TUNEL (+) and fertility rates obtained from thawed samples of Red Villafranquina and Quail Castellana roosters, frozen without (Control) or with valine 10 mmol. Different letters (a,b; A,B) indicate significant differences between treatments (control or valine) within the same breed (P < 0.05; P < 0.01, respectively). Line over bars indicates significant differences between breeds. n = 40 (20 samples per bird). Abbreviations: TUNEL, terminal deoxynucleotidyl transferase dUTP nick end labeling; VF, Red Villafranquina; QC, Quail Castellana.