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Factors affecting milk production and prolificacy of Alpine goats in Lombardy (Italy)
Small Ruminant Research 32 (1999) 83±88
Factors affecting milk production and proli®cacy of Alpine goats in Lombardy (Italy) P. Crepaldi*, M. Corti, M. Cicogna Istituto di Zootecnia Generale, FacoltaÁ di Agraria, UniversitaÁ degli Studi, via Celoria 2, I-20133, Milan, Italy Accepted 7 July 1998
Abstract In order to evaluate the adaptation of a newly introduced breed and of a production system, the effects of herd-year, season of kidding, parity, and, where appropriate, proli®cacy on milk yield, lactation length and proli®cacy of Alpine goats in the Italian region of Lombardy were investigated. Analysis of two consecutive years, 1298 lactation records, from 34 herds, gave mean values (SE) of 5676 kg for milk yield, 2311 days for lactation length and 1.60.01 kids per kidding. Milk yield and lactation length were primarily in¯uenced by the herd-year factor (p<0.001, partial R2 0.68 and 0.55, respectively) which mainly re¯ects differences in herd management. Milk yield was also affected by season of kidding (p<0.001, partial R2 0.4), parity (p<0.001, partial R2 0.03) and litter size (p<0.001, partial R2 0.01). Lactation length was also affected by parity (p<0.001 R2 0.16) and season of kidding (p<0.001 R2 0.06). Proli®cacy was affected by parity and by herd-year factor (p<0.001, partial R2 0.09). Kidding early in the year gave higher milk yields, longer lactations and higher proli®cacy, but in the choice of the kidding season also the higher prices of kid meat just before Easter have to be considered. Maximum milk yield and proli®cacy were attained late (in 4th and 5th lactation), probably due to early age at ®rst kidding. The relevant effect of the herd-year factor indicates that performances of Alpine goats in Lombardy can be successfully improved with an adequate management. Our ®ndings con®rm that litter size should not be ignored when establishing correction factors in order to compare milk yields. # 1999 Elsevier Science B.V. All rights reserved. Keywords: Alpine goat; Milk production; Lactation length; Proli®cacy
1. Introduction Dairy goat farming on a commercial basis has been recently introduced into sub-alpine areas of Lombardy. This was achieved in the 1970s when importation of specialised dairy goat breeds, such as the Alpine and Saanen, and the adoption of more intensive management techniques occurred (Enne et al., 1988; Gallarati Scotti and Corti, 1989). *Corresponding author. Fax: +39-02-70638083; e-mail: [email protected]
In respect to the previous extensive system used with local breeds, the more intensive one, with zero or minimum grazing, is adopted with exotic breeds: at most grazing is limited to few hours a day, from Spring to Autumn, in a pasture area with electric fencing close to the farm. Goats are kept in groups usually on a deep litter. Concentrate are largely used (with an average of 0.9 kg/head/day during lactation, ranging from a minimum of 0.2 to a maximum of 1.7 kg/head/ day) as well as hay (with an average of 2.4 kg/head/ day during lactation, ranging from a minimum of 2.1 to a maximum of 2.8 kg/head/day); silages are never
0921-4488/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved. PII: S0921-4488(98)00156-4
84
P. Crepaldi et al. / Small Ruminant Research 32 (1999) 83±88
used. Only about one-third of the farms is equipped with milking machine. The kids are not allowed to suckle and milk replacer are used by most farmers. Average live weight of kids at slaughtering is 12 kg. Meat production from kids is seasonal and the proportion of gross income from meat is about 45%. Young goats are usually sold at 3±4 months of age or, less frequently, when pregnant. The Alpine breed was ®rst introduced, mainly from France, 10±12 years before this study took place. At that time A.I. was not yet practiced and bucks of local origin were actively exchanged between herds all over the region. Thus, the population studied could be considered relatively isolated and homogeneous with respect to genetic origin. Also climatic conditions were quite homogeneous; the farms examined are located at an average altitude of 500 m above sealevel, in the sub-alpine area of Lombardy. The average annual rainfall is 1400±2200 mm and the average annual temperature 9±118C. The coldest month is January and the warmest is July. Differences between herds could be mostly associated with different levels of management. In order to evaluate the adaptation both of a newly introduced breed and of a more intense production system, some factors that might affect milk yield and proli®cacy were studied in Alpine goats of Lombardy. 2. Material and methods Available data recorded in 1987 and 1988 on all the of®cially registered goats of the Alpine breed in the four sub-alpine provinces of Lombardy (Bergamo, Brescia, Como and Varese) were considered. After an initial screening, records with discrepancies between Herd Book and Milk recording data and those from 10 herds with less than six records were discarded. The ®nal sample was composed of 1298 lactations from 34 herds. Analyzed traits included milk yield (kg), lactation length (days) and proli®cacy (litter size). Lactation records, referred to an effective lactation length, were estimated according to method A4 as prescribed by the International Committee for Recording the Productivity of Milk Animals. Of a number of factors that may affect the productivity of goats, herd-year, season of kidding and parity
were considered. For milk yield and lactation length even proli®cacy (litter size) was studied as a potential factor of different production. The dependent variables (Yijklm) were analysed with PROC GLM of SAS (1994) software according to the following model with all possible second order interactions: yijklm m HYij Sk Ll Pm HYSijk HYLijl HYPijm SLkl SPkm LPlm eijklm where y(ijklm)milk yield (kg), lactation length (days) and proli®cacy (no. kids/kidding); mthe population mean; HYijthe ®xed effect of the herd (i1, , 34) and year of production (j1[1987], 2[1988]); Skthe ®xed effect of the season (k1 [Winter from January to February], 2 [Spring from March to April], 3 [Summer from May to July]); Llthe ®xed effect of the lactation number or parity (l1, , 6 and over); Pmthe ®xed effect of proli®cacy as litter size (m1 [singles], 2 [twin and litters >2]); obviously this effect was excluded from the model when proli®cacy was the dependent variable; (HYS)ijk, (HYL)ijl, (HYP)ijm, (SL)kl, (SP)km, (LP)lmsecond order interactions; eijklmresidual. The model has empty cells and unbalanced structure, for example, the herd-year factor had only 54 levels instead of the expected 68 (2 years by 34 herds). The signi®cant second order interactions were (HYP)ijm on the dependent variables milk yield and proli®cacy and (HYS)ijk on lactation length. Because in unbalanced models most interactions are meaningless, in order to better estimate the effects of the principal factors a model without interactions was ®nally adopted. The contribution of each factor to the variation of the dependent variable was indicated as partial R2, and the differences between levels of each factor were assessed by Scheffe's test. 3. Results and discussion The 1298 lactations studied showed a mean value (SE) of 5676 kg for milk yield, of 2311 days for lactation length and a proli®cacy of 1.60.01 kids per kidding. It is worth mentioning that these average performances are very similar to those recorded in
P. Crepaldi et al. / Small Ruminant Research 32 (1999) 83±88
85
Fig. 1. Frequency distribution of age at first kidding (total no. 287 goats).
France in the same breed and years, that is, 589 kg for milk yield and 237 days for lactation length (UCARDEC, 1998). Goats showed a similar age at ®rst kidding (Fig. 1), except for the few that were too young during the ®rst breeding season. In fact, in the considered rearing system, goats are bred during their ®rst year of life, but those born late in the year due to late breeding of their mothers, may delay ®rst kidding by 1 year. In the same area goats of local breeds (Orobica, Bionda of Adamello and Verzasca) reared with extensive systems show a much higher age at ®rst kidding, since most of them are mated in the second year of life (Corti, unpublished observations). Least square means deviations and the signi®cance of the factors affecting milk yield, lactation length and proli®cacy are given in Table 1. Factors considered by the models explain 67% and 74% of the total variation for milk yield and lactation length, respectively, but only 19% for proli®cacy. 3.1. Milk yield Milk yield is primarily in¯uenced by the factor herd-year (partial R20.68, p<0.001) which mainly
re¯ects the different management systems, such as feeding and milking techniques. Most kiddings occurred in Winter (55%) and in Spring (40%) and season of kidding signi®cantly in¯uenced (p<0.001) milk yield (partial R20.4). Goats kidding early in the year had higher milk yields (Table 1), whereas goats that kidded in summer had the lowest yields. This can largely be attributed to the simultaneous onset of the breeding season, which is affected by seasonal factors and management decisions and obliges all goats to be dry by early Autumn. Thus, in the northern hemisphere kidding early in the year (i.e. January±February) is generally recognised as one of the main factors favouring milk production in goats, even in different rearing conditions (Steine, 1975; Alderson and Pollak, 1980; Montaldo et al., 1981; Bouloc, 1992; Mourad, 1992; Vecerova and Krizek, 1993; Niznikowski et al., 1994b). Milk yield was also affected by parity (partial R20.03; p<0.001) and by litter size (partial R20.01; p<0.001) (Table 1). The effect of parity on milk yield shows an almost steady growing trend from ®rst to ®fth lactation. The maximum milk yield is attained in the ®fth lactation, whereas a great deal of reported lactation records
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Table 1 Estimates of factors affecting milk yields, lactation lengths and prolificacy of Alpine goats raised in Lombardy, Italy Factor
No.
Milk yield (kg) Deviation
Lactation length (days) Deviation
Prolificacy (no. kids/kidding) Deviation
Overall LS mean Herd-Year Season of kidding Winter (Jan±Feb) Spring(March±April) Summer(May±June±July) Parity 1st 2nd 3d 4th 5th 6th and over No. of kids born/ kidding One Two±Four Model R2
1298
519.29 *** 2 R 0.68 *** 2 R 0.40 82.24a 12.43b ÿ94.66c *** 2 R 0.03 ÿ138.83a ÿ10.11b 33.49c 35.18d 56.55e 23.73d *** 2 R 0.01 ÿ16.44a 16.44b 0.67
199.57 *** 2 R 0.55 *** 2 R 0.06 39.30a 15.32b ÿ54.63c *** 2 R 0.16 ÿ8.02a 4.52b 2.26bc 1.46bc 3.17cd 2.92d NS ÿ0.956 0.956 0.74
1.537 *** 2 R 0.09 NS 0.331 ÿ0.005 0.02 *** 2 R 0.09 ÿ0.323a ÿ0.041b 0.102bc 0.140bc 0.087bc 0.036c ^
720 524 54 287 269 277 249 139 77 580 718
0.19
NS, not significant. p<0.001. ^, not included in the model. R2 for each factorpartial R2. a,b,c,d,e,f, values within each column and for each factor with different letters differ (p<0.05) at Scheffe's test. ***
obtained from different breeds and countries show that goats usually reach maximum milk yield at third day or, less frequently, at fourth lactation. (Subires et al., 1989; Cherix, 1990; Fresno et al., 1991; Montalvo Valdenegro et al., 1991; Bouloc, 1992; Niznikowski et al., 1994b.) Reports of milk yield increasing with age even in older goats are much less frequent; Vecerova and Krizek (1993), on 809 lactations from 248 Czech White Short-hair goats, found productivity increasing till 10th lactation; Raats et al. (1983), in a small group of Boer goats, found that milk production increased from second to sixth lactation; Finley et al. (1984), on 13,708 records from American Alpine, Saanen and Toggenburg goats observed maximum production between 24 and 50 month of age. Seventy percent of the goats in our study were young (between 11 and 15 months of age) at ®rst kidding (Fig. 1). This could partially explain a somewhat late attainment of a mature milk production level. It is worth considering that, even if kids are not allowed to suckle, milk yield was affected by proli®cacy, with about 32 kg more milk in goats with multiple birth (Table 1). Our ®ndings agree with those
of several authors who found that proli®cacy affected milk yield (Subires et al., 1988; Boichard et al., 1989; Mioc, 1991; Fresno et al., 1992; Vecerova and Krizek, 1993; Niznikowski et al., 1994a). In agreement with Subires et al. (1988), we found that twin kidders in ®rst lactation produced more than single kidders, with an average milk yield (SE) of kg 457.121.5 vs. 393.910.9, but this difference gets smaller in third lactation (kg 614.113.3 vs. 599.0817.3). 3.2. Lactation length Lactation length, as well as milk yield, were primarily in¯uenced by herd-year (p<0.001; partial R20.55), but also by parity (p<0.001; partial R20.16) and by season of kidding (p<0.001; partial R20.06). As expected early kidding gave longer lactations (Table 1). Mioc (1991), on a small number of goats (no. 89), recorded longer lactations for twinning vs. single kid goats, whereas in our sample proli®cacy did not signi®cantly affect lactation length.
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3.3. Prolificacy
Acknowledgements
In this study 44.7% of the goats gave birth to one kid only, whereas multiple births were recorded in 55.3% of the goats (twins: 51.5%, triplets: 3.7% or quadruplets: 0.1%). Proli®cacy was in¯uenced by parity (partial R20.09; p<0.001), with least square means increasing from 1.2 kids in goats kidding for the ®rst time, to 1.5 kids in second parity and about 1.7 in goats of 4th parity, but is also affected by the herd-year factor (partial R20.09; p<0.001). No signi®cant effect exerts the season of kidding even if the highest proli®cacy were registered for goats kidding in Winter and lower proli®cacy for late kidding. Steine (1975) in Norway found larger litter size in goats kidding in December± January.
The authors wish to thank the Provincial Breeders Associations of Bergamo, Brescia, Como and Varese for providing the recorded data and G.B. Muricchio for the work carried out while preparing his degree thesis. The study was supported by a grant from the National Research Council of Italy, in the context of the Milk Production Coordinated Research Unit.
4. Conclusions Goats kidding early in the year produced more milk, had longer lactations and higher proli®cacy, while lower yields, shorter lactations and lower proli®cacy were recorded for goats kidding in the Summer. Even if early kidding produces the best performances, the kidding season is chosen by taking into account that the local market offers higher prices for kid meat just before Easter. Our ®ndings show that maximum milk production is attained quite late, in ®fth lactation, whereas young goats tend to be mated quite early, probably when the body weight is still too low. In spite of a fairly homogeneous environment with respect to climate, herd-year effect was quite considerable. This probably because intensive goat rearing represents something new in the area and in many cases the farmer regards goat breeding only as a subsidiary activity that can be undertaken even without adequate structures and knowledge. Hence, in these conditions, performance does not yet ful®l its potential. On the other hand good results obtained from several herds indicate that Alpine goats can be successfully farmed in Lombardy when management is adequate. Our ®ndings con®rm that the litter size should not be ignored when establishing correction factors in order to compare milk yields.
References Alderson, A., Pollak, E.J., 1980. Age±season adjustment factors for milk and fat of dairy goats. J. Dairy Sci. 63, 148±151. Boichard, D., Bouloc, N., Ricordeau, G., Piacere, A., Barillet, F., 1989. Genetic parameters for first lactation dairy traits in the Alpine and Saanen goat breeds. GeÁneÁtique SeÁlection Evolution 21, 205±215. Bouloc, N., 1992. Courbes de lactation des cheÁvres: quelques eÂleÂments sur leur forme (Some factors affecting the lactation curve in goats). CheÁvre 193, 15±17. Cherix, P., 1990. Die EinfluÈsse einiger Umweltfaktoren auf die Milchleistung der Ziegen (Effects of some environmental factors on milk yield in goats). KleinviehzuÈchter 38, 67±74. Enne, G., Corti, M., Greppi, G.F., Bruni, G., Ponti, F., Pagani, M., 1988. L'allevamento caprino specializzato in Lombardia: situazione e prospettive (Specialised goat farming in Lombardy: present situation and prospects). Proc. VIII Cong. SIPAOC, Viterbo, 279±284. Finley, C.M., Thompson, J.R., Bradford, G.E., 1984. Age±parity± season adjustment factors for milk and fat yields od dairy goats. J. Dairy Sci. 67, 1868±1872. Fresno, M., Rodero, J.M., Serrano, I., Delgado, J.V., Capote, J., Rodero, A., 1991. EvolucioÂn de la produccioÂn de leche de la poblacioÂn caprina tinerfena seguuÂn algunos factores ambientales (Development of milk production in the Tenerife goat population in relationship to various environmental factors). Avances en AlimentacioÂn y Mejora Animal 31, 265±267. Fresno, M., Serrano, I., Rodero, J.M., Delgado, J.V., Capote, J., Rodero, A., Herrera, M., 1992. Efecto de algunos factores ambientales sobre la produccioÂn lechera de cabras tinerfenas (Effect of some environmental factors on milk yield of goats in Tenerife). Actas de las XVI Jornadas Cientificas, Sociedad EspanÄola de Ovinotecnia y Caprinotecnia Pamplona, Spain, september 1991, 369±373. Gallarati Scotti, G.C., Corti, M., 1989. Le razze caprine autoctone dell'area alpina lombarda e ticinese. (Autochtonous goat breeds of the Alpine area of Lombardy and Tessin), In: Greppi, G.F., Corti, M. (Eds.), Proc. XXIV Simp. Intern. di Zootec. Milan, Italy, 117±130. Mioc, B., 1991. Utjecaj pasmine i velicine legla na mlijecnost koza u prvoj laktaciji (Effect of races and number of kids on first lactation goat milk traits). Poljopprivredna Znanstvena Smotra 56, 3±4.
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Montaldo, H., Tapia, G., Juarez, A., 1981. Algunos factores geneticos y ambientales que influyen sobre la produccioÂn de leche y el intervalo entre partos en cabras. (Some genetic and environmental factors affecting milk yield and kidding interval in goats). Tecnica Pecuaria en MeÂxico 41, 32±44. Montalvo Valdenegro, H., Juarez Lozano, A., Sanchez y Garcia Figueroa, F., 1991. CorreccioÂn de lactancias para edad y epoca de parto en programas de seleccioÂn de cabras en Mexico (Correction of milk yields for age and season of kidding in selection programmes for goats in Mexico). Vet. Mexico 22, 279±283. Mourad, M., 1992. Effects of month of kidding, parity and litter size on milk yield of Alpine goats in Egypt. Small Rumin. Res. 8, 41±46. Niznikowski, R., Rant, W., Samitowska, R., Migielska, H., 1994a. Preliminary characteristics of some factors affecting milk performance of goats bred in Opole district, Poland. I. The sources of variances and correlations between traits, Ann. Warsaw Agric. Univ., SGGW AR, Anim. Sci. 30, 69±73. Niznikowski, R., Rant, W., Samitowska, R., Migielska, H., 1994b. Preliminary characteristics of some factors affecting milk performance of goats bred in Opole district, Poland. II. The effect of genotype, number of lactation, month of kidding and litter size, Ann. Warsaw Agric. Univ., SGGW AR, Anim. Sci. 30, 75±80.
Raats, J.G., Wilke, P.I., Du Toit, J.E.J., 1983. The effect of age and litter size on milk production in Boer goats. South African Journal of Animal Science 13, 240±243. TM SAS, 1994. SAS/STAT User's Guide. Release 6.10. SAS Institute Inc., Cary, NC, USA. Steine, T.A., 1975. Faktorar med innverknad pa oekonomisk viktige eigenskapar hos geit (Factors affecting characters of economic importance in goats). Meldinger fra Norges Landbrukshoegskole 54(2), 30. Subires, J., Lara, L., Ferrando, G., Boza, J., 1988. Factores que condicionan la productividad lechera de la cabra. Numero de lactatioÂn y tipo de parto (Factors affecting milk yield in goats. Lactation number and type of kidding). Archivos de Zootecnia 37, 145±153. Subires, J., Lara, L., Ferrando, G., Boza, J., 1989. Factores que condicionan la productividad lechera de la cabra II. Efecto de la edad y del tipo de parto sobre la produccioÂn lechera (Factors affecting milk yield in goats. 2. Effect of age and type of parturition on milk yield). Archivos de Zootecnia 38, 237±248. UCARDEC, 1998. (Unite de Coordination des Actions de CoopeÂration en Recherche et DeÂveloppement Caprins, Paris) personal communication. Vecerova, D., Krizek, J., 1993. Analyza variance miecne uzitkovosti koz bileho kratkosrsteho plemene (Analysis of variation in milk production by goats of the White Short-haired breed). Zivocisna Vyroba 38, 961±969.
Factors affecting milk production and proli®cacy of Alpine goats in Lombardy (Italy) P. Crepaldi*, M. Corti, M. Cicogna Istituto di Zootecnia Generale, FacoltaÁ di Agraria, UniversitaÁ degli Studi, via Celoria 2, I-20133, Milan, Italy Accepted 7 July 1998
Abstract In order to evaluate the adaptation of a newly introduced breed and of a production system, the effects of herd-year, season of kidding, parity, and, where appropriate, proli®cacy on milk yield, lactation length and proli®cacy of Alpine goats in the Italian region of Lombardy were investigated. Analysis of two consecutive years, 1298 lactation records, from 34 herds, gave mean values (SE) of 5676 kg for milk yield, 2311 days for lactation length and 1.60.01 kids per kidding. Milk yield and lactation length were primarily in¯uenced by the herd-year factor (p<0.001, partial R2 0.68 and 0.55, respectively) which mainly re¯ects differences in herd management. Milk yield was also affected by season of kidding (p<0.001, partial R2 0.4), parity (p<0.001, partial R2 0.03) and litter size (p<0.001, partial R2 0.01). Lactation length was also affected by parity (p<0.001 R2 0.16) and season of kidding (p<0.001 R2 0.06). Proli®cacy was affected by parity and by herd-year factor (p<0.001, partial R2 0.09). Kidding early in the year gave higher milk yields, longer lactations and higher proli®cacy, but in the choice of the kidding season also the higher prices of kid meat just before Easter have to be considered. Maximum milk yield and proli®cacy were attained late (in 4th and 5th lactation), probably due to early age at ®rst kidding. The relevant effect of the herd-year factor indicates that performances of Alpine goats in Lombardy can be successfully improved with an adequate management. Our ®ndings con®rm that litter size should not be ignored when establishing correction factors in order to compare milk yields. # 1999 Elsevier Science B.V. All rights reserved. Keywords: Alpine goat; Milk production; Lactation length; Proli®cacy
1. Introduction Dairy goat farming on a commercial basis has been recently introduced into sub-alpine areas of Lombardy. This was achieved in the 1970s when importation of specialised dairy goat breeds, such as the Alpine and Saanen, and the adoption of more intensive management techniques occurred (Enne et al., 1988; Gallarati Scotti and Corti, 1989). *Corresponding author. Fax: +39-02-70638083; e-mail: [email protected]
In respect to the previous extensive system used with local breeds, the more intensive one, with zero or minimum grazing, is adopted with exotic breeds: at most grazing is limited to few hours a day, from Spring to Autumn, in a pasture area with electric fencing close to the farm. Goats are kept in groups usually on a deep litter. Concentrate are largely used (with an average of 0.9 kg/head/day during lactation, ranging from a minimum of 0.2 to a maximum of 1.7 kg/head/ day) as well as hay (with an average of 2.4 kg/head/ day during lactation, ranging from a minimum of 2.1 to a maximum of 2.8 kg/head/day); silages are never
0921-4488/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved. PII: S0921-4488(98)00156-4
84
P. Crepaldi et al. / Small Ruminant Research 32 (1999) 83±88
used. Only about one-third of the farms is equipped with milking machine. The kids are not allowed to suckle and milk replacer are used by most farmers. Average live weight of kids at slaughtering is 12 kg. Meat production from kids is seasonal and the proportion of gross income from meat is about 45%. Young goats are usually sold at 3±4 months of age or, less frequently, when pregnant. The Alpine breed was ®rst introduced, mainly from France, 10±12 years before this study took place. At that time A.I. was not yet practiced and bucks of local origin were actively exchanged between herds all over the region. Thus, the population studied could be considered relatively isolated and homogeneous with respect to genetic origin. Also climatic conditions were quite homogeneous; the farms examined are located at an average altitude of 500 m above sealevel, in the sub-alpine area of Lombardy. The average annual rainfall is 1400±2200 mm and the average annual temperature 9±118C. The coldest month is January and the warmest is July. Differences between herds could be mostly associated with different levels of management. In order to evaluate the adaptation both of a newly introduced breed and of a more intense production system, some factors that might affect milk yield and proli®cacy were studied in Alpine goats of Lombardy. 2. Material and methods Available data recorded in 1987 and 1988 on all the of®cially registered goats of the Alpine breed in the four sub-alpine provinces of Lombardy (Bergamo, Brescia, Como and Varese) were considered. After an initial screening, records with discrepancies between Herd Book and Milk recording data and those from 10 herds with less than six records were discarded. The ®nal sample was composed of 1298 lactations from 34 herds. Analyzed traits included milk yield (kg), lactation length (days) and proli®cacy (litter size). Lactation records, referred to an effective lactation length, were estimated according to method A4 as prescribed by the International Committee for Recording the Productivity of Milk Animals. Of a number of factors that may affect the productivity of goats, herd-year, season of kidding and parity
were considered. For milk yield and lactation length even proli®cacy (litter size) was studied as a potential factor of different production. The dependent variables (Yijklm) were analysed with PROC GLM of SAS (1994) software according to the following model with all possible second order interactions: yijklm m HYij Sk Ll Pm HYSijk HYLijl HYPijm SLkl SPkm LPlm eijklm where y(ijklm)milk yield (kg), lactation length (days) and proli®cacy (no. kids/kidding); mthe population mean; HYijthe ®xed effect of the herd (i1, , 34) and year of production (j1[1987], 2[1988]); Skthe ®xed effect of the season (k1 [Winter from January to February], 2 [Spring from March to April], 3 [Summer from May to July]); Llthe ®xed effect of the lactation number or parity (l1, , 6 and over); Pmthe ®xed effect of proli®cacy as litter size (m1 [singles], 2 [twin and litters >2]); obviously this effect was excluded from the model when proli®cacy was the dependent variable; (HYS)ijk, (HYL)ijl, (HYP)ijm, (SL)kl, (SP)km, (LP)lmsecond order interactions; eijklmresidual. The model has empty cells and unbalanced structure, for example, the herd-year factor had only 54 levels instead of the expected 68 (2 years by 34 herds). The signi®cant second order interactions were (HYP)ijm on the dependent variables milk yield and proli®cacy and (HYS)ijk on lactation length. Because in unbalanced models most interactions are meaningless, in order to better estimate the effects of the principal factors a model without interactions was ®nally adopted. The contribution of each factor to the variation of the dependent variable was indicated as partial R2, and the differences between levels of each factor were assessed by Scheffe's test. 3. Results and discussion The 1298 lactations studied showed a mean value (SE) of 5676 kg for milk yield, of 2311 days for lactation length and a proli®cacy of 1.60.01 kids per kidding. It is worth mentioning that these average performances are very similar to those recorded in
P. Crepaldi et al. / Small Ruminant Research 32 (1999) 83±88
85
Fig. 1. Frequency distribution of age at first kidding (total no. 287 goats).
France in the same breed and years, that is, 589 kg for milk yield and 237 days for lactation length (UCARDEC, 1998). Goats showed a similar age at ®rst kidding (Fig. 1), except for the few that were too young during the ®rst breeding season. In fact, in the considered rearing system, goats are bred during their ®rst year of life, but those born late in the year due to late breeding of their mothers, may delay ®rst kidding by 1 year. In the same area goats of local breeds (Orobica, Bionda of Adamello and Verzasca) reared with extensive systems show a much higher age at ®rst kidding, since most of them are mated in the second year of life (Corti, unpublished observations). Least square means deviations and the signi®cance of the factors affecting milk yield, lactation length and proli®cacy are given in Table 1. Factors considered by the models explain 67% and 74% of the total variation for milk yield and lactation length, respectively, but only 19% for proli®cacy. 3.1. Milk yield Milk yield is primarily in¯uenced by the factor herd-year (partial R20.68, p<0.001) which mainly
re¯ects the different management systems, such as feeding and milking techniques. Most kiddings occurred in Winter (55%) and in Spring (40%) and season of kidding signi®cantly in¯uenced (p<0.001) milk yield (partial R20.4). Goats kidding early in the year had higher milk yields (Table 1), whereas goats that kidded in summer had the lowest yields. This can largely be attributed to the simultaneous onset of the breeding season, which is affected by seasonal factors and management decisions and obliges all goats to be dry by early Autumn. Thus, in the northern hemisphere kidding early in the year (i.e. January±February) is generally recognised as one of the main factors favouring milk production in goats, even in different rearing conditions (Steine, 1975; Alderson and Pollak, 1980; Montaldo et al., 1981; Bouloc, 1992; Mourad, 1992; Vecerova and Krizek, 1993; Niznikowski et al., 1994b). Milk yield was also affected by parity (partial R20.03; p<0.001) and by litter size (partial R20.01; p<0.001) (Table 1). The effect of parity on milk yield shows an almost steady growing trend from ®rst to ®fth lactation. The maximum milk yield is attained in the ®fth lactation, whereas a great deal of reported lactation records
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Table 1 Estimates of factors affecting milk yields, lactation lengths and prolificacy of Alpine goats raised in Lombardy, Italy Factor
No.
Milk yield (kg) Deviation
Lactation length (days) Deviation
Prolificacy (no. kids/kidding) Deviation
Overall LS mean Herd-Year Season of kidding Winter (Jan±Feb) Spring(March±April) Summer(May±June±July) Parity 1st 2nd 3d 4th 5th 6th and over No. of kids born/ kidding One Two±Four Model R2
1298
519.29 *** 2 R 0.68 *** 2 R 0.40 82.24a 12.43b ÿ94.66c *** 2 R 0.03 ÿ138.83a ÿ10.11b 33.49c 35.18d 56.55e 23.73d *** 2 R 0.01 ÿ16.44a 16.44b 0.67
199.57 *** 2 R 0.55 *** 2 R 0.06 39.30a 15.32b ÿ54.63c *** 2 R 0.16 ÿ8.02a 4.52b 2.26bc 1.46bc 3.17cd 2.92d NS ÿ0.956 0.956 0.74
1.537 *** 2 R 0.09 NS 0.331 ÿ0.005 0.02 *** 2 R 0.09 ÿ0.323a ÿ0.041b 0.102bc 0.140bc 0.087bc 0.036c ^
720 524 54 287 269 277 249 139 77 580 718
0.19
NS, not significant. p<0.001. ^, not included in the model. R2 for each factorpartial R2. a,b,c,d,e,f, values within each column and for each factor with different letters differ (p<0.05) at Scheffe's test. ***
obtained from different breeds and countries show that goats usually reach maximum milk yield at third day or, less frequently, at fourth lactation. (Subires et al., 1989; Cherix, 1990; Fresno et al., 1991; Montalvo Valdenegro et al., 1991; Bouloc, 1992; Niznikowski et al., 1994b.) Reports of milk yield increasing with age even in older goats are much less frequent; Vecerova and Krizek (1993), on 809 lactations from 248 Czech White Short-hair goats, found productivity increasing till 10th lactation; Raats et al. (1983), in a small group of Boer goats, found that milk production increased from second to sixth lactation; Finley et al. (1984), on 13,708 records from American Alpine, Saanen and Toggenburg goats observed maximum production between 24 and 50 month of age. Seventy percent of the goats in our study were young (between 11 and 15 months of age) at ®rst kidding (Fig. 1). This could partially explain a somewhat late attainment of a mature milk production level. It is worth considering that, even if kids are not allowed to suckle, milk yield was affected by proli®cacy, with about 32 kg more milk in goats with multiple birth (Table 1). Our ®ndings agree with those
of several authors who found that proli®cacy affected milk yield (Subires et al., 1988; Boichard et al., 1989; Mioc, 1991; Fresno et al., 1992; Vecerova and Krizek, 1993; Niznikowski et al., 1994a). In agreement with Subires et al. (1988), we found that twin kidders in ®rst lactation produced more than single kidders, with an average milk yield (SE) of kg 457.121.5 vs. 393.910.9, but this difference gets smaller in third lactation (kg 614.113.3 vs. 599.0817.3). 3.2. Lactation length Lactation length, as well as milk yield, were primarily in¯uenced by herd-year (p<0.001; partial R20.55), but also by parity (p<0.001; partial R20.16) and by season of kidding (p<0.001; partial R20.06). As expected early kidding gave longer lactations (Table 1). Mioc (1991), on a small number of goats (no. 89), recorded longer lactations for twinning vs. single kid goats, whereas in our sample proli®cacy did not signi®cantly affect lactation length.
P. Crepaldi et al. / Small Ruminant Research 32 (1999) 83±88
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3.3. Prolificacy
Acknowledgements
In this study 44.7% of the goats gave birth to one kid only, whereas multiple births were recorded in 55.3% of the goats (twins: 51.5%, triplets: 3.7% or quadruplets: 0.1%). Proli®cacy was in¯uenced by parity (partial R20.09; p<0.001), with least square means increasing from 1.2 kids in goats kidding for the ®rst time, to 1.5 kids in second parity and about 1.7 in goats of 4th parity, but is also affected by the herd-year factor (partial R20.09; p<0.001). No signi®cant effect exerts the season of kidding even if the highest proli®cacy were registered for goats kidding in Winter and lower proli®cacy for late kidding. Steine (1975) in Norway found larger litter size in goats kidding in December± January.
The authors wish to thank the Provincial Breeders Associations of Bergamo, Brescia, Como and Varese for providing the recorded data and G.B. Muricchio for the work carried out while preparing his degree thesis. The study was supported by a grant from the National Research Council of Italy, in the context of the Milk Production Coordinated Research Unit.
4. Conclusions Goats kidding early in the year produced more milk, had longer lactations and higher proli®cacy, while lower yields, shorter lactations and lower proli®cacy were recorded for goats kidding in the Summer. Even if early kidding produces the best performances, the kidding season is chosen by taking into account that the local market offers higher prices for kid meat just before Easter. Our ®ndings show that maximum milk production is attained quite late, in ®fth lactation, whereas young goats tend to be mated quite early, probably when the body weight is still too low. In spite of a fairly homogeneous environment with respect to climate, herd-year effect was quite considerable. This probably because intensive goat rearing represents something new in the area and in many cases the farmer regards goat breeding only as a subsidiary activity that can be undertaken even without adequate structures and knowledge. Hence, in these conditions, performance does not yet ful®l its potential. On the other hand good results obtained from several herds indicate that Alpine goats can be successfully farmed in Lombardy when management is adequate. Our ®ndings con®rm that the litter size should not be ignored when establishing correction factors in order to compare milk yields.
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