Blumetto Velazco, OR. (2012). Caracterización de sistemas de producción de porcino y vacuno de engorde en Uruguay [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/16002

Estimating feed efficiency in grazing environments is challenging due to difficulties in quantifying food intakes and diet choices in free-grazing animals. The plant-wax marker technique may be a useful tool to redress this problem. However, its reliability needs to be validated before its wider application. This study was designed to assess the reliability of plant-wax markers for estimating botanical composition of test diets, and diet choices in beef cattle, and provided opportunities to evaluate efficiency in growing heifers. To test estimation of botanical composition, samples of red clover and fescue hay were mixed to form test diets containing 0-100% of either forage. To test estimation of diet choices, 24 heifers from large and moderate frame size lines were evaluated at two instances. Cubed red clover and fescue hays were offered ad libitum. After an acclimation period, feed intakes and body weights were collected for 10 days; fecal samples were collected for the final 5 days. Hydrocarbons and alcohols were quantified with gas chromatography. Estimates were based on least squares. Operator expertise affected measured concentrations of shorter-chained n-alkanes (P<0.041) and long-chain alcohols (P<0.02). Still, overall reliability of the technique was unaffected. Large and moderate framed animals did not differ in efficiency (P>0.05), although large framed animals had increased red clover intakes (P<0.01). Once corrected for fecal losses of n-alkanes, diet choices were estimated accurately. Plant-wax markers provided reliable estimates of botanical composition of diets, and diet choices of animals, suggesting it is a valuable tool to assess efficiencies of grazing cattle. / Master of Science

Agricultural conservation practices can have a vast number of environmental benefits but adoption of these practices may not be widespread. If farm operators are able to reap financial returns for environmental services, adoption of these conservation practices could increase. One source of potential financial returns is in greenhouse gas (GHG) emission reductions or increased GHG sequestration. An example of a conservation management strategy for beef and dairy operations which has the potential to decrease GHG emissions or increase GHG sequestration is an intensively managed rotational grazing system. The objective of this study is to estimate potential financial returns from conversion to rotational grazing and the sale of GHG credits by Virginia beef and dairy farms. The three GHGs examined in the study are carbon dioxide, nitrous oxide, and methane. Primary and secondary data are used to simulate financial performance and GHG emissions for three case study farms under different levels of production and pasture utilization. Each case study farm is simulated under three reference conditions to calculate financial performance and three baseline scenarios and a regional performance standard to calculate GHG emissions on both a per farm and a per metric ton of product sold metric. The change in emissions between the scenarios is found and potential returns from the sale of GHG emissions credits are calculated. Results of the analysis demonstrate that conversion to rotational grazing has the potential to increase overall revenues for the farm operation from $4,197.72 to $50,007.46. GHG emission changes for the farm operation do not show a clear trend towards reduction. The amount of financial return from the sale of GHG reduction credits varies from $37.15 to $76.26 for the three case study farms for the initial calculations, and varies from $24.10 to $755.36 once the study performs sensitivity analysis for methane emissions. Therefore, results indicate that rotational grazing can increase net revenues for farm operations but additional net revenue from the sale of GHG reduction credits is small and dependent on the chosen baseline scenario and metric. Follow up research should address the following areas: changes in the cost of on-farm labor, risk of conversion to rotational grazing, increased accuracy of the measurement of GHG emissions and soil carbon, the effects of rotational grazing on forage TDN, and the water quality impacts of rotational grazing. / Master of Science

Grazing pressure is important in structuring plant communities, particularly in aquatic environments. Eelgrass (Zostera marina), a keystone species in estuaries across North America, is experiencing widespread population declines. As a keystone species, eelgrass provides numerous important functions, including: 1) water filtration, 2) sediment stabilization, 3) providing refuge and nursery habitat for numerous species, and 4) carbon sequestration. Benefits which could be lost if eelgrass beds continue to diminish. California has experienced some of the greatest eelgrass declines, and Morro Bay, CA experienced a 96% decrease in eelgrass from 2007 to 2017. Most studies to date have examined bottom-up stressors, such as sedimentation and nutrient load, but little research has been done on top-down effects. Brant geese (Branta bernicla) are specialist grazers of eelgrass, feeding voraciously on it in the winter and spring months to build energy stores for their flight to summer breeding grounds in Alaska. Simulated brant grazing studies conducted in Humboldt, CA indicate brant might play an important role in maintaining the health and productivity of eelgrass communities through selective grazing and overcompensation – where plants purportedly grow more in response to herbivory. While there has been some experimental evidence of overcompensation, the idea is not well supported overall. Research was conducted on eelgrass beds in Morro Bay over the 2018-19 brant season. We hypothesized that: 1) brant grazing would decrease growth and overall condition of eelgrass; and 2) brant would selectively graze younger, nitrogen-rich blades. Four study sites were established, each with four open plots that allowed for natural brant grazing (treatment), and four enclosed plots that excluded brant and prevent grazing (control). Polyvinyl chloride (PVC) pipe was used to create cage-like structures around small plots of eelgrass, thus excluding brant, and exclosure effectiveness was confirmed with rigorous observations. Data on eelgrass growth and brant activity was gathered regularly at each site. We predicted that: 1) eelgrass open to brant grazing would show decreases in blade length, stipe density, and other growth and condition proxies before and after brant season when compared with eelgrass protected from brant grazing; and 2) eelgrass grazed by brant would have more epiphytes because brant selectively graze younger blades and leave older blades that accumulate more epiphytes. There were no significant differences in growth or condition of eelgrass between grazed (treatment) and ungrazed (control) plots. Brant activity was detected at each study site and brant exclosures were effective, with no evidence of brant grazing found in control plots. There was no difference in epiphyte load between grazed and ungrazed plots. The findings of this study are contrary the only previous studies examining the relationship between brant grazing and eelgrass growth. Our study suggests brant do not have a significant effect on eelgrass in Morro Bay.

Master of Science / Department of Agronomy / Walter H. Fick / Patch-burn grazing is a relatively new concept in terms of rangeland management. While numerous benefits have been associated with this system, in the tallgrass prairie of Kansas, cattle production and sustainability of rangeland are critical. In 2006, 253 ha at the KSU Bressner Range Research Unit in Woodson County, Kansas were subjected to spring patch-burn grazing (using one-third portions) and traditional full-burn grazing. Each treatment within the split-block design was replicated four times for 3 years. The objectives were to evaluate whether livestock performance would be compromised under this grazing system, to monitor the health of the rangeland, and to observe the usefulness of this tool as a potential control of the invasive plant sericea lespedeza [Lespedeza cuneata (Dumont) G. Don]. In regards to cattle performance, burn treatments had no significant difference in average daily gain (p≥0.10) in any of the 3 years. On average, cattle utilized 61% of the current year’s forage production in patch-burned portions, which was higher (p≤0.10) than that of unburned (30%) and full-burn (41%) portions. Results of the botanical composition show forb and woody plant composition did not differ between treatments, however differences (p≤0.10) were present in grass composition. Total annual grasses increased 19.1 percentage units under patch-burn and 2.1 units under full-burn, while total perennial grasses decreased 18.4 and 1.1 units, respectively. When evaluated by treatment area (one-third portion), results indicated that the 3-year cycle did allow enough time for recovery. At 2 years after treatment (2-YAT), no significant difference in composition(p≥0.10) was present between initial patch-burn portions and the full-burn pastures. Finally, in only 1 year of the study did cattle statistically consume a greater percentage of sericea lespedeza plants (p≤0.10) in the patch-burned portions (92%) than in full-burned pastures (35%). Biomass utilization did not differ (p≥0.10) between burn treatments. Surprisingly, there was a trend for the number of plants in the sampled areas of the patch-burn portions to decrease throughout the cycle. However, at the conclusion of the 3-year cycle, sericea densities did not differ(p≥0.10) between treatments. Patch-burn grazing shows promise as a potential management tool for Kansas land managers.

O objetivo do presente estudo foi avaliar o efeito da suplementação energética com dose baixa de milho moído (0 x 0,3% do PC) sobre o consumo de forragem, o comportamento ingestivo e parâmetros metabólicos (ruminais e sanguíneos) em bovinos da raça Nelore, mantidos em pastagem de capim Brachiaria Brizantha cv. Marandu. submetida à duas estratégias de manejo, 25/15cm x 35x21cm como alturas de entrada/saída dos pastos respectivamente. Foram utilizados 8 novilhos Nelores com cânulas no rumen, com PC médio de 414 kg ± 10,32. Foram utilizados 2 quadrados latinos 4X4 simultaneamente. Os animais foram alocados em 2,4 ha de pastagem de capim Brachiaria brizantha cv. Marandu. Foram estudados 2 níveis de suplementação energética (milho moído) e 2 estratégias de manejo do pastejo: T1) não suplementado e manejo 25/15 cm (alturas pré e póspastejo respectivamente); T2) suplementado com 0,3% do PC em milho moído e manejo 25/15; T3) não suplementado e manejo 35/21 cm (alturas pré e pós-pastejo respectivamente); T4) suplementado com 0,3% do PC em milho moído e manejo e 35/21 cm. Os parâmetros avaliados foram o consumo de forragem, comportamento animal, pH e amônia ruminais, concentrações de ácidos graxos de cadeia curta (AGCC), teores plasmáticos de glicose e digestibilidade total dos nutrientes. A suplementação com 0,3% PC causou alta taxa de substituição com tendência a redução do consumo de forragem em %PC (P<0,10) e não alterou (P>0,05) o consumo de MS digestível. Esse efeito foi observado independente da estratégia de manejo adotada. Entre as variáveis do comportamento animal a suplementação reduziu o tempo de pastejo (P<0,05) e o manejo 25/15 resultou em maior taxa de bocado (P<0,01). A suplementação não afetou o pH ruminal (P>0,05), reduziu a concentração de N-NH3 (P<0,05), aumentou a proporção molar de propionato e reduziu a relação acetato:propionato (P<0,05). O manejo 25/15 aumentou a proporção molar de propionato e houve tendência a reduzir a relação acetato:propionato (P<0,1). A suplementação energética reduziu (P<0,05) a digestão da MS da forragem, mas não (P>0.05) da FDN da forragem e aumentou (P<0.05) a digestão da MS da dieta. A digestibilidade da forragem e da dieta total apresentaram maior (P<0,05) digestibilidade da MS e da FDN quando foram manejados com 25/15 cm. A suplementação com 0,3%PC reduz o consumo de forragem e não aumenta a ingestão de energia de bovinos em sistemas de pastejo rotacionado independente da estratégia de manejo adotada. A estratégia de manejo com bovinos de corte em pastagens de bom valor nutritivo manejadas intensivamente no período das aguas promove uma praticidade no seu manejo entre o pastejo de altura com 25/15 e 35/21 cm. / The aim of this study was to evaluate the effects of low dose supplementation with ground corn (0 vs. 0.3% BW) on forage intake, feeding behavior and metabolic parameters (i.e. rumen and blood) in Nellore cattle grazing Bracharia brizantha cv. palisadegrass submitted to two managementstrategies (25 / 15cm vs. 35 / 21cm heights as pre-grazing/ post-grazing heights, respectively). Eight rumen cannulated bulls were used, averaging body weight (BW) of 414 kg ± 10.32 SEM. Two 4X4 Latin squares were used simultaneously. The animals were placed in 2.4 ha palisadegrass pastures. Two levels of supplementation (ground corn) and two grazing management strategies were studied: T1) unsupplemented management and 25/15 cm (height pre and post-grazing heights, respectively); T2) supplemented with 0.3% BW on 25/15 ground corn and management; T3) unsupplemented management and 35/21 cm; T4) supplemented with 0.3% BW with ground corn and 35/21 cm sward heights. The parameters evaluated were forage intake, animal performance, ruminal pH and ammonia-N concentrations of short chain fatty acids (SCFA), plasma levels of glucose and total tract digestibility of nutrients. Supplementation with 0.3% BW caused high substitution rates with reduced forage intake% BW (P <0.10) and no change (P> 0.05) on intake of digestible dry matter. This effect was observed regardless of the pasture management strategy. Among the variables of animal behavior, the use of supplements reduced grazing time (P <0.05) and the management 25/15 resulted in higher bite rates (P <0.01). Supplementation did not affect ruminal pH (P> 0.05), reduced the concentration of NH3-N (P <0.05), increased the molar proportion of propionate and decreased the acetate: propionate ratio (P <0.05) . The management 25/15 increased the molar proportion of propionate and decreased the acetate: propionate ratio (P <0.1). Supplementation reduced (P <0.05) digestion of forage DM, but not NDF (P> 0.05) and forage increased digestion of the diet DM (P <0.05). The digestibility of forage and total diet had higher digestibility of DM and NDF when were managed with 25/15 cm (P <0.05). Supplementation with 0.3% BW reduces forage intake and does not increase the energy intake of cattle in rotational grazing systems independent of the management strategy adopted. The management strategies of 25/15 and 35/21 cm of pre- and post-grazing heights, respectively, were effective and did not differ on overall individual performance of beef cattle grazing on good nutritional value intensively managed pastures in the rainy season.

Burning and grazing are key processes in the natural disturbance regime of the Fescue Prairie. Burning, grazing and their interacting effects on plant species diversity (H¡¯), species richness, and heterogeneity in species composition were studied at two spatial scales for two years in a remnant Fescue Prairie near Saskatoon, Saskatchewan. Cattle distribution in relation to plant communities was also studied. At the plot scale (100 m2), burning increased H¡¯ (P<0.01) (x=1.75) compared to unburned treatments (x=1.54) (S.E.¡À0.058). Burning, grazing, and burning + grazing had no significant effect (P>0.10) on species richness; richness varied between years (P=0.04), averaging 14.2 species m-2 in year one versus 15.8 species m-2 in year two (S.E.¡À 0.65). Spatial heterogeneity (P>0.25; x=46%; S.E.¡À3.0) and temporal heterogeneity in species composition (P>0.21; x=42%; S.E.¡À3.8) were not affected by burning, grazing, or their interaction. Burning + grazing increased tiller densities in <i>Elymus lanceolatus</i> (68%) and those of <i>Festuca hallii</i> (11%) (P<0.001) compared to the control. Burning decreased total aboveground net primary production (ANPP) (P<0.001) (x=305 g m-2) compared to unburned treatments (x=500 g m-2; S.E.¡À30.8). Grazing and burning + grazing had no effect on total ANPP or graminoid ANPP (P¡Ý0.36). At the scale of Kernen Prairie (130 ha), H¡¯ increased between 1996 (P<0.05) (x=1.10) and 2005 (x=1.40; S.E.¡À0.094). Species richness increased from 5.2 species 0.25 m-2 in 1996, to 6.8 species 0.25 m-2 in 2005 (S.E.¡À0.505). Heterogeneity in plant species composition tended to increase after prescribed burning was started in 1986 and after grazing began in 2006. Cattle preferred <i>Bromus inermis-</i> and <i>Poa pratensis-</i>dominated plant communities, areas with intermediate amounts of total aboveground standing crop of plants, and areas in which shrub densities exceeded 16 stems 0.25 m-2. In the short term, burning and environmental conditions had greater effects on species diversity, richness, and heterogeneity in species composition than grazing or the interaction of burning and grazing. Different responses may be expected with different combinations of timing, frequency, and intensity of burning and grazing at different sites under ever changing environmental conditions.

The report is a comparative study between spruce plantations where 4 plants are treated with deer repellents and 4 plantations are untreated. The study aims to provide a base for the Forest Society's future decisions regarding the use of wildlife-repellents.  The report indicates that wildlife-repellents work reasonably well for its purpose, the treated stocks were virtually untouched during the planting year and next year while the untreated stocks have been heavily grazed during these years.  Growth difference between grazed plants and ungrazed plants found to be virtually non-existent (0, 01 m) of the treated stocks and 0, 07 m in the untreated plants. Because of the growth differences are so small between grazed and no grazed plants, it seems like the treatment of deer-repellent are unnecessary. Unless you know in particularly that the area has a specific problem whit severe deer-grazing.

Burning and grazing are key processes in the natural disturbance regime of the Fescue Prairie. Burning, grazing and their interacting effects on plant species diversity (H¡¯), species richness, and heterogeneity in species composition were studied at two spatial scales for two years in a remnant Fescue Prairie near Saskatoon, Saskatchewan. Cattle distribution in relation to plant communities was also studied. At the plot scale (100 m2), burning increased H¡¯ (P<0.01) (x=1.75) compared to unburned treatments (x=1.54) (S.E.¡À0.058). Burning, grazing, and burning + grazing had no significant effect (P>0.10) on species richness; richness varied between years (P=0.04), averaging 14.2 species m-2 in year one versus 15.8 species m-2 in year two (S.E.¡À 0.65). Spatial heterogeneity (P>0.25; x=46%; S.E.¡À3.0) and temporal heterogeneity in species composition (P>0.21; x=42%; S.E.¡À3.8) were not affected by burning, grazing, or their interaction. Burning + grazing increased tiller densities in <i>Elymus lanceolatus</i> (68%) and those of <i>Festuca hallii</i> (11%) (P<0.001) compared to the control. Burning decreased total aboveground net primary production (ANPP) (P<0.001) (x=305 g m-2) compared to unburned treatments (x=500 g m-2; S.E.¡À30.8). Grazing and burning + grazing had no effect on total ANPP or graminoid ANPP (P¡Ý0.36). At the scale of Kernen Prairie (130 ha), H¡¯ increased between 1996 (P<0.05) (x=1.10) and 2005 (x=1.40; S.E.¡À0.094). Species richness increased from 5.2 species 0.25 m-2 in 1996, to 6.8 species 0.25 m-2 in 2005 (S.E.¡À0.505). Heterogeneity in plant species composition tended to increase after prescribed burning was started in 1986 and after grazing began in 2006. Cattle preferred <i>Bromus inermis-</i> and <i>Poa pratensis-</i>dominated plant communities, areas with intermediate amounts of total aboveground standing crop of plants, and areas in which shrub densities exceeded 16 stems 0.25 m-2. In the short term, burning and environmental conditions had greater effects on species diversity, richness, and heterogeneity in species composition than grazing or the interaction of burning and grazing. Different responses may be expected with different combinations of timing, frequency, and intensity of burning and grazing at different sites under ever changing environmental conditions.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The objective of this research was to evaluate the effect of private supplementation with concentrated or legume, on the pasture characteristics, performance, carcass traits, body components, physico-chemical and sensory characteristics of the meat from suckling lambs kept on ryegrass pasture. Twenty seven suckling lambs were used with about 17 days of age and weighing 9,91 ± 0,594kg, which are distributed in the treatments that corresponded to feeding systems: suckling lambs kept on ryegrass pasture, suckling lambs kept on ryegrass pasture and supplemented with concentrated in private feeder (creep feeding) and suckling lambs kept on ryegrass pasture and supplemented with legume in the private pasture (creep grazing). The concentrate supplement was composed by corn, soybean meal and limestone, and was supplied ad libitum. The supplementary pasture was composed by legume white clover. It was evaluated the characteristics of ryegrass pasture and performance of lambs, which were slaughtered when reached 32 kg of body weight. Subsequently, evaluated the carcass characteristics, body components and characteristics of meat. The experimental design was completely randomized, where the results were submitted to analysis of variance and means compared by Tukey test at 5% of significance level. Supplementation, through concentrated or legumes, did not increase the performance of suckling lambs grazing ryegrass, despite differences in neutral detergent fiber and acid detergent fiber by consumed pasture from animals that were smaller for the supplemented with legume. Suckling lambs kept in ryegrass produce similar carcasses of animals receiving supplement, despite gastrointestinal tract content with bile and urine and the proportion of the esophagus be higher (P<0,05) in lambs maintained in ryegrass and not supplemented and proportions of liver and intestine are higher (P<0,05) in lambs supplemented with concentrate. The color of the meat of was affected (P<0,05) by feeding system, being less opaque and red but more yellow the meat from not supplemented lambs. The tocopherol and cholesterol levels were higher (P<0,05) in meat of lambs not supplemented as well as lower contents of ash (P<0,05) were found in the meat of these animals. The water hold capacity was lower (P<0,05) in meat from animals supplemented with concentrate. Most intense characteristic flavor (P<0,05) was observed in meat from lambs who consumed concentrated; and more tender (P<0,05) was the meat of suckling lambs supplemented with legume. The use of white clover legume as supplementary private pasture provides rapid finishing of lambs with carcass and meat with quality, which makes this feeding system an option to finishing lambs. / Esta pesquisa foi realizada com o objetivo de avaliar o efeito da suplementação privativa, com concentrado ou leguminosa, sobre as características da pastagem, desempenho, características de carcaça, componentes corporais, características físico-químicas e sensoriais da carne de cordeiros lactentes mantidos em pastejo de azevém. Foram utilizados 27 cordeiros lactentes com aproximadamente 17 dias de idade e pesando 9,91±0,594kg, sendo estes distribuídos nos tratamentos que corresponderam aos sistemas de alimentação: cordeiros lactentes mantidos em pasto de azevém, cordeiros lactentes mantidos em pasto de azevém e suplementados com concentrado em comedouro privativo (creep feeding) e cordeiros lactentes mantidos em pasto de azevém e suplementados com leguminosa no pasto privativo (creep grazing). O suplemento concentrado era composto por milho, farelo de soja e calcário calcítico e foi fornecido ad libitum. O pasto suplementar foi composto pela leguminosa trevo branco. Avaliou-se as características do pasto de azevém e o desempenho dos cordeiros, que foram abatidos ao atingirem o peso corporal de 32 kg. Posteriormente avaliaram-se as características de carcaça, componentes corporais e características da carne dos animais. O delineamento experimental foi o inteiramente casualizado, onde os resultados foram submetidos à análise de variância e as médias comparadas pelo teste Tukey a 5% de significância. A suplementação privativa, concentrada ou através de leguminosa, não elevou o desempenho de cordeiros lactentes mantidos em pastejo de azevém, apesar das diferenças nos teores de fibra detergente neutro e fibra detergente ácido da pastagem consumida pelos animais que foram menores para os suplementados com leguminosa. Cordeiros lactentes mantidos em azevém produzem carcaças similares a dos animais que recebem suplemento, apesar do conteúdo do trato gastrintestinal juntamente com bile e urina e da proporção de esôfago ser maiores (P<0,05) nos cordeiros mantidos em azevém e não suplementados e as proporções de fígado e intestino grosso serem maiores (P<0,05) nos cordeiros suplementados com concentrado. A coloração da carne dos cordeiros foi influenciada (P<0,05) pelo sistema de alimentação, sendo a carne dos cordeiros lactentes que não receberam suplementação considerada a carne menos opaca, menos vermelha e mais amarela. Os teores de colesterol e tocoferol foram maiores (P<0,05) na carne de cordeiros não suplementados, bem como menores teores de cinzas (P<0,05) foram encontrados na carne desses animais. A capacidade de retenção de água foi menor (P<0,05) na carne dos animais suplementados com concentrado. Sabor característico mais intenso (P<0,05) foi observado na carne dos cordeiros que consumiram concentrado e maior maciez (P<0,05) foi encontrada na carne dos cordeiros suplementados com leguminosa. O uso da leguminosa trevo branco como pasto privativo suplementar proporciona rápida terminação de cordeiros com carcaças e carne de qualidade, o que torna este sistema alimentar uma opção para terminação de cordeiros.