Amino Acid Supplemented Diets Varying in Protein Levels for Laying Hens06 October 2014
A new study from China examines the responses of laying hens to lower-protein diets with supplements of individual essential amino acids. Diets lower in crude protein did not affect egg production or bodyweight yet they did lower nitrogen excretion.
The ideal amino acid concept is increasing by being applied to laying hens, according to Qi Guang Hai of the Chinese Academy of Agricultural Sciences in Beijing and co-authors there and with Evonik in China and Germany,
They explain in their paper in Journal of Applied Poultry Research that understanding the responses of modern laying hens to decreasing levels of dietary protein balanced with crystalline amino acids has yet to be examined.
In their study, five dietary treatments varying in crude protein content (18.0, 17.5, 17.0, 16.5, and 16.0 per cent) were formulated at a fixed dietary energy concentration of 2,825kcal of metabolisable energy (ME) per kg of feed.
The crystalline amino acids, including methionine, threonine, isoleucine, valine, tryptophan, and lysine, were supplemented according to an assumed ideal amino acid profile, and all diets contained 0.831 per cent ileal digestible lysine.
Irrespective of the crude protein levels, the ratio of lysine and the profile of different essential amino acids in relation to lysine remained similar in all the diets.
A total of 540 21-week-old Hy-Line W36 hens were used with six replicates per treatment group. This trial was conducted for a period of 14 weeks, ranging from week 21 to 34.
Egg production, daily egg mass, feed intake and feed conversion ratio were unaffected in the low-protein groups.
Egg weight and nitrogen excretion declined, whereas egg yolk colour increased in the low-protein groups.
Decreasing dietary crude protein was found to have no effect on blood ammonia and plasma uric acid.
The application of the assumed ideal amino acid profile can lead to reduced dietary protein level, from 18 to 16 per cent, without affecting the production performance of laying hens from 21 to 34 weeks of age, the researchers found.
The ratios of standardised ileal digestible methionine, methionine + cystine, threonine, tryptophan, arginine, isoleucine and valine to standardised ileal digestible lysine were 50, 91, 70, 21, 104, 80 and 88 per cent, respectively, in the assumed ideal amino acid profile.
Qi and co-authors added that nitrogen excretion was significantly decreased from hens fed the protein-reduced diet without impairing bodyweight.
Ji F., S.Y. Fu, B. Ren, S.G. Wu, H.J. Zhang, H.Y. Yue, J. Gao, A. Helmbrecht and G.H. Qi. 2014. Evaluation of amino-acid supplemented diets varying in protein levels for laying hens. J. Appl. Poult. Res. 23:384-392. doi: 10.3382/japr.2013-00831
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