O ambiente de terras baixas no sul do Brasil é predominantemente explorado com a cultura do arroz irrigado. Baseado em um sistema agrícola pouco diversificado, é comum o uso sucessivo das mesmas áreas ano após ano, com práticas de manejo que envolvem o revolvimento do solo. Isto acarreta em prejuízos tais como a degradação do solo e recursos naturais, além de recorrente baixa rentabilidade da atividade. O cultivo de espécies forrageiras hibernais, associado com o não revolvimento do solo, pode trazer melhorias ao sistema produtivo, seja com seu uso como plantas de cobertura ou com o pastejo animal. O objetivo deste trabalho foi avaliar os benefícios e potencialidades que a utilização destas espécies podem proporcionar e, para tanto, dois estudos principais foram realizados. O primeiro, conduzido no município de Cachoeirinha, RS, avaliou o estado de agregação e o incremento do teor de carbono orgânico do solo, comparando cultivos sucessivos de arroz irrigado em um experimento de longa duração. Os tratamentos foram um sistema manejado na forma convencional, com revolvimento do solo, e outros três sob semeadura direta, com coberturas de: azevém, cornichão e vegetação espontânea. Os resultados indicaram que, na camada de 0 a 5 cm de profundidade, os tratamentos sob semeadura direta apresentaram maiores teores de carbono orgânico e agregação do que o convencional. Já na camada de 5 a 10 cm, para os agregados, o tratamento azevém se destacou em relação aos demais. O segundo estudo foi conduzido no município de Cristal, RS. Foram avaliadas a produção animal e de forragem durante três anos no período hibernal, em diferentes combinações de sistemas integrados de produção agropecuária (SIPA). Os cultivos estivais trataram-se de arroz irrigado, soja, capim sudão e campo de sucessão, enquanto as pastagens hibernais consistiram de azevém e consórcios desta espécie com trevo branco e cornichão. Os resultados confirmaram a adaptabilidade destas espécies forrageiras ao ambiente de terras baixas e demonstraram as potencialidades que a exploração pecuária possui, sendo necessários, porém, novos estudos para o melhor ajuste do manejo das áreas. Por fim, foi realizado um terceiro estudo, comparando a relação entre a massa de forragem e altura de pastos hibernais em SIPA conduzidos em terras altas com SIPA em terras baixas. A relação no ambiente de terras baixas é menor, corroborando a necessidade de maiores estudos neste ambiente, visto que as alturas ótimas preconizadas para o manejo do pasto se originam de estudos conduzidos em terras altas. / The lowland environment in Southern Brazil is predominantly explored with the irrigated rice crop. Based on a very low diversified system, in such environment is very common the successive use of the same areas year after year, with management practices that involve soil tillage. This leads to damages such as the degradation of soil and natural resources, in addition to recurrent profitability problems. The insertion of winter pasture species associated with the no-till, as cover crops or for animal grazing, may bring improvements to the system. The objective of the current work was to evaluate the benefits and potentialities that the utilization of such plants can provide. For this, two main studies were performed. The first, conducted in the Cachoeirinha County (Rio Grande do Sul State – RS), evaluated the soil aggregation status and its organic carbon content, by comparing successive irrigated rice croppings in a long-term experiment. The treatments consisted of one system under conventional soil tillage and three others under no-till, being the treatments the following cover crops: Italian ryegrass, birdsfoot trefoil and spontaneous vegetation. The results indicated that, in 0 to 5 cm soil layer, the treatments under no-till presented higher organic carbon contents and greater aggregation, as compared to the conventional system. In the 5 to 10 cm soil layer, the treatment with Italian ryegrass has its aggregation highlighted among the others. The second study was conducted in the Cristal County (RS). The animal and pasture production was evaluated during three years in the winter season, under different combinations of integrated crop-livestock systems (ICLS). The summer croppings were irrigated rice, soybean, Sudan grass and a succession field (native pasture), while the winter pastures consisted of Italian ryegrass and its mix with white clover and birdsfoot trefoil. The results confirmed the adaptability and potentiality of such pasture species and livestock exploration in the lowland environment. However, it is needed further studies for a better management adjustment of the areas. Finally, a third study was performed, comparing the relationship between forage mass and winter pasture height in ICLS conducted in highland and lowland. It was demonstrated that in lowland such relationship is lower, corroborating the necessity of more studies in these conditions, because the optimum heights preconized for pasture management are originated from studies conducted in highlands.

Objetivou-se avaliar como diferentes estratégias de manejo do pasto de azevém anual interferem na produção animal, no consumo de forragem e na emissão de metano por ovinos em sistema de integração lavoura-pecuária (SILP) (Capítulo II). Já no Capítulo III objetivou-se avaliar as técnicas dos nalcanos e do nitrogênio fecal na estimativa do consumo de forragem por ovinos em pastos de azevém anual. Os experimentos foram conduzidos nos anos de 2011 e 2012 na Estação Experimental da UFRGS. Foram utilizados ovinos em um SILP de soja e milho no verão, em rotação com azevém anual no inverno. Para ambos os Capítulos (II e III) foram estudados dois métodos de pastoreio (contínuo e rotativo) e duas intensidades de pastejo (moderada e baixa; 2,5 e 5 vezes o potencial de consumo de matéria seca, respectivamente) em um delineamento de blocos casualizados com 3 repetições. Para o Capítulo II, no primeiro experimento os animais experimentais eram cordeiros, enquanto no segundo foram ovelhas em lactação. Os resultados indicaram que o ganho médio diário (GMD) dos cordeiros foi maior (P<0,05) no método de pastoreio continuo que no método de pastoreio rotativo, independente da intensidade de pastejo. O ganho de peso vivo por área (GPV) apresentou a mesma resposta em ambos os experimentos, com maior GPV na intensidade de pastejo moderada (P<0,05). No experimento 1, o consumo de matéria seca (CMS) foi maior para o método de pastoreio continuo, enquanto no experimento 2 não houve diferenças entre métodos e intensidades. As emissões de CH4 diárias por animal não diferiram entre tratamentos em ambos os experimentos (P>0,05), porém, quando expressas em g CH4 kg GPV-1 as emissões foram em média 15,33% maiores (P<0.05) para o método de pastoreio rotativo, independente da intensidade de pastejo. Os resultados afirmam que as emissões de metano por animal não são afetadas pelos tratamentos impostos. Porém, do ponto de vista de sistema o método de pastoreio contínuo o mais eficiente, por apresentar menor emissão de metano por kg de ganho de peso vivo, independente da intensidade de pastejo. Para o Capítulo III, foram utilizados apenas cordeiros. Utilizou-se a metodologia dos n-alcanos e do nitrogênio fecal, por meio de coleta total de fezes com o auxílio de bolsas coletoras. Na avaliação entre os n-alcanos, verificou-se melhores resultados quando utilizando o par C31:C32. Para a metodologia do nitrogênio fecal, as equações propostas por Wang et al. (2009) e por Azevedo (2011) foram as melhores (P<0,05). A técnica do nitrogênio fecal mostrou-se mais acurado do que o uso dos n-alcanos, que superestimou os valores de consumo. / The aim of this study was to evaluate how different management strategies of Italian ryegrass affects animal production, forage intake and methane emissions by sheep in integrated crop-livestock system (ICLS) (Chapter II). In Chapter III, we aimed to evaluate the techniques of n-alkanes and fecal nitrogen in estimating forage intake by sheep grazing on ryegrass. The experiments were conducted in 2011 and 2012 at the UFRGS Experimental Station. The ICLS soybeans and corn crops in summer, in rotation with grazed Italian ryegrass in winter. For both chapters (II and III) two stocking methods (continuous or rotational) and two grazing intensities (moderate and low, 2.5 and 5 times the potential dry matter intake, respectively) were studied in a randomized block design with three replications. In Chapter II, in the first experiment, the experimental animals were lambs, while in the second were lactating ewes. The results indicated that the average daily gain (ADG) of lambs was higher (P<0.05) in the continuous method than in rotational grazing method, regardless of grazing intensity. The live weight gain per area (LWG) showed the same response in both experiments, with higher LWG values in moderate grazing intensity (P<0.05). In experiment I, higher dry matter intake (DMI) values were obtained under continuous grazing, while in experiment II, there no differences between methods and intensities. CH4 emissions per animal and per day did not differ between treatments in both experiments (P>0.05), but when expressed in g CH4 kg-1 LWG emissions were, on average, 15.33% higher (P<0.05) for rotational grazing method, regardless of grazing intensity. Methane emissions per animal were not affected by the treatments applied. However, from system point of view, the continuous grazing method is more efficient, since lower methane emissions per kg of LWG, regardless of grazing intensity, were obtained. In Chapter III, were used only lambs. The methodologies of n-alkanes and fecal nitrogen, were applied through total collection with dung bags. In relation to n-alkanes, better results were obtained when using the pair C31:C32. For the methodology of fecal nitrogen, the equations proposed by Wang et al. (2009) and Azevedo (2011) were the best (P<0.05). The technique of fecal nitrogen proved to be more accurate than the use of n-alkanes, which overestimated the intake.

Nos últimos anos, a lavoura de arroz irrigado no estado do RS aumentou a produtividade em mais de 2,0 Mg ha-1. Este avanço se deve principalmente a alterações no manejo do solo, da cultura e da adubação e à utilização de cultivares modernas, com potencial produtivo cada vez mais alto. Entretanto, deve-se continuar a busca por práticas capazes de aumentar a produtividade do arroz irrigado e, principalmente, a sua sustentabilidade ao longo do tempo. Sistemas de rotação e sucessão de culturas podem ser alternativas viáveis. Diante disso, o objetivo deste trabalho foi avaliar o desempenho agronômico de sistemas de rotação e sucessão de culturas com o arroz irrigado e soja e desenvolver práticas de manejo de culturas capazes de aumentar a sustentabilidade das áreas de várzea utilizadas para a produção de arroz irrigado no estado do RS. Foi, então, conduzido experimento a campo nas safras 2007/08 e 2008/09 na Estação Experimental do Arroz do Instituto Rio Grandense do Arroz, no município de Cachoeirinha-RS. Os tratamentos constaram de três coberturas de solo no inverno, pousio, azevém e azevém + cornichão, e arroz irrigado e soja, no verão, em dois níveis de adubação, em delineamento em blocos casualizados, com parcelas subdivididas com três repetições. Avaliaram-se os seguintes sistemas de rotação e sucessão de culturas: arroz/coberturas de solo/arroz, arroz/coberturas de solo/soja, soja/coberturas de solo/arroz, soja/coberturas de solo/soja. O rendimento do arroz em rotação com soja foi beneficiado em relação à sua sucessão ao próprio arroz. As coberturas de solo no inverno, não constituíram problema para o estabelecimento da cultura do arroz, desde que bem manejadas e a soja é uma alternativa viável para as áreas de várzea, podendo alcançar elevados rendimentos. / In the last few years, flooed rice yields in the state of Rio Grande do Sul – Brazil improved more than 2,0 Mg ha-1. This improvement is mainly due modifications in the soil, culture and nutrition management and the utilization of modern rice cultivars with even more yield potential. However, it is necessary to continue searching for better management practices to enable increase flooded rice productivity, and farming sustainability along time. Culture rotation and succession systems may be valuable alternatives. The objectives of this research were to evaluate the agronomic performance of rotation and succession systems with rice and soybean and to develop management practices to increase the sustainability of lowland areas used for flooded rice cultivation in the State. A field experiment was conducted in 2007/08 and 2008/09 harwest years at Rice Experimental Station of Rice Rio-Grandense Institute (IRGA), in Cachoeirinha - RS. Treatments were three winter cover crops: fallow, ryegrass and ryegrass + birdsfoot trefoil, and flooded rice and soybean, in the summer, with two fertilization levels, arranged in a split-plot design. The follow crop systems were evaluated: rice/cover crops/rice, rice/cover crops/soybean, soybean/cover crops/rice, and soybean/cover crops/soybean. Rice yield in rotation with soybean was higher than rice yield after rice cultivation; well managed winter cover crops were not problem for rice establishment; and soybean showed as a good alternative for low land areas, where can reach high yields.

Objetivou-se avaliar como diferentes estratégias de manejo do pasto de azevém anual interferem na produção animal, no consumo de forragem e na emissão de metano por ovinos em sistema de integração lavoura-pecuária (SILP) (Capítulo II). Já no Capítulo III objetivou-se avaliar as técnicas dos nalcanos e do nitrogênio fecal na estimativa do consumo de forragem por ovinos em pastos de azevém anual. Os experimentos foram conduzidos nos anos de 2011 e 2012 na Estação Experimental da UFRGS. Foram utilizados ovinos em um SILP de soja e milho no verão, em rotação com azevém anual no inverno. Para ambos os Capítulos (II e III) foram estudados dois métodos de pastoreio (contínuo e rotativo) e duas intensidades de pastejo (moderada e baixa; 2,5 e 5 vezes o potencial de consumo de matéria seca, respectivamente) em um delineamento de blocos casualizados com 3 repetições. Para o Capítulo II, no primeiro experimento os animais experimentais eram cordeiros, enquanto no segundo foram ovelhas em lactação. Os resultados indicaram que o ganho médio diário (GMD) dos cordeiros foi maior (P<0,05) no método de pastoreio continuo que no método de pastoreio rotativo, independente da intensidade de pastejo. O ganho de peso vivo por área (GPV) apresentou a mesma resposta em ambos os experimentos, com maior GPV na intensidade de pastejo moderada (P<0,05). No experimento 1, o consumo de matéria seca (CMS) foi maior para o método de pastoreio continuo, enquanto no experimento 2 não houve diferenças entre métodos e intensidades. As emissões de CH4 diárias por animal não diferiram entre tratamentos em ambos os experimentos (P>0,05), porém, quando expressas em g CH4 kg GPV-1 as emissões foram em média 15,33% maiores (P<0.05) para o método de pastoreio rotativo, independente da intensidade de pastejo. Os resultados afirmam que as emissões de metano por animal não são afetadas pelos tratamentos impostos. Porém, do ponto de vista de sistema o método de pastoreio contínuo o mais eficiente, por apresentar menor emissão de metano por kg de ganho de peso vivo, independente da intensidade de pastejo. Para o Capítulo III, foram utilizados apenas cordeiros. Utilizou-se a metodologia dos n-alcanos e do nitrogênio fecal, por meio de coleta total de fezes com o auxílio de bolsas coletoras. Na avaliação entre os n-alcanos, verificou-se melhores resultados quando utilizando o par C31:C32. Para a metodologia do nitrogênio fecal, as equações propostas por Wang et al. (2009) e por Azevedo (2011) foram as melhores (P<0,05). A técnica do nitrogênio fecal mostrou-se mais acurado do que o uso dos n-alcanos, que superestimou os valores de consumo. / The aim of this study was to evaluate how different management strategies of Italian ryegrass affects animal production, forage intake and methane emissions by sheep in integrated crop-livestock system (ICLS) (Chapter II). In Chapter III, we aimed to evaluate the techniques of n-alkanes and fecal nitrogen in estimating forage intake by sheep grazing on ryegrass. The experiments were conducted in 2011 and 2012 at the UFRGS Experimental Station. The ICLS soybeans and corn crops in summer, in rotation with grazed Italian ryegrass in winter. For both chapters (II and III) two stocking methods (continuous or rotational) and two grazing intensities (moderate and low, 2.5 and 5 times the potential dry matter intake, respectively) were studied in a randomized block design with three replications. In Chapter II, in the first experiment, the experimental animals were lambs, while in the second were lactating ewes. The results indicated that the average daily gain (ADG) of lambs was higher (P<0.05) in the continuous method than in rotational grazing method, regardless of grazing intensity. The live weight gain per area (LWG) showed the same response in both experiments, with higher LWG values in moderate grazing intensity (P<0.05). In experiment I, higher dry matter intake (DMI) values were obtained under continuous grazing, while in experiment II, there no differences between methods and intensities. CH4 emissions per animal and per day did not differ between treatments in both experiments (P>0.05), but when expressed in g CH4 kg-1 LWG emissions were, on average, 15.33% higher (P<0.05) for rotational grazing method, regardless of grazing intensity. Methane emissions per animal were not affected by the treatments applied. However, from system point of view, the continuous grazing method is more efficient, since lower methane emissions per kg of LWG, regardless of grazing intensity, were obtained. In Chapter III, were used only lambs. The methodologies of n-alkanes and fecal nitrogen, were applied through total collection with dung bags. In relation to n-alkanes, better results were obtained when using the pair C31:C32. For the methodology of fecal nitrogen, the equations proposed by Wang et al. (2009) and Azevedo (2011) were the best (P<0.05). The technique of fecal nitrogen proved to be more accurate than the use of n-alkanes, which overestimated the intake.

No description available.

Harvest weed seed control (HWSC) methods concentrate, remove, or destroy weed seeds captured by the combine during harvest. Furthermore, chaff lining uses a chute fitted on the back of a combine to concentrate chaff and weed seed therein into a narrow line. Since chaff amount increases with crop yield, studies aimed to determine how varying crop yield and the associated chaff amount will affect chaff lining control of select weed species, while also examining subsequent crop performance. Objective 1 of this work focused on wheat chaff lining (WCL), and objective 2 studied soybean chaff lining (SCL). Weed species of interest included wild mustard (Sinapis arvensis L.) and Italian ryegrass (Lolium perenne ssp. multiflorum L. Husnot) in WCL and Palmer amaranth (Amaranthus palmeri S.) and common ragweed (Ambrosia artemisiifolia L.) subject to SCL. Each weed species was evaluated in separate experiments, and the SCL experiment included an additional factor of with and without a cereal rye cover crop treatment. Chaff lines mimicked harvest across a range of wheat and soybean yields, with equal weed seed additions (based on existing fecundity and seed shatter phenology data) to each chaff line. A conventional harvest (control) and an outside-the-chaff-line treatment were included, where total fecundity or weed seed rain occurring prior to harvest based on weed species were broadcast respectively. Inhibition of crop and weed emergence as a function of yield and the associated chaff amount was also investigated in the greenhouse. Crop yield across treatments at the field scale (accounts for both chaff lines and outside-the-chaff-line), was not affected in double-crop soybean following WCL and full-season soybean following SCL. Field scale wheat yield in WCL compared to conventional harvest was not different, increased, or decreased in 8, 3, and 1 site-years, respectively. WCL reduced total weed emergence over the combined double-crop soybean and winter wheat growing seasons by 43-54% at the field scale. SCL reduced common ragweed emergence in cereal rye by 64% and 85% in 2 of 3 locations across the soybean growing season. The cover crop did not reduce common ragweed emergence while it was growing, but residual mulch in soybean reduced emergence by 39%. No differences were observed in Palmer amaranth emergence during cereal rye growth, however cereal rye decreased total emergence by 41%. In 6 of 7 Palmer amaranth location-years, SCL decreased field scale weed emergence in soybean by 81%. These results indicate chaff may create an unfavorable environment for weed seed emergence. In both WCL and SCL, greater amounts of chaff caused larger reductions in weed emergence. Objective 3 focused on quantifying the above-ground biomass breakdown of soybean plants into chaff, straw, and seed fractions as they are processed and dispensed by various harvesters. Depending on HWSC system, chaff and straw residues may also be destroyed, removed, or concentrated. Therefore, chaff and straw nutrient composition was analyzed to evaluate the nutrient and economic consequences of HWSC. Our results show average soybean harvest index is 0.57:1. Furthermore, chaff and straw residues equal 13.4% and 68.5% of the seed weight, respectively. Using 5-year average fertilizer prices (2017 – 2021), replacement of N, P, K and S in chaff, straw, and the combination of both residues costs USD 1.58, USD 5.88, and USD 7.46, respectively. / Master of Science in Life Sciences / In conventional wheat and soybean production, the primary means of weed control is herbicides. If herbicide use is not diversified, a repeated selection pressure drives weeds to evolve resistance to such chemistries. Producers and researchers alike are constantly looking for new ways to combat weeds and herbicide-resistant issues. Originally developed to control nuisance weeds in Australia, harvest weed seed control (HWSC) offers promise in aiding our current herbicide resistance crisis. To further explain HWSC, it is important to know the harvesting mechanism. Many of the row crops including corn, soybean and wheat are harvested using a combine. Combines cut below or tear off plant material to capture the grain or seed which is processed via a threshing system and separated into three fractions: the seed, chaff, and straw. The grain is allocated to a storage bin and eventually removed from the field. In conventional harvest, the remaining crop residue is spread evenly behind the combine across the field to ensure a balanced distribution of organic matter, nutrients, and residue across the field. There is however more than chaff and straw being dispersed. Weeds present in the field at harvest whose seed is retained at crop maturity and at an elevation above the combine header height will inherently end up inside the combine. HWSC are methods intended to capitalize on the combine capturing weed seeds during harvest. Many HWSC approaches to managing weed seed exist, including destruction, removal and concentration of weed seed. Most of this research focuses on only one method of HWSC, chaff lining. Chaff lining utilizes a chute fitted onto the back of the combine and concentrates weed seed and the chaff fraction only into a narrow line behind the combine. Although not directly known, chaff may inhibit future weed emergence within the line due to a mulching effect, intraspecific competition, a greater degree of rotting and increased seed predators. The chute is inexpensive to construct, and there are no additional labor requirements at harvest making it an appealing HWSC option. There is a limited amount of research on chaff lining in North American cropping systems making it a prime HWSC candidate for this thesis. We were curious if chaff lining could benefit wheat and soybean farmers and if crop yield and the associated chaff amount deposited in chaff lines would have any impact on crops planted and weeds placed in lines. Our results indicate chaff lining does not cause field scale yield consequence in double-crop and full-season soybean following wheat and soybean chaff lining, respectively. The effect of wheat chaff lining on wheat field scale yield was variable, but only caused a yield decrease in 1 of 12 experimental locations. Reductions in weed emergence in chaff lining systems compared to conventional indicate chaff may alter the environment to be unfavorable for weed seed emergence. The final objective of this thesis investigates the economic cost of nutrient loss among HWSC systems. Using average fertilizer prices, the cost to apply N, P, K and S concentrated or lost during HWSC in chaff, straw, and the combination of both residues is USD 1.58, USD 5.88, and USD 7.46, respectively.

Despite the importance of a high white clover (Trifolium repens) content in temperate pastoral systems in terms of livestock performance and nitrogen fixation, the proportion of white clover in grass-clover pastures is often low (<20%). This thesis examined in two experiments whether the white clover content of pastures could be improved by sowing white clover with alternative grass species to diploid perennial ryegrass (Lolium perenne L.). In a pasture experiment, DM production, pasture composition and morphology of grass-clover mixtures was measured over the establishment year (January 2007 to January 2008) where white clover was sown in fine mixtures with diploid perennial ryegrass, tetraploid perennial ryegrass, timothy (Phleum pratense L.) and cocksfoot (Dactylis glomerata L.). Pastures were irrigated and rotationally grazed with on-off grazing with Coopworth ewe hoggets. Total annual DM production of pasture was more than 20% higher in tetraploid (12521 kg DM ha⁻¹) and diploid (11733 kg DM ha⁻¹) perennial ryegrass than timothy (9751 kg DM ha⁻¹) and cocksfoot (9654 kg DM ha⁻¹). However, timothy (5936 kg DM ha⁻¹) and cocksfoot (5311 kg DM ha⁻¹) had more than four times higher white clover annual DM production than tetraploid (1310 kg DM ha⁻¹) and diploid (818 kg DM ha⁻¹) ryegrass. Pasture growth rate at the first three harvests in autumn was significantly greater in tetraploid and diploid ryegrass than timothy and cocksfoot. Timothy and cocksfoot had a higher proportion of white clover than tetraploid and diploid perennial ryegrass throughout the entire year. This was due to more and larger white clover plants in timothy and cocksfoot plots. In a grazing preference experiment, the partial preference of sheep for white clover offered in combination with the same grass species as in the pasture experiment was measured in five grazing tests in May, September, October, November and December 2007. Pastures were sown in January 2007. Paired plots (grass and clover both 4.2 m x 10 m) were grazed by three Coopworth ewe hoggets between 9am and 5pm, and preference was recorded by decline in pasture mass and visual scan sampling for grazing time. Grazing preference for clover was generally low throughout these tests (e.g. average apparent DM intake from clover = 47%; average grazing time from clover = 44%). Several explanations are proposed for this low preference including a high N content and intake rate of the grass relative to the clover. No significant differences were found among the grass treatments in total grass grazing time, total clover grazing time, ruminating time, the proportion of grazing time on clover, selective coefficient for clover and DM intake percentage from clover at any date. There was no significant change in overall sward surface height (SSH) decline among grass treatments throughout all the tests except December 2007 when the overall SSH decline for cocksfoot was significantly lower than the other species. The study indicated that the rapid growth rate of perennial ryegrass in the early phase of pasture establishment, rather than differences in partial preference, was the key factor limiting white clover content in the mixed swards relative to cocksfoot and timothy pastures. It is concluded that high clover-containing pastures capable of delivering high per head performance can be established through the use of slow establishing pasture species such as timothy and cocksfoot.

Thesis (MScAgric)--Stellenbosch University, 2012 / ENGLISH ABSTRACT: Ruminal pH is the rumen condition that varies most. Studying the cause and effect of diurnal variation offers a means of improving ruminal conditions for rumen micro-organisms with subsequent improvements in fibre degradation, milk yields and milk composition. A research project was conducted to test the following hypothesis: feeding 6 kg (as is) concentrate per cow/day in different weight ratios, divided in a morning and an afternoon allocation, will result in an improved ruminal pH profile and a concurrent increase in fibre fermentation, milk yield and improved milk composition. The project was conducted at the Outeniqua Research Farm in the Southern Cape of South Africa. A randomized block design was used and two phases, viz. ryegrass phase and a kikuyu phase, were applied. Each phase was conducted during the growing season of the grass specie used as pasture. A rumen study and a production study were done in each phase. The rumen study used six cannulated multiparous cows per treatment, testing rumen pH, volatile fatty acid (VFA) concentration, in sacco degradation of neutral detergent fibre (NDF) and dry matter (DM). The production study used 42 multiparous cows, blocked according to days in milk (DIM), parity and milk yield, and cows were randomly divided into three treatment groups. The study tested milk yield, milk composition and changes in body weight (BW) and body condition score (BCS). Treatments consisted of a maize based concentrate supplement (6 kg per cow/day, as is) being fed to cows on pasture in different weight ratios between morning and afternoon allocation. Treatments used in the production study were: Concentrate fed: 5 kg during morning; 1 kg during afternoon • Concentrate fed: 4 kg during morning; 2 kg during afternoon • Concentrate fed: 3 kg during morning; 3 kg during afternoon The first and the last treatments mentioned above were used in the rumen studies. Results of the rumen study of the ryegrass phase showed no differences in ruminal pH between treatment means. The time (h) spent below the critical ruminal pH, i.e. 5.8, was of short duration (2.92 to 3.42 hours). The concentration of certain VFA’s differed at times, but the differences were not reflected in graphs and data of the ruminal pH. No differences were observed in in sacco NDF and DM degradation between treatment means. Similar results were mostly obtained in the kikuyu phase. No differences were found in either daily maximum, minimum or mean ruminal pH between treatment means. Though time (h) spent below the critical ruminal pH was of a long duration (7.1 hours) it did not differ between treatments. No differences were observed between treatment means for in sacco NDF and DM degradation. Results of the production study of the ryegrass phase showed no differences in milk yield or milk composition between treatment means. The same was observed in the kikuyu phase except that milk fat was higher in the treatment group that received the 3:3 kg ratio treatment. The fact that treatments did not differ in terms of milk yield and milk composition in the production studies can be attributed to no differences between treatments in terms of rumen parameters observed in the rumen studies. Thus, feeding a higher proportion of concentrate in the morning relative to the afternoon for a total of 6 kg per cow/day does not affect ruminal pH, fibre digestion or milk production. Based on the results of both phases it can be concluded that the null hypothesis should be rejected. / AFRIKAANSE OPSOMMING: Die invloed van kragvoer voedingsstrategieë op rumen parameters, melkproduksie en melksamestelling van Jerseykoeie op raaigras- (Lolium multiflorum) of kikoejoe- (Pennisetum clandestinum) weidings. Die invloed van kragvoer voedingsstrategieë op rumen parameters, melkproduksie en melksamestelling van Jerseykoeie op raaigras- (Lolium multiflorum) of kikoejoe- (Pennisetum clandestinum) weidings. Behandelings toegepas in die produksiestudie het bestaan uit ‘n kragvoeraanvulling met ‘n mieliebasis wat aan koeie op weidings gevoer is in verskillende gewigsverhoudings tussen oggend- en middagvoeding, as volg: Behandelings toegepas in die produksiestudie het bestaan uit ‘n kragvoeraanvulling met ‘n mieliebasis wat aan koeie op weidings gevoer is in verskillende gewigsverhoudings tussen oggend- en middagvoeding, as volg:

Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Kikuyu over-sown with ryegrass forms the basis of pasture based systems in the Southern Cape. During early spring, energy is the first limiting nutrient in kikuyu/ryegrass pasture, supplementation is thus essential. Supplementation consists mainly of high starch concentrates (high maize inclusion), which is expensive and could negatively affect rumen parameters. The objective of this study was to determine if milk production could be improved or maintained, and if the rumen environment would be improved, by replacing high starch concentrates with low starch (high by-product) concentrates for dairy cows on kikuyu/ryegrass pasture. Forty-five multiparous, high producing, lactating Jersey cows [body weight, 340 ± 34.7 kg; milk yield (MY), 19.6 ± 2.23kg/d; days in milk (DIM), 153 ± 33.5; lactation number, 3.6 ± 1.85; (mean ± SD)] were used in the production study. A randomised block design was used. The forty-five cows were allocated to fifteen groups of three each (blocking) on the basis of MY, DIM, and lactation number. Cows from each group were randomly allocated to one of three treatment groups (high starch, medium starch and low starch concentrate supplementation). Cows were fed 6kg (3kg during each milking) concentrate per day and were allocated fresh pasture ad lib after each milking. There were no significant differences (P > 0.05) found in milk yield and fat corrected milk yield between treatment groups. Milk fat percentage was significantly higher (P < 0.05) in the low starch treatment than in the high starch treatment. Milk fat yield was significantly higher (P < 0.05) in both the low starch and the medium starch treatment when compared to the high starch treatment. Milk protein and lactose percentages, as well as milk urea nitrogen and somatic cell count, did not differ significantly (P > 0.05) between treatments. Live weight change, as well as body condition score change, was unaffected (P > 0.05) by treatments indicating body reserves were not used to maintain milk production in the low starch treatment. A rumen metabolism study was also done with ten lactating, cannulated Jersey cows [body weight, 332 ± 56.3 kg; MY, 17.3 ± 1.73kg/d (mean ± SD)] were used. The cows were divided into two groups of five each, on the basis of lactation number, DIM, and MY. The five cows from each group were randomly allocated to one of two treatment groups (high starch and low starch concentrate supplementation) and used in a cross-over design. Cows were fed 6kg concentrate per day and were allocated fresh pasture ad lib after each milking. The volatile fatty acid (VFA) concentration was significantly higher (P < 0.05) in the high starch treatment when compared to the low starch treatment. The individual VFA’s, acetic-, propionic- and butyric acid concentrations were also significantly higher (P < 0.05) in the high starch treatments when compared to the low starch treatment. The acetic to propionic acid ratio was unaffected (P > 0.05) by treatment. Rumen ammonia-nitrogen concentration was significantly higher (P < 0.05) in the high starch treatment. Rumen pH was unaffected (P > 0.05) by supplementation type. The in sacco dry matter and neutral detergent fibre digestibilities of the kikuyu/ryegrass pasture were unaffected (P > 0.05) by treatment type. Results indicated that milk production could be maintained with low starch concentrates which also improved milk composition. Results further suggested that the rumen environment was relatively unaffected by low starch concentrate supplementation. / AFRIKAANSE OPSOMMING: Kikoejoe, oorgesaai met raaigras, vorm die basis van weidingstelsels in the Suid-Kaap. Tydens die lentemaande is energie die eerste beperkende voedingstof op kikoejoe/raaigras weidings, wat kragvoeraanvulling noodsaaklik maak. Aanvulling bestaan grootliks uit hoëstysel-kragvoer (hoë mielieinhoud) wat nie net duur is nie, maar dit kan ook die rumenomgewing benadeel. Die doel van die studie was om vas te stel of melkproduksievlakke onderhou kan word en of rumenomgewing verbeter kan word deur die vervanging van hoëstysel-kragvoer met laestysel-kragvoer (hoë neweprodukinhoud) vir melkkoeie op kikoejoe/raaigras weidingstelsels. Vyf-en-veertig meervoudige pariteit-, hoë produserende, lakterende Jerseykoeie [liggaamsmassa, 340 ± 34.7 kg; melkproduksie, 19.6 ± 2.23kg/d; dae in melk, 153 ± 33.5; laktasienommer, 3.6 ± 1.85; (gem ± standaardafwyking)] is gebruik vir die produksiestudie van die proef. Daar is gebruik gemaak van ‘n ewekansige blokontwerp. Die vyf-en-veertig koeie is opgedeel in vyftien groepe van drie elk, gebaseer op melkproduksie, dae in melk en laktasienommer. Koeie in elke groep is ewekansig aan een van drie behandelings (hoëstysel-, mediumstysel- of laestysel-kragvoeraanvulling) geallokeer. Koeie is daagliks 6kg (3kg tydens twee milkings) kragvoer gevoer en vars weiding was ad lib beskikbaar na elke melking. Daar was geen beduidende verskil (P > 0.05) in melkopbrengs of vet-gekorrigeerde melkopbrengs tussen die drie behandelings nie. Bottervetpersentasie was beduidend hoër (P < 0.05) in die laestyselbehandeling in vergelyking met die hoëstyselbehandeling. Bottervetopbrengs was beduidend hoër (P < 0.05) in beide die laestysel- en mediumstyselbehandelings in vergelyking met die hoëstyselbehandeling. Melkproteïen- en melklaktosepersentasies, asook melkureumstikstof en somatise seltelling, was onveranderd (P > 0.05) tussen behandelinge. Liggaamsmassa en liggaamskondisietelling het geen verskille (P > 0.05) getoon tussen behandelings nie, wat daarop dui dat liggaamsreserwes nie gebruik is om melkproduksie in die laestyselbehandeling te onderhou nie. ‘n Rumenmetabolismestudie is ook uitgevoer met tien lakterende, gekannuleerde Jerseykoeie [liggaamsmassa, 332 ± 56.3 kg; melkproduksie, 17.3 ± 1.73kg/d (gem ± standard afwyking)]. Die koeie is in twee groepe van vyf elk verdeel, gebasseer op laktasienommer, dae in melk en melkproduksie. Die vyf koeie van elke groep is in ‘n omslagontwerp gebruik en is ewekansig aan een van twee behandelings (hoëstysel- of laestysel-kragvoeraanvulling) geallokeer. Koeie het daagliks 6kg kragvoer ontvang en vars weiding was ad lib beskikbaar na elke melking. Die vlugtige vetsuurkonsentrasie was beduidend hoër (P < 0.05) in die hoëstyselbehandeling as in die laestyselbehandeling. Die individuele vlugtige vetsure naamlik asynsuur, propionsuur en bottersuur, was ook beduidend hoër (P < 0.05) in die hoëstyselbehandeling as in die laestyselbehandeling. Die asynsuur- tot propionsuurverhoudings het geen verskille (P > 0.05) tussen behandelings getoon nie. Rumen-ammoniakstikstof was beduidend hoër (P < 0.05) in die hoëstyselbehandeling as in die laestyselbehandeling. Rumen-pH het geen verskille (P > 0.05) getoon tussen behandelings nie. Die in sacco droëmateriaal- en neutraalbestande veselverteerbaarhede van kikoejoe/raaigras weiding het geen verskille (P > 0.05) tussen behandelings getoon nie. Die resultate het aangedui dat melkproduksie onderhou kan word en dat melksamestelling verbeter kan word met laestysel-kragvoeraanvulling. Resultate het ook daarop gedui dat die rumenomgewing nie noodwendig verbeter word deur die aanvulling van laestysel-kragvoer vir koeie op kikoejoe/raaigras weidings nie.

No Instituto de Zootecnia, Nova Odessa, SP, em uma pastagem de capim-aruana (Panicum maximum Jacq. cv. Aruana) utilizada com ovinos em sistema intensivo de produção (irrigação, adubação e lotação rotacionada), foram sobre-semeadas as espécies forrageiras de inverno: aveia preta (Avena strigosa Schreb cv. Comum), azevém anual (Lolium multiflorum Lam. cv. Comum) e trevo branco (Trifolium repens L. cv. Zapicán) com o objetivo de suprir o déficit e melhorar o valor nutritivo da forragem no período crítico do ano. A sobre-semeadura foi efetuada em 14/04/00 e 07/06/01 no primeiro e segundo anos do experimento, respectivamente. Nos dois anos (14/04/00 a 18/01/01 e 07/06/01 a 22/02/02) foram avaliados, em seis períodos de pastejo: massa total de forragem pré-pastejo, sua composição botânica e porcentagem de lâminas foliares, massa de forragem pós-pastejo, acúmulo de forragem (AF) e taxa média diária de acúmulo de forragem (TMDAF) em cada período de rebrotação, altura do dossel forrageiro pré e pós-pastejo, características químicas: proteína bruta (PB), fibra em detergente neutro (FDN), fibra em detergente ácido (FDA), lignina e digestibilidade "in vitro" da matéria seca (DIVMS), nas amostras da massa total de forragem e nas dos componentes botânicos (aruana, aveia preta e azevém) pré-pastejo. O delineamento experimental foi o de blocos completos casualizados (quatro), com duas repetições dentro do bloco e dois tratamentos: 1) capim-aruana exclusivo (AE) e 2) sobre-semeadura da mistura das três espécies forrageiras de inverno (MFI). Os blocos eram pastejados pelo mesmo lote de animais, em sequência, por dois a três dias, até atingir 10 a 15 cm. O trevo-branco não se estabeleceu em ambos os anos. No primeiro ano, a pastagem MFI apresentou maior massa total de forragem do que a pastagem AE no segundo período e na média dos seis períodos. A aveia apresentou a maior contribuição no segundo período e o azevém no terceiro. As pastagens com a MFI apresentaram maiores AF e TMDAF que as pastagens de AE no segundo, quinto e na média dos seis períodos. A PB da forragem na pastagem de capim-aruana exclusivo foi maior em relação à sobre-semeada no terceiro período de pastejo e semelhante nos demais. A PB dos componentes aveia e azevém, no terceiro período, foi menor em relação aos do primeiro e segundo. FDN, FDA e lignina da forragem no tratamento exclusivo foram mais elevados em relação aos do tratamento sobre-semeado, na média dos seis períodos. Aveia e azevém apresentaram FDN mais baixos nos períodos iniciais de crescimento, com aumento no último. A digestibilidade da forragem foi semelhante nos dois tratamentos, em todos os períodos de avaliação. No segundo ano, a massa total de forragem apresentou quantidades semelhantes entre as duas pastagens ao longo dos seis períodos e na sua média. A aveia esteve mais presente no primeiro período e o azevém no terceiro. Não houve diferença entre tipos de pastagem para AF e TMDAF em nenhum dos seis períodos, nem na sua média. Para o componente aruana a porcentagem de lâminas foi semelhante entre os dois tipos de pastagem e para a aveia e azevém, as menores porcentagens ocorreram no período final dos seus ciclos vegetativos, em ambos os anos. O teor de PB da massa total de forragem da pastagem de capim-aruana exclusivo foi maior que o da pastagem sobre-semeada, no quarto período mas semelhante nos demais e na média dos períodos. Os teores de PB da aveia e do azevém decresceram ao longo dos períodos de pastejo. Os teores de FDN, FDA, lignina e DIVMS da forragem foram semelhantes entre as duas pastagens na média e ao longo dos seis períodos, exceto para FDN no segundo período. A aveia e o azevém apresentaram os maiores teores de FDN, FDA e lignina no último período de pastejo. A DIVMS do azevém manteve-se constante nos dois primeiros períodos de pastejo diminuindo no último. Pastos de capim-aruana convenientemente adubados e irrigados, que recebam sobre-semeadura com espécies forrageiras de inverno, produzem mais forragem no período crítico mas com valor nutritivo semelhante em relação a pastos não sobre-semeados, nas condições do Estado de São Paulo. Pastos deste capim, não sobre-semeados, mas que recebam adubação e irrigação também apresentam boa produção e valor nutritivo nesta época. / At Instituto de Zootecnia, Nova Odessa, SP, in a pasture of aruanagrass (Panicum maximum Jacq. cv. Aruana), grazed by sheep in an intensive production system (irrigation, fertilization and rotational stocking), it was introduced a three winter forage species: black oat (Avena strigosa Schreb. cv. Common), italian ryegrass (Lolium multiflorum Lam. cv. Common) and white clover (Trifolium repens L. cv. Zapican) with the objective of increasing the forage supply and its nutritive value during the dry winter period. The mixture was broadcasted sown over the grass on 04-14-00 and 06-07-01 in two years of experiment. From 04-14-00 to 01-18-01 and 06-07-01 to 02-22-02 it was evaluated, in six annual grazing periods, the forage mass, its botanical composition and leaf blades percentage pre grazing, residual mass post grazing, forage accumulation (FA) and mean forage accumulation daily rate (MFADR) in each regrowth period and sward heigth pre and post grazing, the chemical characteristics: crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin and in vitro dry matter digestibility (IVDMD) in the forage on offer and in its botanical components. The experimental design was a completely randomized block (four) with two replications within the block. The treatments were: 1) grass alone and 2) the grass oversown with the mixture of the winter forages. The blocks were grazed by the same group of sheep in sequence for two or three days until the sward height reached to 10-15 cm. The white clover did not establish. In the first year the oversown treatment presented higher total forage mass than the control in the second periods and in the mean of the six periods. The black oat presented higher contribution in the second period and italian ryegrass in the third. The oversown pastures presented higher FA and MFADR than the single aruanagrass pastures, in the second, fifth and in the mean of the six periods. The CP in the forage from the grass pasture alone was greater than the one of the oversown pasture in the third period, and similar in the others. Oat and ryegrass CP was lower in the third period than the ones of the first and second ones. NDF, ADF and lignin in the forage from the grass pasture alone were greater than the ones of the oversown pasture. Oat and ryegrass NDF was lowest in the initial growth periods, increasing in the final. Forage IVDMD from the two treatments were similar in all evaluation periods. In the second year, the total forage mass was similar in the two pasture treatments in all grazing periods and in their means. The black oat contribution was higher in the first period and the one of italian ryegrass in the third. The FA and the MFADR were similar in the two pasture systems. The leaf blades percentage of aruanagrass was similar in the two pastures in all periods and the ones of black oat and italian ryegrass were lower in the final period compared to the preceeding ones, in the two years. The CP in the forage from the grass pasture alone was greater than the one of the oversown pasture in the fourth period, and similar in the others. Oat and ryegrass CP decreased along the grazing periods. NDF, ADF, lignin and IVDMD of the forage from the two treatments were similar in all evaluation periods. Oat and ryegrass NDF, ADF and lignin were greater in the last grazing period. Ryegrass IVDMD from the first two periods were similar and decreased in the final. For the São Paulo State conditions, adequately fertilized and irrigated aruanagrass pastures, when oversown with winter annual forages, yield more than single aruanagrass ones during the dry winter period but with similar nutritive value. Single aruanagrass pastures when fertilized and irrigated present also good forage yields with good nutritive value during this time.