Pig Feed Pellet Size & Its Impact on Pig Performance 

Pig Feed Pellet Size & Its Impact on Pig Performance

Uses of Pig Feed

Pigs have a relatively simple digestive system, and the hay, silage, or pasture grass are not available for pigs to utilize. So the farm-grown grains, such as the wheat bran, rice bran and corn meal, etc. are frequently used as the single feed, or the compound feed by mixing them with a nutrients supplement that includes protein, vitamin and minerals, etc. According to feed appearance, the compound feed can be divided into feed meal, pellet feed, crushed feed, extruded feed, compressed feed, liquid feed, floating feed, cubed feed, etc.

Pig feed plays different roles for pig production. Piglets eat the feed mainly for growth and maintenance; mature pigs use feed primarily for maintenance and reproduction; the digested feed that is not for growth, maintenance, or reproduction is reserved as body fat.
1.For growth: feed helps the increase in size of bone, muscle and skin cells.
2.For maintenance: feed supplies the energy for normal pig activities and recover of worn body tissue.
3.For reproduction: feed supports the growth and development of unborn pigs during the gestation, from mating to farrowing. And high-quality feed helps pigs lactation performance.
4.For fattening: feed facilities the formation and deposition of fat tissue under the skin, around muscles and in the body cavity.

Using Pellet Feed for Swine Production

The technology of making pellet feed has been around for many years and pellet feed is also widely employed in livestock raising, including pig feeding. Pellet swine feed can be made from complete formula feed or single feed by pressing action. And usually it is cylinder-shaped with different sizes.

Advantages of pellet feed for pig performance
Due to the finely ground ingredients in pelleted diet, both ADG (the average daily gain) and feed efficiency can be further improved compared to a diet containing a larger particle size. The improvements are a result of the enhanced palatability, reduced wastage, and improved nutrient utilization. In fact, one of the main reasons for processing swine feed into pellets is to take advantage of the feed ingredients property of being finely ground.

Pig Feed Pellet Size and Pellet Quality

Pig feed pellet size has two dimensions: the feed pellet diameter and the feed particle size (the grinding fineness of ingredients). The conventional wisdom shows that small pigs prefer feed pellets with small diameter and large pigs prefer feed pellets with large diameter. But a lot of experiments indicate that pellet diameter has no significant influence on pig performance; the particle size is a leading factor affecting feed quality, thus pig performance.

Effect of particle size on pellet quality
1.Effect on nutrients uniformity
In terms of mixing process, if there are various raw materials, small particle size means slow feed ingredients mixing, but high mixing evenness, which ensues the nutrients uniformity
2.Effect on feed pelleting
In the feed pelletization process, finely ground feed ingredients have large superficial area, so they can get good conditioning, full curing, and total permeation of water and heat; the pelleted feed comes with good caking property and high stability. At the same time, the ground materials with small size reduces the wear of die,which means high pelleting efficiency.

Impact of Feed Pellet with Different Particle Size on Pig Performance

Particle size is the mean geometric diameter of particles measured in microns and the geometric mean standard deviation of the particle distribution.

1. Impact on pig gastrointestinal tract and digestive function
Experimental results express that coarse grinding will lead adverse reaction, cornification and damage to pig gastrointestine, thus affecting the nutrients absorption. However, fine grinding will increase feed process cost and may result in feed bridging, dust problems and the incidence of gastric ulcers (increase of gastric acid and pepsin activity is the origin) in swine.
2. Impact on feed efficiency
When the particle size of feed ingredients is reduced, the surface area of the cereal is increased. This will allow greater interaction with digestive enzymes, which helps a lot with the improvement of feed conversion rate.

Impact of particle size on pig performance experiments
1. Weaned pigs
A study conducted at Kansas State University demonstrates the effects of particle size on weaned pig performance. In the study, 192 pigs (initial weight 13 to 18 pounds) were fed either corn or sorghum based diets.
The grains were either processed by a hammer mill or a roller mill, and the hammer mill was equipped with an 1/8 inch (539 to 624 microns) or 1/4 inch (722 to 877 microns) screen. By adjusting the roller gap and feeding rate, each kind of grain was rolled either fine (822-855 microns) or coarse (1,147-1217 microns).
It can be learned that fine grinding or rolling reduced mean particle size of the diet. Although the differences in particle size did not affect average daily gain (ADG), feed efficiency (F/G—feed/gain) was improved by either fine grinding or rolling. By combine the data of grain type and processing method and classifying it only based on particle size, the improved feed efficiency appears to be a result of improved nutrient digestion.

2.Growing-finishing pigs
For growing pigs, a research from Healy et al. showed that reducing particle size from 900 microns or greater to 500 microns had little effect on daily gain, but reduced average daily feed intake resulted in improved feed efficiency.
For growing-finishing pigs, several studies have indicated that grinding of less than 500 microns (to the lowest particle size tested) continues to improve feed efficiency. The F/G from research in the 1990’s demonstrated a 1.2% improvement for each 100 micron reduction in particle size. More recent research indicated a 1% improvement in F/G for each 100 micron reduction in particle size.

3. Lactating sows
The research using 100 lactating sows was conducted at Kansas State University. Wondra et al. (1995) fed lactating sows diets of 1200, 900, 600, or 400 microns, based on corn that was ground by either a roller mill (1200 microns) or hammer mill equipped with a 3/8, 1/8, or 3/64 inch screen.
It turned out that litter weaning weight gain increased linearly (P< .05) as particle size decreased from 1200 to 400microns; feed intake increased linearly (P< .05) as particle size was reduced; digestibility of dry matter, energy and protein in the diet all improved linearly as particle size reduced. Actually, the improved digestibility is the reason that litter weaning weight was improved as particle size was reduced.
Stomach ulcers and keratinization was increased as particle size was reduced, since stomach ulcers and keratinization are always related with finely ground diets, and keratinization is an indication of stomach irritation that may cause ulcers.