The effect of social stress on milking efficiency in dairy ewes differed in milk flow kinetic

- Three groups of ewes differed in types of milk flow during standard machine milking (one emission, plateau, two emissions) were subjected to social stress.
- Tsigai and Improved Valachian breeds with Lacaune were tested.
- Significant decline of total and machine milk yield was observed during milking under social stress as compared to control milking in all three responses.
- The pattern of emission of milk in animals under stress was different than in control ewes.

The aim of this study was to evaluate the effect of social stress on milking parameters in dairy ewes raised in Slovakia. Twenty-seven cross breed ewes of Tsigai and Improved Valachian breeds with Lacaune were included into the experiment. Ewes were selected from the flock on the basis of their milk flow type during the two pre-experimental milkings. According to milk flow types, they were divided into three groups representing three patterns of milk flows - bimodal group (GB; 11 animals), non-bimodal group (NG; 8 animals) and plateau group (PLG; 8 animals). Before milking, the following treatment to each ewe was applied: social isolation (free movement in parlour alone) in dairy parlour for at least 4 min, and afterwards, the ewe was fixed into a milking stall and disturbed by unknown person standing in front of the head who was gently touching it during whole milking (milking under stress). Parameters of milkability and milk flow type were measured using electronic collection jar. For statistical evaluation, data from last pre-experimental (control) and milking under stress were compared. The significant decline of total and machine milk yield was observed during milking under stress as compared to control milking in all three groups. The machine stripping yield and milking time were reduced in BG and peak flow rate in NG. During milking under stress, the clear increase of non-bimodal milk flow types was recoded compared to control milking in BG and PLG. In conclusion, milk flow kinetic can serve an important parameter for evaluation of physiological response of ewes to milking and for further improvement of milking conditions and increasing the milk performance of ewes.