Survey on the Sheep Milk Recording (2002)
The survey by the Milk Recording of Sheep Working focused on topics related to the terms of reference of the working group. The report points out the state of milk recording in ICAR countries, the increasing importance of simplification of milk recording, the great diversity in lactation calculation, the development of optional recordings such as milk composition and somatic cell counts, the few implementation of on-farm breeding schemes, the use molecular genetic, particularly the PrP genotyping
Report of the working group on milk recording of sheep
Since the approval in 1992 of the ICAR guidelines for milk recording in sheep, the working group on milk recording of sheep has carried out in 2002 a 5th survey, and used answers from 21 countries. The survey focused on topics related to the terms of reference of the working group. The report points out the state of milk recording in ICAR countries, the increasing importance of simplification of milk recording, the great diversity in lactation calculation, the development of optional recordings such as milk composition and somatic cell counts, the few implementation of on-farm breeding schemes, the use molecular genetic, particularly the PrP genotyping. Other activities of the working group have concerned the updating of the ICAR guidelines (introduction of D method) and co-operation with the sub-committee Recording Devices and the milk testing laboratories working group.
Depuis l’adoption en 1992 par le CICPE du règlement de contrôle laitier ovin, le groupe de travail sur le contrôle laitier ovin a réalisé en 2002 une cinquième enquête, et valorisé les réponses de 21 pays. L’enquête a focalisé sur des thèmes en relation avec les termes de référence du groupe de travail. Le rapport met l’accent sur l’état des lieux du contrôle laitier ovin dans les pays membres du CICPE, l’importance croissante de la simplification du contrôle laitier, la grande diversité dans les calculs de lactation, le développement des contrôles facultatifs tels que la composition chimique du lait et les comptages de cellules somatiques, le faible développement des schémas de sélection en ferme, l’utilisation de la génétique moléculaire, notamment le génotypage au locus PrP. Les autres activités du groupe de travail ont concerné la mise à jour du règlement ICAR (introduction du contrôle D), et la coopération avec le sous-comité éprouvettes et compteurs et le groupe de travail sur les méthodes d’analyse du lait en laboratoire.
Keywords: Dairy sheep, milk recording, breeding schemes
As every two years since 1994, the Working Group has carried out a fifth survey to be presented at the 33rd Biennial Session of ICAR. These biennial surveys allow to have a regular look on the state of milk recording in sheep in ICAR member countries and in some other countries. The questionnaire included topics related to the terms of reference : situation of milk recording in the different countries and breeds, simplification of milk recording, milk traits, optional dispositions regarding the guidelines (milk composition, somatic cell count, other traits), breeding value evaluation, artificial insemination (AI) and progeny tests.
The questionnaire has been sent to 43 ICAR member countries and 3 non ICAR countries. The report was written using 21 replies received from 20 ICAR members and 1 non ICAR member country respectively, i.e. a answer rate of 46 %. This rate may appear to be low, but we must remember that milk production from sheep does not exist or is not significant in several ICAR countries which therefore does not answer. Nevertheless, we regret that some important countries regarding the dairy sheep population, such as Portugal, do not answer the questionnaire. Moreover, answers from PECO countries should be very useful to have a look at the situation of dairy sheep production in post-communist countries.
Finally we report the activities of the Working Group during the last 2 years, dealing with the current terms of reference.
Survey of milk recording in dairy sheep
Situation of milk recording in dairy sheep
- Official milk recording (A or B or E method) is carried out in every country. The use of another type of milk recording (D method according to the new nomenclature approved in Barillet and Astruc, 1998)) is described in only two countries : France and Spain. In both cases, D recording is implemented in addition to the official one. The D method practiced in France consists in visiting the flocks 2 to 4 times a lactation (monthly or bimonthly) at only one of the two daily milkings, the purpose being to record 2 to 3 test-day per ewe and per lactation (Barillet, 1997) to implement a within-flock ranking of the ewes. In Spain, there is no description of the practice of D milk recording. In both cases, the purpose and valorization of such data is similar : in France as in Spain, D method is applied only to commercial flocks of breeders of the base population for within-flock breeding purposes (in contrast with A recording kept for the flocks of the open nucleus of the breeding schemes). In France, it concerns flocks belonging to the part of the population out of the nucleus flocks (44 % of the whole population including 5 breeds) whereas in Spain, it is dedicated to a foreign breed (Assaf) not included in a purebred breeding scheme.
- Regarding the importance of sheep dairying, two groups of countries may be described: the countries which have a large population (Mediterranean countries) and those with a smaller one, less than 40,000 ewes (Central and Northern Europe). In the Mediterranean countries, except in France where the impact of milk recording is high (up to 66 % ewes recorded when accounting both for A and D recordings), the percentage of recorded ewes is usually not higher than 8 % of the whole population. This situation emphasizes the difficulty to implement milk recording in sheep because fixed costs are high compared to cattle. Nevertheless, 2 countries have substantially increased the number of recorded ewes for the last 4 years : Italy (462,000 in 2002 vs 331,000 ewes in 1997, representing an increase of 40 % in 4 years) and Spain (243,000 in 2002 vs 141,000 ewes in 1997, representing an increase of 70 % in 4 years, basically due to implementation of D method) . The situation of the other countries is quite stable compared to the previous surveys (Astruc and Barillet, 2000; Barillet and Astruc, 1998). In Central and Northern Europe (Czech Republic, Denmark, England, Germany, Slovenia, Switzerland), milk recording is carried out in small flocks and represents few recorded ewes. Slovak Republic represents an intermediate situation with a large population (211,000 ewes on the whole, more than 14,000 recorded) of local breeds as Tsigai & Valachian.
- Among the breeds whose total size of population is up to 10,000 ewes (total size of the population), the following ones have at least 10 % recorded ewes : Assaf and Awassi (Israel), Basco-Béarnaise (France), Comisana (Italy), Corse (France), Frizarta (Greece), Karranzana (Spain), Lacaune (France), Langhe (Italy), Latxa -blond and black face- (Spain), Manech -red and black face- (France), Mountains of Ipiros (Greece), Pinzirita (Italy), Serres (Greece), Valle del Belice (Italy). Five breeds have a percentage of recorded ewes smaller than 10 %, while the number of recorded ewes is up to 10,000 : Churra (Spain) with 31,000 recorded ewes, Karagouniki (Greece) with 18,000 recording ewes, Lesvos (Greece) with 11,000 recording ewes, Manchega (Spain) with 51,000 recorded ewes and Sarda (Italy) with 217,000 recorded ewes. Let us mention that only two breeds are up to 100,000 recorded ewes: Sarda (Italy) and Lacaune (France), the Comisana breed (Italy) having decreased during the two past years down to 100,000 recorded ewes. Sarda is the first breed according to the number of recording ewes in official milk recording (217,000 ewes), while the Lacaune breed is the more extensively recorded breed when accounting both for official (A) and D recording (741,000 ewes).
- Although dairy sheep industry is usually based on local breeds raised in their native area and specific breeding conditions, several breeds are bred and recorded in several countries : Assaf (Israel, Spain) and Awassi (Israel, Macedonia), East Friesian (Czech Republic, England, Germany, Italy, Switzerland), Lacaune (France, Slovak Republic, Switzerland). If the presence of East Friesian in several countries is well known since a long time, the use of Lacaune and Assaf breeds is more recent and reaches large figures, especially in Spain (Ugarte et al, 2000).
Simplification of the official milk recording (for milk yield)
As initiated and promoted by ICAR as soon as the beginning of the works of the group, the standard A4 method continues to be progressively replaced by two simplified designs for milk yield (AT or AC) approved in ICAR regulations for sheep (ICAR, 1992) (Table 4).
AT method (alternating a monthly test on a single daily milking) has been used in Czech Republic, Germany, Italy and Spain. AC method (correcting monthly test of a single daily milking for evening/morning differences by using the total volume of milk produced by the whole flock for the two daily milkings) has been implemented in France, Israel, Italy (Sarda breed), Slovak Republic and Spain. AT and AC methods have thus now been implemented in 7 countries. The use of simplified methods, which has been a main term of reference for the last decade, should be applied in all countries, especially for the large populations, in order to increase the impact of milk recording. The case of Italy may be highlighted, where the adoption of simplified methods (AC in Sarda, AT in other breeds) has allowed a significant increase of milk recording. Basically, simplified methods have been well spread for the last 7 years (remember that in 1988, France and Switzerland were the only countries using simplified methods). On the whole, simplified methods represents 90 % over all the 1,035,000 recorded ewes of the survey (respectively 60 and 30 % for AC and AT method).
E method is practiced only in Germany on 108 ewes, representing 6% of the recorded ewes in this country.
Definition of milk traits
Classical husbandry systems in dairy sheep include a suckling period (or a combined suckling plus milking period) of at least one month (25 to 75 days according to the breed) before the milking only period. Milking from lambing has been described only in Czech Republic, England, Germany and Israel, for the East Friesian, Awassi and Assaf breeds. Except in these particular systems for which total milk yield is calculated in agreement with the husbandry system, ICAR regulations recommend to calculate milk yield at the milking only period (ICAR, 1992) : from a genetic point of view, milk of suckled ewes and milk of milked ewes don’t represent exactly the same trait. In addition, the estimation of the milk produced during the suckling period based on the first test-day (after weaning) is few accurate. Despite this recommendation, 3 countries continue to compute and publish the two traits and sometimes use as selection criteria the total milk yield instead of the milk yield at the milking only period (Table 4). Moreover the situation does not evolve over the years in spite of the ICAR guidelines.
Milk yield calculated with or without a reference length for the lactation is another difference between countries: 9 countries calculate a production of reference with a reference length ranging from 90 to 305 days.
Conversely to cattle, because of the heterogeneous breeding systems, types of calculation, number of flocks involved in, any classification of the breeds according to their supposed average milk yield level (Table 5) should not be reliable enough, as already pointed out by Barillet (1997). Under these conditions, the table 5 must be interpreted only as an illustration of these various modalities. Nevertheless, as every country in which the breeding system includes a suckling period computes milk yield during the milking only period, we propose to collect only this calculation for the next survey.
Optional dispositions: milk composition, somatic cell count (SCC) and other traits
In ICAR dairy sheep guidelines, the recording of milk quality (chemical as well as hygienic) is optional, mainly because of its cost. Consequently, it is recommended to implement these optional recordings only when the number of ewes recorded on milk yield is sufficient enough. Anyway, in 2001, 10 countries have practiced this type of recording (Table 6). The milk analysis concern fat and protein content (always), SCC (often), lactose (sometimes). For many years, milk quality has been recorded in countries of Central and Northern Europe. On the other hand, in the countries with large population involved in breeding schemes, until recent years, only France and Spain have recorded milk quality. Now, Cyprus and Italy have set up such a recording, in order to include the corresponding traits in the selection criteria. The recording method used is generally the same than for milk yield recording (AT, AC, A4). France has conceived in the eighties a specific design of sampling in the framework of the AC method : it consists in a part-lactation sampling only at the morning milking (2 to 4 samplings in the middle of the lactation, when the test-days are the most representative of the annual trait from a genetic point of view (Barillet, 1985)). This design is reliable for EBVs, but it needs cautious use for management purposes. This design (part lactation sampling in AC method) is also being used in Italy for the Sarda breed (Sanna et al. 1998).
The increasing economic importance of SCC (animal health, quality of milk) is a positive factor of the development of SCC recording. In some countries, high somatic cell counts in milk affects the price of the milk. Moreover, the European Union regulation concerning sheep and goat milk (EU Directive 92/46) should be applied within a few years. In this context, an European research project (FAIR project co-ordinated by X. Berthelot from France) including 3 ICAR members (France, Italy, Spain) has just ended, whose main objective was to attempt to reduce somatic cell counts in small ruminants and thereby improve both animal health and the quality of milk for processing into typical cheese (Berthelot, 1995). One important topic of the project was the harmonization of the analytical methods for SCC. Olivier Leray, chairman of the ICAR Working Group on Milk Testing Laboratories, was responsible of this topic, permitting thereby a close co-operation with his Working Group. In France, in a first step, a study was carried out to verify that the part-lactation sampling conceived for milk composition was available for SCC (Barillet et al., 2001). Then, a extensive recording of SCC has been implemented in the French milk recording since 1999 and first EBVs for SCC have been computed in 2002 (Rupp et al., 2002).
Recording of non-milking traits is described in the table 7. Reproduction (at least lambings) is always collected in the countries which answered the questionnaire. But only Greece (prolificacy) and Israel (prolificacy, age at first lambing, open days) includes it as a selection criteria. In some countries, the lambs are weighted at birth and/or weaning (Greece, Cyprus, Republic of Macedonia, Czech Republic, Germany). More and more members are interested in udder morphology related to milking ability, mainly at an experimental level. Udder scores are carried out in Cyprus, France, Germany, Italy, Spain and Switzerland. Some countries as France, Spain and Italy aim at including the scores in the selection criteria.
Finally, molecular genetics has an increasing development, with the pedigree verification based on microsatellite markers (France, Italy, Spain) and through PrP genotyping. As susceptibility to scrapie depends on the PrP gene, its knowledge is necessary (Cyprus, France, Germany, Spain, Italy) to select resistant animals. let’s notice that Israel works on FecB (Boorola) gene. A program of QTLs detection is currently running in France, Italy (Sardinia), Spain and United Kingdom, and an European research project (Barillet, 1999) called “genesheepsafety” started in 2001 on this topics.
Breeding schemes, objective and selection criteria
One objective of the questionnaire was to evaluate in which way milk recording has been connected with a breeding scheme.
According to the survey (Table 8), breeding schemes including progeny test have been implemented in a few breeds. Indeed, young rams (born from assortative matings) are progeny tested by AI in 3 countries : Spain with Latxa and Carranzana (100 rams), Manchega (100 rams), Churra (40 rams) ; Italy with Sarda (50 rams) ; France with Lacaune (470 rams), Manech & Basco-Béarnaise (190 rams), Corsica (30 rams). It emphasizes the technical and financial difficulty to implement an on-farm breeding scheme and also the necessity to adapt the selection tools to the dairy sheep (simplification of the tools, concentration of the tools in an open nucleus of flocks able to provide the AI or natural mating rams needed both for the breeders in official recording (nucleus) and for the commercial flocks.
AI is used only in Mediterranean countries : as a main tool of selection for the breeding schemes (France, Italy, Spain) or as a reproduction method (Cyprus, Greece, Israel). The sum of AI in these 6 countries reaches 560,000. The breeds are Assaf & Awassi (2,000), Lacaune (135,000 in the nucleus flocks in A recording, 265,000 out of the nucleus in commercial flocks using D recording), Manech & Basco-Béarnaise (53,300 in the nucleus flocks, 17,400 out of the nucleus), Corsica (5,200), Sarda (18,800), Latxa & Carranzana (25,000), Manchega (22,400) and Churra (10,700). In most cases, AI is carried out using fresh semen and induced oestrus, except in Churra breed where 85 % of the AI are performed with frozen semen.
Regarding objectives and selection criteria, the table 9 suggests two different situations. On the one hand, countries with small recorded populations (Germany, Macedonia, Slovak Republic, Slovenia). The selection criteria includes milk yield and milk composition. On the other hand, countries or breeds with an on-farm breeding scheme. In these populations, milk composition is more and more added to milk yield in the selection criteria (France, Spain). Cyprus includes growth rate, and Israel takes into account prolificacy.
BLUP applied to an Animal Model is more and more widely applied to estimate EBVs.
Main activities of the working group during the last two years
Updating the ICAR Guidelines of sheep milk recording
- Formal revision of the ICAR rules, standards and guidelines for milk recording in sheep, in accordance with the new statuses of ICAR.
- Introduction of more substantive changes in the guidelines, particularly new methods of sheep milk recording (method D and E) agreed in Rotorua. Method D has been introduced in the guidelines in autumn 2001. Concerning the E method (record of designated ewes actually suckling by their lambs but milked only the day of the test in order to estimate a lactation), the Working Group have asked to the German member (Franz-Joseph Romberg) a precise description of the actual practice of the E method (used in Germany only), in order to better fit the updating of the guidelines. This description is planned to be discussed at the meeting of the WG in Interlaken.
- A description of D and E methods have been published in the “ICAR Newsletter” (2001/No. 2).
Co-operation with the relevant Sub-Committees and Working Groups of ICAR
- Sub-Committee Recording Devices: adapting the rules of small ruminants (and especially sheep) regarding the design, construction and performance of meters and jars, and the tests of provisional approval for milk meters for small ruminants, each paragraph of the documents being divided into sub-paragraphs regarding each species. This work has been achieved in co-operation with the Working Group, Pierre Billon and Michel Blanchard, members of the SC Recording Devices.
- Milk Testing Laboratories Working Group (MTLWG) : The European research program on somatic cell count (SCC) of small ruminants ended in 2001. Olivier Leray is a partner of this project which has provided sound results regarding harmonization of SCC analysis methods for sheep or goat milk. We also have to stress that small ruminants and particularly sheep are more and more involved in the works of the MLT WG (standardization of reference methods for fat and protein in sheep and goat milk, proposal for a small ruminants reference laboratory network).
Contacts with non-ICAR organizations
- Cooperation with CIHEAM : on the one hand with the FAO-CIHEAM sub-network on animal resources in sheep and goats managed by Dunixi Gabina, on the other hand by teaching at the superior course of animal production organized by the IAMZ-CIHEAM in Zaragoza (Spain).
Since the approval of the ICAR guidelines for milk recording in sheep in 1992, the Working Group has carried out five surveys on milk recording in sheep, including each time other topics related to the terms of reference. The following points may be pointed out. As 10 years ago the dominant recording design was A4 method, to-day, simplification of milk recording (AT or AC method) represent 90 % of the recorded ewes. This simplification has been a efficient way to increase milk recording, particularly in Mediterranean countries with large population of dairy sheep (Italy, Spain). The record of milk composition and somatic cell count, which is optional in the guidelines has been increasingly implemented, at least at an experimental level. However, milk recording is not always sufficient to manage an efficient breeding scheme for the whole population (recorded and unrecorded flocks) and few breeds are involved in actual on-farm breeding schemes using AI rams. In this context, the main purpose of the members of the Working Group remains both to improve and simplify genetic tools suitable to dairy sheep, in the aim to promote the starting and/or development of breeding schemes based on on-farm milk recording combined with an accurate evaluation of the animals and the use of AI.
For the second time, we have attempted to publish average milk yield production from each country or breed. The great diversity in lactation calculation, sometimes combined with the non application of ICAR regulations (which recommend to compute milk yield at the milking period only, if ewes are being milked after a suckling period) prevents from proposing any classification of the breeds. Indeed, under these conditions, the supposed average phenotypic level for milk yield is not reliable enough.
Finally the Working Group, by the way of some of its members, stimulate and participate to research dealing with new technologies as molecular genetics combined with quantitative genetics to face new challenge related to functional traits or animal health for instance, as attested by the case of the PrP gene for selecting resistant animals to scrapie.
We thank ICAR and non-ICAR member countries, which have sent back answers to the questionnaire.
These countries are listed in the table 1.
Astruc J.M., Barillet F., 2000. Report of the ICAR Working Group on milk recording of sheep. Proc. 32nd Biennial Session of ICAR, Bled, Slovenia, 14-19 May 2000, EAAP Publication N° 98, Wageningen Pers, 289-306.
Barillet, F. 1985. Amélioration génétique de la composition du lait des brebis : l’exemple de la race Lacaune. PhD thesis, INA Paris-Grignon, Paris, 144 pp.
Barillet F., 1997. Genetics of milk production, in « The Genetics of Sheep », CAB International, editors I. Piper and A. Ruvinsky, chap 2, 535-560.
Barillet F., Astruc J.M., 1998. Report of the ICAR Working Group on milk recording of sheep: Survey of milk recording, use of AI and progeny test, pedigree information and supervisory systems, and on-farm computerisation of data collection in ICAR member countries. Proc. 31st biennial Session of ICAR, Rotorua, New Zealand, 18-23 January 1998, EAAP Publication N° 91, Wageningen Pers, 327-343.
Barillet F., 1999. Proposal QLRT-1999-30656 : Using genetics to improve the quality and safety of sheep products. 5th European Framework Programme.
Barillet F., Rupp R., Mignon S., Astruc J.M., Jacquin M., 2001. Genetic analysis for mastitis resistance and milk somatic cell score in French lacaune dairy sheep. Genet. Sel. Evol. 33 : 397-415.
Berthelot X., 1995. Projet du contrat FAIR N0 950881 (1996-2001) intitulé « Stratégies de contrôle en ferme des comptages de cellules somatiques du lait de brebis et de chèvre ».
ICAR, 1992. International Regulations for milk recording in Sheep. Institut de l’Elevage, Paris, 15 pp + appendix.
Rupp R., Boichard D., Barbat A., Astruc J.M., Lagriffoul G., Barillet F., 2002. Selection for mastitis resistance in French dairy sheep. Proc 7th WCGALP (to be published).
Sanna S.R., Carta A., Casu S., 1998. Simplifying schemes for recording fat and protein contents in Sarda dairy sheep. Proc. 31st biennial Session of ICAR, Rotorua, New Zealand, 18-23 January, EAAP Publication N° 91, Wageningen Pers, 155-160.
Ugarte E., Ruiz R., Gabina D., Beltran de Heredia I., 2000. Impact of high-yielding foreign breeds on the Spanish dairy sheep industry. Livest. Prod. Sci. 71 (1) 3-10.