Graduation date: 1996

Grazing cattle on alfalfa (Medicago sativa L.) would be economically beneficial, but its rapid initial rate of protein degradation results in pasture bloat, low efficiency of protein utilization and excessive N pollution into the environment. Introducing a gene that stimulates the accumulation of mono/polymeric anthocyanidins might reduce the ruminal protein degradation rate and reduce bloat related foam stability. The overall objective of this thesis was to evaluate newly developed anthocyanidin-accumulating Lc-alfalfa progeny for nutritional properties (composition, site of degradation and molecular structure), environmental emissions and bloat characteristics. The objective of the first study was to determine survival and phytochemical and chemical profiles of Lc-alfalfa progeny (BeavLc1, RambLc3 and RangLc4) and their non-transgenic (NT) parental cultivars (Beaver, Rambler and Rangelander). Lc-alfalfa forage accumulated enhanced amounts of anthocyanidin, with an average concentration of 197.4 µg/g DM, while proanthocyanidin (i.e. condensed tannins) were not detected. Both of these metabolites were absent in the NT-parental varieties. Lc-alfalfa progeny had ~3 % less crude protein (CP) and ~3 % more carbohydrates (CHO), which resulted in their 11 g/kg lower N:CHO ratio compared with NT-alfalfa. Total rumen-degradable N:CHO ratio based on chemical analysis was 12.9 g/kg lower in Lc-alfalfa compared with NT-alfalfa. The objective of the second study was to evaluate in vitro degradation, fermentation and microbial-N partitioning of three forage color phenotypes [green, light purple-green (LPG) and purple-green (PG)] within Lc-progeny and their parental green NT-alfalfa varieties. Purple-green-Lc alfalfa accumulated more anthocyanidin than Green-Lc with LPG-Lc intermediate. Gas, methane and ammonia accumulation rates were slower for the two purple-Lc phenotypes compared with NT-alfalfa with Green-Lc intermediate. Effective degradable DM and N were lower in the three Lc-phenotypes compared with NT-alfalfa. Anthocyanidin concentration correlated negatively with gas and methane production rates and effective degradability of DM and N. The objectives of the third study were to evaluate in situ ruminal degradation characteristics and synchronization ratios, and to model protein availability to dairy cattle and net energy for lactation of three Lc-alfalfa progenies, BeavLc1, RambLc3 and RangLc4 and the cultivar AC Grazeland (selected for a low initial rate of ruminal degradation). Anthocyanidin accumulation was on average 163.4 ìg/g DM in the three Lc-progeny while AC Grazeland did not accumulate anthocyanidin. The basic chemical composition of the original samples, soluble and potentially degradable fractions and degradation characteristics of crude protein and carbohydrates were similar in Lc-alfalfa and AC Grazeland. The undegradable in situ crude protein and neutral detergent fiber fraction were, respectively, 1.3 %CP and 4.8 %CHO lower in the three Lc-progeny compared with AC Grazeland. Lc-alfalfa had a 0.34 MJ/kg DM higher net energy for lactation and tended to have a 11.9, 6.9 and 8.4 g/kg DM higher rumen degradable protein, rumen degraded protein balance and intestinal available protein, respectively, compared with AC Grazeland,. The hourly rumen degraded protein balance included an initial and substantial peak (over-supply) of protein relative to energy which was highest in RangLc4 and lowest in RambLc3. The hourly rumen degraded protein balance between 4 and 24 h was similar and more balanced for all four alfalfa populations. The objective of the fourth study was to determine foam formation and stability in vitro from aqueous leaf extracts of three Lc-alfalfa progeny (BeavLc1, RambLc3, RangLc4), parental NT-alfalfa and AC Grazeland (bloat reduced cultivar) harvested in the field at 07:00 or 18:00 h. Anthocyanidin accumulation averaged 247.5 ìg/g DM in the leaves of the three Lc-progeny. There was an interaction between population and harvest time for the foam parameters. Initial foam volume (0 min) and final foam volume (150 min) at 07:00 h were lower for AC Grazeland compared with all other treatments and lower for RangLc4 compared with the other two Lc-progeny at 0 min and NT-alfalfa at 150 min; while from the 18:00 h harvest, initial foam volume was larger for NT-alfalfa and final foam volume was larger for RambLc3 compared with AC Grazeland, BeavLc1 and RangLc4. Foam formation correlated positively (R = 0.30 to 0.44) with leaf DM content, leaf extract protein and ethanol-film content, spectroscopic vibration intensity due to all carbohydrates (CHOVI) and amide I:amide II ratio and negatively (R = -0.33 and -0.34; P<0.05) with á-helix:â-sheet ratio and amide I:CHOVI. Final foam volume correlated negatively (R = -0.53 to -0.25; P<0.05) with leaf extract pH, spectroscopic vibration intensity due to all protein structures, structural carbohydrates (SCVI) and lipids (CH2 and CH3 asymmetric stretching) and amide I:CHOVI ratio and corelated positively (R = 0.39 to 0.44; P<0.05) with CHOVI, amideI:SCVI ratio and CHOVI:SCVI ratio. In conclusion, all Lc-alfalfa progeny and phenotypes accumulated anthocyanidin in their forage. Lc-alfalfa progeny had lower protein and higher carbohydrate content which improved the nitrogen to carbohydrate balance compared to their parental NT-alfalfa cultivars. Rate of fermentation and effective degradability in vitro reduced for both purple anthocyanidin-accumulating Lc-alfalfa phenotypes compared with NT-alfalfa. Intestinal protein availability tended to be higher and net energy for lactation was higher from Lc-alfalfa progeny for dairy cattle compared with AC Grazeland. Foaming properties were reduced in Lc-alfalfa progeny compared with parental non-transgenic alfalfa but not compared with AC Grazeland. However, differences between the Lc-alfalfa progeny and other cultivars were small. Therefore, further increases in mono/polymeric anthocyanidin accumulation in alfalfa are required in order to develop an alfalfa cultivar with superior nutritional and bloat preventing characteristics compared to currently available alfalfa cultivars.

Grazing cattle on alfalfa (Medicago sativa L.) would be economically beneficial, but its rapid initial rate of protein degradation results in pasture bloat, low efficiency of protein utilization and excessive N pollution into the environment. Introducing a gene that stimulates the accumulation of mono/polymeric anthocyanidins might reduce the ruminal protein degradation rate and reduce bloat related foam stability. The overall objective of this thesis was to evaluate newly developed anthocyanidin-accumulating Lc-alfalfa progeny for nutritional properties (composition, site of degradation and molecular structure), environmental emissions and bloat characteristics. The objective of the first study was to determine survival and phytochemical and chemical profiles of Lc-alfalfa progeny (BeavLc1, RambLc3 and RangLc4) and their non-transgenic (NT) parental cultivars (Beaver, Rambler and Rangelander). Lc-alfalfa forage accumulated enhanced amounts of anthocyanidin, with an average concentration of 197.4 µg/g DM, while proanthocyanidin (i.e. condensed tannins) were not detected. Both of these metabolites were absent in the NT-parental varieties. Lc-alfalfa progeny had ~3 % less crude protein (CP) and ~3 % more carbohydrates (CHO), which resulted in their 11 g/kg lower N:CHO ratio compared with NT-alfalfa. Total rumen-degradable N:CHO ratio based on chemical analysis was 12.9 g/kg lower in Lc-alfalfa compared with NT-alfalfa. The objective of the second study was to evaluate in vitro degradation, fermentation and microbial-N partitioning of three forage color phenotypes [green, light purple-green (LPG) and purple-green (PG)] within Lc-progeny and their parental green NT-alfalfa varieties. Purple-green-Lc alfalfa accumulated more anthocyanidin than Green-Lc with LPG-Lc intermediate. Gas, methane and ammonia accumulation rates were slower for the two purple-Lc phenotypes compared with NT-alfalfa with Green-Lc intermediate. Effective degradable DM and N were lower in the three Lc-phenotypes compared with NT-alfalfa. Anthocyanidin concentration correlated negatively with gas and methane production rates and effective degradability of DM and N. The objectives of the third study were to evaluate in situ ruminal degradation characteristics and synchronization ratios, and to model protein availability to dairy cattle and net energy for lactation of three Lc-alfalfa progenies, BeavLc1, RambLc3 and RangLc4 and the cultivar AC Grazeland (selected for a low initial rate of ruminal degradation). Anthocyanidin accumulation was on average 163.4 ìg/g DM in the three Lc-progeny while AC Grazeland did not accumulate anthocyanidin. The basic chemical composition of the original samples, soluble and potentially degradable fractions and degradation characteristics of crude protein and carbohydrates were similar in Lc-alfalfa and AC Grazeland. The undegradable in situ crude protein and neutral detergent fiber fraction were, respectively, 1.3 %CP and 4.8 %CHO lower in the three Lc-progeny compared with AC Grazeland. Lc-alfalfa had a 0.34 MJ/kg DM higher net energy for lactation and tended to have a 11.9, 6.9 and 8.4 g/kg DM higher rumen degradable protein, rumen degraded protein balance and intestinal available protein, respectively, compared with AC Grazeland,. The hourly rumen degraded protein balance included an initial and substantial peak (over-supply) of protein relative to energy which was highest in RangLc4 and lowest in RambLc3. The hourly rumen degraded protein balance between 4 and 24 h was similar and more balanced for all four alfalfa populations. The objective of the fourth study was to determine foam formation and stability in vitro from aqueous leaf extracts of three Lc-alfalfa progeny (BeavLc1, RambLc3, RangLc4), parental NT-alfalfa and AC Grazeland (bloat reduced cultivar) harvested in the field at 07:00 or 18:00 h. Anthocyanidin accumulation averaged 247.5 ìg/g DM in the leaves of the three Lc-progeny. There was an interaction between population and harvest time for the foam parameters. Initial foam volume (0 min) and final foam volume (150 min) at 07:00 h were lower for AC Grazeland compared with all other treatments and lower for RangLc4 compared with the other two Lc-progeny at 0 min and NT-alfalfa at 150 min; while from the 18:00 h harvest, initial foam volume was larger for NT-alfalfa and final foam volume was larger for RambLc3 compared with AC Grazeland, BeavLc1 and RangLc4. Foam formation correlated positively (R = 0.30 to 0.44) with leaf DM content, leaf extract protein and ethanol-film content, spectroscopic vibration intensity due to all carbohydrates (CHOVI) and amide I:amide II ratio and negatively (R = -0.33 and -0.34; P<0.05) with á-helix:â-sheet ratio and amide I:CHOVI. Final foam volume correlated negatively (R = -0.53 to -0.25; P<0.05) with leaf extract pH, spectroscopic vibration intensity due to all protein structures, structural carbohydrates (SCVI) and lipids (CH2 and CH3 asymmetric stretching) and amide I:CHOVI ratio and corelated positively (R = 0.39 to 0.44; P<0.05) with CHOVI, amideI:SCVI ratio and CHOVI:SCVI ratio. In conclusion, all Lc-alfalfa progeny and phenotypes accumulated anthocyanidin in their forage. Lc-alfalfa progeny had lower protein and higher carbohydrate content which improved the nitrogen to carbohydrate balance compared to their parental NT-alfalfa cultivars. Rate of fermentation and effective degradability in vitro reduced for both purple anthocyanidin-accumulating Lc-alfalfa phenotypes compared with NT-alfalfa. Intestinal protein availability tended to be higher and net energy for lactation was higher from Lc-alfalfa progeny for dairy cattle compared with AC Grazeland. Foaming properties were reduced in Lc-alfalfa progeny compared with parental non-transgenic alfalfa but not compared with AC Grazeland. However, differences between the Lc-alfalfa progeny and other cultivars were small. Therefore, further increases in mono/polymeric anthocyanidin accumulation in alfalfa are required in order to develop an alfalfa cultivar with superior nutritional and bloat preventing characteristics compared to currently available alfalfa cultivars.

Natural forest dynamics is a foundational topic of forest science. A new Wood Pasture hypothesis considering large herbivore as driving force in forest ecosystem is now challenging the traditional High Forest hypothesis, in which vegetation is regarded as main driving force. In this study, a model-based approach is applied to investigate differences between these two hypotheses and the determine factors in the system. A theoretical landscape of 1 km²formed by 100*100 cells is set up with 100 vegetation patches and free moving herbivores on. Our null hypothesis that herbivores make no difference in vegetation dynamics especially at canopy level is rejected. It is found that synchronization of herbivore behaviors is the most influencing factor of how a landscape might be shaped. It is also found that landscape could be a mosaic of both high forest and wood pasture depends on large herbivore’s herd size.

Who uses the forage resources under a communal land tenure system? Using data from a Mexican Indian community with a history of communal land tenure extending prior to the Conquest, the research explores and attempts to answer this question. The analysis is based on 1970 socio-economic data for 533 households, secondary sources, and 1987 field observations in a community of Zapotec farmers in the State of Oaxaca, Mexico. The factors influencing who uses the communal resources include livestock ownership, wealth ranking, migration history, and participation in the local labor market. Although all members of the community have the right to graze animals on the commons, only a fraction of the wealthier households exercise this right. Consequently grazing pressure is minimized (reduced) compared to the potential grazing pressure that otherwise would be exerted if all the members of the community were to exercise their rights to use the forage resources at the same time.

This research was conducted at the University of KwaZulu-Natal, Pietermaritzburg, South Africa. The research encompasses five different studies to assess nutrient cycling in intensive and extensive grazing systems with a view to optimising livestock production. The first study was designed to assess the effect of teff-lucerne mixtures on teff, lucerne and teff-lucerne mixture yields. Lucerne and teff-lucerne mixtures benefited from the association. The overall soil N content of the teff-lucerne mixture plots was greater than the teff alone plots. The second study focused on teff-leucaena association evaluation. It had two leucaena plant row spacings as treatments, 180cm and 120cm, respectively. Teff grown in mixture with leucaena produced a total teff dry matter (DM) of 7931.57 kg ha¯¹ for the 180cm row spacing and 8329.57 for the 120cm row spacing compared to the 3548.93 kg ha¯¹ of DM obtained from the teff alone treatment. The teff-Ieucaena stand also had a greater DM yield response to leucaena row spacing compared to the teff alone. In terms of nutritive quality, all stands from the teff-leucaena plots were better than the quality obtained from the teff alone plots. Total N content of teff from the l80cm row spacing was 21.83 g kg¯¹ and that from the 120cm 16.07 g kg¯¹ compared to the total nitrogen (N) content of 19.77 g kg¯¹ of the teff alone treatment. The total phosphorus (P) content was 2.73, 1.96 and 2.07 g kg¯¹ for the 180cm, 120cm and teff alone treatments respectively. However, the total soil N content was higher for the teff alone plot than for the teff-leucaena plots, which are 1.91, 1.48 and 100 g kg¯¹ for the teff alone, 180cm and 120cm treatments respectively. The third study was designed to assess the effects of different N fertilizer application rates on teff yield response. The rates applied were 0, 50, 100 and 150 kg N ha¯¹. There was significant difference in teff response of the three N fertilizer application rates compared to the control and teff DM yield response was lower for the 150 kg N ha¯¹ (838 kg ha¯¹) treatment compared to the control (553 kg ha¯¹). Both teff DM and nutritive value were higher in the plots treated with N fertilizer than in the plot which received no N fertilizer (control). The soil N content was also higher in those plots treated with N fertilizer. Study four was conducted on the Department of Grassland Science's grassland management techniques trial field at Ukulinga. The effects of nutrient cycling under different management techniques such as burning, mowing and grazing on grass yield response, plant quality and soil nutrients were assessed. However, the response of grass DM yield and P content was not significant but the three treatments had a significant effect on grass N content. Their effect on soil N content was also significant and the grazing plot had the greatest soil N levels. The last study was conducted in the rural areas of Okhombe and Zwelitsha to assess the effects of grazing intensity on grass yield response, plant quality and soil nutrient status at different distances from homesteads. Grass DM yield and nutritive value declined when distance from the homestead increased. The soil N content also was higher nearer to the homestead than further away. Most farmers, particularly in developing countries including those in Eritrea, often experience that their animals prefer forages from some plants such as lucerne, leucaena, and other indigenous leguminous plants. They also observe that they get greater yield from crops grown near leguminous plants or in rotation with legumes. They are also still using manure from their animals to fertilize their croplands. Therefore, it is still the duty of the researchers to demonstrate to farmers on farm studies to convince farmers that it is because leguminous plants have the ability to add quality and quantity to the feed of the animals and soil nutrients to the croplands. Hopefully, this study will convey to farmers the use of growing integrated grassllegume pastures and crops, and illustrate that livestock have their own role in transporting nutrients and hence use them as good means of distributors of soil nutrients. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.

No description available.

In New Zealand, native shrubs are considered an important potential carbon-sink in disturbed or abandoned land (e.g., pastoral land that is unsustainable for long-term pastoral agriculture). However, the impact of varying environmental drivers on carbon uptake from photosynthesis and carbon loss from respiration of a developing shrubland remains uncertain. In this study, the effects of both temperature and soil water content (θ) on photosynthesis and respiration were examined under controlled growth cabinet and field conditions in a pasture grass and the native shrub, kānuka (Kunzea ericoides var. ericoides). The purpose of the investigation was to assess the combined impacts of varying temperature and θ on canopy processes and to disentangle the effects of θ on photosynthesis and respiration for the two different plant types. A controlled growth cabinet study (Chapter 2) showed that θ had a greater effect on the short-term temperature response of photosynthesis than the temperature response of respiration. The optimum value of θ for net photosynthesis was around 30 % for both kānuka and the grass. Statistical analysis showed that the temperature sensitivity of photosynthetic parameters was similar for both plant types, but the sensitivity of respiratory parameters was different. Reduction in θ induced an inhibition of photosynthetic capacity in both plant types. The response of respiratory parameters to θ was not related to substrate limitations, however available evidence suggests that it is likely to be a species dependent plant mechanism in regulating the cost of maintenance due to reduced photosynthate assimilation and decreasing energy supply to support the activity of respiratory enzymes. Results obtained from a field study (Chapter 3) showed that photosynthesis and respiration in the grass and kānuka were sensitive to seasonal changes in temperature and θ. Photosynthetic parameters showed little acclimation following changes in seasonal growth conditions. In contrast, respiratory parameters tended to acclimate more strongly. Respiratory acclimation to multiple environmental conditions was characterised by changes in temperature sensitivity and a shift in the response of respiration to temperature, demonstrating the involvement of both ‘Type I’ and ‘Type II’ acclimation in both plant types. The results from controlled growth cabinet and field studies were used to drive a leaf level model that integrates the responses of photosynthesis and respiration to changes in temperature and θ and incorporates acclimation using variable photosynthetic and respiratory parameters (Chapter 4). This model was used to estimate the annual canopy carbon exchange of the grass and kānuka in response to seasonal changes and to predict changes in canopy carbon exchange under varying future climate change scenarios. The model highlighted the importance of considering seasonally-acclimated parameters in estimating canopy carbon exchange of both plant types to concurrent changes in multiple environmental variables. The overall results support the conclusion that understanding the combined effects of environmental variables on canopy processes is essential for predicting canopy net carbon exchange of a pasture-shrub system in a changing global environment. It has been shown here that the rate of increase in photosynthesis with increasing θ is greater than that of respiration which results in a progressively greater apparent carbon gain at moderate values of θ. Moreover, the impact of lower values of θ, which reduced the apparent sensitivity of respiration to temperature, may effectively decrease the rate of respiration during warmer summer months and enhance thermal acclimation via downregulation of respiration. Therefore, considering the influence of soil water conditions on the temperature sensitivity of photosynthetic and respiratory model parameters has important implications for precisely predicting the net carbon exchange of a pasture-shrub system.

Tall ironweed (Vernonia altissima) and Canada thistle (Cirsium arvense) control in cool season grass pastures was evaluated in 2007 and 2008. Tall ironweed was evaluated in Fayette and Boone Counties, KY and Canada thistle was evaluated at Spindletop Research Farm. Herbicides applied selectively with a rope-wick were compared to a broadcast foliar spray. Treatments were a broadcast treatment, of aminopyralid + 2, 4-D and six rope-wick treatments: aminopyralid at three concentrations, glyphosate, triclopyr and clopyralid at one concentration each. The Boone County location had five broadcast foliar treatments: aminopyralid at three rates, triclopyr + fluroxpyr, and 2,4-D + triclopyr. The Canada thistle study consisted of the same six rope-wick treatments as the Fayette County tall ironweed study. A broadcast treatment of aminopyralid at 70 g a.e./ha was included in 2008. Studies were evaluated 1, 2, 3, 4, 8 and 52 weeks after treatment. Aminopyralid plus 2,4-D provided 86% control of tall ironweed 52 WAT. Aminopyralid at 20% v/v controlled 65% of tall ironweed. Canada thistle control 52 WAT ranged from 0 to 25% control for the six ropewick treatments.

No description available.