Abstract
The study presented was designed to ascertain the influences of a change in the milking condition on the intramammary pressure, milking rate and milk yield of seven Holstein cows. Experimental treatments consisted of abrupt changes in housing system by moving the cow from loose barn to tie-up stall and in milking procedure by altering from farm routine to experimal routine. The experimental routine incorporated to following treatments : (1) insertion of cannula to right-front teat for the measurement of imtramammary pressure (2) washing of the udder with warm water (3) teat cup application on theremaining three teats, after 30 sec. (4) machine milking with a De Laval portable unit, operated at a vacuum of 35 mm Hg. with pulsation ratio of 1 : 1, at 54 cyc. (5) stripping the last milk from udder by machine (6) removal of teat cup.
The results were as follows.
1. At the first milking, after a change in milking condition, there was considerable variation in the intramammary pressure change of various cows during milking routine. No discernible change was observed in two cows and a rise in pressure after a latent period of 1 min. 30 sec. was observed in three cows. The rise in pressure promptly after udder stimulation was observed in the two others. In one of these cows, the pressure rose gradually, whereas the pressure rose abruptly in another cow.
2. Intramammary pressure of cows was also variable in the course of adaptation. In the cow no descernible change in the pressure at the first milking, was observed extremely high but not abrupt rise in pressure at the second and the third milkings. At the fourth milking the cows began to responed to the experimental milking routine and was achieved the abrupt rise in pressure after the latent period of 1 min. 30 sec. The latency of cows attained to 30 sec at the fifth and the subsequent milkings.
On the other hand, slightly high pressure level and rise in pressure after the latency of 1 min. 30 sec. in the cows the latent period of 1 min. 30 sec. at the first milking, and then after the latency of 30 sec. at the third and the subsequent milkings. At the third milking, however, pressure level was slightly higher than at the subsequent milking.
3. Milking rate and milk yeild were more related to the degree of intramamary pressure rise than the reduction in latent time. On the other hand, when pressure level was extremely high, milking rate and milk yield have attained the level of normal, inspite of pressure being not rise after udder stimulation.
4. It appears that milking rate and milk yield in the course of adaptation associated with activation of the sympathetico-adrenal systerm, some special feature of morphology of the udder such as udder capacity, tonus of the tissue lining of the teat and gland cistern, and the amount of residual milk.
