Over the last six months we have received less than half our average rainfall, yet again we are hand feeding our cattle. With 30 years’ experience in ruminant nutrition research, Helena has the job of calculating what we feed the cattle to provide sufficient energy and protein to meet their maintenance and production needs. We also try and make the most cost effective decisions.
At present we have four groups of stock on the farm. Early lactation cows, pregnant dry cows in their second trimester, weanling bulls and yearling bulls. All of these cattle are on different levels of hand feeding. We also have 40 heifers and 10 steers on agistment on another property.
We have feed on hand which includes Dried Distillers Grain, wheaten hay, silage, lucerne hay, molasses and urea. All of our feeds are tested for feed quality, either at purchase or we send samples to Dairy One in the USA for analysis. There are still a few paddocks at Cadfor with feed of varying quality and quantity that the different classes of livestock can graze.
|Feed||Metabolisable Energy(MJ/kg DM)||Crude Protein %||Price landed($/tonne dm)|
|Dried Distillers Grain||12.4||24.4||284|
The other information needed to calculate the feed required are the average weight of the group and the desired production outcomes. The first calculation to make is how much energy is required to maintain the current weight of each animal. A simple rule of thumb, the energy required is equivalent to 10% of the liveweight. Our 650 kg cows need 65 MJ of energy to maintain their current weight.
Secondly, what is required to meet energy requirements for production? We know that it will take about 10 litres of milk to feed the calf. Again using rules of thumb, 5.5 MJ of energy is required for each litre of milk produced, 34 MJ is required for each kg of gain and there is an additional 10% of energy required for pregnancy in the second trimester.
|Group||Average liveweight (kg)||Production||Energy required per animal (MJ)|
|Early lactation cows||650||Calves growing @ 1kg/day||120|
|Pregnant cows||650||Calf growth||72|
|Yearling bulls||450||Growth @ 1 kg/day||79|
|Weanling bulls||320||Growth @ 1 kg/day||66|
It is also necessary to make sure we are meeting the protein requirements of the groups. Lactating cows require 10% crude protein in their diet, growing cattle between 12 to 15% while the requirement of dry cows is 7 to 8%.
The final piece of information to calculate is the total amount of feed each animal can consume. The voluntary intake (VFI) of cattle is driven by feed quality and production rate and is usually equivalent to 1.75 to 2.5% of bodyweight. For example a 650 kg animal consuming equivalent to 2% of its bodyweight will eat 13 kg of feed dry matter.
|Group||Voluntary Feed Intake at 2% liveweight (kg)||Dietary Crude Protein Requirement (%)|
|Early lactation cows||13||10|
So armed with these calculations, we can work out what to feed each group.
Lactating cows: (22 cows)
We give one bale of silage containing 250 kg of dry matter each day to this group or about 10 kg per cow. This gives 91MJ energy, a shortfall of 40 MJ per cow. There is vegetative mixed pasture in their paddock which would have an energy content of about 10 MJ/kg DM. The daily VFI of these cows is at least 13 kg. If they were to consume a further 3 kg of pasture these cows will easily be able to maintain their body weight and produce 10 litres of milk a day.
The crude protein content of the silage is 9.1% which is a little lower than the desired level of 10%. The pasture on offer would have a protein level of about 20% which would be sufficient to make up the shortfall from the silage.
Cost: $40 per day or $1.80 per cow per day
Pregnant cows: (38 cows)
These cows are on clean up duty. With their relatively low energy and protein requirement, these cows are currently grazing pasture in late vegetative stage of growth (ME 7-8 MJ/kg, CP 7%). Their VFI would be expected to be a little lower, at about 1.5 to 1.75% of bodyweight (9.75 to 11 kg dm).
Molasses urea licks help improve the digestibility of poor quality pastures by increasing the nitrogen to carbon ratio in the rumen. This effectively increases the CP% and ME of the total diet.
These cows are consuming adequate nutrients to meet their energy and protein requirements on the late vegetative pasture with access to a licker drum containing molasses and urea. (Estimated intake of 10 kg dry +pasture with ME 8 MJ/kg provides 80 MJ energy per cow per day)
Cost: $0.50 per cow per day
Yearling Bulls: (8 bulls)
These young bulls have grown well to date but with the sale season approaching we need to keep them growing. We have put these bulls in a paddock that we are planning to resow, we consider it a sacrifice paddock. There is very little pasture on offer and it would be of low quality. (ME 8, CP 9%).
We are feeding 3 kg DDG per head per day which will provide 37 MJ energy. If the bulls consume a further 6 kg as hay (54 MJ energy) it is expected that they will be growing at a rate 1.3 kg/day. We will need to weigh them to check our calculations.
Cost: $1.30 as hay plus $0.85 as DDG per bull per day ($2.15 per day)
Weanling bulls: (11 bulls)
We have put these youngsters on the best pasture we have on offer (ME 11 MJ/kg) and providing them with 2 kg DDG per day (24.8 MJ). Based on the VFI of 7 kg per day, these calves will be consuming about 5 kg pasture per day (55 MJ). With this amount and quality of feed, we would expect these bulls to be growing at 1.4 kg/day.
These youngsters were weighed today, we calculated their average post weaning weight gain at 1.46 kg/day.
Cost: $0.57 per bull per day
The take home message for feeding is that you need to be meeting the energy and protein requirements of the stock and are providing the quantity of feed to meet their VFI.