Breed and shearing effects on milk composition and rennet-induced coagulation properties in dairy ewes

Abstract

Shearing during late-pregnancy and mid-lactation has been proposed as improving welfare practices in dairy sheep. With this aim, and as a follow up of a previous experiment, milk composition and milk rennet-induced coagulation properties were assessed in 2 breeds of dairy ewes (Manchega, MN, n = 43; Lacaune, LC, n = 28) which were shorn at different moments of their production cycle: i) unshorn (CO), ii) shorn before breeding (SBB), or iii) shorn at d 100 of pregnancy (S100). Individual milk samples were collected at d 160 and 161 of lactation and composited for milk analyses and milk batches produced by breed and shearing treatment for assessing milk rennet-induced coagulation properties with an Optigraph laboratory instrument (rennet coagulation time, RCT; Curd firmness at 45 min, F45). Milk composition and cheese rennet-induced coagulation properties varied markedly by breed, the MN showing greater values than the LC ewes, but no differences in major milk components nor in rennet-induced coagulation properties were detected by effect of shearing in both breeds. Nevertheless, opposite differences by shearing treatment were detected in RCT, which was longer in MN (9 %) and shorter in LC (− 8 %), when S100 and CO treatments were compared. The obtained results showed marked differences in cheese extract and yield in favor to the richer MN milk, with economic consequences on milk price, whereas shearing moment only modified RCT, the sense of variation depending on the breed and not being associated to changes in milk composition; therefore, assessment of additional factors is required for in-depth understanding.