CHANGES IN COMPOSITION OF FATTY-ACIDS OF THE FAT IN GOAT MILK DURING LACTATION

In the milk fat collected of 20 animals, the white short-woolled polled breed, the representation of fatty acids was studied ten times from day 1 to day 255 of lactation by gas chromatography. 22 fatty acids in total were determined with the number of carbons 8 and more. Majority fatty acids, whose average content exceeded 1 %, are presented in tables together with basic statistical data. In minority fatty acids minimum and maximum values are given in brackets as found during the lactation. The following fatty acids were identified: C8:0 (Tab. I), C8:1 (0.10 -2.70 %), C9:0 (Tab. II), C9:1 (0.00 - 6.60 %), C10:0 (Tab. III), C10:0izo (0.00 - 8.78 %), C11:0 (0.00 - 1.01 %), C12.0 (Tab. IV), C12.1 (0.00 - 1.02 C13:0 (0.00 - 0.34 %), C14:0 (Tab. V), C14:1 (0.00 - 1.07 %), C15:0 (0.10 - 1.71 %), C15:1 (0.00 - 1.78 %), C16:0 (Tab. VI), C16:1 (Tab. VII), C17:0 (0.06 - 2.29 %), C17:1 (0.00 - 2.29 %), C18:0 (Tab. VIII), C18:1 (Tab. IX), C18:2 (Tab. X) and C18:3 (0.00 - 0.62 %). The following basic changes in composition of fatty acids were found during lactation: After parturition when deposited fat starts to be mobilized, a high content of fatty acids C18:0 (Tab. VM) and C,8:1 (Tab. IX) and relatively low content C16:0 (Tab. VI) was recorded in colostral fat. A high proportion of fatty acids C14:0 (Tab. V) and C16:1 (Tab. VII) after parturition is probably of the same origin. In further period relative representation of fatty acids with 18 C is falling and the proportion of the fatty acid C16:0 (Tab. VI) is rising. In the period of green feeding fatty acids with 18 C are synthetized through ruminal microflora and their relative contents am increasing, in particular that of C18:0 (Tab. VIII), C18:1 (Tab. IX) and C18:3, but the representation of unsaturated fatty acids C14:1 and C16:1 (Tab. VII) is increasing too. The representation of fatty acids with 8, 9 and 10 carbons is fluctuating relatively little during lactation and without dependence on the stage of lactation arid nutrition. The variability of majority fatty acid content during lactation is lower compared with the literary data. Relatively higher representation of C9:0 acid (Tab. II) was found in goat milk fat. These differences were probably caused by different nutrition. Goats are usually on the pasture during summer and the feeding ration is composed practically exclusively of green forage. In our studies goats were reared in the stall and the summer, eventually autumn feeding rations contained except green forage and hay as well, ground barley and oat, and mineral and vitamin additions. In the first days after parturition the total fat content (Tab. XI) is highest and is falling to day 110 of lactation, to the end of studies it exhibits permanent increase. In dependence on the total fat content in goat milk, contents of some fatty acids are significantly changing during lactation. There were positive relationships to the total fat contents for C16:1 (r = +0.197), C18:0 (r = +0.202) and C18?1 (r = +0.305), negative relationships to the total fat content were found for C8:1 (r -0.209, C10:0 (r = -0.208) and for C16:0 (r = -0.262).