The effect of milking frequency reduction from twice to once daily on mammary physiology and animal welfare of two dairy Greek sheep breeds

The objective of this study was to investigate the effect of milking frequency reduction from twice (TDM) to once (ODM) daily on mammary physiology, activities of all milk enzymes implicated in the plasminogen activating cascade and animal welfare in dairy ewes. Thirty-eight dairy ewes (Chios, n = 22; Karagouniko, n = 16) under the same dietary and management conditions were used in a 14-wk experiment lasting from the 92nd to the 188th day of lactation period. The ewes were distributed in two equal groups of animals per breed. The first 14 days served as an acclimatization period and once per day milking started at the 106th day following parturition and lasted 12 weeks. A significant decline in milk production of ODM ewes was observed compared to that of TDM ewes (−29.2%, P < 0.001). Enzymatic activities of plasmin (PL), plasminogen-derived (PG) and plasminogen activator (PA) were significantly increased in the milk of ODM ewes compared to that of TDM. Furthermore, the sum of PL + PG activities was increased in ewes milked once daily and this indicates possible enhanced entrance of plasminogen towards milk. Increased blood lactose was observed in the ODM ewes at the 108th d following parturition, 2 days after the milking frequency reduction was started, a finding indicating that the permeability of the tight junctions was compromised, although the leakiness of tight junctions was a transient phenomenon. Finally, no significant signs of distress were observed in ODM ewes. Thus, ODM treatment does not affect negatively the welfare of dairy ewes. Overall, the adaptation of the ODM practice is not recommended for the Greek farmers despite the apparent improvement of their quality of life.