O consumo na dose correta e principalmente na frequência adequada são as principais dificuldades do fornecimento de ionóforos para animais em dietas com elevado teor de volumoso. O objetivo do estudo foi avaliar o efeito da frequência do fornecimento de narasina no desempenho (Exp. I), parâmetros de fermentação ruminal, digestibilidade aparente dos nutrientes e balanço de nitrogênio (Exp. II) em ovinos alimentados com dietas contendo elevado teor de volumoso. As dietas experimentais foram compostas por 95% de feno de coastcros e 5% de milho moído. Os tratamentos utilizados foram: Controle (C): fornecimento do concentrado uma vez ao dia sem ionóforo, Narasina 24 horas (N24): fornecimento diário de narasina na dosagem de 13 mg de narasina /kg de MS, Narasina 48 horas (N48): fornecimento de narasina a cada 48 horas (dias alternados), sendo no primeiro dia ofertado 26 mg de narasina/kg de MS e no segundo dia foi fornecido apenas o milho moído (média receberam 13 mg de narasina/kg de MS), Narasina 72 horas (N72): fornecimento de narasina a cada 72 horas, sendo no primeiro dia ofertado 39 mg de narasina/kg de MS, já no segundo e terceiro dia fornecido apenas o milho moído sem ionóforo. As análises estatísticas foram realizadas utilizando o procedimento MIXED do SAS (2002) e considerado efeito significativo quando P 0,05. Experimento I: Foram utilizados 44 cordeiros (33,31 ± 0,59 kg), sendo o delineamento experimental de blocos completos casualizados, com a duração de 105 dias. Não houve efeito para o CMS (P = 0,28), no entanto, a inclusão de narasina diariamente (N24) e a cada 48 horas (N48) aumentou o GMD dos animais (P = 0,03) e a EA (P = 0,02). Experimento II: Foram utilizados quatro borregos (Dorper x Santa Inês, castrados e providos de cânulas ruminais). O delineamento experimental utilizado foi o quadrado latino 4 x 4. O experimento teve duração total de 144 dias, divididos em quatro períodos de trinta e seis dias. Em cada período os doze primeiros dias foram utilizados como wash-out, do 13° ao 36° dia os animais receberam as dietas experimentais, a colheitas de dados (total de fezes, urina e de fluido ruminal) foram realizadas nos seis últimos dias de cada período. Não houve efeito na digestibilidade da MS e do FDN, os tratamentos N24 e N48 aumentaram a concentração molar de 11 propionato (P < 0,01), a concentração total de AGCC (P < 0,01) e diminuiu a relação acetato:propionato (P < 0,01). Com base nos dados obtidos é possível concluir que os tratamentos N24 e N48 aumentaram o peso final dos cordeiros, e alterou positivamente fermentação ruminal dos ovinos, por outro lado, a narasina mostrou diminuição na sua capacidade como moduladora da fermentação ruminal no intervalo de fornecimento maior que dois dias (72 horas/N72). / The intake on the correct dosage and frequency are the main difficulties of supplying ionophores for animals on high forage diets. Therefore, the aim of this study was to evaluate the frequency of supplementation of narasin over performance (Exp. I), ruminal fermentation parameters, nutrient apparent digestibility and nitrogen balance (Exp. II) on sheep fed high forage diets. The experimental diets consisted on 95% coastcross hay and 5% ground corn used as a delivery vehicle of the additive. The treatments were: Control (C): daily supply of concentrate without the ionophore; narasin 24 hours (N24): daily supply of 13 mg of narasin/kg of DM; narasin 48 hours (N48): supply of narasin every 48 hours (every other day), being provided 26 mg of Narasin/kg of DM on the first day and only the ground corn on the second day (an average of 13 mg of narasin/kg of DM); narasin 72 hours (N72): supply of narasin every 72 hours (one day receiving the additive followed by two days without receiving it), being provided 39 mg of narasin/kg of DM on the first day and only the ground corn on the second and third days. The statistical analysis was done using the MIXED procedure on SAS (2002) and the effects were considered significant when P 0.05. Experiment I: Were used 44 lambs (33.31 ± 0.59 kg) in a randomized block experimental design, the trial lasted 105 days. There was no effect for DMI (P = 0.28), the daily inclusion of narasin (N24) and every 48 hours (N48) increased the ADG (P = 0.03) and the FE (P < 0.01). Experiment II: Were used 4 male lambs (Dorper x Santa Inês, castrated and cannulated in the rumen) in a 4 x 4 Latin square experimental design. The trial lasted 144 days, divided in 4 periods of 36 days each. The first twelve days of each period were used as wash-out, from the 13th to the 36th day the animals received the experimental diets, and the data collection (feces, urine and ruminal fluid) were done on the last six days of each period. . It was not the effect on the digestibility of DM (P = 0.30) and NDF (P = 0.14). The daily inclusion of narasin (N24) and every 48 hours (N48) increased the molar concentration of propionate (P < 0.01), the total concentration of SCFA (P <0.01) and reduced the acetate to propionate (acetate:propionate ratio) ratio (P < 0.01). Based on this data it was possible to 13 conclude that the daily supply of narasin (N24) and every 48 hours (N48) affected the performance and ruminal fermentation parameters on sheep, but this effects decreased when intervals bigger than 48 hours (N72) were used.

O consumo na dose correta e principalmente na frequência adequada são as principais dificuldades do fornecimento de ionóforos para animais em dietas com elevado teor de volumoso. O objetivo do estudo foi avaliar o efeito da frequência do fornecimento de narasina no desempenho (Exp. I), parâmetros de fermentação ruminal, digestibilidade aparente dos nutrientes e balanço de nitrogênio (Exp. II) em ovinos alimentados com dietas contendo elevado teor de volumoso. As dietas experimentais foram compostas por 95% de feno de coastcros e 5% de milho moído. Os tratamentos utilizados foram: Controle (C): fornecimento do concentrado uma vez ao dia sem ionóforo, Narasina 24 horas (N24): fornecimento diário de narasina na dosagem de 13 mg de narasina /kg de MS, Narasina 48 horas (N48): fornecimento de narasina a cada 48 horas (dias alternados), sendo no primeiro dia ofertado 26 mg de narasina/kg de MS e no segundo dia foi fornecido apenas o milho moído (média receberam 13 mg de narasina/kg de MS), Narasina 72 horas (N72): fornecimento de narasina a cada 72 horas, sendo no primeiro dia ofertado 39 mg de narasina/kg de MS, já no segundo e terceiro dia fornecido apenas o milho moído sem ionóforo. As análises estatísticas foram realizadas utilizando o procedimento MIXED do SAS (2002) e considerado efeito significativo quando P 0,05. Experimento I: Foram utilizados 44 cordeiros (33,31 ± 0,59 kg), sendo o delineamento experimental de blocos completos casualizados, com a duração de 105 dias. Não houve efeito para o CMS (P = 0,28), no entanto, a inclusão de narasina diariamente (N24) e a cada 48 horas (N48) aumentou o GMD dos animais (P = 0,03) e a EA (P = 0,02). Experimento II: Foram utilizados quatro borregos (Dorper x Santa Inês, castrados e providos de cânulas ruminais). O delineamento experimental utilizado foi o quadrado latino 4 x 4. O experimento teve duração total de 144 dias, divididos em quatro períodos de trinta e seis dias. Em cada período os doze primeiros dias foram utilizados como wash-out, do 13° ao 36° dia os animais receberam as dietas experimentais, a colheitas de dados (total de fezes, urina e de fluido ruminal) foram realizadas nos seis últimos dias de cada período. Não houve efeito na digestibilidade da MS e do FDN, os tratamentos N24 e N48 aumentaram a concentração molar de 11 propionato (P < 0,01), a concentração total de AGCC (P < 0,01) e diminuiu a relação acetato:propionato (P < 0,01). Com base nos dados obtidos é possível concluir que os tratamentos N24 e N48 aumentaram o peso final dos cordeiros, e alterou positivamente fermentação ruminal dos ovinos, por outro lado, a narasina mostrou diminuição na sua capacidade como moduladora da fermentação ruminal no intervalo de fornecimento maior que dois dias (72 horas/N72). / The intake on the correct dosage and frequency are the main difficulties of supplying ionophores for animals on high forage diets. Therefore, the aim of this study was to evaluate the frequency of supplementation of narasin over performance (Exp. I), ruminal fermentation parameters, nutrient apparent digestibility and nitrogen balance (Exp. II) on sheep fed high forage diets. The experimental diets consisted on 95% coastcross hay and 5% ground corn used as a delivery vehicle of the additive. The treatments were: Control (C): daily supply of concentrate without the ionophore; narasin 24 hours (N24): daily supply of 13 mg of narasin/kg of DM; narasin 48 hours (N48): supply of narasin every 48 hours (every other day), being provided 26 mg of Narasin/kg of DM on the first day and only the ground corn on the second day (an average of 13 mg of narasin/kg of DM); narasin 72 hours (N72): supply of narasin every 72 hours (one day receiving the additive followed by two days without receiving it), being provided 39 mg of narasin/kg of DM on the first day and only the ground corn on the second and third days. The statistical analysis was done using the MIXED procedure on SAS (2002) and the effects were considered significant when P 0.05. Experiment I: Were used 44 lambs (33.31 ± 0.59 kg) in a randomized block experimental design, the trial lasted 105 days. There was no effect for DMI (P = 0.28), the daily inclusion of narasin (N24) and every 48 hours (N48) increased the ADG (P = 0.03) and the FE (P < 0.01). Experiment II: Were used 4 male lambs (Dorper x Santa Inês, castrated and cannulated in the rumen) in a 4 x 4 Latin square experimental design. The trial lasted 144 days, divided in 4 periods of 36 days each. The first twelve days of each period were used as wash-out, from the 13th to the 36th day the animals received the experimental diets, and the data collection (feces, urine and ruminal fluid) were done on the last six days of each period. . It was not the effect on the digestibility of DM (P = 0.30) and NDF (P = 0.14). The daily inclusion of narasin (N24) and every 48 hours (N48) increased the molar concentration of propionate (P < 0.01), the total concentration of SCFA (P <0.01) and reduced the acetate to propionate (acetate:propionate ratio) ratio (P < 0.01). Based on this data it was possible to 13 conclude that the daily supply of narasin (N24) and every 48 hours (N48) affected the performance and ruminal fermentation parameters on sheep, but this effects decreased when intervals bigger than 48 hours (N72) were used.

Due to the increasing cost of soybean meal and concerns of excess N being excreted into the environment, new protein supplements have been developed. Two products that have shown potential in increasing N utilization efficiency are slow release urea (SRU; Optigen) and ruminal escape protein derived from yeast (YMP; DEMP). The objective of this study was to assess the effects of feeding these 2 supplements in high-forage [(54% of total dietary dry matter (DM)] dairy diets on nutrient utilization, feed efficiency, lactational performance of dairy cows, and their impacts on income-over feed costs. Twelve multiparous dairy cows were used in a triple 4 × 4 Latin square design with one square consisting of ruminally cannulated cows. Treatments included: 1) control, 2) SRU-supplemented total mixed ration (TMR, SRUT), 3) YMP-supplemented TMR (YMPT), and 4) SRU and YMP-supplemented TMR (SYT). The control consisted only of a mixture of soybean meal and canola meal (SBMCM) in a 50:50 ratio. The SRU and the YMP were supplemented at 0.49% and 1.15% DM, respectively. The experiment consisted of 4 periods lasting 28 d each (21 d of adaptation and 7 d of sampling). Cows fed YMPT and SYT had decreased intake of DM, and all supplemented treatments had lower crude protein intake compared to those fed the control. Milk yield tended to have the greatest increase in YMPT compared with the control (41.1 vs. 39.7 kg/d) as well as a tendency for increased milk fat and protein yields. Feed efficiencies based on yields of milk, 3.5% fat-corrected milk, and energy-corrected milk increased at 10-16% due to protein supplementation. Cows fed with protein supplements partitioned less energy toward body weight gain, but tended to partition more energy toward milk production. Efficiency of use of feed N to milk N increased by feeding SRUT and YMPT, and milk N-to-manure N ratio increased in YMPT. Cows fed SRUT or YMPT tended to improve income-over feed costs. Overall results from this experiment indicate that replacing SBMCM with SRU and YMP in high-forage dairy diets can be a good approach to enhance dairy profitability through improved nutrient utilization efficiencies by lactating dairy cows.

Methane is a potent greenhouse gas with a global warming potential 21 times that of carbon dioxide. Globally, ruminants are the main anthropogenic contributors to methane release to the atmosphere. Methane is produced in the gastrointestinal tract of ruminants, mostly within the rumen by methanogenic archaea. However, methane production represents a loss of 2 to 12% of dietary gross energy for the animal, which could otherwise be available for growth or milk production. Therefore, mitigation of methane production by ruminants could produce both economic and environmental benefits, with more sustainable and energy efficient livestock, and offering a promising way of slowing global warming. Despite extensive research undertaken to find ways of reducing methane emissions from ruminants, progress has been relatively limited. Furthermore, there is still a lack of studies linking rumen microbiology and ruminant nutrition and production. The central purpose of this research was to investigate feed additives to reduce methane emissions and to understand associated changes that occur in the rumen microbiota. For the first experiment (Chapter 2), biochar was evaluated as an antimethanogenic compound for beef cattle. The in vitro gas production technique was used to study the effects of biochar on rumen fermentation and methane production. Overall, methane production was reduced by 5% by the addition of biochar compounds (10 g/kg of substrate). The observed reduction in methane produced was not associated with a change in volatile fatty acid profile suggesting biochar primarily inhibited fermentation. Ammonia concentration was significantly reduced with biochar inclusion. Because different biochars had different effects on methane production, further investigation of relationships between the physicochemical properties of biochars and antimethanogenic effects are necessary. However, due to the small reduction in methane production recorded, research with biochar was discontinued. Encapsulated nitrate was then explored as an antimethanogenic additive and as an alternative non-protein nitrogen source to urea (Chapter 3). The effect of using encapsulated nitrate as a replacement for urea or dietary protein, plus the addition of inorganic sulphur, on enteric methane emissions, nutrient digestibility, nitrogen utilization and microbial protein synthesis from crossbred beef steers were studied. In addition, nitrate toxicity and eating behaviour were investigated. The inclusion of encapsulated nitrate reduced methane production compared to urea and a true protein source, with no adverse effects on rumen fermentation or nitrogen metabolism and no effects with the inclusion of elemental sulphur. The level of addition of encapsulated nitrate (14.3 g nitrate /kg DM) and the time of adaptation chosen for this study (14 days) were adequate to avoid nitrate toxicity. Finally, the effects of adding nitrate inclusion to different basal diets on rumen microbial populations and relationships of these populations with methane production were investigated (Chapter 4). The V4 hypervariable regions of the bacterial and archaea 16S rRNA genes were amplified and sequenced. Effects on microbial population induced by nitrate were dependant on the basal diet but nitrate altered specific archaeal and bacterial OTUs consistently between studies. A direct and strong correlation between some archaea taxonomic groups and OTUs with methane production was observed.