Ken Geenty offers advice for experienced and inexperienced farmers wanting to feed stock correctly to ensure enough energy for reproduction and growth.
Most farmers intuitively know how much feed their animals need but often it’s wise to refresh with published guidelines. For students and young farmers, use of the guidelines is a must, particularly when starting out.
Farm animals, just like us, will not survive and thrive if there are feed deficiencies.
Good reproduction and growth of progeny are the rewards for correct feeding of sheep and beef cattle. This means enough tucker for consistently good body condition in adult breeders and targeted growth in progeny.
Because the key feed ingredient is energy, the metabolisable energy (ME) system has been adopted for farm animals worldwide. The pathway between gross energy in feeds and metabolisable energy available for production in animals is shown in Figure 1. Put simply, the net energy in feeds is available as ME to the animal for production after losses in faeces, urine and fermentation in the rumen.
This ME system is simple and easily applied. The quantities of ME in pastures, forage crops and supplementary feeds are readily available online and in publications.
Other important dietary components such as protein, fibre, minerals and vitamins are conveniently balanced in high quality pastures and forages.
The exception is where there are known mineral deficiencies in the soil, e.g. selenium, cobalt and copper in some areas of New Zealand. These can be corrected with fertilisers or administered directly to animals. Many supplementary feeds such as cereal grains are deficient in protein and some minerals and vitamins, which also need to be corrected. This information is normally available with the published feeding tables.
A good place to start finding sheep and cattle feeding information is the Beef + Lamb NZ website beeflambnz.com where “Making every mating count” and “Guide to NZ cattle farming” have comprehensive tables of feed requirements.
Handy feeding guidelines, including pasture production in various areas, is available on the Farmax site www.farmax.co.nz
The trick is to provide animals with enough feed to meet their ME requirements for the desired production level.
ENERGY REQUIREMENTS
It’s important to remember that feeding isn’t a precise activity but, using available guidelines and some simple rules of thumb, you should be able to get close to animal needs.
A few worked examples of planned feeding of sheep or cattle given here can be the basis of plans for your particular situation.
The ready reckoner table provided (left) relating feed drymatter to ME is a useful tool for your feeding plans. For example, a mob of ewes with 150% of lambs will need about 30 MJ ME/day during early-mid lactation. On good quality pasture with 12 MJ ME/kg DM, ewes will need to eat about 2.5kg of pasture DM/day. This means liberal feeding by either set-stocking of ewes on pastures with at least 1200kg DM/ha or rotational grazing from over 1200kg DM/ha to no lower than 1000kg DM/ha.
From the pasture length graph in last month’s issue of Country-Wide, or using the pasture sward stick, the above spring pasture quantities mean set-stocking at about 3cm or grazing pasture down from 4-5cm to 2cm.
A rule of thumb such as the “gumboot test” can be a practical guide with pasture length at or above the big toe being at the upper level for sheep and the ankle for cattle.
A handy pasture “sward stick” relating length to DM yield, developed jointly by Farmax and B+LNZ, is available from either organisation.
The amount of ME for beef cattle and their calves during early-mid lactation and grazing medium quality pasture on easy hill country would be up to 150MJ ME each day. Extrapolating from the ready reckoner this amounts to 15kg pasture DM. Such a large quantity of feed consumed would require pastures about 12-15cm in length or 3000kg DM/ha.
Because spring pastures generally have a drymatter content of about 20%, the quantities of fresh herbage eaten are five times the weight of drymatter. Therefore lactating ewes will eat up to 12.5kg of green pasture each day, and cows 75kg – equivalent to a sugarbag full for sheep and a large sack for cattle. These big quantities of wet material eaten each day, equivalent to 15-20% of adult liveweight, show the incredible feed intake capacity of ruminants and the reasons why they graze for a large proportion of the day and night.
SUPPLEMENTS FOR PREGNANCY AND MAINTENANCE
The time that feed volume causes most problems is during pregnancy when the ME requirements of sheep and cattle are rarely met from pasture. This is due mainly to competition for space with the growing foetus and placenta. Therefore during pregnancy, when both ewes and cows lose body condition, supplementation will minimise losses. The supplement should have a higher DM content and equal or higher ME than the pasture being grazed.
The amount of supplement offered will be pretty much a judgement call but can be guided by monitoring body condition score or liveweight. Maintenance of body condition score during pregnancy in both sheep and cattle has huge advantages in both survival and viability of lambs and calves owing to good early supply of milk.
For ewes at maintenance during winter or over a dry summer when limited pasture supplies only 75% of required ME to hold body condition, supplementation can be with cereal grain fed in the paddock. To make up the 25% of the diet for maintenance using grain with an energy content of 12MJ ME/kg DM would require 0.25kg of grain per ewe per day. Care needs to be taken to introduce the grain gradually over 7-10 days starting at 100g/ewe each day to avoid digestive upsets. No mineral or protein supplementation will be required until over 75% of the daily ration is cereal grain.
Similar principles apply to growing lambs to boost growth rates. Use of the tables of ME requirements is recommended to ensure daily needs are met for the desired liveweight gains.
For adult beef cattle during periods of pasture shortage, several types of supplements can be effectively used. Silage is commonly fed to pregnant cows during winter. Requirements for 500kg cows during early-mid pregnancy are around 100MJ ME per day. Good quality pasture silage will have a DM content of about 25% and contain 9MJ ME per kg DM. To meet daily pregnant cows’ ME needs, a total of 11kg of DM or 44kg of wet silage is required, amounting to 2.2 tonnes per 50 cows. If a green pick is available in the paddock the quantity of silage fed can be reduced by 10-15%.
FORAGE CROPS
Pregnant cows are often break fed forage crops such as rape during winter. An example calculation of the break size needed for 50 cows each day follows:
Maintaining body condition in 500kg pregnant cows as above requires 100MJ ME per day or just over 8kg DM – rape has about 12MJ ME/kg DM. With an average yield of 7t of DM per ha, or 0.7kg DM per square metre, this means each cow will need about 11.5 sq m per day. To allow 15% trampling wastage, allocation will be 13.5 sq m per cow or 675 sq m for 50 cows. If the feeding face is 75m wide then the electric fence will need to be advanced 9m each day.
These above example calculations give some basic pointers for working through your own feeding plans. For more help, including a FeedSmart App, go to B+LNZ at beeflambnz.com and search using “feeding calculator”.
- Ken Geenty is a primary industries consultant.
