A nutritional supplement composed of serum-derived bovine protein concentrate containing high levels of immunoglobulins (Ig), particularly IgG, with the potential to improve nutritional status. Upon oral administration of SBI, the Ig promotes gastrointestinal (GI) health by improving the composition of the GI microflora, enhancing digestive processes, and increasing gut barrier integrity and function. SBI may also improve immune function, maintain immune homeostasis, bind to and neutralize bacterial toxins and antigens, and decrease intestinal inflammation. Altogether, this may enhance the functioning of the GI tract, improve both the digestion and absorption of nutrients, and increase weight gain.