*2.1. Experimental Design*

2.1.1. Experiment In Vivo

Animals and Diets

A total of twenty-four Danbred × Duroc barrows (body weight 10.8 ± 0.8 kg) at the age of 40 days were randomly divided into four dietary treatment groups, each fed a cereal-based diet (Table 1) supplemented with Zn and fibre from different sources during a four-week feeding period. The experimental diets consisted of cellulose (Lonocel, Cargill Poland Ltd., Kiszkowo, Poland) and zinc sulphate monohydrate for control treatment (C), cellulose and zinc glycinate (Glycinoplex-Zn, Phytobiotics Futterzusatzstoffe GmbH, Eltville, Germany) for ZnGly treatment, and potato fibre (Potex, Lyckeby Starch, Kristianstad, Sweden) with ZnSO4 for PF treatment or potato fibre with zinc glycinate for PF + ZnGly treatment. All experimental diets were prepared to contain a total of 150 mg Zn/kg and up to 50 g/kg of total crude fibre content in the complete diet (as-fed basis) from different Zn and fibre sources. Chemical composition of both dietary fibre preparations was published in our previous study [24]. The analyzed total content of Zn and crude fibre (CF) in the experimental diets were 141.9 mg Zn/kg and 42 g/kg of CF for C treatment, 142.2 mg Zn/kg and 40 g/kg of CF for the ZnGly, 141.1 mg Zn/kg and 40 g/kg of CF for PF, and 142.2 mg Zn/kg and 40 g/kg of CF for PF + ZnGly treatments. The ingredients and chemical composition of the cereal-based diets are shown in Table 1.


**Table 1.** Ingredients and chemical composition of the cereal-based diets.

1 C—the diets containing cellulose fibre, PF—the diets containing potato fibre. 2 Provided per kg of diet: 14,680 IU vitamin A, 1835 IU vitamin D3, 138 mg vitamin E, 4.59 vitamin K3, 2.94 mg vitamin B1, 7.34 mg vitamin B2, 4.40 mg vitamin B6, 44.0 μg vitamin B12, 36.7 mg nicotinic acid, 16.0 mg calcium D-pantothenate, 1.47 mg folic acid, 147 μg biotin, 228 mg Fe, 73.4 mg Mn, 156 mg Cu, 631 μg I, 411 μg Se.
