8. The feeding trial: Kau kau silage v commercial pellets

In this blog the feeding trial results are presented.

Two dietary treatments were compared.  The pigs were randomly allocated to two groups. The control group was fed the standard commercial diets for weaner, grower and finisher pigs used on the 400 sow Boroma commercial farm just down the road. The test pigs were fed the fermented sweet potato (kau kau) tuber silage combined with a protein mineral premix at 30% of the diet from 12 weeks of age to 15 weeks and 25% from 16 weeks until 23 weeks. 

We knew that the smaller pigs would struggle with silage feed intakes necessary to achieve the amino acid and energy intakes necessary to compete with the animals fed the commercial diets.  Since most feed is consumed by pigs more than 40 kg liveweight we wanted to see how these performed.  We were quite prepared to feed a commercial diet until at least ten weeks of age.  We could look more closely at the performance of the younger pigs later. In any case we had no choice because the repair of the kau kau mulcher delayed the start of the experiment until the pigs were 12 weeks old.

 

Feed for each pen weighed and fed by bucket.
B1 was a control group, fed by a white bucket.

Trial pigs about 14 weeks old

We provided Isidor with a feeding scale that increased the amount of feed offered each week. Staff weighed out the estimated amount of kau kau silage to be fed, mixed in the protein mineral balancer at 30% or 25% by weight of the silage depending on the age of the pigs and then distributed it to each pen according to a feeding chart for each pen.

The kau kau, premixed with the supplement, and the Boroma commercial diet were measured into the feed trough twice each day. Food not consumed by the time of the next feed was removed and weighed. We didn’t know exactly how much they would eat in the tropical Port Moresby climate. We were guided by intakes of Australian pigs so fed them according to a feeding scale based on energy intakes predicted by the Auspig pig growth computer model but were prepared to offer them more.

Five faecal samples were taken from each pen when the pigs were 20 weeks of age for faecal egg counts all with negative results. Pigs falling behind were assessed, temperatures taken, clinical signs recorded and treated if necessary. Dead pigs were weighed and measured.

Staff took a keen interest in the pigs and their performance. They were very impressed by how quickly the pigs grew. Miriam wrote in her weekly reports, 

“It is very surprising to see how much these pigs have grown. From my observation, I have seen that they have gained much weight and are very healthy. The second batch is catching up with the first batch.” They weren’t really, but they were growing very quickly by PNG standards. People were still talking about their performance 6 years later.

Of the 90 pigs that started the trial 84 finished.  Six pigs died, one from the control group and five from the treatment group.  Two of the pigs from the treatment group died while they were being fed the same pellet diet as the controls, in the first few weeks of the trial. Three died while they were being fed the silage diet, but these numbers are too small to mean anything statistically.

Fig1. The pigs fed pellets grew faster than those fed silage.

The pigs in both groups grew well for pigs raised in a hot climate.  They reached 90-95 kg in 170 days for an average daily gain of 529 and 560 grams for the silage fed pigs and the pellet fed pigs respectively, (Figure one). The weight difference at 170 days of 5.6 kg was statistically significant, P<0.01).

The feed intakes of the pigs fed the silage were acceptable but they failed to both match the energy intakes of the pigs fed commercial pellets and reach the intakes required to meet the expected digestible energy (DE) targets, (Figures two and three). It is apparent from about 80 -105 days that staff struggled to match the feed provided to each pen with the actual intakes. The silage diets were fed from about 85 days of age but at that stage both diets were being fed to excess. Any leftover food was removed without being weighed and it took staff several weeks to get the feeding levels “right.”  

Fig 2.  The pigs fed pellets consumed more

energy than the pigs fed silage.

  

Fig 3. The pigs fed silage couldn't eat enough

The silage fed pigs could not consume enough feed to reach the predicted amount, (Figure four).   It points to the difficulty of achieving the intakes required for high level growth performance in hot humid climates. It wasn't that the silage wasn't good to eat, their stomachs just weren't big enough. In figure four it is evident that staff tried to feed the pigs to the feeding scale but, after it was pointed out that the pigs were not consuming the feed but wasting it, staff fed to appetite.

Fig 4.  The pigs fed pellets couldn't consume as

 much feed as we thought but they were closer to the

prediction than the pigs fed silage

The data show that pigs fed a kau kau diet supplemented with a protein-mineral balancer, grew a little less quickly than pigs fed conventional diets.  Nonetheless they grew well enough to suggest that kau kau could form the foundation of a diet that villagers could feed their pigs. 

The achieved growth rate for the trial pigs would be cost competitive with pigs fed conventional diets anywhere.  The next step was to test the concept in a small purpose-built pig house. See my next blog (#9) for that chapter.