A sound breeding objective is the basis for genetic improvement in overall economic merit of animals. Breeding objectives for Holstein and Jersey dairy cattle breeds in South Africa were developed in the current study, using a systematic approach. First, a logical framework with a profit focus was utilised to develop plausible selection goals for the pasture-based and concentrate-fed dairy production systems in South Africa, leading to an exhaustive list of objective traits influencing these goals and subsequently their possible selection criteria. Next, economic values were calculated for those objective traits for which there was adequate bio-economic data, viz.: milk volume, fat yield, protein yield, live weight, longevity, calving interval and somatic cell score. A bioeconomic model, simulating typical South African pasture-based and concentrate-fed herds, was used to calculate economic values by determining changes in profit arising from an independent unit increase in each trait. Alternative payment systems of four major milk buyers in South Africa were used. Relative economic values, standardised to the value of protein, were used to compare the relative importance of traits across breeds, production systems and payment systems. Protein yield, fat yield and longevity consistently had positive economic values and the converse was true for body weight and calving interval. Economic value for volume was positive or negative, depending on whether the payment system paid for it or did not. Economic values were reasonably robust to fluctuations in the cost of feed and price of beef; with the exception of fat, whose value became negative beyond the feed price of ZAR3.50. Protein was, overall, the most important trait, although volume, live weight, longevity and somatic cell score were more important in some situations. Calving interval was the least important trait, its value ranging from 4 to 22% compared to that of protein, probably because the model used underestimated its value. Sire rankings on aggregate EBVs based on these economic values did not differ much across breeds, production systems and payment systems, most rank correlations falling in the range 0.70-0.99. A single breeding objective may therefore be used for both the Holstein and Jersey breeds, across the different production and payment systems. The basis for multiple-trait selection in the major cattle breeds in South Africa has thus been developed. Considerable work, however, needs to be done to enhance this breeding objective as well as facilitate its wide adoption by industry.

Wag-ân-Bietjie Private Nature Reserve is situated ±30 km north of Bloemfontein in the summer rainfall area. The northern part is 437 ha in size and represents a transition between grassland and riparian vegetation. Vegetation types present are grassland, open thickets, dense thicket, drainage lines of the Modder River, a wetland and disturbed area. Phenology (seasonal leaf carriage) of plants formed the basis of this study. Percentage leaves in each phenophase (Budding-, Immature-, Mature-, Yellow- and Dry leaves) was noted fortnightly for specific marked trees and shrubs representing each vegetation type. The deciduous nature of woody species influenced quality and quantity of browse available for herbivores. Consequently the nitrogen concentration in faeces (Nf) of four game species was determined to indicate their nutritional status through the different seasons. The rise and fall of Nf values corresponded to the seasonal increase and decrease of leaves (phenology pattern). Nf ranged during four years from 18 â 37 gN/kgDM for giraffe, 14 â 33 g/kg for kudu, 16 â 35 g/kg for eland and 17 â 28 g/kg for impala. Abovementioned minimum concentrations are close to, and in the case of kudu below known critical values where animals start to lose body condition. Nitrogen is the most limiting nutrient in the dry, cool season and is linked to protein percentage present in browse. Browse becomes a limited resource in the winter, therefore certain game species moved seasonally to different areas inside the private reserve in search of food. It was decided to supply feed in order to sustain animals and help them maintain body condition during the critical period that was established to be from July/August to middle October. The duration of feeding is important and it is recommended to start feeding from July at a low ration and then gradually increase feed towards the end of the critical period in correspondence with the declining browse and grass resources. Average monthly leaf carriage percentages were used to calculate browsing capacity per month in each vegetation type and in the study area as a whole. Browser units that could be sustained on browse resources within the 0 â 2 m stratum ranged from 1 â 6.7 BU between winter and summer due to the deciduousness of all woody plants present in the study area. This justifies in some way the provision of feed, or else the numbers of animals would need to be reduced to 1 BU which does not represent sustainable populations. Viable population numbers, economic value, diet and reproduction rates were used in determining the numbers of individual animals that can be stocked. Grazing capacity of the area differed according to annual rainfall and increased with higher rainfall. Consequently it needs to be recalculated annually. Habitat occupied by all 17 herbivore species was determined. Some species did not historically occur in the province. Most of them have adapted to the central Free State conditions over time, while others were introduced more recently. Inter-species competition for space and food resources proved to be high in the study area. A reduction in animal numbers has been recommended to limit competition. There is an ever increasing number of private game ranches in the province, >343 in August 2010, that will benefit from this research. Some general, operational guidelines have been presented that are applicable to the management of other game ranches in the province as well. When calculating individual animal numbers equivalent to carrying capacity values of other areas, the percentage grass and browse that herbivores include in their diet need to be adjusted to the specific area for accurate stocking densities.

Semen was collected from the indigenous Damara, Namaqua Afrikaner, Pedi and Zulu rams. Hundred and twenty eight (128) ejaculates were collected throughout the entire study, with semen being collected twice a week (every Monday and Tuesday) from each ram, using the electro-ejaculator. Ejaculates were collected in graduated test tubes, placed in a thermo flask at 37°C, and transported to the laboratory for evaluation within 1h interval. The raw or fresh undiluted semen was then microscopically evaluated for volume, concentration, pH and sperm motility. The sperm concentration was determined with the aid of a spectrophotometer (Spermacue®) and the semen pH using a pH meter (Microprocessor pH/mV/°C Meter Hanna HI 931401). A Computer Assisted Sperm Analysis (CASA) system was used to evaluate the different sperm motility characteristics. All data were analysed using the statistical GenStat® program. The analysis of variance (ANOVA) was used to test for significant differences between treatments. Characterization of the South African indigenous ram sperm viability (percentage live/dead) of the semen samples was determined, using an eosin/nigrosin stain (60μl eosin/nigrosin and 6μl semen), in a thin smear. All sperm cells were evaluated on the same day of semen collection with the aid of a fluorescent microscope (BX 51TF), using an oil immersion objective (X100 magnification). The live sperm fluoresced green, while the dead cells stained red. The live sperm cells were further categorized as morphologically normal or abnormal. The volume of the indigenous ram ejaculates ranged between 0.4 and 0.9mL. The sperm concentration recorded in this study ranged between 0.9 and 1.3x109 sperm/mL, which are much lower when compared to other studies. The semen pH recorded in this study ranged between 6.5 and 7.3 and the sperm abnormalities ranged between 5.2% and 8.2% â which is regarded as acceptable for fertilization. To test the effect of storage temperatures on the viability of the diluted ram semen stored for different periods of time, the same procedure of semen collection and semen evaluation was followed. After the initial semen evaluation, all semen samples were pooled and diluted equally in an egg yolk citrate extender in the ratio of 1:1(v/v). The pooled semen sample was then divided into two portions, one sample being stored at 5ºC, and the other at 15°C, following storage periods of 3, 6, 9, and 24h respectively. Sperm characteristics were then recorded for each interval of storage. In general the percentage total motile sperm recorded after a 24h period of storage at 15°C was higher (61.2%), compared to that at 3h (51.4%), 6h (50.1%) and 9h (50.6%). From the results of this study it was concluded that diluted ram semen can be successfully stored for 24h at 15°C, retaining sperm motility for the application of AI. When evaluating the effect of glycerol as a cryoprotectant, in the diluted ram semen stored at two temperatures for different periods of time, the same procedure for semen collection and evaluation was followed. After initial evaluation, all semen samples were pooled and diluted equally with an egg yolk citrate extender containing 14% glycerol in the ratio of 1:1 (v/v), resulting in a final glycerol concentration of 7%. The pooled semen sample was then divided into two portions, one sample being stored at 5ºC and the other at 15°C, for periods of 3, 6, 9, and 24h. Sperm characteristics were recorded at each interval of semen storage. Semen stored at 15°C recorded a 48.3% total motile sperm after 3h of storage, but this increased to 50.4% following 24h of storage. The percentage of total motile sperm remained relatively constant at 40% after 3h of storage and 40.8% after 24h in the semen stored at 5°C. The addition of glycerol as a cryoprotectant demonstrated a protective effect on the sperm motility characteristics of sperm stored at both 5°C and 15°C for up to 24h of storage. The effect of different glycerol inclusion levels in the diluent, on the indigenous ram semen characteristics following cryopreservation were evaluated. The same procedure for semen collection was followed and semen was subjected to the initial evaluation comprising sperm concentration, semen pH and sperm motility. After initial evaluation of the ejaculates, the semen samples were diluted with an egg yolk citrate extender (EYC) fraction A (without glycerol), in the ratio of 1:1 (v/v) and cooled over a period of 2h to 5°C. All ram ejaculates were pooled and then divided into 4 portions treatment (groups). The first group was diluted with EYC (fraction A), which served as a control and the other 3 groups with EYC (fraction B) contained 7, 10 or 14% glycerol (GLY) in the ratio of 2:1 (v/v), making final glycerol concentrations of 2.3, 3.3 or 4.7% respectively. The semen samples were equilibrated for 2h and then loaded into 0.25mL semen straws. The straws were frozen in liquid nitrogen (LN2) vapour, whereafter semen straws were plunged into the LN2 (-196°C). The semen straws were thawed 7 days later, in a water bath (37°C) for 30 seconds. The sperm characteristics (motility and velocity) were microscopically evaluated using the Sperm Class Analyzer® (CASA) system. A 10% glycerol inclusion rate recorded a higher percentage of total motile sperm (15.6%), compared to the 7% glycerol (12.8%) and 14% glycerol (8.5%) inclusion levels, although all these differences were not significant. This study demonstrated that an egg yolk- citrate extender containing 10% glycerol can be used to cryopreserve indigenous ram semen effectively, based on the sperm motility characteristics. The low sperm motility results recorded when semen was cryopreserved in an extender containing 14% glycerol also indicated a degree of toxicity of glycerol at high inclusion levels in the semen extender. Regarding the conventional slow cryopreservation (programmable freezer) of ram semen versus semen cryopreservation in liquid nitrogen vapour, the same procedure for semen collection and evaluation was followed. After the initial evaluation of the raw semen samples, all ejaculates were pooled and then diluted using an egg yolk - citrate extender (EYC) fraction A (without glycerol), in the ratio of 1:1(v/v) and cooled over a 2h period at 5°C. After equilibration, the pooled semen sample was further diluted with EYC fraction B, containing 14% glycerol, in a ratio of 2:1(v/v)resulting in a final glycerol concentration of 4.7%. The pooled semen sample was then further equilibrated and loaded into 0.25mL semen straws. Half of the straws were frozen in liquid nitrogen (LN2) vapour and then plunged into the LN2. The other half of the semen straws were frozen with the aid of a programmable freezer. After 7 days, the semen straws were thawed in a water bath at 37°C, for 30 seconds. The sperm characteristics (sperm motility and velocity) were microscopically evaluated using the CASA system. From the findings in this study, it can be concluded that a controlled rate of semen cooling gave superior sperm motility results (15.3±3.0%), compared to semen frozen in LN2 vapour (8.8±0.9%). It should be noted that programmable freezers are costly, when compared to the liquid nitrogen vapour technique. Due to the fact that sperm motility differences recorded were not significant, it is suggested that the freezing of semen on a small scale be done using the LN2 vapour technique, without any significant decrease in sperm motility or possible fertility.

Pedigree and performance data of a well-documented ostrich breeding resource flock was used to (1) investigate the flock structure, (2) estimate variance and (co)variance components for egg and day-old chick weight (individual traits), (3) estimate genetic and environmental parameters for egg and chick production, mean egg and day-old chick weights and hatchability within breeding seasons (hen traits) and (4) investigate early identification of superior animals using random regression models for repeated measures (longitudinal) data over years. The average level of pedigree completeness of 40 074 birds of a pair-breeding ostrich flock maintained from 1978 to 2005 at the Oudtshoorn Research Farm, South Africa was high (99.3%) in the first generation and the average level of inbreeding (F) was low at 0.51%. The estimated measures of variability were: effective genome equivalents = 47.3, effective number of founders = 59 and the effective number of ancestors = 58. The numbers of ancestors responsible for 100%, 50% and 20% of the variation in the reference population (birds with both parents known), were equal to 254, 21 and 6 respectively. The generation interval in years calculated as the average age of parents when their offspring which were kept for reproduction were born, amounted to 7.72 ± 4.79 years. The linear regressions of rate of inbreeding on year of hatch for the two distinct periods, 1995-2002 and 2003-2005, were 0.08% and -0.07 % per year respectively. The estimate of effective population size (Ne) computed via the increase in the individual rate of inbreeding was 112.7 animals. The results of this study indicated that the population under study was at an acceptable level of genetic variability. Pedigree and performance data for 71 147 individual egg records collected between 1991 to 2005 were used to estimate genetic parameters for egg weight (EWT), live day-old chick weight (CWT) and hatchability (H). Heritability estimates (±SE) were 0.12 ± 0.02, 0.14 ± 0.04 and 0.09 ± 0.04 for EWT, CWT and H. Corresponding estimates for maternal genetic effects were 0.27 ± 0.08, 0.38 ± 0.08 and 0.13 ± 0.02. The effects of common environment, permanent environment and breeding paddock were significant but relatively low for all traits. Egg weight and CWT were highly correlated at all levels, while H was mostly independent of the weight traits. These results indicated that genetic improvement in these traits would be feasible. Data involving monthly records of egg production (EP), chick production (CP), hatchability (H), mean egg weight (MEW) and mean day-old chick weight (MCW) were analysed as hen traits. Heritability estimates amounted to 0.04 ± 0.02 for EP, 0.05 ± 0.03 for CP, 0.44 ± 0.04 for MEW, 0.02 ± 0.02 for H and 0.67 ± 0.02 for MCW. Permanent environmental effects as a ratio of phenotypic variance (c2 pe) ranged from 0.08 ± 0.03 to 0.11 ± 0.02 for the first four traits (MCW did not exhibit a significant c2 pe effect). Monthly EP and CP were highly correlated at all levels, ranging from 0.74 for the temporary environmental correlation to unity for the genetic correlation. Hatchability was highly correlated with EP and CP at the genetic level (>0.94). Genetic correlations of EP and CP with MEW and MCW were variable and in some cases antagonistic. Genetic correlations of H with MEW and MCW were positive (0.52 and 0.47, respectively). Results indicate that selection for improved reproduction (reproductive output and product quality traits) is feasible. Selection for production is unlikely to be complicated by unfavourable correlations with H, MEW and MCW. Hen traits defined above were further analysed in single-trait mixed models with a random regression fitted as an intercept for the direct animal (a) and a quadratic polynomial with intercept for the permanent environmental (p) effect peculiar to each hen. Heritability (h2) estimates were moderate and remained relatively constant for EP and CP ranging from 0.13-0.14 and 0.07-0.08 respectively for 3- to 10-year old hens. Quality traits MEW and MCW had moderately high h2 estimates ranging from 0.49-0.61 and 0.37-0.45 respectively. Hatchability had h2 estimates ranging from 0.11-0.13 for the 10 hen-ages. Permanent environment variance ratio for EP, CP, MEW, MCW and H ranges were 0.28-0.42, 0.29-0.41, 0.17-0.33, 0.21-0.35 and 0.14-0.24 respectively. Selection of superior hens from three years onwards seems possible. Hens older than eleven years should be replaced with younger, genetically superior hens which would reduce the generation interval and improve EP and CP genetically, without adversely affecting MEW, MCW and H.

The length of productive life is of major economic importance in dairy cattle production. Simple breeding objectives such as selection for increased production in dairy cattle have led to a significant decline in fitness traits. A multi-purpose breeding objective that includes other traits such as length of productive life should be considered. Herd life reflects the ability of a cow to avoid being culled for low production, low fertility, or illness. Herd life can be used in breeding programs if genetic parameters are known. The objectives of the study were to: (1) estimate genetic parameters for functional herd life for the South African Jersey breed using a multiple trait linear model, (2) develop a prototype breeding value for functional herd life for the South African Jersey breed, (3) estimate genetic relationships between functional herd life and conformation traits in the South African Jersey breed and (4) assess inbreeding depression for functional herd life in the South African Jersey breed based on level and rate of inbreeding. A measure of herd life called functional herd life was considered in the current study. Functional herd life refers to herd life adjusted for milk production in the first lactation. In this study functional herd life was defined as survival in each of the first three lactations. Functional herd life was denoted by a 1 if a cow survived and 0 otherwise. Analyses to estimate genetic parameters for functional herd life were carried out as follows. Data and pedigree records on purebred Jersey cows that participated in National Milk Recording and Improvement Scheme were analyzed. Data before editing comprised test-day and lactation yields on milk, fat and protein yields from 252 629 Jersey cows born between 1968 and 2005. After editing, 181 269 cow records from 636 herds recorded over 16 years were available for analysis. Estimates of genetic parameters for herd life were obtained using REML procedures fitting a multiple-trait linear animal and sire models. Heritability estimates (0.02 to 0.03) from the two models were somewhat similar for all lactations. However, heritability estimates for lactations 2 and 3 were slightly higher with the sire model compared to the animal model. The genetic correlation between lactations 1 and 2 from both the sire and animal models was higher than that between lactations 2 and 3. Genetic correlations from the sire model ranged from 0.68 to 0.99 and corresponding estimates from the animal model ranged from 0.76 to 0.99. Genetic parameters obtained in the current study suggest that sufficient genetic variation exist for herd life to allow for genetic improvement and that early selection for functional herd life is feasible. The development of a prototype breeding value for functional herd life for the South African Jersey breed was carried out as follows. Test-day and lactation data on cows that participated in the National Dairy Cattle Improvement Scheme were considered. A multiple-trait linear animal model was used to estimate breeding values using Parameter ESTimation (PEST) software package. A complete (co)variance structure for the additive genetic and residual effects for the three traits were used. These (co)variances were estimated in the first objective. Reliabilities were approximated using the effective number of daughters. Estimated breeding values were scaled so that the average breeding value was a 100. Estimated breeding values for sires ranged from 79 to 114. The rate of genetic progress per year for the period 1985 to 2002 was statistically non-significant (b = 0.02±0.05 per year). The mean reliability was 33.43% and reflective of the low heritability of functional herd life. However, it should be noted that while direct selection for functional herd life could lead to genetic progress, this genetic response could be relatively slow due to the low heritability. The genetic relationship between conformation traits and functional herd life of the South African Jersey population was investigated. Data on conformation traits (n = 46 238) and functional herd life (n = 90 530) on registered South African Jersey cows calving between 1989 and 2008 were obtained from the Integrated Registration and Genetic Information System. Conformation traits were scored using a subjective linear scoring system ranging from 1 to 9, except for foot angle with a maximum score of 8. Conformation traits included stature, chest width, body depth, dairy strength, rump angle, thurl width, rear leg side view, foot angle, fore udder attachment, rear udder height, rear udder width, udder support, udder depth, front teat placement, rear teat placement and front teat length. Genetic correlations between conformation traits and functional herd life were estimated using a series of bivariate analyses. The highest correlations were estimated for udder traits. Significant moderate to high positive genetic correlations between most udder traits and functional herd life (0.23 to 0.63) were estimated. The most important udder traits related to functional herd life were fore udder attachment, rear udder height, and udder depth. Correlations between the majority of body structure and functional herd life were variable. Most of the body structure traits had a low to moderate negative correlation with functional herd life (-0.04 to -0.27). The structural body traits of rump angle and foot angle were estimated to have a moderate positive genetic correlation with functional herd life. The genetic relationships between functional herd life and conformation traits in the South African Jersey breed indicate that conformation traits could be used to enhance the accuracy of genetic evaluation for functional herd life. The effect of inbreeding depression on functional herd life in the South African Jersey population based on individual level and rate of inbreeding was investigated. A pedigree file of the South African Jersey breed (n = 912 638) was obtained from the Integrated Registration and Genetic Information System (INTERGIS). The data included registered, grade and imported animals. The percentages of animals in the pedigree file with two, one and zero parents unknown were 22%, 18% and 60%, respectively. The inbreeding coefficient for each animal (Fi) and the rate of individual inbreeding (ÎFi), as an alternative measure of inbreeding which is adjusted for the depth of known pedigree, were calculated. The effect of inbreeding on functional herd life in each of the first three lactations was estimated using a single trait sire model on data collected from 1985 to 2003. Three analyses for survival in each of the first three lactations were conducted. In the first analysis, in addition to fixed and random effects, an individual inbreeding coefficient (Fi) was fitted as a linear covariate. In the second analysis, the inbreeding coefficient was included as a discrete variable with the following classes of inbreeding: 0 < F ⤠3.125, 3.125 < F ⤠6.25, 6.25 < F ⤠12.5 and F > 12.5. In the third analysis, the individual rate of inbreeding (ÎFi) was included in the model as a linear covariate. The level of inbreeding in the SA Jersey population showed a gradual increase for the period 1985 to 1994, while the period 1995 to 2009 showed a rapid increase. The current mean level of inbreeding (for the year 2010) is 4.85% with a minimum and maximum of 0 and 31.34%, respectively. The rate of inbreeding showed a gradual increase from 0.36% to 0.43% between 1985 and 2003. The average rate of inbreeding is currently (for the year 2010) at 0.55%. There was a significant (P<0.05) unfavourable relationship between inbreeding and functional herd life in the first and second lactation. The effect of inbreeding was more pronounced in the second lactation for both measures of inbreeding. Based on the current level of inbreeding, the reduction in functional herd life in the first lactation can be estimated to be 0.68%. The corresponding estimate for the second lactation is 1.70%. These results indicate that the current level or rate of inbreeding has reached levels that are detrimental to functional herd life. Therefore, individual inbreeding coefficient should be considered when breeding decisions are made by the Jersey breeders in addition to genetic merit.

Small-scale livestock production systems are an inherent part of communal livestock farming in the Southern African region and require certain interventions and welldeveloped management systems to ensure long-term sustainability. To this end a better understanding of the biophysical and socio-economic features of communal farming communities can contribute to the planning and implementation of better focused agricultural development programmes in these areas. The present study presented a unique opportunity to study and compare two adjacent areas where mainly livestock farming has been practised for generations by, on the one hand, communal farmers who apply limited pasture management, and on the other, the Mara, which uses proven pasture management and rotational grazing, practices. This research presented an opportunity not only to compare livestock production systems but also to determine the impact of communal farming on plant composition and edible plant material production. The study elicited excitement and enthusiasm among local animal and pasture scientists, as well as social scientists, as the outcome of this study could impact directly on future small-scale livestock farming development. The objective of this study was twofold. The first objective was to evaluate the socioeconomic complexities of small-scale ruminant livestock production under communal farming conditions. To this end, fifty farmer households that share a communal grazing area were surveyed. Data analysis was performed using Statistical Package for Social Sciences (SPSS). Most pertinent results of this study are the following: female animals make up the largest proportion of a herd; the majority of farmers sustain their livelihood from off-farm activity and farm for status not for profit; and farmers farm mainly with the Nguni breed owing to its adaptability to the environment. Given the socio-economic scenario, the second objective was to investigate the way socio-economic conditions impact on the natural feed resource base. Twelve fistulated Bonsmara steers were used. Rumen fistulated steers were used to determine the dry matter disappearance and ammonia concentration using nylon bag technique and the Oesophageal fistulated steers were used to determine the chemical composition. Data were analysed with the SAS Statistical package (2002- 2003) and the results indicated that there was no significant difference measured between the two sites in terms of ingested dry matter (DM) disappearance from the rumen and chemical composition of ingested material and ammonia production in the rumen and vegetational measurements were all significantly different between the two sites. The study concludes that differences in the grazing material available in terms of the two systems are a result of the quantity of the dry material available and not the quality. Moreover, livestock farming on its own is declining and is unable to provide sufficient financial returns for the survival of households. Households are consequently compelled to become involved in off-farm activities in order to generate enough income to sustain their livelihoods.

The objective of this study was to infer direct and maternal additive effects and direct and maternal heterosis effects for growth, fitness and carcass traits in beef cattle using least squares means estimated from crossbreeding studies by Els (1988) and De Bruyn (1991). The dataset was formed by recording each least squares mean along with the breed composition, maternal breed composition and direct and maternal heterozygosity. Each trait was analyzed using a single trait fixed effect model which included source of data as a fixed effect and breed composition and heterozygosity as covariates. Breed solutions were relative to the Afrikaner breed. Heterosis results were also obtained for crosses not made. Among breed groups, crossbred calves showed higher average values for almost all traits than purebred calves. The average direct heterosis contributions to weight traits in ten two-breed genotypes, which involved the Afrikaner (A) as dam line and the Simmentaler (S), Brahman (B), Charolais (C) and Herefords (H) as sire lines were 3.5, 7.9, 8.2 and 4.3% for birth weight (BW), weaning weight (WW), 19-month heifer weight (HW) and cow weight at partus (CW) respectively. Similarly, the average maternal heterosis effects for the weight traits in the four A crossbred dam genotypes (BA, CA, HA and SA) were 1.5, 8.8, 4.9 and 2.9% for the growth traits respectively. Due to additive and non-additive effects of C and B purebreds on BW these sires should only be bred to mature cows. For a weaner calf production system, the C genotype had the highest direct breed effect of +64.1 kg or 34.8% for WW. The combined additive effect of the C dam line was however, exceeded by the S dam line (+38.4 kg or +20.9% versus +50.0 kg or +27.2%). The total combined heterosis effect of the CA dam line was +32.5 kg versus the +19.2 kg effect of the SA dam line. The average expected phenotypic values for WW for the SA dam line was thus larger than the CA dam line (233.3 versus 230.7 kg). The maternal heterosis effect of the HA dam was the second largest (+22.1 kg) of the four two-breed combinations of A. The B genotype used in the study did not have a true superior ability to increase the expected WW in the A breed. The direct and maternal heterosis effects of the breed were - 0.5 kg or -0.3% and +22.1 kg or 12.0% respectively. The H breed had the lowest direct breed effects of +24.7 kg or +13.4% on WW out of the four purebred sire lines that were bred to the A dam line and a small negative direct heterosis effect (-0.5 kg or -0.3%). Furthermore, the maternal additive effect was negative (-29.6 kg or -16.1%). The maternal heterosis effect however, was positive (+22.1 kg or +12.0%). The A sire line had the lowest expected phenotypic values for HW and CW (323.9 and 434.3 kg respectively), indicating that these heifers would probably reach puberty earlier and that these cows would be smaller compared to genotypes from S, B, C and H genotypes. On average two-breed genotypes had 48.9 and 40.6 kg expected increase in HW and CW respectively, and an additional 21.9 kg and 20.4 kg for the two traits respectively in threebreed genotypes (backcrossing excluded). The H sire line did not have a true ability to increase expected CW in the A breed. The C genotypes had the lowest average individual heterosis effect of -17.6 kg (-4.0%) on CW of all four sire lines which were involved in the ten different two-breed combinations of the study. However, the CA dam line was responsible for the highest maternal heterosis effect of +54.8 kg or +12.6% out of the four crossbred A dam lines. By utilizing genotypic differences the opportunity for high productivity and profitability can be maximized, especially through cumulative traits such as the calf/cow weight ratio. All crossbred genotypes, except the BA genotype, increased the calf/cow weight ratio. Results indicated that the A breed should constitute 75% of the genetic make up of B and C crossbred genotypes and 25% of H and S crossbred genotypes to maximize calf/cow weight ratios. The HSA, HBA and BSA, genotypes had the largest calf/cow weight ratios of 0.509, 0.506 and 0.495 respectively, mainly due to the large direct heterosis effects of +22.7 (+12.3%), +28.0 (+15.2%) and +36.7 kg (+19.9%) of the HS, HB and BS genotypes for WW respectively. This gives opportunity for direct paternal heterosis to be used in crossbreeding systems with purebred A dams. Alternatively, since the B breed had a true ability to increase the expected BW in the A dam, it is suggested that a specific or rotational crossbreeding system which involves S and A dams that are mated with either H or B (only on mature dams) sires for the production of weaner calves under sweet veld conditions, be used. The data were also used to estimate the additive and non-additive effects for fitness traits in the two- and three-breed crosses. The average direct heterosis contributions were +14.9, +109.1, -162.7, +21.0 and 15.4% respectively for CR, MB, MP, WP and WR for ten two breed genotypes. Similarly, the average maternal heterosis effects in four A crossbred dam genotypes were 0.0, -87.5, +97.7, -1.9 and -7.4% for the fitness traits respectively. The HA genotype had the highest expected F of 83.1% in two-breed genotypes. The direct heterosis contributions in the HA genotype were +21.7, -2.3, -5.8, +28.3 and +30.1% percentage units respectively and the maternal contributions were -8.2, -2.4, +1.6, -6.4 and -11.6 for the traits respectively. The expected phenotypic values for improved traits in the HA and AHA genotypes were 94.9 versus 96.4% for CR, 92.2 versus 96.3% for WP and 83.1 versus 86.8% for WR (MB and MW remained unchanged). Crossbreeding the A dam line with the B sire line resulted in improved expected WR: 66.7 versus 80.2% in BA. Backcrossing the BA genotype decreased WR. This could mainly be explained by the increased expected MW; 3.3% in the A versus 6.0 and 15.6% in the BA and ABA genotypes respectively and the lower expected WR of 72.8 and 74.5% in the ABA and BBA genotypes respectively. While the SA genotype had an improved expected WR of 78.4% compared to the A genotype (66.7%), the WR in the ASA progeny was the lowest of all genotypes (60.4%). The low expected WR of the SA genotype could be explained by the increased expected MB of 5.3 versus 2.2% and MW 5.7 versus 3.3% of the A breed. The poor performance of the SSA genotype could be ascribed to an increase in MB and MW which was 7.3 and 4.3% respectively. The ACA, AHA and BHA genotypes had the highest expected WR of 86.9, 86.8 and 83.0% respectively. A specific crossbreeding combined with a terminal sire system is suggested to increase fertility in the A breed. Rotational systems will not have the same advantage since backcrossing the CA or HA dams to their respective sire lines would decrease the WR to 64.2 and 73.1% respectively. Alternatively, CA, HA or CH crossbred sires could be used on purebred A dams in a specific crossbreeding system. These genotypes had the largest direct heterosis effect on WR of all ten two-breed genotypes (36.5, 30.1 and 30.8% percentage units respectively). In a specific two-breed system the HA genotype would maximize WR. Although the average direct heterosis effects were unfavourable (-2.1 and -13.0 g/day respectively) for feedlot gain (FG) and carcass gain CG), feed conversion ratio (FCR) was -2.3% (a desirable effect). The average maternal heterosis effects for the feedlot traits were undesirable in the four A crossbred dam genotypes (-1.3, -7.4, and +0.9% respectively) for all the traits. Although these average heterosis effects suggest that feedlot traits do not benefit from crossbreeding, selected genotypes offer opportunity to increase feedlot production efficiency. As purebred the A compared less favourably in feedlot traits with Bos taurus breeds. However, it was evident that the A dam in two-breed crossbreeding could outperform the purebred S and Bos taurus crossbred dam lines in most of the these traits. The average direct heterosis contributions to feedlot traits in ten two-breed genotypes for the S, B, C and H as sire lines were -2.1, -13.0 (undesirable) and -2.3% (desirable) for feedlot gain (FG), carcass gain (CG) and feed conversion rate (FCR) respectively. Similarly, the average maternal heterosis effects for the feedlot traits in the four A crossbred dam genotypes were -1.3, -7.4, and +0.9% (undesirable) for FG, CG and FCR respectively. However, the A dam could be utilized in two-way crossbreeding systems with a terminal sire such as the C. The CCA genotype had expected average FG, CG and FCR of 1376.8 g/day, 781.2 g/day and 6.0 kg/kg respectively. Alternatively, the paternal heterosis contributions from BA, HA, SA, BH, BS and HS sire lines were also favourable. The aforementioned genotypes could thus be used as sire lines on purebred A dams to improve feedlot traits. It should however be noted that the data did not take cogniance of the genetic trends in the traits and the effects on heterosis parameters in any of the breeds since the conduction of the crossbreeding experiments. Heterosis units are therefore not directly applicable.

THE POPULATION DYNAMICS OF ACACIA NILOTICA SUBSP. KRAUSSIANA IN NORTHERN KWAZULU-NATAL By JANET MARY TAYLOR Supervisor: Prof. G.N. Smit Department of Animal, Wildlife and Grassland Sciences University of the Free State MAGISTER SCIENTIAE Globally the thickening of woody plants is on the increase, creating many issues within these areas of encroachment. Within KwaZulu-Natal, one such species, Acacia nilotica, is part of this phenomenon. A. nilotica is currently creating an issue over a large portion of the province. An increase in tree density lowers the amount of available grazing which reduces the stocking numbers of grazing herbivores. A better understanding of the drivers, phenology and growth of this plant will assist in providing information to control the establishment and increase of tree density of this plant species. Focussing on a smaller area in KwaZulu-Natal, uMkhuze Game Reserve, in the northern region of the province, was chosen as the study area. This reserve was chosen as the study area as it is currently experiencing an increase in A. nilotica density as well as having good historical management records and imagery. The Maxent species distribution model was used to determine the extent and potential distribution of A. nilotica within KwaZulu-Natal. For this study A. nilotica presence data, collected from surveys done by the KZN Department of Agriculture and Environmental Affairs, along with environmental variable data (rainfall, altitude, geology and mean minimum temperature) were used to model the potential distribution of the plant. Results indicate that a large portion of the province has the potential for A. nilotica occurrence. This distribution map has created an awareness of this plant for land users within the province. It also illustrates that a possible increase in temperature and rainfall from global change may provide more areas within KwaZulu-Natal with the potential to inhabit A. nilotica. Within uMkhuze Game Reserve, the plant communities were surveyed, described, classified and mapped. From this the approximate areas and tree density of A. nilotica were estimated. Seventy sites were surveyed with the 5 measurements for the BECVOL procedure. Site data were run through the BECVOL 3-model and grouped into one of the 12 identified vegetation communities. Of these 12 communities, A. nilotica were found to be in 8 of them. This is a possible 73% of the park that has the potential to contain A. nilotica. Tree density for these vegetation classes ranges from an estimated 950 to almost 7 000 plants/ha, while tree volume ranged from 5 200 to approximately 15 900 ETTE/ha. These results provide good baseline data for the vegetation of the reserve and illustrate the variety that an area can have. Different vegetation communities require different management practices and therefore this vegetation map illustrates these rough boundaries. An assessment of the monthly plant phenology was undertaken to gain insight into the inter-seasonal changes of A. nilotica. Browsing herbivores rely on the available browse of deciduous plants like A. nilotica, where forage becomes limited during the winter season. This understanding also provides insight into the biology of the plant for easier control. Thirty-two trees were marked and monthly leaf, flower and seedpod phenology was recorded on a qualitative scoring basis. Four branches within each of these trees were marked and repeat monthly growth measurements were taken. The leaf phenology had a seasonal pattern that seemed to be linked largely to temperature and photoperiod. New leaves budded in late September to October and leaves started to senesce by June. A. nilotica produces summer (October to February) flowers and seeds followed thereafter (March to June). The major plant growth was also found to be in the warm, high rainfall season. A distinct link was noted between tree stem circumference (age) and tree branch growth. These phenological seasons are useful in guiding management decisions for both the stocking of game in the reserve and for the control of A. nilotica. Finally, all the knowledge gained from this study and other literature sources were pulled together to develop a conceptual understanding on how best to aid in the control of this plant species. This conceptual understanding provides detailed information into the different life stages of the plant and a âtool kitâ of suggestions into the management and control of this plant. Through this research, an integrated management plan using a combination of holistic management measures is regarded as the recommended form of control for this plant species.

The successful and effective management of conservation areas can only be achieved with access to sound environmental data. The Doornkloof Nature Reserve (DNR) in the Northern Cape Province, was in need of such data which was essential for the development of proper management policies. The objectives of this study were to identify, describe and measure the most important environmental characteristics of the reserve, which will be used as the baseline data for the refinement of management policies. This included the identification and description of the plant communities; the demarcation of management units; determining the botanical composition and the veld condition of each management unit; quantifying the density; species composition and above-ground biomass of woody plants; calculating the carrying capacity (graze and browse); determining the seasonal habitat selection, group sizes and social structures of the ungulate species of DNR and developing a suitability index to assists management decisions. The Braun-Blanquet method was used to identify the plant communities of DNR. A total of 204 reléves were sampled and upon analysis six major plant communities and 14 sub-communities were identified. The plant communities and sub-communities were grouped into seven management units. Due to the heterogeneous landscape of the reserve, the vegetation of DNR was relatively diverse, consisting of grasslands, shrublands and riverine communities. A step point-method and the Ecological Index Method were used to determine the species composition and veld condition of the herbaceous layer of each management unit respectively. The grazing capacity of each management unit was determined by two separate methods. The floristic diversity differed substantially between topographical features, rather than between management units. The mountainous areas were in excellent veld condition and had a high grazing capacity, while the more degraded lower regions were in poor to good condition and had substantially lower grazing capacities. Rainfall and grazing played an important role in the study area and indicated that the vegetation of Doornkloof Nature Reserve displays both equilibrial and non-equilibrial trends. A quantitative description technique, (BECVOL3-model), was used to quantify the plant densities, species composition and above ground biomass of the woody plants of each management unit. Browsing capacities were calculated for different browsing heights (1.5m, 2m and 5m). Both plant densities and browsing capacities differed substantially between the various units. Plant densities varied from 40 plants/ha to 1 120 plants/ha, while browsing capacity varied from 4 ha/Bu to 157 ha/BU at a browsing height of 2 m. The browsing capacity did not decline substantially from the wet to the dry season, predominantly due to the abundance of evergreen species. The habitat selection of seven ungulate species was investigated by recording sightings of game species within each habitat unit. A goodness-of-fit test was applied to the data to determine if habitat selection of game species differed from being random. Habitat selection was found not to be random. Confidence intervals were calculated by means of the Bonferroni method to determine the habitat preference of each game species. The results indicated that species had clear habitat preferences and that some species showed seasonal changes in habitat selection. Species such as buffalo and mountain reedbuck were found to be habitat specialists, while species such as eland were more habitat generalist. The results indicated that eland, kudu and warthog were thriving in the environment, while the gemsbok and mountain reedbuck population were not adapting as well as expected. An alternative approach to conventional habitat suitability models was attempted in this study. The proposed suitability model proved to be relatively accurate in predicting both the habitat selection of game species and the quality of the habitats of DNR. The potential use of similar suitability models holds potential as a tool in assisting with objective management decisions