Source: UNIVERSITY OF VERMONT submitted to
HORMONAL CONTROL OF GROWTH AND ENERGY USE BY CHICKENS DEFICIENT IN AMINO ACIDS.
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
Reporting Frequency
Annual
Accession No.
0183037
Grant No.
(N/A)
Project No.
VT-AS-00605
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Oct 1, 1999
Project End Date
Sep 30, 2003
Grant Year
(N/A)
Project Director
Carew, L. B.
Recipient Organization
UNIVERSITY OF VERMONT
(N/A)
BURLINGTON,VT 05405
Performing Department
ANIMAL SCIENCE
Non Technical Summary
(N/A)
Animal Health Component
(N/A)
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
30232201010100%
Goals / Objectives
To determine if low dietary levels of amino acids alter growth, growth hormone, insulin-like growth factors, thyroid hormones,organ histology, and energetic efficiency of growing chickens in order to find means to increase the economy of meat production and reduce envirionmental nitrogen pollution.
Project Methods
Chicks will be fed diets containing suboptimal levels of growth hormone, insulin-like growth factors, and thyroid hormones will be measured by radioimmunoassays. Organs will be examined microscopically. Energetic efficiency will be measured by determining the partition of energy intake into energy retention and heat loss using body composition analysis and calorimetry.

Progress 01/01/03 to 12/31/03

Outputs
Final data on the effects of dietary Met and Lys deficiencies on growth and endocrine changes in broilers were summarized. Compared to control (0.5% Met), a mild deficiency of Met (0.4% of diet) increased feed intake with no change in body weight while greater deficiencies (0.3, 0.2%) caused reductions in both feed intake and growth. Liver weights were heavier in chicks fed 0.3 and 0.2% Met but not 0.4% Met. Plasma triiodothyronine (T3) was higher in all deficient chicks, but significant only with 0.3%. However, with 0.3 and 0.2% Met plasma T3 was significantly elevated compared to pair-fed controls (0.5% Met). Plasma thyroxine (T4) was lower in all deficient groups but was significant only with 0.2% Met. Plasma levels of insulin-like growth factor-I (IGF-I) were consistently but not significantly lower in all deficient chicks and deserve further study. Plasma IGF-II was significantly less in chicks fed 0.2% Met. It was concluded that deficiencies of dietary Met altered plasma levels of T3, T4 and IGF-II, but this was dependent on the degree of deficiency. Final data with Lys deficiencies showed that all deficient levels from mild to more severe (0.88, 0.66, 0.54% of diet) caused graded reductions in both feed intake and growth rate compared to a free-fed control (1.10% Lys). Liver weights were unaffected. Plasma T3 was elevated in chicks fed 0.88 and 0.66% Lys compared to the free-fed control, and were elevated in chicks fed 0.66 and 0.53% compared to pair-fed controls. Plasma T4 was unaffected. Plasma IGF-I was significantly lower with 0.53% Lys, but this was solely a consequence of restricted feeding as determined by comparison with pair-fed chicks. Plasma IGF-II was unaffected. It was concluded that the primary effect of Lys deficiencies is an elevation in plasma T3 with no change in T4. There was no direct effect of the Lys deficiencies on plasma IGF-I or -II. These two studies demonstrate that deficiencies of essential amino acids affect patterns of feed intake, liver weights, and plasma levels of thyroid hormones and insulin-like growth factors in different ways.

Impacts
Our studies show that deficiencies of essential amino acids (EAA) exert some of their effects on avian growth and development through changes in the endocrine system. Nutritionists are increasingly formulating poultry diets with minimal protein levels supplemented with pure amino acids to achieve a better EAA balance. This increases the possibility of single amino acid deficiencies. Through studies such as the current ones described for methionine and lysine deficits, we have shown that deficiencies of individual EAA have differing effects of the avian endocrine system. Understanding these relationships will help in adequately balancing low-protein diets that are supplemented with individual amino acids. This should result in improved nutrient balance, reduced costs, and less environmental pollution through reduced nitrogen excretion.

Publications

  • Carew, L.B., J.P. McMurtry and F.A. Alster. 2003. The effects of methionine deficiencies on plasma levels of thyroid hormones, insulin-like growth factor-I and -II, liver and bodyweights, and feed intake in growing chickens. Poultry Sci. 82:1932-1938.


Progress 10/01/99 to 09/30/03

Outputs
This project is a continuation of earlier work which showed that moderate to marked dietary deficiencies of essential amino acids (EAA) have differing effects on the endocrine system of growing chickens. However, the new protocol was modified to study the effects of milder to borderline EAA deficiencies, more comparable to those that might occur under practical conditions. The current research also incorporated the study of more hormones. We have now shown that plasma triiodothyronine (T3) is elevated in dietary deficits of lysine (Lys), methionine (Met), and isoleucine (Ile) while it is lower in an arginine (Arg) deficiency. These results are very similar to what occurred with more severe deficiencies of these EAA. Additionally, we showed that a phenylalanine (Phe) deficiency also causes an elevation in T3, an unexpected result because of its role as a precursor of thyroid hormones. The elevated plasma T3 in Met and Ile deficiencies was accompanied by decreases in plasma T4, but T4 was unchanged in deficiencies of Phe and Lys. T4 was elevated in the Arg deficiency. Thus in Met, Ile and Arg deficiencies plasma T3 and T4 moved in opposite directions, but this did not occur with the Phe and Lys deficiencies. These results further support our concept that deficiencies of various EAA have differing effects on the avian endocrine system. In initial studies with insulin-like growth factors I and II (IGF-I and IGF-II), we found that Phe and Arg deficiencies caused depressions in plasma IGF-I, but deficiencies of Lys, Met, and Ile had no effect. Plasma IGF-II was low in a severe Met deficiency but not altered in deficiencies of Lys, Ile and Arg (it was not studied with Phe). Liver weight was heavier in Met and Arg deficiencies, lighter in an Ile deficiency, and unchanged with deficiencies of Phe and Met, again demonstrating differing effects of the individual EAA as well as a lack of correlation of liver growth with plasma levels of thyroid or IGF hormones. Furthermore there was no correlation between plasma levels of thyroid hormones and IGF-I or IGF-II. The effect of EAA deficiencies on growth was also variable. With both Phe and Ile there was a sharp drop in both feed intake and weight gain as the deficiencies progressed. With Lys, a mild deficiency had no effect on either feed intake or weight gain, but both parameters were smaller as the deficiency worsened. In an Arg deficiency, weight gains were smaller but there was little effect on feed intake. With the Met deficiency, feed intake initially increased with no effect on weight gain, but both growth and feed intake diminished as the deficiency progressed. With all EAA deficiencies, growth in the pair-fed controls was almost always better than in the deficient chicks even though both groups consumed the same amounts of diet and energy. We conclude that the effects of a protein deficiency on growth, feed intake, organ weights, and especially circulating levels of thyroid and IGF hormones will vary depending on the specific balance of amino acids present, and that dietary deficits of individual EAA have unique and distinct effects on these parameters.

Impacts
Our studies show that deficiencies of essential amino acids (EAA) exert some of their effects on avian growth and development through changes in the endocrine system. Nutritionists are increasingly formulating poultry diets with minimal protein levels supplemented with pure amino acids to achieve a better EAA balance. This increases the possibility of single amino acid deficiencies. Through studies such as the current ones described for methionine, lysine, isoleucine, arginine and phenylalanine, we have shown that deficiencies of individual EAA have differing effects of the avian endocrine system. Understanding these relationships will help in adequately balancing low-protein diets that are supplemented with individual amino acids. This should result in improved nutrient balance, reduced costs, and less environmental pollution through reduced nitrogen excretion.

Publications

  • No publications reported this period


Progress 01/01/02 to 12/31/02

Outputs
Results accumulated with studies on several essential amino acids (EAA) were analyzed further. With an arginine (Arg) deficiency, chicks fed between 60-80% (0.75% and 1.0%) of the National Research Council recommended level of 1.25% Arg from 8-22 days of age showed no differences in plasma growth hormone (GH) when compared to results obtained with free-fed or pair-fed controls. Since we previously showed that plasma levels of insulin-like growth factor I (IGF-I) decrease in an Arg deficiency, these data suggest that circulating levels of GH are not regulators of IGF-I. Liver color was significantly paler or more yellow in Arg-deficient chicks than in any control group. This, coupled with our earlier observation of enlarged livers in Arg-deficient chicks, suggests that fatty infiltration of the liver occurred in the deficient chicks and should be studied further. With a phenylalanine (Phe) deficiency, plasma levels of GH were markedly elevated showing that Arg and Phe deficiencies of have differing effects on this hormone. Thyroid weights in Phe-deficient chicks were heavier but on histological examination follicles were smaller with a severe Phe deficiency. This was accompanied by elevations in plasma triiodothyronine as reported earlier. These studies continue to show that deficiencies of individual EAA have markedly different effects on the endocrine system. Thus, physiological and hormonal changes observed in protein deficient animals are not a consequence of EAA deficiencies in general but are most likely related to the specific pattern or profile of limiting EAA present in the diet.

Impacts
Our studies show that deficiencies of essential amino acids (EAA) exert some of their effects on growth and development through changes in the endocrine system. Nutritionists are increasingly formulating diets with minimal protein levels supplemented with pure amino acids to achieve a better EAA balance. This increases the possibility of single amino acid deficiencies. Through studies such as the current ones reported for arginine and phenylalanine deficits, we show that deficiencies of individual EAA have differing effects on the avian endocrine system. Understanding these relationships will help in adequately balancing low-protein diets that are supplemented with individual amino acids. This should result in improved nutrient balance, reduced costs, and less environmental pollution through reduced nitrogen excretion.

Publications

  • Carew, L.B., Alster, F.A. Vasilatos-Younken, R., McMurtry, J.P. and Zakrzewska, E.I. 2002. Changes in organ size and plasma levels of thyroid hormones, growth hormone and insulin-like growth factors in chicks fed diets deficient in arginine. Poultry Sci. 81 (Suppl. 1):68.
  • Carew, L.B., Valverde, M.T., Zakrzewska, E.I., Alster, F.A. and Gernat, A.G. 2002. Raw velvet beans (Mucuna pruriens) and L-dopa have differing effects on organ growth and blood chemistry when fed to chickens. In: Proceedings of the International Workshop, "Food and Feed From Mucuna: Current Uses and the Way Forward." Pp. 272-287. Eds. M. Flores B., M. Eilitta, R. Myhrman, L.B. Carew and R.J. Carsky. International Cover Crops Clearinghouse (CIDICCO), P.O. Box 4443, Tegucigalpa, Honduras.


Progress 01/01/01 to 12/31/01

Outputs
In earlier research we showed that deficiencies of individual essential amino acids vary markedly in their effect on the avian endocrine system. Arginine (Arg) deficiency at 60% of the required amount was among those that caused a severe deficiency in growth coupled with an elevation in the thyroid hormone, triiodothyronine (T3). We have now studied further the effect of a milder deficiency of Arg on growth parameters, plasma thyroid hormones, and insulin-like growth factors I and II (IGF-I and II). Chicks were originally fed 80% and 70% of the NRC requirement (1.25%) for Arg (1.0% and 0.875% of the diets, respectively) for two weeks (8-22 days of age). When no growth depression was observed after one week with 80% Arg, the level was dropped to 60% of the requirement (0.75% of the diet). Two-week weight gains were significantly depressed to a similar degree by both Arg deficiencies. Feed consumption was not altered by either deficiency. Plasma T3 was significantly lower in chicks fed 60% Arg compared to 70% but was not different from the free-fed or pair-fed controls. Plasma thyroxine was significantly elevated in chicks fed 60% Arg compared to the free-fed controls but not compared to their pair-fed controls. However, plasma IGF-I, compared to all controls, was significantly lower in chicks fed both deficient levels of Arg and the depression was significantly greater with the most severe deficiency. Plasma IGF-II was unaffected by any treatment. Liver weights, relative to body weight, were much heavier in the deficient chicks compared to any control. Thyroid weights were also heavier, but they were significantly different from pair-fed controls only with the most severe deficiency. We conclude that a dietary Arg deficiency has a major effect on circulating IGF-I levels, but plasma thyroid hormone levels are only slightly affected. Liver and thyroid weights also change markedly in response to an Arg deficiency, although thyroid weights increased only with the most pronounced deficiency. These prominent changes in response to an arginine deficit deserve further study to fully understand the biological role of this essential amino acid.

Impacts
Our studies show that deficiencies of essential amino acids (EAA) exert some of their effects on growth and development through changes in the endocrine system. Nutritionists are increasingly formulating diets with minimal protein levels supplemented with pure amino acids to achieve a better EAA balance. This increases the possibility of single amino acid deficiencies. Through studies such as the current one with an arginine deficit, we have shown that deficiencies of individual EAAs have differing effect on the avian endocrine system. Understanding these relationships will help in adequately balancing low-protein diets that are supplemented with individual amino acids. This should result in improved nutrient balance, reduced costs, and less environmental pollution through reduced nitrogen excretion.

Publications

  • No publications reported this period


Progress 01/01/00 to 12/31/00

Outputs
We have shown that dietary deficiencies of most essential amino acids (EAA) either increase or have no effect on circulating levels of certain hormones, especially the thyroid hormone, triiodothyronine (T3). However, our work did not include the EAA, phenylalanine (Phe). Reports in the literature suggest that plasma thyroid hormone levels decrease in a Phe deficiency as might be expected due to its role as a precursor of T3. Therefore, we studied this EAA under our experimental conditions. Nutritionally complete control diets containing 0.98% Phe and 0.36% tyrosine (Tyr) were fed to chicks through 8 days of age. These diets were composed of a 50/50 mixture of a commercial-type diet, composed mainly of corn and soybean oil meal, and a purified diet in which the protein content was supplied as pure individual amino acids. This allowed dietary manipulation of levels of individual EAA. From 9-23 days chicks were fed the control diet and diets containing deficient levels of 0.71% or 0.44% Phe. Tyr was kept constant at 0.36%. Groups of chicks fed the control diet were also pair-fed on a daily basis to the intake of the deficient groups. Both deficient levels of Phe caused marked reductions in growth and feed intake, but growth of the pair-fed controls was always greater than the deficient group. Relative heart weights were heavier in deficient chicks but liver weights were little affected. Contrary to expectations, plasma T3 increased in the Phe deficiency especially compared to pair-fed controls. Thyroxine was unaffected. Plasma levels of insulin-like growth factor-I (IGF-I) were depressed by the severe deficiency. In a similar experiment with a deficiency of isoleucine (Ile) in which chicks had shown an elevation in plasma T3, plasma IGF-I levels were unchanged. These results show that in the presence of constant dietary Tyr, Phe, a precursor of thyroid hormones, does not result in the expected decrease in plasma T3; instead plasma T3 increases. Also, deficiencies of different EAA resulted in differing effects on plasma IGF-I; Phe deficiency caused a decrease while an Ile deficiency had no effect. Thus, deficiencies of different EAA may exert their physiological effects through changes in different hormonal mechanisms and these must be studied individually. Also, the balance between essential amino acids, such as Phe and Tyr, may influence their effects on hormonal mechanisms and this must be studied further.

Impacts
We have shown that dietary deficiencies of essential amino acids (EAA) may exert their effects on growth and development through changes in blood levels of certain hormones. The picture is complicated and shows that amino acid balance as well as specific changes in different hormones, such as thyroid hormones and insulin-like growth factors, must be taken into account. Understanding these relationships will help promote the replacement of intact protein with EAA in animal diets. This will result in improved nutrient balance, reduced costs, and less environmental pollution through reduced nitrogen excretion.

Publications

  • Carew, L.B., E.I. Zakrzewska, J.P. McMurtry, R. Vasilatos-Younken and F.A. Alster. 2000. Growth, thyroid histology, organ weights, and plasma levels of thyroid hormones, insulin-like growth factors and growth hormone in broilers fed diets deficient in phenylalanine. Poultry Sci. 78:331.