Understanding the weight of feed
The amount of feed your pigs need depends on the things that vary most in piggeries, i.e. age, weight, genotype (a combination of genes that produce different types of pigs), sex, environment and the time of year.
The other important element, assuming all nutrients are adequately balanced, is the energy content of the feed.
You can think of feeding pigs in terms of the amount of energy they eat each day. This is different to the weight of the feed they eat each day.
The amount of feed given depends on the diet’s energy content and the total energy to be fed each day. Of course, the pigs must be physically able to consume this amount of feed during the day.
When deciding how much feed to give your pigs, use your knowledge of the herd’s past performance to work out the energy they need each day to perform their best. From this figure, you should be able to calculate the total amount of daily feed.
For example, we want the pigs to consume a maximum of 32 MJ of energy per day. In summer, diets are often based on barley, while, in winter, diets are based on sorghum. Each diet is balanced and contains adequate amounts of protein and lysine. However, barley diets usually have less energy than sorghum diets (13.1 MJ DE/kg compared with 14.2 MJ DE/kg) because barley contains more fibre than sorghum. So if we want to feed them 32 MJ DE/day, we need to calculate how many kg/day we feed them.
- (32 MJ DE/day) ÷ (13.1 MJ DE/kg) = 2.44 kg/day
- (32 MJ DE/day) ÷ (14.2 MJ DE/kg) = 2.25 kg/day
The difference in weight between the two diets is enough to affect the pigs’ performance. For example, feeding 2.44 kg of a sorghum diet may result in fat pigs. On the other hand, feeding 2.25 kg of a barley diet could cause the pigs to grow slowly.
In the summer heat, pigs often eat less food than in winter, which causes a problem. Pigs need to eat 32 MJ/day but they do not want to eat that much. One way to overcome this is to feed them a higher energy diet by adding a high-energy ingredient, such as animal fat or edible oil. This ensure that, although the pigs are eating a smaller amount of feed, they are still consuming an adequate amount of energy.
Similarly, sows feeding their first litter may need more energy than they can obtain from their current diet and the diet may need to be increased in energy density compared with the diet for older sows.
Make sure you know the amount of feed you are feeding them. If you use a bucket to measure the feed, ensure you know the weight of feed it holds. When you change diets, weigh the bucket full of feed again, as you may find that it is different. For example, after filling a 10 L bucket with a bulky feed based on barley (more fibre), you may find that it weighs 4 kg.
However, if you then fill an identical bucket with a denser feed based on sorghum, it could weigh 7 kg. There will be a greater difference in weight between mash feeds when the base grain changes than pelleted feeds. If you are using ready-mixed feeds, check the density of each load.
Live weight and sex differences
Young pigs need fresh food available all the time. This is called ad libitum (ad lib for short) feeding. Weaner pigs have a small stomach, which limits the amount they can eat, so they need a good-quality diet. Depending on the age at weaning, you may need to feed them a ‘creep’ diet until about five weeks, and then a ‘weaner’ diet until about nine weeks (approximately 20 kg).
After that, feed ‘grower’ diets, which are lower in lysine than weaner diets, until 13 to 14 weeks (40 to 45 kg). Depending on genotype, most pigs can be fed ad lib to this age or weight.
The length of time that grower pigs can remain on ad lib feeding depends on their genotype and sex. Generally, the better genotype pigs can be fed longer to appetite without getting fat.
In many commercial herds, the pigs have been selected for lean growth and can be fed to appetite without getting too fat for their market.
However, this may not be the case for all piggeries so feed intake may need to be restricted (see Table 1)
However, in the long run, the answer involves changing the feeding system to minimise waste.
To obtain even better results from your pigs, split up the sexes and, in the period after they reach about 50 kg live weight, feed the females less energy per day than the males. Female pigs start laying down fat at an earlier age, so feeding them generously could result in more overfat pigs. Feed the males a higher lysine/energy level.
Buying or mixing feed
Whatever the source of feed, whether ready-mixed or farm-mixed, you need to know:
- the amount of energy in it (MJ DE/kg)
- the lysine/energy ratio (g lysine/MJ DE).
If you mix your own feed, look for these figures in the diet specifications. If not, ask your feed manufacturer to give you the specifications of their ready-mixed diets. You need to know whether the diets match your pigs’ needs and are economical. Some feed companies will discuss the diets that your pigs need and custom mix to your specifications. You can also ask feed suppliers to advise when diet specifications or ingredients change.
When comparing feed prices, whether between feed companies or diets computed for your piggery, do not focus only on the cost per tonne.
A better method of assessing feed price is cost per unit of energy (cents/MJ DE), while accounting for any difference in the lysine to energy ratio. Each kilogram of feed contains a certain amount of energy, which pigs use for growth. You need to calculate the cost of the energy that the feed provides to find the true value of the feed to the pigs.