Search

The objective of this study was to determine the effects of narasin on rumen fermentation of steers fed a high-forage diet. Thirty rumen-fistulated Nellore steers were assigned to a randomized completed block design, defined by initial BW. Steers were fed daily and diets were composed of 99% of coastcross haylage and 1% of concentrate, used as delivery vehicle for the narasin. The concentrate was offered separately, and the forage was offered after the total consumption of concentrate. The experimental diets were: N0 = concentrate without narasin; N13: inclusion of 13 ppm of narasin; and N20 = inclusion of 20 ppm of narasin. The trial lasted 140 days, divided on 5 periods of 28 days each. Rumen fluid was collected on days 0, 28, 56, 84, 112 and 140, starting 6 hours after feeding, in order to evaluate rumen pH and SCFA. Data were analyzed as repeated measures over time using the MIXED procedure of SAS and the LSMEANS option was used to generate individual means. Data obtained on d 0 were used as covariate. Orthogonal polynomials were determined by linear and quadratic effect. There was no treatment and day interaction for any of the parameters evaluated (P > 0.05). There was a quadratic effect on acetate (73.9, 72.6, and 72.6 mM/100mM; P < 0.01), propionate (13.9, 15.9, and 15.3 mM/100mM; P < 0.01), butyrate (9.1, 8.7, and 9.0 mM/100mM; P < 0.01), valerate (1.0, 0.9, and 1.0 mM/100mM; P = 0.01), and Ac:Pr ratio (5.3, 4.6, and 4.8; P < 0.01). The narasin inclusion linearly increased total SCFA (93.1, 98.9, and 104.4 mM; P < 0.01), whereas no effects were noted on rumen pH (6.69 ± 0.05; P = 0.23). Hence, the inclusion of 13 ppm of narasin increased propionate and decreased the Ac:Pr ratio. Key Words

Narasin is a coccidiostatic and antibacterial agent that may change rumen fermentation, improving ruminants performance. The objective of this trial was evaluate the effects of narasin inclusion on diets over the milk production and composition of ewes, and performance of their lambs. Thirty lactating ewes were allotted in a randomized complete block design, defined by body weight, offspring number and sex. Diets were formulated to be isonitrogenous (14% CP, DM basis), composed of 50% coastcross hay and 50% concentrate, fed once a day, ad libitum. The treatments were determined by no inclusion (N0) or inclusion of 13 ppm of narasin (N13). From the 2nd until the 10th week of lactation, DMI was measured, whereas in the same period, once a week, the ewes were separated from their lambs, and mechanically milked after intravenous administration of 10 IU of synthetic oxytocin. Three hours after the first milking, the ewes were milked again for milk production and composition evaluation. Data were analyzed as repeated measures over time using the MIXED procedure of SAS and the LSMEANS option was used to obtain the means. Narasin did not affect DMI (2.52 for N0 and 2.71 kg/d for N13 [SEM 0.10, P = 0.16]), however, it increased milk production (153.69 for N0 and 187.83 g/3h for N13 [SEM 12.43, P = 0.04]). Narasin supplementation decreased protein concentration (5.41 for N0 and 5.07% for N13 [SEM 0.09, P < 0.01]), but had no effect on fat, lactose and total solids composition (%, p > 0.05), or fat, protein, lactose and total solids production (g/3h, p > 0.05). In conclusion, narasin administration at 13 ppm improved the lactation performance in ewes offered a 50 % concentrate diet.

The aim of this study was to determine the effects of three additives (Narasin, Lasalocid and Virginiamycin) on rumen fermentation characteristics of steers fed high-forage diet. Thirty-two rumen-fistulated Nellore steers were assigned to a randomized completed block design, according to their initial BW. Steers were fed daily and diets were composed of 99% of coastcross haylage and 1% of concentrate, used as delivery vehicle for the additives. The concentrate and forage were offered separately, whereas the forage was offered after the entire consumption of the concentrate. The experimental diets consisted of: CON = Control; NAR: 13 ppm of narasin; LAS = 20 ppm of lasalocid; and VIR: 20 ppm of virginiamycin. The experimental period lasted 140 d, divided on 5 periods of 28 d each. Rumen fluid was collected on d 0, 28, 56, 84, 112 and 140, at 0, 6 and 12 hours after feeding and combined as a pool for SCFA analysis. Data were analyzed as repeated measures over time using the MIXED procedure of SAS and the LSMEANS option was used to generate individual means. Data obtained on d 0 were used as covariate. Orthogonal contrasts were determined to mean comparisons (C1: CON vs NAR, LAS, VIR; C2: NAR and LAS vs VIR; C3: NAR vs LAS). There was a treatment effect on total SCFA (87.13, 105.42, 88.64 and 90.35 mM/100mM; C1: P = 0.02; C2: 0.06; C3: P < 0.01), propionate (14.47, 15.74, 14,77 and 14,50 mM/100mM; C1: P = 0.04; C2: P = 0.01; C3: P < 0.01), and Ac:Pr ratio (5.19, 4.50, 5.05 and 5.23; C1: P < 0.01; C2: P < 0.01; C3: P < 0.01). Therefore, the inclusion of narasin increased propionate, total SCFA and decreased the Ac:Pr ratio compared to the other feed additives.