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Globally, the majority of dairy cows are milked twice a day (TAD); however, in pasture-based production systems, such as in Ireland, the idea of milking once a day (OAD) is being considered for reasons such as improved work-life balance. The immediate effects within a lactation, as well as the multilactation consequences of OAD, compared with TAD milking, require understanding. The objective of this randomized experiment was to compare OAD and TAD milking, over a 3-yr period, by examining the differences in milk production and composition, body weight (BW), body condition score (BCS), dry matter intake (DMI), udder characteristics, locomotion score, and milking time. Over the 3-yr period, 83 cows were enrolled in the experiment; 32, 44, and 48 cows in yr 1, 2, and 3 of the experiment, respectively. Each year, 23% of the herds were primiparous animals, while the remainder were second lactation or greater in parity. All cows were milked in the morning at 0700 h; only cows milked TAD were milked a second time each day at 1600 h. Cows rotationally grazed pastures for the duration of the lactating period and were housed during the nonlactating period. Milking cows OAD reduced cumulative milk yield by 26%, and milk solids yield (kg of fat + kg of protein) by 21%, across the 3 yr of the experiment when compared with cows milked TAD which produced 4,126 and 365 kg/cow, respectively. A contributory factor to the reduced production was a shorter lactation length (9.7 d) of the cows milked OAD compared with TAD (294 d). Milk fat percent of cows milked TAD was similar for all 3 yr of the study (5.05%), whereas milk fat percent of the cows milked OAD increased year on year, with each year being greater than the previous year (5.02%, 5.32%, and 5.70% for yr 1, 2, and 3; respectively). Milk protein percent was greater (+0.19%) for cows milked OAD compared with TAD which was 3.78%. Compared with cows milked TAD, total DMI for cows milked OAD was 22% less at the start of lactation (<167 d), but as the lactation progressed (>167 d) we observed no difference in DMI between treatments. Similar to the literature, milking cows OAD significantly increased average somatic cell score, both during (+16%) and at the end of lactation (+19%), compared with milking cows TAD which were 4.69 and 4.79, respectively. We detected positive aspects associated with OAD milking such as greater BW, BCS, and fertility performance. Milking OAD reduced both milking time per cow per day (reductions ranged from 34% in the first 4 mo of lactation to 43% during mo 5–9 of lactation) and milking time per liter of milk (−3.5 s/L) throughout lactation, leading to less labor inputs on-farm which can have positive implications for farmer work-life balance. The significant time saving and potential savings in costs (e.g., electricity) need to be considered in conjunction with the milk production reduction when considering OAD milking for the entire lactation. [ABSTRACT FROM AUTHOR]

• Early lactation once-a-day milking does not significantly reduce total lactation kg fat + kg protein. • Milking cows once daily for six or eight-weeks in early lactation reduces milk yield. • Milking time was up to 35% less when cows were milked once-a-day. • From week five of lactation somatic cell score was similar between treatments. The availability of labour during a compact calving period, can pose a challenge to dairy farmers. The objective of this study was to investigate, in comparison to twice-a-day (TAD) milking, the effect of short-term once-a-day (OAD) milking for four (OAD4), six (OAD6) or eight (OAD8) weeks directly post-calving on milk production, cow health and welfare. After each treatment finished their respective time on OAD milking cows reverted back to TAD milking for the remainder of lactation. A milk yield reduction of 21% was observed after the first four-weeks of lactation when milking OAD compared to TAD (618 kg/cow). When OAD milking continued until week six or eight of lactation milk yield reduction increased to 24 and 26%, respectively, compared to TAD. Following the 35-week lactation OAD6 (4,913 kg/cow) and OAD8 (4,815 kg/cow) treatments had a lower cumulative milk yield compared to the TAD cows (5,300 kg/cow); OAD4 were similar to all treatments (5,073 kg/cow). Following the first four weeks of the experiment the TAD herd had a higher milk fat, protein and lactose yield (+0.29, +0.17 and 0.28 kg/cow/day, respectively) than the three OAD herds which were not significantly different to each other (1.19, 0.72 and 0.95 kg/cow/day, respectively). Total milk fat, protein and lactose yields for the first six weeks of lactation were similar for all OAD treatments (44, 28 and 38 kg/cow, respectively) compared to the TAD treatment (54, 33,and 47 kg/cow, respectively). Following the first eight-weeks of lactation milk fat, protein and lactose yields were highest for the TAD (72, 45 and 65 kg/cow, respectively); OAD6 and OAD 8 were similar, OAD4 was similar to OAD6 but higher than OAD8. There was no difference in kg fat + kg protein (MSY) between treatments at the end of lactation. During the first four weeks of lactation milking cows OAD increased (+ 0.95 units) somatic cell score (SCS) compared to cows being milked TAD (3.26 units). From week five of lactation onwards there was no difference in SCS between any of the treatments. Milking time was consistently less (up to 35% less) when cows were milked OAD compared to TAD. The likelihood of milk leakage from udders pre-milking was significantly higher with OAD compared to TAD milking. There was no effect of treatment on locomotion score or fertility. The results of this study indicate that OAD milking for a short period of time in early lactation may be a viable option to reduce labour requirements without having a negative impact on cow milk production or welfare indicators. [ABSTRACT FROM AUTHOR]

Colostrum, the first postpartum secretion of the mammary gland, plays a vital role in the nutrition, development, and immunity of a newborn calf. We characterised the protein profile as milk transitions from colostrum to transition milk over the first 5 days of lactation, collecting samples on d0, d2 and d5 after calving. Protein concentration decreased significantly after d0 (colostrum) before stabilising. Principal component analysis revealed samples clustered by day postpartum, with a limited effect from parity. In total, 471 proteins were identified across all samples; 199 protein groups showed altered relative abundance by day of lactation (fold change ≥2, P < 0.05), but none were altered significantly by parity. Higher relative levels of immune proteins were found in colostrum, and milk fat globule membrane proteins were found to increase over early lactation. Our findings provide a better understanding of the dynamics of the protein profile of bovine milk in early lactation. [ABSTRACT FROM AUTHOR]