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Adding ionophores to ruminant diets is a strategy to manipulate ruminal fermentation and improve milk yield. This study evaluates the effects of narasin supply to lactating ewes on dry matter intake (DMI), milk yield and composition, and performance of the lambs. Thirty lactating Santa Inês and Santa Inês × Dorper ewes fed a basal diet containing 50 % coastcross hay and 50 % concentrate were randomly assigned to two treatments: control (CON; without ionophores) or NAR (addition of 13 mg narasin kg–1 DM). From the 2nd to 10th week of lactation, DMI of ewes was determined, and once a week, their milk production and composition was measured over a 3-h interval. At the 10th week of lactation, lambs were weaned and their average daily gain (ADG) and starter DMI continued to be evaluated for two more weeks. Narasin supply did not affect weight and DMI of ewes. Ewes fed NAR had greater feed efficiency for milk production and displayed tendency for higher milk yield. Narasin supply reduced milk protein levels, but it did not affect other milk component levels. Ewes fed NAR had greater production of milk urea nitrogen and showed tendency for higher production of fat and total solids. Starter DMI of lambs was not affected by treatments; however, there was a tendency for greater weaning weight for NAR lambs. At the end of experiment, no differences were observed in the performance of lambs. The supply of 13 mg narasin kg–1 to lactating ewes improved milk yield efficiency and tended to increase the weaning weight of their lambs.

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.

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

Made available in DSpace on 2021-06-25T11:20:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 The objectives were to evaluate the effects of two non-fibrous carbohydrate sources and the rate of body weight gain on puberty status in ewe lambs. Sixty ewe lambs (1/2 Dorper x 1/2 Santa Ines) with an initial body weight of 25.1 +/- 4.1 kg and 102.8 +/- 1.5 days old were distributed in a randomized complete block design with 10 blocks and 3 treatments. The trial lasted 119 days, in which performance was evaluated on days 28, 56, 84, and 119, and puberty status was every week evaluated by progesterone concentration. The treatments were characterized by the inclusion of different carbohydrate sources in the diets in order for ewe lambs to reach different rates of body weight gain: CORN, total diet containing 46% of corn (% DM); PCP, total diet containing 46% of pelleted citrus pulp (% DM); and HAY, total diet containing 80% of coastcross hay (% DM). The CORN- and PCP-based diets were formulated for an average daily gain (ADG) of 0.200 kg/day and a HAY-based diet for an ADG of 0.100 kg/day. There was an interaction between treatments and experimental periods for dry matter intake (DMI) (P < 0.01), in which lambs in the CORN treatment presented DMI similar to PCP in the first and second periods, but lambs from the PCP treatment presented lower DMI than the CORN treatment in subsequent periods. In all periods, the body weight, average daily gain, and feed efficiency of CORN lambs were similar to PCP lambs, but higher thanHAY lambs. The age at puberty was not affected by treatments; however, lambs fed with non-fibrous carbohydrate sources reached puberty heavier (P < 0.0001) than lambs from the HAY treatment. Despite the high increase in body weight for lambs fed with non-fibrous carbohydrate sources, it did not affect the age of puberty. Univ Sao Paulo, Dept Anim Sci, Coll Agr Luiz de Queiroz, Padua Dias Ave 11,POB 09, BR-13418900 Piracicaba, SP, Brazil Univ Fed Amazonas, Dept Anim Sci, Gen Rodrigo Octavio Ave 6200, BR-69152240 Manaus, Amazonas, Brazil Univ Estadual Ponta Grossa, Dept Anim Sci, Gen Carlos Cavalcanti Ave 4748, BR-84030900 Ponta Grossa, Parana, Brazil Univ Sao Paulo, Coll Vet & Anim Sci, Dept Nutr & Anim Prod, Duque Caxias North Ave 225, BR-13635000 Pirassununga, SP, Brazil Sao Paulo State Univ, Sch Engn, Brasil Ave 56, BR-SAO PAUL Ilha Solteira, SP, Brazil Sao Paulo State Univ, Sch Engn, Brasil Ave 56, BR-SAO PAUL Ilha Solteira, SP, Brazil

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.

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.

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.

Narasin is an antibiotic ionophore that may change rumen fermentation; however, the effects on the post-rumen are unknown. The objective of this study was to determinate the effects of different levels of hay and narasin inclusion on the cecal parameters of lambs. Forty-four lambs were allotted in a randomized complete block design, defined by initial BW, in a 2x2 factorial treatment 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) and the experiment lasted 112 days. At the end of the experimental period, the lambs were slaughtered without fasting, and the cecal fluid was collected to determinate pH and short chain fatty acid (SCFA). Data were analyzed using the MIXED procedure of SAS. The effects were considered significant when P < 0.05. There was no interaction between forage content and narasin inclusion. Narasin increased the molar concentration of propionate (N0: 19.4; N13: 21.4 mM/100mM; P = 0.02) and decreased isobutyrate (N0: 1.6; N13: 0.7 mM/100mM; P = 0.05) and acetate:propionate ratio (N0: 3.4; N13: 2.9; P = 0.03). The valerate was greater in diets with 10% hay when compared of diets 20% (H10: 2.0; H20: 1.3 mM/100mM; P < 0.01). The experimental diets not affect the molar proportion of acetate (62.7±1.3 mM/100mM), butyrate (12.9 ± 0.7 mM/100mM), isovalerate (1.3 ± 0.5 mM/100mM) total SCFA concentration (68.6 ± 8.5 mM) and cecal pH (6.2 ± 0.14). Therefore, the inclusion of 13 ppm of narasin changes the cecal fermentation in high concentrate diets. In addition, the inclusion of 10 or 20% of hay has a little influence on cecal fermentation.

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.