MINERAL METABOLISM IN STEERS IMPLANTED WITH RALGRO® OR SYNOVEX-S®

 

Authors: T.Craig, L.W.Greene, F.M.Byers and G.T.Schelling

 

SUMMARY

Sixty-four crossbred steers, large and small frame size, were assigned to a control, Ralgro® or Synovex® implant treatment group. Implanted animals were reimplanted at 90 day intervals.  Large frame cattle were either Charolais sired or Chianina sired steers.  Small frame cattle were genetically distinct from large frame cattle and were sired by either Red Poll, Hereford X (Angus-Hereford) or Angus X Brahman.   Steers were fed, ad libitum, a high grain finishing diet based on either ground sorghum or whole shelled corn.  Serum samples were obtained 28 days post-implant via jugular vein venipuncture.  Serum calcium and magnesium concentrations were not different (P>0.10) between implant groups or frame size.  When summarized by main effects, there were no differences between treatment groups or frame size for serum iron concentrations.  Serum iron concentrations were lower during the second bleeding which occurred 118 days after the initiation of the experiment.  This could be a reflection of liver iron depletion.  There was a 19.7% decrease in the large framed steers when implanted with Synovex-S® compared to those not receiving an implant, with those implanted with Ralgro® being intermediate.  However, serum iron concentrations increased (P>0.05) 39.6% in steers of the small frame group when implanted with Synovex-S® compared to the control cattle, with those implanted with Ralgro® being intermediate.  At 28 days after the first implant, serum zinc concentrations decreased from 88.6 to 79.4µg/dl when cattle were implanted with Synovex-S®, with those cattle implanted with Ralgro® being intermediate, 83.4 µg/dl.  A significant interaction between frame size and implant treatment group occurred during the first bleeding date.  Large frame steers implanted with Synovex-S® and Ralgro® had a 12.1 and 9.3% decrease in serum zinc concentrations, respectively, and small frame steers implanted with Ralgro® had a 9.6% increase in serum zinc concentrations compared to the control steers.  Although bleeding 2 did not indicate a significant main effect for serum zinc levels, there was a significant implant by frame interaction.  Large frame controls had significantly greater serum zinc values than either Ralgro® or Synovex® implanted steers.

 

INTRODUCTION

Human research studies involving estrogenic and progesterone based oral contraceptives indicated that changes occur in mineral metabolism.  However, other research has not indicated a change in the propensity towards mineral deposition in skeletal growth with the growth promotants diethylstilbestrol and Synovex-S®.  A mild hypomagnesemia has been reported with the use of oral contraceptives.  Estrogen mediated reduction in serum or plasma zinc has also been found, while progesterone containing compounds, such as those found in the “mini-pill”, did not cause this affect.  Additionally, significant increases in serum iron levels have also been reported with both estrogenic and progestogen preparations of oral contraceptives.  There has been limited reported research that has determined mineral metabolism in cattle as affected by anabolic implants of progesterone based compounds like Synovex®, or those that mimic estrogenic compounds like zeranol as found in Ralgro®.

 

OBJECTIVES

This study was initiated to elucidate the effect of the anabolic implants, particularly Synovex-S® and Ralgro®, on serum mineral concentrations (calcium, iron, magnesium and zinc) in cattle of large and small frame size.

 

PROCEDURE

Sixty-four crossbred steers were assigned to one of three treatment groups, control (n=19), Ralgro® (n=22) or Synovex® (n=23).  Within these treatment groups, 29 large and 35 small frame sized cattle were assigned.  Implanted animals were reimplanted at 90 day intervals.  Large frame cattle were either Charolais sired or Chianina sired steers.  Small frame cattle were genetically distinct from large frame cattle and were sired by either Red Poll, Hereford X (Angus-Hereford) or Angus X Brahman.  Brahman breeding did not exceed ¼ of the genetic background of any small framed steer.

Steers were fed, ad libitum, a high grain finishing diet based on either ground sorghum or whole shelled corn.  Serum samples were obtained 28 days post-implant via jugular vein venipuncture.  Samples were kept on ice until centrifuged for extraction of serum and then stored at minus 10oC until analysed.  Mineral analysis was performed by atomic absorption spectroscopy for calcium, magnesium, iron and zinc.  Data was analysed using the General Linear Models procedure of the Statistical Analysis System.

 

RESULTS

Serum calcium concentrations of steers are shown in Table 1.  Serum calcium concentrations were not different (P>0.10) between implant groups or frame size.  Serum calcium concentrations ranged from 8.8 to 9mg/dl for bleeding 1 (28 days post first implant) and 9.5 to 10mg/dl for bleeding 2 (28 days post second implant).

Serum magnesium concentrations were not affected (P>0.05) by implant treatment or frame size.  The serum magnesium concentrations were lower than expected for steers consuming a high concentrate diet.  The low concentration of serum magnesium in these steers could have masked any potential effect caused by the implants, since research has indicated that females using estrogenic contraceptives have been found to be hypomagnesemic.

When summarized by main effects, there were no differences between treatment groups or frame size for serum iron concentrations (Table 3).  Serum iron concentrations were lower during the second bleeding which occurred 118 days after the initiation of the experiment.  This could be a reflection of liver iron depletion in steers fed this diet.  There was an interaction (P<0.05) between implant groups and frame size for serum iron concentrations.  The interaction occurred due to a 19.7% decrease in the large framed steers when implanted with Synovex-S® compared to those not receiving an implant, with those implanted with Ralgro® being intermediate.  Additionally, serum iron concentrations increased (P<0.05) 39.6% in steers of the small frame group when implanted with Synovex-S® compared to the control cattle, with cattle implanted with Ralgro® being intermediate.  Work with oral contraceptives in humans have generally indicated a tendency towards greater serum iron levels.

Serum zinc concentrations of steers are shown in Table 4.  At 28 days after the first implant, serum zinc concentrations decreased from 88.5 to 79.4µg/dl when cattle were implanted with Synovex-S®, with cattle implanted with Ralgro® being intermediate, 83.4µg/dl.  Although serum zinc concentrations at the second bleeding date were not different between treatment groups, cattle implanted with Synovex-S® tended to have lower concentrations of zinc than the other treatment groups.  A significant interaction between frame size and implant treatment group occurred during the first bleeding date.  Large frame steers implanted with Synovex-S® and Ralgro® had a 12.1 and 9.3% decrease in serum zinc concentrations, respectively, and small frame steers implanted with Ralgro® had a 9.6% increase in serum zinc concentrations compared to the control steers.

As scientists strive for more efficient lean beef production through the use of growth promotants, the animal’s nutritional demands may be altered, thereby becoming a rate limiting parameter, if not dealt with.  In light of this data, a follow up study is presently underway at the Texas Agricultural Experiment Station in McGregor, Texas to further elucidate mineral metabolism in relationship to anabolic agents.

 

Table 1:

SERUM CALCIUM CONCENTRATIONS IN STEERS OF TWO FRAME SIZES IMPLANTED WITH NONE, RALGRO® OR SYNOVEX® IMPLANTS

Bleeding

Treatment

Frame Size

Control

Ralgro®

Synovex®

Large

Small

mg/dl

1

9.0

9.0

8.8

9.0

8.9

2

9.5

10.0

9.5

9.8

9.5

 

Table 2:

SERUM MAGNESIUM CONCENTRATIONS IN STEERS OF TWO FRAME SIZES IMPLANTED WITH NONE, RALGRO® OR SYNOVEX® IMPLANTS

Bleeding

Treatment

Frame Size

Control

Ralgro®

Synovex®

Large

Small

mg/dl

1

1.2

1.4

1.4

1.4

1.3

2

1.6

1.7

1.7

1.7

1.6

 

Table 3:

SERUM IRON CONCENTRATIONS IN STEERS OF TWO FRAME SIZES IMPLANTED WITH NONE, RALGRO® OR SYNOVEX® IMPLANTS

Bleeding

Treatment

Frame Size

Control

Ralgro®

Synovex®

Large

Small

mg/dl

1

0.57

0.58

0.60

0.58

0.58

2

0.36

0.35

0.35

0.36

0.35

 

Table 4:

SERUM ZINC CONCENTRATIONS IN STEERS OF TWO FRAME SIZES IMPLANTED WITH NONE, RALGRO® OR SYNOVEX® IMPLANTS

Bleeding

Treatment

Frame Size

Control

Ralgro®

Synovex®

Large

Small

µg/dl

1

88.6a

83.4ab

79.4b

88.1

79.5

2

104.6

104.0

98.4

103.3

101.4

a,b Means bearing different superscripts differ (P< 0.10)

 

Table 5:

INTERACTION BETWEEN FRAME SIZE AND IMPLANT TREATMENT 

Mineral

Bleeding

Frame Size

Control

Ralgro®

Synovex®

µg/dl

Iron

1

Large

660.0

590.0

530.0

Small

480.0

580.0

670.0

Zinc

2

Large

111.3a

100.9b

97.8b

Small

97.9b

107.3ab

99.0b

a,b Means bearing different superscripts within a mineral differ (P< 0.10)

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