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Context Ionophores improve rumen fermentation efficiency, average daily gain (ADG) and feed efficiency. However, the effects of providing ionophores to grazing animals are extremely variable, primarily due to infrequent supplement intake. Aim This study aimed to evaluate the effect of frequency of narasin intake on ruminal fermentation, nutrient digestibility and growth of lambs. Methods In Experiment I (metabolism assay), four rumen-cannulated wethers (1/2 Dorper × 1/2 Santa Inês) were assigned to a 4 × 4 Latin square design. The four treatments included a control, where animals were fed a diet without ionophore, and the following three treatments where animals were fed narasin at different intervals: 13 mg/kg of narasin every 24 h (N24), 26 mg/kg of narasin every 48 h (N48) and 39 mg/kg of narasin every 72 h (N72). All animals were fed with 95% Tifton-85 hay and 5% ground corn that was used as a vehicle for narasin. In Experiment II, 44 lambs (1/2 Dorper × 1/2 Santa Inês; 33.3 ± 0.5 kg (mean ± s.e.m.) and 180.5 ± 8 days of age) were used in a randomised complete-block design to assess performance. All treatments and management were similar to those in Experiment I. Key results Experiment I, dry-matter intake and apparent digestibility of nutrients were not affected by the treatments. The treatments N24 and N48 increased (P

Two experiments were designed to evaluate the impacts of supplementing lasalocid (LAS), narasin (NAR), or virginiamycin (VRM) on rumen fermentation parameters, apparent nutrient digestibility, and blood parameters (Exp. 1), as well as feed intake and performance (Exp. 2) of Nellore cattle consuming a forage-based diet. In Exp. 1, 32 rumen-fistulated Nellore steers (initial shrunk body weight [BW] = 355 ± 4.4 kg) were assigned to a randomized complete block design. Within block, animals were randomly assigned to one of four treatments: 1) forage-based diet without feed additives (CON), 2) CON diet plus 13 mg/kg of dry matter (DM) of NAR, 3) CON diet plus 20 mg/kg of DM of sodium LAS, or 4) CON diet plus 20 mg/kg of DM of VRM. No treatment effects were detected (P ≥ 0.32) for intake and apparent digestibility of nutrients. Steers fed NAR had the lowest (P ≤ 0.01) molar proportion of acetate on day 28, 56, and 112 vs. CON, LAS, and VRM steers, whereas acetate did not differ (P ≥ 0.25) between LAS, VRM, and CON steers from day 28 to 84. On day 112, steers fed LAS had a lower (P < 0.02) molar proportion of acetate vs. VRM and CON, whereas it did not differ between CON and VRM (P > 0.33). Steers receiving NAR had a greater (P ≤ 0.04) ruminal propionate vs. CON, LAS, and VRM, whereas LAS steers had greater (P < 0.04) propionate vs. CON and VRM steers on day 28 and 112, and it did not differ (P > 0.22) between CON and VRM. In Exp. 2, 160 Nellore bulls were blocked by initial shrunk BW (212 ± 3.1 kg) in a 140-d feedlot trial. Diets contained the same treatments used in Exp. 1. Bulls fed NAR had greater (P < 0.02) average daily gain (ADG) vs. CON and VRM, and similar (P = 0.17) ADG between NAR and LAS, whereas ADG did not differ (P > 0.28) between LAS, VRM, and CON bulls. A treatment effect was detected (P = 0.03) for dry matter intake, being greater in NAR vs. CON, LAS, and VRM bulls, and similar (P > 0.48) between CON, LAS, and VRM bulls. A tendency was detected (P = 0.09) for feed efficiency, which was greater (P < 0.02) in NAR bulls vs. CON and VRM, and similar (P = 0.36) between NAR and LAS bulls. From day 112 to 140, bulls receiving NAR were heavier (P < 0.03) vs. CON, LAS, and VRM bulls, but no differences were observed (P > 0.51) between CON, LAS, and VRM bulls. Collectively, ruminal fermentation profile and intake were impacted by NAR supplementation, which partially contributed to the enhanced performance of Nellore bulls receiving a forage-based diet.

This study aimed to compare the effects of the feed additives lasalocid, narasin and virginiamycin to cattle fed high-forage diet. The hypothesis was that the inclusion of these additives would improve nutrient digestibility, change rumen fermentation and, increase the performance of beef cattle fed high-forage diet. Two experiments were designed to evaluate the effects of lasalocid, narasin, and virginiamycin on apparent total tract nutrient digestibility, rumen fermentation characteristics, blood parameters, and performance of Bos indicus cattle fed high-forage diet. In Exp. 1, 32 rumen-fistulated Nellore steers (initial shrunk BW = 355 ± 4.4 kg) were assigned to a randomized complete block design (n = 8), according to their initial shrunk BW. Steers were fed daily and diets were composed of 99% of coastcross haylage and 1% of concentrate, used as a delivery vehicle for the additives. The experimental diets consisted of 1) forage-based diet without feed additives (CON); 2) 13 mg/kg DM of narasin (NAR); 3) 20 mg/kg DM of lasalocid (LAS); and 4) 20 mg/kg DM of virginiamycin (VM). The experimental period lasted 140 d, divided into 5 periods of 28 d each. The inclusion of feed additives did not affect the DMI (P = 0.46), consequently, did not affect the nutrients intake (P > 0.05). In addition, there was no difference in nutrient digestibility among diets (P > 0.05). There was an interaction between treatment x day (P < 0.01) for total SCFA, acetate, propionate, and acetate:propionate (A:P) ratio. Animals offered NAR had the greatest total SCFA values on days 84 and 112 (P < 0.05), whereas acetate concentration was lowest to NAR on days 28, 56, 112 (P < 0.05), and lower on day 140 in relation to CON and LAS(P < 0.05). The treatment NAR had the greatest propionate and lowest A:P ratio values on days 28, 56, 112 and 140 when compared to other treatments(P < 0.05). In Exp. 2, 160 Nellore yearling bulls were blocked (n = 10) by initial shrunk BW (212 ± 3.1 kg) in a 140-d feedlot trial. Bulls were fed daily and diets were composed of 96% of coastcross haylage and 4% of concentrate, used as a delivery vehicle for the additives. The treatment NAR had a greater ADG (P = 0.04) than CON and VM and was similar to the LAS. In turn, the animals that received LAS presented a similar ADG to those of the other treatments. The gain:feed (G:F) was greater (P = 0.05) for NAR than CON and VM. Besides, LAS supplementation increased (P = 0.05) the G:F compared with CON, with no difference compared to VM. Consequently, the treatment NAR had the greatest final BW (P = 0.03) than others. In conclusion, NAR improves rumen parameters and performance of yearling bulls fed high-forage diets and LAS improves feed efficiency. Este estudo teve como objetivo comparar os efeitos dos aditivos alimentares lasalocida, narasina e virginiamicina para bovinos alimentados com dietas de alta forragem. A hipótese foi de que a inclusão desses aditivos melhoraria a digestibilidade dos nutrientes, alteraria a fermentação ruminal e melhoraria o desempenho de bovinos de corte alimentados com dietas de alta forragem. Foram delineados dois experimentos para avaliar os efeitos das moléculas lasalocida, narasina e virginiamicina sobre a digestibilidade aparente do trato total, parâmetros de fermentação ruminal, sanguíneos e desempenho de bovinos Nelore (Bos indicus) alimentados com dieta de alto volumoso. No experimento 1, 32 novilhos Nelore providos de cânula ruminal (peso corporal em jejum = 355 ± 4,4 kg) foram aleatorizados em blocos (n = 8), de acordo com seu peso corporal em jejum. Os novilhos foram alimentados diariamente e as dietas eram compostas de 99% de pré-secado de Coastcross e 1% de concentrado, usado como veículo de fornecimento dos aditivos. As dietas experimentais consistiam em 1) dieta baseada em forragem sem aditivos (CON); 2) 13 mg/kg de MS de narasina (NAR); 3) 20 mg/kg de MS de lasalocida e 4) 20 mg/kg de MS de virginiamicina (VM). O período experimental durou 140 dias, divididos em 5 períodos de 28 dias cada. A inclusão dos aditivos não afetou o CMS (P = 0,46), consequentemente, não afetou o consumo de nutrientes (P > 0,05). Além disso, não houve diferença na digestibilidade dos nutrientes entre as dietas (P > 0,05). Houve uma interação tratamento x dia (P < 0,01) para AGCC, acetato, propionato e a taxa acetato:propionato (A:P). Os animais que consumiram NAR tiveram os maiores valores de AGCC nos dias 84 e 112 (P < 0,05), enquanto as concentrações de acetato foram as menores para NAR nos dias 28, 56, 112 (P < 0,05), e menor no dia 140 em relação ao CON e LAS (P < 0,05). O tratamento NAR teve o maior valor de propionato e menor A:P nos dias 28, 56, 112 e 140 quando comparado com os outros tratamentos (P < 0,05). No experimento 2, 160 novilhos Nelore foram blocados (n = 10) pelo peso inicial em jejum (212 ± 3,1 kg) em um confinamento de 140 dias de duração. Os novilhos foram alimentados diariamente e as dietas foram compostas de 96% de pré-secado de Coastcross e 4% de concentrado, usados como veículo de fornecimento para os aditivos. O tratamento NAR teve o maior GMD (P = 0,04) do que CON e VM e foi similar para LAS. Por outro lado, os animais que receberam LAS apresentaram um GMD similar a estes outros tratamentos. A eficiência alimentar (GMD/CMS) foi maior (P = 0,05) para NAR em comparação ao grupo CON e VM. Além disso, o fornecimento de LAS aumentou (P = 0,05) a eficiência alimentar comparado ao CON, com nenhuma diferença comparado a VM. Consequentemente, o tratamento NAR teve o maior peso final (P = 0,03) do que os outros tratamentos. Em conclusão, NAR melhorou os parâmetros e desempenho de novilhos alimentados com dietas de alta forragem e LAS melhorou a eficiência alimentar.

Made available in DSpace on 2021-06-25T10:10:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) This study investigated the effects of growth rates and compensatory growth on puberty attainment in Nellore heifers. Nellore heifers (n = 120), weaned at 8 ± 0.75 mo of age, were blocked by sire and BW (180 ± 8.6 kg) and assigned randomly to receive 1 of 4 treatments over a 10-mo period. Treatments included ad libitum feeding (high gain, HG), feed intake to gain 0.6 kg/d (medium gain, MG), restricted feeding (0.2 kg/d) for 4 mo followed by ad libitum feeding for 6 mo (compensatory gain, CG), and alternating periods of ad libitum and restricted feeding for 2 mo each throughout the trial (alternated CG, ACG). Puberty was assessed weekly by transrectal ultrasonography. Blood samples were collected at 8, 11, and 18 mo of age and at puberty to determine circulating concentrations of leptin. At 18 mo of age, nonpubertal heifers were treated with a puberty induction protocol using an intravaginal progestin device. There was no treatment effect (P = 0.17) on the percentage of heifers pubertal by 18 mo of age (HG: 66, MG: 40, CG: 58, and ACG: 52%), BW at puberty, and age at puberty. However, HG heifers had higher ADG (P < 0.01), dry matter intake (P < 0.01), and leptin concentrations (P = 0.03) than heifers from other groups. The response to the puberty induction protocol was similar (P = 0.90) among treatments. Regarding sire effects (genetic effects), there was an effect (P = 0.03) on the percentage of heifers pubertal by 18 mo of age and a tendency (P = 0.07) of sire effect in response to the puberty induction protocol. Compensatory growth appears to be an effective managerial approach to decrease feeding costs and stimulate puberty in Nellore heifers. Department of Nutrition and Animal Production College of Veterinary and Animal Science University of São Paulo, Duque de Caxias North Avenue, n 225 Department of Animal Science Federal University of Amazonas, Macurany Avenue, Jacareacanga Department of Animal Science Texas A&M University, 2471 TAMU Department of Animal Science College of Agriculture “Luiz de Queiroz” University of São Paulo, Pádua Dias Avenue, n 11, PO Box 09 College of Veterinary Medicine São Paulo State University (UNESP) College of Veterinary Medicine São Paulo State University (UNESP)

Narasin is an antibacterial agent that may change rumen fermentation. Two experiments were proposed to evaluate the efficiency of narasin inclusion for lambs fed a diet containing high amounts of ground flint corn. Thirty rumen-cannulated wethers were used to evaluate nutrient digestibility, nitrogen balance, and rumen metabolism (Exp. 1); and forty-five lambs were used to evaluate performance (Exp. 2) of animals fed with narasin for high flint corn diets. The experimental diets were: control or basal diet without additives (C); 25 mg of monensin kg−1 of dry matter (DM) (M); and inclusion of 5 (N5), 10 (N10), and 15 (N15) mg of narasin kg−1 of DM. The statistical analyses were performed using the MIXED procedure of SAS. Monensin increased DM digestibility compared to C ( p = 0.01) and increasing doses of narasin linearly increased DM digestibility ( p < 0.01). There was a quadratic effect ( p = 0.10) for molar proportion of acetate peaking at N15. Monensin inclusion increased ( p = 0.07) propionate compared to C; however, it did not differ from narasin. The increasing levels of narasin linearly decreased the total volatile fatty acids concentration in the rumen ( p = 0.02). Monensin and C showed a similar performance. The increasing levels of narasin linearly increased ( p ≤ 0.04) average daily gain and feed efficiency. Monensin and narasin changed rumen fermentation and improved overall nutrient digestibility. However, lambs that received narasin showed improved performance when compared with animals that received M.

Two experiments were proposed to evaluate the addition of monensin for lambs fed diets containing a high level of mature ground flint corn. The experimental diets were as follows: no inclusion of monensin (M0) and inclusion of 8 (M8), 16 (M16) and 24 mg kg–1 of monensin (M24). In experiment 1, eight cannulated wethers were divided into a double 4 × 4 Latin square experimental design to evaluate nutrient digestibility, plasma parameters and rumen fermentation. The experiment lasted 112 days, divided into four periods of 28 days each. In experiment 2, ninety-two lambs were used in a randomized block design to evaluate the performance over 56 days. In experiment 1, doses of monensin had no effect on nutrient intake (p ≥ 0.07) and digestibility (p ≥ 0.09). There was a quadratic effect for acetate molar proportion (p = 0.01), acetate to propionate ratio (p = 0.04) and rumen pH (p < 0.01). However, there was no effect on the molar proportion of propionate and butyrate. The monensin decreased linearly the total SCFA concentration (p < 0.01). The inclusion of monensin increased glucose (p < 0.01) and decreased lactate concentration in plasma (p = 0.05). In experiment 2, monensin decreased dry matter intake (p = 0.04). However, there was a quadratic effect for average daily gain (p = 0.03) and feed efficiency (p < 0.01), with the greatest values observed for the M8 diet. Thus, the inclusion of 8 mg kg–1 of dry matter diet (DM) improves ruminal fermentation and plasma parameters, resulting in greater growth performance in lambs.

The aim of the present study was to evaluate the inclusion of narasin, salinomycin, or flavomycin for 140 d on ruminal fermentation parameters, apparent nutrient digestibility, and performance of Nellore cattle offered a forage-based diet. In experiment 1, 32 rumen-cannulated Bos indicus Nellore steers [initial body weight (BW) = 220 ± 12.6 kg] were assigned to individual pens in a randomized complete block design according to their initial shrunk BW. Within block, animals were randomly assigned to 1 of 4 treatments: (1) forage-based diet without feed additives (CON; n = 8), (2) CON diet plus 13 ppm of narasin (NAR; n = 8), (3) CON diet plus 20 ppm of salinomycin (SAL; n = 8), or (4) CON diet plus 3 ppm of flavomycin (FLA; n = 8). The experimental period lasted 140 d and was divided into 5 periods of 28 d each. The inclusion of feed additives did not impact (P ≥ 0.17) dry matter intake (DMI), nutrient intake, and apparent total tract digestibility of nutrients. Nonetheless, steers fed NAR had lower (P < 0.01) molar proportion of acetate compared with CON, SAL, and FLA steers, whereas ruminal acetate tended to be greater (P < 0.09) for SAL vs. CON and FLA, but did not differ (P = 0.68) between CON vs. FLA steers. Ruminal propionate was the highest (P < 0.01) for steers fed NAR and did not differ (P > 0.20) between CON, SAL, and FLA. Consequently, NAR steers had the lowest (P < 0.01) Ac:Pr ratio, whereas Ac:Pr did not differ (P > 0.18) among CON, SAL, and FLA. Total volatile fatty acids were greater (P < 0.04) for NAR and CON vs. SAL and FLA, but did not differ (P > 0.67) among NAR vs. CON and SAL vs. FLA. In experiment 2, 164 Nellore bulls (initial shrunk BW = 299 ± 2.5 kg) were assigned to feedlot pens for 140 d in a randomized complete block design. Within block (n = 10), animals were randomly assigned to the same treatments used in experiment 1. Average daily gain was greater (P < 0.01) in NAR vs. CON, SAL, and FLA bulls, and did not differ (P > 0.12) between CON, SAL, and FLA bulls. Bulls fed NAR had greater (P < 0.02) DMI (as kg/d or % BW) and final shrunk BW compared with CON, SAL, and FLA bulls, whereas DMI and final shrunk BW did not differ (P > 0.26) between CON, SAL, and FLA bulls. Feed efficiency, however, was not impacted (P = 0.51) by any feed additives used herein. Collectively, narasin was the only feed additive that benefited performance and ruminal fermentation of Nellore animals fed a forage-based diet.

The changes promoted by feed additives in ruminal fermentation, especially increasing the availability of propionate, can improve the energy balance of an animal, which is of great importance in the lactation period. This trial aimed to evaluate the inclusion of narasin in the diet of lactating ewes on milk yield, composition, dry matter intake (DMI), and plasma metabolites of the ewes and growth rate of lambs. Thirty-two lactating ewes (59.0 ± 2.42 kg) were assigned to a randomized complete block design. The experimental diets contained 500 g/kg of dry matter (DM) of coast cross (Cynodon dactylon (L.) Pers) hay and 500 g/kg DM of concentrate, and the treatments were: N0—no narasin inclusion; N13—inclusion of 13 mg of narasin/kg DM. Once a week, from week 2 to 10 of lactation, ewes were separated from their lambs, injected with oxytocin, and milked mechanically to empty the udder. After 3 h, the milk production was recorded, using the same procedure, and sampled to evaluate the composition. The blood samples were taken weekly, 4 h after feeding. The average daily gain (ADG) and starter DMI of the lambs were evaluated weekly from week 2 to 12 of age. The inclusion of narasin did not affect (P = 0.93) DMI of ewes; however, it increased milk production (P < 0.01) and feed efficiency (P = 0.02; FE). Ewes fed N13 had a greater milk fat (P < 0.01), protein (P < 0.01), lactose (P = 0.04), and total solids production (P < 0.01). Narasin inclusion in ewe’s diet increased plasma glucose concentration (P = 0.05) at weeks 8, 9 and 10; however, there was no effect on plasma urea concentration (P = 0.96). The lambs of N0 ewes had a greater starter DMI (P < 0.01) at weeks 7, 8, 9, and 10; however, the ADG and body weight at weaning and after weaning were similar between treatments (P > 0.05). The results showed that the inclusion of 13 mg of narasin/kg DM improved the milk production and FE of the ewes without altering the composition of the milk. The lower initial consumption of concentrate by N13 lambs before weaning was caused by the higher production of milk. The results obtained in the present study demonstrate the possible productive gain with the inclusion of narasin in diets for lactating ewes.

The objective of this work was to evaluate the effect of narasin inclusion in mineral and protein supplements on the performance and supplement intake of grazing beef yearlings. One hundred and fifty Nellore yearlings with 17.0±0.06 months of age and 219.7±1.62 kg initial body weight (BW) were allocated into 30 experimental units (EUs), with five animals each. The EUs were assigned to 16 paddocks, which were continuously stocked for 28 days, followed by 28 days of rest. A randomized complete block design was used. The experiment lasted 140 days, divided into five periods of 28 days each. The assessed treatments were: control mineral supplement (CON); CON + 1,800 (N1800) or 2,750 (N2750) mg narasin per kilogram of supplement; and protein mineral supplement (PROT) or PROT + 360 mg narasin per kilogram of supplement (PROT 360). The inclusion of narasin in the mineral supplement increased average daily gain (ADG) in the first period and decreased supplement intake in the first, second, and third periods, when compared with the CON treatment. The ADG and supplement intake were similar between the N1800 and N2750 treatments. Narasin has a positive effect on ADG up to 28 days of supplementation and controls mineral supplement intake, without compromising this gain. Resumo: O objetivo deste trabalho foi avaliar a inclusão de narasina em suplementos mineral e proteico sobre o desempenho e o consumo de suplemento de novilhos de corte em pastagem. Cento e cinquenta novilhos Nelore com 17,0±0,06 meses de idade e 219,7±1,62 kg de peso inicial foram distribuídos em 30 unidades experimentais (UEs), com cinco animais cada uma. As UEs foram dispostas em 60 piquetes, os quais foram pastejados continuamente por 28 dias, seguidos de 28 dias de descanso. Utilizou-se o delineamento de blocos ao acaso. O tempo de duração do experimento foi de 140 dias, dividido em cinco períodos experimentais de 28 dias cada um. Os tratamentos avaliados foram: suplemento mineral controle (CON); CON + 1.800 (N1800) ou 2.750 (N2750) mg de narasina por quilograma de suplemento; e suplemento mineral proteinado (PROT) ou PROT + 360 mg de narasina por quilograma de suplemento (PROT 360). A inclusão de narasina na mistura mineral aumentou o ganho médio diário (GMD) durante o primeiro período e reduziu o consumo de suplemento no primeiro, no segundo e no terceiro períodos, quando comparado ao tratamento CON. O GMD e o consumo de suplemento foram semelhantes entre os tratamentos N1800 e N2750. A narasina tem efeito positivo no GMD até 28 de suplementação e controla o consumo de suplemento mineral, sem comprometer esse ganho.

This trial aimed to evaluate the effects of thyme essential oils (EO) on rumen parameters, nutrient digestibility and nitrogen balance in wethers fed with high-concentrate diet. Twenty rumen-cannulated wethers were blocked according to body weight (BW= 64.0±2.1kg), and received one of the following treatments: 25mg of monensin/kg of dry matter (DM; MON) or doses of thyme EO (1.25, 2.50 or 3.75g/kg of DM). The diet was composed of 90% concentrate. Thyme EO was composed mainly by thymol (46.6% of DM) and p-cymene (38.9% of DM). The nutrient intake and apparent digestibility were similar among treatments. The inclusion of 3.75g of thyme EO tended (P= 0.07) to increase butyrate compared to MON and 1.25OE and wethers fed with 1.25g of thyme EO tended (P= 0.07) to decrease ruminal pH on the 14th day compared to MON. The treatments did not affect acetate:propionate ratio, total short chain fatty acids (SCFA) and nitrogen retention. Results from this study suggest that adding thyme EO to high-concentrate diets may be used as an alternative to monensin as feed additive in feedlot lambs.

The aim of this study was to evaluate three feed additives for rumen manipulation. Thirty-two rumen-fistulated animals were assigned to a completed randomized block design, according to their initial BW. Steers were fed with 99% of coastcross haylage and 1% of concentrate, used as vehicle for the additives. The forage and concentrate were offered separately, whereas the forage was offered after the entire consumption of the concentrate. The experimental diets consisted in: CON = Control (no feed additive); NAR = 13ppm of Narasin; SAL = 20ppm of Salinomycin; and FLA = 3ppm of Flavomycin. 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 using the MIXED procedure of SAS. Data obtained on d 0 were used as covariate. Tukey test 5% was used for comparisons. There was treatment effect on acetate (CON: 73.5ab; NAR: 73.0a; SAL: 73.9b and FLA: 73.6b mM/100mM, P = 0.01; SEM = 0.16), propionate (CON: 13.7b; NAR: 14.6a; SAL: 13.5b and FLA: 13.4b, P = 0.01; SEM = 0.11), butyrate (CON: 9.06a; NAR: 8.64b; SAL: 8.72ab and FLA: 8.96ab, P = 0.02; SEM = 0.10), isovalerate (CON: 1.51b; NAR: 1.61ab; SAL: 1.55ab and FLA: 1.67b, P = 0.03; SEM = 0.04) and ac:prop ratio (CON: 5.39a; NAR: 4.99b; SAL: 5.49a and FLA: 5.4a, P = 0.01; SEM = 0.05). Therefore, narasin improves energetic efficiency of ruminal fermentation compared to other additives.

The objective of this study was to determinate the effects of narasin on carcass characteristics of lambs fed a diet containing different levels. Forty-four lambs were allotted in a randomized complete block design, defined by initial body weight (BW), in a 2x2 factorial arrangement. The first factor was forage (coastcross hay) inclusion (10 or 20%, DM basis) and the second factor was narasin (0 or 13 ppm). The experimental diets were isonitrogenous (17.4%, DM basis). The experiment lasted 112 days. At the end of the experiment, the lambs were slaughtered to evaluate the carcass characteristics and meat composition. Data were analyzed using the MIXED procedure of SAS and the LSMEANS option was used to obtain the means. The effects were considered significant when P < 0.05. There was no interaction between forage levels and narasin inclusion. The experimental diets did not affect the slaughter BW (54.8 ± 1.6 kg), hot carcass weight (29.3 ± 0.96 kg), dressing percentage (53.5 ± 0.67%) and LM area (18.8 ± 0.89 cm2). The inclusion of narasin increased 12th-rib fat (2.10 vs 2.75 mm; P < 0.01) and BW thickness (16.9 vs 20.2 mm; P < 0.01). The inclusion of 20% of hay decreased BW thickness (19.21 vs 17.9 mm; P = 0.03). The experimental diets did not affect the moisture (74.2 ± 0.53%) and ash content in meat (1.27 ± 0.04%). Narasin inclusion increased the fat (2.81 vs 3.62%; P < 0.01) and decreased the CP (21.3 vs 20.7%; P = 0.02) in meat composition. The inclusion of 10% of hay increased the fat in meat (3.5 vs 2.9%; P = 0.03), however, did not affect the CP content. In conclusion, the narasin inclusion and levels of hay improve the carcass characteristics and change the meat composition.

The aim of this study was to compare the effects of three additives (narasin, lasalocid, and virginiamycin) on the performance of bulls fed a high-forage diet. One hundred and sixty Nellore (Bos indicus) yearling bulls were assigned to a randomized completed block design, according to initial BW (212.5 kg ± 3.1; 10 pen/treatment; 4 animals/pen). Yearling bulls were fed daily and diets were composed of 96% of coastcross haylage (12% CP) and 4% of concentrate, used as the delivery vehicle for the additives. Once a day, the concentrate and forage were offered separately. The forage was offered after the entire consumption of the concentrate. The experimental diets consisted of CON: Control (no additives); NAR: 13 ppm of narasin; LAS: 20 ppm of lasalocid; and VIR: 20 ppm of virginiamycin. The experimental period lasted 140 d and the yearling bulls were individually weighed at d 0, 28, 56, 84, 112 e 140 after 14h of feed and water restriction. The orts were recorded to determine the DMI. Data were analyzed as repeated measures over time using the MIXED procedure of SAS and the LSMEANS option was used to generate individual means. There was a treatment effect on DMI (CON: 5.26b: NAR: 5.69a; LAS: 5.16b; VIR: 5.11b kg/d; SEM = 0.14; P = 0.03), ADG (CON: 0.451b; NAR: 0.557a: LAS: 0.498ab; VIR:0.459b kg; SEM = 0.03; P = 0.04), FE (0.080c, 0.095a, 0.092ab and 0.085bc; SEM = 0.0044; P = 0.05) and final BW (CON: 273.9b; NAR: 287.8a; LAS: 277.1b; VIR: 275.7b kg SEM = 3.4; P = 0.03). In conclusion, the inclusion of 13 ppm of narasin improves the performance of yearling bulls fed high-forage diets.

The objective of this study was to determine the effects of forage levels and narasin inclusion in diets on the rumen parameters in feedlot lambs. Forty-four lambs were allotted in a randomized complete block design, defined by initial body weight, in a 2x2 factorial arrangement. The first factor was forage inclusion (10 or 20% of coastcross hay, DM basis) and the second factor was narasin (0 or 13 ppm). The experimental diets were isonitrogenous (17.4%, DM basis). At the end of the experimental period, the lambs were slaughtered without fasting, and the rumen fluid was collected to determinate pH and short chain fatty acid (SCFA). Data were analyzed using the MIXED procedure of SAS and the LSMEANS option was used to obtain the means. The effects were considered significant when P < 0.05. There was an interaction between hay and narasin on the molar proportion of propionate (P = 0.02) and the acetate:propionate ratio (P < 0.01). Narasin inclusion in diets containing 20% forage increased propionate (25.4 vs 37.1 mM/100mM; P = 0.02); however, there was no effect in diets containing 10% forage (35.9 ± 1.75 mM/100Mm). Consequently, the narasin decreased acetate:propionate ratio in diets containing 20% forage (2.57 vs 1.42; P < 0.01), and no effect was observed 10% forage diets (1.40 ± 0.14). The inclusion of narasin increased the total SCFA (86.2 vs 115.4 mM; P < 0.01), ruminal pH (6.26 vs 6.49; P = 0.05) and decreased acetate (55.6 vs 47.6 mM/100mM; P < 0.01). The inclusion of 20% forage increased acetate when compared with 10% hay (54.99 vs 48.19 mM/100mM; P < 0.01) and the pH ruminal (6.25 vs 6.49; P = 0.04). The experimental diets did not affect the butyrate. In summary, the narasin inclusion and forage levels content change rumen parameters in feedlot lambs.

The objective of this study was to determinate the effects of forage levels and narasin inclusion on the performance of feedlot lambs. Forty-four lambs were allotted in a randomized complete block design, defined by initial body weight (BW), in a 2x2 factorial arrangement. The first factor was forage (coastcross hay) inclusion (10 or 20%, DM basis) and the second factor was narasin (0 or 13 ppm). The experimental diets were isonitrogenous (17.4%, DM basis). The experiment lasted 112 days, divided into two periods of 56 d each. The lambs were weighed after a fasting period of 14 hours on days 0, 56, and 112. Average daily gain (ADG), dry matter intake (DMI) and feed efficiency (FE) were determined in each period. Data were analyzed as repeated measures over time using the MIXED procedure of SAS and the LSMEANS option was used to obtain the means. The effects were considered significant when P < 0.05. There was no interaction between forage levels and narasin inclusion. Narasin did not affect the DMI, ADG, and FE. There was hay levels and period interaction for DMI and ADG. Increase levels of hay did not affect the DMI during the first period; however, 20% of hay inclusion increased DMI in the second period (1.16 vs 1.30 kg/d; P = 0.01). The inclusion of 10% of hay increased the ADG in the first period (0.28 vs 0.24 kg/d; P < 0.01), however, there was no effect in the second period. Consequently, 10% of forage inclusion increased the FE (0.23 vs 0.21; P = 0.01). In summary, diets containing 10% of forage improves the FE, and narasin inclusion did not affect the lamb’s performance.

Narasin is a feed additive used to alter ruminal fermentation and increase performance of cattle fed forage-based diets. The present study had two objectives: 1) to define the best dose of narasin for lambs fed forage-based diets; 2) evaluate whether the quality of the forage used can affect the action of narasin on performance of lambs. In Exp. 1, fifty-one crossbred ewe’s lambs [Dorper × Santa Ines; initial body weight (BW) = 25.9 ± 0.07 kg and 145 ± 2.1 d of age], were stratified by initial BW and randomly allotted in a tie-stall system in a randomized complete block design with 17 blocks and 3 treatments. The treatments for the 63-d feeding trial consisted of: 1) forage-based diet without narasin (CONT; n = 17), 2) CONT diet plus 13 ppm of narasin (13 N; n = 17), and 3) CONT diet plus 20 ppm of narasin (20 N; n = 17). Experimental diets were composed by 80 % of coastcross hay (Cynodon dactylon spp.) and 20 % of concentrate, which was used as delivery vehicle for the narasin treatments. Narasin inclusion increased (P 0.49) among hay quality and narasin inclusion for any variable analyzed. Hay with high CP increased (P

The objective of this trial was to determine the effect of narasin inclusion into a protein supplement on the performance of grazing yearling bulls. One hundred and fifty Nellore yearling bulls were blocked by initial BW (332 ± 3.4 kg) and assigned to 30 paddocks (15 paddocks/treatment). Sixty paddocks of Brachiaria brizantha with 1 ha each were used, whereas each paddock was continuously grazed by 28 d, followed by a resting period of 28 d. Paddocks were rotated among treatments every 28 d to minimize possible paddock variation. The experimental period lasted 112 d, divided into 4 periods of 28 d each. The treatments were: 1) negative control (no narasin: 0N), and 2) 13 ppm of narasin/d (13N; Zimprova®; Elanco, São Paulo, Brazil). Narasin was added to the protein supplement by adjusting its concentration in each 28-d period, according to the supplement intake (SI) during the previous period. The SI was evaluated on a weekly basis. Forage mass in the paddocks was measured by choosing two points upon entry and exit of the lot from each pasture. All data were analyzed using the PROC MIXED procedure of SAS. The ADG and SI were analyzed as repeated measures over time. There was no treatment × period interaction for ADG (P = 0.06) and SI (P = 0.66). Narasin inclusion into the protein supplement did not affect SI (0N = 435.5, 13N = 431.3 g/d; SEM = 12.2; P = 0.74), increased the ADG (0N = 0.240, 13N = 0.284 kg; SEM = 0.017; P < 0.01) and the final BW of the yearling bulls (0N = 357.7, 13N = 363.0 kg; SEM = 3.43; P < 0.01). In conclusion, narasin inclusion into protein supplement improved the performance of grazing yearling bulls.

Essential oil (EO) from Brazilian red pepper fruit contains compounds with antimicrobial activity, and could be possible substitutes for the antibiotics commonly used in ruminant nutrition. Te objectives of the present study were to evaluate the efects of the Brazilian red pepper fruit EO (Schinus terebinthifolius) as a substitute for monensin on performance, carcass characteristics and meat of lambs fed high concentrate diets. Forty-eight lambs were used, 24 males (20 ½ Dorper × ½ Santa Inês and 4 Santa Inês) and 24 females (24 ½ Dorper × ½ Santa Inês), with 21.54 ± 0.88 kg of initial body weight (BW) and 78 ± 2.4 days of age, in a randomized complete block design. Te experiment lasted 56 days, divided into 2 periods of 28 days each. Te treatments were defned by the inclusion in diets of 8 ppm of monensin (MON), and the doses 0.14% (14EO), 0.28% (28EO) and 0.42% (42EO) of red pepper fruit EO. Te additives were included in a base diet with a 10:90 of forage to concentrate ratio. At the end of 56 days, 32 animals were slaughtered for the measurement of carcass parameters and meat composition. Tere was no interaction among treatments and periods for average daily gain (P = 0.08), DM intake (P = 0.36), feed efciency (P = 0.24) and oocyst of Eimeria ssp. in feces (P = 0.46). Te treatments did not afect (P > 0.05) the average daily gain (ADG), dry matter intake (DMI) and feed efciency. Lambs fed diets containing monensin had less (P < 0.01) oocyst/g compared with the diet 14EO. Tere was no efect of diets on carcass characteristics. Te treatments with higher doses of the Brazilian red pepper fruit EO had reduced mineral content of meat compared to monensin. Te red pepper fruit EO demonstrated the potential to replace monensin in feedlot lambs fed high concentrate diets, maintaining performance and carcass characteristics. However, the monensin has greater capacity to control coccidiosis in feedlot lambs. Os óleos essenciais (OE) dos frutos de aroeira possuem compostos com atividade antimicrobiana, sendo possíveis substitutos aos antibióticos comumente utilizados na nutrição de ruminantes. Os objetivos do presente estudo foram avaliar os efeitos da inclusão do óleo essencial de aroeira fruta (Schinus terebinthifolius) como substituto da monensina sobre o desempenho, características de carcaça e da carne de cordeiros alimentados com dietas contendo elevado teor de concentrado. Foram utilizados 48 cordeiros, 24 machos (20 ½ Dorper × ½ Santa Inês e 4 Santa Inês) e 24 fêmeas (24 ½ Dorper × ½ Santa Inês), com peso inicial de 21,54 ± 0,88 kg e 78 ± 2,4 dias de idade, em delineamento de blocos completos casualizados. O experimento teve duração de 56 dias, divididos em 2 períodos de 28 dias cada. Os tratamentos foram defnidos pela inclusão na dieta de 8 ppm de monensina sódica (MON) e as doses de 0,14% (14EO), 0,28% (28EO) e 0,42% (42EO) de óleo essencial dos frutos da aroeira. As dietas experimentais foram compostas por 10% de volumoso e 90% de concentrado. Ao fnal dos 56 dias, 32 animais foram abatidos para a mensuração dos parâmetros de carcaça e análise química da carne. Não houve interação entre tratamento e período para o ganho médio diário (P = 0,08), consumo de MS (P = 0,36), efciência alimentar (P = 0,24) e contagem de oocistos de Eimeria ssp. (P = 0,46). Não houve efeito (P > 0,05) dos tratamentos no ganho de peso médio diário (GMD), consumo de matéria seca (CMS) e efciência alimentar (EA). Cordeiros alimentados com dietas contendo monensina tiveram menor (P < 0,01) contagem de oocistos/g de fezes comparado com a dieta 14OE. Não houve efeito das dietas sobre as características de carcaça.A inclusão de 0,28 e 0,42% de OE de aroeira fruto reduziram a concentração de matéria mineral da carne dos cordeiros comparados ao tratamento MON. O OE dos frutos da aroeira demonstrou capacidade de substituir a monensina, apresentando resultados similares com relação ao desempenho e características de carcaça. Entretanto, a monensina apresentou maior capacidade no controle de coccidiose.

Two experiments were conducted to evaluate the effect of thyme (Thymus vulgaris) essential oil (EO) doses on rumen fermentation, nutrient digestibility, and nitrogen metabolism, as well as performance and coccidia oocyst discharge. In experiment I, 20 rumen-cannulated wethers received the experimental diets containing 80% dry matter (DM) of haylage and 20% DM of concentrate. Treatments were 25mg of monensin/kg DM or doses of 1.25, 2.50, or 3.75g of thyme EO/kg DM. In experiment II, 50 ewe lambs received the same diets from experiment I, including a diet without feed additives. Wethers fed with diets containing 1.25g/kg DM of thyme EO had higher molar proportion of propionate (P= 0.03) and butyrate (P< 0.01), and lower (P= 0.04) acetate to propionate ratio than other treatments. Adding thyme EO to diets increased (P= 0.02) nitrogen retention compared to monensin. The performance of ewe lambs was not affected (P≥ 0.05) by treatments. However, lambs fed monensin had a lower (P= 0.04) number of coccidia oocyst discharge than others. Adding 1.25g/kg DM of thyme EO in high-forage diet improved ruminal fermentation. Thyme EO enhanced nitrogen metabolism, however, it did not improve performance.

The objective of this trial was to determine the effect of narasin inclusion into a mineral salt on the performance of grazing bulls. Two hundred and forty Nellore yearling bulls were blocked by initial BW (193.1 ± 3.34 kg) and assigned to 32 paddocks (16 paddocks/treatment). Sixty-two paddocks of Brachiaria brizantha with 1 ha each were used, whereas each paddock was continuously grazed by 28 d, followed by a resting period of 28 d. Paddocks were rotated among treatments every 28 d to minimize the possible paddock variation. The experimental period lasted 112 d, divided into 4 periods of 28 d each. The treatments were: 1) negative control (no narasin; 0N), and 2) 13 ppm of narasin/d (13N; Zimprova(®); Elanco, São Paulo, Brazil). Narasin was added on the mineral salt by adjusting its concentration in each 28-d period, according to the mineral intake (MI) during the previous one. The MI was evaluated on a weekly basis. Forage mass in the paddocks was measured by choosing two points upon entry and exit of the lot from each pasture. All data were analyzed using the PROC MIXED procedure of SAS. The ADG and MI were analyzed as repeated measures over time. There was no treatment × period interaction for ADG (P = 0.40) and MI (P = 0.27). Nonetheless, narasin inclusion into the mineral salt did not affect MI (0N = 64.1, 13N = 64.9 g/d; SEM = 1.77; P = 0.27), increased the ADG (0N = 0.555, 13N = 0.639 kg/d; SEM = 0.02; P < 0.01) and the final BW of the animals (N0 = 254.5, N13 = 263.6 kg; SEM = 4.62; P < 0.01). In summary, narasin inclusion into the mineral salt improved the performance of grazing yearling bulls.

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.

Essential oil (EO) from Brazilian red pepper leaves contains antimicrobial compounds that control Gram-positive bacteria in the rumen content, improving the efficiency of ruminal fermentation. The objectives of the present study were to evaluate the effects of the Brazilian red pepper leaves EO (Schinus terebinthifolius) as a substitute for monensin on performance, occurrence of coccidiosis by Eimeria ssp., carcass characteristics and meat composition of feedlot lambs. Forty-four lambs, 16 males (12 ½ Dorper × ½ Santa Inês and 4 Santa Inês) and 28 females (16 ½ Dorper × ½ Santa Inês and 12 Santa Inês), with 21.4 ± 1.05 kg of initial body weight (BW), were used in a randomized complete block design. The experiment lasted 56 days, divided into 2 periods of 28 days each. The treatments were defined by the inclusion of 8 ppm of monensin (MON), and the doses 0.14% (14EO), 0.28% (28EO) and 0.42% (42EO) of red pepper leaves essential oil (EO). At the end of 56 days, 32 lambs were slaughtered for the measurement of carcass parameters and meat composition. There was no interaction among treatments and periods for average daily gain (ADG), dry matter intake (DMI), feed efficiency (FE) and oocyst of Eimeria ssp. in feces. The treatments did not affect the ADG, DMI and FE; however, the monensin inclusion decreased the oocyst of Eimeria ssp. (P = 0.01). There was a tendency (P = 0.06) of increase in hot carcass yield for lambs fed 28EO compared to 14EO. In addition, the cold carcass yield was higher (P = 0.02) in the animals fed 28EO and 42EO. The subcutaneous fat thickness was not affected by the experimental diets; however, there was a tendency for lambs from 28EO and 42EO treatments to present higher body wall thickness (P = 0.07) and Longissimus muscle area (P = 0.07) when compared to MON. The higher doses of red pepper leaves EO increased the percentage of crude protein (P < 0.01) and mineral matter (P = 0.02) in the chemical composition of meat. Although the performance of lambs did not change, the inclusion of 0.28 and 0.42% red pepper leaves EO improve the carcass characteristics and change the meat composition, demonstrating the potential of the use of this additive in confined lamb diets. However, the monensin has greater potential to control coccidiosis in feedlot lambs compared with red pepper leaves EO.

The aim of this study was evaluating the effects of different feed additives on performance of yearling bulls fed a high forage diet. One hundred and sixty-four Nellore (Bos indicus) yearling bulls were assigned to a complete randomized block design, according to of their initial body weight (BW) (298.95 ± 2.49; 10 pen/treatment; 4 animal/pen). Yearling bulls were fed daily and diets were composed of 96% of coastcross haylage and 4% of ground corn, used as the delivery vehicle for the additives. Once a day, the concentrate and forage were offered separately. The forage was offered after the entire consumption of the concentrate. The experimental diets consisted in: CON = Control (no feed additive); FLA = 3ppm of Flavomycin; NAR = 13ppm of Narasin; SAL = 20ppm of Salinomycin. The experimental period lasted 140 d and the yearling bulls were weighted at 0, 28, 56, 84, 112 and 140 d, after a 14h feed and water restriction. The orts were recorded to determine the dry matter intake (DMI). All data were analyzed using the MIXED procedure of SAS and the LSMEANS option was used to generate individual means. Tukey test 5% was used for comparisons. There was a treatment effect on DMI (CON: 6.59b; FLA: 6.53b; NAR: 7.1a; SAL: 6.42b kg/d; SEM = 0.19; P < 0.01), ADG (CON: 0.792b; FLA: 0.842b; NAR: 0.907a; SAL: 0.813b kg; SEM = 0.02; P < 0.01) and final BW (CON: 408.27b; FLA: 411.36b; NAR: 424.69a; SAL: 407.91b kg; SEM = 2.56; P < 0.01). There was no effect on feed efficiency (P = 0.41). In summary, the narasin inclusion increased DMI, ADG, and final BW in comparison with the other additives.

Forty-four ½ Dorper x ½ Santa Inês lambs (initial BW 33.3 ± 0.59 kg) were used in a randomized block design to evaluate the effects of different supplementation frequencies of narasin on lamb′s performance. The experimental diets consisted of 95 % coastcross hay (11.2 % CP) and 5 % ground corn (DM basis), used as delivery vehicle for the narasin. The fed offer and orts were measured daily. The treatments were: N0: ground corn without narasin; N24: daily offer of narasin 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 (13 ppm of narasin on average); 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 105 days, divided into 5 periods of 21 days each. The lambs were weighed at the end of each period after 14 hours fasting of feed and water. All data were analyzed using the MIXED procedure of SAS and the treatments were compared through Tukey test at 5%. There was no effect on narasin intake (P < 0.01) among treatments N24, N48 and N72 (17.6 ± 0.34 ppm). There was no treatment effect on DMI (0.81 ± 0.03 kg/d; P = 0.28). Nonetheless, lambs fed N24 and N48 had a greater ADG (N0 = 41.1(ab); N24 = 56.9(a); N48 = 54.9(a); N72 = 34.9(b) g/d; P = 0.03) and feed efficiency (N0 = 0.05(bc); N24 = 0.06(ab); N48 = 0.07(a); N72 = 0.04(c); P = 0.02). In summary, narasin must be offered daily or every 48 hours in order to improve the performance of lambs fed high forage diets.

The narasin is an antibiotic that causes changes in the ruminal microbiota by altering the final product of the fermentation. The objective of this trial was to determine the effects of Narasin on ewe milk yield and milk composition. After lambing, 32 ewes were allotted in a randomized complete block design, defined by initial body weight, number and sex of offspring. Diets were isonitrogenous (13.6% CP, DM basis), composed of 50% concentrate and 50% coastcross hay and fed daily, “ad libitum”. The narasin levels were 0 or 13 ppm, corresponding to the experimental diets N0 and N13. From the 2nd until the 10th week of lactation, DMI was determined, whereas in the same period, once a week, the ewes were separated from the 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 (2.27 ± 0.10 kg/d; P = 0.93), however, it increased milk production (N0 = 193.9; N13 = 241.4 g/3h; P < 0.01). Consequently, narasin supplementation increased fat (N0 = 16.5; N13 = 22.4 g/3h; P < 0.01), protein (N0 = 8.0; N13 = 10.0 g/3h; P < 0.01), lactose (N0 = 9.3; N13 = 11.1 g/3h; P = 0.04) and total solids production (N0 = 35.2; N13 = 45.9 g/3h; P < 0.01). There was no effect in the milk composition (%; P > 0.05). In conclusion, narasin administration at 13 ppm improved the lactation performance in ewes offered a 50 % concentrate diet.

O crescimento compensatório pode ser uma ferramenta interessante em sistemas de criação de bovinos de corte, uma vez que os animais que passam por crescimento compensatório são mais eficientes, diminuindo o custo com alimentação. É bem aceito que a nutrição é capaz de influenciar a idade à puberdade de novilhas, no entanto, pouco se sabe sobre o efeito do crescimento compensatório na puberdade de novilhas Nelore. O objetivo deste trabalho foi avaliar o efeito de ritmos de crescimento e crescimento compensatório sobre a idade e peso à puberdade de novilhas Nelore. Para isso, foram utilizadas 120 novilhas da raça Nelore, desmamadas com oito meses de idade e filhas de 6 touros que foram alocadas em quatro tratamentos de acordo com o peso inicial de 180 ± 8,6 kg. O período experimental foi dos 8 aos 18 meses de idade. Tratamentos: 1) GMD elevado (CMS d libitum), cerca de 1kg/dia, durante todo o período experimental (ALTO). 2) GMD médio (0,6kg/dia) durante o período experimental (MÉDIO). 3) Restrição alimentar por 4 meses (0,2kg/dia), seguido de CMS ad libitum com crescimento compensatório (RESTRITO). 4) CMS ad libitum (GMD elevado) por dois meses, alternando com restrição alimentar (0,2kg/dia), durante um período total de 10 meses (ALTERNADO). A restrição alimentar foi realizada através da restrição quantitativa do CMS, e o crescimento compensatório e o GMD alto foram obtidos através do CMS ad libitum. As novilhas passaram por exame ginecológico semanalmente e a manifestação da puberdade foi acompanhada por meio de US (presença de CL) e colheita de sangue (determinação de P4). Também foi determinada a concentração de IGF-1 (8, 10, 12, 14, 16 e 18 meses de idade e no momento da puberdade) e leptina (8, 11 e 18 meses de idade e no momento da puberdade). Ao final do experimento, as novilhas que não entraram em puberdade foram submetidas a um protocolo de indução de puberdade com P4. O delineamento utilizado foi em blocos casualizados incompletos (touro), sendo as variáveis contínuas analisadas pelo procedimento MIXED e as variáveis binomiais avaliadas pelos procedimentos GLIMMIX ou LIFETEST quando avaliadas as curvas de sobrevivência, todos procedimentos procedimento do SAS 9,3. Não houve diferença na porcentagem de novilhas púberes aos 18 meses de idade entre os tratamentos. O peso a puberdade e a idade a puberdade também não diferiram entre os tratamentos. Entretanto, o GMD ao longo do experimento (P

This study aimed to determine whether reproductive performance of ewes submitted to laparoscopic timed artificial insemination (TAI) would be similar to ante meridiem (AM)/post meridiem (PM) rule and assisted natural mating (NM), and whether GnRH may enhance the pregnancy rate in TAI. In experiment I, 191 non-lactating ewes were synchronized, then TAI was performed either 48 h after progesterone (P4) removal (TAI-48 h) or 12 h after estrus detection (AM/PM); moreover, some ewes were submitted to NM (NM) as control treatment. In experiment II, 247 non-lactating ewes were allocated in five treatments, a control (no-GnRH on protocol) and four treatments arranged in a factorial design 2 × 2. The factors were time and dose of GnRH: ewes that received either 10 μg (TAI-10 μg-36 h) or 25 μg of GnRH (TAI-25 μg-36 h) 36 h after P4 removal and ewes that received either 10 μg (TAI-10 μg-48 h) or 25 μg of GnRH (TAI-25 μg-48 h) at time of insemination, 48 h after P4 removal. In experiment I, pregnancy rate in TAI-48 h was lower (P = 0.03) than AM/PM and NM. Moreover, the probability of pregnancy in TAI-48 h was higher (P = 0.06) in ewes detected in estrus early. In experiment II, the use of GnRH in TAI protocols increased (P

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.