RIASSUNTO -Effetto delloKEY WORDS: heat tolerance, temperature-humidity index (THI), dairy sheep.INTRODUCTION -European Mediterranean countries are characterized by exposure to considerable heat between three and six months annually. High ambient temperature, solar radiation, wind speed and relative humidity, cause the effective temperature of the environment to be above the thermo-neutral zone of the animals (5 to 25ºC; McDowell, 1972) and therefore heat stress occurs (Bianca, 1962). Heat stress is one of the limiting factors in dairy production in hot climates (Johnson et al., 1962) and is hard to account for by management in the extensive grazing-based farming system of Mediterranean dairy sheep where animals are rarely kept indoors. The interest of our study was to investigate if in the Mediterranean area heat stress has an effect on dairy sheep performance. Some studies (Ames et al., 1971;Sevi et al., 2001) on sheep heat stress investigated changes in rectal temperatures, respiration rates, volumes of air inhaled and other physiological functions. Unfortunately, such measurements are costly and not feasible on a large scale in practical farming circumstances, which leads to insufficient data quantity, especially for genetic studies. In the present paper the methodology of Ravagnolo et al. (2000) based on using weather station data for Holstein cattle was applied to Valle del Belice dairy sheep. The animals were investigated with the following aims: to establish the relationship between production and weather conditions using information from a weather station, and to estimate the additive genetic variances of milk production traits and heat tolerance, and therefore to investigate the possibility of future selection for increased heat tolerance.

Test day models were used to estimate the lactation curves for Valle del Belice ewes and to study the main environmental effects on milk yield and on percentage of fat and protein. Environmental effects were treated as fixed. A random effect was associated with each lactation to evaluate the mean correlation among all test day records of an individual ewe. Lactation curves were constructed by adding solutions for classes of either days in milk nested within parity or days in milk nested within season of lambing to appropriate general means. Parity primarily affected the lactation curve for milk yield, which was lower and flatter for first lambing ewes; effects on fat and protein were smaller. Season of lambing affected all traits. Seasonal productivity had the greatest effect on milk composition, resulting in an imbalance between fat and protein percentages. Flock and feed supplementation affected only the lactation curve for milk yield. The lactation curve of Valle del Belice ewes stood at a relatively high level. However, the presence of notable, perturbative effects (environmental and random variation) on milk yield and composition suggests that management is unable to meet the requirements of ewes consistently.

The physicochemical characteristics and sensory traits of Cinisara bresaola were investigated, to explore a new commercial opportunity for autochthonous dairy cattle farms. Semimembranosus, Semitendinosus and Biceps brachii muscles, from adult cows (AC) and grazing (GB) or housed (HB) young bulls of Cinisara breed, were processed to made bresaola. Differences due to animal category and muscle type were observed. Bresaola from AC was richer in fat and volatile organic compounds. The bresaola from Semitendinosus showed higher colorimetric parameters, fat and, when from grazing animals, Warner-Bratzler shear force than those made from other muscles. In general, all bresaola were well appreciated. The principal component analysis performed using selected physicochemical and sensory traits was able to discriminate bresaola produced from different animal categories, effect of muscle type was relevant only for AC. These results evidenced the possibility to obtain bresaola from the meat of different animal categories, comparable for sensory properties and appreciable by consumers.

The aim of this work was to sequence the exons of β-defensin 1 and 2 genes (SBD1 and SBD2) in Valle del Belice dairy sheep in order to identify polymorphisms. The study was conducted on 60 samples from three flocks. Six SNPs were identified: two in SBD1 and four in SBD2. Both genes consist of two exons and one intron. In SBD1 gene, SNPs were found only in the exon 2, whereas in SBD2, SNPs were detected in both exons. In both genes, SNPs were located in the coding regions and in the 3'-UTR. The SNP in SBD2 located at position 1659 determined a change in the protein sequence. Further studies will be necessary to investigate if the amino acid change modifies the biological function of the protein and the association with SCC, in order to use this information in a breeding program for mastitis resistance in Valle del Belice sheep

The objective of this paper was to investigate the prion protein (PrP) genotype and haplotype frequencies in three Sicilian dairy sheep populations. The three populations were: (1) 1096 Valle del Belice animals, (2) 1143 Comisana animals, and (3) 1771 individuals from 5 flocks with scrapie outbreaks, in which the animals were crossbreds derived from indigenous Sicilian dairy breeds. PrP genotypes are described for the three codons 136 (Alanine or Valine; A, V), 154 (Histidine or Arginine; H, R), and 171 (Glutamine, Arginine or Histidine; Q, R, H) which represent polymorphisms known to be linked with scrapie susceptibility. The Valle del Belice haplotype frequencies were 32.3% ARR, 6.5% AHQ, 1.0% ARH, 58.8% ARQ, and 1.4% VRQ. The Comisana frequencies were 39.4% ARR, 2.9% AHQ, 2.9% ARH, 50.9% ARQ, and 3.9% VRQ. In the flocks with scrapie outbreaks the frequencies were 32.8% ARR, 2.4% AHQ, 1.7% ARH, 59.1% ARQ, and 3.9% VRQ. In all three populations ARQ and ARR were the most frequent haplotypes. Multiple generations of strong selection will be needed to fixate the most resistant ARR haplotype