Ruminal modulator additive effect of Stryphnodendron rotundifolium bark in feedlot lambs.

The study aimed to evaluate the inclusion effects of Stryphnodendron rotundifolium (barbatimão) extracts in substitution of the lasalocid sodium on the ingestive behaviour, intake, ruminal parameters, and digestibility of feedlot lambs. Twenty-four pantaneiro lambs were used, with an average age of 150 ± 4.59 days and an initial body weight of 21.2 ± 3.63 kg. The lambs were distributed in three treatments in an experimental design with randomized blocks. The treatments correspond to the additive supplements: LAS (0.019 g of lasalocid sodium/lamb/d); DGB (1.50 g of barbatimão dried ground bark/lamb/d); DHE (0.30 g of barbatimão dry hydroalcoholic extract/lamb/d). The DHE increased 59.74 min in the time spent for ingestion per day, resulting in an efficiency reduction of dry matter (DM) ingestion (127 g of DM/h of feed). There was a reduction of 1.8 mg/dL in the ammoniacal nitrogen concentration with extract supplementation compared to LAS. The DGB reduced total volatile fatty acids by 48.9% compared to the control treatment. The inclusion of barbatimão extracts (DGB and DHE) reduced 12.05% of ruminal butyrate content. The supplementation of barbatimão extracts replacing lasalocid sodium in the diet of feedlot lambs did not affect intake and caused small changes on ingestive behaviour.

Effects of lasalocid, narasin, or virginiamycin supplementation on rumen parameters and performance of beef cattle fed forage-based diet.

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.

Feed additives are nutritional tools that benefit dietary digestibility and nutrient utilization, alter ruminal fermentation routes, and improve cattle growth and efficiency, thus increasing productivity and profitability in beef cattle systems. Nonetheless, most of the current research focuses on supplementing feed additives in high-concentrate diets. Leaving a significant gap in understanding the influence of feed additives in cattle consuming forage-based diets, especially molecules capable of altering the fermentation process and, consequently, beef cattle performance. Therefore, this experiment aimed to evaluate the impacts of supplementing narasin (NAR), lasalocid (LAS), or virginiamycin (VRM) on rumen fermentation parameters, apparent nutrient digestibility, feed intake, and performance of Bos indicus Nellore cattle consuming a forage-based diet. Including commercially available feed additives into forage-based diets did not impact nutrient intake and digestibility of nutrients. The inclusion of NAR affected ruminal fermentation parameters toward propionate production, positively contributing to animal performance. Ruminal fermentation characteristics and animal growth were not impacted by dietary LAS and VRM, which could be attributed to the dose used in the current experiment, despite the manufacturer's recommendation. This research provides insights into NAR as an important feed additive for forage-based beef cattle diets.

The decrease of lasalocid residue in the edible tissues by silymarin supplementation of chicken diet.

Widespread use of coccidiostats, in spite of beneficial control of protozoan infections in poultry, implies a risk of residues in edible tissues, and there is increasing interest in the development of strategies for prevention of veterinary drugs residue in food-producing animals. The aim of this study is assigned to clarify the impact of silymarin addendum in the diet on lasalocid concentration in the liver and breast muscles from the broiler. Four groups of chickens received a feed with lasalocid at levels between 75 and 200 mg kg-1. Other four groups received a feed with lasalocid (75-200 mg kg-1) plus silymarin. Significant differences of lasalocid concentrations between the liver and breast muscles were observed. Moreover, the chickens from the groups supplemented with silymarin shown significant decreases of lasalocid concentrations in the analysed tissues. The herbal substance did not counteract the ionophore in the treatment of coccidiosis and did not change biochemical parameters of blood. These findings suggest that silymarin might be used in chicken feeding in order to reduce the risk from lasalocid contamination of the broiler edible tissues.

Repurposing Ionophores as novel antimicrobial agents for the treatment of bovine mastitis caused by Gram-positive pathogens.

Increasing reports of multidrug-resistant bacterial infections in animals has created a need for novel antimicrobial agents that do not promote cross-resistance to critically important antimicrobial classes used in human medicine. In response to the recent emergence of antimicrobial resistance in several bovine mastitis pathogens, in vitro antimicrobial susceptibility was determined for four polyether ionophores (lasalocid, monensin, narasin and salinomycin) against Staphylococcus spp. and Streptococcus spp. isolated from clinical cases. In addition, erythrocyte haemolysis and WST-1 cell proliferation assays were used to assess in vitro mammalian cell cytotoxicity and biofilm susceptibility testing was performed using the minimum biofilm eradication concentration (MBEC™) biofilm assay. Lasalocid, monensin, narasin and salinomycin exhibited bacteriostatic antimicrobial activity against all pathogens tested, including methicillin-resistant staphylococci, with MIC90 values <16 µg/ml. Narasin and monensin displayed the least toxicity against mammalian cell lines and all compounds significantly reduced viable cell numbers in a Staphylococcus aureus biofilm. Based on in vitro characterization, all four ionophores offer potentially novel treatments against bovine mastitis but in vivo studies will be essential to determine whether acceptable safety and efficacy is present following intramammary administration.

Effects of dried distiller's grains and lasalocid inclusion on feedlot lamb growth, carcass traits, nutrient digestibility, ruminal fluid volatile fatty acid concentrations, and ruminal hydrogen sulfide concentration.

Our hypothesis was that increasing the inclusion level of dried distiller's grains with solubles (DDGS) to feedlot lambs would increase growth and the inclusion of lasalocid (LAS; Bovatec, Alpharma, LLC, Bridgewater, NJ) would increase ADG and G:F, while not affecting digestibility, ruminal VFA concentration, and ruminal pH. Furthermore, we hypothesized that rations containing LAS and higher levels of DDGS would cause increased ruminal hydrogen sulfide gas (HS) concentrations. Two hundred forty crossbred (Suffolk × Rambouillet) lambs (31.9 ± 5.87 kg BW; approximately 90 d of age) were allocated to 6 treatments in a completely randomized design with a 3 × 2 factorial arrangement of treatments. Lambs were placed into 24 feedlot pens (4 pens/treatment; 10 lambs/pen) for a 111 d finishing study. Main effects included concentration of DDGS (0, 15, or 30% DM basis) and inclusion of LAS (0 or 22.05 g/metric ton LAS) resulting in treatments of: 1) 0% DDGS without LAS (0DDGS-NL), 2) 0% DDGS with LAS (0DDGS-L), 3) 15% DDGS without LAS (15DDGS-NL), 4) 15% DDGS with LAS (15DDGS-L), 5) 30% DDGS without LAS (30DDGS-NL), and 6) 30% DDGS with LAS (30DDGS-L). Two-day weights were taken at the beginning and end of the experiment. Two-hundred-eighteen lambs (64.8 ± 7.99 kg BW) were slaughtered on d 112 at a commercial abattoir and carcass data collected. The inclusion of LAS increased ( ≤ 0.02) final BW, ADG, G:F, and HCW. As DDGS in the ration increased to 30%, DMI decreased linearly ( = 0.03) while G:F increased linearly ( = 0.03). A second study was conducted utilizing the same treatments to evaluate N and S balance, ruminal VFA and H2S concentration, and ruminal pH in 24 crossbred wethers (Suffolk × Rambouillet; 41.2 ± 12.23 kg BW). Daily urinary sulfur excretion and ruminal H2S concentration were linearly increased ( < 0.001) as DDGS increased in the ration. Total ruminal VFA concentration linearly decreased ( = 0.002) as DDGS increased in the ration. The inclusion of LAS increased ( = 0.02) ruminal pH. The results confirm our hypothesis that LAS increased overall growth and increasing DDGS increased ruminal HS concentration but did not influence growth. We reject the hypothesis that the combined effects of LAS and DDGS would have no effect on rumen pH and VFA concentrations.

Performance of beef heifers supplemented with sodium lasalocid.

This study was conducted on 78 13-month-old crossbred beef heifers that weighed 215 kg in Southern Rio Grande do Sul (RS) State, Brazil. We evaluated the performance of beef heifers that were reared in a pasture system that received a mineral supplement energy-type protein with added sodium lasalocid (LAS). The heifers were randomly and uniformly divided into 2 groups, with 39 animals in each group. One group of animals received a mineral supplement energy-type protein without sodium lasalocid (CON), and the other group received a mineral supplement energy-type protein with added LAS. The mean feed intake, the body weight (BW), the average daily gain (ADG), the body condition score (BCS), and ovarian cyclicity were recorded, and economic parameters were calculated. No differences in supplement intake were observed between the groups, which ensures adequate intake of the other components of the mineral mixture, which are part of the nutritional requirements for the production process. Similarly, no difference in the ADG was observed between treatments. We observed that the heifers in the LAS group had a higher BW gain (51 kg) that the CON heifers (40 kg; P < 0.05). In addition, LAS-supplemented heifers had a higher BCS (3.53) than CON heifers (3.38) at the end of the experiment (P < 0.05). The heifers supplemented with LAS had a higher profitability than the CON heifers, even with the higher cost of the supplement containing LAS; this effect was due to the higher live BW at the end of the study. We concluded that the administration of a mineral supplement energy-type protein with added LAS has beneficial effects on beef heifers in terms of production and economic feasibility.

A meta-analysis of lasalocid effects on rumen measures, beef and dairy performance, and carcass traits in cattle.

The effects of lasalocid on rumen measures, beef and dairy performance, and carcass traits were evaluated using meta-analysis. Meta-regression was used to investigate sources of heterogeneity. Ten studies (20 comparisons) were used in the meta-analysis on rumen measures. Lasalocid increased total VFA and ammonia concentrations by 6.46 and 1.44 m, respectively. Lasalocid increased propionate and decreased acetate and butyrate molar percentage (M%) by 4.62, 3.18, and 0.83%, respectively. Valerate M% and pH were not affected. Meta-regression found butyrate M% linearly increased with duration of lasalocid supplementation (DUR; = 0.017). When >200 mg/d was fed, propionate and valerate M% were higher and acetate M% was lower ( = 0.042, = 0.017, and = 0.005, respectively). Beef performance was assessed using 31 studies (67 comparisons). Lasalocid increased ADG by 40 g/d, improved feed-to-gain ratio (F:G) by 410 g/kg, and improved feed efficiency (FE; combined measure of G:F and the inverse of F:G). Lasalocid did not affect DMI, but heterogeneity in DMI was influenced by DUR ( = 0.004) and the linear effect of entry BW ( = 0.011). The combination of ≤100 vs. >100 d DUR and entry BW ≤275 vs. >275 kg showed that cattle ≤275 kg at entry fed lasalocid for >100 d had the lowest DMI. Heterogeneity of ADG was influenced by the linear effect of entry BW ( = 0.028) but not DUR. Combining entry BW ≤275 vs. >275 kg and DUR showed that cattle entering at >275 kg fed ≤100 d had the highest ADG. The FE ( = 0.025) and F:G ( = 0.015) linearly improved with dose, and entry BW >275 kg improved F:G ( = 0.038). Fourteen studies (25 comparisons) were used to assess carcass traits. Lasalocid increased HCW by 4.73 kg but not dressing percentage, mean fat cover, or marbling score. Heterogeneity of carcass traits was low and not affected by DUR or dose. Seven studies (11 comparisons) were used to assess dairy performance but the study power was relatively low and the evidence base is limited. Lasalocid decreased DMI in total mixed ration-fed cows by 0.89 kg/d but had no effect on milk yield, milk components, or component yields. Dose linearly decreased DMI ( = 0.049). The DUR did not affect heterogeneity of dairy measures. This work showed that lasalocid improved ADG, HCW, FE, and F:G for beef production. These findings may reflect improved energy efficiency from increased propionate M% and decreased acetate and butyrate M%. Large dairy studies are required for further evaluation of effects of lasalocid on dairy performance.

Development of intramammary delivery systems containing lasalocid for the treatment of bovine mastitis: impact of solubility improvement on safety, efficacy, and milk distribution in dairy cattle.

BACKGROUND: Mastitis is a major disease of dairy cattle. Given the recent emergence of methicillin-resistant Staphylococcus aureus as a cause of bovine mastitis, new intramammary (IMA) treatments are urgently required. Lasalocid, a member of the polyether ionophore class of antimicrobial agents, has not been previously administered to cows by the IMA route and has favorable characteristics for development as a mastitis treatment. This study aimed to develop an IMA drug delivery system (IMDS) of lasalocid for the treatment of bovine mastitis. METHODS: Minimum inhibitory concentrations (MICs) were determined applying the procedures recommended by the Clinical and Laboratory Standards Institute. Solid dispersions (SDs) of lasalocid were prepared and characterized using differential scanning calorimetry and Fourier transform infrared spectroscopy. IMDSs containing lasalocid of micronized, nano-sized, or as SD form were tested for their IMA safety in cows. Therapeutic efficacy of lasalocid IMDSs was tested in a bovine model involving experimental IMA challenge with the mastitis pathogen Streptococcus uberis. RESULTS: Lasalocid demonstrated antimicrobial activity against the major Gram-positive mastitis pathogens including S. aureus (MIC range 0.5-8 µg/mL). The solubility test confirmed limited, ion-strength-dependent water solubility of lasalocid. A kinetic solubility study showed that SDs effectively enhanced water solubility of lasalocid (21-35-fold). Polyvinylpyrrolidone (PVP)-lasalocid SD caused minimum mammary irritation in treated cows and exhibited faster distribution in milk than either nano or microsized lasalocid. IMDSs with PVP-lasalocid SD provided effective treatment with a higher mastitis clinical and microbiological cure rate (66.7%) compared to cloxacillin (62.5%). CONCLUSION: Lasalocid SD IMDS provided high cure rates and effectiveness in treating bovine mastitis with acceptable safety in treated cows.

Assessment of probiotics supplementation via feed or water on the growth performance, intestinal morphology and microflora of chickens after experimental infection with Eimeria acervulina, Eimeria maxima and Eimeria tenella.

In this study, the effect of probiotic supplementation via drinking water or feed on the performance of broiler chickens experimentally infected with sporulated oocysts of Eimeria acervulina (5 × 10(4)), Eimeria maxima and Eimeria tenella (2 × 10(4) each one) at 14 days of age was evaluated. Two hundred and forty 1-day-old Ross 308 male chicks were separated into eight equal groups with three replicates. Two of the groups, one infected with mixed Eimeria oocysts and the other not, were given a basal diet and served as controls. The remaining groups were also challenged with mixed Eimeria species and received the basal diet and either water supplemented with probiotic (three groups) or probiotic via feed (two groups); the probiotic used consisted of Enterococcus faecium #589, Bifidobacterium animalis #503 and Lactobacillus salivarius #505 at a ratio of 6:3:1. Probiotic supplementation was applied either via drinking water in different inclusion rates (groups W1, W2 and W3) or via feed using uncoated (group FN) or coated strains (group FC). The last group was given the basal diet supplemented with the anticoccidial lasalocid at 75 mg/kg. Each experimental group was given the corresponding diet or drinking water from day 1 to day 42 of age. Throughout the experimental period of 42 days, body weight and feed intake were recorded weekly and feed conversion ratios were calculated. Seven days after infection, the infected control group presented the lowest weight gain values, while probiotics supplied via feed supported growth to a comparable level with that of the lasalocid group. Probiotic groups presented lesion score values and oocyst numbers that were lower than in control infected birds but higher than in the lasalocid group. In the duodenum, jejunum and ileum, the highest villous height values were presented by probiotic groups. In conclusion, a mixture of probiotic substances gave considerable improvement in both growth performance and intestinal health in comparison with infected control birds and fairly similar improvement to an approved anticoccidial during a mixed Eimeria infection.

Effects of lasalocid and intermittent feeding of chlortetracycline on the growth of prepubertal dairy heifers.

Forty Holstein heifers entered the 12-wk study at approximately 12 wk of age. At enrollment, heifers were blocked by birth date and assigned to 1 of 4 treatments: (1) carrier (30 g; control); (2) lasalocid + carrier (1 mg/kg of body weight; L); (3) chlortetracycline + carrier (22 mg/kg of body weight; CTC); (4) L + CTC + carrier (CTCL). Heifers on CTC and CTCL were provided treatment Monday through Friday and carrier only on Saturday and Sunday. These heifers were provided their respective treatment during wk 1 to 4, 6, and 10; wk 5, 7 to 9, and 11 to 12 heifers were provided the nonmedicated carrier. Heifers were individually fed a total mixed ration with treatments top-dressed at 1200 h daily. Dry matter intake was monitored for each heifer and feed provided was adjusted according to individual intakes. Skeletal measurements were taken weekly and blood samples were obtained every Monday, Wednesday, and Friday. Blood samples were analyzed for thyroxine concentration via radial immunoassay. Heifers supplemented with L had lower average daily gain , overall body weight gain, and trends for lower daily body length gain and overall girth gain compared with CTC heifers, but similar to control and CTCL heifers. Heifers fed L had lower hip height gain and overall hip height gain compared with CTCL heifers, but similar to control and CTC heifers. Heifers fed L had lower overall withers height gain compared with control heifers, but similar to CTC and CTCL heifers. No treatment effect on thyroxine concentrations was observed. These data indicate that L did not increase growth. Results from this experiment indicate that supplementing heifers with L was not beneficial and no benefits to supplementing heifers with CTC or the combination of CTC and L were evident compared with control heifers. Heifers in this study experienced minimal health problems and were regarded to be under low stress levels. Supplementing CTC and L may be beneficial to growing heifers under conditions where disease exposure and stressors are greater.

Determination of narasin and monensin in bovine, swine, and chicken tissues by liquid chromatography with tandem mass spectrometry: first action 2011.24.

The single-laboratory validation (SLV) of an LC-MS/MS method for determination and confirmation of two ionophores, narasin and monensin, in animal tissues is described. The data demonstrated linearity of matrix-matched calibration curves using a weighted (1/x) regression and selectivity of the method for narasin and monensin in the presence of lasalocid, salinomycin, maduramycin, nicarbazin, and sulfadiazine. Recoveries varied from 86.2 to 103.5% for narasin and 89.1 to 105.1% for monensin. Intertrial repeatability precision [relative standard deviation of repeatability (RSDr)] varied from 3.9 to 13.8% for narasin and 3.3 to 16.3% for monensin in fortified tissue. Precision of the method was verified in incurred tissues. The LOQ of the method was validated and ranged from 0.45 ng/g in milk, to 4.0 ng/g in chicken fat, but was 0.75 ng/g for most tissues. Two confirmatory ions for each analyte were examined across all matrixes, resulting in estimated false-negative rates of 0.00% (95% confidence interval of 0.00-0.68%) for monensin ions (540 samples) compared to the U.S. and European Union (EU) acceptance criteria. The confirmatory ions for narasin demonstrated 0.00% false-negative rates (95% confidence interval of 0.00-0.58%) when compared to either the U.S. or EU criteria in 630 samples. The method was robust when small changes in method parameters were made and stability of fortified tissues, extracts, and calibration solutions were estimated. The data satisfy the requirements of the AOAC Stakeholder Panel on Veterinary Drug Residue for SLV studies, and the method was adopted Official Methods of Analysis First Action 2011.24 by the AOAC Expert Review Panel on Veterinary Drug Residues.

Assessment of dietary supplementation with probiotics on performance, intestinal morphology and microflora of chickens infected with Eimeria tenella.

We evaluated the effects of dietary supplementation with different preparations of probiotics on the performance of broiler chickens experimentally infected with 2 × 10(4) sporulated oocysts of Eimeria tenella at 14 days of age. Three hundred, day-old, Cobb-500 chicks, as hatched, were separated into 10 equal groups with three replicates. Two of the groups, one challenged with E. tenella oocysts and the other not, were given a basal diet and served as controls without medication. The other challenged groups were given the anticoccidial lasalocid (60 mg/kg) or Enterococcus faecium (5 × 10(8) or 5 × 10(9)cfu/kg feed), Bifidobacterium animalis (5 × 10(8)cfu/kg feed), Lactobacillus reuteri (5 × 10(8)cfu/kg feed), Bacillus subtilis (5 × 10(8)cfu/kg feed), or a multi-species probiotic mix at 5 × 10(8) or 5 × 10(9)cfu/kg feed, respectively. The trial lasted 6 weeks. Individual body weight, feed intake per pen and feed conversion ratio values were recorded weekly, along with the extent of bloody diarrhea, excreta oocyst numbers and bird mortality. Caecal lesions were assessed and intestinal samples were taken for histopathological and bacteriological evaluation from ileum and caecum. Overall growth performance of chickens fed the multi-species probiotic mix at both levels was higher (P<0.05) compared to the infected control. Overall oocyst shedding was lowest (P<0.05) in the lasalocid supplemented group. Villous height was higher (P<0.05) in Bacillus supplemented groups compared to infected controls. The Lactobacillus supplemented group had the highest (P<0.05) numbers of both Lactobacillus and Bifidobacterium in ileum and caecum. In conclusion, dietary probiotics are promising for further investigation on improving intestinal health and growth performance of broiler chickens experimentally challenged with E. tenella.

Suplemento múltiplo com ionóforos para novilhos em pasto: desempenho / Multiple supplement with ionophores for grazing steers: performance

Avaliou-se o desempenho de 25 novilhos Holandês x Zebu, castrados, com média de peso vivo inicial de 265±50 kg, sob pastejo emBrachiaria decumbens, distribuídos em cinco grupos e em cinco piquetes, segundo os tratamentos: controle - suplementação múltipla sem ionóforos (CONT); suplementação múltipla com 100mg/cab/dia de monensina (M100); suplementação múltipla com 200mg/cab/dia de monensina (M200); suplementação múltipla com 100mg/cab/dia de lasalocida (L100); suplementação múltipla com 200mg/cab/dia de lasalocida (L200). O período experimental foi de 105 dias, com rotação dos grupos nos piquetes a cada 21 dias. A suplementação foi fornecida ad libitum. A avaliação de desempenho ocorreu mediante a pesagem dos animais, em jejum de alimento e água de 14 horas, no início de cada período e término do experimento. Os animais alimentados com suplementos com ionóforos apresentaram maior ganho de peso em relação aos do controle (0,357 vs. 0,268; P = 0,0068). Entre os ionóforos, os animais alimentados com lasalocida ganharam mais peso (0,398 vs. 0,333; P=0,0175). O melhor desempenho pode ser explicado pelo maior consumo dos suplementos pelos animais alimentados com lasalocida (0,53 vs. 0,42; P<0,0001).

The performance of 25 castrated Holstein x Zebu crossbred steers averaging 265±50kgBW, grazing on Brachiaria decumbens, during dry season was evaluated. The experiment was carried out in a completed randomized design and the animals were grouped in five different paddocks with the following treatments: control - multiple supplement without ionophores (CONT); multiple supplement with 100mg of monensin/animal/day (M100); multiple supplement with 200mg of monensin/animal/day (M200); multiple supplement with 100mg of lasalocid/animal/day (L100); and multiple supplement with 200mg of lasalocid/animal/day (L200). The experimental period was 105 days, with changing groups on paddocks every 21 days. The multiple supplement was offered ad libitum. Body weight was evaluated after 14 hours of fasting. Animals fed multiple supplement with ionophores showed higher average daily weight gain than control (0.357 vs 0.268; P= 0.0068), as well as steers fed lasalocid in comparision to monensin (0.398 vs. 0.333; P= 0.0175). Animals suplemented with lasalocid had higher intakes and higher average daily gain (0.53 vs. 0.42; P<0.0001).

Suplemento múltiplo com ionóforos para novilhos em pasto: consumo, fermentação ruminal e degradabilidade in situ / Multiple supplement with ionophores for grazing steers: intake, ruminal fermentation, and in situ degradability

Avaliou-se o efeito do suplemento múltiplo com ionóforos sobre o consumo, a fermentação ruminal e a degradabilidade in situ da matéria seca da forragem. Utilizaram-se cinco novilhos Holandês x Zebu fistulados no rúmen, com peso vivo médio de 350kg, em delineamento em quadrado latino. Os tratamentos foram: suplementação múltipla sem ionóforos (CONT); suplementação múltipla com 100mg/cab/dia de monensina (M100); suplementação múltipla com 200mg/cab/dia de monensina (M200); suplementação múltipla com 100mg/cab/dia de lasalocida (L100); e suplementação múltipla com 200mg/cab/dia de lasalocida (L200). O uso de ionóforos no suplemento não influenciou o consumo de forragem, que foi, em média, 7,24kg MS/dia. A presença de ionóforos resultou em ligeiro aumento do pH ruminal em relação à ausência desses aditivos (P<0,05). Houve diferença na concentração do N-NH3 apenas para os teores de ionóforos em que 200mg/cab/dia reduziu a quantidade de N-NH3. As concentrações de acetato, propionato e butirato não foram influenciadas pela inclusão, pelo tipo ou pelos teores de ionóforos. A fração solúvel média (A) da Brachiaria decumbens foi igual a 22 por cento, e a fração insolúvel potencialmente degradável média (B) igual a 65 por cento, resultando em degradação potencial média de 87 por cento. A taxa de degradação média (c) foi de 0,03/hora. Os ionóforos não alteraram a degradação in situ da matéria seca.

The effect of multiple supplement with ionophores was evaluated on intake, ruminal fermentation, and in situ degradability of dry matter (DM) of the pasture forage. Five rumen fistulated Holstein x Zebu steers averaging 350kg of BW were used. The animals were grouped in five different paddocks under Latin Square experimental design. The treatments were multiple supplement without ionophores (CONT); multiple supplement with 100mg of monensin/animal/day (M100); multiple supplement with 200mg of monensin/animal/day (M200); multiple supplement with 100mg of lasalocid/animal/day (L100); multiple supplement with 200mg of lasalocid/animal/day (L200). The pasture intake was 7.24kg DM/day and it was not affected by ionophores. The average pH was influenced (P<0.05) by the presence of the ionophores in the supplements. There rumen N-NH3 concentration was negatively influenced by the ionophores levels in the multiple supplement. The molar concentrations of acetate, propionate, and butirate in the rumen were not affect by the presence, type, or level of ionophores. The mean soluble fraction A of Brachiaria decumbens was 22 percent, the mean potential degradable insoluble fraction (B) was 65 percent, and the degradability was 87 percent. The mean degradation rate (c) was 0.03/h. The ionophores did not affect DM in situ degradability.

Determination of lasalocid sodium in animal feeds and premixes by reversed-phase liquid chromatography: collaborative study.

A liquid chromatographic (LC) method for the analysis of lasalocid sodium in premixes, complete animal feeds, and trace-level feeds was collaboratively studied. The method employs a 0.5% HCI acidified methanol extraction followed by 20 min sonication in a water bath heated to 40 degrees C. Samples are then shaken on a mechanical shaker for 1 h and stored overnight, followed by an additional 10 min shaking the following morning. Sample extracts are diluted if necessary with extractant, filtered, and injected onto an LC system. Determination of all lasalocid homologs is by reversed-phase LC with fluorescence detection at 314 nm excitation and 418 nm emission. Eight samples of drug premixes, medicated feeds, and mineral supplements, along with 2 samples for trace-level analysis were sent to 20 collaborators in the United States, Canada, and The Netherlands. Study data were returned by 17 laboratories. Two additional supplemental trace-level samples and a blank feed were provided to 15 of the collaborating laboratories, and test data were received from all 15 participants. For the drug premixes, medicated feeds, and mineral supplements, RSDr values (within-laboratory repeatability) ranged from 1.2 to 19.9%, RSDR values (among-laboratory reproducibility) ranged from 3.4 to 32.3%, and HorRat values ranged from 0.35 to 3.73. For the trace-level samples, only lasalocid A, the predominant homolog comprising > 90% of the sum of all homolog peak area, was quantified. All laboratories correctly identified the analyte. Although some instrument response was reported by a number of laboratories for the blank feed, all but one laboratory's results were well below the 1 mg/kg limit of quantification. RSDr values for the initial 2 trace-level samples were excessive, ranging from 51.6 to 64.4%. RSDR values ranged from 51.6 to 75.7%, and HorRat values ranged from 3.6 to 4.0. Data for the initial trace-level samples indicated that the test samples were improperly prepared to ensure homogeneity, and a new set of supplemental samples was provided to collaborators, with significantly improved results. RSDr values for the 2 supplemental trace-level samples ranged from 1.6 to 2.5%, RSDR values ranged from 5.6 to 9.2%, and HorRat values ranged from 0.43 to 0.62.

Effects of lasalocid or monensin supplementation on digestion, ruminal fermentation, blood metabolites, and milk production of lactating dairy cows.

Six ruminally fistulated midlactating multiparous Holstein cows were used in a double 3 x 3 Latin square design (35-d periods) to study the effects of lasalocid (LAS) and monensin (MON) supplemented at 24 mg/ kg of dry matter on digestion, ruminal fermentation, blood metabolites, and milk production. Cows were blocked according to milk production and fed a red clover silage-based total mixed ration (17.8% crude protein) without supplementation or supplemented with LAS or MON. Daily dry matter intake, milk production, and milk fat and protein concentrations were similar among treatments and averaged 23.5 kg, 36.6 kg, 3.36%, and 3.38%, respectively. Rumen lipogenic:glucogenic volatile fatty acids and NH(3)-N concentration were lower, and apparent digestibility of dry matter, organic matter, crude protein, and gross energy were higher with than without ionophore supplementation. Compared with LAS, MON increased concentrations of plasma urea-N and milk urea-N, and excretion of urinary urea-N and total N. Monensin also decreased N retention and tended to reduce plasma concentration of nonessential AA in comparison with LAS. Both ionophores reduced daily fecal excretion of N by 13 g compared with the control, but MON increased daily losses of urinary N by 36 g compared with LAS. Results from this study suggest that postabsorptive metabolism of N might be altered by the type of ionophore fed.

Changes in net portal nutrient flux in response to weaning transition and ionophore supplementation in dairy calves.

Dairy calf weaning is associated with ketone concentrations that exceed the levels occurring in adults, and weaning represents a potential energy loss that may be mitigated by ionophore supplementation. To assess the effects of weaning and ionophore supplementation on net nutrient flux across portal-drained viscera (PDV) tissues in dairy calves, concentrations of glucose, acetoacetate (ACAC), beta-hydroxybutyrate (BHBA), nonesterified fatty acids, volatile fatty acids, lactate, pyruvate, insulin, and glucagon and PDV flux rates were determined in Jersey bull calves (n = 19) at 35, 56, 84, and 112 d of age. Calves were randomly assigned at birth to either a commercial pelleted starter without (CON) or with lasalocid (TRT; 83 mg/kg of dry matter). Calves were fed only milk replacer from d 3 to 34 (d 3 to 20 = 454 g/d; d 21 to 34 = 568 g/d). After blood sampling on d 35, calves received replacer (d 35 to 41 = 454 g/d; d 42 to 48 = 227 g/d) and had free access to the CON or TRT starter, and from d 49 to 112 they received CON or TRT ad libitum. Catheters were implanted in the portal vein and in the mesenteric vein and artery between d 21 and 28. Blood flow was measured by continuous infusion of p-aminohippurate into the mesenteric vein. Six serial samples were taken at 30-min intervals from the arterial and portal vein catheters simultaneously. Portal blood flow increased with age but did not differ between CON and TRT calves. Glucose was released preweaning and was extracted postweaning by PDV, but was not affected by ionophore. The portal flux of nonesterified fatty acids was not different from zero during any of the 4 sample ages. Fluxes of ACAC and BHBA in CON and TRT calves went from no measurable flux preweaning to a postweaning PDV release that peaked at d 84, but the d-84 release of ACAC and BHBA was lower in TRT calves. The portal flux of volatile fatty acids increased with age, and PDV release of both butyrate and propionate was lower at d 84 in TRT than in CON calves. However, TRT calves had a greater PDV release of lactate on d 84, partially compensating for the lower release of propionate. Glucagon was greater in CON than in TRT calves at d 84 and could be a response to the elevated ketogenesis observed in CON calves during this period. Changes in the metabolic profile and nutrient flux of transition calves were demonstrated in response to weaning and ionophore supplementation. Inclusion of an ionophore appeared to moderate alimentary output at a postweaning period (d 84) at which ketone concentrations have the potential to exceed the whole animal capacity for utilization.

Effects of weaning and ionophore supplementation on selected blood metabolites and growth in dairy calves.

Dairy calf weaning results in blood ketone concentrations in excess of mature rates of use and can result in excretion of ketones in urine representing a loss of energy. Lasalocid is frequently supplemented as an anticoccidial agent in calf starters; however, in mature ruminants it is known to alter molar ratios of ruminal volatile fatty acids (VFA). Effects of weaning transition and postweaning ionophore supplementation on body weight, dry matter (DM) intake, average daily gain (ADG), and blood concentrations of glucose, acetoacetate, beta-hydroxybutyrate (BHBA), lactate, pyruvate, nonesterified fatty acids (NEFA), VFA, insulin, and glucagon were examined using Jersey bull calves (n = 24) over 16 wk. Calves were blocked into groups of 2 according to birth date and weight and randomly assigned to receive either a commercial pelleted starter (control), or the same diet containing lasalocid (TRT; 83 mg/kg of DM). Calves were fed milk replacer from d 3 to 34 (d 3 to 20 = 454 g/d at 12% solids; d 21 to 34 = 568 g/d at 15% solids), from d 35 to 48 calves received both replacer (d 35 to 41 = 454 g/d; d 42 to 38 = 227 g/d) and free access to control or TRT starter, and from d 49 to 112 received ad libitum control or TRT. Body weight and jugular blood metabolite concentrations were measured and recorded weekly. Postweaning DM intake, average daily gain, and feed:gain did not differ between control and TRT calves. Glucose and NEFA concentrations did not differ between control and TRT, but declined with age. Insulin and glucagon concentrations did not differ between control and TRT, but glucagon concentrations increased with weaning. Total VFA significantly increased following introduction of solid feed at d 35 in both groups with an apparent 1-wk lag in TRT VFA increases compared with control. Jugular acetate and butyrate concentrations were greater in control calves than TRT calves during wk 7. Propionate concentrations did not differ between control and TRT at any time following weaning. Blood BHBA concentrations were greater in control than TRT during wk 8 and 9. Thus, consumption of starter supplemented with lasalocid delayed peak acetate and butyrate and lowered peak BHBA concentrations. However, supplementation at concentrations currently recommended for control of coccidiosis did not appear to be sufficient to enhance growth or efficiency during the wk 7 to 16 postweaning interval for this sample size.

An alternative to antibiotic-based drugs in feed for enhancing performance of broilers grown on Eimeria spp.-infected litter.

Three trials were conducted to evaluate the effects of lasalocid, an anticoccidial feed additive (90.7 kg/ton); bacitracin, a growth-promoter (50 g/ton); and yeast culture residue (YCR) (1 kg/ton) on the performance of broiler chicks reared to 42 d of age on recycled litter. Recycled litter consisted of pine wood shavings containing droppings from chicks infected with 3 select strains of coccidia (Eimeria tenella, Eimeria maxima, and Eimeria acervulina). Response variables (BW, intestinal tract and litter coliform counts, cecal and liver relative weights, and litter moisture content) were recorded biweekly. Mean BW of chicks fed the diet supplemented with YCR was higher than that of the controls (P < 0.05) and comparable to that of the lasalocid-treated birds in all 3 trials. Mean BW of chicks in all treatment groups decreased uniformly as the litter aged and moisture content increased. The mean intestinal coliform population from YCR-treated chicks was lower (P < 0.05) than those of the control and lasalocid populations. The coliform count was consistently lower than that in chicks on a bacitracin-supplemented diet. Coliform counts from the control and lasalocid-treated birds did not differ. The litter coliform counts increased with increased use of the litter. Cecal and liver relative weights calculated from the chicks in trial 3 showed that only the liver was significantly affected by treatments. YCR appeared to be a viable alternative to bacitracin and lasalocid medication in enhancing growth of broiler chicks reared on recycled litter.

Effect of dietary supplementation with oregano essential oil on performance of broilers after experimental infection with Eimeria tenella.

A study was carried out to examine the effect of dietary supplementation of oregano essential oil on performance of broiler chickens experimentally infected with Eimeria tenella at 14 days of age. A total of 120 day-old Cobb-500 chicks separated into 4 equal groups with three replicates each, were used in this study. Two groups, one infected with 5 x 10(4) sporulated oocysts of E. tenella and the other not, were given a basal diet and served as controls. The other two groups also infected with E. tenella were administered diets supplemented with oregano essential oil at a level of 300 mg/kg, or with the anticoccidial lasalocid at 75 mg/kg. Following this infection, survival rate, bloody diarrhoea and oocysts excretion as well as lesion score were determined. Throughout the experimental period of 42 days, body weight gain and feed intake were recorded weekly, and feed conversion ratios were calculated. Two weeks after the infection with E. tenella supplementation with dietary oregano oil resulted in body weight gains and feed conversion ratios not differing from the non-infected group, but higher than those of the infected control group and lower than those of the lasalocid group. These parameters correspond with the extent of bloody diarrhoea, survival rate, lesion score and oocyst numbers and indicated that oregano essential oil exerted an anticoccidial effect against E. tenella, which was, however, lower than that exhibited by lasalocid.