The most serious concerns over liquid feeding for pigs are initial cost and demand for on-farm professional training. Assuming financial and technical difficulties are overcome, the neophyte user is then faced with significant challenges that must be addressed successfully if pigs are to reap the full benefits of liquid feeding.
1. Fermentation
Although controlled fermentation can be advantageous, the opposite has detrimental effects on animal health. This is the major complaint regarding newly-established liquid feeding systems. Uncontrolled fermentation often results in increased populations of Escherichia coli, Salmonella, yeasts and many other possible pathogens. To this effect, acidification with lactic acid (or several other acids) to pH 4 is often recommended, as well as treatment with 300 ppm chlorine dioxide. It should be noted here that as each mixing and delivery system is provided with specific procedures for cleaning and disinfection, these guidelines must be followed strictly to ensure proper hygiene of the system.
2. Dry matter
Another crucial issue in liquid feeding is the dry matter concentration of the soup. The rule of thumb is three parts water for each part dry feed, or approximately 25 percent dry matter. Many older delivery systems were unable to deliver a thicker mix, whereas a less dense soup was undesirable because of increased effluent production. Research has clearly demonstrated that pigs can effectively use liquid diets even with 15 percent dry matter without any loss in performance, although a soup with 25 percent dry matter is strongly recommended for the first week post-weaning to ensure sufficient nutrient uptake.
3. Effluent production
Experience indicates that pigs consuming liquid diets produce more effluent, especially when fed liquid byproducts rich in protein and (or) salt. This can be a desirable effect as slurry becomes thinner and can be handled easier or, in contrast, an undesirable effect as more effluent must be disposed at greater cost. Nevertheless, it is recommended that soup dry matter concentration be kept above 20 percent to control effluent production
4. Water availability
All authorities recommend pigs be provided with free access to fresh, non-saline water, even when liquid diets contain no liquid byproducts and (or) normal sodium levels. Pigs require water at variable quantities according to individual body weight, growth rate, room temperature and health. In liquid feeding systems, a single drinker per 10-20 pigs is considered sufficient, although having a minimum of two drinkers per pen should be considered a good measure against possible blockage of a single drinker.
5. Feed refusal
It is occasionally reported that during the first few days (especially for weaned pigs), pigs previously unfamiliar with liquid feed may refuse to eat, despite no obvious faults with the feed. This is often resolved by placing some dry feed in lock-down feeders close to the liquid feed troughs for a couple days or until pigs start consuming liquid feed. For older pigs, placing a small amount of dry feed in the troughs is usually sufficient to indicate to them where feed is coming from. If the problem persists, then fault should be attributed to the feed or delivery system.
