Short-Term Eating Preference of Beef Cattle Fed High Forage or High Grain Diets Supplemented with 3-Nitrooxypropanol

SIMPLE SUMMARY: 3-Nitrooxypropanol is an effective methane-mitigating feed additive. However, a decrease in feed intake is frequently observed in beef cattle fed a diet supplemented with 3-nitrooxypropanol. Thus, a study was conducted to determine the short-term preference of beef cattle offered diets supplemented with 3-nitrooxypropanol. When given a choice, the cattle initially showed less preference for a diet supplemented with 3-nitrooxypropanol, suggesting potential changes in organoleptic properties of the diet. However, the animals acclimatized to the supplemented diet rapidly such that there was no preference between a diet with and without 3-nitrooxypropanol within a week. Therefore, the change in the organoleptic properties of a diet supplemented with 3-nitrooxypropanol does not appear to be the main reason for reduced feed intake of beef cattle. ABSTRACT: Two experiments were conducted to examine eating preference of beef cattle for diets with or without the investigative enteric methane inhibitor 3-nitrooxypropanol (3-NOP). Nine beef steers were housed in individual stalls, each equipped with two feed bunks. The first experiment (Exp. 1) was conducted with a high forage diet and each animal received a diet without 3-NOP (CON) in one bunk and a diet with 3-NOP (dNOP) in the other bunk. The second study (Exp. 2) was conducted with the same animals about 6 months after Exp. 1 where a high grain diet without (CON) or with 3-NOP (dNOP) was offered. In Exp. 1, animals initially preferred CON compared with dNOP. Feed consumption from 0 to 3, 3 to 6, and 6 to 12 h after feeding was lower for dNOP compared with CON. However, dry matter intake (DMI) and feed consumption of dNOP gradually increased during Exp. 1 such that there was no preference between CON and dNOP on day 7. In Exp. 2, there was no preference for or against dNOP. Average DMI was greater for dNOP vs. CON, but interactions between diet and day for DMI and feed consumption rates indicated that daily preference between CON and dNOP was variable. In conclusion, beef steers initially detected a difference between CON and dNOP and selected in favor of CON rather than dNOP when they had not previously been exposed to 3-NOP. However, the animals rapidly acclimatized to a diet with 3-NOP (Exp. 1) and showed no eating preference between CON and dNOP within 7 days. This lack of preference was maintained throughout Exp. 2 when the same animals were fed a high grain diet.