Effect of force-feeding diets containing varying amounts of lysine on plasma free amino acids in laying hens

Weight gain, feed conversion efficiency and plasma free lysine as response criteria in evaluating supplements of lysine plus threonine and lysine plus tryptophan to deficient diets for rats

Two experiments were conducted on growing male SPF-rats to compare weight gain, feed conversion efficiency and plasma free lysine concentration as response criteria in evaluating adequacy of lysine plus threonine and lysine plus tryptophan supplements to the deficient diets. Two basal semisynthetic diets were prepared limiting in lysine and threonine (Expt. 1) and lysine and tryptophan (Expt. 2). The addition of graded supplements to the basal diets of L-lysine X HCl alone (0.2; 0.4; 0.6; 0.8 and 1.0% of diet) induced imbalance of amino acids resulting in low level of daily weight gain and feed conversion efficiency. Plasma free lysine concentration started to grow linearly from the first supplement of L-lysine X HCl. If rats were fed the diets containing identical supplements of L-lysine X HCl in combination with two supplements of L-threonine (0.2 and 0.4% of diet, Expt. 1) or L-tryptophan (0.05 and 0.1% of diet, Expt. 2), plasma free lysine started to increase before supplements of amino acids were adequate to support maximum weight gain and feed conversion efficiency. this difference in response seems to be caused by different feeding regiment during the growth period of the experiments (ad libitum) and training period prior to blood sampling (feeding twice daily).

[Effect of graded dietary protein rations on the amino acid content of crude protein in various parts of the gastrointestinal tract and blood fractions of laying hens]

Four groups of four colostomized laying hens each received rations only consisting of wheat, vitamins plus a mineral mixture and a graded daily feed supply of 110 g, 88 g, 66 g and 44 g. The determination of amino acids from faeces was carried out after hydrolysis from a 6-day sampling period from the 16 laying hybrids. At the end of the experiment the animals were slaughtered. The corpuscular fractions of the blood, the contents of crop and stomach as well as of the intestines were also hydrolysed and the amino acid content in the crude protein was determined. In addition, the content of free amino acids in the blood plasma was determined. The content of amino acids in the protein of the corpuscular blood fractions remained uninfluenced by the decreasing amino acid and energy supply. The content of free basic amino acids in the blood plasma decreased with the decreasing supply with amino acids and energy, whereas the content of free amino acids with branched chains and hydroxylized ones increased. The content of glutamic acid in the contents of crop and stomach changed considerably in comparison with feed protein. The amino acid values of the crude protein in the contents of the intestines and in faeces to a large extent differ considerably from those of the wheat fed and are approximate values of body protein. Deficient supply with amino acids and energy did not influence the apparent digestibility of the amino acids.

Individual variation in the content of free amino acids observed in the blood and muscle of chicks fed a single meal daily

1. Fifty broiler chicks in individual cages, were fed on a balanced diet ad libitum until 10 d old and then given a single meal daily. Blood and pectoral muscle samples were taken from each. Free aspartic acid, threonine, serine, glutamic acid, glycine, alanine, valine, cystine, isoleucine, leucine, phenylalanine, lysine and arginine were determined. 2. Free amino acid concentrations varied greatly between birds. Values for the coefficient of variation ranged from 0.21 for serine in both tissues to 0.571 and 0.749 for valine and lysine in blood and muscle respectively. 3. Many correlations for pairs of amino acids did not seem related to the body weight of chicks.

Appearance of D-alloisoleucine in the blood plasma of laying hens

Two strains of laying chickens were used to investigate the effects of amino acid additions, including D-alloisoleucine, to a low protein corn-soy diet on plasma free amino acids and egg albumen amino acid composition. Intake of .1% D-alloisoleucine with the L-form in the mixture resulted in appearance of this compound in the plasma but not in egg albumen. The concentration of plasma valine was significantly increased when the amino acid (.2% D-L) was added to the 10% protein diet. Threonine and arginine additions did not increase the concentration of the respective amino acid in the plasma significantly. The amino acid composition of egg albumen remained unaffected by dietary supplementation. Production data along with amino acid composition of egg albumen showed that the laying hen reduces production rather than altering amino acid composition of egg albumen protein in its response to reduced uptake. No apparent strain differences were noted.

[The metabolism of colostomised laying hens with 15N-labelled wheat. 4. 15N-Incorporation in the corpuscular components of blood, in the blood plasma and the basic amino acids]

Three colostomised Laying hybrids received over four days a dosage of 672 mg 15N-excess (15N'), 20.3 mg lysine 15N', 23.0 mg histidine-15N' and 66.7 mg arginine-15N' with a ration customary in production. After feeding the same nonlabelled ration for another four days the hens were killed and the N-content of the blood as well as of its fractions (corpuscular components, plasma, free amino acids of the plasma) was determined.

The amino acid requirements of the preruminant calf

1. Ten calves (50--58 kg live weight) were given a diet consisting of diluted whole milk, wheat gluten and supplemented with appropriate nutrients including amino acids but deficient in lysine. The lysine reequirements of these calves, which were growing at approximately 0.25 kg/d, were estimated from responses to lysine supplementation of this diet. From plasma urea, plasma lysine, nitrogen retention and apparent digestibility of N responses the estimated lysine requirements were 8.5, 7.5, 7.2 and 7.6 g/d respectively. 2. From the mean lysine requirement (7.8 g/d) and the ratio, lysine: otheressential amino acids in carcasses of similar calves the estimated requirements were (g/d): methionine 2.1, cystine 1.6, threonine 4.9, valine 4.8, isoleucine 3.4, leucine 8.4, tyrosine 3.0, phenylalanine 4.4, histidine 3.0, arginine 8.5, tryptophan 1.0.