Study results In their research, Gasa, Muns and their colleagues found that the optimal water-to-feed ratio for improving organic matter and gross energy digestibility varies according to the age of the animal. “In particular, the water-to-feed ratios that im- prove digestibility coefficients were lower for young growing pigs and higher for older finishing pigs,” the team states. “The data suggest that optimum efficiency is reached with a less water-diluted diet for young animals, when compared to old- er pigs.” Younger pigs have a smaller gut, and the larger vol- ume of a liquid diet can therefore make it difficult for them to consume the amount of dry matter (and therefore absorb enough nutrients) to result in optimal growth. Gasa notes that older pigs may produce more enzymes, boosting nutri- ent absorption. Their stomachs are also more developed, not just larger, making them inherently more able to absorb more nutrients/energy from liquid feed compared to young- er pigs with less-developed guts. Gasa concludes that with current technology (a feed kitchen, mixing tanks, pumps and pipes), “it is not clear that using liquid feeding across all stag- es would be beneficial. For the finishing and gestation stages it’s usually good, but at the nursery and lactation stages it might result in suboptimal intake.” When he was asked whether the speed of mixing and distributing liquid feed to the pigs could make a difference in pig performance at any age, Gasa said he doesn’t think so. “I don’t believe that short- ening mixing or distribution time (we would be talking about a difference of 10 or maybe 30 minutes) would affect digesti- bility and intake,” he says. “Fermented liquid feeding where the mixture ‘rests’ for about four to eight hours before being distributed is a different story. There can be some degrada- tion of animo acids with that type of system, which can affect pig performance.”

Wet/dry systems At AFBI, Muns has recently been involved in some trials with a newish type of wet/dry feeding system, but wet/dry is also used to refer to feeders that have a water nipple in the trough. “In our system at AFBI, which happens to be made by Spotmix, water and the compound feed are kept separate up to the point of delivery to the feeding trough where they mix to some extent,” he explains. “This somewhat homogenises a meal diet, but it doesn’t work as well with pellets. I would say it’s closer to liquid feeding because you can have different di- lution ratios that are similar to liquid systems. In their prelimi- nary analysis, Muns and his colleagues have found that feed conversion ratios with their system were similar to dry feed- ing, but feed intake and growth rate were higher. “I would say that about 40 per cent of the fattening houses in Northern Ireland use liquid feeding and wet/dry is only used at a few farms,” Muns reports. “I am not sure about the rest of Europe and beyond. Next in our research, we are going to see how much the amount of water added to the dry feed affects feed

conversion, feed intake and growth rate, especially in the nursery phase. Another question is whether it’s best to use liquid or wet/dry feeding the whole way from wean to finish- ing, or if it’s best to change from dry to wet at some point from a performance and economic perspective.”

In terms of advice to producers who need to make a decision about the type of feeding system to purchase, Muns says that if a farmer has co-products available, a liquid feeding system is the best way to go, particularly if it’s a finishing operation. With finishing pigs, there is more leeway, he notes, in terms of not having to be so precise with quality monitoring and adjustment of liquid-feed plus co-product compared to, say, sows in lactation. If there are no co-products available to a farmer however, Muns does recommend a wet/dry system. “You will then have no degradation of ingredients,” he says, “and you will have less maintenance and cleaning of the sys- tem compared to a liquid system (less risk of biofilm formin ). Also, if a farmer has the type of system we have been using at ABFI, it allows you to choose or swap between dry and wet/ dry feeding.”

▶ ALL ABOUT FEED | Volume 28, No. 8, 2020

One reason li- quid feed has become a popu- lar feeding sys- tem for pigs is the availability of liquid food in- dustry co-prod- ucts, which makes liquid feeding cheaper than other alternatives.



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