Abstract
Liquid feed is susceptible to microbiological growth. Yeasts are said to cause sudden death in swine due to intestinal gas formation. As not all animals given high yeast content feed fall ill, growth and gas formation potential at body temperature were investigated as possible causally required properties. The best identification method for these environmental yeasts should be tested beforehand. Yeasts derived from liquid diets without (LD − S) and liquid diets with maize silage (LD + S) were examined biochemically (ID32C-test) and with MALDI-TOF with direct smear (DS) and an extraction method (EX). Growth temperature and gas-forming potential were measured. With MALDI-EX, most yeast isolates were identified: Candida krusei most often in LD − S, and C. lambica most often in LD + S, significantly more than in LD − S. Larger colonies, 58.75% of all yeast isolates, were formed at 25 °C rather than at 37 °C; 17.5% of all isolates did not grow at 37 °C at all. Most C. krusei isolates formed high gas amounts within 24 h, whereas none of the C. lambica, C. holmii and most other isolates did. The gas pressure formed by yeast isolates varied more than tenfold. Only a minority of the yeasts were able to produce gas at temperatures common in the pig gut.
Highlights
Yeasts, about 600 species of which are known [1], are ubiquitous in nature and can be found on feedstuffs [2]
Yeasts diagnosed twice in the same sample were not considered in the evaluation of the number of yeast species or species of yeast-like organisms that were found in the respective feed sample
MALDI-TOF; there was no reliable identification, it mucilaginosa could not be detected with MALDI-TOF; there was no reliable identification, was registered in the database
Summary
About 600 species of which are known [1], are ubiquitous in nature and can be found on feedstuffs [2]. Depending on the species or strain, as well as on the growth conditions like temperature, substrate and its aw-value (activity of water), yeasts are able to metabolize numerous sugars, starch, protein, amino acids or even fats, and lead to a loss of nutrients and energy in the feed [3,4,5]. In pig fattening, these energy losses in the feed are undesirable [4,5]. Feed hygiene related to yeast content was of special concern
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