A succinct summary of that would be that the smaller the mobs of cattle on a farm are, the greater will be the efficiency of feed utilisation because with fewer numbers a greater compatibility of the feed requirements of the individuals in the mob will be achieved.
While proving this in theory might be a cosy mathematical exercise, putting it into practice is a somewhat more challenging one because sorting out, maintaining, and managing a large number of mobs on one farm would prove a logistic nightmare.
Taken to extremes, any gains made would be far outweighed by the extra work and hassles created.
Accordingly, there have to be compromise solutions and I did indicate my intention to look at them in this issue. As a lead into this discussion I will start with a bit of bull – in fact a whole lot of bull.
Those in the industry with long memories will recall a time in the early seventies when the dairy price had slumped – a situation not too dissimilar to the present.
About the same time the market for bull beef was on the ascendancy as the United States hamburger trade had discovered bull beef was its ideal raw material.
It was thus suggested the intensive farming of bull beef was a viable economic alternative to dairying and considerable expansion of it occurred.
However, the experience of this type of farming was limited and new practitioners were on a steep learning curve.
Accordingly, newly formed bull beef discussion groups were well attended and at each meeting, for a very long time, the hot topic of debate was “What is the ideal mob size for a group of bulls?”
Too many and the bulls spent a considerable proportion of their time fighting, digging holes and wrecking fences with a consequent reduction in liveweight gain and profitability.
On the other hand, a whole lot of too small mobs created problems of workload and organisation and grazing management.
From memory, I think the general consensus was 30-40 bulls for the optimum mob size.
Certainly, I cannot recall any time before or since when the dynamics of livestock interactions was so intensely scrutinised.
I am strongly of the belief that the whole field of animal behaviour is one that is sadly neglected, from both the research and the practical viewpoints.
The point is that, in terms of general behaviour, there is no reason why the female of the species should be any different from the male.
It is not hard to identify the origin of the terms bully and bullying and there is generally plenty of this going on in a dairy herd – we are all familiar with the concept of the “boss cow”.
Her victims will be stress-prone and shy feeders and both these factors will be a brake on productivity. Smaller mobs will generally be more contented and a contented cow is a productive cow.
This also throws up another important factor to influence the timing and management of mob size and composition.
That is the stability of the mob. Back in time, as herds became increasingly larger, the practice of milking two herds on the one farm gained some traction.
One of the suggested advantages was, again, the compatibility viewpoint. Herds could be classed and fed as a preference herd or a routine herd. Cows could be regularly switched from one group to the other to cater for changes on condition and/or production – all very nice in theory but in practice not so much.
Any gains made by increasing compatibility in the herd would be generally more than negated by losses caused by the stresses arising from the unsettling effect of introducing strangers into the herd.
If my memory serves me correctly, that this is a real effect was confirmed by an earlier trial at the old Taranaki Research Station where liveweight changes were measured when the two-year-old heifers were merged with the mature herd. They lost significant liveweight until the pecking order was sorted out.
The interesting point, however, was that the mature cows also lost liveweight over the same period – admittedly not to the same extent but enough to indicate they also suffered some degree of upset and stress resulting from the disruption from the mixing.
As an aside from this it can be seen there is an advantage in amalgamating the heifers with the main herd well before calving so that at least will be one less stress from the many they will face in early lactation.
While I’m on the trend of herds
getting larger I can hear some critics of
my small is better philosophy raising the point that in the early days of the Large Herds Conferences surveys showed, contrary to expectations, cows in large herds achieved a significantly higher per head production than those in smaller herds.
To put this one solidly to rest, it is a classic example of faulty deduction along the lines of a table has four legs; a cow has four legs; therefore a cow is a table.
The fact that these cows performed better was not that they were in a large herd but rather that to be able to successfully operate the more complex and demanding large herd business the owners had to be above average in terms of energy, enthusiasm, innovation and business acumen.
So, it can be taken as indisputable that the smaller the mob the more efficient will be the feed utilisation.
However, the practice of grouping
cows to form mobs with the individuals in it having compatible feed demands has to be limited by the consequent hassles created and the necessity to avoid excessive and continual disruption to the mobs by altering their composition.
How this compromise is reached and what the number of wintering mobs will be is very much a matter for the individual farm because the optimal arrangement will be dependent on a myriad of individual factors relatively unique to it.
Certainly, there is no one size fits all. However, I offer the following as general guidelines.
Before June mobs should be formed on the needs of the individuals in them to gain condition.
If a cow is not at the desirable condition score 5 by the beginning of June it will be very difficult, if not impossible, to then achieve this by calving and it would take an inordinate amount of feed to do so.
Ideally all cows will be BCS 5 on June 1 then they could be split into their final wintering mobs.
The most important distinguishing factor in determining mob composition at this stage will be calving date because, with all cows at about BCS 5, the time to calving will be by far the most important factor influencing feed requirements.
Obviously, as always, flexibility in decision-making is required so lower condition cows and possibly some or all heifers and shy feeders can go with the earlier calvers but, to reiterate, calving date should be the main criteria.
For simplicity’s sake cows can stay in the mob they have been allocated to until calving. Then the picture then becomes somewhat murky.
In the past I have sometimes seen, on the one farm immediately post-calving, a milking mob, a colostrum mob, a springing mob, one or two dry cow mobs and possibly a few antibiotic and crook cows isolated.
While this might be optimal, I can well understand the desire to avoid this sort of complexity and in a big operation desirability might well have to give way to expedience and convenience.
Brian Hockings is a member of the management committee of the Stratford Demonstration Farm.
