is crucial that the results represent valid levels of overall fear for all lines.…”