PSVI-19 - Dose effect of a spice feed additive on ingestion and digestion in fattening bulls

Abstract: Palatability of feeds offered to fattening bulls depends on numerous factors including organoleptic properties. Modulating the palatability of the ration could alter the rate of ingestion, resulting in differences in the efficiency of mastication, rumination, and digestion. A trial was conducted to assess whether a spice feed additive (SFA) could modulate behavior and digestion in fattening bulls, and whether the dose would modify the response. Eight bulls (427±40kg BW) were distributed in a 4-period × 4-treatment Latin square design. Experimental periods lasted 21 days (d1-d21) and were separated by 7-day wash-out periods. The treatments consisted in a total mixed ration (in DM: 62% corn silage, 22% barley, 16% soybean meal, 1% minerals) without (CTRL) or with a SFA homogeneously included at 0.5g/d (SFA0.5), 1.0g/d (SFA1.0), or 2.0g/d (SFA2.0). It was individually adjusted (DMI=1.88% BW) and daily divided in 2 equal meals (8:30am and 4:15pm). Animals were weighted weekly, and feed conversion ratio (FCR) was calculated per period. Videos were recorded at d16 and d17 of experimental periods to calculate the duration of ingestion. Rumination behavior was determined from videos (2-min scan sample intervals) recorded from 7:00am to 7:00pm at d18. Ruminal pH was continuously recorded with boluses. At d21 ruminal content was sampled 3-h after the morning meal to score the abundance of fiber particles (from 0: “Liquid without fiber” to 3: “Very abundant fiber particles”). These scores were compared with a Fisher exact test (SAS). The effect of the SFA on the other variables was assessed through analysis of variance (proc GLIMMIX), and linear or quadratic regressions (proc REG, SAS). Duration of ingestion followed a quadratic model (P=0.061): it was faster with CTRL and SFA2.0 (46-min) than SFA0.5 (48-min) and SFA1.0 (52-min). The duration of pH decrease after the meal also fitted a quadratic model (P=0.064): it was maximum with CTRL (6.0-h) and minimum with SFA0.5 (3.7-h), and differed between CTRL and SFA0.5 (P=0.018) but not between SFA-containing rations. This different postprandial pH pattern might be explained by differences between treatments in the rumination kinetics between 9:00am and 2:00pm (P=0.077). Time ruminating was numerically higher with SFA-containing rations (CTRL: 22.9; SFA0.5: 24.2; SFA1.0:24.9; SFA2.0: 24.5% of observations). In the ruminal content, less fiber was observed with SFA0.5 (P=0.069), SFA1.0 (P=0.001), or SFA2.0 (P=0.041) compared to CTRL. Finally, although non-significant the FCR also followed a bell curve with maximum efficiency with SFA1.0. These results suggest that spices added to the ration might modify both ingestion and rumination, with possible consequences on digestion. Interestingly, the effect of the tested SFA was quadratic with optimal impact in fattening bulls at the dose 1.0g/d. Considering the sense of taste in cattle could be a promising way to modulate ruminal ecosystem and zootechnical performance.