Changes in teat parameters caused by milking and their recovery to their initial size

Dairy cows of 2 breeds, 74 Holstein (H) and 72 Czech Fleckvieh (C) cows in the 1st (H, n=38; C, n=38) and 2nd lactation (H, n=36; C, n=34) during the 1st period (n=74; H, n=40; C, n=34; to 150 days) and the 2nd period of lactation (n=72; H, n=34; C, n=38; above 150 days) were observed. Differences in external and internal proportions of teat closely before (the 1st measurement), immediately after (the 2nd measurement) and 3 h after milking (the 3rd measurement), udder conformation evaluated by linear description, somatic cell count, daily milk yield and the time of milking were evaluated in relation to the effect of breed and period of lactation. The length of the teat canal, area of the teat end, and wall thickness were measured from the axial picture recorded by ultrasound Aloka SSD500 (Aloka Co., Ltd., Tokyo, Japan). Significant interbreed differences were detected in external as well as internal teat proportions (P < 0.05-0.001). Relative changes of teat diameter, comparing C and H cows, differed significantly between the 1st and the 3rd measurement (P < 0.05). The length of teat increased during milking and didn't achieve the beginning size during 3 h after milking. Significant diiference in the length of teat between the 2nd measurement and the 3rd measurement was determined in H cows only (P < 0.001). The most significant changes of the length of the teat canal and the area of teat were found in both breeds between values measured closely before and immediately after milking (P < 0.5-0.001). Wall thickness was strengthen in C cows (+15.6%) during the 2nd measurement according to the 1st (P < 0.05), while difference represented +18% (P < 0.001) in H cows. Non-significantly higher values of external proportions of teat were measured in the 2nd period of lactation except diameter of teat closely before milking. Internal proportions of teat were always significantly higher in the 2nd period of lactation in relation to the 1st period. Prolongation of teat canal by 0.15 cm (P < 0.01) closely before, by 0.16 cm (P < 0.001) immediately after, and by 0.13 cm (P < 0.01) 3 h after milking was measured in the 2nd period of lactation. The area of teat end measured before milking was significantly larger in the 2nd period of lactation (P < 0.01).