Abstract
Resilient animals can cope with environmental disturbances in life with minimal loss of function. Resilience can be enhanced by optimizing early-life conditions. In poultry, eggshell temperature (EST) during incubation and early feeding are two early-life conditions that are found to alter neonatal chick quality as well as immune response in later life. However, whether these early-life conditions affect disease resilience of chickens at later ages has never been studied yet. Hence, we studied the effects of EST [(37.8°C (control) or 36.7°C (lower)] during late incubation (≥embryonic days 17–19.5) and feeding strategy after hatch [immediately (early feeding) or 51–54 h delayed (delayed feeding)] on later-life broiler resilience in a 2 × 2 factorial arrangement. At hatch, 960 broilers of both sexes from a 54-week-old Ross breeder flock were equally divided over 32 pens (eight replicate pens per treatment combination) and grown for 6 weeks. Necrotic enteritis was induced by a single inoculation of Eimeria spp. at d 21 and repeated Clostridium perfringens inoculation (3×/d) during d 21–25. Mortality and body weight (BW) gain were measured daily during d 21–35 as indicators of resilience. Additionally, disease morbidity was assessed (gut lesions, dysbacteriosis, shedding of oocysts, footpad dermatitis, and natural antibody levels in blood). Results showed a lack of interaction between EST and feeding strategy for the vast majority of the variables. A lower EST resulted in lower BW gain at d 5 and 8 post Eimeria inoculation (P = 0.02) and more Eimeria maxima oocysts in feces at d 8 post Eimeria inoculation compared to control EST (P < 0.01). Early feeding tended to lower mortality compared to delayed feeding (P = 0.06), but BW gain was not affected by feeding strategy. Morbidity characteristics were hardly affected by EST or feeding strategy. In conclusion, a few indications were found that a lower EST during late incubation as well as delayed feeding after hatch may each impair later-life resilience to necrotic enteritis. However, these findings were not manifested consistently in all parameters that were measured, and conclusions are drawn with some restraint.
Highlights
There is an increased global concern about the high use of antimicrobials and potentially related resistance threats [1]
The percentage of dead or culled broilers post Eimeria inoculation (PEI) did not show an interaction between eggshell temperature (EST) and feeding strategy (Table 1; P ≥ 0.28) nor a main effect of EST (P ≥ 0.48) or feeding strategy (P ≥ 0.11)
Regardless of the d PEI, body weight (BW) did not show an interaction between EST and feeding strategy (P = 0.30) nor showed a main effect of EST (Figure 1A; P = 0.37)
Summary
There is an increased global concern about the high use of antimicrobials and potentially related resistance threats [1]. Efforts are made in various areas to reduce the usage of antibiotics. In animal husbandry, this reduction in antibiotics usage led to a rising interest in alternative approaches to enhance animal health, e.g., by enhancing animal resilience. Environmental disturbances can be for instance changes in social structures, thermal conditions, or disease outbreaks. When focusing on the latter one, a resilient animal has a lower chance to become ill, and once it does become ill, it will show rapid recovery. Increased animal resilience may lead to a lower need of antibiotics, improved animal welfare, and beneficial revenues and sustainability. Resilience of animals is likely affected by early-life conditions, because critical windows for immune organ development exists during early life [3] and environmental conditions in this period can affect the animal’s immune system in later life [4]
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