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Adjustment factors for growth traits of Chios sheep
Livestock Production Science, 19 (1988) 409-416
409
Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
Adjustment Factors for Growth Traits of Chios Sheep A.P. MAVROGENIS
Agricultural Research Institute, Nicosia (Cyprus) (Accepted 30 December 1987)
ABSTRACT Mavrogenis, A.P., 1988. Adjustment factors for growth traits of Chios sheep. Livest. Prod. Sci., 19: 409-416. Data on 3741 purebred Chios lambs, collected at Athalassa and Orites, were used to determine the effects of year, month and type of birth, sex of lamb and dam lactation number on pre-weaning and post-weaning growth traits of sheep. Least-squares analyses revealed that most of the factors studied had a significant effect (P < 0.01 ) on lamb live weights. Flock effects were important for weaning weight only, but year and month of birth were significant for all live weights (P < 0.01 ). Dam lactation number effects were small and insignificant for post-weaning growth rate alone. Although year-by-month interactions were in all cases significant, no changes in rank were detected. Type of birth-by-sex interaction was not significant for any of the traits studied. Adjustment factors were computed across year of birth for the effects of month of birth, type of birth, sex of lamb and dam lactation number. Since flock effects were insignificant, these multiplicative adjustment factors could be used in performance testing programs for the improvement of growth traits in Chios sheep.
INTRODUCTION
To improve breeding value, selection must be based on genotypic rather than environmental superiority. It is well documented that corrections for classifiable sources of variation render selection and culling more accurate and should be removed by the use of suitable adjustment factors (Notter et al., 1975). Adjustment factors may be developed for similar management-feeding regimes, although each regime may possess its own specificities. The Chios breed is found in mainland Greece, on some of the Greek islands, at the coastal area of Turkey and in Cyprus. It is characterized by high milk production and prolificacy (Lawlor et al., 1974; Mavrogenis and Louca, 1979; Mavrogenis, 1982 ) and it is mostly exploited as a dual purpose animal. Lamb growth is considered satisfatory (Mavrogenis and Louca, 1979; Mavrogenis et al., 1980; Mavrogenis, 1982 ). The breed thrives under semi-intensive or inten0301-6226/88/$03.50
© 1988 Elsevier Science Publishers B.V.
410
sive conditions, where better management and feeding are secured. Body weight and/or gain is, therefore, a character of equal economic importance to milk and must be considered in schemes aimed at improving meat production. The purpose of this study was to identify classifiable sources of environmental variation influencing pre-weaning and post-weaning growth, and to develop suitable adjustment factors for growth traits in the Chios sheep. MATERIALS AND METHODS
The data were obtained at 2 experimental units of the Department of Agriculture (Athalassa and Orites). They represent weights and growth rates of 3741 lambs, born in 9 successive years (1978-1986), that were the progeny of 155 sires. The distribution of lambs within each year was similar and the family size was 22.3 lambs per sire. Different sires were used in each farm and their use was limited to a single year. All lambs were ear-tagged and their birth weight, sex, type of birth (single, twin or multiple), sire, dam and dam lactation number (1-9) were recorded. They were all weighed again at weaning ( 42 _ 3 days post-partum ) and at 105 days of age. Pre-weaning and post-weaning gains were calculated from live weights at the various stages of growth. All ewes were joined to vasectomized males for heat detection and oestrous ewes were hand mated to avoid matings between relatives and for pedigree purposes. The linear model used accounted for the effects of year and month of birth, flocks, sires within years and flocks, type of birth and sex of lamb, dam lactation number and a number of 2-way interactions. Years, sires within years and flocks and interactions containing years and error were considered random effects, while all other effects were considered fixed. Sub-class frequencies were unequal and, therefore, the method of least squares (S.A.S., 1985) was employed. Lambs born to ewes of >~6 lactations were grouped together. Moreover, only 3 classes for type of birth were considered (triplets, quadruplets and others were classed as multiples). Dam lactation number was preferred to age at lambing, since in practice it is more likely that livestock keepers will record lactation rather than age (in months or in years). In addition, age in years almost coincides with lactation number, particularly for early-maturing breeds. The effects of type of rearing and their interaction with type of birth were not considered in the statistical model. Although such classes were present in the data set, their effects could not be estimated with adequate accuracy because of their low frequency. Moreover, artificial rearing is not yet practiced on a large enough scale to require correction factors or the estimation of such effects. Although the effects of month of birth could be estimated for each month separately, it was considered more appropriate to group months into 4 classes, since not all months were represented in all years. No grazing of lambs was
411 practiced and sexes were kept together until 105 days of age. Following weaning, all lambs were fed on a concentrate mixture and barley hay and straw ad libitum. RESULTS AND DISCUSSION Mean squares and tests of significance for the traits studied are presented in Table I. Significant year effects were found for all live weights and gains and can be partly attributed to differences in sanitary conditions and other uncontrollable environmental factors. M o n t h of birth had a significant effect on all growth traits (Table II). Lambs born between September and December were mostly heavier and had faster growth rates before and after weaning than those born in spring ( M a r c h - M a y ) . Tail-enders are often penalized because of lower intakes due to higher ambient temperatures during and following weaning, which coincides with early summer. Males were always heavier ( P < 0.01 ) and had a faster pre-weaning and postweaning growth rate ( P < 0.01 ) than female lambs (Table III ). Growth differences between sexes have been well documented for all phases of the growth curve (Gjedrem, 1967; Eikje, 1971; Notter et al., 1975; Mavrogenis and Louca, 1979; Mavrogenis et al., 1980; Mavrogenis, 1982). Type of birth had a significant effect ( P < 0.01 ) on all live weights and gains. Weaning weight and pre-weaning growth rate may be influenced by non-genetic factors such as number of lambs suckling and milk capacity of the dam. Post-weaning growth rate should, however, be free of maternal and carry-over effects. The lower heritability estimates for weaning weight and pre-weaning TABLE I Mean squares and tests of significance for growth characters of Chios sheep Source Flocks Sires/flocks )
df 1 196 8 3 2 1 5 8 24 3492
Weaning weight
105-day weight
48.84**
0.49
1546.62"* 441.38"* 106.55"* 5879.19"* 838.22** 294.31"* 554.67** 317.73"* 8.55
8300.16"* 994.61"* 1680.16"* 11404.49** 10196.49** 672.06** 1944.94"* 1903.54"* 54.24
P r e - w e a n i n g Post-weaning growth rate growth rate 0.001
0.003
0.548** 0.064** 0.102"* 1.195"* 0.242** 0.065** 0.078** 0.126"* 0.003
1.350"* 0.169"* 0.230** 0.236** 1.459"* 0.028 0.376** 0.483** 0.009
412 T A B L E II Least-squares means and standard errors for growth traits of Chios sheep Main effect
Sub-class
No. of observations
Weaning weight (kg)
105-day weight (kg)
Growth rate (g day 1) Pre-weaning
Post-weaning
252 327 373 401 451 381 489 518 549
14.5 _+0.9 14.8_+0.8 14.1 _+0.6 12.8_+ 0.5 13.7 _+0.5 12.5_+0.6 12.6±0.7 12.8_+0.8 13.1 _+0.7
24.2 ± 1.8 28.2_+1.6 27.1 _+ 1.2 25.3 _+ 1.1 28.3 ± 1.1 26.4 ± 1.3 27.3 _+1.4 26.8_+1.7 26.6_+1.5
198_+32 230_+ 29 214_+ 22 203 _+19 224_+ 19 205_+ 22 203 _+25 209 ±31 215 ± 27
184±22 227 _+19 228_+ 15 204_+ 13 238_+ 13 224± 15 234_+ 17 223_+ 21 216_+ 19
Year
1977/78 1978/79 1979/80 1980/81 1981/82 1982/83 1983/84 1984/85 1985/86
Month
Sep.-Oct. Nov.-Dec. Jan.-Feb. Mar.-May
1822 511 1214 194
13.9_+0.2 13.6±0.3 13.2_+0.2 13.1 _+0.2
28.3±0.3 27.6_+0.5 25.8_+0.4 24.9 _+0.6
224_+4 216_+8 205_+5 199_+8
239_+4 231±6 210±5 199_+7
Flock
Athalassa Akhelia
1719 2022
13.2 _+0.2 13.6 _+0.2
26.9 _+0.3 27.9 _+0.3
213_+4 217_+4
222_+4 237_+4
T A B L E III Least-squares means and standard errors for growth traits of Chios lambs Main effect
Sub-class
No. of Weaning observations weight (kg)
105-day weight (kg)
Growth rate (g d a y - 1) Pre-weaning
Post-weaning
Type of birth
Singles Twins Multiples
990 2093 658
15.6 _+0.2 13.2 _+0.2 11.6 _+0.2
29.6 _+0.4 26.6 _+0.3 23.9 _+0.4
242_+4 206 -+ 4 186±5
232±4 222 ± 4 205±4
Sex of lamb
Males Females
1899 1842
14.0 _+0.2 12.9 ± 0.2
28.6 _+0.3 24.8 _+0.3
221_+4 202 _+4
243_+4 197 _+4
Dam lactation
1 2 3 4 5 6 plus
1159 992 694 418 262 216
12.8±0.2 13.5 _+0.2 13.8_+0.2 13.6_+0.2 13.7_+0.2 13.2 ± 0.3
25.6±0.4 26.8 _+0.4 27.1_+0.4 26.9±0.4 27.0_+0.5 26.4 _+0.5
203±5 212±5 217_+5 215±6 217±7 204 _+7
213±4 221_+4 222_+5 221_+5 220_+6 22O _+6
413 TABLE IV Multiplicative adjustment factors for growth traits of Chios sheep Main effect
Sub-class
Weaning weight
105-day weight
Growth rate Pre-weaning
Post-weaning
Month of birth
Sep.-Oct. Nov.-Dec. Jam-Feb. Mar.-May
1.00 1.02 1.05 1.06
1.00 1.03 1.10 1.14
1.00 1.04 1.09 1.13
1.00 1.03 1.14 1.20
Type of birth
Singles Twins Multiples
1.00 1.18 1.34
1.00 1.11 1.24
1.00 1.17 1.27
1.00 1.05 1.13
Sex of lamb
Males Females
1.00 1.09
1.00 1.15
1.00 1.09
1.00 1.23
1
1.07
1.06
1.07
1.03
2 3, 4 and 5 6 plus
1.02 1.00 1.05
1.01 1.00 1.02
1.02 1.00 1.06
1.00 1.00 1.00
Darn lactation
growth rate (Mavrogenis et al., 1980) provide some evidence for the above suggestion. Unlike, however, previous studies (Bichard and Cooper, 1966; Gjedrem, 1967; Mavrogenis and Louca, 1979; Mavrogenis et al., 1980) differences in post-weaning growth rate were significant between singles, twins and multiples. There were no changes in rank or scale between males and females for either weights or gains at any growth stage. Parity of dam had a significant quadratic effect on weaning weight (P < 0.01 ), pre-weaning growth rate ( P < 0.05 ) and 105-day weight. Post-weaning growth rate was not affected by dam lactation number (Table III ). Unlike sheep, dam parity has a much more lasting effect in goats (Moulick et al., 1966; Mavrogenis, 1982) until 140 days post-partum (Table I). Growth rate following weaning (adjusted for sex) was similar for all type-of-birth classes. When weaning weight was used as a covariate (adjusting for differences at weaning), 105-day weight was also independent of parity effects, which suggested that differences in 105-day weight were probably due to carry-over effects rather than dam lactation number. Adjustment factors computed across years for the effects of month of birth, type of birth, sex of lamb and parity of dam are presented in Table IV. Subclass means used in this table were the sum of the overall least-squares mean plus least-squares constants for main effects. They are expressed as ratios to male, single lambs born to fourth lactation (3-5) dams in autumn (September
414 and October). Similar adjustment factors have been developed by Notter et al. (1975) for 90-day lamb weight, except that they considered both type of birth and rearing. It was not considered appropriate to develop correction factors for the combined effects of type of birth and rearing for 2 reasons: very few lambs are reared artificially because of the high milking ability of the breed to raise all her offspring; in addition, although cross-fostering is not practiced frequently, all data coded as cross-fostered lambs were excluded from the analyses. Correction factors have been used extensively in dairy cattle. More recently, adjustment factors have been developed for milk production in dairy goats and live weight of lambs from mutton breeds. Both additive and multiplicative adjustment factors have been used and their merit has been discussed. The multiplicative adjustment factors developed in the present study are intended to be used for performance testing and should, therefore, be more appropriate than additive factors (Cundiff et al., 1966; Anderson and Willham, 1978). Since 105-day weight and post-weaning growth rate were better selection criteria than weaning weight and pre-weaning growth rate (Mavrogenis et al., 1980), it should be more appropriate to correct live weights (or gains) before selection is practiced. Adjustments for weaning weight should be used with caution because of the complex nature of the trait. Their application may be worth considering in suckling lamb operations since genetic effects for growth and maternal effects do not seem to be antagonistic (Mavrogenis, 1982). ACKNOWLEDGEMENTS The author wishes to acknowledge the valuable assistance of Messrs. Ph. Lysandrides and A. Roushias, and Mr. C. Heracleous for his contribution in data processing and analysis.
REFERENCES Anderson, J.H. and Willham, R.L., 1978.Weaning weight correction factors from Angusfield data. J. Anim. Sci., 47: 124-130. Bichard, M. and Cooper, M. McG., 1966. Analysis of production records from a lowland sheep flock. 1. Lamb 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. Eikje, E., 1971.Studies on Sheep Production Records. 1. Effect of environmental factors on weight of lambs. Acta Agric. Scand., 21: 26-32. Gjedrem, T., 1967. Phenotypic and genetic parameters for weights of lambs at five ages. Acta Agric. Scand., 17: 199-216. Lawlor, M.J., Louca, A. and Mavrogenis, A., 1974. The effect of three suckling regimes on the lactation performance of Cyprus fat-tailed, Chios and Awassi sheep and the growth rate of the lambs. Anim. Prod., 18: 293-299.
415 Mavrogenis, A.P., 1982. Environmentaland genetic factors influencingmilk production and lamb output of Chios sheep. Livest. Prod. Sci., 8: 519-527. Mavrogenis, A.P. and Louca, A., 1979. A note on some factors influencingpost-weaning performance of purebred and crossbred lambs. Anim. Prod., 29: 415-418. Mavrogenis, A.P., Louca, A. and Robison, O.W., 1980. Estimates of genetic parameters for preweaning and post-weaning growth traits of Chios lambs. Anim. Prod., 30: 271-276. Moulick, S.K., Guha, H., Gupta, S., Nitra, D.K. and Bhattacharya, S., 1966. Factors affecting multiple births 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. Anim. Sci., 40: 383-391. SAS, 1985. Statistical Analysis System, Users Guide, Version 5 Edition. SAS Institute Inc., Cary, NC.
RESUME Mavrogenis, A.P., 1988. Facteurs de correction pour les caract~res de croissance du mouton Chios. Livest. Prod. Sci., 19:409-416 (en anglais). On a utilis~ les r~sultats enregistr~s sur 3741 agneaux Chios h Athalassa et Orites pour calculer l'influence de l'ann~e, du mois et du mode de naissance, du sexe de l'agneau et du num~ro de lactation de la brebis sur la croissance des agneaux avant et apr~s le sevrage. La plupart de ces facteurs ont eu une influence significative (P < 0.01 ) sur les poids des agneaux. Les effets troupeau n'ont ~t~ importants que pour le poids au sevrage mais l'ann~e et le mois de naissance ont eu des effets significatifs (P < 0.01 ) sur tousles poids. Le num~ro de lactation des brebis a eu un effet faible qui n'a plus ~t~ significatifsur la croissance apr~s le sevrage. Bien que les interactions ann~emois aient dt~ significatives dans tousles cas, elles n'ont pas modifi~ le classement. Les interactions mode de naissance-sexe n'ont ~t~ significatives pour aucun des caract~res. On a calcul~ des facteurs de correction intra-ann~e de naissance pour le mois et le mode de naissance, le sexe des agneaux et le num~ro de lactation des brebis. Les effets troupeau n'~tant pas significatifs, ces facteurs peuvent ~tre utiles dans les programmes de testage pour l'am~lioration des caract~res de croissance des moutons Chios. KURZFASSUNG Mavrogenis, A.P., 1988: Korrekturfaktoren filr Wachstumsmerkmale von Chios-Schafen. Livest. Prod. Sci., 19:409-416 (aufenglisch). Datenmaterial von 3741 reinrassigen Chios-L~nmern, gesammelt in Athalassa und Orites wurde dazu benutzt, die Einfltlsse Jahr, Monat, Geburtstyp, Geschlecht und Laktationsnummer der Mutterschafe auf Wachstumsmerkmale vor und nach dem Absetzen von L~immern zu bestimmen. Die Least-squares-Analyse zeigte, daft die meisten der untersuchten Einflul~faktoren einen signifikanten Effekt (P < 0.01 ) auf das Gewicht der L ~ m e r austiben. Herdeneffekte wirkten sich lediglich auf das Absetzgewicht aus, Geburtsjahr und -monat erwiesen sich dagegen als signifikant Ftir alle Gewichtsmerkmale (P < 0.01 ). Laktationsnummerneffekteyon Mutterschafen zeigten sich als gering und nicht signifikant ftir die Wachstumsrate nach dem Absetzen. Obwohl Jahr und Monat Interaktionen in alien Fiillen signifikant waren, wurden keine Ver~inderungen im Rang festgestellt. Interaktionen zwischen Geburtstyp und Geschlecht waren ffir keines der untersuchten Merkmale signifikant. Korrekturfaktoren wurden innerhalb des Geburtsjahres fiir die Effekte Geburtsmonat, Geburts-
416 typ, Geschlecht des Lammes und Laktationsnummer der Mutterschafe berechnet. Da Herdeneffekte sich als nicht signifikant erwiesen, kSnnten diese multiplikativen Korrekturfaktoren in Leistungsprtifungsprogrammen zur Verbesserung von Wachstumsmerkmalen der Chios-Rasse benutzt werden.
409
Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
Adjustment Factors for Growth Traits of Chios Sheep A.P. MAVROGENIS
Agricultural Research Institute, Nicosia (Cyprus) (Accepted 30 December 1987)
ABSTRACT Mavrogenis, A.P., 1988. Adjustment factors for growth traits of Chios sheep. Livest. Prod. Sci., 19: 409-416. Data on 3741 purebred Chios lambs, collected at Athalassa and Orites, were used to determine the effects of year, month and type of birth, sex of lamb and dam lactation number on pre-weaning and post-weaning growth traits of sheep. Least-squares analyses revealed that most of the factors studied had a significant effect (P < 0.01 ) on lamb live weights. Flock effects were important for weaning weight only, but year and month of birth were significant for all live weights (P < 0.01 ). Dam lactation number effects were small and insignificant for post-weaning growth rate alone. Although year-by-month interactions were in all cases significant, no changes in rank were detected. Type of birth-by-sex interaction was not significant for any of the traits studied. Adjustment factors were computed across year of birth for the effects of month of birth, type of birth, sex of lamb and dam lactation number. Since flock effects were insignificant, these multiplicative adjustment factors could be used in performance testing programs for the improvement of growth traits in Chios sheep.
INTRODUCTION
To improve breeding value, selection must be based on genotypic rather than environmental superiority. It is well documented that corrections for classifiable sources of variation render selection and culling more accurate and should be removed by the use of suitable adjustment factors (Notter et al., 1975). Adjustment factors may be developed for similar management-feeding regimes, although each regime may possess its own specificities. The Chios breed is found in mainland Greece, on some of the Greek islands, at the coastal area of Turkey and in Cyprus. It is characterized by high milk production and prolificacy (Lawlor et al., 1974; Mavrogenis and Louca, 1979; Mavrogenis, 1982 ) and it is mostly exploited as a dual purpose animal. Lamb growth is considered satisfatory (Mavrogenis and Louca, 1979; Mavrogenis et al., 1980; Mavrogenis, 1982 ). The breed thrives under semi-intensive or inten0301-6226/88/$03.50
© 1988 Elsevier Science Publishers B.V.
410
sive conditions, where better management and feeding are secured. Body weight and/or gain is, therefore, a character of equal economic importance to milk and must be considered in schemes aimed at improving meat production. The purpose of this study was to identify classifiable sources of environmental variation influencing pre-weaning and post-weaning growth, and to develop suitable adjustment factors for growth traits in the Chios sheep. MATERIALS AND METHODS
The data were obtained at 2 experimental units of the Department of Agriculture (Athalassa and Orites). They represent weights and growth rates of 3741 lambs, born in 9 successive years (1978-1986), that were the progeny of 155 sires. The distribution of lambs within each year was similar and the family size was 22.3 lambs per sire. Different sires were used in each farm and their use was limited to a single year. All lambs were ear-tagged and their birth weight, sex, type of birth (single, twin or multiple), sire, dam and dam lactation number (1-9) were recorded. They were all weighed again at weaning ( 42 _ 3 days post-partum ) and at 105 days of age. Pre-weaning and post-weaning gains were calculated from live weights at the various stages of growth. All ewes were joined to vasectomized males for heat detection and oestrous ewes were hand mated to avoid matings between relatives and for pedigree purposes. The linear model used accounted for the effects of year and month of birth, flocks, sires within years and flocks, type of birth and sex of lamb, dam lactation number and a number of 2-way interactions. Years, sires within years and flocks and interactions containing years and error were considered random effects, while all other effects were considered fixed. Sub-class frequencies were unequal and, therefore, the method of least squares (S.A.S., 1985) was employed. Lambs born to ewes of >~6 lactations were grouped together. Moreover, only 3 classes for type of birth were considered (triplets, quadruplets and others were classed as multiples). Dam lactation number was preferred to age at lambing, since in practice it is more likely that livestock keepers will record lactation rather than age (in months or in years). In addition, age in years almost coincides with lactation number, particularly for early-maturing breeds. The effects of type of rearing and their interaction with type of birth were not considered in the statistical model. Although such classes were present in the data set, their effects could not be estimated with adequate accuracy because of their low frequency. Moreover, artificial rearing is not yet practiced on a large enough scale to require correction factors or the estimation of such effects. Although the effects of month of birth could be estimated for each month separately, it was considered more appropriate to group months into 4 classes, since not all months were represented in all years. No grazing of lambs was
411 practiced and sexes were kept together until 105 days of age. Following weaning, all lambs were fed on a concentrate mixture and barley hay and straw ad libitum. RESULTS AND DISCUSSION Mean squares and tests of significance for the traits studied are presented in Table I. Significant year effects were found for all live weights and gains and can be partly attributed to differences in sanitary conditions and other uncontrollable environmental factors. M o n t h of birth had a significant effect on all growth traits (Table II). Lambs born between September and December were mostly heavier and had faster growth rates before and after weaning than those born in spring ( M a r c h - M a y ) . Tail-enders are often penalized because of lower intakes due to higher ambient temperatures during and following weaning, which coincides with early summer. Males were always heavier ( P < 0.01 ) and had a faster pre-weaning and postweaning growth rate ( P < 0.01 ) than female lambs (Table III ). Growth differences between sexes have been well documented for all phases of the growth curve (Gjedrem, 1967; Eikje, 1971; Notter et al., 1975; Mavrogenis and Louca, 1979; Mavrogenis et al., 1980; Mavrogenis, 1982). Type of birth had a significant effect ( P < 0.01 ) on all live weights and gains. Weaning weight and pre-weaning growth rate may be influenced by non-genetic factors such as number of lambs suckling and milk capacity of the dam. Post-weaning growth rate should, however, be free of maternal and carry-over effects. The lower heritability estimates for weaning weight and pre-weaning TABLE I Mean squares and tests of significance for growth characters of Chios sheep Source Flocks Sires/flocks )
df 1 196 8 3 2 1 5 8 24 3492
Weaning weight
105-day weight
48.84**
0.49
1546.62"* 441.38"* 106.55"* 5879.19"* 838.22** 294.31"* 554.67** 317.73"* 8.55
8300.16"* 994.61"* 1680.16"* 11404.49** 10196.49** 672.06** 1944.94"* 1903.54"* 54.24
P r e - w e a n i n g Post-weaning growth rate growth rate 0.001
0.003
0.548** 0.064** 0.102"* 1.195"* 0.242** 0.065** 0.078** 0.126"* 0.003
1.350"* 0.169"* 0.230** 0.236** 1.459"* 0.028 0.376** 0.483** 0.009
412 T A B L E II Least-squares means and standard errors for growth traits of Chios sheep Main effect
Sub-class
No. of observations
Weaning weight (kg)
105-day weight (kg)
Growth rate (g day 1) Pre-weaning
Post-weaning
252 327 373 401 451 381 489 518 549
14.5 _+0.9 14.8_+0.8 14.1 _+0.6 12.8_+ 0.5 13.7 _+0.5 12.5_+0.6 12.6±0.7 12.8_+0.8 13.1 _+0.7
24.2 ± 1.8 28.2_+1.6 27.1 _+ 1.2 25.3 _+ 1.1 28.3 ± 1.1 26.4 ± 1.3 27.3 _+1.4 26.8_+1.7 26.6_+1.5
198_+32 230_+ 29 214_+ 22 203 _+19 224_+ 19 205_+ 22 203 _+25 209 ±31 215 ± 27
184±22 227 _+19 228_+ 15 204_+ 13 238_+ 13 224± 15 234_+ 17 223_+ 21 216_+ 19
Year
1977/78 1978/79 1979/80 1980/81 1981/82 1982/83 1983/84 1984/85 1985/86
Month
Sep.-Oct. Nov.-Dec. Jan.-Feb. Mar.-May
1822 511 1214 194
13.9_+0.2 13.6±0.3 13.2_+0.2 13.1 _+0.2
28.3±0.3 27.6_+0.5 25.8_+0.4 24.9 _+0.6
224_+4 216_+8 205_+5 199_+8
239_+4 231±6 210±5 199_+7
Flock
Athalassa Akhelia
1719 2022
13.2 _+0.2 13.6 _+0.2
26.9 _+0.3 27.9 _+0.3
213_+4 217_+4
222_+4 237_+4
T A B L E III Least-squares means and standard errors for growth traits of Chios lambs Main effect
Sub-class
No. of Weaning observations weight (kg)
105-day weight (kg)
Growth rate (g d a y - 1) Pre-weaning
Post-weaning
Type of birth
Singles Twins Multiples
990 2093 658
15.6 _+0.2 13.2 _+0.2 11.6 _+0.2
29.6 _+0.4 26.6 _+0.3 23.9 _+0.4
242_+4 206 -+ 4 186±5
232±4 222 ± 4 205±4
Sex of lamb
Males Females
1899 1842
14.0 _+0.2 12.9 ± 0.2
28.6 _+0.3 24.8 _+0.3
221_+4 202 _+4
243_+4 197 _+4
Dam lactation
1 2 3 4 5 6 plus
1159 992 694 418 262 216
12.8±0.2 13.5 _+0.2 13.8_+0.2 13.6_+0.2 13.7_+0.2 13.2 ± 0.3
25.6±0.4 26.8 _+0.4 27.1_+0.4 26.9±0.4 27.0_+0.5 26.4 _+0.5
203±5 212±5 217_+5 215±6 217±7 204 _+7
213±4 221_+4 222_+5 221_+5 220_+6 22O _+6
413 TABLE IV Multiplicative adjustment factors for growth traits of Chios sheep Main effect
Sub-class
Weaning weight
105-day weight
Growth rate Pre-weaning
Post-weaning
Month of birth
Sep.-Oct. Nov.-Dec. Jam-Feb. Mar.-May
1.00 1.02 1.05 1.06
1.00 1.03 1.10 1.14
1.00 1.04 1.09 1.13
1.00 1.03 1.14 1.20
Type of birth
Singles Twins Multiples
1.00 1.18 1.34
1.00 1.11 1.24
1.00 1.17 1.27
1.00 1.05 1.13
Sex of lamb
Males Females
1.00 1.09
1.00 1.15
1.00 1.09
1.00 1.23
1
1.07
1.06
1.07
1.03
2 3, 4 and 5 6 plus
1.02 1.00 1.05
1.01 1.00 1.02
1.02 1.00 1.06
1.00 1.00 1.00
Darn lactation
growth rate (Mavrogenis et al., 1980) provide some evidence for the above suggestion. Unlike, however, previous studies (Bichard and Cooper, 1966; Gjedrem, 1967; Mavrogenis and Louca, 1979; Mavrogenis et al., 1980) differences in post-weaning growth rate were significant between singles, twins and multiples. There were no changes in rank or scale between males and females for either weights or gains at any growth stage. Parity of dam had a significant quadratic effect on weaning weight (P < 0.01 ), pre-weaning growth rate ( P < 0.05 ) and 105-day weight. Post-weaning growth rate was not affected by dam lactation number (Table III ). Unlike sheep, dam parity has a much more lasting effect in goats (Moulick et al., 1966; Mavrogenis, 1982) until 140 days post-partum (Table I). Growth rate following weaning (adjusted for sex) was similar for all type-of-birth classes. When weaning weight was used as a covariate (adjusting for differences at weaning), 105-day weight was also independent of parity effects, which suggested that differences in 105-day weight were probably due to carry-over effects rather than dam lactation number. Adjustment factors computed across years for the effects of month of birth, type of birth, sex of lamb and parity of dam are presented in Table IV. Subclass means used in this table were the sum of the overall least-squares mean plus least-squares constants for main effects. They are expressed as ratios to male, single lambs born to fourth lactation (3-5) dams in autumn (September
414 and October). Similar adjustment factors have been developed by Notter et al. (1975) for 90-day lamb weight, except that they considered both type of birth and rearing. It was not considered appropriate to develop correction factors for the combined effects of type of birth and rearing for 2 reasons: very few lambs are reared artificially because of the high milking ability of the breed to raise all her offspring; in addition, although cross-fostering is not practiced frequently, all data coded as cross-fostered lambs were excluded from the analyses. Correction factors have been used extensively in dairy cattle. More recently, adjustment factors have been developed for milk production in dairy goats and live weight of lambs from mutton breeds. Both additive and multiplicative adjustment factors have been used and their merit has been discussed. The multiplicative adjustment factors developed in the present study are intended to be used for performance testing and should, therefore, be more appropriate than additive factors (Cundiff et al., 1966; Anderson and Willham, 1978). Since 105-day weight and post-weaning growth rate were better selection criteria than weaning weight and pre-weaning growth rate (Mavrogenis et al., 1980), it should be more appropriate to correct live weights (or gains) before selection is practiced. Adjustments for weaning weight should be used with caution because of the complex nature of the trait. Their application may be worth considering in suckling lamb operations since genetic effects for growth and maternal effects do not seem to be antagonistic (Mavrogenis, 1982). ACKNOWLEDGEMENTS The author wishes to acknowledge the valuable assistance of Messrs. Ph. Lysandrides and A. Roushias, and Mr. C. Heracleous for his contribution in data processing and analysis.
REFERENCES Anderson, J.H. and Willham, R.L., 1978.Weaning weight correction factors from Angusfield data. J. Anim. Sci., 47: 124-130. Bichard, M. and Cooper, M. McG., 1966. Analysis of production records from a lowland sheep flock. 1. Lamb 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. Eikje, E., 1971.Studies on Sheep Production Records. 1. Effect of environmental factors on weight of lambs. Acta Agric. Scand., 21: 26-32. Gjedrem, T., 1967. Phenotypic and genetic parameters for weights of lambs at five ages. Acta Agric. Scand., 17: 199-216. Lawlor, M.J., Louca, A. and Mavrogenis, A., 1974. The effect of three suckling regimes on the lactation performance of Cyprus fat-tailed, Chios and Awassi sheep and the growth rate of the lambs. Anim. Prod., 18: 293-299.
415 Mavrogenis, A.P., 1982. Environmentaland genetic factors influencingmilk production and lamb output of Chios sheep. Livest. Prod. Sci., 8: 519-527. Mavrogenis, A.P. and Louca, A., 1979. A note on some factors influencingpost-weaning performance of purebred and crossbred lambs. Anim. Prod., 29: 415-418. Mavrogenis, A.P., Louca, A. and Robison, O.W., 1980. Estimates of genetic parameters for preweaning and post-weaning growth traits of Chios lambs. Anim. Prod., 30: 271-276. Moulick, S.K., Guha, H., Gupta, S., Nitra, D.K. and Bhattacharya, S., 1966. Factors affecting multiple births 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. Anim. Sci., 40: 383-391. SAS, 1985. Statistical Analysis System, Users Guide, Version 5 Edition. SAS Institute Inc., Cary, NC.
RESUME Mavrogenis, A.P., 1988. Facteurs de correction pour les caract~res de croissance du mouton Chios. Livest. Prod. Sci., 19:409-416 (en anglais). On a utilis~ les r~sultats enregistr~s sur 3741 agneaux Chios h Athalassa et Orites pour calculer l'influence de l'ann~e, du mois et du mode de naissance, du sexe de l'agneau et du num~ro de lactation de la brebis sur la croissance des agneaux avant et apr~s le sevrage. La plupart de ces facteurs ont eu une influence significative (P < 0.01 ) sur les poids des agneaux. Les effets troupeau n'ont ~t~ importants que pour le poids au sevrage mais l'ann~e et le mois de naissance ont eu des effets significatifs (P < 0.01 ) sur tousles poids. Le num~ro de lactation des brebis a eu un effet faible qui n'a plus ~t~ significatifsur la croissance apr~s le sevrage. Bien que les interactions ann~emois aient dt~ significatives dans tousles cas, elles n'ont pas modifi~ le classement. Les interactions mode de naissance-sexe n'ont ~t~ significatives pour aucun des caract~res. On a calcul~ des facteurs de correction intra-ann~e de naissance pour le mois et le mode de naissance, le sexe des agneaux et le num~ro de lactation des brebis. Les effets troupeau n'~tant pas significatifs, ces facteurs peuvent ~tre utiles dans les programmes de testage pour l'am~lioration des caract~res de croissance des moutons Chios. KURZFASSUNG Mavrogenis, A.P., 1988: Korrekturfaktoren filr Wachstumsmerkmale von Chios-Schafen. Livest. Prod. Sci., 19:409-416 (aufenglisch). Datenmaterial von 3741 reinrassigen Chios-L~nmern, gesammelt in Athalassa und Orites wurde dazu benutzt, die Einfltlsse Jahr, Monat, Geburtstyp, Geschlecht und Laktationsnummer der Mutterschafe auf Wachstumsmerkmale vor und nach dem Absetzen von L~immern zu bestimmen. Die Least-squares-Analyse zeigte, daft die meisten der untersuchten Einflul~faktoren einen signifikanten Effekt (P < 0.01 ) auf das Gewicht der L ~ m e r austiben. Herdeneffekte wirkten sich lediglich auf das Absetzgewicht aus, Geburtsjahr und -monat erwiesen sich dagegen als signifikant Ftir alle Gewichtsmerkmale (P < 0.01 ). Laktationsnummerneffekteyon Mutterschafen zeigten sich als gering und nicht signifikant ftir die Wachstumsrate nach dem Absetzen. Obwohl Jahr und Monat Interaktionen in alien Fiillen signifikant waren, wurden keine Ver~inderungen im Rang festgestellt. Interaktionen zwischen Geburtstyp und Geschlecht waren ffir keines der untersuchten Merkmale signifikant. Korrekturfaktoren wurden innerhalb des Geburtsjahres fiir die Effekte Geburtsmonat, Geburts-
416 typ, Geschlecht des Lammes und Laktationsnummer der Mutterschafe berechnet. Da Herdeneffekte sich als nicht signifikant erwiesen, kSnnten diese multiplikativen Korrekturfaktoren in Leistungsprtifungsprogrammen zur Verbesserung von Wachstumsmerkmalen der Chios-Rasse benutzt werden.