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Praca oryginalna Original paper
Triiodothyronine (T3) and thyroxin (T4) are hormo-nes of the thyroid glands and the major regulator of metabolic rate and development of the body. Thyroid hormones have very important effects on metabolism in both mammals and poultry, in excess metabolism rate increase (8, 14) and in deficiency metabolism rate reduce (14). Thyroid hormones affected many stages of carbohydrate metabolism, and increased glucose usage by tissues, and increased gylucogenessis in hart, liver and skeletal muscle (35). In addition, thyroid hormones are necessary for growing and maturation due to increased protein synthesis in growing period (33).
Concentrations of T3 and T4 were positively related with energy balance status (26). The high energy level in the diet increased the concentrations of thyroid hor-mones (23, 24, 31). This effect of energy level was emphasized by Macari et al. (17), Alshaikh et al. (3) and Yambayamba et al. (32). Exposure to environmen-tal heat leads to physiological adjustments in animals, such as increasing of body temperature, decreasing of feed intake and thyroid activity (34). High
environ-mental temperatures reduced plasma concentrations of T3 and T4 (7, 15, 18, 21). However, Aceves et al. (2) reported that heat-acclimation in dairy cattle does not depress thyroid gland activity. Blood metabolites were influenced by the heat stress. Previous studies have suggested a dramatic influence of heat stress on plas-ma glucose, total protein, uric acid, albumin, triglyce-ride and cholesterol (9, 22). Ronchi et al. (27) repor-ted that heat stress led to reduced blood glucose, cho-lesterol, SGOT and SGPT. Marai et al. (19) have shown that serum concentrations of glucose, total protein, creatinine, total lipid and total cholesterol decreased in summer as compared with winter conditions.
Several studies have examined the effects of am-bient temperature and energy level of diet on thyroid status in separate sets of experiments. However, stu-dies on the combined effects of ambient temperature and diet energy level are limited. The objective of the present study was to determine whether different energy level or different ambient temperature for Holstein steers would result in T3 and T4 and some blood para-meters.
Effects of different energy levels and ambient
temperatures on serum thyroid hormones and some
biochemical values in Holstein steers
TALAT GÜLER, SELÝM KUL*, O. NÝHAT ERTAÞDepartment of Animal Nutrition, *Department of Zootechnia, Veterinary Faculty, University of Fýrat, TR- 23119 Elazýð, Turkey
Güler T., Kul S., Ertaþ O. N.
Effects of various energy levels and ambient temperatures on serum thyroid hormones and some biochemical values in Holstein steers
Summary
This 2x2 factorial study was designed to test the effects of different diet energy levels (Low: 5.39 NEf MJ/kg and High: 6.60 NEf MJ/kg) and environmental temperature (Low: 19.84°C and High: 28.5°C) on triiodo-thyronine (T3), thyroxine (T4) and blood serum parameters of Holstein steers. A total of 28 10-month old steers were divided into 4 groups, each containing 7 steers. According to this design, steers which were subjected to housing in barns were either offered normal energy (Barn-NE group) or high energy (Barn-HE group) diets; steers which were subjected to housing outside were also either offered normal energy (Outside-NE group) or high energy (Outside-HE group) diets. The highest levels of T3 and T4 were in the Outside-HE group followed
by Outside-NE group, Barn-HE group and Barn-NE group, respectively (p<0.05). Serum glucose, cholesterol and triglyceride levels were higher in all the outside groups (p<0.05). No differences were found between the groups in the total protein, albumin, uric acid, inorganic phosphor, Ca, Na and K levels. The levels of SCOT, SGPT, amylase, alkaline phosphates and creatinin were similar in all groups. The results of the study indi-cated that increasing energy levels and ambient temperatures increased T3 and T4 levels and did not affect serum metabolites except for glucose, cholesterol and triglyceride.
Medycyna Wet. 2006, 62 (1) 37
Material and methods
Animals. Ten months old Holstein steers were obtained from an official farm (Ceylanpýnar Agri-cultural Administration). A total of 28 of 10 month--old steers were divided into 4 groups, each con-taining 7 steers.
Dietary treatments. Levels of energy of diets were the basis for the experimental rations. Ac-cordingly, two diets were used. One of them had normal energy (Diet NE) and the other had high energy (Diet HE). Rations were prepared isinitro-genous. The ingredient and chemical composition of the diets are presented in Table 1.
Experimental design. A 2 × 2 factorial design was used. Factors consisted of two different housing methods (in barn and outside) and two different diets with different energy levels (nor-mal and high energy density). Each of four groups included 7 Holstein steers (average 200 kg BW). According to this design, steers which were sub-jected to the housing in the barn were either offe-red normal energy (NE group) or high energy (HE group) diets. Steers which were subjected to housing at the outside were either offered normal energy (NE group) or high energy (HE group) diets. At the beginning of the experiment the steers were weighed and divided four groups and groups were balanced according to BW. The expe-riment was carried out in hot season (July-Octo-ber) and 112 day. Feeds and water were offered ad libitum to all groups. The animals were fed twice daily, at 08.00 and 18.00 hours. During the
experimental period, ambient temperatures of the barn and the outside were measured daily (Tab. 2). No antibiotics and vitamins were applied to the steers except standard rations during the experi-ment period.
Growth performance. Feed intake was determined daily. For that purpose, each day, feed was weighed and offered ad libitum and following morning refused feed was deduced. Body weight gain, following pre-experimental period, steers fasted overnight were weighed and starting body weight was determined. Weighing was carried out 14 day thro-ughout the study and daily BW gain was calculated by divi-ding it by 14. Feed efficiency ratio was calculated by dividivi-ding daily feed consumption to daily BW gain at the end of the 112 day.
Sample collection and laboratory analysis. Feed ingre-dients of nutrients were analyzed using A.O.A.C. (5) proce-dures and crude fiber was determined as described by Cramp-ton and Maynard (10).
Blood samples were taken from vena jugularis at 56th and
112th days and two h after feeding. Blood samples were
cen-trifuged at 3000 × g for 10 min. and serum collected and sto-red at 20°C for later analyses. Sera were thawed at room temperature and T3 and T4 concentrations were determined using commercially available radioimmunoassay kits (Diagno-stic Products Crop., Los Angeles, CA). Intra and intraassay
coefficients of variation were 6.11 and 8.21% for T3 and 12.20
and 7.97% for T4, respectively. Serum biochemical parame-ters were measured using auto analyzer (Technicon RA-XT, Technicon Instrument Corporation,Tarrytown, NY).
Statistical analysis. Data collected were subjected to ana-lysis of variance, and where significant differences were ob-served, means were further subjected to Duncans multiple range test, SPSS (30) for Windows: 10.1, SPSS inc., (1999). The results were considered as significant when p values were less than 0.05.
Results and discussion
The effects of ambient temperature and diet energy level on feed intake, live weight change and feed con-version ratio are shown in Tab. 3. Low ambient tem-perature and low diet energy level increased feed in-take (p < 0.05) and had no significant effect on live s d e e F 200-250kg 250-300kg 300-350kg E N HE NE HE NE HE % , w a rt s y e lr a B 20.00 20.00 20.00 20.00 20.00 20.00 % , e t a rt n e c n o C 80.00 80.00 80.00 80.00 80.00 80.00 e t a rt n e c n o c f o n o it i s o p m o C % , y e lr a B 36.79 79.62 40.61 83.44 43.79 86.62 % ,l a e m n a e b y o S 10.75 15.40 16.93 11.58 13.75 18.40 % , n a r b t a e h W 48.66 48.66 48.66 O C H a N 3 11.00 11.20 11.00 11.20 11.00 11.20 % , e n o t s e m i L 12.00 10.68 12.00 10.68 12.00 10.68 % , e t a h p s o h p m u i c l a c i D 12.30 12.30 12.30 % ,t l a S 10.50 10.50 10.50 10.50 10.50 10.50 % , * x i m e r P .t i V 10.15 10.15 10.15 10.15 10.15 10.15 % , * * x i m e r P . n i m e c a r T 10.15 10.15 10.15 10.15 10.15 10.15 s i s y l a n A % ,r e tt a m y r D 90.00 90.00 90.00 90.00 90.00 90.00 P C D +,g/kg 109.391 109.411 99.44 99.46 91.14 91.14 f E N ++,MJ/kg 15.39 16.60 15.39 16.60 15.39 16.60 Tab. 1. Composition of rations
Explanations: * per kg include; 1.200.000 IU vit A, 200.000 IU vit D3,
5.000 mg vit E, 100 mg vit K3, 100 mg vit B1, 50 mg vit B2, 10 mg vit B6,
500 mg Niacin, 300 mg Cal-D-Pentotenat and 100 mg vit C. ** per kg inclu-de; 5.000 mg Fe, 5.000 mg Zn, 1.000 mg Cu, 200 mg I, 50 mg Co, 30 mg Se, 54.000 mg P, 319.000 mg Ca, 100.000 mg NaCl and 15.000 mg Antioksidan.
++ Net energy fat (Founded by calculated). +DCP Digestibility crude protein
°C e d i s t u O 19.8 n r a B 28.5
Tab. 2. Average daily ambient temperature in outside and barn during the experimental period m e tI Outside Barn SEM P E N HE NE HE d / g , e k a t n i d e e F 9102a 8680b 8790ab 8642b 0.58 * g , n i a g W B y li a D 1060 1049 1054 1047 1.24 NS o it a r n i a g : d e e F 8.58 8.27 8.34 8.25 0.88 NS Tab. 3. The effect of ambient temperature and diet energy level on the performance in Holstein steers, (n = 7)
Explanations: NS non significant; * P < 0.05; a, b mean values with different superscripts within a row differ significantly
Medycyna Wet. 2006, 62 (1) 38
weight gain and feed conversion ratio. The highest feed intake was in Outside-NE group, this was followed by Barn-NE group, Outside-HE group and Barn-HE group, respectively. The reason of different feed intake in groups might be due to the prevention of combined effects of both high ambient temperature and the heat produced as a result of feed consumption. Because, high ambient temperature and high nutrient density of ration are decreasing factors of feed intake.
The highest level of serum T3 and T4 were in Out-side-HE group, this was followed by Outside-NE group, Barn-HE group and Barn-NE group, respecti-vely (p < 0.05) (Tab. 4). As shown, the high energy diets were increased serum T3 and T4 concentrations. The thyroid hormones concentrations can be regula-ted by diet composition and energy level. The amount and composition of energy supplied in an important nutritional regulating factor in the activation of the de-iodinase enzyme responsible for the peripheral conver-sion of T4 to T3. Pethes et al. (24), observed an decre-ase in T3 concentrations in preparturient cows fed 20%
less energy, suggesting reduced maintenance require-ments could be associated with lower energy intakes. Refsal et al. (26) reported that the concentrations of T3 and T4 were related positively with energy balance sta-tus. In addition, Powell et al. (25) reported that
redu-ced T3 concentrations and a slower metabolic rate
would be expected with energy restriction. Besides, serum thyroid hormones concentrations had been af-fected from glucose level. Because, glucose is an im-portant stimulus for increasing peripheral conversion of T4 to T3 (11). Saymonds et al. (29) reported that T3 concentration was increased to be parallel the incre-asing of glucose production. Additionally, the amount of soluble carbohydrate in the diet is an important de-terminant of peripheral T3 concentrations. Glade and Luba (13) reported that thyroid hormones concentra-tion increased due to the addiconcentra-tion of carbohydrate. Yambayamba et al. (32) found that beef heifers fed a restricted diet had lower T3 concentrations and a slo-wer metabolic rate than heifers given ad libitum access to feed. The results of the present study are in agree-ment with results previous studies (3, 12, 17, 23, 32). Conversely, Rosebrough (28) reported that ration ener-gy levels did not significantly alter thyroid hormones levels. Similarly, there is a near relationship between thyroid hormones and ambient temperature. T3 and T4 concentrations were increased by low ambient tempe-rature (Tab. 3). As known, in cold ambient temperatu-re, neural impulses come to the thermo receptor in skin stimulates center of heat arrangement in the hypotha-lamus and thyrotropin-releasing-hormone (TRH) syn-theses in the hypothalamus. TRH is trans-ferred to the front pituitary gland via portal vena, and increase of thyrotropin secretion. Thyrotropine causes T3 and T4 synthesis in the thyroid gland. For this reason, thyroid hormones levels increases and body tempe-rature is balanced. Conversely, in high am-bient temperature, the synthesis of TRH and thyroid hormones are reduced. Thyroid size and thyroid secretion rate were decreased by high temperatures and increased by low tem-peratures. During heat stress T3 was depres-sed, apparently because of decreased ener-gy metabolism and nutrient digestibility. These results were in agreement with pre-vious studies (20, 21, 34). Studies have sug-gested that thyroid activity is affected by the ambient temperature (7, 21). Marai et al. (19) reported that serum concentration of T3 de-creased in summer compared to winter con-ditions.
Data for serum constituents values are presented in Tab. 5. Serum glucose, chole-sterol and triglyceride levels were higher in Outside groups (p < 0.05). No differences were found in total protein, albumin, uric acid, inorganic phosphor, Ca, Na and K le-m e tI Outside Barn SEM P E N HE NE HE T3 98.17b 107.83a 91.00c 96.50b 0.07 * T4 18.31b 108.92a 17.30c 17.95b 0.08 * Tab. 4. The effect of ambient temperature and diet energy level on the levels of T3 and T4 in Holstein steers, (ng/ml) (n = 7)
Explanations: * P < 0.05, a, b, c mean values with different
superscripts within a row differ significantly
m e tI Outside Barn SEM P E N HE NE HE l/ M m , e s o c u l G 178.00a 182.50a 68.50b 170.17b 0.47 * l/ M m ,l o r e t s e l o h C 108.50b 125.67a 98.00b 101.33b 1.64 * l/ M m , e d ir e c y l g ir T 121.53a 123.33a 118.50b 118.83b 2.14 * l d / g , n i e t o r P . T 128.33 128.37 128.08 128.10 0.47 NS l d / g m , n i m u b l A 123.83 123.97 123.80 123.75 0.19 NS l d / g m , d i c a c ir U 120.88 120.90 120.87 120.83 1.04 NS l d / g m ,r o f s o h P .I 127.60 127.48 127.15 127.25 2.10 NS l d / g m , a C 129.33 129.37 128.93 128.73 1.22 NS L / q E m , a N 149.42 150.20 148.60 147.65 2.01 NS L / q E m , K 127.90 128.64 128.46 127.93 0.89 NS L / U , T O G S 182.67 184.67 183.83 184.00 2.14 NS L / U , T P G S 120.03 119.17 119.33 118.83 1.88 NS L / U , e s a l y m A 2067.331 2056.001 2069.001 2048.831 3.45 NS L / U , e s a t a f s o h P . A 158.67 160.33 156.50 160.67 0.96 NS l d / g m , n i n it a e r C 111.60 111.53 111.58 111.53 1.44 NS Tab. 5. The effect of ambient temperature and diet energy level on the blood parameters in Holstein steers, (n 7)
Explanations: NS non significant; * P < 0.05; a.b mean values with
Medycyna Wet. 2006, 62 (1) 39
vels in groups. There was no significant change in the enzyme activity. SGOT, SGPT, amylase, alkaline phos-phates and creatinine levels were similar in all groups. The reason of differences in serum metabolites may be due to the effect of heat stress and energy level. High energy level was increased glucose, cholesterol and triglyceride levels both Outside and Barn groups. On the contrary, high ambient temperature was decre-ased glucose, cholesterol and triglyceride levels. In addition, the serum metabolites in the current study were within normal range in all groups (4). The effect of heat stress on serum metabolites determined in the current study was similar to previous reported values (9, 22, 27). Ronchi et al. (27) reported that heat stress led to reduced blood glucose, cholesterol, SGOT and SGPT. Marai et al. (19) have shown that serum con-centrations of glucose, total protein, creatinine, total lipid and total cholesterol decreased in summer as com-pared with winter conditions. Glade and Luba (13) re-ported that glucose concentration increased due to the addition of carbohydrate. These results are in agree-ment with our study. Also, there was a close relation-ship between thyroid hormones and blood parameters. Thyroid hormones affected many stages of carbohy-drate metabolism, and increased blood glucose level due to increased glucose usage by tissues, and incre-ased gylucogenessis in hart, liver and skeletal muscle (35). Even so, many studies reported that, blood glu-cose level was decreased in thyroid hormones defi-ciency (6, 16). In addition, Abrams et al. (1) reported that cholesterol level was increased due to increasing of thyroid hormones level.
In conclusion, the result of the present study indica-ted that the increasing of energy level increased serum T3 and T4 levels, and the increasing of ambient tempe-rature decreased serum T3 and T4 levels in Holstein steers. While serum glucose and triglyceride levels were not affected by the increasing of energy level, serum cholesterol level increased with the increasing of energy level and the level of these parameters redu-ced in high ambient temperature. Both diet energy le-vel and ambient temperature did not affect the other investigated serum metabolites.
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Authors address: Dr. Talat Güler, Department of Animal Nutrition, Veterinary Faculty, University of Firat, TR-23119 Elazig, Turkey; e-mail: Tguler@firat.edu.tr, talatguler@yahoo.com
