Fungal endophytes of the genus Neotyphodium form stable symbiotic associations, with grasses, that are symptomless and generally considered to be mutualistic. The benefits that these fungi confer to their grass hosts are exploited in pastoral agriculture systems. The production of a range of secondary metabolites, specifically alkaloids including peramine and ergovaline can give their host plants an ecological advantage in certain environments. Neotyphodium endophytes are asexual and have lost the ability to transfer horizontally between hosts making seed transmission a vital feature of the association. This thesis reports the occurrence of phenotypically different perennial ryegrass plants (Lolium perenne) in a population infected with Neotyphodium lolii. Here we show that the change in the plants is directly attributable to a variant endophyte that they host. Isolation of the variant endophyte reveals a change in colony growth compared to the wild-type resident endophyte in the population, which has a white and cottony phenotype. Colonies of the variant endophyte are smaller than wild-type colonies and mucoid, with hyphal filaments forming aggregates. Evidence shows that the switch between colony morphologies occurs at a very high frequency, is reversible, and appears to be environmentally induced. This suggests that the switching phenomenon involves gene regulation rather than mutation. When endophyte-free plants are infected, with either white and cottony (wild-type) or mucoid (variant) fungal colonies, they assume a morphology consistent with the state of the fungus at the time of inoculation, that is normal or dwarfed, respectively. In addition, re-isolation of endophyte from either normal or dwarfed plants always yields white and cottony or mucoid colonies, respectively, suggesting that the host environment stabilizes the state of the fungus. Proteomic profiling revealed differences in protein expression between plants infected with either the wild-type or mucoid fungus. Furthermore, host plants containing the mucoid fungus have never flowered or produced seed. Thus, if this change in the fungal symbiont occurs in a competitive natural environment the mucoid fungus and its host plant may not persist beyond the first generation. This thesis provides insights into the plastic nature of fungal endophyte/grass symbiota and discusses possible mechanisms for the observed morphological switching in culture and host dwarfing.

Os cereais destinados a produção de grãos (trigo) e de pastagens (azevém) são alvos espectralmente semelhantes, o que dificulta a sua identificação e discriminação em imagens de satélite ao usar sensoriamento remoto. Entretanto, o ciclo fenológico destas culturas é diferente. A análise do perfil multitemporal dos talhões torna-se a estratégia mais adequada para a discriminação destes alvos, os quais apresentam ciclos fenológicos diferentes, porém são espectralmente semelhantes. Usaram-se as imagens bissemanais (vermelho, infravermelho próximo e infravermelho médio) do produto MOD13q1 do sensor MODIS para aplicar um modelo linear de mistura espectral, do qual foram geradas as imagens fração: vegetação, solo e sombra (água). Utilizou-se a distância de Bhattacharyya para realizar uma análise prévia de separabilidade das classes de trigo e azevém geradas. As composições NDVI do produto MOD13q1 foram utilizadas para a segmentação de imagens e para a geração dos perfis multitemporais, os quais foram elaborados usando pontos de controle (lavouras) coletados em saída de campo com auxílio de GPS. Usaram-se as imagens NDVI 129, 177 e 257 do ano de 2009 na segmentação. O mapeamento foi realizado usando o Isodata implementado no Spring 5.0.3, e várias classificações foram testadas. Os dados do mapeamento final foram comparados com dados do IBGE. A estimativa oficial do IBGE para as pastagens é de 118.657 ha para os 42 municípios da área de estudo (metade sul do RS), uma diferença de 18.018 ha a mais quando comparada com a estimativa do mapeamento, de 100.639 ha. Dos 42 municípios que compõem a área de estudo, 19 apresentaram uma diferença menor do que 1.000 ha ao compararem-se os dados do IBGE com o mapeamento. A estimativa dos cereais destinados a produção de grãos foi de 73.690 ha de acordo com o IBGE, uma diferença de 9.543 ha a menos quando comparada com a estimativa do mapeamento, de 83.233 ha. Dos 42 municípios que compõem a área de estudo, 25 apresentaram uma diferença menor do que 1.000 ha. / When employing remote sensing, the cereals destined for grain production (wheat) and pasture (ryegrass) become spectrally similar targets, which makes their identification and distinction more difficult on satellite images. Nevertheless, the phenological cycle of both cultures is different. Thus, the analysis of the multi-temporal profile of plots results in the most suitable strategy for the distinction of those targets, which have unalike phenological cycles but are spectrally similar. Biweekly images (red, near-infrared and mid-infrared) of the product MOD13q1 from MODIS sensor were employed in order to apply a linear model of spectral mixture, from which fraction images were rendered: vegetation, soil and shade (water). The Bhattacharyya distance was used to perform a previous analysis of the separability of generated wheat and ryegrass classes. The NDVI composites of the product MOD13q1 were used in image segmentation and in the multi-temporal profiles rendering, which were elaborated by exploiting control points (crops) gathered in trip field with the aid of GPS. Images NDVI 129, 177 and 257 from the year 2009 were used in the segmentation. The mapping was carried out by employing the Isodata implemented in Spring 5.0.3, and several classifications were tested. The final mapping’s data were compared with IBGE’s data. According to IBGE’s official estimate, there are 118.657 ha of pastures in the 42 cities of the study area (south half of RS), a difference of 18.018 ha more in comparison to the mapping’s estimate, which is of 100.639 ha. Out of the 42 cities that totalize the study area, 19 presented a difference of less than 1.000 ha when comparing IBGE’s data to the mapping’s data. As stated by IBGE, the estimate of cereals destined for grain production was of 73.690 ha (a difference of 9.543 ha less in comparison to the mapping’s estimate of 83.233 ha. Out of the 42 cities that totalize the study area, 25 showed a difference of less than 1.000 ha.

Os cereais destinados a produção de grãos (trigo) e de pastagens (azevém) são alvos espectralmente semelhantes, o que dificulta a sua identificação e discriminação em imagens de satélite ao usar sensoriamento remoto. Entretanto, o ciclo fenológico destas culturas é diferente. A análise do perfil multitemporal dos talhões torna-se a estratégia mais adequada para a discriminação destes alvos, os quais apresentam ciclos fenológicos diferentes, porém são espectralmente semelhantes. Usaram-se as imagens bissemanais (vermelho, infravermelho próximo e infravermelho médio) do produto MOD13q1 do sensor MODIS para aplicar um modelo linear de mistura espectral, do qual foram geradas as imagens fração: vegetação, solo e sombra (água). Utilizou-se a distância de Bhattacharyya para realizar uma análise prévia de separabilidade das classes de trigo e azevém geradas. As composições NDVI do produto MOD13q1 foram utilizadas para a segmentação de imagens e para a geração dos perfis multitemporais, os quais foram elaborados usando pontos de controle (lavouras) coletados em saída de campo com auxílio de GPS. Usaram-se as imagens NDVI 129, 177 e 257 do ano de 2009 na segmentação. O mapeamento foi realizado usando o Isodata implementado no Spring 5.0.3, e várias classificações foram testadas. Os dados do mapeamento final foram comparados com dados do IBGE. A estimativa oficial do IBGE para as pastagens é de 118.657 ha para os 42 municípios da área de estudo (metade sul do RS), uma diferença de 18.018 ha a mais quando comparada com a estimativa do mapeamento, de 100.639 ha. Dos 42 municípios que compõem a área de estudo, 19 apresentaram uma diferença menor do que 1.000 ha ao compararem-se os dados do IBGE com o mapeamento. A estimativa dos cereais destinados a produção de grãos foi de 73.690 ha de acordo com o IBGE, uma diferença de 9.543 ha a menos quando comparada com a estimativa do mapeamento, de 83.233 ha. Dos 42 municípios que compõem a área de estudo, 25 apresentaram uma diferença menor do que 1.000 ha. / When employing remote sensing, the cereals destined for grain production (wheat) and pasture (ryegrass) become spectrally similar targets, which makes their identification and distinction more difficult on satellite images. Nevertheless, the phenological cycle of both cultures is different. Thus, the analysis of the multi-temporal profile of plots results in the most suitable strategy for the distinction of those targets, which have unalike phenological cycles but are spectrally similar. Biweekly images (red, near-infrared and mid-infrared) of the product MOD13q1 from MODIS sensor were employed in order to apply a linear model of spectral mixture, from which fraction images were rendered: vegetation, soil and shade (water). The Bhattacharyya distance was used to perform a previous analysis of the separability of generated wheat and ryegrass classes. The NDVI composites of the product MOD13q1 were used in image segmentation and in the multi-temporal profiles rendering, which were elaborated by exploiting control points (crops) gathered in trip field with the aid of GPS. Images NDVI 129, 177 and 257 from the year 2009 were used in the segmentation. The mapping was carried out by employing the Isodata implemented in Spring 5.0.3, and several classifications were tested. The final mapping’s data were compared with IBGE’s data. According to IBGE’s official estimate, there are 118.657 ha of pastures in the 42 cities of the study area (south half of RS), a difference of 18.018 ha more in comparison to the mapping’s estimate, which is of 100.639 ha. Out of the 42 cities that totalize the study area, 19 presented a difference of less than 1.000 ha when comparing IBGE’s data to the mapping’s data. As stated by IBGE, the estimate of cereals destined for grain production was of 73.690 ha (a difference of 9.543 ha less in comparison to the mapping’s estimate of 83.233 ha. Out of the 42 cities that totalize the study area, 25 showed a difference of less than 1.000 ha.

Os cereais destinados a produção de grãos (trigo) e de pastagens (azevém) são alvos espectralmente semelhantes, o que dificulta a sua identificação e discriminação em imagens de satélite ao usar sensoriamento remoto. Entretanto, o ciclo fenológico destas culturas é diferente. A análise do perfil multitemporal dos talhões torna-se a estratégia mais adequada para a discriminação destes alvos, os quais apresentam ciclos fenológicos diferentes, porém são espectralmente semelhantes. Usaram-se as imagens bissemanais (vermelho, infravermelho próximo e infravermelho médio) do produto MOD13q1 do sensor MODIS para aplicar um modelo linear de mistura espectral, do qual foram geradas as imagens fração: vegetação, solo e sombra (água). Utilizou-se a distância de Bhattacharyya para realizar uma análise prévia de separabilidade das classes de trigo e azevém geradas. As composições NDVI do produto MOD13q1 foram utilizadas para a segmentação de imagens e para a geração dos perfis multitemporais, os quais foram elaborados usando pontos de controle (lavouras) coletados em saída de campo com auxílio de GPS. Usaram-se as imagens NDVI 129, 177 e 257 do ano de 2009 na segmentação. O mapeamento foi realizado usando o Isodata implementado no Spring 5.0.3, e várias classificações foram testadas. Os dados do mapeamento final foram comparados com dados do IBGE. A estimativa oficial do IBGE para as pastagens é de 118.657 ha para os 42 municípios da área de estudo (metade sul do RS), uma diferença de 18.018 ha a mais quando comparada com a estimativa do mapeamento, de 100.639 ha. Dos 42 municípios que compõem a área de estudo, 19 apresentaram uma diferença menor do que 1.000 ha ao compararem-se os dados do IBGE com o mapeamento. A estimativa dos cereais destinados a produção de grãos foi de 73.690 ha de acordo com o IBGE, uma diferença de 9.543 ha a menos quando comparada com a estimativa do mapeamento, de 83.233 ha. Dos 42 municípios que compõem a área de estudo, 25 apresentaram uma diferença menor do que 1.000 ha. / When employing remote sensing, the cereals destined for grain production (wheat) and pasture (ryegrass) become spectrally similar targets, which makes their identification and distinction more difficult on satellite images. Nevertheless, the phenological cycle of both cultures is different. Thus, the analysis of the multi-temporal profile of plots results in the most suitable strategy for the distinction of those targets, which have unalike phenological cycles but are spectrally similar. Biweekly images (red, near-infrared and mid-infrared) of the product MOD13q1 from MODIS sensor were employed in order to apply a linear model of spectral mixture, from which fraction images were rendered: vegetation, soil and shade (water). The Bhattacharyya distance was used to perform a previous analysis of the separability of generated wheat and ryegrass classes. The NDVI composites of the product MOD13q1 were used in image segmentation and in the multi-temporal profiles rendering, which were elaborated by exploiting control points (crops) gathered in trip field with the aid of GPS. Images NDVI 129, 177 and 257 from the year 2009 were used in the segmentation. The mapping was carried out by employing the Isodata implemented in Spring 5.0.3, and several classifications were tested. The final mapping’s data were compared with IBGE’s data. According to IBGE’s official estimate, there are 118.657 ha of pastures in the 42 cities of the study area (south half of RS), a difference of 18.018 ha more in comparison to the mapping’s estimate, which is of 100.639 ha. Out of the 42 cities that totalize the study area, 19 presented a difference of less than 1.000 ha when comparing IBGE’s data to the mapping’s data. As stated by IBGE, the estimate of cereals destined for grain production was of 73.690 ha (a difference of 9.543 ha less in comparison to the mapping’s estimate of 83.233 ha. Out of the 42 cities that totalize the study area, 25 showed a difference of less than 1.000 ha.

During spring kikuyu-ryegrass pasture has a low dry matter (DM) content (10-12%), is highly digestible and has high levels of soluble carbohydrates. Low rumen pH values have been recorded for cows grazing these pastures even when supplemented with low levels of concentrate. The rumen environment and extent of rumination may therefore be sub-optimal. Supplementation of the pasture with dry roughage may improve rumination, the rumen environment and therefore also milk production performance. The aim of the study was to determine if strategic supplementation of lucerne hay will improve milk production, milk composition and the rumen environment of cows grazing high quality kikuyu/ryegrass during spring and receiving low levels of concentrate. Forty eight high producing Jersey cows were blocked and randomly allocated to one of the following treatments: control (no supplemental roughage), supplementation of 1.0 kg lucerne hay and supplementation of 2.0 kg lucerne hay after morning milking. Cows received 5 kg of dairy concentrate per day during milking. Cows grazed as one group and pasture was allocated to ensure a post grazing height of 10-12 on the rising plate meter (5-6 cm). The average post grazing pasture height for the experimental period was 10.83±1.68 (n=73) on the RPM (5.42 cm). There were no differences (P >0.10) between the treatments for 4% fat corrected milk production, which were 22.2 kg/d for the control, and 22.5 kg/d and 22.9 kg/d for the 1 kg and 2 kg lucerne treatments respectively. Milk fat and protein percentage was not affected (P >0.10) by supplementation of lucerne hay. The milk lactose content of cows receiving the control and 1 kg lucerne hay treatments were higher (P <0.05) than those of cows receiving the 2 kg lucerne hay treatment. Eight rumen cannulated Jersey cows were randomly allocated to either the control or the 2 kg lucerne hay treatment in a cross-over design. These cows grazed together with the cows of the production study and received the same dairy concentrate. Rumen pH was measured for 48 hours with 10 minute intervals using an automated pH logging system. Rumen samples were taken at 08:00, 14:00, 20:00 and 02:00 and were analysed for ammonia-nitrogen (NH3-N), volatile fatty acids (VFA) and pH. An in sacco study was conducted to determine DM and neutral detergent fibre (NDF) disappearance of ryegrass. There were no differences (P >0.10) between treatments in overall mean pH, measured with either the logging systems or with the portable pH meters averaging 6.18 and 6.11 for cows receiving the control and the 2 kg lucerne treatment respectively. The mean rumen NH3-N did not differ (P >0.10) between treatments. The mean concentration of acetic acid and the total VFA concentration was higher (P <0.05) for cows receiving the 2 kg lucerne treatment compared to the control. There were no differences (P >0.10) between treatments in the DM or NDF disappearance of ryegrass after 24 hours. Supplementation of lucerne hay to cows grazing well managed kikuyu-ryegrass pasture during spring did not improve milk production, milk composition, rumen pH or in situ NDF disappearance of ryegrass Results suggest that cows grazing kikuyu/ryegrass pastures supplemented with low levels of concentrate consume sufficient eNDF to maintain a favourable rumen environment and normal milk composition. Copyright / Dissertation (MSc(Agric))--University of Pretoria, 2012. / Animal and Wildlife Sciences / unrestricted

Energy is the first-limiting nutrient for cows grazing pasture therefore, energy supplementation is necessary for high producing animals. In pasture-based systems, the concentrate is fed twice a day in the dairy parlour during the milking procedure. Consumption of large amounts of fermentable carbohydrates results in a drop in rumen pH and this may induce rumen acidosis. This may lead to reduced intake, lower fibre digestion and depressed milk yield. Supplemental yeast offer great possibilities in stabilising the rumen fermentation patterns and, therefore, improving dry matter intakes (DMI). This may increase milk production, milk composition parameters, rumen volatile fatty acid concentrations (VFA) which leads to higher profits. Investigating these responses, a trial was conducted, where live yeast (Levucell SC 10 ME-Titan) was supplemented to Jersey cows grazing ryegrass/kikuyu pastures, supplemented with 6 kg (as is) dairy concentrate per day split over two milking periods. Thirty multiparous high-producing Jersey cows between 30 and 120 days in milk (DIM) were selected, blocked and randomly allocated to control (no yeast) or live yeast treatment groups. Ten fistulated lactating cows were added in a cross-over design (two periods and two treatments) and all 40 cows strip grazed Italian ryegrass (Lollium multiflorum) and kikuyu pastures as one group. A new pasture strip was allocated after each milking and pasture was measured using a rising plate meter (RPM). The yeast product Levucell SC 10 ME – Titan containing Saccharomyces cerevisiae CNCM I-1077 was supplied by Lallemand S.A.S (19 rue des Briquetiers, 31702 Blagnac cedex, France). The Levucell SC 10 ME – Titan is a micro-encapsulated formulation for premix and pelleted feeds. The yeast treatment group had the yeast pelleted in with the dairy concentrate at a concentration of 167 g of yeast per ton of concentrate, to obtain the required intake of 1 g yeast per cow per day as specified by Lallemand. Milk yields were recorded daily and composite milk samples were taken every two weeks to determine, milk fat, protein, lactose, milk urea nitrogen (MUN) and somatic cell count (SCC) contents. The fistulated cows were adapted to their respective diets and treatments for 21 days after which the pH measurment, rumen fluid sampling, and In sacco study were conducted. Milk yield, 4% fat corrected milk (FCM) yield, milk protein and lactose percentages, SCC, body condition score (BCS), and live weight did not differ (P > 0.05) between treatments. The milk fat% however, was higher for the yeast supplemented cows at 4.24% compared to the control group of cows of 3.99% (P < 0.05). The mean acetic and total VFA concentration (mmol/L) for the control treatment was higher compared to the yeast treatment (P < 0.05). There was no difference in the fermentation patterns of VFA, the pH and NH3-N values measured between treatments (P > 0.05). The mean In sacco neutral detergent fibre (NDF), organic matter (OM) and DM disappearance was higher for the yeast treatment group of cows after a 12 and 24 hour incubation compared to the control group (P < 0.05). The mean ruminal NDF disappearance of ryegrass in cows supplemented with yeast increased by 11.9% and 6.3% compared to the control at the 12 and 24 hour incubation periods, respectively. With higher fibre digestibilities in the rumen and more acetate available at the mammary gland and subsequently higher milk fat percentages, the yeast effects on stimulating the cellulolytic bacteria in the rumen, may be a possible explanation for the results in the current study and it is well documented in previous studies. Live yeast supplementation resulted in higher milk fat percentages which improved milk price. / Dissertation (MSc(Agric))--University of Pretoria, 2011. / Animal and Wildlife Sciences / unrestricted

Rumen-undegradable protein might be the first limiting nutrient for high producing dairy cows receiving high levels of maize supplementation while grazing pasture. To test this hypothesis two trials were conducted using fishmeal as a high quality protein source rich in rumen-undegradable protein, Methionine and Lysine. In the first trial cows grazed annual ryegrass for two months in spring. In the second trial cows grazed kikuyu for two months in late summer. In addition to the pasture cows received 6 kg (as is) of a maize-based supplement, including minerals, fed in two equal portions in the milking parlour. A randomised complete block design was used. Three groups of 15 (ryegrass) or 14 (kikuyu trial) cows received control (no fishmeal), low fishmeal (4 % fishmeal replacing maize) or high fishmeal (8 % fishmeal replacing maize) treatments. Multiparous, high producing, Jersey cows in early to mid lactation were used. Milk production was measured and milk samples taken fortnightly. Simultaneous studies were conducted using eight rumen cannulated cows receiving the control and high fishmeal treatments in a cross over design experiment. Ruminal pH, ammonia-N and volatile fatty acid concentrations were measured. In the ryegrass trial milk yield, 4 % fat-corrected milk yield and milk fat and protein percentages of cows on the low and high fishmeal treatments (21.9 and 22.1 kg milk/d, 24.1 and 24.2 kg 4 % fat-corrected milk/d, 4.73 and 4.67 % fat and 3.49 and 3.45 % protein) were significantly higher than the control (20.5 kg milk/d, 20.4 kg 4 % fat-corrected milk/d, 3.97 % fat and 3.25 % protein). There was no treatment effect on milk urea N (16.8, 17.4 and 17.9 mg/dl, for the control, low fishmeal and high fishmeal treatments, respectively). The ruminal ammonia-N concentration was significantly higher in the cows on the high fishmeal treatment than the control (16.67 vs. 14.16 mg/dl). Fishmeal supplementation to cows on ryegrass is profitable under any realistic price scenarios in South Africa. In the kikuyu trial cows on the high fishmeal treatment produced significantly more milk (19.5 kg/d) than the cows on the control (18.2 kg/d), neither differing from the low fishmeal treatment (18.9 kg/d). The cows on the low fishmeal treatment had significantly higher milk fat percentage (4.18 %) than the control (3.71 %), neither differing from the high fishmeal treatment (3.91 %). The cows on the two fishmeal treatments produced significantly more 4 % fat-corrected milk than the control (19.4 and 19.2 vs. 17.3 kg 4 % fat-corrected milk/d). There was no treatment effect on milk protein percentage (3.30, 3.41 and 3.34 % for the control, low and high fishmeal treatments, respectively). Milk urea N was significantly higher for the high fishmeal treatment (10.80 mg/dl) than the control and low fishmeal treatments (9.09 and 9.44 mg/dl). Ruminal ammonia-N concentration was significantly higher in the cows on the high fishmeal treatment than the control (6.52 vs. 4.74 mg/dl). Fishmeal supplementation to cows on kikuyu could be profitable under certain price scenarios. / Dissertation (MSc(Agric) (Animal Science))--University of Pretoria, 2008. / Animal and Wildlife Sciences / unrestricted

Kikuyu is well adapted to the main milk producing areas of the Southern Cape region of South Africa. The strategic incorporation of different types of temperate grasses into kikuyu pastures can increase the seasonal dry matter production, pasture quality, and milk production attainable from these pastures. To determine whether there is production and economical differences between kikuyu based pasture systems, a trial was conducted on the Outeniqua Research Farm near George. The three pasture treatments, namely italian, westerwold, and perennial ryegrass over-sown into kikuyu, were tested. Forty-five Jersey cows were blocked and cows within blocks were randomly allocated to the treatments. The cows received 9 kilograms of pasture (on a dry matter basis) per cow per day, and four kilograms of concentrate per cow per day. Milk production was recorded daily, and milk composition was determined monthly. The cows were weighed and body condition scored monthly. The perennial ryegrass pasture treatment had a higher milk production per hectare (32288 kg/ha) than the westerwold ryegrass pasture treatment (29761 kg/ha) but did not differ from the italian ryegrass pasture treatment (30446 kg/ha). The italian ryegrass pasture treatment had a higher milk protein percentage than the perennial ryegrass pasture treatment (3.84% vs. 3.64%) but did not differ from the westerwold ryegrass pasture treatment (3.75%). When the three pasture treatments were economically compared, the italian ryegrass pasture treatment had the highest margin over specified costs per hectare (R 36,565.03), followed by the perennial (R 33,889.14) and westerwold (R 29,468.09) ryegrass pasture treatments. From the results it seems that the italian ryegrass pasture treatment is the best choice for a kikuyu based pasture system in the Southern Cape region of South Africa. A high level of concentrate supplementation could increase energy intake of grazing dairy cows, but might also reduce fibre digestion within the rumens of high producing dairy cows. To test this hypothesis, two trials were conducted, one during October and November 2007, and the other during March 2008. In both trials twelve rumen cannulated cows were allocated to four groups. Two groups were allocated to each pasture treatment, namely perennial and westerwold ryegrass over-sown into kikuyu. Within each pasture treatment, one group received 4 kg of concentrate per cow per day, and the other 8 kg of concentrate per day. Pasture was allocated at 9 kg per day (DM). Cows were adapted for ten days, after which ruminal pH, and ammonia nitrogen and volatile fatty acid concentration data was collected. An in sacco study was conducted to determine the neutral detergent fibre degradability. After the data was collected, the two groups within each pasture treatment swapped concentrate levels; were adapted, and the same data as described above was collected. During both trials reductions in ruminal pH were observed when a higher amount of concentrate was supplemented. During the first trial there was a significant increase in the time that the ruminal pH remained below pH 5.8 on the westerwold ryegrass pasture treatment (from 80 minutes when the cows received 4 kg of concentrate per day, to 375 minutes when it was increased to 8 kg of concentrate per day). A decrease in neutral detergent fibre degradability was also seen. During the second trial, the percentage of NDF disappearance decreased from 8.45% over a twelve hour period when 4 kg of concentrate was fed, to 4.51% when 8 kg of concentrate was fed on the perennial ryegrass pasture treatment. From the results it appears that feeding a higher level of concentrate supplementation to high producing dairy cows grazing kikuyu pasture systems has a negative effect on neutral detergent fibre digestion within the rumen. It appears that feeding a moderate level of concentrate supplementation when cows are on pasture based systems is more beneficial to the rumen environment and decreases the possibility of sub-clinical ruminal acidosis when cows grazed ryegrass dominant pastures, but had a less pronounced effect when the dominant pasture specie was kikuyu. Future research could examine the relationship between the level of concentrate supplementation and pasture specie more closely, as it would be interesting to find the optimal ratios for each pasture specie. Copyright / Dissertation (MScAgric)--University of Pretoria, 2009. / Animal and Wildlife Sciences / unrestricted

Kikuyu (Pennisetum clandestinum) is highly productive during summer and autumn and capable of supporting high cattle stocking rates., The winter and spring production of kikuyu, however, is low, while forage quality, and consequently milk production per cow, is also low compared to temperate grass species. The aim of this study was to determine the dry matter yield, botanical composition, nutritional value, grazing capacity and milk production potential of irrigated kikuyu over-sown with Italian ryegrass (Lolium multiflorum var. italicum), Westerwolds ryegrass (Lolium multiflorum var. westerwoldicum) or perennial ryegrass (Lolium perenne) under an intensive grazing system with Jersey cows. Calibrations for the rising plate meter (RPM) were developed for the kikuyu-ryegrass systems. These calibrations were evaluated for seasonal variation, linearity and were also combined over seasons, treatments and years to develop a calibration equation that could be used by dairy farmers in the region. The three kikuyu based pasture systems reached their peak growth rates during different months and seasons. All treatments experienced lower growth rates during winter, while peak growth rates occurred during spring for the Italian ryegrass treatment; summer for the Westerwolds ryegrass treatment and late spring/early summer for the perennial ryegrass treatment. All three treatments had similar total annual dry matter yields (kg DM ha-1) during the first year of the study. However, during year 2 the PR treatment had a higher annual DM production than IR and WR treatments. The ability of the PR treatment to maintain DM production during periods when the other treatments underwent a dip in production (WR during spring and IR during summer) enabled the PR treatment to maintain a higher annual DM production during year 2 than the systems based on annual ryegrass species. As the kikuyu component increased in kikuyu-ryegrass pastures from winter to summer, the DM and NDF content increased, while the ME content decreased. All three treatments were deficient in Ca throughout the study and deficient in P during summer and autumn for high producing dairy cows. The Ca:P ratio was below the recommended ratio of 1.6:1 for high producing dairy cows throughout the study. The grazing capacity of all three kikuyu-ryegrass systems was lower during winter and autumn than during spring and summer. The seasonal grazing capacity of the perennial ryegrass treatment, however, was more evenly distributed than that of the Italian and Westerwolds ryegrass treatments. The perennial ryegrass treatment had a lower butterfat and milk production per lactation than the Italian and Westerwolds ryegrass treatments during both years, but had the highest milk production per ha. The latter was a result of the higher annual grazing capacity achieved by the perennial ryegrass treatment. It was thus concluded that, because kikuyu over-sown with perennial ryegrass supported a higher number of animals and had a more evenly distributed fodder-flow, it allowed for higher animal production per ha than kikuyu over-sown with annual ryegrass varieties such as Italian and Westerwolds ryegrass. The pre-grazing and post-grazing regressions of all three the kikuyu based pastures developed for the RPM differed over seasons and years, primarily due to the change in botanical composition from ryegrass based pastures during winter to kikuyu-based pastures in the summer and the associated change in pasture structure. The post-grazing regressions developed during the study did not have a lower degree of accuracy (R2 values) than the pre-grazing regressions. The generalised RPM regression equations developed for kikuyu-ryegrass pastures (consisting of large data sets pooled over treatments and years) could be of use to farmers in the surrounding area, but are not recommended for research purposes due to the large errors and variation associated with such regressions. In the event that farmers employ these calibrations it is important that pasture type and pasture management practices be similar to those utilised during the study. The decision on which kikuyu-ryegrass system to utilize should be based on the specific conditions prevalent on a particular farm, an economic analysis on and a comparison between the three systems, as well as the particular fodder-flow program requirements within the pasture system. / Dissertation (MSc(Agric))--University of Pretoria, 2010. / Plant Production and Soil Science / unrestricted

Dormant bermudagrass (Cynodon dactylon) fairways become matted down and thinned out from winter traffic. This appears to be more of a problem on the coarser textured, winter hardy, improved varieties (e.g., 'Midiron' and 'Vamont') typically used in the colder regions of the upper transition zone. Winter overseeding with cool-season species can improve dormant bermudagrass winter and spring quality. However, bermudagrass persistence can decline in golf course fairways overseeded with ryegrasses (Lolium sp.) for winter quality if ryegrasses persist due to cool spring temperatures, use of persistent ryegrass varieties, and management practices that favor ryegrasses over bermudagrass. Winter overseeding practices that facilitate a reliable transition from overseeded species to bermudagrass would enable transition zone golf courses to overseed bermudagrass fairways for winter-spring quality while allowing the bermudagrass turf to persist without excessive competition from cool-season overseeded species. Studies were conducted to determine the effects of perennial ryegrass (L. perenne) and annual ryegrass (L. multiflorum) seeding rates on winter-spring quality and subsequent transition to bermudagrass in two transition zone locations. Studies were also conducted to determine the potential influence trinexapac-ethyl (TE), a plant growth regulator used by many professional turfgrass managers to suppress foliar growth, has on encouraging overseeded species to transition to bermudagrass. These studies demonstrated that higher overseeding rates (448 and 896 kg ha-1) can provide greater winter-spring quality but do not enhance transition to bermudagrass over lower overseeding rates (224 kg ha-1). This was especially evident in cooler transition zone climate, where higher overseeding rates delayed transition to bermudagrass. Annual ryegrass transitioned to bermudagrass better than perennial ryegrass, but the overseeded winter-spring quality of annual ryegrass was unacceptable. Perennial ryegrass varieties differed in transition. Some perennial ryegrass varieties were too persistent to fully transition to bermudagrass even with the onset of summer temperatures. Intermediate ryegrasses (L. multiflorum x L. perenne) appeared to be promising alternatives to overseeding perennial ryegrass in areas of the transition zone where summer reliance on bermudagrass turf is strongly preferred. Trinexapac-ethyl, when applied to overseeded perennial ryegrasses, did not enhance overseeded ryegrass transition to bermudagrass. Spring TE applications to overseeded perennial ryegrasses were found to reduce or delay their transition to bermudagrass. / Master of Science