Recent studies show polymorphisms in the leptin gene significantly impact milk production in dairy cattle. If the leptin gene were to have a similar impact on beef cattle, calf weaning weights would be expected to increase from the increased milk production in the cows. Since weaning weight is a key component of profitability in a cow-calf operation, leptin genotyping may prove to have an economic impact in breeding cattle. However, no research has been done to link the economic impact of increased milk production to breeding cattle. Using 595 observations from genotyped cows spanning 11 years (1995-2005), calf weaning weight by genotype is estimated as a function of calf and dam characteristics and environmental effects. A MIXED procedure, utilizing data from 89 culled cows, is used to determine statistical differences in average cull age by genotype. A simulation model calculates mean annualized equivalent return by genotype and breed using the regression coefficients and residuals and 16 years of price data. results show that at least one T-allele in breeding cows increases calf weaning weight, average cull age, and annualized equivalent return compared to cows with homozygous C-alleles. These results indicate that there may be future premiums and discounts for breeding cattle based on genotype. Seedstock producers could potentially begin to segregate herds based upon genotype so that they could sell genotypic registered products. Cow-calf producers may also benefit from this knowledge by increasing the amount of TT genotype breeding cattle in their herd to maximize profits.

Relationships between the futures price, cash price, and U.S. Feeder Steer Price in the final eight weeks of trading on the feeder cattle futures contract were analyzed. Models were developed to examine continued problems with basis variability in the feeder cattle futures contract. The results of these models indicated that the change from physical delivery to cash settlement and the use of the U.S. Feeder Steer Price as a settlement index for the contract did not improve problems associated with basis variability. / Master of Science

M.S.

This study attempts to identify factors responsible for determining differences in the productivity of cattle managed by communal and private livestock farmers in the southern region of Botswana during 1999/2000. It is hypothesised that herd productivity and investment in southern Botswana are higher on private ranches than on open access communal grazing land. This study is important because livestock, especially cattle, contribute significantly to the livelihood of farmers in Botswana. Cattle are a major source of meat, milk and draught power, and provide a store of wealth that protects against inflation and which can easily be converted into cash. Cattle production is also an important source of employment in the rural economy of Botswana. Furthermore, the export of beef is a major source of foreign exchange earnings, and cattle account for 80 percent of agriculture's contribution to Botswana's gross domestic product. A stratified random sample survey of communal and private livestock farmers was conducted in the southern region of Botswana from August 1999 to May 2000 with the assistance of four enumerators. The sample survey data were used to compute descriptive statistics and to estimate the parameters of a block recursive regression model. The model postulated relationships between agricultural credit, investment in fixed improvement, investment in operating inputs and herd productivity. Some of the equations are estimated with Ordinary Least Squares (OLS) and some with Two-Stage Least Squares (2SLS) to account for likely correlation between endogenous explanatory variables and the error term. Descriptive statistics show that levels of investment and herd productivity are higher on private farms than on open-access communal grazing. Private farmers are also better educated, more liquid, and have larger herd sizes, but do not differ from their communal counterparts in terms of age, gender, race or household size. The regression results show that (a) respondents with secure tenure and larger herds use more agricultural credit than those who rely on open access communal grazing land to raise cattle; (b) secure land tenure, higher levels of liquidity and use of long-term credit promote investment in fixed improvements to land; (c) liquidity from short-term credit and wage remittances supports expenditure on operating inputs; and (d) herd productivity increases with greater investment in fixed improvement and operating inputs. Herd productivity is therefore positively (but indirectly) influenced by secure land tenure. It can therefore be inferred that government should (a) uphold private property rights to land where they already exists; (b) privatise open access grazing to individual owner operators where this is politically, socially, and economically feasible; and (c) where privatisation to individuals is not feasible, government should encourage users to convert the grazing into common property by subsidising the costs of defining user groups and the boundaries of their resources, and enforcing rules limiting individual use of common property. This first-step in a gradual shift towards more secure tenure should be followed by the conversion of user groups to non-user groups organized along the lines of investor-owned firms where members exchange use rights for benefit and voting rights in a joint venture managed by an expert. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

The economic necessity of a better production strategy on sourveld promoted this study. Production of marketable two-tooth steers in the summer season and overwintering of all cattle without excessive feed costs were motivating factors. The problems of economic beef production were identified as resulting from the seasonal flow of forage quality from sourveld grass production. Season long rests, early burning and non-selective grazing of nutritious grass were identified as essential elements of a new utilization strategy. A 'forage reserve', built into the system to cater for fluctuations in grass production due to varied climatic conditions, is used as an indicator of the seasonal stocking rate. This provides a barometer in relation to the economic and ecological carrying capacity of the property. Research was conducted on the winter utilization of rested veld and its effects on grass species composition and vigour in the following season. It was found that the winter grazing of the rested veld did not affect (P>0.05) the subsequent production in the three seasons of this study on 'Stratherne' in the Dundee district, KwaZulu-Natal South Africa (30°17'E 28°17'S). The grass species composition of four transects was recorded in 1994, prior to the implementation of the grazing system under test. The same transects were recorded again in 2002 to determine the effect of the change in utilization on grass species composition. It was found that a more productive state was developing in response to the strategy implemented in this study. The general trend has been for sites to move from a Hyparrhenia hirta dominated state to a more productive one associated with species such as Themeda triandra. Summer mass gains of steers (147 kg and 143 kg over the two summers) have improved over the previous systems applied (average 119 kg), as a result of the more nutritious grazing. A greater proportion reached market readiness as two-year old to two and half year olds (97%) on veld, which is far superior to the 38% quoted from research using similar Bonsmara type steers from 'conventional' systems. Monitoring and flexibility are important in the application of the strategy to conditions in Africa. The principles of adaptive management (monitoring, recording, constant learning and adaptation) will build a data base to ensure long-term success of the strategy. A change of focus in grazing strategy from needs of animals to the needs of plants is strongly advocated. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.

Arid and semi-arid regions have increasingly become the subject of much research and debate by scientists. By their very nature, these regions characteristically exhibit extremes which complicate the implementation of effective management strategies that ensure sustainable productivity and economic output. Namibia is one such region where low and highly variable rainfall conditions and fluctuating productivity pose a challenge to managers of commercial livestock enterprises, / who seek to optimise economic benefits while controlling the negative effect on herd production and income of unpredictable and unfavourable climatic events. Various management approaches are proposed as a means of exploiting periods of abundant productivity and so optimising income from herd production, while controlling for the effects of drought conditions. To analyse the effects of these various offtake strategies, a rainfall-driven plant-herbivore simulation model is used. The model comprises components simul~tihg vegetation and herbivore dynamics. The vegetation component incorporates soil moisture and nutrient allocation to plant parts. The herbivore dynamics sub-model comprises age and sex classes, population dynamics and animal energy requirements which govern accumulated fat reserves. The model is adapted to account for climatic and vegetation attributes specific to Namibia. An economic component including a seasonal monthly price structure is developed, and a dynamic feedback governing management decisions is incorporated. The much debated issue of whether to maintain a constant stocking rate or to track climatic variation by employing a variable stocking level is investigated, with the performance of management strategies incorporating these approaches ranked according to various factors, including annual returns, associated risk and annual stock mortality. The economic consequences of the timing of offtake are investigated, with the simulation of management strategies that implement destocking in the face of anticipated drought conditions. A dynamic projection of expected income allows the impact of forecasting potential economic gains on decision-making to be analysed. Results indicate that the performance of management strategies is not as dependent on climatic and seasonal price variability as was originally expected, with the application of a constant stocking level proving to be the most favourable strategy in terms of economic gain and variability of income. Tracking climatic variation by adapting stocking levels does not provide the improvement in economic returns from a livestock production system that was anticipated, although this approach is successful in effecting a significant reduction in annual stock mortality. Further results show the sensitivity of income to the long-term average stocking level characterising the management strategies investigated, as well as to the elasticity of the underlying price structure. The results of this study indicate that the implementation of management strategies designed to track climatic variation does not offer significant economic advantages over the application of a constant stocking approach. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2001.

Climatic and market uncertainty present major challenges to livestock producers in arid and semi-arid environments. Range managers require detailed information on biological and economic components of the system in order to formulate stocking strategies which maximise short-term financial risk and minimise long-term ecological risk. Computer-based simulation models may provide useful tools to assist in this decision process. This thesis outlines the development of a bioeconomic stocking model for the semi-arid savanna of Natal. Grazing trials were established at two sites (Llanwarne and Dordrecht) on Llanwarne Estates in the Magudu area of the semi-arid savanna or Lowveld of Natal. The Lowveld comprises a herbaceous layer dominated by Themeda triandra, Panicum maximum and P. coloratum and a woody layer characterised by Acacia species. The sites differed initially in range composition. Llanwarne was dominated by Themeda triandra, Panicum maximum and P. coloratum, while Dordrecht with a history of heavy stocking was dominated by Urochloa mosambicensis, Sporobolus nitens and S. iocladus. Three treatments were stocked with Brahman-cross cattle at each site to initially represent 'light'(0.17 LSU ha-'), 'intermediate' (0.23 LSU ha-') and 'heavy' (0.30 LSU ha-') stocking. Data collected at three-week intervals over seven seasons (November 1986 to June 1993 or 120 measuring periods) provided the basis for the development of a bioeconomic stocking model (LOWBEEF - LOWveid BioEconomic Efficiency Forecasting) which comprised two biological sub-models (GRASS and BEEF), based on step-wise multiple linear regression models, and an integrated economic component (ECON) . The GRASS model predicted the amount of residual herbage at the end of summer (kg ha-') and the forage deficit period (days) over which forage supplementation would be required to maintain animal mass. Residual herbage mass at the end of summer (kg ha-') was significantly related (P < 0.01) to cumulative summer grazing days (LSU gd ha-'), rainfall (mm) (measured 1 July to 30 June) and range condition (indexed as the sum of the proportions of T. triandra, P. maximum and P. coloratum). The forage deficit period (days) over which herbage mass declined below a grazing cut-off of 1695 kg ha-' was significantly related (P < 0.01) to residual herbage mass at the end of summer. The BEEF model predicted the livemass gain over summer (kg ha¯¹) which was significantly related (P< 0.01) to rainfall (mm) stocking rate (LSU ha¯¹) but interestingly not to condition. The economic component (ECON) reflected the difference between gross income (R ha¯¹) and total costs, which were based on fixed and variable cost structures (using 1993 Rands), including demand-related winter costs, to reflect net returns to land management (R ha¯¹). A conceptual model of range dynamics based on three discrete states, was to developed to summarise the effects of rainfall and stocking rate in semi-arid savanna. State 1, characterised by iocladus and S. nitens, was associated with heavy stocking. Movement towards State 2, characterised by T. triandra and P. maximum, was associated with periods of above-average rainfall. Drought conditions, which comprised a major system disturbance led to stability at State 3, dominated by U. mosambicensis. Post-drought recovery was influenced by predrought composition and stocking levels where tuft numbers, basal cover and seedbank were significantly reduced by increased stocking within a sward dominated by species of low stature such as Aristida congesta subsp Urochloa mosambicensis, Sporobolus nitens, Sporobolus iocladus and Tragus racemosa. It was suggested that extensive soil loss may lead to stabilisation across an irreversible threshold at a forth state characterised by shallow species such as Tragus racemosa Aristida congesta subsp. congesta. Sensitivity of optimum economic stocking rate net return to price and interest rate fluctuations, and wage and feed cost increases were examined for various rainfall and range condition scenarios. Net return and optimum economic stocking rate increased as rainfall and range condition increased through the effect of increased residual herbage mass at the end summer, decreased forage deficit periods and reduced supplementary feed costs. Net return was highly responsive to changes beef price where an increase in beef price led to an increase in optimum economic stocking rate and net return. The effect of reduced prices may be compounded by dry where supply-driven decreases in price may occur. This suggested that for dry seasons the optimum stocking rate was the lightest within the range of economic stocking rates. Although an increase in interest rates would increase variable costs and lead to reduced returns, the influence of interest rates on enterprises will vary in relation to farm debt loads. Increased labour costs would result in a corresponding decline in net return although optimum economic stocking rate would remain unaffected. Increased supplementary feed cost had little influence on net return relative to the effect of demand-driven increases in feed costs as rainfall decreased . The distribution of net returns for stocking strategies of 0.20, 0.30 and 0.40 LSU ha¯¹ and climate-dependent stocking (where stocking levels were varied in relation to rainfall and hence forage availability) and range condition scores of 10, 50, 80 and a dynamic range model were examined for a 60 year rainfall sequence (1931- 1991). While a range score of 10 would see residual herbage mass decline to below a grazing cut-off of 1695 kg ha¯¹ before the end of summer, a range score of 80 suggested that, irrespective of stocking strategy within the range investigated, herbage would not become limiting. This suggested that irrespective of stocking strategy a range score of 10, established across an irreversible soil loss threshold, would reflect accumulated losses over the 60 year period. In contrast, a range score of 80 would lead to positive accumulated returns. A dynamic range model (where range composition was related to previous seasons rainfall) and a climate-dependent stocking strategy, suggested that herbage would not become limiting by the end of summer and forage deficit periods would be restricted to an average of 88 days per year. Such an approach would yield a higher accumulated cash surplus than fixed stocking strategies. Incorporation of stochastic rainfall effects allowed the development of cumulative probability distributions based on 800-year simulations to evaluate the risk associated with various stocking strategies. Range condition played a major role in determining the risk of financial loss where decreased range condition was associated with enhanced risk. An increase in stocking rate resulted in increased variability in returns. Although the risk of forage deficits and financial losses may be reduced with lighter stocking, this may be at the cost of reduced returns during wetter seasons. Increased stocking may increase the probability of higher returns during wetter seasons although this may at the cost of increased risk of forage deficits and highly negative returns during dry seasons. Importantly, ecological risk may increase as stocking is increased. A flexible or climate-dependent strategy, where stock numbers are adjusted according to previous seasons rainfall, combine financial benefits of each approach and reduce financial risk. Although errors may carry hig h ecological costs where, for example, the effect of an above-average rainfall season would be to increase stock numbers into a subsequent dry season, the probability of incurring such error was low. Current livestock production systems in the semi-arid savanna of Natal based on breeding stock may not be appropriate in a highly variable environment where low rainfall may require extended periods of supplementary feeding or force the sale of breeding stock. A change in emphasis from current systems to a mixed breeding system, where the level of breeding stock would be set at the optimum economic stocking rate for drier seasons, may decrease both financial and ecological risk. Growing stock may either be retained or purchased during wetter seasons to reach the optimum economic stocking rate for such seasons. Although growing stock may display a greater tolerance to restricted intake (during dry seasons) than would breeding stock, additional growing may be rapidly sold in response to declining rainfall with no influence on the breeding system. Integration of wildlife into current cattle systems may be an important means of reducing financial risk associated with variable rainfall and profitability and ecological risk associated with woody plant encroachment. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1994.

Dairy farming is one of the most important agricultural industries in South Africa, and thus improving the performance of dairy cows, with respect to economically important dairy traits, would be beneficial. Selection of dairy cows has traditionally been phenotypic, but new molecular techniques have made it possible to evaluate phenotypic dairy traits at the DNA level, providing the possibility of more accurate selection. The economically important dairy traits, milk production and reproductive performance, are quantitative traits, and are therefore controlled by many genes and the environment. A number of genes have been identified that have been shown to influence economically important dairy traits, including the lep gene. This gene encodes the hormone leptin, which has been proven to regulate feed intake, energy balance, fertility and immune function. A polymorphism has been identified in the lep gene, which may be associated with economically important dairy traits. This study on a South African Jersey herd investigated the possible association of the polymorphism, RFLP-Kpn 21, with milk production and reproductive performance. The lactation records of fifty Jersey cows that completed their first lactation between 1997 and 2004 were collected, and these cows were genotyped for the RFLP-Kpn 21 polymorphism, located at exon 2 of the lep gene. This involved the extraction of DNA from venous blood, using a salting out technique. The extracted DNA was amplified using PCR primers; the reverse primer included a purposeful mismatch. The role of the purposeful mismatch was to create a recognition site for a restriction enzyme (Kpn 21), thus allowing the alleles of the polymorphism to be identified through a restriction digestion protocol. Two alleles were identified, the C- and the Tallele. The genotype of each cow was identified using PAGE. The significance of the genotype effects on the milk production traits and the reproductive performance traits were estimated using the F-statistic provided by a GLM Univariate analysis. In conclusion, no significant effect of the RFLP-Kpn 21 polymorphism was found for milk yield, butterfat and protein percentage, ICP and SPC (p > 0.05), but a possible association with lactose percentage was suggested by the statistical analysis (p < 0.05). Further investigation of South African Jersey cows will be necessary in order for conclusive results to be obtained. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

In KwaZulu-Natal the production of beef in summer from veld is a common enterprise. Many techniques are available to optimise the productivity of this enterprise, from improving the quality of the grazing resource (planted pastures) to improving the diet of animals using nutritional supplements. To gain an insight into the production potential and financial returns possible from such improvements a trial was established at the Ukulinga Research Farm during two consecutive summer growing seasons (1997-1998 and 1998-1999). The aim was to determine the optimum beef production system for the area from both veld and kikuyu pastures. To evaluate the benefits of supplying supplementary nutrition, four alternate feed supplements, namely: 1) a Standard commercially available molasses-based protein/mineral/energy supplement; 2) a Brewers grain based protein/mineral/energy supplement, and two supplements consisting of the Brewers grain ration with either; 3) Avoparcin (an additive that improves dietary energy) or 4) Bentonite (an additive that increases the bypass of protein) were compared. As stocking rate has been shown to influence the quality of the diet consumed, the kikuyu pasture was grazed at both the recommended (1.92 LSD ha¯¹) and half the recommended stocking rate for the region. In addition, a commercial hormonal implant was applied to half of the cattle in each treatment. Grazing was monitored using the falling plate disc meter to measure pasture bulk density and laboratory analyses of herbage grab samples for digestibility and crude protein percentage. Cattle were weighed on a weekly basis and their condition was scored prior to slaughter. All enterprise costs and returns were recorded to facilitate financial analyses of the five treatments. Low rainfall and high midsummer temperatures had a detrimental effect on the productivity of the grazing and hence it was difficult to optimise production in either season. In the first season, a midsummer drought decreased the quality and quantity of both veld and kikuyu, limiting mass gain during the latter part of the season. A delay in the onset of rain at the start of the second season limited the available grazing season to 121 days as opposed to 154 days, though fodder production during the season was not limited. Trends in herbage production (quality and quantity) from veld showed moderate quality (Crude protein 7.02%; digestibility 50.2%) with an average available herbage of 1670 kg DM ha¯¹. As anticipated, kikuyu had higher quality (Crude protein 10.84%; digestibility 53.5%) and available herbage (2730 kg DM ha¯¹). These results were similar to regional benchmarks. The variable rainfall highlighted both the drought tolerance of veld and the minimum water requirements of kikuyu pastures. Lighter stocking rates tended to reduce the negative impact of moisture stress on Kikuyu pastures. The best method of producing beef (averaged over two seasons) was from heavily stocked Kikuyu pastures using the Standard supplement (1107.63 kg livemass ha¯¹). Cattle grazing veld and utilising the Avoparcin supplement produced beef at a rate of 95.96 kg ha¯¹. In comparison, the unsupplemented cattle grazing Kikuyu produced 834.87 kg ha¯¹, whilst veld grazing produced 64.43 kg ha¯¹. Hormonal implants significantly (P≤0.05) improved beef production from all sources of grazing. A lack of rain limited grazing time, causing all the cattle to be marketed whilst too lean - this negatively affected live mass gain and, hence, net financial. Although improved biological production is desirable, it is important to ensure that these gains are financially sustainable. Within the trial environment, implanted cattle fed the Standard supplement and grazing Kikuyu pastures at a high stocking rate provided the highest average gross margin of R 859.59 ha¯¹. Changing to this production system from unsupplemented veld improved expected profit by R 632.58 ha¯¹ (averaged over both seasons). Further financial analyses indicated that beef purchase price had the greatest influence on the added profit from switching from the control treatment. From a scientific standpoint these data are conclusive but it is important to remember that consumer pressure and concerns can often limit the introduction of production improvements. Such is the case with both hormonal implants and antibiotic feed additives (Avoparcin) although considering the impact of such limitations is speculative and beyond the scope of this trial. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.

No description available.