Feeding a persistent laying hen: Effect of dietary amino acid levels in rearing and dietary energy source and level in laying on body composition and metabolism

The level and source of dietary protein and energy provided during rearing and laying might influence body composition and metabolic functions of laying hens. We therefore studied the influence of a low or high Apparent Fecal Digestible (AFD) Lys level in all rearing diets and constant or reduced ME level and source during laying (Reducing Energy over time with High Oil = REHO; Constant Energy High Oil = CE; Reducing Energy over time with Low Oil = RELO) on body composition and metabolism in a 2 × 3 factorial design. Dekalb White pullets were randomly divided over 8 pens per treatment and housed until 110 wk of age. Body composition (relative breast, abdominal fat pad and liver weights and total body chemical composition of crude fat, CP, ash and moisture) and liver crude fat levels were measured 4 times during rearing and at 8 wk intervals during laying. Plasma metabolic markers (triglyceride, free fatty acids) were measured 5 times and adipokines 3 times during laying. Data were subjected to mixed model analyses. Hens fed RELO compared to REHO diets had elevated plasma free fatty acid and triglyceride levels in some weeks, heavier relative liver weights with higher liver crude fat levels in most sampled timepoints, indicating de novo lipoprotein synthesis. Segmented regression models showed that relatively less body fat was directed towards abdominal fat in hens fed RELO diets, with a greater proportion accumulating in other fat depots, such as the liver. Correlations showed that hens with higher relative abdominal fat pad weights between wk 52 and 84 had lower ADFI and FCR in wk 52 to 110. This indicates abdominal fat is needed to supply sufficient ME in the final phases of laying. Higher plasma chemerin levels correlated to a lower BW, egg weight, abdominal fat deposition but higher liver crude fat levels. Adiponectin showed opposite effects. Feeding REHO diets indicated better fat utilization to support egg production in long-term producing hens.