Zinc (Zn) is a micromineral with structural, catalytic, and regulatory functions in muscle tissue. It improves growth in ruminants because it modulates energy metabolism. The objective of this study was to evaluate the effect of Zn methionine (Zn-Met) and (or) Zn oxide (ZnO) addition in the diet of Katahdin × Dorper lambs on performance, carcass traits, and meat quality characteristics. Forty non-castrated Katahdin × Dorper F1 lambs were randomly assigned to the following experimental groups: (1) Zn-Met (65 ppm), (2) ZnO (65 ppm), (3) Zn-Met + ZnO (32.5 + 32.5 ppm), and (4) basal diet (BD, without Zn). The duration of experiment was 93 d. Treatment Zn-Met + ZnO vs. control improved (P ≤ 0.05) average daily gain (ADG) and feed conversion (FC); ZnO increased leg perimeter and decreased visceral fat. Intramuscular fat (IMF) and marbling of chop with Zn-Met + ZnO vs. control were higher (P ≤ 0.05). Oxidative stability of cooked meat was delayed (P ≤ 0.05) with Zn-Met + ZnO. Myristic acid was lowest (P ≤ 0.05) with ZnO, and arachidonic acid was higher (P ≤ 0.05) in Zn-Met. Therefore, compared with the BD, Zn-Met + ZnO improved the ADG and FC, decreased the shear force, and delayed the stability oxidative in cooked meat; Zn-Met and ZnO increased the IMF and marbling; additionally, Zn-Met increased arachidonic acid and ZnO decreased visceral fat and myristic acid.

The effect of breed and dietary avocado level on the total apparent digestibility (RAD) and balance of nitrogen (N) energy, in young pigs, was studied. Four Pelón Mexicano (PM) and four Yorkshire × Landrace (Y×L) barrow male pigs (39.2 kg average inital liveweight) distributed in two groups...

Free amino acids (AA) appear to be absorbed faster than protein-bound AA (PB-AA). We conducted an experiment to assess the effect of feeding pigs with a partially free (F-AA) or totally PB-AA diet on expression of selected genes and performance of pigs. The expression of cationic AA transporters b(0,+) and CAT-1 in intestinal mucosa, liver, and longissimus (LM) and semitendinosus (SM) muscles, as well as that of myosin in LM and SM, was analyzed. Twelve pigs (31.7 ± 2.7 kg) were used. The F-AA diet was based on wheat, supplemented with 0.59% L-Lys, 0.33% L-Thr, and 0.10% DL-Met. The PB-AA diet was formulated with wheat-soybean meal. Average daily feed intake was 1.53 kg per pig. The expression of b(0,+) and CAT-1 was analyzed in jejunal and ileal mucosa, liver, LM, and SM; myosin expression was also analyzed in both muscles. Pigs fed the PB-AA diet tended to have higher weight gain and feed efficiency (P < 0.10), and had thinner back fat (P = 0.02). The expression of b(0,+) was higher (P < 0.01) in jejunum but lower (P < 0.01) in the liver of pigs fed the F-AA diet; CAT-1 tended to be lower in liver but higher in LM of PB-AA pigs. Myosin expression was not affected. Intestinal AA absorption was faster in pigs fed the F-AA diet, but AA uptake by the liver seemed to be faster in pigs fed the PB-AA. Performance and expression of AA transporters and myosin suggest that the dietary content of free or protein-bound AA does not affect their availability for protein synthesis in pigs.