Bovine colostrum: changes in lipid constituents in the first 5 days after parturition.

Despite the great interest paid to protein components in colostrum, fat also plays an important role in the supply of essential nutrients to provide energy, increase metabolism, and protect the newborn calf against microbial infections. This work aimed to elucidate levels of different fat components in colostrum, in particular fatty acid (FA), triglyceride (TG), cholesterol, and phospholipid contents. Colostrum samples from primiparous and multiparous (3-5 lactations) Holstein dams, fed the same ration indoors, were collected on the first 5d after parturition, analyzed, and compared with milk samples from the same cows collected at 5mo of lactation. Fat content during the first 5d of milking did not vary. However, the proportion of short-chain saturated FA increased and that of long-chain FA decreased. The concentration of n-3 FA was higher on the first day of calving than on the other days, with clear differences in the number and type of n-3 FA. Conjugated linoleic isomers and trans FA slowly increased from d 1 to 5, reaching a maximum at 5mo of lactation. Changes in the distribution profile of TG were observed as lactation progressed, with a shift from a prevalence of high-carbon-number TG (C48-50) on d 1 to a bimodal distribution (maxima at C38 and C50) on d 5, characteristic of mid-lactation milk. Cholesterol content was high in the first hours after calving and rapidly decreased within 48h. Colostrum sampled on d 1 also had a high content of phospholipids. Phosphatidylethanolamine and sphingomyelin were, respectively, lower and higher in the first 5d than in mid-lactation milk. The influence of lactation number on colostrum fat composition was also considered and significant results were obtained for all FA groups (except for polyunsaturated and n-6 FA) and TG content.

Study on the influence of pasture on volatile fraction of ewes' dairy products by solid-phase microextraction and gas chromatography-mass spectrometry.

The detection of markers of identification of the geographical origin of food is an attractive challenge and, as far as dairy products are concerned, this paper represents a contribution to this field. In this research the influence of feed on the volatile compound composition was investigated on milk, 2-mo-old cheese (Caciotta), and whey cheese (ricotta) obtained from the same flock of Sarda ewes, under standardized technological conditions. Three different types of pasture (mixture of Lolium perenne and Trifolium squarrosum; rough pasture; Avena sativa) were studied. Solid-phase microextraction combined with gas chromatography-mass spectrometry was used and principal component analysis was applied for statistical evaluation of the data set. The volatile composition was significantly affected by the type of pasture independently of the type of cheese and the ripening period. Moreover, a marker of rough pasture, tentatively identified as (E,E)-3,7,11-tri-methyl-2,4,10-dodecatriene, was detected only in milk and cheeses produced when the ewe flock grazed on that pasture.