8 October 2013

3 minute read

In an automatic milking system (AMS) feed is used as an incentive to encourage voluntary and distributed cow traffic to the milking unit.

Therefore the timing, placement and size of feed allocations need to be managed in order to achieve targeted milking events per day.

A behavioural study was conducted at the Camden AMS research farm in spring 2011, where a herd of 175 mixed age and breed cows received supplementary feed either prior to (PRE), or immediately after (POST) milking.

It was hypothesised that as PRE cows would have spent comparatively more time than POST cows since they ate their respective allocation of supplementary feed (at the time of exiting the dairy), they would be more motivated to go to the paddock in search of additional feed. Thus they would graze more intensively once they entered their pasture allocation.

On average, 60 per cent of daily DMI was supplied as grazable pasture (predominantly Ryegrass - Lolium perenne and Lolium multiflorum) in 2 allocations per day. The remaining 40 per cent of the daily allowance was offered as supplementary feed in a feeding area at the dairy, consisting of pelleted concentrates offered through 4 automatic feed stations, and a partial mixed ration.

Cows accessed each allocation for a consistent 12 h period of time and had an additional 10 h in which they were expected to voluntarily exit the allocation. Any cows that did not voluntarily exit a paddock were fetched and encouraged from the paddock to the dairy 2 h prior to the subsequent allocation closing for access.

Fifteen cows within each group were randomly selected as observation cows. Every 15 min during 24 h, trained observers recorded Presence (presence or absence of each observation cow at the time of each observation in a particular pasture allocation) and Grazing (animal with head close to forage sward, and actively searching or removing pasture from the canopy). Additionally, bite rate was recorded hourly by counting the number of bites taken per minute for at least 5 cows that were actively grazing.

The PRE cows started exiting the paddock 6 h after entering a defined allocation, whereas the POST cows started exiting 8 h after entering (Figure 1a). There was no difference between treatments in the proportion of cows ‘grazing’ in relation to the time since exiting the dairy (Figure 1b). A higher proportion of cows grazed during the first hour after exiting the dairy. There was neither an effect of time nor of treatment on bite rate. The average bite rate was 40 ± 1 bites/min.

Figure 1.Curves for cows present (1a where survival probability was the likelihood that a cow that had entered the paddock was likely to remain in the paddock through time) and that are grazing (1b) in the pasture allocation (at time since exiting the dairy) in a pasture-based automatic milking system when supplementary feed is provided either prior to (PRE; solid line) or immediately after (POST; dashed line) milking

The higher proportion of cows grazing during the first hour confirms previous studies in which access to fresh pasture acted as stimuli that were strong enough to initiate grazing. The higher proportion of cows grazing at 6 h, 12 h and 19 h after entering the allocation, also confirms the likelihood of cows to perform grazing in bouts, separated by periods of ruminating or idling. The behaviour observed whilst cows were in an allocation, together with the rate at which cows exited the paddock confirms that PRE feeding is a strong incentive to encourage cows to traffic from pasture to the dairy. However, cows’ response to feed availability and behaviour whilst on pasture is influenced more by pasture cover than supplementary feed location and resultant time since previous feed consumption.

In conclusion, cows in both treatments spent at least 6 to 8 h in the pasture allocation and had similar grazing behaviour (time and bite rate).

October 2013