The aim of this work was to investigate the genetic structure of the casein gene cluster in 5 Italian goat breeds and to evaluate the haplotype variability within and among populations. A total of 430 goats from Vallesana, Roccaverano, Jonica, Garganica, and Maltese breeds were genotyped at α s1 -casein (CSN1S1), α s2 -casein, (CSN1S2), β-casein (CSN2), and κ-casein (CSN3) loci using several genomic techniques and milk protein analysis. Casein haplotype frequencies were estimated for each breed. Principal component analysis was carried out to highlight the relationship among breeds. Allele and haplotype distributions indicated considerable differences among breeds. The haplotype CSN1S1*F-CSN1S2*F-CSN3*D occurred in all breeds with frequencies >0.100 and was the most common haplotype in the Southern breeds. A high frequency of CSN1S1*0-CSN1S2*C-CSN3*A haplotype was found in Vallesana population (0.162). Principal component analysis clearly separated the Northern and Southern breeds by the first component. The variability of the caprine casein loci and variety of resulting haplotypes should be exploited in the future using specific breeding programs aiming to preserve biodiversity and to select goat genetic lines for specific protein production. (Key words: goat, casein, polymorphism, haplotype) Abbreviation key: AS-PCR = allele specific-PCR, CSN1S1 = α s1 -casein locus, CSN1S2 = α s2 -casein locus, CSN3 = κ-casein locus, CSN2 = β-casein locus, IEF = isoelectrofocusing, PCR-SSCP = PCR-single strand conformational polymorphism.

The objective of this study was to estimate the effects of different haplotypes of the casein genes on milk production traits in Italian dairy cattle. Traits of interest were yields of milk, fat, and protein, and percentages of fat and protein in milk. The data included 728 multiparous records from 347 Holsteins and 773 records from 298 Brown Swiss cows. Records were preadjusted for effects of age and parity, season of calving, and region, and expressed as deviations from herdmate averages. Twenty half-sib families were represented in each breed. Haplotype probabilities were estimated for each animal and phenotypes were regressed on these probabilities. Nine haplotypes were observed in Holsteins and 17 were identified among the Brown Swiss. For Holsteins, significant effects were observed for protein percentage, with some indication of an effect for fat percentage. For the Brown Swiss, effects of haplotypes were significant for milk yield and fat and protein percentages. Effects were strongest for protein percentage. Correlation coefficients of solutions across breeds tended to be strong and positive, indicating that the same haplotypes had similar estimated effects in the 2 breeds. Although the data were limited (<350 cows in each study), this latter result may suggest that genes in the casein complex itself are responsible for the effects observed, rather than loci that are physically linked on either side of the casein cluster.

Mammary involution and inflammation are known to negatively affect milk quality. A trial was carried out to elucidate the mechanism by which udder health status and lactational phase determine compositional modifications in ovine milk. A total of 60 individual milk samples was collected from a group of 20 pluriparous Sardinian ewes from mid to late lactation. Each sample was assessed for its chemical characteristics, quantitative distribution of casein fractions, lactodynamographic characteristics, and enzymatic activity. Udders were classed as healthy, doubtful, or infected on the basis of repeated somatic cell counts, and samples were grouped in 3 classes of days in milk. Results indicated that both udder inflammation and mammary involution can increase plasmin (PL) activity (15.6 vs. 18.4 U/mL in healthy vs. infected udders; 14.0 vs. 20.2 U/mL in phase 1 vs. 3), which is responsible for an evident protein breakdown in milk. Significant differences between groups were observed for several characteristics. With regard to udder heath status, casein index was lower in the infected vs. healthy udders (74.8 vs. 76.6%), and beta(tot)-casein showed a similar trend (43.9 vs. 46.6%). As a consequence of protein degradation, gamma-casein (5.78 vs. 2.82%) and proteolysis index (7.60 vs. 3.82) increased in the infected group with respect to the healthy group. Udder health status also affected milk technological traits. Udder inflammation resulted in longer clotting time (20.7 vs. 16.5 min for infected vs. healthy, respectively) and in poorer curd firmness (35.6 vs. 47.6 mm for infected vs. healthy, respectively). Frequency of samples reactive to rennet was 100, 93, and 67%, respectively, for healthy, doubtful, and infected groups. With regard to lactational phase, a decrease in alpha(s1)-casein (39.13 vs. 29.36%) and beta(1)-casein (23.41 vs. 19.36%) occurred during phase 1 vs. 3, whereas kappa + alpha(s2)-casein increased (12.30 vs. 21.56%, phase 1 vs. 3). Correlation coefficients confirmed the role of PL in protein degradation. It was concluded that PL activity was strongly affected by both lactational phase and udder health status and, in turn, could be an important agent enhancing milk quality detriment.

A protocol for the rapid and simultaneous genotyping of A, C, and 0 'CSN2 alleles in goat was developed by single strand conformational polymorphism polymerase chain reaction (SSCP-PCR) technique. Screening the CSN2 variability in 7 goat breeds reared in Italy validated the genotyping test. The SSCP-PCR technique was also suitable for monitoring CSN2 polymorphism. In particular, the discrimination between CSN2*A and CSN2*C is important because the 2 corresponding protein variants cannot be separated by standard typing techniques. The monitoring of CSN2 variability in the goat breeds indicates the predominance of the C allele. In most breeds, CSN2*C occurred with the highest frequency, except in Saanen where CSN2*A and CSN2*C showed similar frequencies. Variant CSN2*C occurred with a frequency of 0.68 (Camosciata), 0.70 (Jonica), 0.71 (Garganica), 0.82 (Maltese), 0.87 (Cilentana), and 0.97 (Orobica). The alignment among the mature CSN2 sequences of different species suggests that CSN2*A is the ancestral allele compared with CSN2*C. Interestingly, the CSN2*A goat variant showed higher frequencies in selected breeds (Saanen and Camosciata).

The milk protein genetic structure of the Reggiana dairy local cattle with remarkable milk quality properties was analysed and compared with the structure of Italian Friesian and Italian Brown cattle. A total of 1138 individual milk samples from the three breeds were typed by isoelectrofocusing. Polymorphism was found at the a s1 -casein (CSN1S1), b-casein (CSN2), j-casein (CSN3), and b-lactoglobulin (LGB) loci. High frequencies were observed for some casein alleles in Reggiana (CSN1S1*C, 25%; CSN2*B: 28%) with considerable differences to those observed in a survey carried out 30 years before. A great variation among breeds was observed for casein haplotype frequencies and high linkage disequilibrium was detected at the three polymorphic casein loci CSN1S1-CSN2-CSN3. The prevalent haplotypes were CA 2 B (23%; Reggiana), BA 2 A (48%; Italian Friesian) and BA 2 B (51%; Italian Brown). Higher G ST values between breeds were observed when haplotype frequencies were considered instead of gene frequencies. In the Reggiana cattle, the occurrence of two casein alleles at a rather high frequency (CSN1S1*C, CSN2*B) allowed to estimate the effects of rare casein haplotypes on milk traits. The CA 2 B haplotype was associated with a significantly higher milk protein and fat content and a significantly higher protein per cent was found also for the BA 1 B haplotype. ZusammenfassungDie genetische Struktur von Milchproteinpolymorphismen und ihre Effekte auf Milchproduktionsmerkmale in einer lokalen Milchrinderrasse Die genetische Struktur der Milchproteine der lokalen Rinderrasse Reggiana, die ü ber bemerkenswerte Eigenschaften der Milchqualität verfü gt, wurde analysiert und mit der genetischen Struktur der Rassen Italienische Holsteins und Italienisches Braunvieh verglichen. Es wurden hierbei 1.138 individuelle Milchproben der drei Rassen mit Hilfe der isoelektrischen Fokussierung typisiert. Es konnten Polymorphismen im a S1 -Kasein (CSN1S1), b-Kasein (CSN2), j-Kasein (CSN3) und b-Lactoglobulin (LGB) dargestellt werden. Bei einigen Kaseinallelen wurden bei der Rasse Reggiana hohe Allelfrequenzen beobachtet (CSN1S1*C, 25%; CSN2*B, 28%), mit erheblichen Unterschieden zu den Allelfrequenzen, die bei einer Untersuchung vor 30 Jahren beobachtet wurden. Eine große Variation zwischen den Rassen wurde fü r die Kasein-Haplotyp-Frequenzen beobachtet, und ein hohes Kopplungsungleichgewicht wurde an den drei polymorphen Kaseingenorten CSN1S1-CSN2-CSN3 festgestellt. Die häufigsten Haplotypen waren CA 2 B (23%; Reggiana), BA 2 B (48%; Italienische Holsteins) und BA 2 B (51%; Italienisches Braunvieh). Hö here G ST Werte wurden dann beobachtet, wenn die Haplotypfrequenzen an Stelle von Genfrequenzen verwendet werden. Bei der Rasse Reggiana erlaubte das Auftreten von zwei Kaseinallelen mit hohen Frequenzen (CSN1S1*C, CSN2*B) das Schätzen der Effekte von seltenen Kaseinhaplotypen auf Milchmerkmale. Der CA 2 B-Haplotyp war mit einem signifikant hö heren Protein-und Fettgehalt assoziiert und auch fü r den BA 2 B-Haplotyp konnte ein signifikant hö...