Directory UMM :Data Elmu:jurnal:A:Animal Feed Science and Technology:Vol86.Issue1-2.Jul2000:
Animal Feed Science and Technology
86 (2000) 95±105
Ef®cacy of chromium-yeast supplementation
for growing beef steers$
K.C. Swansona, D.L. Harmona,*, K.A. Jacquesb, B.T. Larsona,
C.J. Richardsa,1, D.W. Bohnerta,2, S.J. Patona
a
Department of Animal Sciences, University of Kentucky, Lexington, KY 40546-0215, USA
b
Alltech Inc., Nicholasville, KY 40356, USA
Received 17 September 1999; received in revised form 7 March 2000; accepted 21 March 2000
Abstract
This experiment was conducted to determine the ef®cacy of feeding chromium yeast to growing
beef steers. Animal growth, gain ef®ciency, and blood glucose kinetics were determined in 24 beef
steers (initial body weight253 4 kg) fed a corn silage-based diet supplemented with 0 (control),
100, 200, or 400 mg chromium from high-chromium yeast/kg of diet dry matter. Intravenous
glucose tolerance tests (IVGTT) and intravenous insulin challenge tests (IVICT) were conducted at
3 and 6 weeks of chromium-yeast supplementation. There were minimal effects on plasma glucose
kinetics during IVGTT and IVICT. There were tendencies for glucose clearance rate to increase
(p0.16) and half-life to decrease (p0.14) during IVICT. However, chromium-yeast supplementation had no effect (p>0.24) on ADG and gain ef®ciency, suggesting that chromium-yeast
supplementation to unstressed growing calves may not be bene®cial. # 2000 Elsevier Science B.V.
All rights reserved.
Keywords: Beef cattle; Chromium; Glucose tolerance; Growth
1. Introduction
Chromium has been implicated as an essential nutrient for humans and lab animals
(Mertz, 1993). Chromium increases glucose tolerance by potentiating the action of
$
Approved by the Director of the Kentucky Agricultural Experimental Station as publication 99-07-106.
Corresponding author. Tel.: 1-859-257-7516; fax: 1-859-257-3412.
E-mail address: dharmon@ca.uky.edu (D.L. Harmon)
1
Present address: University of Tennessee, P.O. Box 1071, Knoxville, TN 37901-1071.
2
Present address: Eastern Oregon Agricultural Research Center, Oregon State University, Burns Station, HC
71, 4.51 Highway 205, Burns, OR 97720-9399.
*
0377-8401/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 0 0 ) 0 0 1 4 2 - 5
96
K.C. Swanson et al. / Animal Feed Science and Technology 86 (2000) 95±105
insulin in clearing postprandial glucose from the blood (Mertz, 1993). This could lead to
improved glucose utilization and increased growth and ef®ciency. However, inorganic
forms of chromium are relatively unavailable for absorption (Mordenti et al., 1997).
Organic forms of chromium, such as high-chromium yeast, are usually more available for
absorption (Mordenti et al., 1997). High-chromium yeast has been grown in the presence
of high chromium concentrations. Yeast has the ability to accumulate ions, such as
chromium, in high concentrations (Ingledew, 1999) and, therefore, can be useful as a
source of supplemental minerals. Research with ruminants has suggested that organic
chromium supplementation may have the greatest in¯uence on stressed animals (Chang
and Mowat, 1992; Moonsie-Shageer and Mowat, 1993; Burton, 1995; Kegley and Spears,
1995). Research regarding the biological effects of organic chromium supplementation on
non-stressed ruminants have been variable (Chang and Mowat, 1992; Bunting et al.,
1994; Kitchalong et al., 1995; Gentry et al., 1999) and different levels of supplementation
have rarely been examined (Moonsie-Shageer and Mowat, 1993). Therefore, our
objectives were to examine the in¯uence of increasing amounts of chromium yeast
supplementation to non-stressed growing beef steers on (1) growth and gain ef®ciency,
and (2) blood glucose kinetics during intravenous glucose tolerance and intravenous
insulin challenge tests.
2. Materials and methods
Thirty steers were purchased from public auction through a local order buyer. They
were predominantly British crosses with little or no Charolais or Brahman in¯uence.
Upon receiving, steers were vaccinated (IBR and PI3) and treated for external and internal
parasites (Ivomec1). Rectal temperatures were checked and any exceeding 408C were
treated with Tilmicosin and re-examined after 2 days. Steers were fed hay and a
medicated receiving diet until adjusted to their new environment and outbreaks of
respiratory disease and/or shipping fever had passed. Steers were trained to tie by halter
and were accustomed to handling. This enabled collection of blood samples without the
animals being overly excited. Based on temperament and ease of handling, 24 of the 30
steers were selected for use in the experiment. The time interval between arrival and the
initiation of the experiment was 30 days.
Experimental steers (initial body weight2534 kg) were fed individually twice daily
(0800 and 1600) a diet containing 90% corn silage and 10% soybean meal-based
supplement (dry matter basis; Table 1) at 2.2% body weight/day (DM basis) and were
housed in concrete-¯oored pens in an open-sided barn. The diet was selected because
corn silage diets are commonly fed to growing cattle in Kentucky. Steers were limit-fed at
2.2% of body weight so that differences in intake would not confound the results obtained
due to chromium-yeast supplementation. Steers were supplemented with 0 (control), 100,
200, or 400 mg Cr from chromium-yeast/kg of diet dry matter (Alltech, Nicholasville,
KY). Chromium yeast was mixed with the soybean meal supplement and top-dressed at
the 0800 feeding. Steers would rapidly and completely consume the supplement. Feed
samples were collected and analyzed weekly for DM (558C for 48 h) and as-fed dietary
intakes were adjusted accordingly so that dry matter intake was 2.2% of body weight
K.C. Swanson et al. / Animal Feed Science and Technology 86 (2000) 95±105
97
Table 1
Components and composition of basal dieta
Diet components
Ingredient
Diet dry matter (%)
Corn silage
Soybean meal
Fine ground corn
Urea
Choice white grease
Vitamin A, D, & E premixb
Trace mineral salt with Sec
Dicalcium phosphate
Limestone
90.0
7.61
0.57
0.23
0.11
0.02
0.27
0.47
0.72
Diet composition
Item
Diet dry matter (%)
Ash
Crude protein
NDF
ADF
6.0
12.5
42.3
21.4
a
Diet contained 0 (control), 100, 200, or 400 mg Cr/kg diet dry matter from chromium yeast.
8800 IU/g vitamin A, 1760 IU/g vitamin D, and 1.1 IU/g vitamin E.
c
98.5% NaCl, 0.35% Zn, 0.34% Fe, 0.20% Mn, 330 ppm Cu, 70 ppm I, 50 ppm Co, and 90 ppm Se.
b
throughout the experiment. Steers consumed all of the feed offered. Body weights were
taken prior to assignment to experimental treatment before the 0800 feeding. Three days
prior to assignment to treatment, steers were placed in individual pens and fed a corn
silage-based diet at equal intakes to minimize the effects of intake on ruminal ®ll. Body
weights also were taken at 3 and 6 weeks of chromium-yeast supplementation prior to the
0800 feeding. Average daily gain (ADG) and gain ef®ciency for the 6-week feeding
period were calculated for each steer.
Intravenous glucose tolerance tests (IVGTT) and intravenous insulin challenge tests
(IVICT) were conducted at 3 and 6 weeks of chromium-yeast supplementation at 0800
and 1300, respectively. Procedures were similar to those described by Bunting et al.
(1994) and Kitchalong et al. (1995). Tests were done on two consecutive days with half of
the steers from each treatment tested each day.
Steers were ®tted with sterile indwelling jugular catheters the day prior to IVGTT and
IVICT. At 3 weeks of chromium supplementation, a 14-gage thin-wall needle was
inserted into the jugular vein and a 30-cm piece of 18-gage thin-wall Te¯on tubing
introduced into the jugular vein through the needle. The needle was removed and a 19gage luer-lock tubing adapter with a 50-cm extension was attached. The catheter was
sutured to the skin. The catheter was ¯ushed with 100 U/ml heparin in saline, capped, and
the steers' necks wrapped with elastic tape to secure catheters. Due to problems with the
catheters becoming non-functional and the dif®culty of infusing large volumes rapidly,
larger catheters (Abocath-T, 14-gage14 cm; Butler; Columbus, OH) were used for the
collection after 6 weeks of supplementation. A 38-cm extension was connected to the
98
K.C. Swanson et al. / Animal Feed Science and Technology 86 (2000) 95±105
catheter and the catheter was sutured to the skin. Catheters were then ¯ushed with 100 U/
ml heparin in saline, capped, and the steers' necks wrapped with elastic tape. The IVGTT
and IVICT were initiated after an overnight fast by intravenously dosing each steer via the
jugular catheter with glucose (0.5 g/kg BW as a 50% solution) or insulin (0.1 unit/kg as a
1.3 U/ml solution containing, respectively, 0.2% BSA and 0.9% NaCl; Sigma, St. Louis,
MO). Glucose and insulin solutions were ®ltered through 0.45 and 0.2 mm membranes,
respectively, into sterile bottles prior to intravenous administration. Blood samples
(10 ml) were collected using a heparinized syringe at ÿ10, 0, 5, 10, 15, 20, 25, 30, 45, 90,
120, 150, and 180 min relative to dosing. Blood was transferred to a tube containing
sodium ¯uoride (20 mg), mixed by inversion, and placed on ice. Catheters were ¯ushed
with 20 U/ml heparin in saline after each collection time. Plasma was harvested by
centrifugation (2500g, 48C, 15 min) and stored at ÿ308C until analyzed for glucose
using the hexokinase method (Slein, 1963; Sigma Procedure 16-UV) with modi®cations
for use on a Cobas Fara II (Roche Diagnostic Systems, Montclair, NJ). Blood glucose
clearance rate (k) and half-life (T1/2) were calculated according to Kaneko (1989), using
the following equations: k (%/min){(ln [glucosetime1]ÿln [glucosetime2])/(time2ÿtime1)}100 and T1/2 (min)(0.693/k)100. For the IVGTT, k and T1/2 were
calculated using the interval from 15 to 45 min. For the IVICT, k and T1/2 were calculated
using the interval from 0 to 30 min. The time points used for the calculation of k and T1/2
during the IVGTT and IVICT were selected because they were in a linear range of
glucose clearance and also because similar time points have been used previously
(Kitchalong et al., 1995). The area under the curve and that above the curve from 0 to
180 min for the IVGTT and IVICT, respectively, were calculated using trigonometric
geometry (Swokowski, 1988). Calculations of areas under, and above, the curve were
calculated relative to basal levels (i.e. Time 0 values were subtracted from others).
Data were analyzed using GLM procedures of SAS (1988). The IVGTT and IVICT
data were analyzed as a completely randomized design within period. The IVGTT and
IVICT were also subjected to split-plot analysis testing the effects of treatment, animal
within treatment, period, and treatment by period using animal within treatment as the
error term. Growth data were analyzed as a completely randomized design. Contrast
statements were used to compare treatments for linear and quadratic effects due to
chromium-yeast supplementation using the appropriate coef®cients for unequal spacing
of treatments. Contrasts with p
86 (2000) 95±105
Ef®cacy of chromium-yeast supplementation
for growing beef steers$
K.C. Swansona, D.L. Harmona,*, K.A. Jacquesb, B.T. Larsona,
C.J. Richardsa,1, D.W. Bohnerta,2, S.J. Patona
a
Department of Animal Sciences, University of Kentucky, Lexington, KY 40546-0215, USA
b
Alltech Inc., Nicholasville, KY 40356, USA
Received 17 September 1999; received in revised form 7 March 2000; accepted 21 March 2000
Abstract
This experiment was conducted to determine the ef®cacy of feeding chromium yeast to growing
beef steers. Animal growth, gain ef®ciency, and blood glucose kinetics were determined in 24 beef
steers (initial body weight253 4 kg) fed a corn silage-based diet supplemented with 0 (control),
100, 200, or 400 mg chromium from high-chromium yeast/kg of diet dry matter. Intravenous
glucose tolerance tests (IVGTT) and intravenous insulin challenge tests (IVICT) were conducted at
3 and 6 weeks of chromium-yeast supplementation. There were minimal effects on plasma glucose
kinetics during IVGTT and IVICT. There were tendencies for glucose clearance rate to increase
(p0.16) and half-life to decrease (p0.14) during IVICT. However, chromium-yeast supplementation had no effect (p>0.24) on ADG and gain ef®ciency, suggesting that chromium-yeast
supplementation to unstressed growing calves may not be bene®cial. # 2000 Elsevier Science B.V.
All rights reserved.
Keywords: Beef cattle; Chromium; Glucose tolerance; Growth
1. Introduction
Chromium has been implicated as an essential nutrient for humans and lab animals
(Mertz, 1993). Chromium increases glucose tolerance by potentiating the action of
$
Approved by the Director of the Kentucky Agricultural Experimental Station as publication 99-07-106.
Corresponding author. Tel.: 1-859-257-7516; fax: 1-859-257-3412.
E-mail address: dharmon@ca.uky.edu (D.L. Harmon)
1
Present address: University of Tennessee, P.O. Box 1071, Knoxville, TN 37901-1071.
2
Present address: Eastern Oregon Agricultural Research Center, Oregon State University, Burns Station, HC
71, 4.51 Highway 205, Burns, OR 97720-9399.
*
0377-8401/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 0 0 ) 0 0 1 4 2 - 5
96
K.C. Swanson et al. / Animal Feed Science and Technology 86 (2000) 95±105
insulin in clearing postprandial glucose from the blood (Mertz, 1993). This could lead to
improved glucose utilization and increased growth and ef®ciency. However, inorganic
forms of chromium are relatively unavailable for absorption (Mordenti et al., 1997).
Organic forms of chromium, such as high-chromium yeast, are usually more available for
absorption (Mordenti et al., 1997). High-chromium yeast has been grown in the presence
of high chromium concentrations. Yeast has the ability to accumulate ions, such as
chromium, in high concentrations (Ingledew, 1999) and, therefore, can be useful as a
source of supplemental minerals. Research with ruminants has suggested that organic
chromium supplementation may have the greatest in¯uence on stressed animals (Chang
and Mowat, 1992; Moonsie-Shageer and Mowat, 1993; Burton, 1995; Kegley and Spears,
1995). Research regarding the biological effects of organic chromium supplementation on
non-stressed ruminants have been variable (Chang and Mowat, 1992; Bunting et al.,
1994; Kitchalong et al., 1995; Gentry et al., 1999) and different levels of supplementation
have rarely been examined (Moonsie-Shageer and Mowat, 1993). Therefore, our
objectives were to examine the in¯uence of increasing amounts of chromium yeast
supplementation to non-stressed growing beef steers on (1) growth and gain ef®ciency,
and (2) blood glucose kinetics during intravenous glucose tolerance and intravenous
insulin challenge tests.
2. Materials and methods
Thirty steers were purchased from public auction through a local order buyer. They
were predominantly British crosses with little or no Charolais or Brahman in¯uence.
Upon receiving, steers were vaccinated (IBR and PI3) and treated for external and internal
parasites (Ivomec1). Rectal temperatures were checked and any exceeding 408C were
treated with Tilmicosin and re-examined after 2 days. Steers were fed hay and a
medicated receiving diet until adjusted to their new environment and outbreaks of
respiratory disease and/or shipping fever had passed. Steers were trained to tie by halter
and were accustomed to handling. This enabled collection of blood samples without the
animals being overly excited. Based on temperament and ease of handling, 24 of the 30
steers were selected for use in the experiment. The time interval between arrival and the
initiation of the experiment was 30 days.
Experimental steers (initial body weight2534 kg) were fed individually twice daily
(0800 and 1600) a diet containing 90% corn silage and 10% soybean meal-based
supplement (dry matter basis; Table 1) at 2.2% body weight/day (DM basis) and were
housed in concrete-¯oored pens in an open-sided barn. The diet was selected because
corn silage diets are commonly fed to growing cattle in Kentucky. Steers were limit-fed at
2.2% of body weight so that differences in intake would not confound the results obtained
due to chromium-yeast supplementation. Steers were supplemented with 0 (control), 100,
200, or 400 mg Cr from chromium-yeast/kg of diet dry matter (Alltech, Nicholasville,
KY). Chromium yeast was mixed with the soybean meal supplement and top-dressed at
the 0800 feeding. Steers would rapidly and completely consume the supplement. Feed
samples were collected and analyzed weekly for DM (558C for 48 h) and as-fed dietary
intakes were adjusted accordingly so that dry matter intake was 2.2% of body weight
K.C. Swanson et al. / Animal Feed Science and Technology 86 (2000) 95±105
97
Table 1
Components and composition of basal dieta
Diet components
Ingredient
Diet dry matter (%)
Corn silage
Soybean meal
Fine ground corn
Urea
Choice white grease
Vitamin A, D, & E premixb
Trace mineral salt with Sec
Dicalcium phosphate
Limestone
90.0
7.61
0.57
0.23
0.11
0.02
0.27
0.47
0.72
Diet composition
Item
Diet dry matter (%)
Ash
Crude protein
NDF
ADF
6.0
12.5
42.3
21.4
a
Diet contained 0 (control), 100, 200, or 400 mg Cr/kg diet dry matter from chromium yeast.
8800 IU/g vitamin A, 1760 IU/g vitamin D, and 1.1 IU/g vitamin E.
c
98.5% NaCl, 0.35% Zn, 0.34% Fe, 0.20% Mn, 330 ppm Cu, 70 ppm I, 50 ppm Co, and 90 ppm Se.
b
throughout the experiment. Steers consumed all of the feed offered. Body weights were
taken prior to assignment to experimental treatment before the 0800 feeding. Three days
prior to assignment to treatment, steers were placed in individual pens and fed a corn
silage-based diet at equal intakes to minimize the effects of intake on ruminal ®ll. Body
weights also were taken at 3 and 6 weeks of chromium-yeast supplementation prior to the
0800 feeding. Average daily gain (ADG) and gain ef®ciency for the 6-week feeding
period were calculated for each steer.
Intravenous glucose tolerance tests (IVGTT) and intravenous insulin challenge tests
(IVICT) were conducted at 3 and 6 weeks of chromium-yeast supplementation at 0800
and 1300, respectively. Procedures were similar to those described by Bunting et al.
(1994) and Kitchalong et al. (1995). Tests were done on two consecutive days with half of
the steers from each treatment tested each day.
Steers were ®tted with sterile indwelling jugular catheters the day prior to IVGTT and
IVICT. At 3 weeks of chromium supplementation, a 14-gage thin-wall needle was
inserted into the jugular vein and a 30-cm piece of 18-gage thin-wall Te¯on tubing
introduced into the jugular vein through the needle. The needle was removed and a 19gage luer-lock tubing adapter with a 50-cm extension was attached. The catheter was
sutured to the skin. The catheter was ¯ushed with 100 U/ml heparin in saline, capped, and
the steers' necks wrapped with elastic tape to secure catheters. Due to problems with the
catheters becoming non-functional and the dif®culty of infusing large volumes rapidly,
larger catheters (Abocath-T, 14-gage14 cm; Butler; Columbus, OH) were used for the
collection after 6 weeks of supplementation. A 38-cm extension was connected to the
98
K.C. Swanson et al. / Animal Feed Science and Technology 86 (2000) 95±105
catheter and the catheter was sutured to the skin. Catheters were then ¯ushed with 100 U/
ml heparin in saline, capped, and the steers' necks wrapped with elastic tape. The IVGTT
and IVICT were initiated after an overnight fast by intravenously dosing each steer via the
jugular catheter with glucose (0.5 g/kg BW as a 50% solution) or insulin (0.1 unit/kg as a
1.3 U/ml solution containing, respectively, 0.2% BSA and 0.9% NaCl; Sigma, St. Louis,
MO). Glucose and insulin solutions were ®ltered through 0.45 and 0.2 mm membranes,
respectively, into sterile bottles prior to intravenous administration. Blood samples
(10 ml) were collected using a heparinized syringe at ÿ10, 0, 5, 10, 15, 20, 25, 30, 45, 90,
120, 150, and 180 min relative to dosing. Blood was transferred to a tube containing
sodium ¯uoride (20 mg), mixed by inversion, and placed on ice. Catheters were ¯ushed
with 20 U/ml heparin in saline after each collection time. Plasma was harvested by
centrifugation (2500g, 48C, 15 min) and stored at ÿ308C until analyzed for glucose
using the hexokinase method (Slein, 1963; Sigma Procedure 16-UV) with modi®cations
for use on a Cobas Fara II (Roche Diagnostic Systems, Montclair, NJ). Blood glucose
clearance rate (k) and half-life (T1/2) were calculated according to Kaneko (1989), using
the following equations: k (%/min){(ln [glucosetime1]ÿln [glucosetime2])/(time2ÿtime1)}100 and T1/2 (min)(0.693/k)100. For the IVGTT, k and T1/2 were
calculated using the interval from 15 to 45 min. For the IVICT, k and T1/2 were calculated
using the interval from 0 to 30 min. The time points used for the calculation of k and T1/2
during the IVGTT and IVICT were selected because they were in a linear range of
glucose clearance and also because similar time points have been used previously
(Kitchalong et al., 1995). The area under the curve and that above the curve from 0 to
180 min for the IVGTT and IVICT, respectively, were calculated using trigonometric
geometry (Swokowski, 1988). Calculations of areas under, and above, the curve were
calculated relative to basal levels (i.e. Time 0 values were subtracted from others).
Data were analyzed using GLM procedures of SAS (1988). The IVGTT and IVICT
data were analyzed as a completely randomized design within period. The IVGTT and
IVICT were also subjected to split-plot analysis testing the effects of treatment, animal
within treatment, period, and treatment by period using animal within treatment as the
error term. Growth data were analyzed as a completely randomized design. Contrast
statements were used to compare treatments for linear and quadratic effects due to
chromium-yeast supplementation using the appropriate coef®cients for unequal spacing
of treatments. Contrasts with p