Association of Feed to Egg Efficiency With Body Weight and Digestive Organ Characteristics in Laying Hens

The objective of this study was to characterise the individual feed conversion ratio (FCR) of a cohort of laying hens and investigate the relationship of body weight (BW) with feed intake (FI), FCR, and digestive organ parameters. From an initial screening phase (6 weeks) using 450 Isa Brown layers (28-week-old), 50 high feed efficiency (HFE, FCR < 1.8), 50 medium FE (MFE, FCR < 2.0) and 50 low FE (LFE, FCR > 2.3) hens were identified. Individual BW, FI, egg production (EP) and egg mass (EM) were determined in 150 ISA brown (35 weeks of age) laying hens that were given a wheat-soybean meal-based mash diet for 6 weeks (41 weeks of age). To investigate the association of BW with FI and FCR, the data from the 150 birds were collected and digestive organs measurements undertaken on 10 birds per group (n = 30) randomly selected from 150 laying hens. The birds were euthanised and the weights of abdominal fat pad, liver, gizzard, total intestinal tract and pancreas measured. Both FI and FCR had significant positive correlations with the final BW of birds (𝑟 = 0.63, P = 0. 002; 𝑟 = 0.44, P < 0. 01). The percentage of abdominal fat pad weight (P < 0.001) and liver weight (P < 0.01) were lowest for the HFE group followed by the MFE and then LFE groups. A lower gizzard weight in proportion to body weight was noticed in LFE group (P < 0.01) when compared with HFE group of hens. There was a strong positive association between final BW and percent abdominal fat pad weight (𝑟 = 0.95, P < 0. 001). A moderate positive relationship was noticed between final BW and percent liver weight (𝑟 = 0.44, P < 0.01) while a slight negative relationship was found between final BW and percent gizzard weight (𝑟 = -0.31, P = 0.09) of the birds.