Trials with Hexoestrol for Beef Production

New Zealand Journal of Agriculture, Volume 99, Issue 4, 15 October 1959, Page 360

Trials with Hexoestrol for Beef Production

THE use of sex hormones fo increase the rate of THE use of sex hormones to increase the rate of a production of beef cattle has been studied at Ruakura Animal Research Station and a preliminary report was given in a paper to the Station's Farmers’ Conference in 1958. Results of further work reported to the 1959 conference in June last were stated to show that hexoestrol could be a most valuable too! for increasing efficiency of beef production; but it was a treatment about which much had yet to be learnt and the drug should be available for use by farmers only through veterinarians.*

By

G. C. EVERITT,

Scientific Officer, Department of Agriculture Ruakura Animal Research Station, Hamilton

IT is regrettable that beef production is severely penalised by a slow turnover; ‘ it takes at least two and a half years to. produce an animal suitable for the chiller beef trade. Any economical method, therefore, which will increase this rate of production, but at the same time retain the essential features of meat quality, has much to commend it. One way is to give sex hormones to steers during the final fattening stage of growth. A report of a pilot trial with hexoestrol, a manufactured sex hormone, in fattening beef steers was given to this conference last year. In effect this treatment aims to replace some of the sex hormone in the castrated animal, the source of which was removed at the time of castration.

GENERALLY, castration prevents the development of the secondary male characteristics; that is, those characters which, while closely associated with the male sex, are not directly concerned with the reproductive processes. The flesh of castrated animals is much improved thereby and they lay down fat more readily. In terms of growth-rate, however, as distinct from rate of maturity, the entire male has a higher rate of gain than the castrate. The sex hormone produced by the testicles is responsible for these and other characteristics. It is quite understandable, therefore, that in the attempt to replace some of the sex hormone in the castrated animal the amount given is critical, as is the time of replacement, for though stimulation of growth-rate is required, production of the secondary male characters is undesirable. The results of the small pilot trial described last year encouraged us to carry out a series of larger trials both at Ruakura, where detailed investigations could be made, and on farms in the Waikato area. The latter experiments would provide results from cattle kept under a variety of farm conditions, though, necessarily, such results would be more general.

EXPERIMENTS AT RUAKURA At Ruakura two groups of Aberdeen Angus steers were available, namely: (a) Twelve two year olds in fresh store condition, and (b) Eleven five year olds, previously used on the Hill Station but overwintered at Ruakura, which were fairly forward in condition. Six of the two-year-old steers were implanted with 60 mg of hexoestrol on 29 September 1958; the remaining six steers were not treated and acted as controls. The hormone was supplied as four very small pellets, each pellet weighing 15 mg and being about the size of a small match head. The illustration on page 360 shows the size of a pellet of hexoestrol and the instrument used for implanting. The illustration above right shows how implantation is done where the steer’s head is restrained by a head

bail, the pellets being implanted under the loose skin at the top and back of the ear. This illustration is included to emphasise that much of the success of this treatment is dependent on obtaining a good implant and this can be done only when the animal is properly restrained. Implantation of the five-year-old steers was done on 7 October 1958. It consisted of six pellets, or a total of 90 mg, of hexoestrol. The same method of implantation was used. Five steers were implanted and six. were left untreated to act as controls. All these cattle were run together and given good grazing, without supplementary feed. . Live weights were recorded every two weeks. One of the possible disadvantages of this treatment is that certain defects, mainly of conformation and commonly

termed “side .effects”, may become apparent in the animal. Consequently, the cattle were closely - observed throughout the trial. There - was a suspicion that the treated steers were more easily excited and this was most noticeable at the time of slaughter. No other side effects were seen, except that the rudimentary teats of the treated cattle became much enlarged. •\ .. . Slaughter took place in January 1959, 91 days after implantation of the five-year-old steers and 101 days after implantation of the two-year-old steers. There was no indication by eye judgment that treated steers were finished sooner than their controls. Two-year-old Steers

Table 1 summarises some of the information relating to the two-year-old steers, and for comparison the results of the previous year’s pilot trial are included.

TABLE I—EFFECT OF HORMONE IMPLANTATION ON LIVE-WEIGHT GAIN OF TWO-YEAR-OLD STEERS

1957-58 1958-59 Control Treated Control Treated Number of steers .. .. ..4 4 6 6 Dosage level of hormone (mg) .. .. 60 60 Live weight at start of trial (lb) .. .. 950 949 887 893 Number of days on trial .. .. .. .. 107 107 101 101 Total live-weight gain (lb) .. .. .. 212 307 245 317 Weight increase per day (lb) .. .. .. 1.98 2.87 2.43 3.15 Percentage increase in daily live-weight gain .. 100 . 145 100 130

Treated steers added a total of 317 ib live weight or 3.15 lb per day, compared with only 245 lb total liveweight gain or 2.43 lb per day for the controls. This means that the treated steers had an increased daily liveweight gain of 30 per cent. Though the treated steers in the 1957-58 pilot trial had an increased rate of gain of 45 per cent over the controls, the actual gains of both control and treated steers were less than in this year’s experiment. Nevertheless, the results from the two trials agree fairly closely.

Five-year-old Steers Similar information for the five-year-old steers is given in Table 2.

TABLE 2—EFFECT OF HORMONE IMPLANTATION ON LIVE-WEIGHT GAIN OF FIVE-YEAR-OLD STEERS

1957-58 1958-59 Control Treated Control Treated Number of steers ... ■ ... .. .... 7.7. 6 7 Dosage level of hormone (mg) .. .. .. . 90 90 Live weight at start of trial (lb) .. .1,221 1,208 1,338 1,345. Number of days on trial .. ... ... 102 . 88 91 .■ . .. 9.1 Total live-weight gain (lb) .. .. . . 348 378 225 279 Weight increase per day (lb) .. .. .. 3.39 4.35 2.56 . 3.17 Percentage increase in daily live-weight gain .. 100 128 100 124

Again there is a close agreement of the results from the two trials. In the 1958-59 trial the treated steers had an increased daily live-weight gain of 24 per cent compared with 28 per cent in the previous year. In overseas trials with this drug results have tended to be inconsistent; in other words, the precise amount of gain cannot be guaranteed any more than can the growth-rates of untreated cattle.

Closer investigation of these liveweight gains has revealed that for both age groups the. increased gains of the treated groups were more apparent in the second half of the feeding period. This fact does not agree with a lot of work done overseas where the greatest effect has been in the first six weeks after implantation. This inconsistency in results will have to be checked by future work.

Carcass Quality With a treatment such as this it is vital that the story should be taken beyond the farm gate; the quality of the product is immensely important. Each carcass was assessed for quality by a system which has been used at Ruakura for many years. Essentially this system consists of allocating marks for certain carcass characteristics which are assessed, mainly, by measurements. . Many farmers will know this type of judging from the shows held at various. freezing works. Some of these carcass-quality results are given in. Tables 3 and 4.

TABLE 3—EFFECT OF HORMONE IMPLANTATION ON CARCASS QUALITY OF TWO-YEAR-OLD STEERS

Control Treated Live weight at slaughter (lb) 1,130 1,211 Carcass weight (lb) .. .. 593 , 621 Dressing out (per cent) ... 52.48 51.28 Blockiness: Measurement (in.) .. .. 17.25 17.0 Points (maximum, 20) .. 7 9 Rib-cover points (maximum, 5)3 4 Fat-distribution points (maximum, 10) .. .. . . 6 7 Balance of carcass (hinds minus fores: Difference in weight (lb) .. +l3 +l3 Points (maximum, 10) .. 6 5 Weight of : kidney and channel fat (lb) -17.6 13.0 Total carcass score .... 53 53

In Two-year-old Steers For the two-year-old steers the difference of 81 lb in live weight at slaughter between the two groups was reduced to a. difference of 28 lb in carcass weight. This was due to the lower dressing,-out percentage, which is the carcass weight expressed as a percentage of the live weight, of the treated steers, and it means that there was a greater production of uneatable products. Treated cattle produced carcasses which were more blocky, with a better cover of meat over the ribs, and with the fat distributed more equably than in the untreated carcasses. This latter point is reflected in the weights of excess fat surrounding, and near to, the kidneys, where the treated carcasses had nearly 5 lb less fat. Today, this factor of fatness, particularly in this region of the body, is a very important selling point. The best cuts of meat are located in the hind end of ..the beef carcass, and the heavier the hind end is. in relation to the fore end the better; this is known as the balance of the carcass. There. was no difference in weight, however, in the balance of the carcass between the two groups. No differ-

ences were observed in the thickness of the “eye” muscle, which denotes a meaty carcass; in the depth of fat over the “eye” muscle, in marbling of the muscle, or in the colour and texture of muscle and fat. Despite the variations in individual characteristics, both control and treated steers attained the same total carcass score.

In Five-year-old Steers Information about the five-year-old steers is given in Table 4.

TABLE 4—EFFECT OF HORMONE IMPLANTATION ON CARCASS QUALITY OF FIVE-YEAR-OLD STEERS

■ '(: Control Treated Live weight at slaughter (lb) 1,563 1,623 Carcass weight (lb) .. .. 835 857 Dressing out (per cent) .. 53.42 52.80 Fullness of meat (depth of “eye” muscle): Measurement (mm) ... 60 63 Points (maximum, 20) . . 6 7 Fat cover, depth of fat over “eye” muscle: Points (maximum, 20) .. 9 10 Blockiness: Measurement (in.) .. .. 19 19 Points (maximum) .. .. 6 7 Bib-cover points (maximum, 5) .2 3 Balance of carcass (hinds minus fores): Difference in weight (lb) ... 4-38 4-8 Points (maximum, 10) .. . 3 1 Weight of kidney and channel fat (lb) 24.1 17.4 Total carcass score (maximum, 100) 42 41

Dressing-out percentage of treated five-year-old steers was again slightly lower than that of the control steers, and this meant that a difference of 60 lb in live weight at slaughter was reduced to a difference of 22 lb in carcass weight. No differences were observed in the marbling or in the colour and texture of muscle and fat. Treated steers produced more meaty carcasses, as judged by measurements of the “eye” muscle, and the fat cover over the “eye” muscle earned more marks. The carcasses of treated steers were more blocky and the rib cover was superior. Because the fore ends of the treated steers were proportionately heavier than the hind ends, only one mark was allowed for this character compared with three marks for the control steers. The weight of excess fat near the kidneys was 6lb less in the treated animals, and this must be taken into account when considering carcass balance. Total carcass scores of the two groups were very similar. Effect on Consumer Finally, the consumer of this meat was considered. Has the treatment any effect on the consumer? To assess if there was any hormone left in the carcass, various parts were subjected to a very sensitive test, and no detectable amount could be found when the drug was given to the animal in the amounts previously stated. This problem has received considerable attention from overseas workers, and it has been calculated that over 140 lb of meat per day would have to be eaten

to produce any effect.

In this respect it is important to remember that the drug was placed in the ear, a part not consumed, but a serious danger would exist if the drug was implanted anywhere else, for then any hormone unabsorbed at slaughter would be present in large amounts. Results of Ruakura Experiments To sum up these Ruakura experiments, it seems that the doses of hexoestrol used have increased live weight by about 60 to 80 lb. Owing to a lower dressing-out percentage this has increased carcass weight by 20 to 30 lb. There has been no significant depreciation of carcass quality from the treatment; indeed, there have been some indications of. better quality owing to a more meaty carcass with slightly less fat. These results substantiate those of last year. If it is assumed that beef sells at 120 s. per 100 lb, this carcass weight increase is worth about 255. to 40s. per head. Each 15 mg pellet of hexoestrol costs 3d. and if the initial cost of the implanting instrument (about 355.) and of labour of implanting and of depreciation of equipment is included, a total cost of about Is. 6d. per head seems appropriate. This is quite a rosy picture, but before jumping to conclusions we must examine the results from the field scale trials. FIELD TRIALS The purpose of the field trials was to investigate the effect of various levels of hexoestrol on the live-weight gain and carcass

quality of Aberdeen Angus steers kept under a variety of New Zealand grassland farming conditions. It had been expected that the 60 mg dose of hexoestrol might induce undesirable side effects and there was also some overseas evidence to suggest that lower levels than 60 mg might produce as much, if not more, weight gain in animals. Therefore in these field trials the doses of hexoestrol used were 30 mg (or two pellets) and 45 mg (or three pellets, each of 15 mg). Response to treatment with hexoestrol may vary according to seasonal

conditions. The majority of cattle were implanted, therefore, in spring, but a smaller number were also treated in autumn. Only the results from the cattle treated between September and December 1958 are at present available. Seven farmers cooperated in these trials. All the farms were within a 30-mile radius approximately of Ruakura; their location is shown in the diagram below. The varied nutritional and management conditions of these seven farms can be considered as a reasonable sample for the Waikato at least. On each farm the cattle used for the experiment were divided at random into three groups (an untreated or control group, a group treated with 30 mg of hexoestrol, and a group implanted with 45 mg). An ear tag was given to each steer and the drug was implanted in the right ear of the cattle in the treatment groups. Subsequently all the cattle were weighed on a mobile weighing machine. The farmer was asked to feed the cattle well at all times, to retain them for about three months, and to market them through one of the schedule-price meat organisations. Owing to the serious risk of bruising cattle if they are weighed immediately before slaughter, live weights were obtained only at the time of implantation. The gains made by the cattle on trial were estimated by assuming that ,at the time of treatment all the cattle would have given a dressing-out percentage of 53. This estimated carcass weight was then

compared with the carcass weight obtained at slaughter, and the difference taken as the gain made by the animal. It is important to realise that this method gives only an estimate of the carcass gains made; the comparison can only be a relative one between groups, and the real or absolute gains of each group may have been rather different.

Two-year-old Steers A summary of the. results of some of the two-year-old cattle ,in the trial is given in Table 5. As the farm conditions varied greatly, it is necessary to consider each farm separately. .

TABLE S—CARCASS WEIGHT GAINS BY TWO YEAR OLDS IN FIELD SCALE TRIALS WITH HEXOESTROL, 1958-59

Farm A Farm B Farm C Farm D Farm E Days on trial .. ... 118 134 124 133 139 . . Treatment (mg of hexoestrol) 30 45 ■ — 30 45 - 30 45 30. 45 30 4.> Number of steers ... .. 9 9 9 8 11 11 12 13 11 10 11 12 8 8 i Gain in carcass weight (lb) 160 175 200 170 190 195 120 145 145 160 185 165 155 185 165 Percentage increase in carcass gain of treated/ , „ control steers .. .. 100 109 125 100 112 115 100 121 121 100 116 103 100 119 106 Total carcass score (maxi- „ „„ „„. „ „„ mum, 100) .. .. .. 57 59 61 61 58 58 58 .57 57 63 62 63 62 60 60

Farm A The 27 cattle on Farm A were killed 118 days after implantation. The 45 mg dose of hexoestrol added 40 lb in estimated carcass weight, or 25 per cent more than in the untreated steers, -while the. 30 mg dose added 15 lb or an extra 9 per cent. No side effects were observed, except that some of the 45 mg-treated group produced a dark-cutting meat. Total carcass scores reveal the two treated groups to be slightly superior in overall quality and this was mainly due to the production of more meaty carcasses. Farm B On Farm B the cattle were selected for slaughter by the farmer as they became “finished” in condition, and there was some indication that the two treated groups, especially those dosed at the 30 mg level, reached a marketable state sooner than the untreated group. The 45 mg dose gave a slightly increased gain over the 30 mg and both treatments had increased gain of 12 lo 15 per cent over the control group. Carcass scores of the two treated groups were the same, 58 marks out of 100, but were three less than those of the untreated steers. It is possible that some of these animals were either implanted when too young or that they were kept on treatment too long. Whatever the cause, the treated carcasses lost a number of marks by being too lean for present requirements. Farm C Again there was an indication from the marketing of Farm C cattle that the treated groups were finished slightly before the untreated steers. Increased gains made by the two hexoestrol treatments were the same,

each treated group having a 21 per cent increase over the control group. A number of the carcasses from the 45 mg group showed considerable side effects, such as dark-cutting meat and a staggy appearance which produced relatively heavy fore ends and an elevation of the tail head with consequent depression of . the loin region. Total carcass scores of the two treated groups were only one mark less, however, than those of the untreated group; the side effects were counteracted mainly by increased muscle

content and by a better fat distribution. . Farm D Farm D stock were slaughtered 133 days after implantation. The 30 mg dose produced the greatest gain, with an increase of 16 per cent over the controls, whereas the 45 mg dose gave only a 3 per cent increase. No side effects were seen in either of the treated groups and the total carcass scores were very similar. Meatiness of the carcasses of the two treated groups was better than that of the controls and fat cover and fat distribution got higher scores. Farm E Cattle from Farm E were slaughtered 139 days after beginning of the treatment. The smaller dose of hexoestrol increased carcass gain by 19 per cent compared with 6 per cent for the 45 mg dose. The fore ends of the carcasses of both treated groups were proportionately heavy and there was evidence of dark-cutting meat from the steers treated with 45 mg. Thus the two treated groups had a lower total carcass score than the control group.

Three-year-old Steers Results for some of the three-year-old cattle in the trial are given in Table 6.

TABLE 6—CARCASS WEIGHT GAINS BY THREE YEAR OLDS IN FIELD SCALE TRIALS WITH HEXOESTROL, 1958-59

Farm F Farm G Days on trial .. .. ~ .. .. .. .. .. 97 103 Treatment (mg of hexoestrol) .. .. .. .. .. .. 30 45 30 45 Number of steers .. .. ... .. .. .. .. 10 10 10 7 6 6 Gain in carcass weight (lb) .. .. .. .. .. .. 100 130 135 145 155 145 Percentage increase in carcass gain of treated/control steers ..... 100 130 135 100 107 100 Total carcass score (maximum, 100) .. .. .. .. .. 53 55 55 -

Farm F Ninety-seven days elapsed between implantation and slaughter of cattle from Farm F. The gains of cattle were the lowest of any in the experiment and yet the 30 mg and 45 mg treated groups had increased carcass gains of 30 per cent and 35 per cent respectively over the controls. Fat distribution was definitely superior in the two treated groups and total carcass scores of these two groups were two marks higher than those of the controls. Severe side effects were apparent in the 45 mg group, but were absent in the group which received the smaller dose. Farm G On Farm G increase in carcass gain was shown only by the group. which received 30 mg; the 45 mg group showed no increase over the control group..; Carcass-quality assessments were not obtained for these cattle. The

small increased carcass gain from the smaller dose and the absence of an effect from the 45 mg dose were probably due. to the rather poor feeding conditions on this farm, but the numbers in each group were also small. Results of Trials These field trials with hexoestrol can be summarised as follows: Under good feeding conditions there have been increases in carcass weights from both the 30 mg and 45 mg doses of hexoestrol. These increases have ranged from 10 per cent to 33 per cent over untreated cattle. Some of the responses from 45 mg have been superior to those from 30 mg and some have been inferior. Most important, the 45 mg dose induced in many of the cattle side effects which were not apparent in cattle dosed with 30 mg. Therefore it can be concluded that for two- and three-year-old Aberdeen Angus steers, at least, the smaller dose, 30 mg, is probably the optimum for commercial application. This dose is likely to give as good weight gains as would the larger dose and the possibility of side effects is minimal. LESSONS OF TRIALS There is still much to be learnt about the use of sex hormones in meat production, but several interim recommendations can be made in the light

of the results described here. The optimum dose of 30 mg of hexoestrol has already been mentioned. Dangers of overdosing can be emphasised again. With excessive doses of hexoestrol growth-rate may be depressed, side effects will appear with consequent deleterious effects on carcass quality, and, in severe cases, there may be blockage of the intestinal and reproductive systems. Present knowledge allows us to recommend this treatment for steers only; the value of the use of hexoestrol in fattening heifers is problematical and requires more research. Breeding stock of any class is definitely not suitable for hexoestrol implantation. The age, weight, and condition at which the. steers are implanted are important. Firstly, the animal should be in the final fattening stage of growth. For Aberdeen Angus steers this means that they will probably be not less than two years old and that they will weigh about 8 cwt live weight or 450 to 500 lb carcass weight. Treatment of relatively young and immature cattle will cause the development of very large bones and little else. There is only one place to implant the hormone pellets: beneath the loose skin at the back of the ear. To do this simple operation efficiently a good head-bail is essential.

Placing the drug in any other part of the animal but the ear is potentially extremely dangerous to the consumer. Cattle must be well fed from the time of implantation, to the time of slaughter; otherwise the effect may not be apparent. The treatment period should last approximately 100 days. We do not know precisely what happens if these two rules are not observed, but probably there would be little or no useful effect from the treatment; trials have been started recently to investigate these two points. Finally, cattle treated with sex hormones must be handled much more efficiently and quietly than normal stock. The treatment makes the animal more susceptible to stress and excitement of any description. . An excited animal will not make efficient weight gains and there may be detrimental effects on carcass quality. An important question not yet adequately answered is whether . the treatment has any effect on subsequent grazing stock through hormonal activity in the excrement, though recent work in Britain indicates that any residual hormone in the excreta is fairly quickly made inactive by certain soil micro-organisms. This danger, of course, is more real when animals are given hormones by mouth. Research work will continue on this problem.

At the beginning of this article it was emphasised that this treatment is a scientific attempt to restore the sex hormone balance of the castrated animal to a prescribed level, and the treatment should be considered in this light. It cannot replace, in any way, good animal husbandry. Results have shown that intelligent use of hexoestrol can prove most valuable for increasing the efficiency of beef production. But because very little is known of the precise mode of action of the treatment and because of the long list of possible dangers the treatment is obviously open to the widest abuse. For these reasons it is my personal, strong recommendation that this drug and others like it should not be readily available to farmers, but rather that they should have access to it through their veterinarians. This recommendation is not made lightly, but I consider that placing this restriction on the drug’s commercial use will at least help to ensure that New Zealand’s pre-eminent position as a meat-exporting country is guarded. Acknowledgments Thanks are offered to farmers who cooperated in the field trials; to Messrs R. and W. Hellaby Ltd., Messrs W. and R. Fletcher Ltd., the staff of the Horotiu Freezing Works of the Auckland Farmers Freezing Company, and to Messrs Evans, who supplied the hexoestrol for this work.

* At the close of discussion on the paper a motion by Mr F. C. Johnstone, deputy chairman of the New Zealand Meat Producers Board, that hexoestrol be used in the meantime only by veterinarians and not by farmers indiscriminately was seconded and carried on the voices of an attendance of about 800.