Intermittent Lighting: Impact on Gut Health and Performance of Broiler Chickens

Abstract

<p>Three animal experiments were conducted to assess the effects of intermittent lighting (IL) on the performance and gut health of broiler chickens. </p> <p>The first experiment studied the impact of light intermittency on the resilience of broilers to a sub-clinical necrotic enteritis challenge. Performance, lesion score, digesta viscosity and short chain fatty acid (SCFA) production were determined following the induction of sub-clinical necrotic enteritis in birds raised under both continuous lighting (CL, 18L:6D) and IL (1 h of light [L]:3 h of dark [D]:1L:3D:1L:3D:1L:3D:2L:6D). Particular attention was given to the days following the infection to understand how lighting programs influence the coping mechanisms developed by birds challenged by an enteric disease. Birds raised under IL were more efficient than those raised under CL in particular during the height of infection. Most importantly, the innate protective mechanism of broilers to reduce feed intake in case of enteric diseases was outweighed by the voracious appetite of CL birds.</p> <p>The primary objective of the second experiment was to understand whether improvements in nutrient (nitrogen and starch) digestibility would explain the apparent efficient advantage of birds raised under IL. Also, light intermittency and its interaction with exogenous enzymes was ascertained in terms of broiler performance, feed transit time, plasma metabolites, and nitrogen and starch digestibility. Within IL birds, the progression of protein and starch digestion through time and the changes in plasmatic metabolites were studied. Neither nitrogen nor starch digestibility could explain the improvement in feed efficiency for IL birds. Also, IL did not further improve the effects of exogenous enzymes in terms of performance and nutrient digestibility. However, results obtained reflect the phenomenal ability of broilers to withstand regular intervals of feed deprivation by regulating feed digestion and nutrient metabolism. </p> <p>A third experiment attempted to explain efficiency improvements of IL birds through reduced heat increment and thus increased net energy of feed. In order to achieve that, an energy assay using closed-circuit respiratory chambers was performed to allow for the calculation of metabolizable and net energy of feed, and total heat production, heat increment, and respiratory quotient of broiler chickens. None of the parameters was affected by light intermittency; however, the methods used in this study might have limited the extent to which the results could be interpreted. </p> <p>In parallel with a larger experiment, bone-related characteristics of IL and CL birds such as breaking strength and mineralization were assessed and associated with legproblem-related culls, growth rate and Ca and P levels in plasma. Results reflected the tight regulation of mineral plasmatic concentrations. Most importantly, the slower initial growth of IL birds in comparison with CL birds was identified as the main driver for the more complete mineralization and the stronger tibias in these birds. Also, birds raised under IL presented lower percentage of culling due to leg-related problems.</p> <p>Finally, results of an ancillary study designed to measure feed intake in IL and CL birds, particularly during periods of darkness, are shown. Albeit limited in scope and time, data generated indicate that a large proportion of feed consumption in IL birds occurs in the dark. Findings contradict the initial – and widely accepted – assumption that ‘feed intake during periods of darkness is largely negligible’ and encourage further research on this topic, specifically with focus on behaviour.</p> <p>This research revisited and expanded some of the IL-related topics studied in the 1970s through the 1990s and reminded of the importance of ancestral organ physiology and feeding behaviour for the progress of an exceptionally technologically advanced poultry industry.</p> <p>In summary, this work reveals the potential of IL programs, in particular one with recurring intervals of 1 h of light and 3 h of darkness, to enhance performance and manipulate nutrient intake, to manage gut health, and to improve skeletal integrity in fast-growing broilers. Manipulating the use of the crop and the other parts of the digestive tract through intermittent feeding has great potential to help overcome some of the current challenges in poultry production</p>