Effect of dose of thymol and supplemental flavours or camphor on palatability in a choice feedings study with piglets

Abstract

Thymol’s antimicrobial properties urged researchers to study its effect on animal performance and intestinal health in pigs. However, thymol has the characteristic sharp odor of thyme and a bitter, aromatic, and sometimes burning sensation which may elicit feeding aversions. The objectives in the current study were: (1) to determine the effect of dose of thymol and camphor on palatability and (2) to test the hypothesis that supplemental flavours or camphor, the latter as a known Transient Receptor Potential A1 blocker, could mitigate feed avoidance caused by thymol. Two analogous choice-feeding trials were conducted. Feed intake of the test diet was expressed as proportion of the total intake and tested by means of a one-sample Student’s t-test against a set value of 50%. The preference for feed supplemented with 125, 500, 1250 and 2000 mg/kg thymol was 53.7 ± 6.0% (P > 0.05), 47.5 ± 5.1% (P > 0.05), 36.8 ± 4.9% (P = 0.022), and 3.9 ± 7.9% (P = 0.005) respectively. When feed containing 2000 mg/kg thymol with either flavour A (containing intense sweeteners) or flavour B (containing the same intense sweeteners and a caramel aroma) was opposed against a control diet, the relative intake of the test diets was 19.9 ± 5.8% and 14.0 ± 4.9% (both P < 0.05) respectively. When animals were offered one of these test diets and a reference diet with 2000 mg/kg thymol, animals exhibited a preference for the feed with 2000 mg/kg thymol + flavour A, but not for the feed with 2000 mg/kg thymol + flavour B. Thus, supplemental flavours containing intense sweeteners partially overcame feed avoidance caused by thymol which was less pronounced when the caramel aroma was present. Exposure to camphor (50 and 200 mg/kg) did not improve feed preference for a diet containing 1250 mg/kg thymol. Thymol’s bitter taste might be largely responsible for the recorded feed refusal at high inclusion rates.    

Impact of sensory feed additives on feed intake, feed preferences, and growth of female piglets during the early postweaning period1

“…That the FA2 unfamiliar starter diet was preferred to the standard starter diet with no additive on the day of feed transition suggests that the FA2 has the ability to mask the change of feed and would be efficient to reduce the negative effect of feed neophobia and maintain feed intake during a sudden feed transition. Certain flavors and sensory additives have the ability to mask the negative properties of unpalatable ingredients, which results in increased feed intake and preferences for the flavoring diets in pigs (Baidoo et al, 1986;Tedò et al, 2008;Sulabo et al, 2010;Michiels et al, 2012). Roura et al (2007) also demonstrated the ability of certain aroma to mask the change of feed during a sudden feed transition.…”

“…Yet such positive effects were expected given that the FA1 contained an extract of Stevia rebaudiana, with a minimum of 90% steviol glycosides (i.e., stevioside), which are the glycosides responsible for the sweet taste of stevia. Sweet taste is very attractive for pigs (Baldwin, 1976;Glaser et al, 2000;Nofre et al, 2002) and some sensory additives based on sweeteners are effective to increase feed palatability (Wahlstrom et al, 1974;McLaughlin et al, 1983;Michiels et al, 2012). According to electrophysiological studies, however, pigs are less sensible to steviol glyco-sides than humans (Hellekant and Danilova, 1999).…”

“…Exposing the piglets to the feed additives through maternal milk during the suckling period by adding the additive directly in the diet of lactating sows might enable to improve growth performance and intake during the early growing period (Ilsley et al, 2003;Matysiak et al, 2012). Finally, the inclusion rate of the additive in the feed is of primary importance for the improvement of feed intake/ preferences in pigs (Jugl-Chizzola et al, 2006;Clouard et al, 2012;Michiels et al, 2012), which suggests that the effects of FA1, FA2, and FA3 could have been more pronounced if tested at different inclusion rates.…”

“…In pig production, sensory feed additives based on essential oils, aromatic herbs, and/or spices are commonly used in an attempt to improve feed palatability and zootechnical performance (feed intake and growth; Windisch et al, 2008;Franz et al, 2010;Jacela et al, 2010) and especially during sensitive/stressful periods such as weaning, environmental, or feed transitions during which feeding activity and growth can be severely impaired (Campbell, 1976;Dong and Pluske, 2007). Several studies have investigated the beneficial effects of feed supplementation with sensory additives on feed palatability, feed intake, and growth performance in pigs and reported contradictory results depending on the additive composition, inclusion rates, periods of exposure to the additive, or diet composition (e.g., Jugl-Chizzola et al, 2006;Seabolt et al, 2010;Clouard et al, 2012;Michiels et al, 2012).…”

Single components of botanicals and nature-identical compounds as a non-antibiotic strategy to ameliorate health status and improve performance in poultry and pigs

“…In fact, Boudry & Perrier (126) , using the ex vivo Ussing chamber technique, showed that thymol induces Cland HCO 3 secretion of epithelial intestinal cells via a nervous pathway. Thymol and carvacrol also seem to activate TRPA1, which plays a role in pain sensation (40) , and this could be the reason why, for example, these phenols sometimes affect feed intake when fed at high doses and are not encapsulated (141) .…”