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Three studies were conducted to evaluate a method for estimating grass and legume fractions in extrusa samples from esophageally-fistulated animals, based on different concentrations of neutral detergent fiber (NDF), Ca and lignin in grasses and legumes. In experiment 1, NDF, Ca and lignin concentrations were measured in mixtures of six combinations of red clover-orchardgrass and alfalfa-tall fescue (100:0; 80:20; 60:40; 40:60; 20:80; 0:100). The R² values were .90, .80 and .22 for Ca, NDF and lignin, respectively. In experiment 2, fresh tall fescue and red clover were collected during 8 d, mixed in the same proportions as in experiment 1, and each fraction was fed to esophageally-fistulated steers. Extrusa samples were collected without loss of saliva. Regression equations developed were y= 1.08 - .008x (R²= .91) for Ca and y= 50.9 + .22x (R²= .74) for NDF, where x represents % grass. In experiment 3, two esophageally-fistulated steers were allowed to graze in 20 4 X 4 m² plots of red clover and tall fescue after fasting overnight. The grass/legume proportions of the extrusas and the grab samples were extrapolated from slopes. The botanical composition of grab samples differed (P<.001) from that of extrusas for both components and for both animals. Extrapolation from NDF values tended to overestimate the proportion of grass in extrusa samples and underestimate it in grab samples. Calcium was not affected by salivation and mastication and was more reliable than NDF. Lignin was not an accurate predictor. / M.S.

Experiments were conducted to study the chemical changes and microanatomical characteristics associated with maturity, rate and extent of DM digestion, behavior and extent of tissue digestion and mode of microbial attack during simulated ruminal digestion. Barley and millet plants were collected at four different stages of development: vegetative, boot, heading and mature. Berseem was harvested at three different stages of development: vegetative, bud and full bloom. For the first three stages of grasses and legumes, the plants were separated into three botanical fractions: leaf blades (leaflets), leaf sheaths (petioles) and stems. Grasses were harvested at mature stage and barley seeds were separated by thresher and millet seed by hand cutting the head. Straws were chopped in a hammer mill through a 2.5 cm screen and treated: 1) no added water (control), 40% added water, 2) alone or with 3) urea, 4) NH₄OH and 5) H₂O₂ at pH 11.5. Grasses showed higher (P<.05) cell wall constituents, xylose, p-coumaric and ferulic acid and lower (P<.05) IVDMD values for stems and leaf sheaths than leaf blades. Legume showed higher (P<.05) values for cell wall constituents and xylose for stems, compared to petioles and leaflets. At advanced maturity, scanning electron microscopy (SEM) showed increased lignification and decreased tissue digestion for leaf sheaths and stems, compared to leaf blades. Lignification was higher in millet leaf sheaths than barley leaf sheaths. Within berseem plant parts, petioles showed better digestion than leaflets and stems. The contents of ADF, cellulose and lignin were increased (P<.05) and hemicellulose was decreased (P<.05) in alkaline H₂O₂-treated straws, compared to untreated, NH₃- and urea-treated straw. Total phenolic acids were decreased (P<.05) in treated, compared to untreated straw. In vitro DM digestibility was increased (P<.05) for all chemical treatments, with larger (P<.05) increase for NH₃ treatment than alkaline H₂O₂ treatment. / Ph. D.

Forage may undergo extensive proteolysis during fermentation. The objectives of this study were to determine if treatment of forage with heat can reduce proteolysis during subsequent fermentation. In Experiment 1, direct-cut barley and alfalfa were either microwaved or steamed then ensiled in laboratory silos as were untreated and wilted forage. Silages of microwaved or steamed forage showed marked increase in NDIN and recovery of hot water insoluble N; however, alfalfa silages also had high pH and butyric acid. In Experiment 2, steaming was compared to formic acid and anhydrous ammonia treatments for their ability to prevent proteolysis in alfalfa silages. Steamed and ensiled alfalfa also was evaluated with addition of microbial inoculant or formic acid. Silage of steamed alfalfa had greater NDIN and recovery of precipitable N than controls, formic acid, or ammonia treated silage. There was no difference in precipitable N between formic acid and ammonia treatments. Silage of steam treatment had lower pH than wilted or direct-cut controls, and additives to steamed forage favored a more homolactic fermentation. Additives to steamed forage also increased aerobic stability of the silage. Steamed silage had less aerobic stability than direct-cut silage. Rumen degradability of silage CP and OM from both experiments were evaluated. In Experiment 1, CP degradability of microwaved or steamed silages was 8 to 26% less than unheated silages, but all had similar undegraded CP after incubation for 72 h. In Experiment 2, wilting, steam, formic acid and ammonia treatments had similar, but decreased CP degradability when compared to direct-cut silage. Longer duration heat in Experiment 1 resulted in greater silage protein preservation, and greater decrease in rumen degradability of CP than Experiment 2. / Master of Science

Master of Science

Cool-season perennial grass growth is suppressed during hot, dry summers. This "summer slump" reduces the availability of grazable forage. Tall-growing perennial warm-season grasses that produce 65 to 75% of their yield in midsummer may provide needed herbage during this period of reduced cool-season forage production. However, establishment of perennial warm-season species is slow and inconsistent when compared to cool-season species. Before these warm-season species can be relied on for summer forage production, a successful establishment methodology must be developed. A study was conducted to evaluate the influence of atrazine [2-chloro·4(ethylarnino)-s-triazine] and carbofuran on establishment of switchgrass (Panicum virgatum L.) and Caucasian bluestem [Boyhtiochloa caucasica (Trin.) C. E. Hubbard]. Treatments of carbofuran at 0 and 1.1 atrazine/ha placed in the row with the seed and of atrazine broadcast at 0, 1.1, and 2.2 kg/ha were imposed in all possible combinations. Another study investigated the influence of limestone, P, and carbofuran on the establishment of switchgrass. Treatments included carbofuran at 0 and 1.1 kg/ha, limestone at 0 and 4.48 Mg/ha, and P at 0 and 22 kg/ha in all possible combinations. Seedling growth rate, leaf appearance rate, plant height, and leaf elongation rate (LER) of seedlings were recorded. Seedling weight and populations were determined at the sixth leaf stage of development. Yields of forage and botanical compositions were also measured in the establishment year. Establishment was further evaluated with yield measurements the year after seeding. Carbofuran application increased first year yield, seedling weight, population, leaf appearance rate, and seedling growth rate. Atrazine reduced seedling population, weight, leaf appearance rate, LER, and yield. Carbofuran partially moderated atrazine influence. The 2.2 kg rate of atrazine tended to injure the switchgrass more than the Caucasian bluestem. In the study investigating limestone and P, carbofuran increased yield, seedling weight, seedling population, LER, seedling growth rate, and leaf appearance rate. The greatest yield, leaf appearance rate, and LER occurred with applications ofP and carbofuran. Even though initial soil pH was 5.1, limestone broadcast prior to planting did not influence seedling measurements and yields in either year. These plantings were made during 1985 and 1986, which were the driest summers in recent years. In spite of the moisture stress, acceptable stands of perennial warm·season grasses were established in both experiments in both years. Including 1.1 kg granular carbofuran/ha in the row, and broadcast application of 1.1 kg atrazine/ha at planting will improve establishment of perennial warm·season grasses. Where the P levels in the soil are low, a broadcast application of 22 kg P/ha improves chances for successful establishment. / Ph. D.

Soil water deficits greatly affect forage production. To evaluate the effects of soil moisture stress on forage production, a budgeting model was developed. The soil water budgeting model uses the initial soil water content which can be assumed or calculated. Stress was calculated as a difference between potential evapotranspiration and actual evapotranspiration at a level of - 5 bar. A radiation method was used to calculate the potential evapotranspiration and the soil water budgeting model was used to calculate the actual evapotranspiration. The Soil Conservation Service method was applied to calculate runoff and effective rainfall was calculated by subtraction of runoff from original rainfall and used in the model for calculation of actual evapotranspiration. Calculated stress was correlated to the yield and stepwise multiple regression were used to produce prediction equations. Observed soil water data and yield for calibration and validation of the models were obtained from Santa Rita Forest and Range Experimental Range in southeastern Arizona.

Diet selection and its variation due to difference in forages nutritive value are central processes in plant-herbivore interactions. An incorporating of these parameters may allow predicting diet selection patterns which are a basic underpin for sustainable vegetation management and profitable animal production. To achieve these issues many studies were done two of which were run to study the browse-browser interactions in a sub-humid subtropical savannah, a herd of goats was used as a model browser in natural pasture. Other studies evaluated the nutritive value of five plant species which were the most selected by goats. The objectives of this study were to (i) determine the seasonal patterns of diet selection of goats on woody species and their nutritive value and (ii) to predict the diet selection. The secondary objectivrs were to (i) investigate how plant characteristics such as plant morphology (spinescence, and broad vs. fine leaves), phenology (evergreen vs. deciduous species) and plant chemistry (nitrogen, neutral detergent fibre, acid detergent fibre, acid detergent lignin, condensed tannin, cellulose and hemicellulose) are relate to the diet selection patterns and to (ii) evaluate the nutritive value of the most plant species selected by goats during the different seasons. Two experiments were conducted at Owen Sitole College of Agriculture, KwaZulu-Natal, to determine diet selection of goats grazing/browsing in Zululand Thornveld. The first experiment was done in the early wet season (November 2007) and late wet season (March/April 2008) while the second experiment was conducted in the dry season (June/July 2008), early wet season (November/December 2008) and late wet season (February/March 2009). The relative abundance of browse species in the veld was determined and used to estimate the selection index. In the first part, diet selection was estimated using (i) direct observation of animals (account bouts) by observing every one minute two goats while they were foraging with others for 3 hours in the morning and 1.5 hours in the afternoon on alternate days for a total of six days and (ii) an indirect plant-based method by observing at regular intervals 40 marked branches on ten plants of each browse species every two days for a total of six days. The browse species observed were: Gymnosporia senegalensis, Acacia nilotica, Acacia karroo (Acacia natalitia), Scutia myrtina and Dichrostachys cinerea. In both seasons, the three most selected species according to the plant-based observations were S. myrtina, A. karroo and D. cinerea. Consistently, A. nilotica experienced moderate defoliation and G. senegalensis the least. However, on the basis of the selection index, the species followed the order: A. nilotica > D. cinerea > A. karroo > S. myrtina > G. senegalensis in the early wet season and A. nilotica > S. myrtina > D. cinerea > A. karroo > G. senegalensis in the late wet season. Both methods did not rank species in the same order. The selection index was negatively (P<0.05) correlated to neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL). In the second part, observations were taken on feeding time of two goats, randomly selected per day for 7-8 days. Observations were made during active foraging periods for 2 hrs in the morning and 1.5 hrs in the afternoon. The duration of each feeding bout and the species of woody plant from which bites were cropped at each feeding station were recorded. Season and plant species affected diet selection and preference. The five main species selected (utilized) by goats in decreasing order were S. myrtina, A. nilotica, D. cinerea, Acacia natalitia and Chromolaena odorata. Scutia myrtina was the most preferred (highest utilisation relative to availability) in the dry season while D. cinerea comprised the greatest proportion in the early and late wet seasons. Scutia myrtina was most preferred in the dry and early wet seasons while A. nilotica was most preferred in the late wet season. Spinescent species were generally selected more than non-spinescent species in all seasons, while fine-leaf and deciduous species were selected more than broad-leaf and evergreen ones in the wet seasons. However, preference for broad-leaf and evergreen species increased in the early wet season. Although plant chemistry varied across seasons, it did not explain the preference of goats for various plant species in this study. Instead, effects of chemistry were species- specific. The nutritive value of the five main species selected by goats was evaluated by chemical composition, in vitro gas production, in vitro degradability and in sacco degradability. Two experiments were conducted for the in vitro studies, the first experiment was to test the effect of season and species, while the second experiment tested the biological effect of tannins using polyethylene glycol 4000 (PEG). The PEG treatment was applied to samples of the early and late wet seasons only. The parameters were maximum gas production (GP), degradation rate (C), lag time (lt), maximum rate of GP at the point of inflection (μ), half time to the maximum gas volume(T1/2), gas produced from fermentation of soluble and slowly degradable fractions (A and B, respectively), their degradation rates (c1 and c2, respectively), apparent (ApDeg) and true degradability (TrDeg), microbial yield (MY), partitioning factor (PF), degradation efficiency factor (DEF) and short chain fatty acids (SCFA). There were wide variations among seasons and species in crude protein (CP), NDF, ADF and condensed tannins. Season and species affected kinetics of gas production, GP, TrDeg, MY, PF and SCFA. Chromolaena odorata had the highest CP (185.8-226.4 g kgˉ¹), GP (87.3-104.1 ml gˉ¹ DM), gas produce from soluble (47.6-50.9 ml gˉ¹ DM) and insoluble (39.8-50.9 ml gˉ¹ DM) fractions during the three seasons compared to other browse species. The TrDeg ranged from 634 to 856 g kgˉ¹ DM. The total SCFA varied between seasons and among species. The addition of PEG decreased TrDeg and PF, and increased GP and total SCFA. The GP, its degradation rate (C) and gas from the soluble fraction were positively correlated to CP without and with PEG. Gas from the soluble fraction was negatively correlated to NDF, ADL and CT; and GP to CT without PEG. In the in sacco study, the parameters of dry matter (DM) and nitrogen (N) degradability were soluble (a) and slowly (b) degradable degradability, the degradation rate (c), potential degradable (PD), effective degradability (ED) and lag time (lt). Season affected PD of DM degradability and ED of both DM and CP. Browse species and its interaction with season affected all parameters except b fraction of CP and interaction did not affected PD of CP. Chromolaena odorata had the highest estimated parameters of degradation during the three seasons compared to other browse species. Based on PD and ED, the plant species followed this decreasing order: C. odorata, A. nilotica, A. natalitia, S. myrtina and D. cinerea. All parameters were positively correlated to CP except the a and b fractions of DM and CP, respectively, and lt of both DM and CP. All parameters were negatively correlated to NDF, ADF and ADL except the b fraction and rate of degradation. Condensed tannins (CT) were negatively correlated with all parameters except the b fraction and PD of DM and CP, and lt of DM degradation. Cellulose was negatively correlated with a of DM and lt of CP degradation. The broad objective of this study was to assess whether plant characteristics, in sacco degradability, in vitro gas production, digestibility or chemical composition (NDF, ADF, ADL, CT and CP) could predict the selection of browse species. The parameters were selection index, plant characteristics (spinescence, or leaves phenology), chemical composition, in vitro gas production, in vitro degradability and in sacco degradability parameters. Most of these parameters were poor for predicting selection by goats of browse species. Spinescence (spn), leaves phenology (phen), NDF, CP and CT accounted for 86% of the variation in selection index (y) = -5.91 - 0.01CT - 0.002NDF + 0.02CP + 6.18spn + 2.43phen; (R2=0.86; n=20; RMSE=0.406; P<0.001; for phen, 1 = evergreen, 0 = deciduous; for spn, 1 = spinescent, 0 = spineless). It was concluded that in vitro gas production, in vitro degradability and in sacco degradability were poor predictors of selection index of browse species used by goats. Spinescence, leaf phenology, condensed tannins, CP and NDF were predictors of diet selection index and suggested that these plant species have potential to be used as feed supplements. Chromolaena odorata has the highest potential as feed protein source in goats. The addition of PEG (tannin binding agent) emphasizes that the inhibitory effect of tannins on rumen microbes was great in tannin-rich feeds. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

Thesis (Ph.D. Agriculture (Plant Production)) -- University of Limpopo, 2022 / Livestock has evolved to serve as the foundation and backbone of human well-being, and it is an important component of South Africa's agricultural sector. The small stock such as sheep (Ovis aries) in Limpopo province has remained a significant and multifunctional livelihood strategy for the majority of the rural and resource-poor people. Factors such as population growth, urbanization, rising per capita income and changes in consumer tastes and preferences are all contributing to gradual increases in livestock product consumption and demand. According to the 2019 Abstract of Agricultural Statistics, South Africa is an importer of sheep and sheep products. If the sheep production industry in the province could pursue this opportunity and realize its full production potential then increased production could stimulate economic growth and development, particularly from the communal and smallholder sector. Objective one of the study seeks to describe the demographic and socio-economic characteristics of communal and smallholder sheep farmers, identify sheep feeding practices and describe the constraints that hinder the sustainable productive growth of communal and smallholder sheep systems. Data were collected from one hundred and twenty (120) sheep farmers using a structured questionnaire across three agro-ecological zones of Limpopo province. Results revealed that overall, the majority of sheep farmers were males (78%) and farmers were above 60 years old (48%). Mean sheep flock size differed significantly between communal (24.74) and smallholder (62.36) farmers. Indigenous crossbreeds were the dominant breed kept by communal (86%) and smallholder (77%) farmers. The majority of communal and smallholder farmers (90% and 96%, respectively) reared their sheep under an extensive system with rangelands as the main source of feed. As a result, they experience a critical feed gap during June and September, the mid-winter to early spring until the first rains. The findings of the study revealed that feed shortages and diseases were ranked as the first and second production constraints by sheep farmers in both the production systems. In rangeland-dependent feeding systems, insufficient feed to meet animal demands create a feed gap, which is a critical factor that limits sheep productivity and causes xxi land degradation through overgrazing. Improved forages have been widely advocated as a critical step toward resolving this challenge. However, the adoption and utilization of improved technologies such as on-farm forage legume production by these farmers have been very low, contributing to the province's low sheep productivity. An extension of objective one of this study used primary data which was collected from a sample of 120 sheep farmers to determine the factors that influence the adoption of on-farm forage legume production and the perceived barriers to adoption by communal and smallholder sheep farmers in the Limpopo province. A Probit regression model and Principal Component Analysis (PCA) were used to analyze the data. The study revealed that the adoption of on-farm forage production by communal and smallholder sheep farmers is influenced by several factors, including gender, farming experience, knowledge of forage legume production, source of income, membership in farmer associations, access to extension services and farm size. Farmer perceived barriers to adoption of on-farm forage legume production identified by this study were low institutional support, lack of resources, lack of knowledge, shortage of water and objectives of the farmer. It is therefore recommended that intensive and high-quality extension support in partnership with industry associations and stakeholders is required for communal and smallholder farmers to improve forage technology awareness, training and promote on-farm forage production to transform communal and smallholder sheep feeding practices. In the face of climate change, identifying forage species with a high potential to mitigate winter feed gap challenges under more variable climatic conditions is critical. Trifolium and Vicia species are forage legumes well known for producing high-quality forage, particularly protein, which is deficient in the majority of feed resources used for sheep feeding during the winter season. Climate change-induced stresses from rising temperatures, which these winter annual forage legumes are likely to face, necessitate agronomic and breeding approaches to improve their adaptability. Lack of knowledge on how these climate change mitigation approaches influence the productivity of winter annual forage legumes in the Pietersburg Plateau of Limpopo province prompted objective two of this study. A three-year field experiment laid in a split-split plot design with four replications was conducted to measure the effects of planting date, cultivar and harvest stage on the physiological traits associated with biomass production, forage quality, nodulation activity and xxii nutritive value of annual clover and vetch species. The results showed that the planting date and harvest stage had a significant effect on leaf gaseous exchange and biomass production. A non-significant effect of planting date on nutritive value was observed. Intercellular CO2 concentration, transpiration rate, stomatal conductance, instantaneous water use efficiency and intrinsic water use efficiency in cultivars increased with delayed planting, while a decrease in photosynthetic rate, shoot DM, root DM and nodule DM was observed. Overall among the cultivars, Resal, Alex, Elite, Laser and Dr Baumans showed more consistency in terms of leaf gaseous exchange, biomass production and quality traits under planting date 1 and varying harvest stages. Investment in the year-round fodder flow establishment with high-quality forages is important in supporting sustainable sheep production. Forage legume-grass rotation systems are important not only for green fodder production of high crude protein, mineral and vitamin content throughout the year but also for enhanced soil fertility to reduce the nitrogen (N) fertilizer requirements. Accurate estimates of forage yields on the farm are required for fodder flow planning to ensure the seasonal distribution of fodder throughout the year. Objective three of the study was a no-tillage, short-term rotation experiment conducted to determine the growth and nutritive value of forage sorghum, planted after the winter annual forage legumes in combination with nitrogen application and to validate the performance of the APSIM-grain sorghum crop model in simulating forage sorghum growth and biomass production under different N rates. The treatments were planting date (January and February) and N source from inorganic N fertilizer (0 kg N ha-1, 60 kg N ha-1, 120 kg N ha-1, 180 kg N ha-1) and forage legume N residues (Alex, Capello, Dr Baumans, Elite, Hanka, Laser, Linkarus, Opolska, Resal and Timok) arranged in a randomized complete block design with four replicates. The findings of this study showed a significant response of forage sorghum growth and nutritive value to planting date. Delayed planting reduced plant height (11%), stem diameter (18%), LAI (6.7%), chlorophyll content (18%), NDVI (2.5%), photosynthetic rate (38%) and biomass production (8%). Delayed planting further reduced crude protein, acid detergent fiber and N yield. Nitrogen source from inorganic N at 60 kg N ha-1, 120 kg N ha-1, 180 kg N ha-1 and residual N from annual clover and vetch cultivars had a significant effect on morphological, physiological, yield and nutritive value parameters of forage sorghum. xxiii Generally, legume N residue effects on all the studied parameters of forage sorghum were similar to the inorganic N fertilizer of 60 kg N ha-1. However, the effects differed widely according to the species and cultivar of the legume. Resal, Laser, Elite Capello and Dr Baumans N residue consistently showed greater effects than other legume residues. They consistently outperformed inorganic 60 kg N ha-1 on the most measured parameters. The results confirm that annual clover-forage sorghum and vetch-forage sorghum rotation have huge potential to reduce the cost and negative environmental effects associated with inorganic N use in forage prediction systems. Regarding the evaluation of the potential of the APSIM grain legume model to simulate forage legume DM and plant height, in general, the model performed well and accurately in predicting the shoot dry matter accumulation and plant height under 0 kg N ha-1, 60 kg N ha-1 and 120 kg N ha-1. However, it underestimated both these parameters at 180 kg N ha-1 implying that the application of N up to 180 kg N ha-1 is not necessary. APSIM-grain module was able to accurately predict forage biomass production under N rates up to 120 kg N ha-1 and it is therefore considered reliable to support the N nutrition in the forage sorghum fodder production systems. / University of Limpopo, research office under the UCDP program and National Research Foundation-Thuthuka

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