Nitrogen excreted by ruminants may negatively impact the environment, and N not retained is not utilized for growth and production. Experiments were conducted to examine the effect of 48 h oscillation of two levels of low ruminally degradable dietary CP on N metabolism in lambs and performance of steers. In Exp. 1, a metabolism trial was conducted with 28 lambs (31 kg), allotted to four different diets: 8% CP, 10% CP, 12% CP, and 8% and 12% CP diets oscillated every 48 h. After adaptation, transition, and preliminary periods, feces and urine were collected for 10 d. Ruminal fluid and blood samples were taken at the end of collection and again 2 d later. In Exp. 2, 24 crossbred steers (228 kg) were allotted to four diets: 1) 7.5% CP, 2) 9% CP, 3) 10.5% CP, and 4) 7.5% and 10.5% CP diets oscillated every 48 h. Feed intake was measured during the 112 d study, and ADG and gain to feed ratio were calculated. Cattle were weighed every 14 d and blood samples were taken every 28 d. In Exp. 1, N retention was lowest (P < 0.05) for the lambs fed the 8% CP diet, with no differences among lambs fed the other diets. Differences in urinary N excretion accounted for most of the differences in total N excretion. Ruminal NH3-N and BUN levels were greater in animals fed higher amounts of CP. Ruminal pH and VFA concentrations were not affected by diet. In Exp. 2, feed intake did not differ among steers fed different diets. Average daily gain was lowest for cattle fed the 7.5% CP diet. No significant difference was evident for ADG between steers fed the 7.5/10.5% CP oscillating diet and those fed the 9% or the 10.5% CP diet. Gain to feed ratio was lower (P < 0.05) for steers fed the 7.5% CP diet compared to steers fed all other diets. Blood urea N level was higher for cattle fed the 10.5% CP diet than those fed the two lower CP levels, and differences were usually significant (P < 0.05). No consistent significant difference in BUN levels existed between steers fed the 7.5/10.5% CP oscillating diet and those fed the 9% and 10.5% CP diets continuously. Oscillating two levels of low ruminally degradable dietary CP every 48 h had no significant effect on N retention in lambs nor on the performance of steers compared to animals fed the same level of CP daily in these experiments. / Master of Science

Dois experimentos foram conduzidos com o intuito de avaliar os efeitos da suplementação com diferentes aditivos, sobre o consumo e ganho de peso, em bovinos mantidos em pastagem durante o período das águas. No experimento I, 48 novilhas Nelore, com 266 kg de peso vivo médio inicial, foram distribuídas no delineamento experimental inteiramente casualizado, em quatro tratamentos, sendo cada animal considerado uma unidade experimental. Os tratamentos foram arranjados em esquema fatorial 2 x 2, com dois tipos de suplemento (suplemento mineral e mineral protéico energético) e dois níveis de monensina (0 e 1200 ppm em suplemento mineral, 0 e 60 ppm em mineral protéico energético). No experimento II, foram utilizados 60 bezerros Nelore, com peso vivo médio inicial de 300 kg. Os animais foram distribuídos em um delineamento inteiramente casualizado em quatro tratamentos com 15 animais cada. Os animais foram submetidos aos tratamentos: com suplemento mineral (controle), suplemento mineral com virginiamicina (1333 ppm), suplemento mineral com salinomicina (1111 ppm) e suplemento mineral com monensina (1000 ppm). Em ambos os experimentos, os animais foram alocados em quatro piquetes de Brachiaria decubens, com 6,7 hectares cada, e eram rotacionados semanalmente. As análises estatísticas foram feitas utilizando o programa estatístico SAS. No experimento I, o consumo do suplemento mineral protéico energético, com e sem monensina, foi maior em relação aos demais tratamentos (P&lt;0,05) e a monensina não provocou uma queda siginificativa no consumo dos suplementos. Os animais que receberam o suplemento mineral protéico energético ganharam mais peso do que os animais que receberam o suplemento mineral (P&lt;0,05), não havendo influencia da monensina sobre o ganho de peso. No experimento II, a monensina promoveu uma redução no consumo em relação ao grupo controle (P&lt;0,06). O suplemento com virginiamicina não afetou o consumo aos 56 dias, mas os suplementos com salinomicina e monensina reduziram o consumo em relação ao controle (P&lt;0,05). Não houve diferença siginificativa no consumo entre os tratamentos aos 28 dias e aos 84 dias, porém houve uma redução no consumo de todos os suplementos. O ganho de peso diário entre os animais que consumiram os aditivos não apresentaram diferenças significativas, mas os tratamentos com virginiamicina e salinomicina proporcionaram ganhos maiores do que o tratamento controle. A virginiamicina e a salinomicina ocasionaram um aumento no ganho de peso, e a salinomicina e a monensina reduziram o consumo. / Two experiments were conducted to evaluate the effects of the supplementation with different feed additives on feed intake and average daily gain for grazing Nellore bovines during the rainy season. On the experiment I, 48 Nellore heifers (266 kg BW) were distributed in four treatments, and each animal was considered one experimental unit. The treatments were organized in a factorial 2x2, two types of supplements (mineral supplement and mineral protein-energy supplement) and two levels of monensin (0 and 1200 ppm in the mineral supplement, 0 and 60 ppm in the mineral protein- energy supplement). In the study II, 60 Nellore calves of 300 kg (BW) were distributed in 4 treatments of 15 animals each. Treatments consisted of the inclusion of: mineral supplement (control treatment), mineral supplement with virginiamycin (1333ppm), mineral supplement with salinomycin (1111 ppm) e mineral supplement with monensin (1000ppm). In both studies, animals were allocated in four rotational stocking areas (6,7 hectares each area) of Brachiariadecubens. Statistical analyses were conducted using the software SAS. In the experiment I, the consumption of the mineral proteic supplement, with and without monensin, was higher compared to the others treatments (P&lt;0.05) and the monensin did not cause any significant decrease on the supplement intake. Animals who received protein mineral supplement had higher average daily gain than animals who received mineral supplement (P&lt;0.05) and there was no effect of monensin on the weight gain. In the experiment II, the inclusion of monensin reduced the consumption compared to the control treatment (P&lt;0.06). The supplement with virginiamycin did not affect the consumption on the day 56, however the supplements with salinomycin and monesin reduced the consumption compared to the control treatment (P&lt;0.05). The average daily gain was statically different among treatments on the days 28 and 84, however there was a reduction on consumption of all treatments. The average daily gain among animals supplemented with different feed additives did not differ statically, but the treatments with the inclusion of virginiamycin and salinomycin had higher gains than the control treatment. The virginiamycin anda salinomycin caused increase weight gain and the salinomycin and monensin reduced the consume.

Dois experimentos foram conduzidos com o intuito de avaliar os efeitos da suplementação com diferentes aditivos, sobre o consumo e ganho de peso, em bovinos mantidos em pastagem durante o período das águas. No experimento I, 48 novilhas Nelore, com 266 kg de peso vivo médio inicial, foram distribuídas no delineamento experimental inteiramente casualizado, em quatro tratamentos, sendo cada animal considerado uma unidade experimental. Os tratamentos foram arranjados em esquema fatorial 2 x 2, com dois tipos de suplemento (suplemento mineral e mineral protéico energético) e dois níveis de monensina (0 e 1200 ppm em suplemento mineral, 0 e 60 ppm em mineral protéico energético). No experimento II, foram utilizados 60 bezerros Nelore, com peso vivo médio inicial de 300 kg. Os animais foram distribuídos em um delineamento inteiramente casualizado em quatro tratamentos com 15 animais cada. Os animais foram submetidos aos tratamentos: com suplemento mineral (controle), suplemento mineral com virginiamicina (1333 ppm), suplemento mineral com salinomicina (1111 ppm) e suplemento mineral com monensina (1000 ppm). Em ambos os experimentos, os animais foram alocados em quatro piquetes de Brachiaria decubens, com 6,7 hectares cada, e eram rotacionados semanalmente. As análises estatísticas foram feitas utilizando o programa estatístico SAS. No experimento I, o consumo do suplemento mineral protéico energético, com e sem monensina, foi maior em relação aos demais tratamentos (P&lt;0,05) e a monensina não provocou uma queda siginificativa no consumo dos suplementos. Os animais que receberam o suplemento mineral protéico energético ganharam mais peso do que os animais que receberam o suplemento mineral (P&lt;0,05), não havendo influencia da monensina sobre o ganho de peso. No experimento II, a monensina promoveu uma redução no consumo em relação ao grupo controle (P&lt;0,06). O suplemento com virginiamicina não afetou o consumo aos 56 dias, mas os suplementos com salinomicina e monensina reduziram o consumo em relação ao controle (P&lt;0,05). Não houve diferença siginificativa no consumo entre os tratamentos aos 28 dias e aos 84 dias, porém houve uma redução no consumo de todos os suplementos. O ganho de peso diário entre os animais que consumiram os aditivos não apresentaram diferenças significativas, mas os tratamentos com virginiamicina e salinomicina proporcionaram ganhos maiores do que o tratamento controle. A virginiamicina e a salinomicina ocasionaram um aumento no ganho de peso, e a salinomicina e a monensina reduziram o consumo. / Two experiments were conducted to evaluate the effects of the supplementation with different feed additives on feed intake and average daily gain for grazing Nellore bovines during the rainy season. On the experiment I, 48 Nellore heifers (266 kg BW) were distributed in four treatments, and each animal was considered one experimental unit. The treatments were organized in a factorial 2x2, two types of supplements (mineral supplement and mineral protein-energy supplement) and two levels of monensin (0 and 1200 ppm in the mineral supplement, 0 and 60 ppm in the mineral protein- energy supplement). In the study II, 60 Nellore calves of 300 kg (BW) were distributed in 4 treatments of 15 animals each. Treatments consisted of the inclusion of: mineral supplement (control treatment), mineral supplement with virginiamycin (1333ppm), mineral supplement with salinomycin (1111 ppm) e mineral supplement with monensin (1000ppm). In both studies, animals were allocated in four rotational stocking areas (6,7 hectares each area) of Brachiariadecubens. Statistical analyses were conducted using the software SAS. In the experiment I, the consumption of the mineral proteic supplement, with and without monensin, was higher compared to the others treatments (P&lt;0.05) and the monensin did not cause any significant decrease on the supplement intake. Animals who received protein mineral supplement had higher average daily gain than animals who received mineral supplement (P&lt;0.05) and there was no effect of monensin on the weight gain. In the experiment II, the inclusion of monensin reduced the consumption compared to the control treatment (P&lt;0.06). The supplement with virginiamycin did not affect the consumption on the day 56, however the supplements with salinomycin and monesin reduced the consumption compared to the control treatment (P&lt;0.05). The average daily gain was statically different among treatments on the days 28 and 84, however there was a reduction on consumption of all treatments. The average daily gain among animals supplemented with different feed additives did not differ statically, but the treatments with the inclusion of virginiamycin and salinomycin had higher gains than the control treatment. The virginiamycin anda salinomycin caused increase weight gain and the salinomycin and monensin reduced the consume.

The current National Academies of Sciences, Engineering and Medicine (NASEM) dry matter intake (DMI) prediction models are inadequate for DMI prediction of beef cattle in the Northern Great Plains. Four studies were conducted to account for additional variation in DMI and average daily gain (ADG) caused by weather variables. Experiment 1 and 2 had 13,895 steer-weeks observations, experiment 3 had 13,739 steer-weeks observations, and experiment 4 had 2,161 cow-weeks observations, respectively. Experiment 1 examined the influence of ambient temperature and solar radiation on DMI of beef steers. In experiment 2, 3, and 4, we examined the influence of ambient temperature, range of temperature, dew point, solar radiation, wind speed and their lags (two-week lag and monthly lag) on DMI of beef steers, ADG of beef steers, and DMI of beef cows, respectively. After adjusting for week of the year, linear and quadratic relationships of predictor variables on response variables were evaluated. In experiment 1 and 2, body weight (BW) had both linear and quadratic relationship with DMI of steers. In experiment 3 and 4, BW had a linear relationship with ADG of steers and DMI of cows, respectively. Week of the year, BW, and dietary energy density (NEm) were accounted for in the base model in experiment 1, 2 and 4 while in experiment 3, DMI was also accounted for. For the models, stepwise regression procedure was utilized. In experiment 1, ambient temperature and solar radiation interacted (P = 0.0001) and accounted for additional variation in DMI of beef steers. In experiment 2, weather variables and their interactions (P = 0.0001) accounted for additional variation in DMI of beef steers. In experiment 3, weather variables (P = 0.0001) accounted for additional variation in ADG of beef steers. In experiment 4, wind speed interacted (P <0.001) with ambient temperature and range of temperature which all accounted for additional variation in DMI of beef cows. These studies show that weather variables interact and cause variation in DMI and ADG in beef cattle. This has helped in better understanding the relationship between weather variables with DMI and ADG. This will improve the accuracy of DMI and ADG prediction equations and help beef cattle producers in managing their feed resources more efficiently.

BACKGROUND: Both endo- and ectoparasites pose a great challenge to the health of pigs worldwide, placing a significant burden on low-resource countries where veterinary care is minimal. As part of a larger clinical trial assessing the use of ivermectin (IVM) mass drug administration to humans and pigs for the control of malaria vectors in the Mopeia district in Mozambique, a longitudinal study to assess the impact of IVM administration on pig health was performed. METHODS: Beginning in March 2022, IVM was administered to pigs in the intervention area once a month for three consecutive months. Seventy pigs from the treatment group and 70 pigs from the control group were randomly selected for inclusion in the study. Fecal samples were collected monthly for three months and analyzed for the presence of strongyle eggs, strongyle eggs in the larval stage (strongyles – larval) and Ascaris suum using the modified McMaster test. Fecal samples were also collected two weeks after each dose of IVM was given to pigs in the treatment group for determination of a fecal egg reduction count. Juvenile pigs were measured twice a month for the first 3 months of the study, then once monthly for another three months. Visual exam for ectoparasites was performed on all pigs for the presence of ticks, lice or scabies at the same time points. RESULTS: Overall, 55% [95% CI: 48-62%] of pigs were positive for Ascaris suum, 95.2% [95% CI: 91-98%] were positive for strongyle eggs, and 72.5% [95% CI: 65.5-79%] were positive for strongyle – larval. A significant difference in the ivermectin treatment group was only seen one month after the second dose of ivermectin was administered: pigs in the treatment group had a 23.6% lower prevalence of strongyles (p = 0.003) and 18% lower prevalence of strongyles – larval (p = 0.03). Pigs in the treatment group also had lower EPG for Ascaris suum (diff = 102 EPG; p = 0.006), strongyles (diff = 642 EPG; p < 0.001), and strongyles - larval (diff = 217 EPG; p < 0.001). Analysis of covariance regression found no significant difference(P>0.05) in average daily weight gain (ADG) between the treatment and control groups. CONCLUSION: IVM delivered once monthly for three months has a small impact on pig health. To counteract the multiple health challenges pigs face in these settings, different dosing schedules along with education on husbandry issues related to nutrition and sanitation should be investigated in order to maximize impact on pig health. / Master of Science / A study was conducted in rural Mozambique in the district of Mopeia to determine the effectiveness of ivermectin against common parasites of swine when administered to pigs. The study began in March of 2022, at the beginning of rainy season, and ivermectin was given to pigs once a month for three months. Pigs were visited twice a month for the first three months, and then once a month for another three months. At various time points, fecal samples were collected, pigs were examined for evidence of ectoparasites (ticks, lice and scabies infestation), and young pigs were measured to determine their rate of growth. Fecal samples were analyzed for the presence of common internal parasites (endoparasites) affecting pigs in the area. The burden of endo and ectoparasites was estimated before any ivermectin was administered, and then compared in treated and untreated pigs over the course of the study. Similarly, the effect of ivermectin on growth rates in young animals was determined. The results of this study found that there was a high burden of common endoparasites in pigs in the Mopeia district, which was only minimally affected by the use of ivermectin delivered once a month. Among the treated pigs, a fecal egg count reduction test suggests that these parasites are potentially resistant to ivermectin, although other issues may be responsible for these results. The burden of ectoparasites was generally low (<10%), with ivermectin only significantly reducing the prevalence of ticks. Young animals that received ivermectin had a 15% increase in their growth rate, but this was not statistically significant. In conclusion, the use of ivermectin once a month for three months in pigs, as part of a malaria intervention, has some minimal positive health effects on treated pigs. Given the poor management practices, poor nutrition and lack of veterinary care in these pigs, it is likely that to have a greater impact on pig health, ivermectin will need to be delivered under a different dosing schedule and alongside owner education on pig management practices.

O objetivo do presente trabalho foi avaliar o desempenho reprodutivo de leitoas que foram selecionadas com baixos ganhos de peso diários (GPD) aos 160 dias de vida. Leitoas da linhagem Camborough® (n = 3301) foram alocadas em quatro grupos de acordo com o GPD no momento da seleção: G1 (n = 799) leitoas com GPD ≥480 a ≤ 530g/dia, G2 (n = 978) leitoas com >530 a ≤ 580g/dia, G3 (n = 916) fêmeas com >580 a ≤ 630g/dia e G4 (n = 608) leitoas com >630 a ≤ 810g/dia. Não foram encontradas diferenças na idade de início de estimulação com o macho e manifestação do primeiro estro entre as classes (P> 0,05). Na cobertura todos os grupos diferiram entre si sendo o G4 o grupo mais precoce e com maior peso (P< 0,05). O GPD da seleção até a cobertura diferiu entre as classes, sendo que o G1 teve maiores ganhos de peso quando comparado ao G3 e G4 respectivamente (P< 0,05). As médias de nascidos totais, nascidos vivos e intervalo desmame-estro não diferiram entre os grupos (P> 0,05). As remoções entre a seleção e a cobertura pós-desmame foram maiores no G1 e G2 quando comparados ao G4 (P< 0,05). Quando agrupados G1 e G2 e, a partir disso, formadas duas classes de acordo com o peso na cobertura (≤ 130 kg e > 130 kg), o grupo > 130 kg obteve 0,93 leitão a mais no primeiro parto (P< 0,05). Em conclusão, leitoas selecionadas com baixos GPDs (inferiores a 630g/dia) podem ser incorporadas no plantel sem gerar prejuízos no desempenho reprodutivo até o primeiro parto, desde que alcancem 130 kg no momento da cobertura. / The aim of this study was to evaluate the reproductive performance of gilts selected with low average daily gain (ADG) at 160 days of age. Camborough® gilts (n = 3301) were allocated into four groups according to ADG at selection: G1 (n = 799) represented the group of gilts with ADG ≥480-≤ 530g/day, G2 (n = 978) corresponded to gilts with >530- ≤ 580g/day, G3 (n = 916) represented the gilts with > 580-≤ 630g/day and G4 (n = 608) gilts with > 630-≤ 810g/day. There were no differences in the age at the onset of boar exposure and first estrus expression among groups (P> 0.05). Age and weight at insemination were different (P< 0.05) among groups. Gilts from G4 were inseminated earlier and heavier. The ADG from selection until mating was different among the groups, and G1 had greater weight gains when compared to G3 and G4 (P< 0.05). Total number of piglets born, number of piglets born alive and weaning to oestrus interval were not different among classes (P> 0.05). The removals since the selection until post-weaning insemination were higher in G1 and G2 when compared to G4 (P< 0.05). When gilts from G1 and G2 were grouped and categorized into two classes according to the weight at insemination (≤ 130 kg and > 130 kg), the heavier group (> 130 kg) had an increasing of 0.93 total born piglets at first farrowing (P< 0.05). The results of this study suggest that gilts selected with low ADG (less than 630g/day) could be incorporated into the breeding herd with no reproductive performance losses until the first farrowing if they reach 130 kg at insemination.

O entendimento das relações entre as características do pasto e as respostas do comportamento ingestivo animal é fundamental para o aprimoramento de inovações no manejo de pastagens, tornando os sistemas pastoris mais eficientes e competitivos. Neste estudo comparamos dois métodos de pastoreio (Rotativo x Contínuo) e duas intensidades de pastejo (Moderada e Baixa) a fim de compreendermos como as características de pastos de azevém anual (Lolium multiflorum Lam.) influenciam o comportamento ingestivo e o ganho médio diário de ovinos. Observamos que o método de pastoreio afeta a quantidade de folhas e inflorescências, influenciando a composição química da forragem, além da taxa de bocados e o tempo de pastejo dos ovinos. Por outro lado, as intensidades de pastejo influenciaram os bocados por estação alimentar e o número de refeições. Além disso, variáveis como: estação alimentar por minuto, duração das refeições e tempo de pastejo foram positivamente correlacionadas com o ganho médio diário dos animais, assim, podem ser utilizadas como preditoras do ganho médio diário de ovinos. Encontramos evidências de que em pastoreio rotativo, ambas as intensidades de pastejo estudadas promoveram um rebaixamento em torno de 45% da altura pré-pastejo. A estrutura do pasto e a composição química da forragem foram adequadas para o pastejo de ovinos até o início do estádio reprodutivo do azevém anual. No entanto, ao final do estádio reprodutivo da pastagem, ambas as intensidades de pastejo restringiram os padrões de comportamento ingestivo dos ovinos nas maiores escalas espaço-temporais. Essa restrição é acentuada durante o rebaixamento do pasto, em decorrência da redução no percentual de lâminas foliares, alterando o comportamento ingestivo de ovinos. Logo, a resposta comportamental de ovinos depende de: (i) taxa de lotação, (ii) nível de desfolha do dossel, (iii) período do estádio reprodutivo do azevém anual e composição estrutural da forragem durante o rebaixamento. / The understanding of the relationships between sward characteristics and the animals' ingestive behavior responses is fundamental for the improvement of sward management innovations, making pastoral systems more efficient and competitive. In this study, we compared two stocking methods (Continuous and Rotational) and two grazing intensities (Moderate and Low) to understand how the sward characteristics of annual ryegrass (Lolium multiflorum Lam.) influence the ingestive behavior and the average daily gain of sheep. We observed that the stocking method affect the quantity of leaf blades and inflorescences influenced forage chemical composition, as well as the bite rate and grazing time of sheep. On the other hand, grazing intensities had influence the bites by feeding station and meals number. Moreover, variables as feeding station per minute, meals duration and grazing time were positively correlated with the average daily gain, thus, they can be used as predictors for the average daily gain of sheep. We found evidence that both grazing intensities studied promote a grazing down around 45% of pre-grazing sward height in rotational stocking. Sward structure and forage chemical composition, were adequate for sheep grazing until the beginning of the sward reproductive stage. However, from the stage 2 of grazing down at the end of the sward reproductive stage, both grazing intensities apparently restricted the sheep‟s ingestive behavior patterns in the larger spatial and temporal scales of grazing. Therefore sheep‟s behavioral response depends on: (i) stocking rate, (ii) canopy defoliation level, (iii) period of sward reproductive stage and forage structural composition during grazing down.

Conventional production of meat products from ruminant animals in the United States requires inputs including the cultivation and nitrogen fertilization of annual grains such as corn and barley, and transportation of cattle and grain to feedlots. Consumers have concerns about the impact of feedlot conditions on animal health, and about the implications of pharmaceutical inputs such as growth hormones and antibiotics on the environment and human health. These concerns have led to a growing interest in pasturefinished meat production by consumers. Such smaller-scale livestock production systems can be healthier and lower-stress for animals, are integrated into local food systems and are more transparent to consumers, and have higher potential profitability for producers than traditional ruminant production methods. There is a strong market for pasture-finished beef products, and prices for naturally or organically raised beef have remained well above feedlot-produced product prices. There is also concern about the impact of ruminant production on the environment, including air and water pollution from feedlot production and greenhouse gasses that are emitted from ruminant animals during feed digestion. This thesis project explored the potential of a beef production system based on perennial legumes, including the non-bloating legume birdsfoot trefoil (BFT; Lotus corniculatus L.) for producing meat products from cattle while reducing concentrate feeding and methane production. The condensed tannins that are produced by BFT bind proteins in the rumen but allow them to be digested in the abomasum and intestines, which in turn leads to better utilization of forage nutrients during the finishing period and higher gains or milk production. The higher digestibility of legumes compared with grasses reduces methane emissions in cattle both through higher digestibility of the forage and through direct impacts on methanogens operating in the rumen. As reported in this thesis, steers finished on BFT gained significantly more weight per day than steers fed another perennial forage legume, cicer milkvetch, but did not gain as rapidly as feedlot-fed steers. At the end of summer grazing, the blood plasma of pasture-fed steers was lower in saturated and omega-6 fatty acids and higher in transvaccenic and omega-3 fatty acids than the blood plasma of feedlot-fed steers. When beef cows grazed grass and legume pastures, enteric methane emissions were lower on the legume pastures than the grass pasture. These results demonstrate that, compared with other feed sources, perennial legume pastures used for cattle production can improve cattle gains and reduce environmental impacts.

Objetivou-se avaliar diferentes maneiras de manejar o campo nativo durante o período hibernal para alimentar ovelhas no inicio de gestação e determinar a melhor metodologia para tal fim, por meio das características produtivas e comportamentais dos animais assim como modificação na estrutura e qualidade da pastagem. Para tal, foram testados, com delineamento em blocos casualizados com quatro tratamentos e três repetições, dois métodos de pastoreio (contínuo (LC) e rotativo (LR)) e dois níveis de oferta de forragem (12 e 18% OF). As variáveis utilizadas para descrever as características produtivas dos animais foram: ganho médio diário das ovelhas e cordeiros, escore de condição corporal das ovelhas e o ganho de peso, em unidade de área, das ovelhas, cordeiros e o ganho total por área. Além destes, foram avaliados parâmetros de comportamento ingestivo, que são o tempo diurno de pastejo, ruminação e outras atividades, número, tamanho e intervalo de refeições, número, tempo e número de passos entre estações alimentares e taxa de bocados. As variáveis medidas no pasto foram: massa de forragem, taxa de acumulo, altura, massa de folhas verdes, colmos, leguminosas e “outras espécies”, e as características bromatológicas (proteína bruta, FDN, etc.) do pasto ao longo do tempo de duração do experimento. Os resultados apontaram que as OF, apesar de provocar modificações significativas na massa de forragem e altura do pasto, teve pouca influencia nos parâmetros de comportamento animal em pastejo e pouca influencia no desempenho produtivo dos animais, provavelmente devido ao baixo contraste que as ofertas de forragem intermediárias proporcionaram durante o inverno. Os métodos de utilização da pastagem também não apresentaram influência marcante sobre o desempenho produtivo das ovelhas, mas modificou drasticamente o comportamento ingestivo dos animais. Os animais manejados em LR apresentaram menores tempos de pastejo do que os animais mantidos em LC, e esse tempo variou também entre os dias de avaliação. A interação dos dois fatores não teve influência no peso dos cordeiros ao nascer, porém, influenciaram as características estruturais e bromatológicas do pasto. Onde no manejo no inverno foi constituído pelo método contínuo e 12% de OF, a pastagem apresentou uma menor quantidade de outras espécies e presença predominante de espécies de melhor qualidade, ficando mais “limpa” e melhor qualidade nutricional na primavera. Essa melhor qualidade nutricional, por sua vez, apesar de não modificar significativamente os ganhos individuais de ovelhas e cordeiros, modificou a quantidade de peso vivo produzido em unidade de área. / The main objective was to evaluate strategies to manage the grassland during the winter season to feed ewes at the early pregnancy and determine the best method for this purpose, through the animal production characteristics, their ingestive behavior as well as modification of the structure and quality of the pasture. The experiment was set up in a randomized block design with four treatments and three replicates, two grazing methods (continuous (CS) and rotational (RS)) and two levels of herbage allowance (HA; 12 - and 18% LW). The variables used to describe the animals performance were: average daily gain of sheep and lambs, ewes body condition score and weight gain in unit area of the sheep, lambs and total gain per area. It was also assessed parameters of ingestive behavior as the diurnal grazing time, ruminating and other activities, number , size and range of meals, number, time and step number between feeding stations and biting rate. The variables measured in the pasture was: herbage mass, accumulation rate, height, mass of green leaves, stems, legumes and 'other species' and nutritive characteristics values (crude protein, NDF, etc.) of the pasture over all time of duration of the experiment. The results showed that the HA, although cause some significant changes in herbage mass and sward height, had little influence on animal behavior parameters and little influence on the productive performance of animals, probably due to the low contrast that intermediate herbage allowance provided. The grazing methods also had no significant influence on the performance of the sheep, but dramatically changed the ewes grazing behavior. The smaller area in the RS promoted a shorter grazing time than the time observed on a CS, and the grazing time on RS also varied during the days. The interaction of the two factors did not influence the weight of lambs at birth, however, influence the structural and chemical characteristics of the pasture. Where the management in winter was constituted by CS and 12% HA, the pasture had a lower amount of other species, being “cleaner” and, also presents a better nutritional quality in the subsequent spring. This improved nutritional quality, in turn, while not significantly modify the ewes and lambs individual gains, changed the amount of weight produced on unit of area, been more productive than other combinations.

O entendimento das relações entre as características do pasto e as respostas do comportamento ingestivo animal é fundamental para o aprimoramento de inovações no manejo de pastagens, tornando os sistemas pastoris mais eficientes e competitivos. Neste estudo comparamos dois métodos de pastoreio (Rotativo x Contínuo) e duas intensidades de pastejo (Moderada e Baixa) a fim de compreendermos como as características de pastos de azevém anual (Lolium multiflorum Lam.) influenciam o comportamento ingestivo e o ganho médio diário de ovinos. Observamos que o método de pastoreio afeta a quantidade de folhas e inflorescências, influenciando a composição química da forragem, além da taxa de bocados e o tempo de pastejo dos ovinos. Por outro lado, as intensidades de pastejo influenciaram os bocados por estação alimentar e o número de refeições. Além disso, variáveis como: estação alimentar por minuto, duração das refeições e tempo de pastejo foram positivamente correlacionadas com o ganho médio diário dos animais, assim, podem ser utilizadas como preditoras do ganho médio diário de ovinos. Encontramos evidências de que em pastoreio rotativo, ambas as intensidades de pastejo estudadas promoveram um rebaixamento em torno de 45% da altura pré-pastejo. A estrutura do pasto e a composição química da forragem foram adequadas para o pastejo de ovinos até o início do estádio reprodutivo do azevém anual. No entanto, ao final do estádio reprodutivo da pastagem, ambas as intensidades de pastejo restringiram os padrões de comportamento ingestivo dos ovinos nas maiores escalas espaço-temporais. Essa restrição é acentuada durante o rebaixamento do pasto, em decorrência da redução no percentual de lâminas foliares, alterando o comportamento ingestivo de ovinos. Logo, a resposta comportamental de ovinos depende de: (i) taxa de lotação, (ii) nível de desfolha do dossel, (iii) período do estádio reprodutivo do azevém anual e composição estrutural da forragem durante o rebaixamento. / The understanding of the relationships between sward characteristics and the animals' ingestive behavior responses is fundamental for the improvement of sward management innovations, making pastoral systems more efficient and competitive. In this study, we compared two stocking methods (Continuous and Rotational) and two grazing intensities (Moderate and Low) to understand how the sward characteristics of annual ryegrass (Lolium multiflorum Lam.) influence the ingestive behavior and the average daily gain of sheep. We observed that the stocking method affect the quantity of leaf blades and inflorescences influenced forage chemical composition, as well as the bite rate and grazing time of sheep. On the other hand, grazing intensities had influence the bites by feeding station and meals number. Moreover, variables as feeding station per minute, meals duration and grazing time were positively correlated with the average daily gain, thus, they can be used as predictors for the average daily gain of sheep. We found evidence that both grazing intensities studied promote a grazing down around 45% of pre-grazing sward height in rotational stocking. Sward structure and forage chemical composition, were adequate for sheep grazing until the beginning of the sward reproductive stage. However, from the stage 2 of grazing down at the end of the sward reproductive stage, both grazing intensities apparently restricted the sheep‟s ingestive behavior patterns in the larger spatial and temporal scales of grazing. Therefore sheep‟s behavioral response depends on: (i) stocking rate, (ii) canopy defoliation level, (iii) period of sward reproductive stage and forage structural composition during grazing down.