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U.S. Department of Health and Human Services

Animal & Veterinary

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NADA 140-869 Purina Bloat Block - original approval

Approval Date: August 8, 1989

I. GENERAL INFORMATION:

NADA140-869
Sponsor:Purina Mills, Inc.
P.O. Box 66812
St. Louis, Missouri 63166-6812
Generic Name:medicated feed block containing 6.6% poloxalene
Trade Name:Purina Bloat Block
Marketing Status: 

 

II. INDICATIONS FOR USE

For control of legume (alfalfa, clover) and wheat pasture bloat in cattle when consumed at the prescribed rate.

 

III. DOSAGE

A.DOSAGE FORMMedicated Feed Block containing 6.6% Poloxalene
B.ROUTE OF ADMINISTRATIONTo be fed free choice to pasture cattle on pasture
C.RECOMMENDED DOSAGES:0.8 oz (0.05 lb) of block/100 lb body weight to provide each animal 1.5 grams of Poloxalene/100 lb body weight per day.

 

IV. EFFECTIVENESS

Summary
Poloxalene is already approved for use in pasture feeds for the control of legume and wheat pasture bloat in cattle as specified in 21 CFR 558.465. Since authorization was granted to Purina Mills, Inc. by SmithKline Animal Health Products to refer to the dose response data contained in NADA 32-704v, no other dose response study was conducted. However, the following efficacy and consumption studies were conducted with the proposed block to show the drug to be effective in the free choice feed.

Efficacy
This study was conducted by E.G. Johnson, Parma, Idaho. Four groups of 15 steers each were used in the double blind study to evaluate the effectiveness of poloxalene in controlling frothy bloat when administered in a free choice high molasses block. The study was conducted on lush alfalfa pastures as it is more likely to precipitate bloat than is wheat pasture. The four groups of animals were placed on four grass pastures until the experiment was initiated. At random, two groups of steers with an average initial weight of 558 lbs were assigned to the medicated blocks and the remaining two groups of steers with an average weight of 555 lbs were assigned to the non-medicated blocks. Animals were offered the experimental blocks before being placed on alfalfa pasture to allow ruminal levels of poloxalene to reach an efficacious amount in the steers on the blindly assigned medicated blocks. Each animal group was rotated approximately every seven days among 16 pastures. The study was conducted for 91 days.

Animals were individually monitored for bloat and for severity of rumen distention using scoring system of zero through three for daily animal evaluation.

0 = no abdominal distention

1 = distention of left side

2 = distention of left and right side, animal distressed

3 = severe distention of left and right side, animal in severe distress, terminal unless relieved.

Weights were taken on a full animal weight basis and were done at 0 day and each 28 days thereafter. The reason for full weights was to prevent poloxalene levels in the medicated groups from becoming depleted to inefficacious levels at a time of substantial forage intake following a fast. Full weights were taken at the same time of the day to reduce variability due to fill.

Poloxalene was consumed free choice at an average of 1.7 g per 100 lbs full body weight. Pooled consumption data across animal groups showed a coefficient of variations of 37.9%. When poloxalene was consumed in a free choice high molasses compressed block by cattle grazing alfalfa pastures, the incidence of severe ruminal distentions was significantly reduced compared to cattle consuming non-medicated blocks (31 vs. 209 total animal days with a bloat score). The total number of animal days with a non-zero score were greater (P .01) with the non-medicated vs. the medicated group of steers.

Consumption studies
Three consumption studies were conducted in three different locations as follows:

a. Arkansas Study:

This study was conducted at the University of Arkansas, Batesville, Arkansas, by Ken Harrision, Resident Director of Experiment Station.

Three groups of 15 heifers each were used in the 50 day study. Three wheat pastures were used, each approximately 10 acres in size. Heifers were weighed and allotted to their three groups one week prior to the start of the experiment. The three groups of animals were placed on their initially assigned wheat pastures and offered non-medicated blocks prior to the start of the experiment to acquaint them with block feeding. The non-medicated blocks were removed on day 1 and replaced with medicated blocks at a feeding rate of one per five animals in all three groups. The three groups were rotated approximately every 14 days among three wheat pastures. Blocks were weighed weekly and recorded on separate record sheets for each group of animals. New blocks were added when judged necessary to prevent each group from running out.

The following consumption results were obtained:

(Eds. note: The following table consists of 3 columns.)

Avg. Ending Wt.Block consumption
lbs/100 lb body wt./day
 
Poloxalene
g/100 lb body wt.
 
All Groups 649 lbs.1033.1

Pooled consumption data across animal groups showed a coefficient of variation of 24.8%.

b. Texas Study:

This study was conducted at Texas Agricultural Experiment Station, by D.P. Hutchinson, Amarillo Texas. Three groups of 15 steers each were used in the 91 day study. Steers were weighed and placed into three groups on the basis of weight and breed. Steers were alloted to their groups on day 1 of the experiment. One to two weeks prior to the start of the experiment, the steers were exposed as a group to non-medicated blocks to acquaint them with block feeding. After being alloted to three groups on day one, the three groups were placed on their initially assigned wheat pastures and offered medicated blocks at a feeding rate of one per five animals in all three groups. The three groups were rotated approximately every 14 days among the three pastures.

Each week, the amount of blocks remaining in the feeders were weighed in each pasture. New blocks were added to prevent each group from running out. Three wheat pastures were used, each approximately 13 acres in size. Pasture conditions were observed every 14 days and recorded.

The following consumption results were obtained:

(Eds. note: The following table consists of 3 columns.)

Avg. Ending Wt.Block consumption
lbs/100 lb body wt./day
 
Poloxalene
g/100 lb body wt.
 
All Groups 736 lbs.04071.2

Pooled consumption data across animal groups showed a coefficient of variation of 22.2%.

c. Idaho Study:

This study described previously under efficacy was conducted to collect both efficacy and consumption data in one location.

The following consumption results were obtained in this study:

(Eds. note: The following table consists of 3 columns.)

Avg. Ending Wt.Block Consumption
lbs/100 lb body wt./day
 
Poloxalene
g/100 lb body wt.
 
All Groups 786 lbs.05751.7

Pooled consumption data across animal groups showed a coefficient of variation of 37.9%. Although there was some overconsumption of the drug in the Arkansas study, the variations in intake in the consumption studies compared favorable with the variations in intake in the efficacy study.

 

V. ANIMAL SAFETY

Data contained in this application show an average block consumption of .067 lbs medicated block to provide an average dose of 2 g poloxalene per 100 lbs body weight without causing any adverse effect. Reference is also made to safety data contained in NADA 32-704v.

 

VI. HUMAN FOOD SAFETY

Authorization has also been granted to refer to the human food safety data contained in NADA 32-704v.

 

VII. AGENCY CONCLUSIONS:

The data submitted in support of this NADA satisfy the requirements of section 512 of the act and demonstrate that Poloxalene 6.6% Medicated Feed Block when used under its proposed conditions of use is safe and effective for the control of legume (alfalfa, clover) and wheat pasture bloat in cattle when consumed at the prescribed rate. Because of the drug's route of administration, conditions to be treated, and adequate directions for use for the layman, the Agency concluded that Poloxalene 6.6% Medicated Feed Block (containing molasses) can be marketed over the counter.

Poloxalene Type A Medicated Articles are currently codified in sections 21 CFR 558.464 (Poloxalene) and 558.465 (poloxalene free choice liquid Type C Feed) for use in cattle providing for the same conditions of use. It is also codified in section 21 CFR 520.1840 for use in cattle as a drench or in molasses block or as a 53% Poloxalene top dressing on individual rations of ground feed.

 

VIII. LABELING (Attached)

Copies of applicable labels may be obtained by writing to the:

Freedom of Information Office
Center for Veterinary Medicine, FDA
7500 Standish Place
Rockville, MD 20855