To analyze digestibility, the diets were supplemented with chromic oxide as an inert marker. Fecal samples were collected from the fiberglass tanks through filtration (Whatman No. 2); they were freeze-dried and placed in plastic bags at −40 °C for analysis. Next, 65% HNO3 (Fulka, Muskegon, MI, USA) was mixed with 3 mL of 30% H2O2 (Merck, Darmstadt, Germany) and used for sample digestion in a microwave (Multiwave Go; Anton Paar, Graz, Austria). The total chromic oxide concentration in the samples was determined through inductively coupled plasma optical emission spectroscopy.
The apparent digestibility of dry matter of protein (ADp) was calculated as follows:
where d is the diet, f is the feces, C is the chromic oxide concentration, and NX is the nutrient concentration.
The apparent digestibility of dry matter of protein (ADp) was calculated as follows:
where d is the diet, f is the feces, C is the chromic oxide concentration, and NX is the nutrient concentration.
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