category: feed additives
authors: bach, a., villalba, j.j. and ipharraguerre i.r.
book/journal:journal of animal science, 90:1015-1025
thirty-two crossbred lambs (bw = 31.2 ± 4.7 kg; 16 females, 16 males) housed in individual pens were used to investigate the relationship between nutrient supply and taste preferences in ruminants. experiment 1 determined whether an imbalanced cp supply would alter preferences for feeds containing flavors designed to elicit either umami (u) or a mixture (1/3:1/3:1/3) of umami, sweet, and bitter (m) tastes. lambs were randomly allocated to either a low (lp; 10.9% cp) or a high (hp; 20.4% cp) cp diet for 21 d. afterward, lambs were presented during 21 d with a choice of the same lp or hp diet unflavored (lpc or hpc, respectively) or flavored (0.1% as fed) with u (lpu or hpu, respectively) or m (lpm or hpm). experiment 2 determined the influence of cp status on preference for dietary cp, bitter taste, and sweet taste elicited by sucrose or a noncaloric sweetener. in test 1, sixteen lambs previously fed lp or hp for 42 d in exp. 1 could choose between the hp and lp diets. in test 2, the remaining 16 lambs from exp. 1 were offered a choice between unflavored lp or hp diets or the same diets flavored (0.066% as fed) with a bitter flavor. in test 3, the 16 lambs from test 1 were offered a choice between an unflavored diet (lp or hp) and the same diet flavored with sucrose (0.2%) or a noncaloric sweetener (0.066%). in exp. 1, when offered a choice, all lambs showed a preference (p < 0.05) for the unflavored diet except for lp lambs, who clearly preferred (p < 0.05) lpu (72% of total dmi) over lpc. however, preference for lpu progressively decreased (p < 0.05) as time of exposure to the choice increased. in exp. 2 (test 1), lambs previously fed lp progressively increased (p < 0.05) total dmi when presented with lp and hp, whereas consumption was constant for lambs previously fed hp and offered a choice of lp and hp diets. at the onset of test 2, lambs fed lp progressively reduced (p < 0.05) preference for the bitter flavor from 53 to 34%. in test 3, lambs previously fed lp diets consumed less (p < 0.05) sweetener- than sucrose-supplemented diet, whereas lambs previously offered hp diets consumed more sweetener- than sucrose-supplemented diet. in summary, protein-restricted lambs were able to differentiate and increase consumption of u-flavored feeds. however, this increase disappeared over time. these results indicate that lambs are able to sense dietary cp content and modulate short-term consumption of flavored feeds based on their nutrient requirements.