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Adjustment factors for growth characters of the Damascus goat
Livestock Production Science, 10 (1983) 479--486 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
479
A D J U S T M E N T F A C T O R S FOR GROWTH CHARACTERS OF THE DAMASCUS GOAT
A.P. MAVROGENIS
Agricultural Research Institue, Nicosia (Cyprus) (Accepted 26 April 1983)
ABSTRACT
Mavrogenis, A.P., 1983. Adjustment factors for growth characters of the Damascus goat. Livest. Prod. Sci., 10: 479--486. Data on 1542 purebred Damascus kids obtained from the Goat Breeding Unit at Akhelia were used to determine the effects of year, m o n t h and type of birth (singles, twins, other multiples), sex of kid and dam lactation number on growth characters of goats. Least squares analyses showed that all factors studied had a significant effect on weaning weight, pre-weaning growth rate and 140-day weight (P<0.01). Type of birth and lactation number effects were small and insignificant for post-weaning growth rate. Adjustment factors were computed across year of birth for the effects of m o n t h of birth, type of birth, sex of kid and dam lactation number. These adjustment factors, although developed from a single herd, can be used, with some caution, in a breeding program for the improvement of Damascus goats. INTRODUCTION
Selection for superior breeding stock presumes that the procedures used in selection are adequate and accurate enough so that it can be based on genotypic rather than environmental merit. It is well d o c u m e n t e d that corrections for classifiable non-genetic sources of variation render selection and culling more accurate. Gjedrem (1965} and Fimland et al. {1969} have reported that 30--40% of the variation in weaning weight of lambs can be accounted for by environmental factors. The use of suitable adjustment factors for production characters is an important tool to the animal breeder and producer in general. Ideally, these adjustment factors should be developed for specific management systems, b u t sufficient data are rarely available. The Damascus goat is found in a n u m b e r of Middle East countries, and it is characterized b y high milk production and prolificacy (Louca et al., 1975; Hadjipanayiotou and Louca, 1976}. It is mostly exploited as a dual-purpose animal and kept under semi-intensive or intensive conditions where better feeding and management can be secured. Body weight and/or gain are, therefore, traits of great economic impor-
0301-6226/83/$03.00
© 1983 Elsevier Science Publishers B.V.
480
tance that cannot be overlooked in breeding schemes aiming at improving meat output. The purpose of the present work was to study environmental factors, such as year and month of birth, sex and type of birth of kids and dam lactation number, that influence pre-weaning and post-weaning growth traits in the Damscus goat, and develop suitable adjustment factors for these traits with regard to month and type of birth, sex and dam lactation number. MATERIALS AND METHODS
The data were obtained from a single flock (Goat Breeding Unit, Akhelia) and represent 1542 kids born in four successive years (1977--81). These kids were the progeny of 81 sires (the average sire family size was 17.2 kids) and 619 dams, born each year between November and April. The distribution of kids from multiparous and primiparous goats in each successive year of kidding was 371 and 76,357 and 54, 302 and 79 and 264 and 39, respectively. All kids were ear-notched and their birth weight, sex, type of birth (single, twin, other multiples), sire and dam lactation number (1 to 9) were recorded. The number of animals in each class and subclass is shown in Table I. They were all weighed again at weaning (70+3 days post-partum) and at 140+3 days of age. Pre-weaning and post-weaning dally gains were calculated for each kid from live weights at birth, at weaning and at 140 days of age divided by the respective period in days.
TABLE I Mean squares and tests of significance for growth characters of Damascus goats Source
Year of birth Sires/years
df
3 82 Month of birth 6 Type of birth 2 Sex of kid 1 Type × sex 2 Dam lactation no. 6 Linear 1 Quadratic 1 Cubic 1 Residual 3 Error 1439 *P < 0.05. **P < 0.01.
Weaning weight
280.43** 18.52"* 79.51"* 853.61"* 1202.59"* 1.33 24.17" 5.54 139.74"* 19.86 5.64 9.36
140-day weight
4145.7"* 62.5** 151.4"* 901.9"* 5623.6** 15.9 93.2** 6.8 537.2** 18.5 36.6 31.9
Growth rate
Pre-weaning
Post-weaning
0.0587** 0.0024** 0.0152"* 0.0977** 0.1486"* 0.0004 0.0041" 0.0037 0.0217"* 0.0012 0.0012 0.0015
0.6366** 0.0065** 0.0205** 0.0072 0.3647** 0.0028 0.0058 0.0001 0.0205* 0.0001 0.0023 0.0032
481
All goats were exposed to vasectomized males for heat detection. Goats in heat were hand-mated to avoid matings between close relatives and for the pedigree identification of the offspring. The linear model used accounted for the effects of year and m o n t h of birth, sires within year of birth, type of birth, sex, dam lactation number and t y p e of birth by sex of kid on weaning weight, 140-day weight, and preweaning and post-weaning growth rate. The sire and error terms were considered r a n d o m effects. All other effects were considered fixed. Subclass frequencies were unequal, so the m e t h o d of least squares (Harvey, 1975} was used. Kids born to goats of seven or more lactations were grouped together. Moreover, only three classes for type of birth were defined (triplets, quadruplets and others were classed as multiples}. The effects of type of rearing were n o t considered since in all cases only two kids suckled their dams and all others were reared artificially. All kids reared artificially and a small number of cross-fostered kids were also used. Dam lactation number was preferred to age at freshening for a number of reasons. In practice, it is more likely t h a t livestock keepers will record lactation number (number of parturitions) rather than age of dam (in months} at a particular parturition. Age in years almost coincides with lactation number in precocious breeds such as the Damascus goat. The effects of year of birth, although included in the same model to acc o u n t for variation in live weight and gain, were n o t used in the estimation of adjustment factors. Year of birth effects, although significant, are n o t repeatable since larger or smaller changes in management, feeding and sanitary conditions, as well as b o d y condition of the dam, are unavoidable. Furthermore, a preliminary screening, particularly of male kids, is a usual practice at bimonthly periods, being more practical from the point of management and allowing for the early culling of a large proportion of animals that are n o t intended to be used as sires or dams in the next generation. The effects of t y p e of rearing and its interaction with type of birth were n o t considered in the statistical model. Although such classes were present in the data set, their effects could n o t be estimated with adequate accuracy because of their low frequency. Moreover, artificial rearing is n o t y e t practised on a large scale, which would have made the estimation of such effects necessary. Although, the effects of m o n t h of birth could be estimated for each m o n t h separately, it was considered more appropriate to group m o n t h s into only four classes (Table II), because some m o n t h s were n o t represented in all years. No grazing o f kids was practised and sexes were penned together until 140 days of age. Following weaning all kids were fed on concentrates and barley straw to appetite. RESULTS AND DISCUSSION
Mean squares and tests of significance for all traits studied are given in Table I. There were significant year effects on all traits studied (Table II),
482 which can be attributed to dissimilar sanitary conditions from one year to another, some changes in the feed texture (pelleted or mash concentrate feed), etc. Month of birth also had a significant effect on growth (Table II). Kids born between October and February were heavier and grew faster than those born in March and April. It should be borne in mind that the latter were weaned in the summer. The high ambient temperatures, apparently had a negative effect on the growth performance of kids born late in the season (March and April) probably as result of decreased appetite and lower feed intake. TABLE II Least squares m e a n s a n d standard errors for g r o w t h characters o f D a m a s c u s g o a t s Main effect
Year o f birth
Month
Subclass
1977/78 1978/79 1979/80 1980/81 Oct.--Nov. Dec.--Jan. February March--April
Overall
No. of observations
447 411 381 303 145 286 716 395 1542
Weaning w e i g h t (kg)
16.07+-0.42 17.57±0.38 18.02+-0.40 18.36+-0.37 17.79+-0.51 17.82+-0.42 17.93±0.31 16.76+-0.39 17.51+-0.31
140-day w e i g h t (kg)
22.6±0.8 31.8+-0.7 26.7+-0.7 25.4+-0.7 26.1+-0.8 26.7+-0.7 27.2+-0.6 26.7±0.7 26.6+-0.6
G r o w t h rate (kg day -1) Pre-weaning
Post-weaning
0.162+-0.005 0.187+-0.004 0.190+-0.004 0.195+-0.004 0.191+-0.006 0.187+-0.005 0.194+-0.004 0.173+-0.004 0.184+-0.003
0.099+-0.008 0.204+-0.007 0.128+-0.007 0.107+-0.007 0.128+-0.009 0.134+-0.008 0.138+-0.007 0.132+-0.007 0.135+-0.006
TABLE n I Least squares m e a n s and standard errors for g r o w t h characters o f D a m a s c u s g o a t s Main effect
T y p e o f birth
Subclass
Singles Twins Multiples S e x o f kid Males Females Dam lactation 1 2 3 4 5 6 7 plus
No. of observations
241 923 378 805 737 251 317 328 245 194 126 81
Weaning w e i g h t (kg)
19.63+-0.36 16.94+-0.31 15.94+0.34 18.59+-0.32 16.43+-0.32 17.26+-0.37 18.00+-0.33 18.00+-0.32 18.38+0.34 17.83+-0.36 17.50+-0.39 17.02+0.47
140-day w e i g h t (kg)
28.7+-0.7 26.3+-0.6 24.8+-0.6 29.0+-0.6 24.3+-0.6 26.4+-0.7 27.5+0.6 27.9+-0.6 28.4+-0.6 27.6+-0.7 26.8+-0.7 25.8+0.8
G r o w t h rate (kg day -I) Preoweaning
Post-weaning
0.207+0.004 0.176+-0.004 0.169+0.004 0.196+-0.004 0.172+-0.004 0.184+-0.004 0.191+-0.004 0.192+-0.004 0.196+-0.004 0.190+-0.004 0.183+-0.005 0.177+0.007
0.134+-0.007 0.139+-0.006 0.131+-0.006 0.153+0.006 0.116+-0.006 0.134+-0.007 0.138+-0.006 0.144+-0.006 0.147+-0.006 0.143+-0.007 0.140+-0.007 0.130+0.010
Males were always heavier ( P < 0 . 0 1 ) and grew faster ( P < 0 . 0 1 ) than females (Table III). Differences between sexes are well documented for all phases of the growth curve (Louca et al., 1975; Hadjipanayiotou and Louca, 1976; Mavrogenis et al., 1979).
483
Type of birth had a significant effect on weaning weight, pre-weaning growth rate and 140-day weight. Pre-weaning growth and weaning weight are a function of individual potential for growth, maternal effects (through milk and other maternal genetic and environmental factors), and/or carryover effects of live weight at birth, litter size born and number of individuals suckling. Post-weaning growth rate is, however, to a large degree free of maternal and carry-over effects. Hence, no significant differences were detected between singles, twins or other multiples (Tables I and III). Similar findings have been reported in sheep (Bichard and Cooper, 1966; Gjedrem, 1967; Louca et al., 1975; Mavrogenis and Louca, 1979; Mavrogenis et al., 1980). There were no significant interaction effects of type of birth by sex on any of the traits studied, indicating that rank and scale among the various sub-classes is consistent. The effects of lactation number of dam on weaning weight, pre-weaning growth rate and 140-day weight were clearly quadratic (Tables I and III). Significant quadratic age of dam effects have been reported by Moulick et al. (1966) for the Black Bengal goat. Lactation n u m b e r effects on 140-day weight probably reflect carry-over effects from weaning weight, since its effect was small (P,=0.05) on post-weaning growth rate (Table I). Growth rate after weaning (averaged over sexes) was similar for all type-of-birth classes. Moreover, when weaning weight was used as covariable postweaning growth and 140-day weight were independent of lactation number effects. TABLE IV Multiplicative adjustment factors for growth characters of Damascus goats Main effect
Month of birth
Type of birth
Sex of kid Dam lactation
Weaning weight
Oct.--Nov. Dec.--Jan. February March--April Singles Twins Multiples Males Females 1 2 3 4 5 6 7 plus
1.01 1.01 1.00 1.07 1.00 1.16 1.23 1.00 1.13 1.06 1.02 1.02 1.00 1.03 1.05 1.08
140-day weight
1.04 1.02 1.00 1.02 1.00 1.09 1.16 1.00 1.19 1.08 1.03 1.02 1.00 1.03 1.06 1.10
Growth rate Pre-weaning
Post-weaning
1.02 1.04 1.00 1.12 1.00 1.18 1.22 1.00 1.14 1.07 1.03 1.02 1.00 1.03 1.07 1.11
1.08 1.03 1.00 1.05 1.04 1.00 1.06 1.00 1.32 1.10 1.07 1.02 1.00 1.03 1.05 1.13
484
Adjustment factors computed across years for the effects of months of birth, type of birth, sex of lamb and dam lactation number are presented in Table IV. Subclass means for this table were the sum of the overall leastsquares means plus least-squares constants for those effects. They are expressed as ratios to male, single lambs born to fourth lactation dams in February. There were no effects of artificial rearing or interactions between type of birth and type of rearing for any of the traits studied. Similar results have been reported by Notter et al. (1975) for 90-day lamb weight. Hence, it was not considered necessary t o develop correction factors for the combined effects of type of birth and rearing. In addition, crossfostering was infrequent in this study and only two lambs from multiple sets were allowed to suckle their dams. Correction factors have been used extensively for dairy and beef cattle. More recently they have been used in sheep, but rarely in goats. Most adjustment factors for goats refer to milk production. Both.additive and multiplicative adjustment factors have been used and their merit has been discussed. In a review, Freeman {1973) pointed out that the main objective is to equalize both means and variances among subclasses. A number of investigators suggested that adjustments for age of dam differences should be additive (Cundiff et al., 1966; Anderson and Willham, 1978), since multiplicative adjustments would also change the variance among subclass records. Multiplicative adjustment factors are expected to be more appropriate in performancetesting situations where large flock differences exist. To test this particular set of adjustment factors, however, would require their application to an independent set of data which is yet not available. The sets of correction factors developed in this study should provide livestock breeders with an improved procedure for selection, free of some of the most important environmental factors influencing growth performance characters. Since 140-day weight was found to be a better criterion of selection for growth traits (Mavrogenis et al., 1980) it would seem more appropriate to correct those live weights by the appropriate adjustment factors. Adjustments for weaning weight should be used with some caution, since weaning weight is a complex character that expresses both the genetics of lamb for growth and some maternal effects through milk production and mothering ability during the suckling period. They could, however, be used for suckling-lamb operations where the primary selection criterion is weaning weight, provided that maternal genetic effects and genetic effects for growth are not antagonistic.
REFERENCES Anderson, J.H. and WiUham, R.L., 1978. Weaning weight correction factors from Angus field data. J. Anim. Sci., 47: 124--130. Bichard, M. and Cooper, M.McG., 1966. Analysis of production records from a lowland sheep flock. 1. L a m b mortality and growth to 16 weeks. Anim. Prod., 8: 401--410. Cundiff, L.V., Willham, R.L. and Pratt, C.A., 1966. Additive versus multiplicative correction factors for weaning weight in beef cattle. J. Anim. Sci., 25 : 983---987.
485 Fimland, E., Eri, J., Liland, P.J. and Gjedrem, T., 1969. Resultat fra Kryssningstorsok med sau. Meld. Nor. Landbrukhoegsk., 13: 35. Freeman, A.E., 1973. Age adjustment of production records; history and basic problems. J. Dairy Sci., 56: 941--967. Gjedrem, T., 1965. Verknaden au nokre & miljofaktorar pa haustvekha hos lain. Meld. Nor. Landbrukhoegsk., 3: 32. Gjedrem, T., 1967. Phenotypic and genetic parameters for weights of lambs at five ages. Acta Agric. Scand. 17: 199--216. Hadjipanayiotou, M. and Louca, A., 1976. The effects of partial suckling on the lactation performance of Chios sheep and Damascus goats and the growth rate of lambs and kids. J. Agric. Sci., 87: 15--20. Harvey, W.R., 1975. Least squares analysis of data with unequal subclass numbers. USDA, ARS H.4, Washington, DC, 157 pp. Louca, A., Mavrogenis, A. and Lawlor, M.J., 1975. The effect of early weaning on the lactation performance of Damascus goats and the growth rate of the kids. Anita. Prod., 20: 213--218. Mavrogenis, A.P. and Louca, A., 1979. A note on some factors influencing post-weaning performance of purebred and crossbred lambs. Anita, Prod., 29: 415--418. Mavrogenis, A.P., Economides, S., Louca, A. and Hancock, J., 1979. The effect of dietary protein levels on the performance of Damascus kids. Agric. Res. Inst. Techn. Bull. No. 27, Nicosia, 9 pp. Mavrogenis, A.P., Louca, A. and Robison, O.W., 1980. Estimates of genetic parameters for pre-weaning and post-weaning growth traits of Chios lambs. Anim. Prod., 30: 271--276. Moulick, S.K., Guha, H., Gupta, S., Mitra, D.K. and Bhattacharya, S., 1966. Factors affecting multiple birth in Black Bengal goats. Indian J. Vet. Sci., 36: 154--163. Notter, D.R., Swiger, L.A. and Harvey, W.R., 1975. Adjustment factors for 90-day lamb weight. J. Anita. Sci., 40: 383--391.
RESUME
Mavrogenis, A.P., 1983. Facteurs de correction pour les caract~res de croissance de la ch~vre Damascaine. Livest. Prod. Sci., 10: 479--486. Les donn~es enregistrdes sur 1542 jeunes caprins de race Damascaine de l'unit~ de s~lection caprine d'Akhelia, ont ~t~ analys~es pour d~terminer l'influence sur los caract~res de croissance, de l'ann~e, du mois et du mode (simples, doubles et multiples) de naissance, du sexe et du num~ro de lactation de la m~re. L'analyse par la m~thode des moindres carr~s montre que tous ces facteurs ont eu une influence significative (P < 0,01) sur le poids au sewage, le croit avant sewage et le poids ~ 140 jours. Les effets du mode de naissance et du num~ro de lactation o n t ~td faihles et non significatifs sur le croft apr~s sewage. On a calcul~ les facteurs de correction intra-ann~e de naissance pour los effets du mois de nalssance, du mode de naissance, du sexe du jeune et du numdro de lactation de la m~re. Bien qu'~tablis dans un seul troupeau, ces facteurs de correction peuvent ~tre utilis~s, avec quelque precaution, dans les programmes de s~lection des ch~vres Damascaines.
486
KURZFASSUNG Mavrogenis, A.P., 1983. Korrekturfaktoren ~ r Wachstumsmerkmale bei der Damaskusziege. Livest. Prodl Sci., 10:479---486 (auf englisch). Es wurden 1542 Daten von reinrassigen Damaskusziegenl/immern aus der Ziegenzuchtstation Akhelia benutzt, um den Einfluss des Jahres, des Geburtsmonats, der Anzahl der Geburtsgeschwister und der Nummer der Laktation der Mutter auf die Wachstumsmerkmale bei der Ziege zu untersuchen. Die "least-squares"-Analyse zeigte, dass alle untersuchten Faktoren einen signifikanten Einfluss auf das Absetzgewicht, die Waehstumsentwieklung bis zum Absetzen und auf das 140-Tage-Gewicht hatten (P<0,01). Die Auswirkungen der Anzahl der Wurfgeschwister und der Nummer der Laktation der Mutter auf die Wachstumsentwicklung nach dem Absetzen waren gering und nicht signifikant. Bezogen auf das Geburtsjahr wurden Korrekturfaktoren errechnet fiir den Einfluss des Geburtsmonats, die Anzahl der Wurfgeschwister, das Geschlecht des Lamms und die Nummer der Laktation der Mutter. Diese Korrekturfaktoren, obwohl sie von einer einzigen Herde stammen, k 6 n n e n mit gewisser Vorsicht in einem Zuchtprogramm fiir die Verbesserung der Damaskusziegen verwendet werden.
479
A D J U S T M E N T F A C T O R S FOR GROWTH CHARACTERS OF THE DAMASCUS GOAT
A.P. MAVROGENIS
Agricultural Research Institue, Nicosia (Cyprus) (Accepted 26 April 1983)
ABSTRACT
Mavrogenis, A.P., 1983. Adjustment factors for growth characters of the Damascus goat. Livest. Prod. Sci., 10: 479--486. Data on 1542 purebred Damascus kids obtained from the Goat Breeding Unit at Akhelia were used to determine the effects of year, m o n t h and type of birth (singles, twins, other multiples), sex of kid and dam lactation number on growth characters of goats. Least squares analyses showed that all factors studied had a significant effect on weaning weight, pre-weaning growth rate and 140-day weight (P<0.01). Type of birth and lactation number effects were small and insignificant for post-weaning growth rate. Adjustment factors were computed across year of birth for the effects of m o n t h of birth, type of birth, sex of kid and dam lactation number. These adjustment factors, although developed from a single herd, can be used, with some caution, in a breeding program for the improvement of Damascus goats. INTRODUCTION
Selection for superior breeding stock presumes that the procedures used in selection are adequate and accurate enough so that it can be based on genotypic rather than environmental merit. It is well d o c u m e n t e d that corrections for classifiable non-genetic sources of variation render selection and culling more accurate. Gjedrem (1965} and Fimland et al. {1969} have reported that 30--40% of the variation in weaning weight of lambs can be accounted for by environmental factors. The use of suitable adjustment factors for production characters is an important tool to the animal breeder and producer in general. Ideally, these adjustment factors should be developed for specific management systems, b u t sufficient data are rarely available. The Damascus goat is found in a n u m b e r of Middle East countries, and it is characterized b y high milk production and prolificacy (Louca et al., 1975; Hadjipanayiotou and Louca, 1976}. It is mostly exploited as a dual-purpose animal and kept under semi-intensive or intensive conditions where better feeding and management can be secured. Body weight and/or gain are, therefore, traits of great economic impor-
0301-6226/83/$03.00
© 1983 Elsevier Science Publishers B.V.
480
tance that cannot be overlooked in breeding schemes aiming at improving meat output. The purpose of the present work was to study environmental factors, such as year and month of birth, sex and type of birth of kids and dam lactation number, that influence pre-weaning and post-weaning growth traits in the Damscus goat, and develop suitable adjustment factors for these traits with regard to month and type of birth, sex and dam lactation number. MATERIALS AND METHODS
The data were obtained from a single flock (Goat Breeding Unit, Akhelia) and represent 1542 kids born in four successive years (1977--81). These kids were the progeny of 81 sires (the average sire family size was 17.2 kids) and 619 dams, born each year between November and April. The distribution of kids from multiparous and primiparous goats in each successive year of kidding was 371 and 76,357 and 54, 302 and 79 and 264 and 39, respectively. All kids were ear-notched and their birth weight, sex, type of birth (single, twin, other multiples), sire and dam lactation number (1 to 9) were recorded. The number of animals in each class and subclass is shown in Table I. They were all weighed again at weaning (70+3 days post-partum) and at 140+3 days of age. Pre-weaning and post-weaning dally gains were calculated for each kid from live weights at birth, at weaning and at 140 days of age divided by the respective period in days.
TABLE I Mean squares and tests of significance for growth characters of Damascus goats Source
Year of birth Sires/years
df
3 82 Month of birth 6 Type of birth 2 Sex of kid 1 Type × sex 2 Dam lactation no. 6 Linear 1 Quadratic 1 Cubic 1 Residual 3 Error 1439 *P < 0.05. **P < 0.01.
Weaning weight
280.43** 18.52"* 79.51"* 853.61"* 1202.59"* 1.33 24.17" 5.54 139.74"* 19.86 5.64 9.36
140-day weight
4145.7"* 62.5** 151.4"* 901.9"* 5623.6** 15.9 93.2** 6.8 537.2** 18.5 36.6 31.9
Growth rate
Pre-weaning
Post-weaning
0.0587** 0.0024** 0.0152"* 0.0977** 0.1486"* 0.0004 0.0041" 0.0037 0.0217"* 0.0012 0.0012 0.0015
0.6366** 0.0065** 0.0205** 0.0072 0.3647** 0.0028 0.0058 0.0001 0.0205* 0.0001 0.0023 0.0032
481
All goats were exposed to vasectomized males for heat detection. Goats in heat were hand-mated to avoid matings between close relatives and for the pedigree identification of the offspring. The linear model used accounted for the effects of year and m o n t h of birth, sires within year of birth, type of birth, sex, dam lactation number and t y p e of birth by sex of kid on weaning weight, 140-day weight, and preweaning and post-weaning growth rate. The sire and error terms were considered r a n d o m effects. All other effects were considered fixed. Subclass frequencies were unequal, so the m e t h o d of least squares (Harvey, 1975} was used. Kids born to goats of seven or more lactations were grouped together. Moreover, only three classes for type of birth were defined (triplets, quadruplets and others were classed as multiples}. The effects of type of rearing were n o t considered since in all cases only two kids suckled their dams and all others were reared artificially. All kids reared artificially and a small number of cross-fostered kids were also used. Dam lactation number was preferred to age at freshening for a number of reasons. In practice, it is more likely t h a t livestock keepers will record lactation number (number of parturitions) rather than age of dam (in months} at a particular parturition. Age in years almost coincides with lactation number in precocious breeds such as the Damascus goat. The effects of year of birth, although included in the same model to acc o u n t for variation in live weight and gain, were n o t used in the estimation of adjustment factors. Year of birth effects, although significant, are n o t repeatable since larger or smaller changes in management, feeding and sanitary conditions, as well as b o d y condition of the dam, are unavoidable. Furthermore, a preliminary screening, particularly of male kids, is a usual practice at bimonthly periods, being more practical from the point of management and allowing for the early culling of a large proportion of animals that are n o t intended to be used as sires or dams in the next generation. The effects of t y p e of rearing and its interaction with type of birth were n o t considered in the statistical model. Although such classes were present in the data set, their effects could n o t be estimated with adequate accuracy because of their low frequency. Moreover, artificial rearing is n o t y e t practised on a large scale, which would have made the estimation of such effects necessary. Although, the effects of m o n t h of birth could be estimated for each m o n t h separately, it was considered more appropriate to group m o n t h s into only four classes (Table II), because some m o n t h s were n o t represented in all years. No grazing o f kids was practised and sexes were penned together until 140 days of age. Following weaning all kids were fed on concentrates and barley straw to appetite. RESULTS AND DISCUSSION
Mean squares and tests of significance for all traits studied are given in Table I. There were significant year effects on all traits studied (Table II),
482 which can be attributed to dissimilar sanitary conditions from one year to another, some changes in the feed texture (pelleted or mash concentrate feed), etc. Month of birth also had a significant effect on growth (Table II). Kids born between October and February were heavier and grew faster than those born in March and April. It should be borne in mind that the latter were weaned in the summer. The high ambient temperatures, apparently had a negative effect on the growth performance of kids born late in the season (March and April) probably as result of decreased appetite and lower feed intake. TABLE II Least squares m e a n s a n d standard errors for g r o w t h characters o f D a m a s c u s g o a t s Main effect
Year o f birth
Month
Subclass
1977/78 1978/79 1979/80 1980/81 Oct.--Nov. Dec.--Jan. February March--April
Overall
No. of observations
447 411 381 303 145 286 716 395 1542
Weaning w e i g h t (kg)
16.07+-0.42 17.57±0.38 18.02+-0.40 18.36+-0.37 17.79+-0.51 17.82+-0.42 17.93±0.31 16.76+-0.39 17.51+-0.31
140-day w e i g h t (kg)
22.6±0.8 31.8+-0.7 26.7+-0.7 25.4+-0.7 26.1+-0.8 26.7+-0.7 27.2+-0.6 26.7±0.7 26.6+-0.6
G r o w t h rate (kg day -1) Pre-weaning
Post-weaning
0.162+-0.005 0.187+-0.004 0.190+-0.004 0.195+-0.004 0.191+-0.006 0.187+-0.005 0.194+-0.004 0.173+-0.004 0.184+-0.003
0.099+-0.008 0.204+-0.007 0.128+-0.007 0.107+-0.007 0.128+-0.009 0.134+-0.008 0.138+-0.007 0.132+-0.007 0.135+-0.006
TABLE n I Least squares m e a n s and standard errors for g r o w t h characters o f D a m a s c u s g o a t s Main effect
T y p e o f birth
Subclass
Singles Twins Multiples S e x o f kid Males Females Dam lactation 1 2 3 4 5 6 7 plus
No. of observations
241 923 378 805 737 251 317 328 245 194 126 81
Weaning w e i g h t (kg)
19.63+-0.36 16.94+-0.31 15.94+0.34 18.59+-0.32 16.43+-0.32 17.26+-0.37 18.00+-0.33 18.00+-0.32 18.38+0.34 17.83+-0.36 17.50+-0.39 17.02+0.47
140-day w e i g h t (kg)
28.7+-0.7 26.3+-0.6 24.8+-0.6 29.0+-0.6 24.3+-0.6 26.4+-0.7 27.5+0.6 27.9+-0.6 28.4+-0.6 27.6+-0.7 26.8+-0.7 25.8+0.8
G r o w t h rate (kg day -I) Preoweaning
Post-weaning
0.207+0.004 0.176+-0.004 0.169+0.004 0.196+-0.004 0.172+-0.004 0.184+-0.004 0.191+-0.004 0.192+-0.004 0.196+-0.004 0.190+-0.004 0.183+-0.005 0.177+0.007
0.134+-0.007 0.139+-0.006 0.131+-0.006 0.153+0.006 0.116+-0.006 0.134+-0.007 0.138+-0.006 0.144+-0.006 0.147+-0.006 0.143+-0.007 0.140+-0.007 0.130+0.010
Males were always heavier ( P < 0 . 0 1 ) and grew faster ( P < 0 . 0 1 ) than females (Table III). Differences between sexes are well documented for all phases of the growth curve (Louca et al., 1975; Hadjipanayiotou and Louca, 1976; Mavrogenis et al., 1979).
483
Type of birth had a significant effect on weaning weight, pre-weaning growth rate and 140-day weight. Pre-weaning growth and weaning weight are a function of individual potential for growth, maternal effects (through milk and other maternal genetic and environmental factors), and/or carryover effects of live weight at birth, litter size born and number of individuals suckling. Post-weaning growth rate is, however, to a large degree free of maternal and carry-over effects. Hence, no significant differences were detected between singles, twins or other multiples (Tables I and III). Similar findings have been reported in sheep (Bichard and Cooper, 1966; Gjedrem, 1967; Louca et al., 1975; Mavrogenis and Louca, 1979; Mavrogenis et al., 1980). There were no significant interaction effects of type of birth by sex on any of the traits studied, indicating that rank and scale among the various sub-classes is consistent. The effects of lactation number of dam on weaning weight, pre-weaning growth rate and 140-day weight were clearly quadratic (Tables I and III). Significant quadratic age of dam effects have been reported by Moulick et al. (1966) for the Black Bengal goat. Lactation n u m b e r effects on 140-day weight probably reflect carry-over effects from weaning weight, since its effect was small (P,=0.05) on post-weaning growth rate (Table I). Growth rate after weaning (averaged over sexes) was similar for all type-of-birth classes. Moreover, when weaning weight was used as covariable postweaning growth and 140-day weight were independent of lactation number effects. TABLE IV Multiplicative adjustment factors for growth characters of Damascus goats Main effect
Month of birth
Type of birth
Sex of kid Dam lactation
Weaning weight
Oct.--Nov. Dec.--Jan. February March--April Singles Twins Multiples Males Females 1 2 3 4 5 6 7 plus
1.01 1.01 1.00 1.07 1.00 1.16 1.23 1.00 1.13 1.06 1.02 1.02 1.00 1.03 1.05 1.08
140-day weight
1.04 1.02 1.00 1.02 1.00 1.09 1.16 1.00 1.19 1.08 1.03 1.02 1.00 1.03 1.06 1.10
Growth rate Pre-weaning
Post-weaning
1.02 1.04 1.00 1.12 1.00 1.18 1.22 1.00 1.14 1.07 1.03 1.02 1.00 1.03 1.07 1.11
1.08 1.03 1.00 1.05 1.04 1.00 1.06 1.00 1.32 1.10 1.07 1.02 1.00 1.03 1.05 1.13
484
Adjustment factors computed across years for the effects of months of birth, type of birth, sex of lamb and dam lactation number are presented in Table IV. Subclass means for this table were the sum of the overall leastsquares means plus least-squares constants for those effects. They are expressed as ratios to male, single lambs born to fourth lactation dams in February. There were no effects of artificial rearing or interactions between type of birth and type of rearing for any of the traits studied. Similar results have been reported by Notter et al. (1975) for 90-day lamb weight. Hence, it was not considered necessary t o develop correction factors for the combined effects of type of birth and rearing. In addition, crossfostering was infrequent in this study and only two lambs from multiple sets were allowed to suckle their dams. Correction factors have been used extensively for dairy and beef cattle. More recently they have been used in sheep, but rarely in goats. Most adjustment factors for goats refer to milk production. Both.additive and multiplicative adjustment factors have been used and their merit has been discussed. In a review, Freeman {1973) pointed out that the main objective is to equalize both means and variances among subclasses. A number of investigators suggested that adjustments for age of dam differences should be additive (Cundiff et al., 1966; Anderson and Willham, 1978), since multiplicative adjustments would also change the variance among subclass records. Multiplicative adjustment factors are expected to be more appropriate in performancetesting situations where large flock differences exist. To test this particular set of adjustment factors, however, would require their application to an independent set of data which is yet not available. The sets of correction factors developed in this study should provide livestock breeders with an improved procedure for selection, free of some of the most important environmental factors influencing growth performance characters. Since 140-day weight was found to be a better criterion of selection for growth traits (Mavrogenis et al., 1980) it would seem more appropriate to correct those live weights by the appropriate adjustment factors. Adjustments for weaning weight should be used with some caution, since weaning weight is a complex character that expresses both the genetics of lamb for growth and some maternal effects through milk production and mothering ability during the suckling period. They could, however, be used for suckling-lamb operations where the primary selection criterion is weaning weight, provided that maternal genetic effects and genetic effects for growth are not antagonistic.
REFERENCES Anderson, J.H. and WiUham, R.L., 1978. Weaning weight correction factors from Angus field data. J. Anim. Sci., 47: 124--130. Bichard, M. and Cooper, M.McG., 1966. Analysis of production records from a lowland sheep flock. 1. L a m b mortality and growth to 16 weeks. Anim. Prod., 8: 401--410. Cundiff, L.V., Willham, R.L. and Pratt, C.A., 1966. Additive versus multiplicative correction factors for weaning weight in beef cattle. J. Anim. Sci., 25 : 983---987.
485 Fimland, E., Eri, J., Liland, P.J. and Gjedrem, T., 1969. Resultat fra Kryssningstorsok med sau. Meld. Nor. Landbrukhoegsk., 13: 35. Freeman, A.E., 1973. Age adjustment of production records; history and basic problems. J. Dairy Sci., 56: 941--967. Gjedrem, T., 1965. Verknaden au nokre & miljofaktorar pa haustvekha hos lain. Meld. Nor. Landbrukhoegsk., 3: 32. Gjedrem, T., 1967. Phenotypic and genetic parameters for weights of lambs at five ages. Acta Agric. Scand. 17: 199--216. Hadjipanayiotou, M. and Louca, A., 1976. The effects of partial suckling on the lactation performance of Chios sheep and Damascus goats and the growth rate of lambs and kids. J. Agric. Sci., 87: 15--20. Harvey, W.R., 1975. Least squares analysis of data with unequal subclass numbers. USDA, ARS H.4, Washington, DC, 157 pp. Louca, A., Mavrogenis, A. and Lawlor, M.J., 1975. The effect of early weaning on the lactation performance of Damascus goats and the growth rate of the kids. Anita. Prod., 20: 213--218. Mavrogenis, A.P. and Louca, A., 1979. A note on some factors influencing post-weaning performance of purebred and crossbred lambs. Anita, Prod., 29: 415--418. Mavrogenis, A.P., Economides, S., Louca, A. and Hancock, J., 1979. The effect of dietary protein levels on the performance of Damascus kids. Agric. Res. Inst. Techn. Bull. No. 27, Nicosia, 9 pp. Mavrogenis, A.P., Louca, A. and Robison, O.W., 1980. Estimates of genetic parameters for pre-weaning and post-weaning growth traits of Chios lambs. Anim. Prod., 30: 271--276. Moulick, S.K., Guha, H., Gupta, S., Mitra, D.K. and Bhattacharya, S., 1966. Factors affecting multiple birth in Black Bengal goats. Indian J. Vet. Sci., 36: 154--163. Notter, D.R., Swiger, L.A. and Harvey, W.R., 1975. Adjustment factors for 90-day lamb weight. J. Anita. Sci., 40: 383--391.
RESUME
Mavrogenis, A.P., 1983. Facteurs de correction pour les caract~res de croissance de la ch~vre Damascaine. Livest. Prod. Sci., 10: 479--486. Les donn~es enregistrdes sur 1542 jeunes caprins de race Damascaine de l'unit~ de s~lection caprine d'Akhelia, ont ~t~ analys~es pour d~terminer l'influence sur los caract~res de croissance, de l'ann~e, du mois et du mode (simples, doubles et multiples) de naissance, du sexe et du num~ro de lactation de la m~re. L'analyse par la m~thode des moindres carr~s montre que tous ces facteurs ont eu une influence significative (P < 0,01) sur le poids au sewage, le croit avant sewage et le poids ~ 140 jours. Les effets du mode de naissance et du num~ro de lactation o n t ~td faihles et non significatifs sur le croft apr~s sewage. On a calcul~ les facteurs de correction intra-ann~e de naissance pour los effets du mois de nalssance, du mode de naissance, du sexe du jeune et du numdro de lactation de la m~re. Bien qu'~tablis dans un seul troupeau, ces facteurs de correction peuvent ~tre utilis~s, avec quelque precaution, dans les programmes de s~lection des ch~vres Damascaines.
486
KURZFASSUNG Mavrogenis, A.P., 1983. Korrekturfaktoren ~ r Wachstumsmerkmale bei der Damaskusziege. Livest. Prodl Sci., 10:479---486 (auf englisch). Es wurden 1542 Daten von reinrassigen Damaskusziegenl/immern aus der Ziegenzuchtstation Akhelia benutzt, um den Einfluss des Jahres, des Geburtsmonats, der Anzahl der Geburtsgeschwister und der Nummer der Laktation der Mutter auf die Wachstumsmerkmale bei der Ziege zu untersuchen. Die "least-squares"-Analyse zeigte, dass alle untersuchten Faktoren einen signifikanten Einfluss auf das Absetzgewicht, die Waehstumsentwieklung bis zum Absetzen und auf das 140-Tage-Gewicht hatten (P<0,01). Die Auswirkungen der Anzahl der Wurfgeschwister und der Nummer der Laktation der Mutter auf die Wachstumsentwicklung nach dem Absetzen waren gering und nicht signifikant. Bezogen auf das Geburtsjahr wurden Korrekturfaktoren errechnet fiir den Einfluss des Geburtsmonats, die Anzahl der Wurfgeschwister, das Geschlecht des Lamms und die Nummer der Laktation der Mutter. Diese Korrekturfaktoren, obwohl sie von einer einzigen Herde stammen, k 6 n n e n mit gewisser Vorsicht in einem Zuchtprogramm fiir die Verbesserung der Damaskusziegen verwendet werden.