Interpretive Summary: Toxicity of canola-derived glucosinolates in pigs fed resistant starch-based diets
By: Anne Wallace
Glucosinolates are naturally occurring chemicals found in plants which impart a bitterness in taste to deter herbivores. When consumed, glucosinolates form toxic byproducts that affect the liver and thyroid. Canola seed contains glucosinolates, although processing (e.g. heating) inactivates toxins. However, microorganisms in the hindgut of pigs may again create toxic byproducts from canola seed. Altering the hindgut microbial population of pigs by changing hindgut pH may be a solution to the aforementioned problem.
In this May 2020 Journal of Animal Science study, researchers hypothesized that high-amylose resistant cornstarch (HA-starch) would counter problems associated with toxic glucosinolate byproducts in a canola-based diet, in pigs. Resistant starch is highly indigestible and fermented by microbes in the hindgut of pigs, thus reducing hindgut pH.
Nursery pigs were fed one of four diets with different combinations of CPCC and HA-starch at 0% or 40%, respectively. The goal of this study was to determine if HA-starch had any benefit on the growth performance, thyroid hormone blood levels, glucosinolate degradation products, and organ weights of pigs fed a cold-pressed canola cake (CPCC) diet.
Results noted a reduced average daily gain (ADG) in pigs fed CPCC. Thyroid hormone blood levels were also decreased. Liver and kidney gland weights were increased, indicating metabolic stress. The addition of HA-starch to the CPCC diet increased thyroid hormone blood levels and reduced thyroid gland weight. Colon pH was also decreased, representative of increased hindgut fermentation from resistant starch.
Overall, the addition of HA-starch to a CPCC diet in nursery pigs was found to lessen the toxic impacts of glucosinolate byproducts on the thyroid. However, more in-depth studies to better understand the impacts of resistant starch on the gut, gut microbiota, and gut microbiota byproducts in the setting of a CPCC-based diet in pigs is warranted.