The effect of anabolic agents on growth rate and reproductive organs of pigs

Livestock Production Science, 26 (1990) 263-275

263

Elsevier Science Publishers B.V., Amsterdam

The effect of anabolic agents on growth rate and reproductive organs of pigs P.J. Sheridan*, F.H. Austin**, S. Bourke and J.F. Roche Department of Animal Husbandry and Production, Faculty of VeterinaryMedicine, Ballsbridge, Dublin 4 (Ireland) (Accepted for publication 5 March 1990)

ABSTRACT Sheridan, P.J., Austin, F.H., Bourke, S. and Roche, J.F., 1990. The effect ofanabolic agents on growth rate and reproductive organs of pigs. Livest. Prod. Sci., 26: 263-275. Three hundred and four hybrid pigs were implanted at 35-40 kg and slaughtered at 75-80 kg body weight in an effort to determine the effects of anabolic steroid implants on growth rate, carcass characteristics and reproductive organs of growing pigs. Implantinghad no effect on growth rate or carcass weight of boars, castrates or gilts. Feed conversion ratio of gilts implanted with 20 mg oestradiol + 140 mg trenbolone acetate improved (P< 0.05) and mid-back fat was reduced (P< 0.05 ). Mid-loin fat was reduced in castrates implanted with 10 mg oestradiol + 100 mg testosterone (P< 0.05). Carcass characteristics of boars were unaffected by implants. All implants decreased ovarian weight (P< 0.05) and, with the exception of those containing trenbolone acetate, increased uterine weight (P< 0.05 ). Testicular measurements and weights were decreased by implants containing trenbolone acetate (P< 0.01 ). Anabolic steroids do not appear to be suitable agents for improving growth or carcass characteristics of pigs. Keywords: anabolic agents; carcass traits; pig growth rate; reproductive organs.

INTRODUCTION

Although their effects in beef cattle are clearly established, knowledge of the effectiveness of anabolic steroids in pig production is limited (Galbraith and Topps, 1981; DeWilde and Lauwers, 1984). Small increases in daily liveweight gain and feed conversion efficiency which might be brought about by the use of anabolic steroids, could be of benefit to pig producers. Anabolic steroids also tend to increase the lean to fat ratio of the carcass, and the problem of excessive fat deposition makes the pig an obvious choice for treatment with anabolic agents. *Present address: Veterinary Research Laboratory, Abbotstown, Castleknock, Dublin 15, Ireland. **Author to whom correspondence should be addressed.

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Boars characteristically have a greater ratio of lean to fat tissue than gilts or castrated males (Cahil| et al., 1960; Fowler et al., 1969; Hansson et al., 1975 ), owing to the hormonal secretion of the testes. However the production, by older entire males, of a steroid which taints the meat may counteract this benefit and result in decreased consumer demand. This problem might be overcome by the use of anabolic steroid hormones in castrated male pigs, or by the use of hormones in intact males, to delay puberty and thereby delay the production of the boar-taint steroids, as has been reported with diethylstilboestrol (Echternkamp et al., 1969). The aims of these investigations were to determine the effects of different anabolic steroid implants on feed conversion efficiency, daily liveweight gain and carcass composition of fattening pigs, and to examine the effects of implantation on their reproductive organs. MATERIALS AND METHODS

Two trials were carried out on a total of 304 Landrace × Large White pigs from a similar genetic background. The pigs were approximately 40 kg liveweight at the time of implanting. The initial trial took place under experimental conditions at the Veterinary Field Station whilst a second on-farm trial was carded out on a commercial fattening unit in central Ireland. In the initial trial 88 gilts were randomly allocated and penned in groups of four animals, giving 22 groups which were then subject to one of six treatments: ( 1 ) 10 mg oestradiol benzoate plus 100 mg progesterone (Synovex S, half dose ), Syntex, U.S.A.; (2) 10 mg oestradiol benzoate plus 100 mg testosterone propionate (Synovex H, half dose), Syntex, U.S.A.; (3) 20 mg oestradiol benzoate plus 200 mg progesterone (Synovex S), (4) 20 mg oestradiol benzoate plus 200 mg testosterone propionate (Synovex H); (5) 20 mg oestradiol- 17fl plus 140 mg trenbolone acetate (Revalor) Roussel, Udaf, France; (6) Control, implant needle inserted into the ears as in other treatments. They were fed "to appetite", i.e. ad libitum with 2 h access at each feed, twice daily on a commercial fattener ration ( 13.8 MJ kg- i, 19% protein). This resulted in 16 gilts on each treatment except Treatment 5 which had eight animals. They were implanted at the base of the ear, weighed regularly and slaughtered 62-65 days later at an average liveweight of 77 kg. Carcass backfat was measured at the shoulder, mid-back and mid-loin positions and the eye muscle area determined. The uterus and ovaries were dissected free of ligaments and weighed. A second on-farm trial involved boars, castrates and gilts; 72 of each. Pigs were randomly allocated to same-sex groups of 12, fed and implanted as in the initial trial. Boars and castrates were assigned to the same treatments as in the earlier trial whilst gilts were assigned to: ( 1) 10 mg oestradiol- 17p plus

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70 mg trenbolone acetate (Revalor); (2) 140 mg trenbolone acetate (Finaplix ), Roussel Uclaf, France; ( 3 ) - ( 6 ) as in Trial 1. Treatments were randomly allocated to pigs within each pen so that two pigs were implanted with each product. This resulted in 12 animals of each sex being subjected to each of their respective treatments. The pigs were fed the same ration as in the first trial, were weighed at the start of the experiment and again prior to slaughter. At slaughter, carcass weights and backfat measurements of all animals and reproductive organs from gilts were examined as in the initial trial. In the case of boars, the testes were dissected free from surrounding tissue and epididymes and testicular lengths, maximum circumferences and weights recorded. All parameters measured, including feed conversion efficiency and average daily gain were analysed statistically using a mixed model, least-squares and maximum likelihood computer program (Harvey, 1960) and where applicable, Duncan's multiple range test (Duncan, 1955 ). RESULTS

Initial trial There was no difference (P> 0.05 ) in average daily gain, finishingweight or carcass weight of gilts(Table I ) assigned to control or the various implant treatments. Feed conversion ratio of giltsimplanted with 20 m g oestradiol17fl plus 140 m g trenbolone acetate was better than that of control animals TABLE1 The effect of implantation with oestradiol and progesterone, testosterone or trenbolone acetate on growth characteristics of gilts (initial trial) Treatment" 10 mg O B + 100 mg Prog. 20 mg O B + 2 0 0 mg Prog. 10 m g O B + 100 m g T P 20 mg O B + 200 mg TP 20 mg O- 17//+ 140 mg TBA Control RSD °

n 16 16 16 16 8 16

Final wt.

ADG

Carcass wt.

FCR b

(kg)

(g)

(kg)

on pen basis

75.0 77.9 77.1 79.3 80.4 76.1 7.32

588 637 621 655 682 623 0. l 0

58.4 60.3 59.3 61.6 62.7 58.8 7.0

2.94 ~ 2.742`3 2.79 L2 2.642'3 2.533 2.79 m'2 0.12

aOB, oestradiol benzoate; TP, testosterone propionate; TBA, trenbolone acetate; Prog., progesterone; O-! 7p, oestradiol-I 7//; NS, not significant. bMean for pens which each contained four pigs. ~Means with the same superscripts are not significantly different ( P > 0.05 ). dResidual standard deviation.

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P.J. SHERIDANET AL.

(P< 0.05). There was no significant difference (P> 0.05 ) in backfat thickness or eye muscle area (Table 2 ) in any of the experimental groups. Ovarian weights of control gilts were higher (P< 0.05) than those of all implanted gilts, while uterine weights of gilts implanted with 10 mg oestradiol benzoate plus 100 nag progesterone were higher (P< 0.05) than those of control gilts (Table 3 ).

On-farm trial Gilts There was no difference in average daily gain, finishing weight or carcass weight between treatments (P> 0.05; Table 4). The gilts implanted with 20 TABLE 2 The effect of implantation with oestradiol and progesterone, testosterone or trenbolone acetate on backfat thickness, and eye muscle area of gilts (initial trial) Treatment

n

Shoulder fat (mm)

Mid-back fat (mm)

Mid-loin fat (ram)

Eye muscle area (cm 2)

10 mg O B + 100 mg Prog. 20 mg OB + 200 mg Prog. 10 m g O B + 100 m g T P 20 mg O B + 2 0 0 mg TP 20 mg O-17p+ 140 mg TBA Control RSD

16 16 16 16 8 16

29 30 30 32 28 30 3.5

15 15 15 15 15 15 2.2

14 14 15 14 13 15 3.2

31 33 30 33 34 33 4.0

Abbreviations and superscripts as in Table 1. TABLE 3 The effect of implantation with oestradiol and progesterone, testosterone or trenbolone acetate on reproductive organs of gilts (initial trial ) • Treatment

n

Ovarian wt.

Uterine wt.

10 mg O B + 100 mg Prog. 20 mg OB + 200 nag Prog. 10 mg O B + 100 mg TP 20 mg O B + 200 nag TP 20 mg O- 17fl+ 140 mg TBA Control RSD

16 16 16 16 8 16

2.73 3.87 3.73 3.72 1.76 5.96 1.83

156 I 125"2 125 x'2 124 ~'2 105 t.2 842 52.7

"Abbreviations and superscripts as in Table 1.

(g)

(g)

24 23 24 24 24 23

I0 m g O - 1 7 p + 7 0 m g T B A 20 m g O-I 7,0+ 140 m g T B A 140 m g T B A 20 m g O B + 2 0 0 m g T P 20 m g O B + 2 0 0 m 8 Prog. Control RSD

680 680 630 670 680 690 90

(g)

(kg)

82.5 80.8 79.0 81.0 81.3 82.2 7.87

ADG

Final wt.

aAbbreviations and superscripts as in Table 1.

n

Treatment 21 23 21 23 22 21

slaughtered

Number 62.0 60.6 59.8 61.3 62.3 61.9 6.1

wt. (kg)

Carcass 35 34 36 37 37 36 5.2

fat (ram)

Shoulder

20 20 21 22 22 22 4.5

181'2'3 173 182"3 201 20 ~'2 191"2 3.2

fat (ram)

Mid-loin

fat (ram)

Mid-back

3.1' 3.6~ 3.7~ 2.9~ 3.5~ 5.32 1.9

wt. (g)

Ovarian

802 822 473 I13 ~ I19 ~ 602,3 32.7

wt. (g)

Uterine

The effect o f implantation with oestradiol and progesterone, testosterone or trenbolone acetate or with trenbolone acetate alone on growth rate, carcass characteristics and reproductive organs o f gilts (on-farm trial)"

TABLE 4

t,O

Z

M

rn

Z

O

t~

8t -

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P.J. SHERIDANET AL.

mg oestradiol- 17,8 plus 140 mg trenbolone acetate had consistently lower fat measurements than gilts on all other treatments at shoulder, mid-back and mid-loin areas. However, differences (P< 0.05 ) from the control group were detected only in the mid-back area. Ovarian weights of implanted gilts were lower (P< 0.01 ) than those of controis (Table 4). Uterine weights of gilts implanted with oestradiol plus progesterone or oestradiol plus testosterone were higher (P< 0.01 ) than controls or those on any other treatment. Uterine weights of gilts treated with trenbolone acetate were lower than those on any other treatment (P< 0.05 ) but not different from the control group. Boars There was no difference (P> 0.05 ) between the various treatments for finishing weight, carcass weight or average daily gain of boars (Table 5). The mean testicular length, circumference and weight of testes of boars implanted with 20 mg oestradiol-17p plus 140 mg trenbolone acetate were lower (P< 0.01 ) than those of testes from boars assigned to any other treatment (Table 6 ). Castrates There was no difference (P> 0.05 ) between treatments for daily liveweight gain, final liveweight or carcass weight of castrates. Pigs implanted with 10 mg oestradiol benzoate plus 100 mg testosterone propionate had consistently lower shoulder, mid-back and mid-loin fat measurements than pigs from any of the other treatments (Table 7). Significant differences were found only in TABLE 5 The effect of implantation with oestradiol and progesterone, testosterone or trenbolone acetate on performance and carcass characteristics of intact male pigsa Treatment 10 mg OB+ 100mgPros. 20 mg OB + 200mgProg. 10 mg OB+ 100 mgTP 20 mg OB + 200 mg TP 20 ms O-17p 140mgTBA Control RSD

n

Final wt. ADG Number Carcass wt. Shoulder (kg) (g) slaughtered (kg) fat (mm)

Mid-back Mid-loin fat (mm) fat (mm)

24 81.3

750

23

59.7

34

18

18

23 82.7

780

22

60.4

33

18

18

23 82.0

760

18

59.1

34

17

18

22 80.9

760

17

60.9

34

18

18

23 82.4 23 83.5 7.5

770 770 90

22 20

60.4 61.2 5.2

33 34 4.1

17 19 3.6

18 19 4.0

"Abbreviations and superscripts as in Table 1.

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TABLE 6 The effect of implantation with oestradiol and progesterone, testosterone or trenbolone acetate on mean testicular length, circumference and weighta Treatment

n

Mean testicular length (cm)

Mean testicular circumference (cm)

Mean testicular weight (g)

10 mg O B + 100 mg Prog. 20 mg OB + 200 mg Prog. 10 mg O B + 100 mg TP 20 mg O B + 2 0 0 mg TP 20 mg O- i 7//+ 140 mg TBA Control RSD

23 21 19 18 20 21

16.8 ~ 16.1 ' 15.91 16.2' 13.02 17.0' 2.0

9.9' 10.0' 9.3' 9.7' 7.62 10.1 t 1.2

170' 156 152' 153' 902 174' 48.8

aAbbreviations and superscripts as in Table I. TABLE 7 The effect of implantation with oestradiol and progesterone, testosterone, or trenbolone acetate on performance and carcass characteristics of castrated male pigs" Treatment 10 mg O B + 100 mg Prog. 20 mg O B + 200 mg Prog. 10 mg O B + 100 m g T P 20 mg OB + 200 mg TP 20 mg O-17//+ 140 mg TBA Control RSD

n

Final wt. ADG Number Carcass wt. Shoulder (kg) (g) slaughtered (k_g) fat (ram)

Mid-back Mid-loin fat (ram) fat (ram)

22 81.3

710

17

62.1

35

20

201'2"3

22 82.5

720

20

62.3

36

30

23"2

22 77.8

680

18

59.0

33

19

193

24 81.2

700

22

61.4

35

19

202,3

23 81.4 23 82.5 7.7

710 700 80

21 20

60.8 61.7 5.9

34 36 4.6

20 21 3.1

21 t'2"3 23 ~ 4.1

aAbbreviations and superscripts as in Table 1.

the mid-loin fat measurements of both groups given oestradiol and testosterone when compared with those of the control group (P< 0.05 ). DISCUSSION

Weight gains There were no significant improvements in average daily gains, finishing

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weights or carcass weights of boars, castrates or gilts implanted with anabolic steroids. This is in agreement with the findings of Beacom ( 1963 ) who worked on gilts, Woehling et al. ( 1951 ), Pearson et al. (1952), Sleeth et al. (1953) who worked on gilts and castrates and Thrasher et al. (1959) who worked on boars. However, Heitman and Clegg (1957) found that implantation of gilts with diethylstilboestrol (DES) had an adverse effect on average daily gain and DeWilde and Lauwers (1984) reported that hormone implants adversely affected the growth rate of boars and castrates whilst they had a positive effect on the liveweight gain of gilts. Feed conversion ratio

In the initial trial, where feed conversion ratios were measured, gilts implanted with 20 mg oestradiol plus 140 mg trenbolone acetate had significantly improved feed conversion ratios (P< 0.05) compared with controls. The other implant treatments employing oestradiol or testosterone had no significant effects or feed conversion ratio. This is in agreement with the findings of Woehling et al. (1951) who also failed to observe differences in feed conversion ratios when oestradiol and testosterone implants, either alone or in combination, were used. The improved feed conversion ratio noted by Heitman and Clegg (1957) in gilts implanted with DES was related to a decreased feed intake. Although DeWilde and Lauwers (1984) reported improved feed conversion ratios in gilts implanted with 20 nag oestradiol plus 140 mg trenbolone acetate their findings were not significant. They did find however that castrated pigs implanted with 20 mg oestradiol plus 140 mg trenbolone acetate had significantly improved feed conversion ratios, whilst castrates implanted with 20 nag oestradiol plus 200 mg testosterone showed no improvement in feed conversion. Vernon and Buttery (1976, 1978a,b) found that female rats treated with trenbolone acetate had significantly decreased rates of protein degradation and synthesis. Reduction in the rate of degradation was greater than the reduction in the rate of synthesis. Thus, the net effect was an increase in protein deposition. Reduction in the overall protein turnover would also improve feed conversion efficiency as protein turnover is an energetically expensive process. This could explain the improved feed conversion efficiency in the group of gilts which were implanted with trenbolone acetate. Carcass characteristics

The only significant effects of anabolic steroid implants on carcass characteristics of growing gilts were a decreased backfat thickness in the mid-back region of gilts implanted with 20 nag oestradiol plus 140 mg trenbolone acetate and in the mid-loin region of gilts implanted with 10 mg oestradiol plus

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100 nag testosterone. Other workers (Woehling et al., 1951; Pearson et al., 1952; Sleeth et al., 1953; Heitman and Clegg, 1957; DeWilde and Lauwers, 1984) found that only implants containing synthetic male hormones had any effect on the carcass characteristics of gilts. The decrease in mid-loin fat in gilts implanted with 10 mg oestradiol plus 100 mg testosterone is in conflict with the findings of other workers, whereas the decrease in baekfat noted in gilts implanted with oestradiol and trenbolone acetate was also observed by DeWilde and Lauwers (1984), but as in our experiments this response was not consistent. Implanting boars with anabolic steroids had no significant effect on carcass characteristics. This is in agreement with the findings of Thrasher et al. (1959) and Newell and Bowland ( 1972 ). DeWilde and Lauwers (1984) observed a decrease in backfat thickness in boars implanted with oestradiol and trenbolone acetate in one trial. However, this was also associated with a significant decrease in liveweight gain and there was no effect on fat:lean ratio in the carcass. Implanting castrated male pigs with anabolic steroids resulted in a decreased backfat thickness only in the mid-loin region of pigs implanted with 20 mg oestradiol plus 200 mg testosterone. In experiments carried out by DeWilde and Lauwers (1984) no anabolic steroid had any effect on back-fat thickness. However, these authors took an average of the three backfat measurements rather than assessing individual points as in this investigation. VanWeerden and Grandadam (1976) recorded a decrease in the backfat of castrates implanted with oestradiol and trenbolone acetate. This may be explained by the fact that their animals were on a different dietary regimen to those in the present experiment.

Reproductive organs No adverse or abnormal sexual behaviour was evident in gilts after implanting. By Day 3, gilts implanted with oestradiol and progesterone showed enlargement and reddening of the vulva which was maintained for the duration of the trial. This served as an indicator that there was a physiological release of hormone from the implants. Slight reddening of the vulva was also noted in gilts implanted with oestrogen and testosterone, over the first 6 days, after which the vulva became more infantile, thereby suggesting that the presence of male hormones may have reduced circulating oestrogens, presumably owing to its negative feedback effect on gonadotrophin release. In both trials, the weights of the ovaries of the control gilts were higher (P < 0.01 ) than those of the implanted gilts, again presumably because of inhibition of LH and FSH secretion by steroids from the implants. Trenbolone acetate may also inhibit or decrease episodic release of LH and this would explain the significantly reduced weights of ovaries of gilts implanted with

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trenbolone acetate alone in the on-farm trial. Support for this hypothesis is found in the findings of Gettys et al. (1984) where they demonstrated that trenbolone acetate prevented a post-castration rise in LH in acutely castrated bulls. In both trials, gilts implanted with oestradiol benzoate plus progesterone, or oestradiol plus testosterone had uteri of heavier weight than the control group. Although the differences were significant in the on-farm trial (P<0.01), in the initial trial they were significant (P<0.05) only for the group implanted with 10 mg oestradiol benzoate plus 100 mg progesterone. The increased weight of uteri in these groups could be explained by the uterine response to high circulating levels of oestrogens. Gilts implanted with oestradiol plus trenbolone acetate did not exhibit such an increase in uterine weight. This may be caused by a direct effect of trenbolone acetate on the uterus inhibiting the uterine response to oestrogens or, to an inhibitory effect of trenbolone acetate on gonadotrophin release, which in turn would cause a decrease in the production of endogenous oestrogens. As the intact male pig produces large quantities of male (Booth, 1975) and female (VeUe, 1958) hormones, it is not surprising that supplementation of the high levels of endogenous hormones produces no further anabolic effect. However, analysis of the testicular parameters measured indicates that implanting with 20 mg oestradiol- 17fl plus 140 mg trenbolone acetate was highly effective in reducing testicular size at slaughter. The testes of boars implanted with this combination had lower (P< 0.01 ); mean length, maximum circumference and weight. Echternkamp et al. (1969) reported that 96 mg of DES implanted at 70 kg liveweight caused a decrease in weight of the testes and accessory sex glands. Echternkamp et al. (1969) also reported atrophy of the Leydig cells of the testes following DES implantation. Palmer et al. ( 1971 ) concluded that early implanting with DES (20 days of age), caused delay in the development of Leydig cells and delayed attainment of sexual maturity by 20 days. Taste panel evaluation of meat from boars which had been implanted with 96 mg DES at 70 kg liveweight consistently resulted in lower odour and taint intensities for the implanted boars (Teague et al., 1964; Echternkamp et al., 1969; Plimpton et al., 1971 ). This suggests that reduction in the testicular size of boars implanted with 20 mg oestradiol- 17p plus 140 mg trenbolone acetate may be accompanied by a reduction in boar taint. A suggested mechanism would be that the combination of oestradiol and trenbolone acetate retards the pulsatile secretion of LH, thereby causing atrophy of Leydig cells and decreased production of testosterone and androstenedione by the testis. However, further studies involving taste panel evaluation of the meat from implanted boars, and hormonal analysis of a series of blood samples taken during the fattening period are required to elucidate the mode of action and the value of hormonal implants in reducing boar taint. Pigs used in this experiment were fed to appetite whereas ad libitum feed-

ANABOLIC AGENTS IN PIGS: GROWTH AND REPRODUCTIVE ORGANS

273

ing was used in experiments where significant improvements in performance and carcass characteristics were obtained. These findings suggest that restriction of the diet of castrates is as effective in improving carcass characteristics as implanting those on an ad libitum diet; it makes more economic sense and avoids the risks of hormonal residues. ACKNOWLEDGEMENTS

The authors wish to acknowledge financial support obtained from HKM Milking Ltd., and the valued assistance of Denis Kelliher, M.V.M.M.R.C.V.S., Diarmuid O'Callaghan, B.Agr.Sc., M.An.Sc., Dan Prcndiville and Matt Daly without whom this work could not have been cffectcd.

REFERENCES Beacom, S.E., 1963. The effect of diethylstilboestrol and estradiol-testosterone implants on rate and efficiency of gain and on carcass quality of market pigs fed different finishing diets. Can. J. Anim. Sci., 43: 374-384. Booth, W.D., 1975. Changes with age in the occurrence of C19 steroids in the testis and submaxillary glands of the boar. J. Reprod. Fertil,, 42: 459-472. Cahill, V.R., Teague, H.S., Kunkle, L.E., Moxon, A.L. and Rutledge, E.A., 1960. Measurements of and ways of affecting sex influenced performance of growing-finishing swine. J. Anita. Sci., 19: 1036-1040. DeWilde, R.O. and Lauwers, H., 1984. The effect of parenteral use of estradiol, progesterone, testosterone and trenbolone on growth and carcass composition in pigs. J. Anita. Sci., 59: 1501-1509. Duncan, D.B., 1955. Multiple range and multiple F tests. Biometrics, 11: 1-42. Echternkamp, S.E., "league, H.S., Plimpton, R.F. and Grifo, A.P., 1969. Glandular development, hormone response and boar odour and flavour intensity of untreated and diethylstilboestrol implanted boars. J. Anim. Sci., 28: 653-658. Fowler, V.R., Taylor, A.G. and Livingstone, R., 1969. Nutritional implications of differences in tissue growth due to sex. In: Meat Production from Entire Male Animals. Churchill, London, pp. 51-61. Galbraith, H. and Topps, J.H., 1981. Effect of hormones on growth and body composition of animals. Nutr. Abstr. Rev., 51:521-540. Gettys, T.W., D'Occhio, M.J., Henricks, D.M. and Schanbacher, B.D., 1984. Suppression of LH secretion by oestradiol, dihydrotestosterone and trenbolone acetate in the acutely castrated bull. J. Endocrinol., 100:107-112. Hansson, I., Lundstrom, K. and Malmfors, B., 1975. Effect of sex and weight on growth, feed efficiency and carcass characteristics of pigs II: Carcass characteristics of boars, barrows and gilts slaughtered at four different weights. Swed. J. Agric. Res., 5: 69-80. Harvey, W.R., 1960. Least squares analysis of data with unequal subclass frequencies. USDA, ARS Bull., 20 p. 8 (mimeo.). Heitman, H. and Clegg, M.T., 1957. Subcutaneous stilboestrol implantation in growing-fattening swine. J. Anita. Sci., 16: 901-910. Newell, J.A. and Bowland, J.P., 1972. Performance, carcass composition and fat composition of boars, gilts and barrows fed two levels of protein. Can. J. Anita. Sci., 52:543-551.

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Palmer, W.M., Teague, H.S. and Grifo, A.P., 1971. Effect ofdiethylstilboestrol implantation on testicular development in the boar. J. Anim. Sci., 32: 525-530. Pearson, A.M., Combs, G.E., Wallace, H.D., Sleeth, R.B., Stroud, J.W., Shepherd, J.M. and Koger, M., 1952. The effects of stilboestrol implants on swine of different sexes. J. Anita. Sci., 11: 251-260. Plimpton, R.F., Ockerman, H.N., Teague, H.S., Grifo, A.P. and Cahill, V.R., 1971. Influence of the time following diethylstilboestrol implantation on the palatability, composition and quality of boar pork. J. Anim. Sci., 32:51-56. Sleeth, R.B., Pearson, A.M., Wallace, H.D., Voropf, D.H. and Koger, M., 1953. Effect of injection of testosterone, oestradiol and a combination of the two upon growing-fattening swine. J. Anita. Sci., 12: 322-330. Teague, H.S., Plimpton, R.F., Cahill, V.R., Grifo, A.P. and Kunkle, L.E., 1964. Influence of DES implantation on growth and carcass characteristics of boars. J. Anita. Sci., 23: 332-338. Thrasher, G.W., Perry, T.W., Andrews, F.N., Beeson, W.M. and Stob, M., 1959. The effect of oestrogenic and androgenic compounds upon growth and carcass composition of swine. J. Anita. Sci., 18: 399-409. VanWeerden, E.J. and Grandadam, J.A., 1976. The effect of an anabolic agent on N-deposition, growth and slaughter quality in growing castrated male pigs. In: F.C. Lu and J. Rendel (Editors), Anabolic Agents in Animal Production. Suppl. V., Thieme, Stuttgart, pp. 115-122. Velle, W., 1958. Further studies on urinary oestrogen excretion by the boar. Acta Endocrinol., 29: 395-400. Vernon, B.G. and Buttery, P.J., 1976. Protein turnover in rats treated with trienbolone acetate. Br. J. Nutr., 36: 575-579. Vernon, B.G. and Buttery, P.J., 1978a. Protein metabolism of rats treated with Trienbolone acetate. Anim. Prod., 26: 1-9. Vernon, B.G. and Buttery, P.J., 1978b. The effect of Trienbolone acetate with time on the various responses of protein synthesis in the rat. Br. J. Nutr., 40: 563-572. Woehling, H.L., Wilson, G.D., Grummer, R.W., Bray, R.W. and Casida, L.E., 1951, Effects of stilboestrol and testosterone pellets implanted into growing-fattening pigs. J. Anita. Sci., l 0: 889-892. RESUME Sheridan, P.J., Austin, F.H., Bourke, S. et Roche, J.F., 1990. Effet d'agents anabolisants sur la vitesse de croissance et les organes sexuels chez le pore. Livest. Prod. Sci., 26:263-275 (en anglais). Cette ~tude avait pour but de d6terminer les effets d'implants de st~ro'ides anabolisants sur la vitesse de croissance, les caract6ristiques de carcasse et les organes sexuels chez le pore en croissance. Trois cent quatre porcs crois6s m~les entiers, m~les castr~s et femelles aliment~s/l volont~ ont requ des implants de st6roides a 35-40 kg de poids vif, ont 6t6 abattus/L 75-80 kg. Les porcs ont ~t~ trait~s avec de l'ac6tate d'oestradiol et de la progest6rone ou de la testost6rone, ou de l'ac6tate de trenbolone. Darts I¢ cas des femelles, un lot suppl~mentaire ne recevait que de l'ac~tate de trenbolone. La vitesse de croissance, l'efficacit~ alimentair¢ et le poids de la carcasse et des organes g6nitaux de ces animaux ont 6t~ enregistr6s. Les implants n'ont aucun effet sur la vitesse de croissance et le poids de carcasse des animaux. L'indice de consommation et l'6paisseur de lard dorsal sont r~uits ( P < 0,05) chez les femelles ayant des implants de 20 mg d'oestradiol + 140 mg d'ac6tate de trenbolone. L'~paissuer de lard au niveau du rein est diminu6e ( P < 0,05) chez les castr6s avec des implants de 10 mg d'oestradiol + 100 mg de testost6rone. Les caract6ristiques de carcasse des pores m~les entiers ne sont

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pas affectdes par les implants. Tousles implants abaissent le poids des ovaires (P< 0,05) et, sauf pour ceux rcnfermant de l'achtatc de trenbolonc, augmcntent lc poids de l'utdrus (P< 0,05 ). La longucur, la circonf6rcnce et le poids des testicules sont diminuds par los implants renfermant de l'acdtate de trenbolone (P< 0,01 ). Lcs stdro~'desanabolisants ne semblcnt pas ~tre des agents approprids pour amdliorer la croissance et lcs caract6ristiques de carcasse chez le porc. KURZFASSUNG Sheridan, P.J. Austin, F.H., Bourke, S. und Roche, J.F., 1990. Der Effect von Anabolika aufdas Wachstum und die Fortpflanzungorgane von Schweinen. Livest. Prod. Sci. 26:263-275 (auf englisch ). Dreihundertundvier Hybrid schweine wurden bei 35-40 kg implantiert und nach Appetit gefutten, sodann bei 75-80 kg geschlachtet. Ebern und Kastraten wurde Ostradiol sowie entweder Progesteron, Testosteron oder Trenbolon verabreicht, die Jungsauen wurden entsprechend behandelt und vine weitere Gruppe erhielt lediglich Trenbolon. Wachstum, Futterverwertung Schlachtgewicht sowie das Gewicht der Fortplanzungsorgane wurden aufgezeichnet. Es ergaben sich keine Unterschicde in der Wachstumsrate (P> 0.05) der durchschnittlichen taglichen Gewichtszunahme sowie dem Schlachtgewicht. Die Futterverwertung der mit 20 mg Ostradiol 17B+ 140 mg Trenbolonazetat implanteinen Jungsauen war besser (P<0,05), und die Riickenspeckmasse waren in Versuch 2 abwichend (P< 0,05 ). Bei den mit 10 mg (~stradiolbenzoat + 100 mg Testosteronpropionat behandelten Kastraten waren die Lendenspeckmasse reduziert (P < 0,05 ). Am Auffallendsten war die Wirkung auf die Fortplanzungsorgane. Bei den Jungsauen waren die Eierstockgewichte der Kontrolltiere grSsser (Testgruppe l P < 0,05 und Testgruppe 2 P< 0,01 ) als bei irgendeiner tier implantierten Gruppen. Das Uterusgewicht der mit l0 mg Ostradiolbenzoat+ 100 mg Progesteron implantienen Jungsauen war h6her als bei den Kontrolltieren (P< 0,05 Testgruppe und P0,01 Testgruppe 2), das gleiche gilt f'tir die in Test 2 mit uOstradiol+ Testosteron implantierten Tiere. Die durchschnittliche Hodenl~inge, sowie Umfang und Gewicht der Hoden von Ebern, die mit 20 mg Ostradiol 17B + 140 mg Trenbolonazetat implantiert wurden, waren geringer als die MaBe der Kontrolltiere oder irgendeiner der anderen behandelten Gruppen (P< 0,01 ).