Though often referred to as a protein in the blood stream, a biomarker might be any molecule in body fluids, tissue or excreta that serves as an indicator for health, disease, exposure or effect. There are several overlapping definitions of biomarkers found in the literature.
One of the early sources defines a biomarker as “a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention.”
3 key applications
The identification and use of valid biomarkers substantially contributes to clinical research. Aside from validity, the ideal biomarker should possess the following features: safe and easy to measure, cost efficient to follow up, consistent across gender and modifiable due to treatment.
In practice, biomarkers can be used a) for diagnosing or staging a disease, b) for monitoring the response to a therapy or c) to indicate the exposure to environmental factors in living organisms. Thus, the descriptions under a) and b) are often summarized as “biomarkers of effects” and the latter as “biomarkers of exposure”. Selected biomarkers with high relevance for swine health and mycotoxin exposure are depicted in Table 1.
Feeding strategy investigations
In experimental feeding trials, biomarkers can be a powerful tool to explore the effect of an investigated feeding strategy and accordingly determine its potential for commercial application at an early stage. It also ideally serves to investigate mycotoxin exposure and effects. Many investigations using biomarker analysis require urine and/or feces sampling. Obtaining proper samples requires the use of specially equipped facilities, such as the BIOMIN Center for Applied Animal Nutrition (CAN) in Tulln, Austria – one of seven such sites globally in the Center for Applied Animal Nutrition network.
Table 1. Selected biomarkers in swine.
Adapted from Niewold (2015), Kataria (2012) and Baldwin (2011).
BIOMIN CAN Tulln
The site in Tulln comprises a feeding station, two rooms each equipped with 12 metabolic pens and one additional room fitted with four plastic coated slatted floor pens. Depending on the housing concept, criteria of trial and size of animals used, a maximum of 96 pigs can be housed in the two rooms with the metabolic pens. In the floor pens, the maximum capacity is 24 pigs up to a body weight of 30kg.
Figure 1 shows the principle set-up of a metabolic pen used at our CAN in Tulln. The pigs are able to move freely on a plastic coated slatted floor. Underneath the floor are two screens that will collect all the fecal material voided by the pig. Under the screens is a stainless steel tray that drains into the center and allows for the collection of all the urine produced during the day.
Figure 1. Metabolic pens used at the Center for Applied Animal Nutrition in Tulln. A) Front and side view with feeders and drinkers in the front door B) Inside view with slatted floor, collection area with screens and trays.
These metabolic pens allow for a large variety of state-of-the-art investigations in living organisms, including biomarker analysis, nutrient digestibility and nutrient retention. By collecting urine and feces separately, metabolism and excretion of molecules (e.g. mycotoxins and respective metabolites) can be studied. The impact of a feeding strategy on inflammation or oxidative stress can be monitored by analyzing the respective biofluid (blood, saliva, urine) or feces.
Knowing the amount of feed given each day and the nutrient composition of the feed, total nutrient intake can be calculated. The digestibility and the amount of nutrients retained in body tissues or lost nutrients can be calculated as well. Total nutrient excretion in feces and urine can be estimated and nutritional strategies evaluated.