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Doktorsavhandling, 2018

Impact of fermentation on the nutritive value of cassava root pulp and soybean pulp as a feed for growing pigs in Lao PDR

Taysayavong, Lotchana

Sammanfattning

This thesis evaluated the impact of fermentation on the nutritive value of cassava root pulp (CRP) and soybean pulp (SBP) as feed for growing pigs. The evaluation was based on four studies (two fermentation and two animal studies). In these, the chemical composition of CRP aerobically fermented with four different yeast sources was evaluated; the digestibility, nitrogen balance, gut environment and visceral organ size were studied in growing Moo Lath and Large White pigs fed unfermented and fermented CRP and SBP; CRP and SBP were anaerobically fermented (ensiled) with or without rice bran; and the digestibility and nitrogen balance of the ensiled products was studied in growing Large White pigs. Crude protein, true protein, neutral detergent fibre (NDF), starch and ash content in fermented CRP differed between yeast sources. Crude protein and ash content increased and starch content decreased with days of fermentation for all yeast sources and all levels of nitrogen addition (1.25, 2.5 %). The greatest increase in crude protein and ash content during fermentation was observed for Lao alcohol yeast. The greatest decrease in starch content was also found for Lao alcohol yeast, followed by Schwanniomyces occidentalis, Saccharomyces cerevisiae and Rhodotorula toruloides. Organic matter and crude protein digestibility was higher for diets with SBP than for diets with CRP, and did not differ between pig breeds. Nitrogen retention, expressed as a proportion of nitrogen digested, was similar between breeds and was highest for fermented CRP and lowest for unfermented CRP. There were no effects of diet on gut environment or visceral organ size. For both CRP and SRP, the pH decreased with days of ensiling and was elevated by inclusion of rice bran. Dry matter (DM) content increased with days of ensiling and with increasing inclusion of rice bran. In CRP, the crude protein content increased with days of ensiling, while there was a decrease in crude protein content in SBP. Increasing inclusion of rice bran elevated the crude protein content in CRP, but reduced it in SBP. Increasing inclusion of rice bran raised the ammonia-nitrogen (NH3-N) content in both CRP and SBP, and the content within pulp source remained elevated during ensiling. Ensiling CRP and SBP with rice bran produced in a feed product that was well digested and utilised in growing Large White pigs, but with differences in palatability. Ensiling both forms of pulp with inclusion of rice bran (10% for CRP and 20% for SBP) improved the digestibility of both organic matter and crude protein, suggesting synergistic effects in the porcine gastrointestinal tract.

Nyckelord

smallholder farmer, digestibility, ensiling, rice bran, yeast

Publicerad i

Acta Universitatis Agriculturae Sueciae
2018, nummer: 2018:67
ISBN: 978-91-7760-274-3, eISBN: 978-91-7760-275-0
Utgivare: Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences