PSX-27 Effects of narasin supplementation frequency on lamb ruminal fermentation

Abstract This study evaluated the frequency of narasin supplementation on ruminal fermentation in lambs. Four male lambs (castrated and cannulated in the rumen) were used in a 4 x 4 Latin square experimental design. The experimental diets consisted of 95% coastcross hay (16% CP) and 5% ground corn (DM basis), used as the delivery vehicle for the narasin. The diet was fed daily. The treatments were: C (no additives), N24: narasin offered every 24 hours at 13 ppm; N48: narasin offered every 48 hours, being 26 ppm offered on the first day and ground corn without narasin on the second day; N72: narasin offered every 72 hours, being 39 ppm offered on the first day and ground corn without narasin on the second and third days. The trial lasted 4 periods of 36 days each. Between the 31st to 36th days of each period, the rumen fluid was collected (hours 0; 6 and 12). All data were analyzed using the MIXED procedure of SAS and the treatments were compared through the Tukey test at 5% probability. There was no effect at the molar concentration of acetate (76.25 ± 1.22 mM/100mM), butyrate (4.9 ± 0.59 mM/100mM), ammonia (15.17 ± 2.03 mg/dl) and pH (6.36 ± 0.13). There was an effect of the molar concentration of propionate (C = 15.88b; N24 = 17.35a; N48 = 16.91a; N72 = 16.57ab mM/100mM; P < 0.01), acetate:propionate ratio (C = 4.86; a N24 = 4.38 b; N48 = 4.53b; N72 = 4.66ab; P < 0.01) and the total SCFA (C = 88.96b; N24 = 107.43 a; N48 = 100.53a; N72 = 84.62b mM; P < 0.01). In conclusion, the daily supply of narasin and every 48 hours positively affected ruminal fermentation parameters in lambs, but this effect decreased when used every 72 hours.