In this study, milk-coagulation properties (MCP) were characterized in the Sarda sheep breed. Milk composition and MCP [rennet-coagulation time (RCT), curd-firming time [time to reach a curd firmness of 20mm (k20)], and curd firmness (a30), (a45), and (a60)] were obtained extending the lactodynamographic analysis from 30 to 60 min from a population of 1,121 ewes from 23 different farms. Managerial characteristics of farms and parity, individual daily milk yields and stage of lactation of ewes were recorded. Data were analyzed using a mixed-model procedure with fixed effects of days in milk, parity, daily milk yield, and flock size and the random effect of the flock/test day nested within flock size. Sampled farms were classified as small (600 ewes), often operated through hired workers. Daily milk yield was, on average, 1.58 ± 0.79 L/d and variability for this trait was very high. The average content of fat, protein, and casein was respectively 6.41, 5.39, and 4.20%. The class of flock size had a significant effect only on curd firmness, whereas days in milk affected RCT and k20. The flock test day, parity, and daily milk yield were important sources of variation for all MCP. The mean value of RCT (8.6 min) and the low occurrence of noncoagulating samples (0.44%) confirmed the excellent coagulation ability of sheep milk compared with cattle milk. A more rapid coagulation was observed in mid-lactating, primiparous, and high-yielding ewes. The k20 was usually reached in less than 2 min after gelation, with the most favorable values at mid lactation. The mean value of curd firmness 30 min after rennet addition (a30) was, on average, 50mm and decreased to 46 and 42 mm respectively after 45 (a45) and 60 min (a60). The decreasing value of curd-firmness traits was likely to be caused by curd syneresis and whey expulsion. The correlation between RCT and a30 was much lower than in dairy cows and about null for a45 and a60. This means that curd firmness in dairy ewes is almost independent of gelation time and this can provide specific information for this species. In conclusion, this study showed that milk from Sarda sheep is characterized by an earlier gelation, a faster increase in curd firmness with time, and greater curd firmness after 30 min compared with dairy cows. Furthermore, correlations between MCP in sheep are much lower than in bovines and some of the assumptions and interpretations related to cows cannot be applied to sheep.

The aim of this study was to test the modeling of curd-firming (CF) measures and to compare the sheep milk of 3 Alpine breeds supplemented with or without rumen-protected conjugated linoleic acid (rpCLA). Twenty-four ewes of the Brogna, Foza, and Lamon breeds were allotted to 6 pens (2 pens/breed) and fed a diet composed of corn grain, corn silage, dried sugar beet pulp, soybean meal, wheat bran, wheat straw, and a vitamin-mineral mixture. The rpCLA supplement (12 g/d per ewe plus 4 g/d for each lamb older than 30 d) was mixed into the diet of 1 pen per sheep breed (3 pens/treatment) to provide an average of 0.945 and 0.915 g/d per ewe of the cis-9,trans-11 C18:2 and trans-10,cis-12 C18:2 conjugated linoleic acid isomers, respectively. The trial started at 38 ± 23 d after parturition, and individual morning milk samples were collected on d 16, 23, 37, 44, and 59 of the trial. Milk samples were analyzed for composition, and duplicate samples were assessed for milk coagulation properties (MCP). A total of 180 CF measures for each sample (1 every 15s) were recorded. Model parameters were the rennet coagulation time, the asymptotic potential CF, the CF instant rate constant, the syneresis instant rate constant, the maximum CF achieved within 45 min (CFmax), and the time at achievement of CFmax. The data were analyzed using a hierarchical model that considered the fixed effects of breed, diet, lamb birth, and initial days in milk, which were tested on individual ewe (random) variance; the fixed effect of sampling day, which was tested on the within-ewe sample (random) variance; and the fixed effect of instrument or cuvette position (only for MCP), which was tested on the residual (replicates within samples) variance. The local Alpine sheep breeds displayed similar milk compositions, traditional MCP, and CF modeling parameters. Supplementation with rpCLA triggered changes in milk composition and worsened MCP (e.g., delayed rennet coagulation time, slower CF instant rate constant, and a doubling of syneresis instant rate constant), but did not influence potential CF. Overall, our results indicate that rpCLA supplementation reduced the actual maximum CF (CFmax) but did not modify the interval between rennet addition and CFmax or time to CFmax.

The aim of this research was to investigate how growth hormone (GH) cortisol and some haematochemical parameters could be modified by the stress caused by the stages of shearing in Sarda breed sheep. Five groups of 10 sheep each were formed. Group A, only separated from the flock; Group B, only tied; Group C, both tied and shorn (animals in these three groups were ewe lambs shorn for the first time); Group D, adult females both tied and shorn; and Group E, adult entire males both tied and shorn (animals in these two groups had been shorn previously). Five blood samples were taken from each animal: the day before treatment (first sample); at the start of the treatment (second sample); in the middle of shearing for Groups C, D and E, 10 min after separation in Group A and 10 min after tying in Group B (third sample); at the end of treatment (fourth sample); and on the day after treatment (fifth sample). Plasma GH levels showed a decrease (P < 0.01) in Groups A, B, C and D during treatment (third and fourth samples), while Group E only at the end of shearing (fourth sample). In the third sample, the highest GH levels were recorded for Group E (P < 0.05), while it was recorded in the fourth sample for Groups A and E (P < 0.05). Cortisol levels showed a clear increase (P < 0.01) in all groups during treatment, but Group A showed a decrease in the fourth sample in comparison to the third sample. Males in the second, third and fourth sample and Group A only in the fourth sample showed lower cortisol levels when compared with the other groups (P < 0.05). Plasma glucose levels showed an increase (P < 0.01) in all groups during treatment but Groups B, C and E showed the highest values (P < 0.05). Magnesium (Mg) showed an increase in all groups in the third and fourth sample, while sodium (Na), in the same samples, only in Groups B, C and D. Potassium (K) values showed a significant decrease (P < 0.05) only in Groups C and D at the end of shearing. These results show that GH secretion is influenced by all the stress procedure: separation, tying and shearing. Shearing, even if necessary for animals, causes a significant change of the blood parameters involved in the stress response.