Description: This invention relates to animal feed compositions and to a novel method of increasing feed efficiency and growth rate by administering these compositions. More specifically this invention relates to a method of increasing feed intake in animals by administering internally as the active ingredients local anesthetics such as mepivacaine hydrochloride, bupivacaine hydrochloride, tetracaine hydrochloride, and oxethazainechloro hydrochloride in a standard premix in the feed of the animals.

Increasing the feed intake in animals, particularly ruminants, is an important commercial objective. Sheep and cattle are fed for maximum growth rate in feed lots until they reach a marketable weight. When the desired weight is achieved, the animal is sold for slaughter. There is a normal feed intake for most animals due to both physical and metabolic factors. Presumably, animals become satiated and therefore will no longer feed voluntarily.

It has been unexpectedly found that when certain local anesthetic derivatives are administered to animals, they ear more and gain weight at a faster rate resulting in better efficiency.

The compositions and methods of this invention definitely benefit the economics of animal production by inducing the animals to eat more than their normal feed intake. The animals eat more, gain weight more rapidly, and get to market faster resulting in a saving of feed cost and labor.

The increased feed intake and weight gain of animals is accomplished in accordance with this invention by a method which comprises administering internally to the animal compounds of the following basic structural formulas: ##SPC1##

In which R represents a lower alkyl having up to four carbons.

In Formula I when R is methyl, the compound is known generically as mepivacaine. When R is butyl the compound is bupivacaine. Generically Formula II is known as tetracaine and Formula III as oxethazaine.

The above compounds of Formulas I, II, and III, which are the active ingredients in the claimed methods and compositions for increasing feed intake and efficiency, are known or prepared by synthetic methods familiar to the art, as for example, those set forth in British Pat. No. 869,978 and U.S. Pat. Nos. 2,799,679, 1,889,645, and 2,780,646.

The compounds set forth by the above Formulas can be mixed with conventional animal feed compositions by incorporating them in feed or feed premix formulations in effective but nontoxic quantities which increase animal feed intake and efficiency. The feed compositions are then fed to animals, preferably ruminants, according to methods well known to the agricultural art.

The animal feeds most generally used in conjunction with the method of this invention are either various grain mixtures and/or roughage feeds such as hay commonly fed to runinant animals such as cattle or sheep. The amount of additive used to supplement such feeds will be an amount sufficient to increase growth rate and/or improve the feed efficiency of the animal but not to have a toxic or noxious effect; in the broad range of from about 10 g. to 675 g. per ton of feed, preferably from about 25 g. to 400 g. per ton. An average sheep will ingest about 3-4 lbs. of feed daily; an average feed lot steer about 20-25 lbs. Therefore the preferable broad range of dosage for ruminants by any method of internal administration is approximately 25 mg. to 5 g. per day.

For commercial use, the active ingredients can be readily used as premix formulations in which the chemical is distributed uniformly throughout a standard animal feed carrier. This premix or concentrate is then mixed with a normal diet for the animal desired. Examples of such carriers are soybean meal, corn oil, ground corn, barley, wheat, mineral mixtures such as vermiculite, diatomaceous earth, corn gluten meal, corn distillers solubles or soyflour. The active ingredient will be in amounts to satisfy the criteria set forth above for whole feed. The active ingredient will usually be present in from about 1-75% by weight of the premix composition.

The animal feeds themselves may also contain: roughages such as cellulose, hay, straw, silages, corn stalks, cotton seed hulls, oats, barley and cereal brans; natural oils such as animal fats, fish oils, safflower oil, peanut oil and cottonseed oil; antioxidants, minerals, vitamins, antibiotics, anthelmintics; and other appropriate medicaments.

Examples of typical prepared animal feed is as follows:

EXAMPLE 1

    Ingredient           Weight per cent
    ______________________________________
    Mixed hay            40.0
    Ground yellow corn   45.0
    Soybean oil meal     7.0
    Cane molasses        7.0
    Dicalcium phosphate  0.5
    Trace minerals salt  .5
    Vitamin A            300 I.U./lb.
    Vitamin D.           150 I.U./lb.
    Mepivacaine Hydrochloride
                         0.4 lb./ton of feed
    ______________________________________

EXAMPLE 2

An example of a suitable premix is as follows:

    Bupivacaine           1 lb.
    Ground yellow corn    to 10 lbs.

EXAMPLE 3

In the field the active ingredients may be administered by means of salt or molasses blocks. A typical block may be prepared using the following conditions:

    Ingredients            Weight per cent
    ______________________________________
    Dried cane molasses    44.54
    Ground soybean hulls   24.90
    Tetracaine hydrochloride
                           5.00
    Granulated salt        21.59
    Trace minerals and vitamins
                           0.20
    Stabilized animal fat  1.11
    Moisture               2.66
    ______________________________________

EXAMPLE 4

Cattle Diet

    Ingredients             Weight per cent
    ______________________________________
    Ground shelled corn     65.85
    Mixed ground hay        20.00
    Dried molasses          6.00
    Soybean meal            6.00
    Mepivacaine hydrochloride
                            1.4 lb./ton feed
    Urea                    .55
    Trace mineral salt      .50
    Dicalcium phosphate     .40
    Ground limestone        .70
    Vitamin A (30,000 units/gm.)
                            66.7 gm./ton
    Vitamin D.sub.2 (16,000,000 units/lb.)
                             7.1 gm./ton
    ______________________________________

The method of this invention comprises allowing the cattle or sheep to graze or be fed ad libitum on the supplemented rations or to be fed on a regular schedule.

The ability of the local anesthetic derivatives of this invention to increase feed intake of animals has been established by the following tests:

Feed intakes of eight sheep were measured for 6 days. During days 1, 2, 5, and 6 a basic diet was fed and during days 3 and 4 a local anesthetic was added to the same basic diet. The 2-day average daily feed intake during the treatment period (days 3 and 4) and during the post-treatment period (days 5 and 6) was compared to that during the pretreatment control period (days 1 and 2). Several levels of each local anesthetic were tested.

Table 1 represents the results of these tests performed with the local anesthetics mepivacaine, bupivacaine, tetracaine, and oxethazainechloro hydrochlorides as the active ingredients.

                  TABLE 1
    ______________________________________
                 Dose    % of Pretreatment
                 Level   Control (Feed Intake)
                   (g/kg of  Treat-
    Local Anesthetic
                   Feed)     ment    Post-Treatment
    ______________________________________
    Mepivacaine HCl
                   .21       104     92
    Mepivacaine HCl
                   .42       107     93
    Mepivacaine HCl
                   .83       111     98
    Mepivacaine HCl
                   1.20      111     90
    Mepivacaine HCl
                   1.60      114     96
    Mepivacaine HCl
                   3.20      110     106
    Bupivacaine HCl
                   .25       104
    Bupivacaine HCl
                   .50       111     99
    Bupivacaine HCl
                   .80       112     101
    Tetracaine HCl .15       106     102
    Tetracaine HCl .25       111     107
    Tetracaine HCl .375      104     105
    Tetracaine HCl .50       100     96
    Oxethazainechloro HCl
                   .40       107     103
    Oxethazainechloro HCl
                   .60       105     90
    ______________________________________

These results clearly indicate that sheep eat significantly more feed after being administered the local anesthetics mepivacaine, bupivacaine, tetracaine, and oxethazainechloro hydrochlorides.

To test the long term effect of mepivacaine hydrochloride on growing lambs, 28 sheep were randomly assigned to one of four groups after a 2-week pretreatment period during which they received a basic meal feed. During a 5-week treatment period, one group continued to receive the basic meal feed, one group received 400 mg. mepivacaine/kg. of the basic feed, one group received 700 mg. mepivacaine/kg. of the basic feed, and the last group received 1,000 mg. carbocaine/kg. of the basic feed. During the last 2 weeks (recovery period), all groups received the basic feed. Animals were weighed at the beginning of the experiment and every seventh day thereafter. Table 2 shows the group average daily feed intake during each period, and in Table 3 the average daily weight gains and feed efficiencies are disclosed for the 5-week period.

                  TABLE 2
    ______________________________________
    Group Average Daily Feed Intakes (Gms./Day)
     Group     Pretreatment Treatment   Recovery
    ______________________________________
     Control   1172         1199        1005
     400 mg/kg 1142         1291        1247
     700 mg/kg 1121         1113         996
    1000 mg/kg 1183         1162        1072
    ______________________________________
    TABLE 3
    ______________________________________
    Group Average Daily Weight Gains (kg) and Feed Efficiencies
               Weight Gain  Feed Efficiency
     Group     (kg)         (kg Feed/kg Weight Gain)
    ______________________________________
     Control   0.14         8.56
     400 mg/kg 0.17         7.53
     700 mg/kg 0.13         8.47
    1000 mg/kg 0.14         8.13
    ______________________________________

To test the long-term effect of mepivacaine hydrochloride on feed intake, 28 mature sheep were divided into four groups matched for weight. For 17 days all sheep received a basic meal diet (pretreatment); for the following 17 days one group continued to receive this diet. One group received 167 mg. mepivacaine/kg. of this diet, one group received 333 mg. mepivacaine/kg. of this diet, and the last group received 667 mg. mepivacaine/kg. of this diet. This treatment period was followed by a 17-day recovery period during which all groups received the basic meal diet. Daily feed intakes were measured and all animals were weighed weekly and at the beginning and end of each period. Each 17-day period was divided into three sections of 6, 5, and 6 days respectively, and average feed intakes/kg. weight are presented in Table 4. The group receiving the highest dose ate more for the 17-day test period.

                  TABLE 4
    ______________________________________
    Group Average Feed Intakes Gms./kg. Body Weight
     Group       6 days      5 days      6 days
    ______________________________________
    Control      31.7        31.6        29.1
    167 mg/kg    30.7        30.7        30.3
    333 mg/kg    31.1        31.1        29.9
    667 mg/kg    33.5        33.9        34.0
    ______________________________________

These results further indicate that mepivacaine hydrochloride has a sustained effect on feed intake and results in improved rates of gain and feed efficiency.