2.3. Animals, and experimental design

Thirty-two male Lacaune lambs with average weight 16 ± 0.99 kg and 45 d of age were used in the study. Lambs were randomly assigned to 1 of 4 treatments: T0, T1, T2, and T4, representing supplementation of N-CU at 0, 1, 2, and 4 mg/kg concentrate, respectively. The animals in each treatment were allocated in 4 pens with 2 lambs each (8 lambs/treatment). Knowing that every 1 g of N-CU powder contained 2 mg of curcumin, the doses were calculated and added to the concentrate. Because the adjuvant of the N-CU formulation was lactose, the amount of lactose was calculated and mixed in the concentrate of the treatments T0, T1, and T2. The doses used in the current study were defined based on the experiment of Jaguezeski et al. (2019).

According to the number of animals available for study, we tested 3 levels of nanostructured curcumin in the lamb diet. The effects of free curcumin on Lacaune lamb were already known at this stage (Molosse et al., 2019); this explains why a group of lambs receiving free curcumin was not included in this study (Jaguezeski et al., 2019).

Between 45 and 62 d of age, the experimental period, the animals received milk once a day (morning), a volume of 500 mL per day per animal. Water was provided ad libitum.

The base concentrate was formulated based on ground corn, soybean meal and premix (Table 1). The base concentrate was then supplemented with various concentrations of powdered N-CU. In the first week (7 d; adaptation period), each animal received 300 g of concentrate daily. This amount was increased to 400 g of concentrate per animal per day from d 8 to 17 of the experiment. The concentrate was offered to the animals twice a day (07:00, and 17:00), which was consumed in its entirety (100%) within 15 min after being made available; and in the sequence, the silage was offered.

Ingredients used to formulate the base concentrate of lambs (%, as-fed basis).

Corn silage was supplied ad libitum, divided into 3 times of the day its replacement in the feeder (07:15, 12:00, and 17:15). Between d 8 and 17, the amount of silage available per pen/repetition was measured; the excess silage is weighed. Based on this information, the amount of feed consumed was calculated.

Concentrate and silage samples were collected and the chemical composition was further analyzed. Results are presented in Table 2.

Chemical composition of diets, and antioxidant activity of diphenyl picrylhydrazyl in concentrates.

DM = dry matter; EE = ether extract; ADF = acid detergent fiber; NDF = neutral detergent fiber; IC₅₀ = half maximal inhibitory concentration.

^{a, b} Within a row, means without out a common superscript differs (P ≤ 0.05) or tends to differ (P ≤ 0.10) between treatments.

A total of 0.5 g of concentrate samples were used for preparation and obtaining the homogenate in order to determine antioxidant activity by elimination of radicals by diphenyl picrylhydrazyl (DPPH) according to methodology described in detail by Alba et al. (2019). Activity was presented by the half maximal inhibitory concentration (IC₅₀) value (μg/mL), defined as the concentration of antioxidant required to eliminate 50% of the DPPH present in the test solution. All tests were performed in triplicate.