EFFECTS OF AMBIENT-TEMPERATURE AND METHIONINE SUPPLEMENTATION OF A LOW-PROTEIN DIET ON THE PERFORMANCE OF LAYING HENS

The effects of ambient temperature and the supplementation of methioni ne to a low protein diet on egg production, egg quality, blood constit uents and nitrogen excretion of laying hens were studied. The objectiv e was to derive an environmental friendly feed formulation for warm cl imate. Seventy-two 29-week-old commercial White Leghorn hens of Babcoc k ISA white strain were used in this trial. The design is a completely randomized design with a 2x3 factors arrangement of treatments. Two c onstant ambient temperatures were 24+/-1 degrees C and 34+/-1 degrees C with 85% relative humidity. The three dietary treatments were 170 g kg(-1) crude protein, 140 g kg(-1) crude protein and 140 g kg-l crude protein supplemented with methionine 1.4 g k(-1). Hens were allotted i nto six groups according to egg production and body weight. Birds were raised in individual wire cages for the experimental feeding period o f five weeks. At the end of the feeding trial, one replicate of laying hens (four birds) from each treatment were selected for a four-day me tabolic study for the daily collection of the excreta. The blood sampl es were withdrawn from the wing vein for analysis of hematocrit, blood glucose, sodium, potassium, magnesium, calcium, phosphorus and uric a cid. Experimental results indicate that increases in ambient temperatu re significantly depress feed intake, egg production, egg weight and l ive weight of laying hens. High ambient temperature also caused inferi or egg quality, including shell weight, shell thickness, shell breakin g strength and specific gravity. Ambient temperature also changes the egg components with heavier egg albumin and yolk in the low-temperatur e group. Increasing ambient temperature also caused an increase in pH value in the plasma. This increase revealed a trend of depressed gluco se (P<0.05) in the plasma of the laying hens. The dietary treatments, however, did not significantly influence feed intakes. Except egg weig ht, laying hens that were fed with the low protein (140 g kg(-1)) with methionine supplemented diet produced similar numbers of egg and feed conversion as the layers fed with the high protein diet. The low prot ein with methionine supplemented diet produced significantly lighter e ggs than the high dietary protein diet under the high ambient temperat ure, but produced heavier egg under the low ambient temperature. The c oncentration of uric acid in the plasma and nitrogen in the excreta of the high protein group was significantly higher than the other two lo w protein dietary groups (P<0.05). (C) 1998 Elsevier Science B.V.