Italian local goat breeds: phenotypic variation of milk mineral and fatty acid composition and milk technological traits. Le razze italiane di capra: variazione fenotipica della composizione del profilo minerale, degli acidi grassi e delle caratteristiche tecnologiche del latte

Studies on goat milk have mainly focused on dairy cosmopolitan breeds and very limited information is available on local breeds. Generally, the cosmopolitan breeds received major attention by farmers and dairy industries for their greater milk yield than local breeds. However, the refuse of locals in favour of more productive breeds implies a gradual decrease in number of animals and may lead to the extinction of the local breed causing the genetic erosion of the species. Hence, preserving local breeds from extinction is a significant action that aims not only to maintain ancient local traditions but also to support local economies in marginal areas. Moreover, local breeds are well adapted to their original environment, showing a better resistance to disease; in addition, several studies found that local breeds yield milk with better milk composition than cosmopolitan breeds. The overall objectives of the present thesis were to assess the phenotypic variation of i) yield, chemical composition and somatic cell; ii) minerals composition iii) fatty acids composition; and iv) technological traits in milk of five Italian local goat breeds (Garganica, GA; Girgentana, GI; Jonica, JO; Maltese, MA; and Mediterranean Red, MR) and one cosmopolitan breed (Saanen, SA). The main source of variation were breed, lactation phase and parity order. The first study examined the phenotypic variation of milk yield and composition. From February to September (every 2-3 weeks) individual milk yield was recorded for 60 does, and a total of 840 individual milk samples were collected. Local breeds produced less milk than cosmopolitan breed; however, local milks were poorer in somatic cell score but richer in fat and lactose than SA breed. The variation in yield and milk quality traits through lactation followed the general pattern described for small ruminants. Milk yield peaked around the 4th week of lactation for all breeds; however, local breeds showed a greater persistency of lactation (until 23rd week of lactation) compared to Saanen breed (until 16th week of lactation). The better milk composition was observed in late lactation. The second and third contribute investigated the variation in milk mineral and fatty acids composition of the pervious goat breeds by investigating a subset of original dataset (n = 252; 7 does per breed). Breed affected P, Mg and Zn and C4:0, from C14:0 to C18:0, C16:1, desaturation index of C16:0 and atherogenic index; however, SA mineral profile was similar to that one of some local breeds, whereas its fatty acids profile was less healthy. Week of lactation highly affect major and trace milk minerals contents. Due to the concentration effect, the greatest content for almost all the minerals was found in late than early lactation. On the other hand, fatty acids were affected by feeding ratio adjusted according lactation phases; in detail, short and medium chain of fatty acids were greater in early than late lactation, and milk of late lactation was richer in n3, n6, conjugated of linoleic acid and unsaturated fatty acids. The fourth research examined the milk composition and coagulation properties of samples collected monthly from GA, GI, MA, MR and SA breeds between May and August (n = 178; 8-10 does per breed). Breed significant affected milk coagulation properties, protein and lactose percentage, and pH; whereas, month of lactation affected all the studied traits. Milk of local breeds were richer in protein that reflected in shorter time of coagulation and curding firming time than SA breed. Therefore, SA milk showed a curd firmness different only to GI breed. Rennet coagulation time and curd firmness decreased toward the end of lactation, observing significant difference between May and August, whereas curd- firming time differs between May and June-July.