Effects of recombinant porcine somatotropin on growth and carcass traits in meishan pigs

Livestock Production Science, 27 ( 1991 ) 211-218

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Elsevier Science Publishers B.V., Amsterdam

Effects of recombinant porcine somatotropin 1 on growth and carcass traits in Meishan pigs H.A.M. van der Steen 2, J. van Dijk, P.N. de Groot and E. Kanis Department of Animal Breeding, Wageningen Agricultural University P.O. Box 338, 6700 AH Wageningen, Netherlands (Accepted 1 May 1990)

ABSTRACT Van der Steen, H.A.M., van Dijk, J., de Groot, P.N. and Kanis, E., 1991. Effects of recombinant porcine somatotropin on growth and carcass traits in Meishan pigs. Livest. Prod. Sci., 27:211-218. Effects of recombinant porcine somatotropin ( rpST ) on growth, feed intake, feed conversion, backfat thickness and lean percentage were examined in growing Meishan pigs. The experiment comprised 42 barrows of which 20 were administered 14 mg rpST twice a week i.m., starting at 40 kg, the others received a placebo. Pigs were fed ad libitum a diet containing 9.2 MJ net energy and 156 g crude protein kg- ~and were slaughtered at 90 kg liveweight. From 40 to 90 kg liveweight, rpST effects were: daily gain + 17.9%; feed intake - 5.1%; feed conversion - 17.5%; backfat thickness - 29.8%; lean percentage + 16.0%. The effects of rpST in Meishan are much larger than in a similar experiment with leaner western pigs. Development of synthetic breeds with Meishan in combination with the use of rpST in cross-bred fattening pigs may be a way to economically exploit the high fertility of Meishan. Keywords: body composition; Meishan; pigs; porcine somatotropin; production traits.

INTRODUCTION

Chinese Meishan pigs are interesting for pig-breeding organizations as reproductive traits are superior to those of western breeds. Development of synthetics with Meishan will result in dam lines with good reproductive performance but rather poor growth and carcass traits. This disadvantage may be overcome to a large extent by use of recombinant porcine somatotropin (rpST) for cross-bred fattening pigs. The effects of exogenous somatotropin on production traits in growing swine have been the subject of many studies. In American pigs treated with soma~Recombinant porcine somatotropin was provided by Pitman-Moore Inc., Terre Haute, IN, USA. 2present address: Pig Improvement Company, Fyfield Wick, Abingdon, Oxfordshire, OX 13 5NA, UK.

0301-6226/91/$03.50

© 1991 - - Elsevier Science Publishers B.V.

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H.A.M. VAN DER STEEN ET AL.

totropin, Chung et al. ( 1985 ), Boyd et al. ( 1986 ), Kraft et al. (1986), Etherton et al. (1986a,b, 1987), McLaren et al. (1987), Campbell et al. (1988) and Bryan et al. ( 1989 ) found increases in growth and decreases in feed conversion. In some studies (Wolfrom et al., 1986; Smith et al., 1987 ) daily gain decreased or was unaffected. Feed intake decreased or did not change significantly in each of these studies. In German Pietrain pigs, which are considered to be very lean, no effect on any of these traits was significant (Hiister et al., 1988). Kanis et al. (1990) studied effects in three genotypes and slaughtered at 100 or 140 kg liveweight. Growth performance improved more in Fl (Dutch Yorkshire X Dutch Landrace) and Pietrain than in the fatter Duroc. It was concluded that, at higher weights, the improvement in growth and feed conversion is largest in lean animals. Additionally, most studies show a marked decrease in fat and increase in lean muscle in the carcass. Kanis et al. (1990) showed that effects of rpST on backfat thickness and lean percentage were greater for fatter pigs. The aim of the current study was to examine the effects of chronic rpST administration on growth, feed intake, backfat thickness and lean percentage in growing Meishan barrows. MATERIALS AND METHODS

Effects of rpST on growth and carcass traits were estimated in two batches of 10 and 32 Meishan barrows, respectively. Pigs were housed and fed individually. The composition of the diet during the treatment period is given in Table 1. The diet contained 9.2 MJ net energy, 156 g crude protein, 7.3 g digestible lysine, 4.7 g digestible methionine and cysteine, 6.1 g Ca and 4.4 g P kg -~. Pigs had free access to water. The rpST treatment consisted of i.m. administration of 14 mg twice a week in the neck region, alternating on the left and the right side. Administration of rpST or placebo started at an approximate weight of 40 kg liveweight and was continued until 4.5 days before slaughter at 90 kg liveweight. The rpST and control group consisted of 20 and 22 barrows, respectively. Liveweight and ad libitum feed intake were measured weekly from on average 17 kg to slaughter weight. Backfat thickness was measured ultrasonically at 40 kg and at slaughter weight. The backfat score was the mean of four measurements on each side of the animal's back, according to the method described by Kroeske et al. (1968). Animals were fasted half a day before slaughtering, which occurred once a week according to the rules for European export slaughter houses. Cold right carcass halves were dissected according to a standard method described by Bergstrrm and Kroeske ( 1968 ). Lean percentage was calculated as the sum of the weights of the trimmed, but not deboned, right-hand-side ham, cutlets, shoulder and meat scraps divided by the weight of the right half of the carcass times one hundred. Fat percentage was calculated in a comparable way and was based on belly, chin, back fat, fat

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EFFECTS OF rpST ON MEISHAN PIGS

TABLE 1 Composition of diet ~ Ingredient

% by weight

Peas Extracted soy bean meal (43.5% crude protein ) Corn gluten feed Tapioca Extracted rape seed meal Alfalfa meal Sugarcane molasses Animal meal Animal fat Monocalcium phosphate Salt Mineral + vitamin mixture 2 Mixture 3

11 14.9 15 38.7 3 3 7 2.8 3.0 0.2 0.2 0.5 0.7

~Calculated: dig. lysine 0.73%; dig. methionine+cysteine 0.47%; net energy for pigs 9.2 MJ k g - t crude protein 15.6%; Ca 0.61%; P 0.44%. 2Mineral + vitamin mixture contained: Ca 29.4%; Fe 16 000 mg kg- 1; Zn 9000 mg kg- '; Mn 4800 mg kg- '; Co 30 mg kg- '; 1 80 mg kg- ~; Se 20 mg kg- t; Cu 4000 mg kg- l; vit. A 1 000 000 IU kg- ~; vit. D 3 200 000 | U kg- ~; vit. B2 700 mg kg- '; niacin 3600 mg kg- '; pantothenic acid 1000 mg kg- '; vit. B~2 3 mg kg- ~; vit. E 1500 mg kg- '; vit. K 80 mg kg- '; tylosin 4000 mg kg- '; dl-methionine 6%. 3Mixture contained: Ca 15%; P 10%; dl-methionine 10%.

meal and flare fat. The growth performance traits daily gain, feed intake and feed conversion ratio were calculated over the liveweight ranges from approximately 17 to 40 kg and 40 kg to slaughter weight. Data were first analysed with SAS GLM Type III (SAS Institute Inc., 1985 ), with a model comprising main effects and covariables. Interaction between main effects was not significant ( P > 0.05 ) and final least squares means are estimated in the model: Y,jk = ~ + B~ + Tj + covariables + e,jk

( 1)

where Yijk = characteristic of animal k of treatment j and batch i /z = general mean B, = fixed effect ofbatch i ( i = 1,2) Tj = fixed effect of treatment j ( j = 1,2 ) eijk = random e r r o r Covariables were overall (Model I a ) or within treatment (Model l b ). Covariables were: (i) weight at start of the pretreatment period (WPT) for feed intake (FIp), daily gain ( D G p ) and feed conversion (FCp) before 40 kg; (ii) weight at start of the treatment (WST) for feed intake (Fit), daily gain

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(DGt) and feed conversion (FCt) from 40 to 90 kg and backfat thickness at 40 kg (BFT40); (iii) backfat thickness at 40 kg and carcass weight (WCC) for lean percentage (%LEAN) and fat percentage (%FAT); (iv) backfat thickness at 40 kg and weight at slaughter (WSL) for backfat thickness at 90 kg (BFT90). Covariables were included in the model to correct for variation in weight at start of the pretreatment and treatment period and at slaughter as these weights were not exactly 17, 40 and 90 kg, respectively, for both treatment groups. Lean percentage, fat percentage and backfat thickness at 90 kg were also corrected for backfat thickness at 40 kg as the control group was slightly, although not significantly, leaner than the rpST group at start of the treatment period. RESULTS

No differences were apparent between rpST-treated and control animals in health status and carcass abnormalities. Means and standard deviations of traits for both treatment groups are in Table 2. Table 3 lists the least squares means of growth traits during the pretreatment period and of backfat thickness at start of treatment. As expected no differences between least squares means of treatment were significant. At start of the treatment period rpST TABLE2

Means and standard deviations per treatment group Trait

W P T (kg) W S L (kg) W C C (kg) D G p (g d a y - ~) DGt (gday -~) Fip (kg day-~ ) Fit (kg day -~ ) FCp (kg kg-~ ) FCI (kg kg- ~) BFT40 ( mm ) BFT90 (mm) %FAT (%) %LEAN (%)

Control

% diff.

rpST

Mean

SD

Mean

SD

17.1 87.7 66.0 547 531 1.49 2.12 2.75 4.04 14.4 27.4 51.2 37.4

3.2 1.5 1.9 94 98 0.24 0.32 0.30 0.30 1.9 4.3 3.1 2.3

16.0 90.1 65.2 564 619 1.48 2.01 2.69 3.36 15.3 20.8 44.4 43.3

3.3 3.4 2.8 149 124 0.28 0.20 0.36 0.54 2.7 3.6 2.6 1.9

+ 16.6 -5.2 - 16.8 - 24.1 - 13.3 + 15.8

W P T = weight at start of the pretreatment period; W S L = weight at slaughter; W C C = carcass weight; D G p , DGt, FIp, Fit, FCp, FCt = daily gain, feed intake and feed conversion ratio during pretreatment and treatment period, respectively; BFT40 and BFT90 = backfat thickness of 40 and 90 kg, respectively.

EFFECTS OF rpST ON MEISHAN PIGS

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TABLE3 Least squares means of feed intake, daily gain and feed conversion during the pretreatment period and backfat thickness at initiation of treatment for both treatment groups (Model la) Trait

FIp I (kg day-1 ) DGp ( kg d a y - J ) FCp (kg kg-~ ) BFT40 ( m m )

Least squares means

Significance

Covariable

0.28 0.12 0.48 0.46

WPT WPT WPT WST

(/')

Control

rpST

1.45 535 2.73 14.3

1.50 581 2.65 14.8

~For explanation of abbreviations, see Table 2. TABLE 4 Least squares means (Model l b ) of feed intake, daily gain, feed conversion ratio during treatment, backfat thickness, fat percentage, lean percentage and organ weights at slaughter for both treatment groups and significance of treatment ( T ) effects (Model la) Trait

Fit ~ (kg day -] ) DGt (g day-~ ) FCt (kgkg -~ ) BFT90 ( m m ) %FAT (%) %LEAN (%) Heart (g) Kidney (g) Liver (g) Spleen (g) Skin ( m m )

Least squares m e a n s T Control

rpST

2.15 532 4.07 28.5 51.3 37.5 246 287 1273 101 7.11

2.04 628 3.36 20.0 44.4 43.4 300 387 1776 138 8.15

%diff.

Significance (P)

Covariable(s)

-5.1 + 17.9 -17.5 -29.8 - 13.5 + 16.0 +21.6 +34.8 +39.5 +35.9 +16.1

0.207 0.009 <0.001 <0.001 <0.001 <0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001

WST WST WST BFT40, WSL BFT40, WCC BFT40, WCC WSL WSL WSL WSL WSL

~For explanation of abbreviations see Table 2.

animals had more backfat than control animals ( + 0.9 m m ) . After correction for body weight the difference was only 0.5 mm. Table 4 lists least squares means of growth and carcass traits and weights of organs per treatment. There appears to be a significant effect of treatment on all traits ( P < 0.05 ) but feed intake. Treatment with rpST promotes daily gain, improves feed conversion, lowers backfat thickness and increases lean percentages and weight of organs. DISCUSSION

Results of the present experiment can to some extent be compared with results from Kanis et al. (1990) as the experiments were carried out at the

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TABLE 5 Least squares means of daily gain, feed intake, feed conversion ratio, backfat thickness and lean percenlage for Meishan and European breeds Trait

DGt ~ (gday -~) Fit (kg day -~ ) FCt BFT90/100 ( m m ) %LEAN (%)

Meishan

European:

% diff.

Control

rpST

% diff.

Control

rpST

532 2.15 4.07 28.5 37.5

628 2.04 3.36 20.0 43.4

+17.9 -5.1 -17.5 -29.8 + 16.0

945 3.14 3.35 15.6 53.8

1012 3.01 3.00 13.2 56.8

+7.1 -4.2 -10.5 - 15.3 +5.6

~For explanation of abbreviations see Table 2. 2From Kanis et al. (1990).

same research farm and the experimental designs were similar. The difference involved the treatment period (40-90 kg and 60-100 kg for Meishan and European breeds, respectively), feed protein level and year-season (start of experiment in October 1987 and March 1988, respectively). Results for barrows are summarized in Table 5. In both experiments rpST administration resulted in an increased daily gain and decreased feed intake and feed conversion. Backfat thickness decreased and lean percentage was elevated. Meishan barrows showed larger improvements in growth and carcass traits than European barrows. This was especially the case for backfat thickness ( - 29.8 vs. - 15.3%) and lean percentage ( + 16.0 vs. + 5.7% ). Effects of rpST are related to the degree of fatness of the breed. Also McLaughlin et al. ( 1989 ) found responses in Chinese Beijing Black hogs (a composite of a local Chinese, Berkshire and Yorkshire breeds) that were at least as large as those for American breeds. Beijing Black hogs are however not as fat as Meishan barrows. Data suggest that in a composite of Meishan and European breeds relatively large effects of rpST can also be expected. In both experiments the dose was fixed at the equivalent of 4 mg day-t animal- 1 throughout the test period. This dose is similar to that in many other experiments. However, rpST was administered not daily but twice a week. This might have had a diminishing effect compared with results in the literature cited (Kanis et al., 1990). It is of interest to compare the difference between the Meishan and European control group with the effect of rpST treatment in Meishan barrows. The effect of rpST in Meishan was 23, 36, 66 and 99% of the breed difference in the control groups for daily gain, lean percentage, backfat thickness and feed conversion ratio, respectively. Development of synthetics with Meishan is a possible way to exploit the good reproductive performance of this Chinese breed. The rather poor growth

EFFECTS OF rpST ON MEISHAN PIGS

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and carcass traits may be overcome to a large extent by use of recombinant porcine somatotropin (rpST) for cross-bred fattening pigs. A synthetic line with 50% Meishan as one of the breeds to produce the crossbred commercial sow will result in a fattening pig with 12.5% Meishan genes. The relatively large effect of rpST treatment in these fattening pigs in combination with selection for lean percentage in the synthetic might result in an acceptable level of growth and carcass traits.

REFERENCES Bergstr~Sm, P.L. and Kroeske, D., 1968. Methods of carcass assessment in research on carcass quality in the Netherlands. I. Description of methods. Report C-123, IVO, Zeist and Proceedings of the 9th Annual Meeting of the Eur. Assoc. Anita. Prod., Dublin. Boyd, R.D., Bauman, D.E., Beerman, D.H., De Neergaard, A.F., Souza, L. and Butler, W.R., 1986. Titration of the porcine growth hormone dose which maximizes growth performance and lean deposition in swine. J. Anim. Sci., 63 (Suppl. 1 ): 218 (Abstract). Bryan, K.A., Hammond, J.M., Canning, S., Mondschein, J., Carbaugh, D.E., Clark, A.M. and Hagen, D.R., 1989. Reproductive and growth responses of gilts to exogenous porcine pituitary growth hormone. J. Anim. Sci., 67: 196-205. Campbell, R.G., Steele, N.C., Caperna, T.J., McMurtry, J.P., Solomon, M.B. and Mitchell, D., 1988. Interrelationships between energy intake and exogenous porcine growth hormone administration on the performance, body composition, and protein and energy metabolism of growing pigs weighing 25 to 55 kg live weight. J. Anim. Sci., 66:1643. Chung, C.S., Etherton, T.D. and Wiggins, J.P., 1985. Stimulation of swine growth by porcine growth hormone. J. Anim. Sci., 60:118. Etherton, T.D., Evock, C.M., Chung, C.S., Walton, P.E., Sillence, M.N., Magri, K.A. and Ivy, R.E., 1986a. Stimulation of pig growth performance by long-term treatment with pituitary porcine growth hormone (pGH) and a recombinant pGH. J. Anim. Sci., 63 (Suppl.. 1 ): 219 (abstract). Etherton, T.D., Wiggins, J.P., Chung, C.S., Evock, C.M., Rebhun, J.F. and Walton, P.E., 1986b. Stimulation of pig growth performance by porcine growth hormone and growth hormone releasing-factor. J. Anim. Sci., 63:1389. Etherton, T.D., Wiggins, J.P., Evock, C.M., Chung, C.S., Rebhun, J.F., Walton, P.E. and Steele, N.C., 1987. Stimulation of pig growth performance by porcine growth hormone: determination of the dose-response relationship. J. Anim. Sci., 64: 433. HiJster, E., Ekkel, D., Kallweit, E., Iv),, R.E. and Ellendorf, F., 1988. The use of recombinant porcine growth hormone to influence growth and body composition in pigs. Acta Endocrinol., 117 (Suppl. 287): 74 (abstract). Kanis, E., Nieuwhof, G.J., de Greef, K.H., van der Hel, W., Verstegen, M.W.A., Huisman, J. and van der Wal, P., 1990. Effect of recombinant porcine somatotropin on growth and carcass quality in growing pigs: interactions with genotype, gender and slaughter weight. J. Anim. Sci., 68:1193-1200. Kraft, L.A., Haines, D.R. and DeLay, R.I., 1986. The effects of daily injections of recombinant porcine growth hormone (rpGH) on growth, feed efficiency, carcass composition and selected metabolic and hormonal parameters in finishing swine. J. Anim. Sci., 63 (Suppl. 1 ): 218 (abstract). Kroeske, D., Buiting, G.A.J. and de Jong, G., 1968. Enkele criteria bij de bepaling van de slachtkwaliteit van varkens. Veeteelt Zuivelber., 11:153.

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McLaren, D.G., Grebner, G.L, Bechtel, P.J., McKeith, F.K., Novakofski, J.E., Easter, R.A., Jones, R.W. and Dalrymple, R.H., 1987. Effect of graded levels of natural porcine somatotropin (PST) on growth performance of 57 to 103 kg pigs. J. Anim. Sci., 65 (Suppl. 1 ): 245 (abstract). McLaughlin, C.L., Baile, C.A., Qi, S.Z., Wang, L.C. and Xie, J.P., 1989. Responses of Beijing Black hogs to porcine somatotropin. J. Anita. Sci., 67:116-127. SAS Institute Inc., 1985. SAS User's Guide: Statistics, Version 5 Edition. Cary, NC, p. 433. Smith, V.G., Moseley, W.M., Kasson, C.W. and Kratzer, D.D., 1987. Effect of exogenous recombinant bovine somatotropin (rbST) and porcine pituitary somatotropin (ppST) on growth performance of pigs. J. Anim. Sci., 65 (Suppl. 1 ): 243 (abstract). Wolfrom, G.W., Ivy, R.E. and Baldwin, C.D., 1986. Effect of native porcine growth hormone (npGH) injected intramuscularly in barrows. J. Anim. Sci., 63 (Suppl. 1 ): 219 (abstract). RESUME Van der Steen, H.A.M., van Dijk, J., de Groot, P.N. et Kanis, E., 1991. Effets de la somatotropine porcine recombinante sur la croissance et les caract6ristiques de la carcasse de porcs Meishan. Livest. Prod. Sci., 27:211-218 (en anglais). Les effets de la somatotropine porcine recombinante (rpST) sur la croissance, la consommarion, l'efficacit6 alimentaire, l'6paisseur de lard dorsal et la teneur en viande maigre ont 6t6 6tudi6s sur des porcs Meishan en croissance. L'exp6rience portait sur 42 m~les eastr6s, 20 d'entre eux recevant deux fois/semaine 14 mg de rpST par voie intramusculaire/l partir de 40 kg, les autres un placebo. Les porcs recevaient h volont6 un r6gime/l 9,05 MJ d'6nergie nette et 182 g de prot6ines brutes/kg et 6taient abattus/l 90 kg de poids vif. Les effets de la rpST entre 40 et 90 kg 6taient: + 17,5% pour la vitesse de croissance, - 5 , 1 % pour la consommation, - 17,5% pour l'indice de consommation, - 29,8% pour l'6paisseur de lard dorsal et + 16,0% pour le taux de viande maigre. Les effets de la rpST chez les Meishan sont beaucoup plus importants quc ceux observ6s au cours d'une exp6rience similaire sur des porcs occidentaux plus maigres. Le d6veloppement de races synth6tiques dans lesquelles entrerait la race Meishan combin6 h l'utilisation de la rpST chez les porcs crois6s engraiss6s pourrait constituer une mani6re 6conomique d'exploiter la fertilit6 61ev6e des Meishan. KURZFASSUNG Van der Steen, H.A.M., van Dijk, J., de Groot, P.N. und Kanis, E., 1991. Die Effekte des rekombinanten porcinen Wachstumshormons auf Merkmale der Mastleistung und des SchlachtkiSrperwertes bei Meishan-Schweinen. Livst. Prod. Sci., 27:211-218 (auf englisch). Bei wachsenden Meishan-Schweinen wurden die Effekte des rekombinanten porcinen Wachstumshormons auf Wachstum, Futteraufnahme, Futterverwertung, R~ickenspeckdicke und Fleischanteil untersucht. Das Experiment enthielt 42 B6rge, von denen 20 14 mg rpSTzweimal w6chentlich intramuskul~ir verabreicht wurden, beginnend mit 40 kg. Die Kontrollgruppe erhielt Placebos. Die Schweine wurden mit einer Digit von 9,05 MJ Nettoenergie und 182 g Rohprotein pro kg ad libitum gef'tittert und mit 90 kg Lebendgewicht geschlachtet. Von 40 bis 90 kg Lebendgewicht waren die rpST-Effekte: t~igliche Zunahme + 17,9%, Futteraufnahme - 5,1%, Futterverwertung - 17,5%, RiJckenspeckdicke - 29,8% und Fleischanteil + 16,0%. Mit Meishan-Schweinen sind die Effekte rpST wesentlich gr613er als in ~ihnlichen Experimenten mit fleischreicheren westlichen Schweinen. Die Entwicklung synthetischer Rassen mit Meishan in Kombination mit der Anwendung von rpST bei den Kreuzungsmastschweinen k6nnte ein 6konomischer Weg zur Ausnutzung der hohen Fruchtbarkeit der Meishan-Schweine sein.