The trade-offs when altering milking frequency and timing for pastoral, block-calving dairy farms : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University

Abstract

The purpose of this thesis was to quantify the effect of milking frequency and intervals on elements of the farm system, which included milk production, cow behaviour and farmer’s sleep. Dairy farmers face challenges attracting and retaining staff, partly due to the difficulty meeting the desires of the modern workforce which include flexible work hours and regular time off. The task of milking fundamentally impacts the ability of dairy farms to meet these desires. Milking contributes to a large proportion of the hours spent working on dairy farms. The number of milkings (milking frequency) and their timing (milking interval) within a day influence the number of hours spent milking and at what time in the day they occur. Milking 3 times in 2 days (3-in-2) reduces the amount of time spent milking compared to milking twice a day (TAD), without reducing milk yield as much as milking once a day (OAD). However, there are a variety of ways these milkings can be arranged within the 2 days, resulting in a variety of 3-in-2 milking intervals that have had little to no exploration. To determine the effect of milking interval within a 3-in-2 milking frequency on milk yield and composition at 2 stages of lactation and compare these with OAD and TAD milking, study 1 milked 5 herds of 40 cows at 5 different milking intervals at early (34 days in milk) and mid (136 days in milk) lactation. The milking treatments included once a day (OAD), 3 variations of 3-in-2 milking: an 8-20-20 hour, 10-19-19 hour and 12-18-18 hour interval, and TAD with a 10-14 hour interval. When comparing 3-in-2 milking intervals, a small numerical but statistically insignificant difference was observed in milk and component yields, through both stages of lactation. Consequently, the results of this study suggest that farmers using 3-in-2 could choose a shorter milking interval on the day with 2 milkings. Or alternatively, farmers have the flexibility to select a milking interval that suits best their requirements without significantly compromising milk yield. In agreeance with previous literature, decreasing milking frequency was associated with decreasing protein, lactose and milk yield. At mid-lactation there was no significant difference between TAD and the 12-18-18 interval of 3-in-2 for milk and component yields, providing an opportunity for farmers to decrease the number of milkings by 25% in later lactation without compromising milk production, when it’s past peak. The effect of milking interval and milking frequency on milk production is not the only factor that will influence a farmer’s decision to alter their milking schedule. When cows are milked less frequently their walking to and from the dairy is reduced and their amount of time spent at pasture increases; however, how this impacts behaviour has had very little investigation. To explore the effect of milking frequency on cow behaviour, in study 2, an exploration of an existing dataset showed that there were changes in cow behaviour when milking frequency changed. CowManager tags, which provide minutes per hour in one of five behaviour categories (active, not active, high active, ruminating, and eating) were attached to cows (n=29) transitioning from a twice a day (TAD) to a 3-in-2 milking schedule at mid-lactation (85 days in milk). When transitioned to 3-in-2 milking, activity significantly increased (+32.3 mins/cow/day; P<0.05), despite less walking to and from milking. When cows were milked 3-in-2, eating time was less (-1.99 mins/hour/cow) during daylight hours and greater during dark hours (+1.57 mins/hour/cow) when compared with when they were on the TAD milking schedule. Ruminating time was not different during daylight but was less during dark hours (-1.64 mins/hour/cow) when cows were milked 3-in-2. These findings indicated that in mid lactation, reducing milking frequency provided cows with more time for social interaction and/or feed searching behaviours, as evidenced by their increase in activity. It also indicates that the timing of milking may influence diurnal behaviour patterns. This study was limited by the short period of observation, and lack of comparative treatments, so a third study was conducted for a more in-depth analysis of milking interval on animal behaviour. Cows from study 1 had AfiAct pedometers attached, which measured steps per hour, and a cohort of 8 cows per treatment had the aforementioned CowManager tags attached as well. Cows that were milked OAD had the lowest activity in the paddock, 86 and 133 steps cow/hour less than 3-in-2 groups at early and mid-lactation respectively, and 65 and 135 steps cow/hour less than the TAD group. Cows milked 3-in-2 were also less active in the paddock on the day they were milked once (approximately 40 steps less per hour at early lactation, and 80 less at mid lactation). However, cows that were milked 3-in-2 were more active than TAD cows in early lactation, similar to what was observed in study 2, although this result was not consistent at mid-lactation. When milking was later in the afternoon, the timing of grazing became later. This was observed when comparing the 12-18-18 3-in-2 group milked at 5PM, in comparison to the 8-20-20 3-in-2 group milked at 2PM. Therefore, altering milking frequency and timing will result in cow behaviour change. Finally in study four, to determine whether milking frequency effects farmer’s behaviour, farmers milking either OAD (n=11) or TAD (n=22) in the South Island of New Zealand wore a sleep measuring device (OuraTM ring) for 90 days over the spring calving period. Neither OAD or TAD farmers were getting sufficient sleep over the calving period (6.3 hours compared to the recommended 7-9 hours). Furthermore, there were no significant differences in sleep quality or quantity between people working on farms milking OAD and TAD. However, this study was limited by the amount the rings were worn by the study participants, and the number of farms involved. Wake time, connected to milking time, was correlated with total sleep time. When milking time became earlier as calving progressed and more cows were needing to be milked, total sleep time decreased. This study demonstrated that there were factors other than milking frequency, such as milking time, farm management, weather and role on farm that were more influential on sleep quantity and quality. Overall, milking frequency and timing was shown to affect milk production and cow behaviour, with just milking timing affecting farmer’s sleep. The relationship between milking frequency and timing to milk production, cow and farmer behaviour are multi-directional, therefore there is no one milking frequency or schedule that seems to provide a positive impact on milk production, cow behaviour and farmers sleep at the same time. However, 3-in-2 from mid lactation onwards seems to provide the biggest opportunity to positively impact all three areas. The choice of milking frequency and milking interval chosen on farm will be dependent on the goals that the individual farmer is trying to achieve. This thesis has provided new information for farmers to be able to make that choice with more confidence in the likely outcome.