Long- and short-term effects of omitting two weekend milkings on the lactational performance and mammary tight junction permeability of dairy ewes

Abstract

The long- and the short-term effects of omitting 2 milkings weekly in early (wk 8 to 14) and mid lactation (wk 15 to 22) were investigated in an experiment conducted with a total of 58 dairy ewes (40 Manchega and 18 Lacaune). Ewes submitted to 2 milking omissions were milked twice daily from Monday to Friday (0800 and 1800 h), and once daily on Saturday and Sunday (1600 and 1400 h, respectively). Individual data were collected for milk yield (weekly), milk composition (biweekly), and somatic cell count (SCC; monthly). Omitting 2 milkings per week in early lactation tended to decrease milk yield in Manchega ewes (-15%), whereas no effects were observed in Lacaune ewes. Averaged milk composition was not modified by milking omissions in either breed. Milking omissions in late lactation did not affect milk yield and milk composition in either breed. The SCC were unaffected by milking omissions in both breeds and in both stages of lactation. A sample of 22 Manchega and 11 Lacaune ewes were used to evaluate the short-term (daily) effects of the 2 milking omissions per week on milk yield and composition, udder health, and tight junction permeability, both in early lactation (wk 12) and in mid lactation (wk 20). Milking omission decreased milk yield, milk fat, and milk lactose contents on the first omission day in both breeds, with losses being more noticeable in early lactation than in mid lactation. Milk protein content and SCC did not vary by effect of the weekend milking omissions. After restoring the twice-daily milking routine on Monday, milk yield showed a compensatory increase that was greater in the large-cisterned than in the small-cisterned ewes, which allowed milk yield to return to Friday values in both breeds. Milk fat content increased during Sunday and Monday, reestablishing Friday values thereafter in both breeds. Weekend milking omissions in early lactation caused tight junction leakiness in both breeds, but mammary epithelia adapted to extended milking intervals when applied successively, recovering their tight state after milking. In mid lactation, the mammary tight junction showed leakiness only in Manchega ewes. In conclusion, 2 milkings per week could be omitted with no negative effects on milk yield, milk composition, and milk SCC values in large-cisterned dairy ewes, as observed in Lacaune and large-cisterned Manchega ewes. Losses in milk yield could be reduced if milking omissions were done from mid lactation in small-cisterned ewes.

Evolution of udder morphology, alveolar and cisternal milk compartment during lactation and their relationship with milk yield in Najdi sheep

“…East Friesian crossbred, Manchega, Sicilo-Sarde) and small-cisterned ewes that resembled unselected or non-dairy sheep. The percentages of Najdi's cisternal milk (55% and 67% during suckling and milking periods, respectively) were similar to the percentages reported in Manchega ewes (Rovai et al, 2002;Castillo et al, 2009), East Friesian crossbred dairy ewes (McKusick et al, 2002b) and Sicilo-Sarde dairy ewes (Ayadi et al, 2011). On the other hand, the percentages of cisternal milk in the current study were lower than those percentages in Lacuane (74-77%, Rovai et al, 2002;Castillo et al, 2009) and Sarda ewes (82%, Nudda et al, 2000).…”

Changes in the composition and fatty acid profile of Najdi ewes’ milk before and after weaning

“…The increased milk protein content during lactation was in agreement with the results obtained by Gargouri et al (1993) and Ayadi et al (2014), who found that milk protein content during the suckling period was lower than in the milking period. The average milk fat percentage (4.41%) in this trial was similar to the value reported by Abd Allah et al (2011) in Chios ewes and Ayadi et al (2014) in Najdi ewes, but was lower than the values (6.2-7.4%) reported by Nudda et al (2002) in Awassi ewes and Castillo et al (2009) in Lacaune and Manchega ewes. Breed differences and diet could explain the discrepancies in fat percentages between these results and those of previous studies.…”

“…According to Marnet (1997), the decrease in milk yield during weaning might be explained by the reduced emptying frequency and to a lesser degree by dam-lamb separation. When extended emptying intervals were practised, alveolar drainage decreased and intramammary pressure increased, all of which had negatively affected milk secretion, and eventually could have decreased milk yield (Castillo et al, 2009). The inconsistencies in daily milk yield dropping rates in this trial compared with other studies are probably due to the milking management, breed differences, and variation in cisternal size.…”

Estimation of udder cistern size in dairy ewes by ultrasonography

“…Cistern size is an important factor in determining the milkability (L abussière, 1988; Marnet and McKusick, 2001) and the adequate interval between milkings (Knight and Dewhurst, 1994;Salama et al, 2003). Animals that store a large proportion of milk in the gland cistern produce more milk, and are more able to tolerate extended milking intervals (Salama et al, 2004;Castillo et al, 2008b;Castillo et al, 2009). Moreover, cistern size plays an important role in controlling milk secretion because when the cistern reaches its full capacity, physical pressure and FIL concentration within alveoli are increased (Wilde et al, 1996).…”