A study to evaluate the effect of feeding a high energy diet on the productive and reproductive characteristics of young bulls was carried out at two different locations in the Free State Province. Two trials were conducted with the aim of evaluating the effect of level of dietary energy and age of the bulls on their productive performance and reproductive characteristics. In the first trial, two levels of energy were fed to two groups of young (343 ± days) Bonsmara bulls. The high energy group HE (n=36) bulls were Phase-C performance tested in an official performance testing center and received a high energy diet for 112 days (28 days adaptation and 84 days testing). The medium energy group ME (n=18) bulls were phase-D performance tested and received a medium-energy diet for 140 days (28 days adaptation and 112 days testing). At the end of both performance testing periods, the productive performances and reproductive characteristics of the two groups were compared. The productive parameters compared included final live body weight (FLW), average daily gain (ADG), average daily gain per day of age (ADA) and body condition score (BCS). The reproductive parameters compared between groups included scrotal circumference (SC), semen volume (Vol) and concentration (SConO), mass movement (MV), linear motility (LM), percentage live sperm (LS), as well as percentage of total abnormalities: major (MD) and minor (MinD). The results of this trial indicated that in general, bulls from the HE group showed a significant (p<0.01) higher FLW, BCS, ADG and ADA, but a significant (p<0.01) lower volume and concentration of the ejaculate, lower mass movement and linear motility, lower percentage of live sperm and higher percentage of major defects and significantly (p<0.05) higher percentage of minor defects than the bulls from the ME group. In the second trial, 36 young Bonsmara bulls were divided into two groups according to their age at the arrival at an official Phase-C performance testing center. Older bulls (OB) (n=19) and younger bulls (YB) (n=17) all received a high energy diet for 112 days (28 days adaptation and 84 days testing). At the end of the Phase-C test the productive performances and reproductive characteristics of the two groups were compared. The animals from both groups that did not pass the Phase-C test, either due to poor performance or not meeting the breed standards, were slaughtered at an official abattoir and their scrotums and carcass characteristics were also compared. The productive parameters compared between the two groups included final live body weight (FLW), average daily gain (ADG), average daily gain per day of age (ADA), body condition score (BCS), feed conversion ratio (FCR), carcass weight both warm (CWW) and cold (CWC), as well as dressing percentage (CDP) and fat grade (CFG). The reproductive parameters compared between the two groups included scrotal circumference (SC), total scrotal weight (TSW), scrotal fat (SF), scrotal skin weight (SSW), paired testes weight (PTW), scrotal skin thickness (SST), total testes circumference (TTC), total testicle volume (TTV), weight of epididimis / spermatic cord (WESC), volume of epididymis / spermatic cord (VESC) and the percentage of bulls with depressed spermatogenesis (PBDS), semen concentration (SConO), mass movement (MV), linear motility (LM), percentage live sperm (LS), percentage of total abnormalities: major (MD) and minor(MinD) as well as the percentage of bulls with depressed spermatogenesis (PBDS). The results of this trial indicated that in general, the younger bulls showed a significant (p<0.05) higher ADG, but a significant (p<0.05) lower ADA than the older bulls. Regarding the reproductive organs compared, the younger bulls showed a significantly (p<0.01) higher total scrotal weight, scrotal fat and scrotal skin weight and thickness. No significant differences were observed on the testicular parameters measured between the two groups. In addition, both weight (WECS) and volume (VECS) of the epididymis / spermatic cord were significantly (P<0.05) higher in the older bulls. In general, the younger group showed poorer semen characteristics. A significantly (p<0.01) lower sperm concentration and linear movement and a significantly (p<0.05) higher percentage of major defects were recorded on the younger bulls, when compared to the older bulls. About half of the bulls in each group showed clear signs of depressed spermatogenesis in their seminiferous tubules, during the histological examination of testicular tissue. The results of this study indicates that high energy diets are beneficial for the productive performance of young bulls (growth rate, BCS and carcass characteristics), but have a detrimental effect on the reproductive characteristics of young bulls. The effect of high energy diets on both the productive and reproductive performances of young beef bulls are more pronounced at a younger age. High energy diets resulted in heavier scrotums in the younger bulls when compared to the older bulls, as a direct result of a higher fat deposition in this region without any relevant effect on testicular size. No intra-testicular fat deposition was observed. The scrotal fat observed in high energy fed young bulls accumulated mainly in the neck of the scrotum, although subcutaneously. These fat deposits may impair testicular thermoregulation and negatively affect the spermatogenesis in the seminiferous tubules, reducing both sperm quantity and quality. Further studies on the effect of high energy diets on bull fertility (as well as on rams and buck) are recommended, to evaluate the extension and duration of its detrimental effects on subsequent fertility.

Thesis (M.Sc. (Animal and Wildlife Science)) -- University of Pretoria, 2005. / Includes bibliographical references (leaves 99-102).

Thesis (M.Sc.(Agric.)) -- University of Pretoria, 2008. / Abstract in English. Includes bibliographical references.

Biological mechanisms that potentially contribute to residual feed intake (RFI) have not been fully understood in the grazing animal. The objective of this study was to determine the differences of RFI measured in confinement (RFIc) or grazing (RFIg) on animal performance. Animals were previously classified in confinement as high RFI (HRFIc), or low RFI (LRFIc) and subsequently under grazing as high (HRFIg) or low (LRFIg). Effects of forage quantity on dry matter intake (DMI), and biological mechanisms that contribute to variations in RFI were investigated using ultrasound, carcass traits and bacterial populations. Bulls were allotted to replicate bermudagrass pastures at low (LSTK) or high (HSTK) stocking intensities and heifers grazed one Ryegrass pasture. Ruminal microbial content was collected and profiled using bacterial tag-encoded FLX amplicon pyrosequencing technique. In 2009, bulls were harvested directly off the pasture and ultrasound and carcass measurements were determined. Data were analyzed using PROC GLIMMIX of SAS. Linear regressions were obtained using PROC REG to estimate RFI. In 2009, there was a difference for LRFIc bulls in F:G (P=0.032), and HRFIg bulls on LSTK had an interaction for ADG (P=0.043). HRFIg bulls had greater intakes regardless of STK (P=0.003). In 2010, HRFIc bulls remained heavier throughout with the greatest DMI (P=0.0095). There were no differences for any traits for 2010 RFIg bulls. At a LSTK, HRFIg bulls tended (P>0.05) to have a lighter gastrointestinal tract (GIT) weight (P=0.093) while liver weight (P=0.072) tended to be heavier for all bulls. The small intestine was heavier for LRFIg bulls (P=0.09) on a HSTK. There was an interaction for microbial bacteria identified in the rumen in 2009 on hemicellulolytic (P=0.048), starch (P=0.025), and pectinolytic (P=0.057) degrading bacteria. HRFIg bulls at a LSTK had a greater percentage for amylolytic and pectinolytic degrading bacteria (P=0.008 and P=0.051, respectively) in the large intestine. There were no interactions for any substrates in 2010. DMI (P<0.0001) was greater each year for HRFIc heifers and was greater (P=0.0168, P=<0.0001, P=<0.0001) each year respectively for LRFIg heifers. No differences were found for initial BW, final BW, MetBW, and ADG in the RFIc or RFIg classes. HRFIg bulls with the greatest forage availability consumed more and had heavier GIT, but it is still unclear how the microbial fauna affected the efficiency among RFI phenotyped bulls.

The study compares the biological performance of progenies of the Afrikaner x Western Sanga crossbred (small frame) and the Bonsmara (medium frame) cattle on the following traits: calving and growth rates as well as mortalities. The study was conducted in the Sourish Mixed Bushveld of the North West province. The objective was to identify a lowcare cattle breed, which can withstand unfavourable conditions under which most farmers in the North West Province operate. The results of this study indicated that, under good management, the Bonsmara cattle have higher growth rates compared to the Sanga cattle. There were statistical differences with regards to birth, pre-wean and wean masses, (P< 0.0001). Sanga cattle however were able to maintain higher calving rates under all varying conditions (Bonsmara 77% average and Sanga 84% average). The Sanga, due to its lower nutritional requirements, on average requires 15% less of the surface area required by the Bonsmara. Sanga cattle also returned better yields in terms of kilogram weaned calf per LSU and per hectare. With regard to herd mortalities, there was no significant difference (P = 0.03329).

The aim of the present study was to determine if the breeding potential of 25-month old, extensively kept, Bonsmara beef bulls can be predicted from production data, spermatozoal characteristics and/or blood hormone concentrations at that age. A further objective of the study was to determine if any of the above mentioned criteria could be associated with the libido of these bulls. Forty-one Bonsmara bulls were included in an on-farm performance test (Phase D1 growth test) for a period of 180 days. At an average age of 24.7 months, blood sampling took place (before and after GnRH treatment) and the bulls were subjected to a libido test, after which further blood samples were collected. Blood sample were analysed for cortisol and testosterone concentrations. The bulls were also subjected to an Overall Breeding Soundness Evaluation. This procedure involves an evaluation of the physical genitalia of the bulls, a measurement of scrotal circumference and semen evaluation. For purposes of statistical analyses the bulls were categorised into independent breeding potential categories according to the scores they obtained for the measured reproductive traits. The categories included scrotal circumference, spermatozoal morphology and motility and the overall breeding soundness category. A statistical analysis of the data was done by using the general linear models (GLM) procedure of the Statistical Analyses System (SAS version 8.2 BMDP). The production and growth measurements of the Bonsmara bulls did not differ between any of the high and low fertility categories and can not be used to predict the breeding potential of young bulls. The correlation between pre-weaning growth rate and the percentage morphologically normal spermatozoa was positive (r = 0.33; P<0.1), suggesting that relatively high growth rates before weaning may have a positive effect on potential fertility under normal extensive feeding conditions. By contrast, numeric differences in growth after weaning suggest that a high growth rate after weaning may have a negative effect on potential fertility. The results showed that the overall breeding soundness categories tended to be influenced by the pre-weaning growth rate (r = 0.24; P>0.1) and body lengths (r = 0.18; P>0.1) of bulls. Sampling time had a statistically significant effect on blood cortisol and testosterone concentrations for all of the breeding potential categories. Testosterone concentration increased significantly (P<0.001) after GnRH treatment. High plasma cortisol concentrations were associated with low plasma testosterone concentrations. High testosterone concentrations were associated with less spermatozoal morphological defects (r = - 0.21; P>0.1). The testosterone concentrations before GnRH treatment was higher for bulls with exceptional fertility (P<0.05), while testosterone concentration after GnRH treatment tended to be higher (P<0.1) for the bulls with acceptable fertility. This observation may be explained by the negative feedback system that operates between LH and testosterone secretion. The percentage spermatozoal defects were influenced to a greater extent by morphological abnormalities leading to reduced motility of the sperm than by any other abnormalities. From the results it seems that the semen morphology category is a better indicator of semen quality than the SC and semen motility categories. Overall breeding soundness classifications of bulls were largely influenced by spermatozoal motility (P<0.001) and to a lesser extend by spermatozoal morphology and SC. None of the reproductive and production measurements showed a correlation with libido scores, implying that optimal bull reproductive evaluation should include the assessment of both breeding soundness and libido. / Dissertation (MSc(Agric))--University of Pretoria, 2009. / Animal and Wildlife Sciences / unrestricted

Several Breeders within the Bonsmara cattle breeders’ association have been selecting for polledness otherwise known as the trait for the genetic absence of horns. There are less costs associated with polled animals, as they require less management input than horned animals. International stud breeders are willing to pay a premium for Bonsmara stud animals certified as homozygous polled, and Bonsmara breeders therefore requested a study for the identification of polled status, using DNA markers. Several microsatellite markers were tested in a linkage analysis on a number of Bonsmara families originating from three polled herds. All of the markers tested in the final Twopoint linkage analysis showed significant linkage with the polled trait. This indicates that the current model proposed for the gene action of polledness is applicable to the Bonsmara breed. Furthermore, by using the Transmission disequilibrium test (TDT), an allele of one of these microsatellites was found to be strongly associated with the polled trait. Due to an inherent lack of phase-known, three-generation families, tracing this allele through the test pedigrees to determine polled status was not possible. These results indicate that phase-known family data must be available so that microsatellite markers linked to the Polled trait can be traced visually to differentiate homozygote polled animals from heterozygote polled animals. Microsatellite markers are a tool that can add additional information in the conclusive determination of Polled status, but cannot as yet be used in isolation to test for polledness in the South African Bonsmara breed. Copyright / Dissertation (MSc)--University of Pretoria, 2005. / Animal and Wildlife Sciences / unrestricted

The production environment is known to have a large influence on extensively managed beef cows. A better understanding of the relationship between the beef cow and her environment should be useful in the pursuit of improving beef cow efficiency. The influence of the production environment on the efficiency of extensively managed Bonsmara cows was investigated through a series of research objectives. It was found that VEGMAP’s bioregion classification system can be used to describe the South African beef production regions. The environmental characteristics with the potential to influence beef cow efficiency were identified as temperature, rainfall, cation exchange capacity, soil pH, soil organic carbon, soil P and grazing capacity. A dataset was created that contains the historical cow production records for every Bonsmara breeder. GIS tools were then used to link the cow production records with the production region in which the farm is located, as well as the environmental characteristics for that specific location. The combined dataset was then statistically analysed to investigate the research objectives. The influence of the geographic location, production region and breeder on Bonsmara production traits was investigated by cluster analysis and ANOVA. Results from ANOVA indicate that production region has a statistically significant (p < 0.05) influence on production traits. The influence of the breeders on the same production traits was, however, statistically much larger (p < 0.0001) than production region. Bonsmara production traits are therefore influenced to a greater extent by the breeders rather than production environment. Stepwise regression analysis was used to determine the influence of the combined environment on production traits. The combined environment has a statistically significant (p < 0.0001) influence on all the production traits. The results indicate that the extent of the influence of the environment on production change through the growth curve. The environment’s influence was the greatest at weaning (9%) and yearling age (10%). Bonsmara weaning and yearling weights therefore show the largest potential for manipulation through management. The influence of individual environmental characteristics on all the Bonsmara cow production traits was then investigated by the same stepwise regression analysis. Most of the environmental characteristics were found to have a statistically significant (p < 0.0001) influence on the production traits. Rainfall and temperature had the largest influence on Bonsmara production traits. The negative influence of rainfall was attributed to the influence of rainfall on the quality of the grazing. The influence of temperature on production traits was small. The small negative influence of temperature could indicate that Bonsmara cows are well adapted to the main South African beef production regions. Finally, the relationship between Bonsmara cow size and reproduction was investigated by linear regression analysis. Results indicate that larger Bonsmara cows are to some extent more reproductive than smaller cows. The study confirmed that production environment influences beef cow efficiency. Bonsmara breeders however have a much larger influence on the efficiency of their cows through the implementation of management practices and breeding objectives. / Dissertation (MSc(Agric))--University of Pretoria, 2012. / Animal and Wildlife Sciences / unrestricted

Ruminants have a unique ability to acquire protein from non-protein nitrogen (NPN) sources, and to recycle nitrogen back into the rumen, instead of excreting all of it via the urine, faeces and milk. However, a high concentration of blood urea nitrogen (BUN) has a negative influence on conception. Additionally, a high dietary nitrogen intake poses a challenge to the environment in the form of ammonia emissions, eutrophication and bad odours. This calls for strategies to reduce the environmental impact of livestock production. Variation exists in the ability of cattle to recirculate nitrogen between as well as within cattle breeds. The purpose of this study was to investigate the effects of BUN concentration on reproductive performance in beef heifers under different management systems in South Africa. Serum samples from 369 Bonsmara heifers were taken in November and December 2010 to determine the BUN concentrations prior to the onset of the breeding season. Heifers were from five herds with different levels of protein supplementation during the weeks before the commencement of the breeding season. Body mass, age, body condition score (BCS) and reproductive tract score (RTS) were recorded at the same time as BUN concentration. Trans-rectal ultrasound and/or-palpation was performed four to eight weeks after the three-month breeding season to detect and estimate the stage of pregnancy. Days to pregnancy (DTP) was defined as the number of days from the start of the breeding season until a heifer was successfully mated. Logistic regression and Cox proportional hazards survival analysis were performed to estimate the effect of BUN concentration on subsequent pregnancy and DTP respectively, while stratifying by herd and adjusting for potential confounders. The correlations between BUN concentration, BCS and RTS were estimated using Spearman’s rho. Pearson correlations were used for the normally distributed variables of age and body mass. BUN concentration was not a significant predictor of pregnancy status but was a significant (P = 0.007) and independent predictor of DTP in heavily and some moderately supplemented herds. As BUN concentration increased, DTP also increased [hazard ratio (HR) = 0.827; 95% CI: 0.721 – 0.949; P = 0.007], while the chance of becoming pregnant decreased, although this was not statistically significant [odds ratio (OR) = 0.882; 95% CI: 0.772 – 1.007; P = 0.063]. Bonsmara heifers with higher BUN concentration, which suggests a better ability to recirculate nitrogen, might be at a disadvantage when the production system includes high levels of RDP supplementation because of this negative impact on reproductive performance. It is proposed that production systems be adapted to avoid selection against animals with an improved ability to recirculate nitrogen. / Dissertation (MMedVet)--University of Pretoria, 2013. / gm2014 / Production Animal Studies / Unrestricted

The effects of month on body weight, body condition scores, internal parasite prevalence and on nutritionally related blood metabolites were studied in Angus, Bonsmara and Nguni steers raised on sweet veld. Pre-slaughter stress was also determined using catecholamines, cortisol, dopamine, packed cell volume and serum creatinine levels. The blood chemical constituents evaluated included glucose, cholesterol, total protein, creatinine, urea, globulin, albumin, calcium, phosphorus, magnesium, aspartate amino transferase (AST), alkaline phosphatase (ALP) and creatinine kinase (CK). The Nguni steers maintained their body condition throughout the study period whereas Angus steers had the least body condition scores. Parasite levels were high during the rainy season and low during the dry season. The predominant internal parasites were Haemonchus (39.3 percent), Trichostrongylus (37.8 percent), Cooperia pectinita (25.5 percent), Fasciola gigantica (16.3 percent) and Ostertagia ostertagi (11.2 percent). The Nguni had the least parasite infestation levels and had high PCV levels. Nguni had higher levels of cholesterol and glucose (2.86 and 4mmol/l, respectively) than the other two breeds. Nguni and Bonsmara steers had higher (P<0.05) mineral levels. There were significant breed and month differences for glucose, cholesterol, creatinine, calcium, albumin, phosphorus, albumin-globulin ratio and ALP levels. Bonsmara was more susceptible to transport and pre-slaughter stress as it had the highest (P<0.05) levels of adrenalin (10.8nmol/mol), noradrenalin (9.7nmol/mol) and dopamine (14.8nmol/mol) levels, whereas the Nguni had the least levels of adrenalin (6.5nmol/mol), noradrenalin (4.6nmol/mol) and dopamine (4nmol/mol) levels. In conclusion, Nguni steers were better adapted to the local environmental conditions