The effect of dietary composition on the water balance of laying hens

Smith, Adam (1997). The effect of dietary composition on the water balance of laying hens. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000fe79

Abstract

12 experiments measured quantitatively the response in excreta moisture of laying hens to dietary concentrations of nutrients and non nutrient components which met or exceeded recommended requirements. Experiments 1-4 measured the response in excreta moisture to dietary sodium, potassium, phosphorus and calcium. Experiment 5 examined the response to 2 sodium salts (bicarbonate or chloride) and for phosphorus x sodium interactions. Linear increases in excreta moisture were produced with increased dietary sodium (Y=719.65+8.12+-1.55X) potassium (Y=570.76+11.95+-2.01X) and phosphorus (Y=723.50+5.59+-0.308X). Dietary calcium concentration had no effect on excreta moisture. Experiments 6-9 measured the response in excreta moisture to dietary crude protein, lysine, methionine and amino acid availability. There were linear increases in excreta moisture with crude protein (Y=410.85+1.32+-0.076X) and lysine (Y=S97.10+0.526+-0.073X). Methionine concentration had no effect on excreta moisture. Reduced amino acid availability gave a linear decrease in excreta moisture (Y=595.93+0.154+-0.048X). Experiments 10-11 measured the response in excreta moisture to dietary resistant starch, differing cereal sources and wheat bran concentration. Linear increases in excreta moisture (Y=679.97+0.170+-0.029X) were produced with increased dietary resistant starch. Cereal source had no effect but wheat bran increased excreta moisture. Experiment 12 measured the response in excreta moisture to dietary fat concentration, saturation and oxidation. There were no effects on excreta moisture. An experiment involving 1440 caged laying hens aimed to describe the change in dirty egg numbers with increases in excreta moisture. Raised excreta moisture gave linear increases in dirty egg numbers (Y=-19.92+0.0367+-0.00430X). A quantitative model was developed using experimental data to attempt prediction of dirty egg numbers from dietary nutrient composition. The nutrient composition of commercial feed samples were fitted and dirty egg numbers predicted. Predicted and commercially determined dirty egg numbers for each feed were incorporated in a regression analysis to validate the model. There was a significant linear relationship between predicted and commercially determined dirty egg numbers. Variation in dietary composition is therefore a major factor effecting excreta moisture and dirty egg output of caged laying hens.