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The Effects of Glucocorticoids on Meat Quality in Broiler Chickens

Glucocorticoids In Chickens

Glucocorticoids belong to a group of steroid hormones called corticoids. Their main role is the metabolism of lipids and proteins. However, they also play a role in the immunity. In chickens, glucocorticoids are produced in the adrenal gland. Glucocorticoids produce effects by binding to receptors on the surface of the cell membrane or in the cytoplasm. A chemical signal is initiated. Corticosterone is the most significant glucocorticoid in birds. Its production is stimulated by other hormones including calcitonin.

Carbohydrate Metabolism

Corticosterone has many effects on carbohydrate metabolism: Increase in blood glucose level. Increase in insulin concentrations Glucose uptake is increased A decrease in glucose uptake is a response to either insulin or nitric acid Decrease in circulating concentrations of nitric oxide. Increase in breast muscle glycogen.

Despite the marked effects on glucose metabolism, circulating concentrations of corticosterone unchanged in chickens receiving glucocorticoid administration. There is a growing viewpoint that corticosterone acts via induction of insulin. Evidence for corticosterone inducing insulin resistance comes from the consistent in circulating concentrations of both glucose and insulin and the decreased glucose uptake evoked by insulin as indicated 2 deoxy-- glucose uptake by fibularis longus muscle in vitro.

Protein Metabolism

Corticosterone has several effects on protein metabolism in chickens: Decrease in body weight, particularly breast muscle weight. Increase in breakdown of muscle protein due to decreased sythesis and increased degredation. Decrease in circulating concentrations of amino acids and increased concentrations of urate. These are indicative of both increases in deamidation of amino acids and gluconeogenesis. Increase in gluconeogenesis by perfused liver.

Lipid Metabolism

Corticosterone has many effects on lipid metabolism in chickens: Increase liver weight. Increased hepatic lipogenesis Increased abdominal and subcutaneous adipose weight. Increased circulating concentrations of non esterified fatty acids Increased circulating concentrations of triglyceride and very low density lipoprotein Increased adipose lipo protein lipase (LPL)

Immune Effects Of Corticosterone

Corticosterone administration to chicken results in reductions in weight of the Bursa Fabricus and spleen. It also induces an initial improvement of the antibody response to Infectious Bronchitis Virus (IBV) vaccination followed by an impairment of the response to IBV. It also increases the heterophil to lymphocyte (H/L) ratio in the circulation. Corticosterone increases expression interleukins interleukins -1beta, IL-6, IL-10, IL-12alpha and IL-18 while decreasing that of chemokine C-C motif ligand (CCL)16 and transforming growth factor-beta4 in heterophils in the circulation of chickens.

Other Metabolic Effects Of Corticosterone

Other metabolic effects of corticosterone in chickens include the following: Increasing expression sodium and glucose co-transporter 1 and peptide transporter 1mRNA in the duodenum. Increasing expression of genes related to obesity in the chicken hypothalmus including brain deprived neutrophic factor, neuropeptide Y and agouti- related protein. Depressing adenosine deaminase activity in all regions of the chicken gastro intestinal tract except the proventriculus.


Corticosterone and Growth

Glucocorticoids including the endogeneous avian steroid corticosterone and the synthetic dexamethasone depress growth in chickens. The following are the effects: Decreased skeletal muscle growth Increased protein degredation as indicated by increases in the concentrations of 3- methyl histidine in both the pectoral and femoris muscles. It increases muscle proteolysis There is reduced skeletal protein synthesis as indicated by the RNA:protein ratio It decreases the growth of the small intestine in chickens Increased expression of myostatin It depresses duodenal and jejunal villus height and crypt depth It has a vital role in inducing functioning somatotrophs during late embryonic development.

Growth Retardation Effects Of Glucocorticoids In Chickens

The main known symptoms of the action of glucocorticoids in birds are increased glucose production by the liver by increasing gluconeogenesis from amino acids. Liver glycogen stores are markedly increased and blood sugar levels are elevated .Urinary nitrogen increases due to the increased breakdown of amino acids. Growth inhibiton is accompanied by an increase in uric acid excretion and by an increase in liver weight. Liver glycogen deposition is more sensitive to glucocorticoids compared with other effects. Glucocorticoids can also cause involution of the bursa fabricus . Friedmann investigated the relationship of glucocorticoids to glucagon and reported data supporting the view that glucocorticoids play a permissive role in the regulation of gluconeogenesis by glucagon. The research of Izzo and Glasser suggests that hydrocortisone and glucagon each cause protein catabolism by a different mechanism. Glucagon facilitates the catabolism of amino acids in the liver while hydrocortisone mobilizes amino acids in extrahepatic tissues. A dual physiological role of glucagon in stimulating gluconeogenesis as well as glycogenolysis was pointed out by Sokal. Considering the above interrelationships, it was postulated that the administration of glucocorticoids and/or glucagon to a growing organism would interfere with its inherent growth potential. The objective of this research was to find a growth retarding agent which would stress the growth potential thereby increasing the variance between individuals in their ability to overcome this stress.


Experiment: Growth Retardation Effects Of Glucocorticoids

A group of broiler chickens were used for this experiment. In experiment 1 & 2 the chickens were grown for 21 and 28 days under artificial heat and were fed continuously. In experiment 3 the chickens were kept in 2 different places. Up to 35 days of age they were in batteries. From 35 days to 5 months they were grown in floor pens. While they were in floor pens they were fed a chicken grower diet continuously and given 8 hours of light per 24 hours. Several hormonal drugs were injected into the thigh muscle. These were Lipo adrenal cortex (LAC), Hydrocortisone acetate (HCA) and glucagon (G). One more was administered orally. This was cortisone acetate (CA). The recorded data came from the measurement of body weight, shank length and feed consumption of the different groups that were treated.

Results

Experiment 1

A dose of 38.7mg CA (150mg/kg feed for 6 days) caused a big reduction in comparison to the controls in the gain of body weight between days 14 and 21. There was no effect on liver weight and feed intake.

Effects of LAC, CA and G on several factors in experiment 1

Body weight on day 21 (g)

Percent body weight gain, days 14-21

Liver weight, percent of body weight on day 21

Daily feed intake per bird, day 14-21 (g)

Feed conversion, day 14-21

Between 333 and 434

Between 54.0 and 79.3

Between 2.33 and 2.84

Between 37 and 45

Between 1.42 and 2.02


Table 1.
Effects of LAC, CA and G on several factors in experiment 1

Experiment 2

The gain in body weight between days 14 and 21 showed big differences from the controls in the administration of 69.6, 96.8 and 95.3mg CA per bird. To see the effects of CA, length of administration was significant. The most inhibition towards growth was treatments of CA and G. No visible effect was seen when G alone was given. Between days 14 and 28 and on day 28 the groups treated with HCA showed a great increase in body weight when compared to the control. At the administration of 4mg HCA/100g of body weight and all higher administrations bar the treatment of 8mg HCA/100g of body weight shank growth was decreased The administration of 4-24mg HCA per 100g body weight showed a significant effect on liver weight however there was no great decrease in liver weight after the administration of G. Mean daily intake per bird was decreased in groups administered with HCA also feed conversion was significantly effected in this group. In groups administered with 4mg HCA/100g of bofy weight and 8mg HCA/100g of body weight the amount of injection given was significant. There was more of an effect of one injection of 4mg HCA than the same dose over two days by two injections. There was an opposite effect by the administration of 8mg HCA At levels up to 12mg HCA and levels above 12mg HCA there was an increase/decrease respectively in liver weight as a percentage of body weight at the same rate. While after the maximum response point shank length was mostly constant. To increase the growth rate variance by retarding growth, the administration of 2 or 4mg HCA/100g of body weight in one single injection at 14 days of age may be used.

Effects of CA and/or G on several factors in experiment 2

Total intake of CA per bird (mg)

Percent body weight gain days 14-21

Body weight on day 28 (g)

Percent body weight gain days 14-28

Daily feed intake per bird, days 14-28 (g)

Feed conversions days 14-28

Between 9.2 and 96.8

Between 60.0 and 73.1

Between 585 and 724

Between 171.9 and 208.3

Between 39 and 60

Between 1.47 and 1.92


Table 2.
Effects of CA and/or G on several factors in experiment 2

No closing quotation
No closing quotation

Effects of HCA and/or G on several factors in experiment 2

Body weight on day 28 (g)

Percent of body weight gain, days 14-28 (means)

Shank length on day 28 (mm)

Liver weight percent of body weight on day 28

Daily feed intake per bird, days 14-28 (g)

Feed conversion, days 14-28

Between 222 and 724

Between -2.7 and 191.5

Between 45.0 and 66.5

Between 2.30 and 6.00

Between 26 and 60

Between 1.85 and 26.17


Table 3.
Effects of HCA and/or G on several factors in experiment 2

The results of experiment 3 are shown below in table 4

Compensation of growth retardation caused by one injection of 4 mg HCA/100g of body weight in experiment 3

Body weight

Body weight gain for each period as percent of 14 day weight

Body weight gain for each period as percent of weight at the start of that period

Age of cockerels

Controls

HCA

Diff

Controls

HCA

Diff

Controls

HCA

Diff

14 days

193

207

-

-

-

-

-

-

-

1 month

576

304

Highly Significant

210

64

Highly Significant

210

64

Highly Significant

2 months

1551

1180

Highly Significant

716

458

Highly Significant

161

242

Highly Significant

3 months

2497

2142

Significant

1122

917

Significant

61

82

Significant

4 months

3578

3314

-

1797

1469

-

40

54

-

5 months

3927

3759

-

1885

1686

-

8

13

-


Table 4.
Compensation of growth retardation caused by one injection of 4 mg HCA/100g of body weight in experiment 3


Experiment:Effects of Crating and Transport on Stress and Meat Quality Characteristics in Broiler Chickens

The experiment was undertaken to see how different crating duration times influence stress response and meat quality in broiler chickens and if holding broilers that were in transported in crates influences corticosterone levels and meat quality. Crating and transportation causes an increase in the production of corticosterone due to the stress experienced by the bird. Duration and methods of crating influences the stress response and the level of corticosterone produced. The quality of meat is also affected by the treatment of the bird prior to slaughter. Ehinger (1977) discovered that the tenderness and water holding capacity of broiler meat declined after 2 hours of transportation but increased again after 4 hours of transportation. Cashman (1987) examined the pH, colour and water holding capacity of broiler meat and discovered that meat was paler in birds that underwent a 2 hour journey than those crated for 10 minutes and not transported. This shows that the stress of transport influences the colour and texture of broiler meat. Stress prior to slaughter influences meat quality.

Experiment 1

The experiment was done in two crates with 9 birds in each. A previous experiment showed that 1 and 3 hours of crating resulted in the highest and lowest mean corticosterone concentrations. Birds were starved for 9 hours. They were transported while covered with black sheets to reduce excitement and light exposure. Five birds from each crate were slaughtered. Blood tests were done on each bird to measure plasma corticosterone and catecholamines. Meat quality was assessed by measuring initial pH, shear value and CIE lab colour using m. pectorals superficialis and m. biceps femoris.

Experiment 2

Eight week old broiler chickens were used in this experiment. Nine birds were put in each crate in early morning. In total nine crates were used and 162 chickens. Eighteen crates of birds were transported for 3 hours. Nine crates of birds were held in a dark quiet place for 4 hours before slaughter. The reason for this was that plasma corticosterone levels in starved broilers decreased 1 hour after crating and increase at 3 hours and then it drops to a very low level at 4 hours. The remaining birds were slaughtered immediately. Blood and meat samples were taken and tested from 4 birds in each crate to find the corticosterone level of the blood, pH, shear value and co;our of m. pectorals superficialis and m. biceps femoris. A connection between Corticosterone level and thigh meat colour was seen.

Results

Experiment 1

The results of Experiment 1 are shown in Table 5. No changes are observed in levels of corticosterone, epinephrine or norepinephrine between the two treatments. There are no connections between meat quality and EPI or NE concentrations. There were no changes in pH ,shear value or colour of meat. There was a link between corticosterone levels and hue values of thigh meat.

Effect or two crating periods on stress responses and meat quality characteristics in broilers

Muscle

Stress and meat quality parameters

Crating duration 1hr

Crating duration 3hr

-

Corticosterone levels, ng/ml

9.7

8.9

Epinephrine levels, ng/ml

26.7

33.1

Norepinephrine levels, ng/ml

15.1

21.6

Pectoralis Superficialis

Initial pH

6.04

6.05

Shear value, Kg/g

9.68

12.56

Chroma

17.5

17.4

Hue angle

65.1

63.7

Biceps Femoris

Initial pH

6.43

6.39

Shear value, kg/g

9.49

10.5

Chroma

16.1

15.5

Hue angle

59.9

56.1


Table 5.
Effect or two crating periods on stress responses and meat quality characteristics in broilers

Experiment 2

Table 6 shows the results of experiment 2. The effects of treatment on CORT, initial pH and shear values on breast and thigh samples are shown. Holding the broilers after transport did not influence meat quality characteristics such as shear value and color of breast and thigh meats. Treatment had no effect on the initial pH of breast meat, but it did influence the plasma CORT levels and initial pH of thigh meat. It was shown that holding the broilers for 4 hours in a dark quiet place after transport reduces the stress response. This is shown by the low corticosterone levels.

Mean plasma corticosterone(CORT) levels, initial pH and shear value obtained from broilers processed immediatly after 3hr transport (NH) and from those processed after 4hr transport(H)

Muscle

Stress and meat quality parameters

Treatment NH

Treatment H

-

CORT levels, mg/ml3

11.50

8.50

Pectoralis Superficialis

Initial pH

6.07

6.01

Shear value, kg/g

80.4

7.57

Biceps Femoris

Initial pH

6.57

6.44

Shear value, kg/g

2.68

2.85


Table 6.
Mean plasma corticosterone(CORT) levels, initial pH and shear value obtained from broilers processed immediatly after 3hr transport (NH) and from those processed after 4hr transport(H)


References

1)Sturkie's Avian Physiology, George Causey Whittow, Academic Press, 2000

2)http://pubs.aic.ca/doi/pdf/10.4141/cjas70-086

3)Hormones and Metabolism in Poultry, Colin G. Scanes, University of Wisconsin Milwaukee, USA

4)G. KANNAN, J. L. HEATH,* C. J. WABECK, M.C.P. SOUZA, J. C. HOWE, and J. A. MENCH Department of Poultry Science, University of Maryland, College Park, Maryland 20742 and USDA, Agricultural Research Service, Diet and Human Performance Laboratory, Beltsville, Maryland 20705 http://ps.fass.org/content/76/3/523.full.pdf+html

5)J. S. GAVORA and P. A. KONDRA Department of Animal Science, University of Manitoba, lAinnipeg, Canada. Received June 1, 1970, accepted JuIy 22, 1970 http://pubs.aic.ca/doi/pdf/10.4141/cjas70-086</ref></ref></ref></ref></ref></ref> * *

GlucocorticoidsMeat (last edited 2013-12-03 22:50:41 by 2436E)