Abstract: The objective of this study was to investigate the growth- and breed-related changes of muscle fiber characteristics in cattle and their importance to meat quality Four cattle breeds with different growth impetus and muscularity were reared and slaughtered under experimental conditions German Angus as a beef type, Galloway as a hardy type, Holstein Friesian as a dairy type, and double-muscled Belgian Blue as an extreme type for muscle growth were used Between 5 and 17 bulls of each breed were slaughtered at 0, 2, 4, 6, 12, 18, and 24 mo of age Muscle fiber traits were determined and classified by computerized image analysis, and several measures of meat quality were also determined, including shear force value, meat color, and im fat content The postnatal growth of semitendinosus muscle in cattle was characterized by a nearly 10-fold increase of muscle fiber area from birth to 24 mo of age In the first few months after birth, a transformation of type IIA fibers into IIB fibers was found, whereas type I fibers were nearly unaffected by age The apparent total muscle fiber number of semitendinosus muscle did not increase during postnatal life These results confirm that the fiber number is determined in embryonic development Throughout the study, the double-muscled Belgian Blue (BBDM) bulls had almost twice the fiber number of the other breeds, emphasizing a more extensive hyperplasia of muscle fibers during embryonic development in BBDM compared with the other three breeds The apparent number of type I fibers was, however, not affected by breed, which suggests that the additional fibers found in BBDM postnatally were type IIB and IIA fibers We did not find significant differences in muscle fiber total number, muscle fiber type frequencies, or meat quality characteristics among breeds, with the exception of BBDM Having pooled the four breeds, paler meat was related to a higher frequency of type IIB fibers, a lower area of type IIA and type I fiber, and a higher total muscle fiber number These findings based on data of double muscling give us some hints for biological causes for the variation of meat quality Further investigation, in particular within each breed, is necessary to identify the superior fiber traits for bovine meat production

Abstract: A set of eleven pig breeds originating from six European countries, and including a small sample of wild pigs, was chosen for this study of genetic diversity. Diversity was evaluated on the basis of 18 microsatellite markers typed over a total of 483 DNA samples collected. Average breed heterozygosity varied from 0.35 to 0.60. Genotypic frequencies generally agreed with Hardy-Weinberg expectations, apart from the German Landrace and Schwabisch-Hallisches breeds, which showed significantly reduced heterozygosity. Breed differentiation was significant as shown by the high among-breed fixation index (overall FST = 0.27), and confirmed by the clustering based on the genetic distances between individuals, which grouped essentially all individuals in 11 clusters corresponding to the 11 breeds. The genetic distances between breeds were first used to construct phylogenetic trees. The trees indicated that a genetic drift model might explain the divergence of the two German breeds, but no reliable phylogeny could be inferred among the remaining breeds. The same distances were also used to measure the global diversity of the set of breeds considered, and to evaluate the marginal loss of diversity attached to each breed. In that respect, the French Basque breed appeared to be the most "unique" in the set considered. This study, which remains to be extended to a larger set of European breeds, indicates that using genetic distances between breeds of farm animals in a classical taxonomic approach may not give clear resolution, but points to their usefulness in a prospective evaluation of diversity.

Abstract: A set of eleven pig breeds originating from six European countries, and including a small sample of wild pigs, was chosen for this study of genetic diversity. Diversity was evaluated on the basis of 18 microsatellite markers typed over a total of 483 DNA samples collected. Average breed heterozygosity varied from 0.35 to 0.60. Genotypic frequencies generally agreed with Hardy-Weinberg expectations, apart from the German Landrace and Schwäbisch-Hällisches breeds, which showed significantly reduced heterozygosity. Breed differentiation was significant as shown by the high among-breed fixation index (overall F(ST)= 0.27), and confirmed by the clustering based on the genetic distances between individuals, which grouped essentially all individuals in 11 clusters corresponding to the 11 breeds. The genetic distances between breeds were first used to construct phylogenetic trees. The trees indicated that a genetic drift model might explain the divergence of the two German breeds, but no reliable phylogeny could be inferred among the remaining breeds. The same distances were also used to measure the global diversity of the set of breeds considered, and to evaluate the marginal loss of diversity attached to each breed. In that respect, the French Basque breed appeared to be the most "unique" in the set considered. This study, which remains to be extended to a larger set of European breeds, indicates that using genetic distances between breeds of farm animals in a classical taxonomic approach may not give clear resolution, but points to their usefulness in a prospective evaluation of diversity.

Abstract: Genetic relationships among six populations of Merino sheep were investigated using microsatellites. The history of the six populations is relatively well documented, with all being derived from the Spanish Merino breed within the last 400 years. Genetic variation was highest amongst the Spanish and Portuguese populations, although the preservation of genetic diversity within the other populations was high. By a variety of different statistical tests the French Mutton, German Mutton and New Zealand Merino populations could be differentiated from each other and the Iberian Merinos, indicating that microsatellites are able to track relatively recent changes in the population structure of sheep breeds. The dendrograms constructed on the basis of microsatellite allelic frequencies showed that populations that have shared selection criteria (meat vs. wool) tend to cluster together.

Abstract: This paper documents the breeding strategy of the New Zealand Radiata Pine Breeding Co-operative (NZRPBC) following a revision in 1997 to 1999 This co-operative serves 15 members in New Zealand and south-eastern Australia, and provides improved genetic material used for planting throughout New Zealand and in parts of Australia In the revised strategy, emphasis on recurrent selection for general combining ability (GCA), a 2-superline structure, main population and breeds are maintained A non-regionalised breeding programme, and a final selection around age eight years are also maintained A new Structural Timber breed is to be formed, along with a Clear Cuttings breed (with modified emphases compared to the long-standing Long Internode breed) The Growth and Form breed will be expanded, recombining new superior parent clones The existing Dothistroma-resistant breed will also be progressed, while the existing Long Internode and High Wood Density breeds will be used as sources of selections Good parents not selected for the breeds will be used in the main population A Guadalupe breeding population is also to be established The combined populations are to have a census number near 550 and a target status number of 400 The role of the breeds is to get optimum genetic gain while delaying the build-up of inbreeding, and to be the main source of new selections for seed orchards The main population will serve as a reservoir of genetic diversity, as a source of candidates for existing and future breeds, and as a form of genetic insurance' Candidates within breeds will be crossed in disconnected factorials and tested as seedlings or as clones within families Candidates within the main and Guadalupe population will be tested as seedlings The previous full review of the New Zealand breeding strategy for radiata pine was in 1986 The strategy was revised because of subsequent developments that impacted on breeding, including: new information and new tested parents; adopting a collaborative government-industry approach to breeding; advances in breeding strategy, forest genetics and propagation techniques; and changes in emphases and practices in the forestry sector The 1986 strategy had several key results, namely an emphasis on recurrent selection for general combining ability, a 2-superline breeding population with relatedness kept within superlines, stratifying the breeding population to an unspecialised main population and specialised breeds (with some overlap), a single breeding programme for all New Zealand, and separate crossing for recombination and for estimation of GCA

Abstract: Objective—To determine which dog breeds are at low and high risk for developing diabetes mellitus (DM). Design—Cohort study. Animals—Hospital population of 221 dogs with DM and 42,882 dogs without DM during 5.5 years. Procedure—165 breeds (including a mixed-breed category) were represented in the hospital population. Breed-specific expected numbers of dogs with DM were calculated by multiplying the proportion of all dogs admitted to the hospital that were determined to have DM during the study period by the breed-specific totals during the study period. Breeds or breed groups evaluated in the analysis (n = 20) were restricted to those that had a combined observed and expected count > 5 to document breeds at low and high risk for developing DM. Proportionate changes in the risk of developing DM by breed were calculated and presented using exact odds ratios, 95% confidence intervals, and P values. Mixed-breed dogs were chosen as the reference breed. Results—Samoyeds, Miniature Schnauzers, Miniature Poodles,...

Abstract: Mortality rate of young rabbits is of vital importance in commercial rabbit farming, since it determines the net income of the rabbitries. However, there is no definite proportion for mortality in young rabbits, since it may be less than 10% in one situation in a given breed and reaches 100% in other situations, in the same breed. This may be due to susceptibility of the genotype to diseases and to the numerous uncontrollable external environmental factors. The significant differences between breeds confirm that mortality can be genetically improved. Within the same breed, kit mortality during the suckling period decreases during the period between 4 and 12 months of doe production, then increases thereafter as age advances up to certain parity. The increase of pre-weaning mortality associates the increase in litter size at birth and reduction of remating interval period, although doe milk yield appeared to be the most important factor, in this respect. Thus, ali factors which may decrease doe rabbit milk yield (nutrition, management of the rabbitry, climatic conditions and doe diseases), increase pre-weaning mortality. lmprovement of nutrition (by using feed additives, antibiotics, probiotics, green fodder or natural sources) increases rabbit doe milk. Heat stress and diseases are the most important factors that affect post-weaning mortality. lt is worthy to note that young rabbits loss may be avoided to a large extent and health and vigour in the stock can be maintained by applying simple methods for cleanliness and in management. Prevention of diseases is also very important, because curative treatment is less successful in rabbits than in many other livestock classes.

Abstract: The genetic diversities and relationships of four Chinese indigenous pig breeds and one Australian commercial pig breed have been evaluated using 27 microsatellites recommended by the International Society of Animal Genetics (ISAG) and the Food and Agriculture Organization (FAO). The allele frequencies, effective numbers of alleles and the polymorphic information content have been calculated. Nei's standard genetic distances have been used to construct a UPGMA dendrogram, which has been evaluated by the Bootstrap test. The utility of microsatellites for evaluating genetic diversity of pigs is discussed.

Abstract: 1. At one colony of short-tailed shearwaters in Bass Strait, Australia, all birds breeding have been recorded individually each year for over 50 years. Among individuals known to be alive and to have bred before, 14% of each sex were not present at their breeding colony, on average, in any one year. 2. A further 15% of males and 13% of females (a significant difference), known to have bred before, were present but not associated with an egg in any one year. 3. Intermittent breeding was associated with pair bond breakdown and with a reduced ability to raise offspring, even when years of absence were allowed for. 4. The frequency of attendance, laying and successful rearing of progeny to fledging increased with age in the early years of breeding. However, this was followed by a decrease, except in the case of laying frequency, which continued to increase throughout life. 5. Our analysis indicated that intermittent breeding in short-tailed shearwaters did not result from individuals implementing trade-offs between the effort required for breeding success and their breeding life span. Rather, we suggest that individuals of higher quality are able to breed more frequently than others without any compensatory reduction in either their annual breeding success or their overall breeding life span.

Abstract: Prepubertal F1 heifers (n = 246; from crossbred dams bred to either Hereford [H], Limousin [L], or Piedmontese [P] sires) were fed 1.9% (LF) or 4.4% (HF) dietary fat from 254+/-4 d of age until they reached puberty or the breeding season started. Safflower seeds (37% oil with 79% linoleic acid) were the added fat source. Blood samples and backfat thickness measurements were obtained from 60 randomly selected heifers representing the sire breeds and diets studied. In addition, five H-sired heifers from both diets were serially bled at 28-d intervals. Total gain, ADG, body condition score, and backfat thickness were affected by sire breed (P 0.10) but tended (P = 0.08) to affect the percentage of heifers pubertal by the beginning of breeding (June 4). Sire breed effects on puberty age at beginning of breeding, percentage pubertal at the beginning of breeding, and puberty age during the entire study were all highly significant. The effect of the diet x sire breed interaction on percentage of heifers pubertal at beginning of breeding (P < 0.05) was 74.4 vs 76.3% in H-sired, 69.8 vs 60.5% in L-sired, and 76.2 vs 97.6% in P-sired heifers (LF vs HF, respectively). Number of AI services per pregnancy and final pregnancy percentage were not affected by diet or the diet x sire breed interaction. Diet affected progesterone (P < 0.05) and cholesterol (P < 0.001) concentrations, and sire breed tended to affect (P = 0.06) cholesterol concentrations. The effect of the diet x time on feed interaction on cholesterol concentrations was highly significant. There were no effects of diet or sample period on insulin or growth hormone concentrations in serially collected blood samples. We conclude that effects of supplemental dietary fat may be breed-dependent and hypothesize that a feeding period of approximately 60 d duration may be more appropriate than the 162 d used in this study.

Abstract: Forty-five Talaverana breed sucking lambs of both sexes were slaughtered at 10 and 12 kg live weight in order to study the effect of gender and slaughter weight on carcass, meat and fat traits. Carcass dressing proportions and fatness (by various measures) were higher in females and heavier lambs, which also showed better conformation. Lightness (L*) of the carcass fat was higher in males and heavier lambs. Females and heavier lambs also displayed a greater proportion of fat on dissection, primarily due to a higher percentage of subcutaneous fat tissue. Water-holding capacity was greater in males and in lower-weight lambs. Males presented higher total collagen and lower soluble collagen values than females. In general, a high percentage of short-chain (C12:0 and C14:0) fatty acids, as well as of palmitic acid (C16:0), was observed in the intramuscular fat of the longissimus dorsi muscle, corresponding with an exclusively milk diet.

Abstract: Significant breed differences in grazing, activity, social and other affiliative behaviours are known to exist in sheep. The roles of maternal and offspring genotype in determining the development of breed-specific behavioural differences in lambs were investigated using embryo-transfer. Two breeds of sheep (Suffolk and Scottish Blackface) were chosen as they differ markedly in social and affiliative behaviours. Sixty ewe-lamb pairs (15 each of the four combinations of ewe and lamb) were observed over the first 3 days after lambing, then when the lambs were aged between 2-5 months old and during the first 6 weeks after weaning. Lamb breed was the main factor affecting lamb activity at birth and play behaviour over the first postnatal days, with Blackface lambs being significantly more active than Suffolk lambs. Lamb sucking behaviour during this period, however, was significantly affected by ewe breed with a higher frequency of sucking interactions observed with Suffolk ewes. When out at grass the two breeds of ewe differed in their use of the field, with Blackface ewes using upland areas whilst Suffolk ewes were found almost exclusively in the lowland parts. Ewes also differed in their spatial relationship to their lamb, with Blackface ewes maintaining a closer relationship to their lamb than Suffolk ewes, regardless of lamb breed. Blackface ewes were also more active than Suffolk ewes and were more frequently observed grazing. The breed of their mother significantly influenced the behaviour of the lambs, and their spatial relationships to other sheep, both before and after weaning. Lambs with Blackface mothers were more active than lambs with Suffolk mothers and this difference persisted after weaning. Blackface-reared lambs also had a shorter nearest neighbour distance after weaning, aggregated into smaller subgroups and were significantly more likely to be in upland areas of the field, regardless of lamb breed, than lambs reared by Suffolk ewes. Maternal influence, therefore, plays an important role in shaping the behaviour of their offspring in sheep, although neonatal lamb activity is not affected by maternal behaviour.

Abstract: Information is presented on the frequency of the Msp I (-) allele in the third intron of the bovine growth hormone gene in a large number of cattle breeds. Consideration of the breed frequencies in relation to their geographic origin shows a low frequency for breeds originating in Northern Europe, moderate frequencies for breeds originating in Eastern Europe or the countries surrounding the Mediterranean basin, and very high frequencies for breeds originating in the Indian subcontinent. Consideration of breed frequencies in relation to breed type, shows low to moderate frequencies for the humpless breeds, high frequencies for the humped breeds. Various explanations for this distribution are discussed, among them the possibility that the Msp I (-) allele originated in the Bos indicus breeds of the Indian subcontinent, from which it diffused through the humpless Bos taurus breeds of Eastern Europe, the Mediterranean basin, eventually reaching Western, Northern Europe, Western Africa in low frequencies.

Abstract: We estimated the genetic relationships between the endangered German Pustertaler–Sprinzen cattle breed and the Pinzgauer, Vosges and Simmental breeds – decided upon after consultation of the available historical literature. Within-breed diversity of the four breeds was also assessed. Twenty microsatellite markers were amplified in 27–50 unrelated individuals from populations of each breed. Within-breed variation was estimated from average heterozygosity values and mean number of alleles. Breed relationships were evaluated by genetic distance and a neighbour-joining tree was calculated from these estimates. Bootstrap resampling of loci tested the robustness of the tree topology obtained. A tree was also constructed from distance matrices using individual animals as operational taxonomic units. From both the average heterozygosity values and mean number of alleles calculated, the Pustertaler breed appears to be no more genetically impoverished than the other breeds analysed. The breed tree showed an 85% support for the Pustertaler–Pinzgauer grouping, and this result is echoed in the genetic distance values and allele-sharing individual tree.

Abstract: Sire breed effects were studied in 1080 lambs born over three years to Merino ewes and 6–10 sires each of Merino, Poll Dorset, Border Leicester, Texel, Oxford Down, and Suffolk breeds. Ewes bearing crossbred lambs required more assistance at lambing than those with purebred Merino lambs. Poll Dorset cross lambs grew fastest and purebred Merinos slowest from tailing until they were 12 months old (P < 0.05). While purebred Merinos tended to have less carcass fat throughout the trial, differences between the other crossbreds changed with time. Texel and Poll Dorset cross carcasses generally had larger eye muscle size (P < 0.05) than other sire breeds. Carcasses were “blockier” for crossbreds, particularly Texel and Oxford Down, but weights of individual cuts were similar for all breeds. At 12 months of age, greasy fleece weights were heaviest (P < 0.05) in Border Leicester cross lambs (4.4 kg) and least in Suffolk crosses (3.1 kg). It is concluded that Merino cross lambs can produce 20‐kg carcasses ...

Abstract: Genetic parameters were estimated for 36-, 42-, 50-, 100- and 150-day weight in the South African Mutton Merino breed. The direct heritability estimates obtained were 0.270, 0.366, 0.278, 0.185 and 0.115 respectively. The maternal heritability estimates for the respective weights were 0.494, 0.249, 0.129, 0.091 and 0.080. The correlation between the animal effects (direct and maternal) varied between -1.000 for 36-day weight to -0.376 for 150-day weight. Very little selection progress was made over the period (1980-1999) in the breed. (South African Journal of Animal Science, 2000, 30(3): 172-177)

Abstract: 3866 sheep from 226 flocks of breeding associations and 1218 sheep from 15 independent sheep owners were tested for the presence of serum antibodies against Maedi-Visna and Border Disease viruses. The flocks were randomly selected based on the relative proportion and the geographical distribution of the 4 predominant Swiss sheep breeds (Braunkopfiges Fleischschaf, Schwarzbraunes Berg- und Juraschaf, Walliser Schwarznasenschaf, Weisses Alpenschaf). Additionally two smaller breeds were included in the study (Charollais Suisse, Milchschafe). Sera of all sheep older than 1 year were collected together with data characterizing host and management factors. The sera were tested using established ELISAs for detection of antibodies to Maedi-Visna and Bovine Virus Diarrhea/Border Disease viruses. ELISA results of Maedi-Visna serology were confirmed by immunoblotting. 9% of the sheep of breeding associations were antibody-positive for Maedi-Visna virus. The results of the different breeds varied between 0.4% and 36%. A multiple logistic regression procedure identified breed, age, airing in barns, herd size, pasturing on alps and way of keeping the animals during winter as associated factors with individual serostatus. The prevalence of antibodies to Border Disease was 20% in sheep of breeding associations and 65% in those of independent sheep owners.

Abstract: The improvement programme in Jamunapari goats was started with the active participation of farmers in two adopted villages and efforts have been made to characterise the performance of Jamunapari goats in their home tract in relation to production, reproduction performance and field conditions relating to socio-economic status of farmers. The phenotypic measurements are also described in the breed in its habitat. Jamunapari is a tall, white and large size milch goat breed of India and their numbers have been reducing over the years for various reasons. The description in relation to housing, feeding, management, growth parameters, milk yield, parasitic load, blood polymorphism and constraints in field conditions has been made in detail. Body weights at birth, three, six and nine months were 2.75 kg, 12.3 kg, 16 kg and 22 kg, respectively. Milk yield at 90 and 150 days was 102 and 145 litres, respectively. The peak breeding season of this goat in field conditions is in May-June and twining percentage is about 52 percent. The overall mortality in village conditions is about 3.7 percent and is mostly due to diarrhea and pneumonia. The mortality was 3.7 percent, 1.9 percent, 9.8 percent and 2.0 percent in 0–3, 3–6, and 6–12 months, and adult goats, respectively over the years. The native goat in its home tract is endangered for several reasons and utmost care is needed from all angles to save this germplasm.

Abstract: This paper documents the breeding strategy of the New Zealand Radiata Pine Breeding Co-operative (NZRPBC) following a revision in 1997 to 1999. This co-operative serves 15 members in New Zealand and south-eastern Australia, and provides improved genetic material used for planting throughout New Zealand and in parts of Australia. In the revised strategy, emphasis on recurrent selection for general combining ability (GCA), a 2-superline structure, main population and breeds are maintained. A non-regionalised breeding programme, and a final selection around age eight years are also maintained. A new Structural Timber breed is to be formed, along with a Clear Cuttings breed (with modified emphases compared to the long-standing Long Internode breed). The Growth and Form breed will be expanded, recombining new superior parent clones. The existing Dothistroma-resistant breed will also be progressed, while the existing Long Internode and High Wood Density breeds will be used as sources of selections. Good parents not selected for the breeds will be used in the main population. A Guadalupe breeding population is also to be established.

Abstract: Effects of Dorset, Finnsheep, Romanov, Texel, and Montadale breeds for performance as sires were estimated in the initial phase of a comprehensive evaluation of these breeds as contributors to sheep crossbreeding systems. Objectives were to evaluate the effects of ram breed, ewe breed, season of mating, and two-way interactions. Rams from the five breeds were single-sire-mated with ewes from two breed types to produce lambs over a 3-yr period. Ewes were assigned to one of three distinct 35-d mating seasons initiated each year in August, October, and December. A different sample of six rams per breed was used each year across all three seasons, and each ram was penned with ewes of both breeds. Traits evaluated and number of ewe records were conception rate and litter weaning weight per ewe exposed (n = 3,261) and number born, litter birth weight, average birth weight, number weaned, and litter weaning weight per ewe lambing (n = 2,751). Ram breed and ewe breed interacted (P < .01) for conception rate and litter weaning weight per ewe exposed, implicating mating preferences, particularly of Romanov rams. In mixed groups of ewes exposed to Romanov rams, conception rate was 12.7% lower and litter weight weaned was 8.4 kg lower in the ewe breed presumably less preferred for mating by the rams. On a per ewe exposed basis, Romanov-sired litters produced either the largest or the smallest values for litter weaning weight, depending on the breed of ewe. Effects of ram breed on number born and litter birth weight interacted (P < .05) with season of mating. The largest litters within each ram breed were associated with the October mating season. Montadale and Romanov rams sired larger and heavier litters from August matings than from December matings, whereas the opposite was true for Dorset-sired litters. Texel- and Finnsheep-sired litters were similar in size and weight from August and December matings. Breed of ram differences affected per ewe lambing productivity measurements (P < .01). Differences between ram breeds for ewe productivity were noted, with increased number born and improved survival of crossbred progeny to weaning for Romanov-sired litters. These results may have implications for using these ram breeds as sires in different crossbreeding systems. Structured mating systems or the creation of new composite populations involving these breeds could be used to match the resources, environment, and market of specific production situations.

Abstract: The objective of this study was to determine the effect of tropically adapted sire breeds on preweaning growth performance of F1 calves and on reproductive performance of their Angus dams. Angus (A) cows were bred in two consecutive years (1992 and 1993) by AI using semen from Brahman (B; Bos indicus; n = 10), Senepol (S; Bos taurus; n = 10), and Tuli (T; Sanga; n = 9) bulls. A total of 82 B x A, 85 S x A, and 91 T x A calves were born. The statistical model included the fixed effects of year, sire breed, calf sex, sire breed x calf sex, and cow parity and the random effect of sire within sire breed. Birth weight, weaning weight, 205-d adjusted weaning weight, ADG from birth to weaning, and hip height at weaning were greater (P .10) length of gestation, and sire breed did not affect the interval from calving to first observed estrus or pregnancy in Angus dams. These results demonstrate that preweaning growth performance of B x A calves was greater than that of either S x A or T x A calves. However, use of Brahman sires on Angus dams led to calving problems and tended to reduce the percentage of calves that survived until weaning. Thus, heavier weaning weights of B x A calves would be an advantage for cow-calf producers marketing calves, but heavier birth weights and calving difficulty attributed to Brahman sires would be a disadvantage.

Abstract: This paper presents a descriptive overview of milk somatic cell counts in the French dairy cattle breeds. Data originated from the national data base, with complete information since 1995. Cell count level varied according to breeds, and the milk was less concentrated in cells in low producing breeds (Abondance, Simmental Francaise) than in more high-yielding breeds (Prim’Holstein, Pie Rouge des Plaines). These differences across breeds were still observed for a given production level and, therefore, could not simply be explained by production . Within breed, the lowest producing cows had the highest cell count level. These cows were likely to be infected and their low production probably reflected the depressive effect of infections on milk production. Within breed, cell counts increased with parity. This illustrated the increase in incidence and persistency of intramammary infections with age. The cell counts evolution with days in milk showed a trend inverted to that of milk yield. Except in the beginning of the lactation, this trend likely resulted from a concentration effect due to the change in milk volume over the lactation, as the number of excreted cells was found to be stable after the first two months of lactation. Cell counts were higher in summer and lower in fall, whatever the lactation stage. They also varied among regions. On the other hand, cell count level was stable over time during the last five years and denoted the technical control ability of the farmers.