Masters Degrees (Animal Sciences)
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- ItemSustainable management of breech flystrike in sheep by manipulating tail length: the effect of tail docking on lamb welfare as well as the genetics of ovine tail length(Stellenbosch : Stellenbosch University, 2024-03) Teubes, Megan; Cloete, Schalk W. P. ; Dzama, Kennedy; Scholtz, Ansie; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.ENGLISH ABSTRACT: It is expected that society will place more pressure on animal production systems to implement change, given increased awareness of ethical animal husbandry and global sustainability. Increased temperatures, due to climate change, are likely to provide favourable conditions for insect activity, thereby inducing favourable conditions for blowfly activity. Myasis following on the deposition of eggs by gravid females of the Australian sheep blowfly, Lucilia cuprina, in the breech area of Merino sheep compromises animal welfare and results in high production losses. Tail docking is a commonly accepted way to render lambs less attractive to breech flystrike as adult sheep, by reducing dag formation in the breech area. This procedure is considered as invasive and painful, with an immediate impact on lamb welfare. Therefore, this study assessed the degree of discomfort lambs experienced both during tail docking and after the procedure was conducted. A total of 228 lambs were randomly assigned to a treatment group whose tails were docked with a hot-blade and a control group where lambs were left intact after tail length was measured. Behavioural assessment of the two groups during tail docking recorded higher (P < 0.05) levels of agitation and vocalisation in the treatment group, while the control group were more likely to be calm. These behavioural patterns persisted in the post-procedural phase with no differences (P > 0.05) between recordings 2 or 10 minutes after docking. The second objective was to determine if there is sufficient genetic variation to select Merino sheep for shorter tail length, on the assumption that selection for shorter tails may provide the same benefits as docking without the painful docking procedure. Tail length had a moderate heritability of 0.30 ± 0.08 with a small maternal effect (0.08 ± 0.04) and nonsignificant permanent dam environmental effect. However, selection for shorter tails will reduce the size of lambs if breeding values are not adjusted for skeletal size by including docking weight as a covariate when breeding values are estimated. The final objective of the study was to assess the effect of breeding for shorter tails on other production traits by estimating genetic correlations between tail length and hogget traits. Tail length was genetically correlated to clean fleece weight (0.36 ± 0.18) and total wrinkle count (0.33 ± 0.15). Selection for a reduced tail length may thus compromise fleece weight and result in plainer (less wrinkly) sheep. The latter genetic correlation is favourable, given the well-recorded higher predisposition of wrinkly sheep to breech strike. It was concluded that tail docking results in at least temporary discomfort in young lambs, thereby compromising their welfare. This procedure could potentially be replaced by selection for shorter tails. However, the reduction of tail length to levels where breech strike is expected to be minimised may take several decades.
- ItemThe potential role of semiochemicals in the reproductive management of cheetahs in captivity(Stellenbosch : Stellenbosch University, 2024-03) Tommasi, Alexia; Esposito, Giulia; Molotsi, Annelin H. ; Koziel, J. A.; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.ENGLISH ABSTRACT: Cheetah (Acinonyx jubatus) numbers have been reduced to less than 7,100 individuals, and the species is currently listed as vulnerable according to the IUCN. Captive breeding has been used for a long time as a method of conservation of the species. Unfortunately, cheetahs have proven difficult to breed in captivity and females are susceptible to asymmetric reproductive aging and endometrial hyperplasia, which is prevented by breeding them when they are still young adults. However, younger females show a significantly lower frequency of mating behaviour than older females, which negatively affects breeding introductions and, therefore, decreases mating success. The urine of male cheetahs plays an olfactory role in mate choice of female cheetahs, and the two most successful captive breeding methods imply the involvement of semiochemicals in cheetah courtship. Therefore, the aim of this study was to investigate the role of semiochemicals in the breeding behaviours of cheetahs to potentially develop a synthetic scent that can be used in captive cheetah breeding programs. For this purpose, three trials have been conducted. In the first experiment the marking fluid (MF) of 4 breeding (B; age: 8.9±1.3 years old) and 4 non-breeding (NB; age: 5.5±0.8 years old) male cheetahs was analysed to identify differences in the volatile organic compounds (VOCs). Of the fifty-three VOCs identified, twelve VOCs were detected in the MF of all the males. Five of the twelve VOCs (i.e. dimethyl disulfide, benzaldehyde, acetophenone, phenol, and indole) are known to be involved in attraction/sexual behaviour in mammals. Among these, the relative concentration (RC) of indole was significantly higher in the NB group (0.06 ± 0.02), and the RC of dodecanoic acid was significantly higher in the B group (0.12 ± 0.1). In the second trial, benzaldehyde, acetophenone, indole, dimethyl disulfide and phenol were used according to the average RC of these VOCs from the breeding males’ group in the previous trial. Each VOC was applied to wooden logs (with water as the control), and seven male cheetahs were exposed to the logs. There was no significant effect of any VOC on the cheetah's behavioural response, however, the males did react negatively towards benzaldehyde and dimethyl disulfide. In the third trial, a synthetic scent (SS) was created using the five pheromones identified in the MF of the males of experiment one. Eight female cheetahs of different age groups (2–4 y and 6–8 y) were enrolled in this trial. The SS did not have a significant effect on the total frequency of oestrous behaviour displayed by the females used in this study, however, the SS did significantly increase the sniff behaviour in general. Findings from this novel study indicated that VOCs can be isolated in the MF of male cheetahs, but no conclusive evidence was obtained that VOCs can be used in the development of a SS for use in captive cheetah breeding programs. Nonetheless, the results of this study does indicate that VOCs do have an effect on cheetahs and their behaviour.
- ItemPeriparturient rumen undegradable protein and colostrum quality in Dohne Merino and Meatmaster ewes(Stellenbosch : Stellenbosch University, 2024-03) Seegmuller, Andre Joseph; Van Zyl, Johan Hendrik Combrink; Lambrechts, Helet; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.ENGLISH ABSTRACT: Sheep and goat farming are considered vital to sustain the economy in extensive farming regions, due to the ability of these species to thrive in very warm and arid environments. Although mutton and lamb production only contributed 3.76% to the total gross value generated from animal products during the last decade, sheep is still the second most abundant livestock species, after poultry, in South Africa. Due to recent declines in sheep numbers, strategies to optimise production are needed. The improvement in the number of lambs sold per ewe, attainment of weaning weight sooner, and optimized lamb growth rate, can all contribute to increase the revenue generated from fewer animals. Two suggested strategies to achieve higher lamb survivability and lamb growth include the optimization of the milk production and composition produced by ewes, and in particular improving colostrum production and quality through the provision of supplementary feeding, thereby improving passive immunity leading the lower lamb mortality. To ensure sustainable lamb and mutton production and to ensure viability of sheep production in South Africa, it is imperative that local sheep producers continuously adapt and improve their production practices to be able to contribute to job and food security while ensuring sustained profitability. The objectives of the study were to evaluate the effect of increased pre-partum rumen undegradable protein (RUP) intake on colostrum quality, colostrum viscosity, lamb survival rate, lamb growth rate as well as the effect of all of the above on extensive (Meatmaster) and intensive (Dohne Merino) sheep breeds. The first part of the study determined the effect of the level of pre-partum RUP supplementation of ewes on colostrum and milk production, as well as lamb rearing ability. Inclusion levels of 220 g/kg and 400 g/kg RUP of total crude protein (CP) were evaluated. The breed effect was also investigated in this study to evaluate the effect of partitioning of nutrients towards production. During the 11-week trail post-partum production performance of 18 Meatmaster (MM) and 18 Dohne Merino (DM) ewes were compared. Daily dry matter intake (DMI) and weekly body weights were used to calculate weekly average daily gain (ADG) and feed conversion ratio (FCR). Blood samples were collected 1 week pre-partum, at parturition and 1-week post-partum to determine the total protein, albumin and alkaline phosphatase (ALP) enzymatic levels in the plasma in the ewes. Colostrum samples were collected 1-, 10- and 18 hours post-partum to determine the colostrum quality over time. Milk samples were collected at 2-, 4-, and 6 weeks post-partum to investigate the composition of the milk at three different stages of lactation. Diet RUP level did not affect DMI, ADG or FCR of the ewes in this study. Ewe breed influenced somatic cell count (SCC), butterfat concentration and total solids, percentage lactose, and milk urea nitrogen for all colostrum samples. The 22% RUP diet fed resulted in the 18 h colostrum samples that were characterized by higher viscosity, immunoglobulin G- (IgG ) and total protein levels. Milk produced by the MM ewes was characterized by higher butterfat concentration and total solids recorded for all three stages of lactation. The milk produced by the DM was characterized by higher SSC recorded during mid-lactation. No differences in udder or teat dimensions were observed. In conclusion, ewe breed had a limited effect on milk production parameters recorded in this study, while diet RUP level resulted in a moderate response with regard to colostrum- and milk production. The second part of the study investigated the effect of ewe breed and pre-partum diet RUP level on ewe colostrum production and the effect thereof on pre-weaning lamb growth and passive immunity. Four treatment combinations were used in this trail; lambs born from Meatmaster ewes that received the 22% RUP pre-partum diet (22%MM), lambs born from Dohne Merino ewes that received the 22% RUP pre-partum diet (22%DM), lambs born from Meatmaster ewes that received the 40% RUP pre-partum diet (40%MM), lambs born from Dohne Merino ewes that received the 40% RUP pre-partum RUP diet (40%DM). During the 7-week post-partum period lambs were weighed weekly to determine weekly weight gain and average daily gain (ADG). Blood samples were collected to determine success of serum immunoglobulin G (Brix’s %) transfer to lambs. Results indicate that pre-weaning lamb growth was not influenced by ewe colostrum- and milk production and quality respectively. Significant interaction between the 4 treatment combinations were however found for birth weight, and ADG and weaning weight of lambs. No difference between treatment combinations was found in birth weight and weaning weight, although the ADG of the 22%MM were lower compared to the 40%DM treatment. Ewe pre-partum diet did not affect lamb serum IgG level and weaning age. The ewe breed did not have any effect on age at weaning and lamb serum IgG level. It was concluded that ewe colostrum- and milk quality produced by the ewes receiving the respective treatments had little response on lamb production. Results from the current study therefore indicate that 22% RUP during the pre-partum period of ewes is sufficient to both Dohne Merino and Meatmaster ewes lambing in intensive pens as little response on both vectors were found in ewe and lamb results. It is therefore concluded that, under the specific conditions of the trial, that the additional cost that would be incurred by increasing the RUP level above 22% of crude protein, could not be justified.
- ItemThe influence of superstimulation protocol on oocyte developmental competence in dairy cattle(Stellenbosch : Stellenbosch University, 2024-03) Grobler, Barend Jacobus; Lambrechts, Helet; Van Zyl, Johan Hendrik Combrink; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.ENGLISH ABSTRACT: The increasing demand for dairy products globally, places increasing pressure on dairy producers to select animals for higher milk yield. In South Africa, market forces and the resulting economic pressure have resulted in a decline in the number of dairy producers, which necessitates that existing producers need to increase the average herd size and select dairy animals for a high milk yield, to remain sustainable in the South African dairy sector and to meet the ever-increasing demands of the consumer. The negative impact of selecting dairy animals for high milk yield is reflected in the decline in fertility of dairy animals, not only in South Africa, but globally. The purpose of this study was to evaluate the effects that age, lactation stage, and superstimulation program have on the fertility of Holstein dairy cows. The effect these factors have on fertility was assessed by looking at oocyte developmental competence in an in vitro embryo production system. The selection of the Holstein breed as donor animals, is based on the substantial representation of this dairy breed in the dairy industry. Twelve Holstein cows were selected as oocyte donors and allocated to three different age categories, i.e.3-4 years, 5-8 years, and 10-11 years; and according to stage of lactation, i.e. dry (non-lactating), early lactation (<120 Days in milk) and mid-lactation (>120 Days in milk). The donor animals were then randomly allocated into four different FSH-concentration superstimulation treatment groups (i.e. Control: 0 mg, Low: 150 mg, Medium: 180 mg, High: 240 mg). The superstimulation program and transvaginal oocyte retrieval (TVOR) were repeated every 28 Days, for four repetitions, to ensure that each donor was subjected to each treatment. In this study, the age of the donor and the FSH concentration had no significant effect on follicular wave response, oocyte developmental competence, or embryo yield in an in vitro embryo production system. Lactation stage, although not having a significant effect on follicular wave response, significantly influenced the number of embryos, with non-lactating cows producing 5.63 ± 0.76 embryos, compared to early-lactation cows (2.96 ± 0.53 embryos), and mid-lactation cows (1.97 ± 0.72 embryos). The findings from this study highlighted the impact of dairy cow nutrition on the quality of oocytes, which was more pronounced than the influence of cow age and FSH treatment. The high demand for nutrients in lactating animals disrupts the delicate physiological balance that is required to ensure oocyte developmental competence, in vivo as well as in vitro. The negative impact of lactation on oocyte developmental competence, and the partitioning of nutrients in favour of milk production at the cost of reproduction is clearly highlighted in this study.
- ItemManipulation of the rumen environment to increase rumen undegradable protein fraction of feedstuffs(Stellenbosch : Stellenbosch University, 2024-03) Van Rensburg, Waldo; Brand, Tersius Swanepoel; Van Zyl, Johan Hendrik Combrink; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.ENGLISH ABSTRACT: The digestive tract of ruminants follows the order of rumen, reticulum, omasum and abomasum, where at least 50 % or more of the total digestion of feed intake occurs. Digestion of protein is a broad spectrum explained by the nitrogen metabolism pathways of any ruminant; dietary protein consumed by a ruminant can split into rumen-degradable and undegradable protein. The rumen itself produces protein for use, in the form of ammonia nitrogen, endogenous nitrogen and microbial protein. Thus, when rumen degradable protein is found to be in excess, the protein will be lost through urine, as urea will be metabolized in the liver. The loss of protein or nitrogen due to excess ammonia can thus be an extreme expenditure and methods to minimize the loss and the cost of feeding protein are greatly researched. These losses whether it be for maintenance or production purposes in ruminants can be compensated or overcome if methods are used to increase the undegradable proteins. Meaning one can reduce the feeding of protein to improve production without diminishing the protein needs of the animal. Methods of protecting feedstuff have shown results to increase rumen undegradable proteins (RUP) for example encapsulation, extrusion, or formaldehyde treatment of feeds. These methods of protecting proteins or increasing the availability thereof still have to be modified into the diet itself, thus extra cost put in processing the feed to achieve this increased availability of RUP. The aim of this study will be to manipulate the rumen fermentation, ruminal pH and/or microbes to provide potentially improved protein availability for use to the animal, without the modification of the feed. The inclusion of tannins (Farmatan D®- 0 %, 0.25 %, 0.5 %, 0.75 %, 1 %), lipids (plant oil extracts- 0 %, 1.25, 2.5 %, 3.75 %, 5 %) and sodium bicarbonate (sodium bicarbonate- 0 %, 0.75 %, 1.5 %, 2.25 %, 3.0 %) were incorporated into the diet for five cannulated sheep, each receiving its own inclusion. Tannins in the past were only to be seen as detrimental to the animal, but with further studies have shown it involves the type of tannins used namely condensed tannins that has this effect. The other type of tannins, which are hydrolysable, have been shown to decrease urinary nitrogen loss and have abilities to manipulate the rumen and bind to microbial protein that can lead to greater availability of protein for use. The inclusion of lipids, especially higher inclusion thereof has led to fibre coating in the rumen, which resulted in a manipulation of the rumen itself, potentially increasing the RUP. Lastly the inclusion of the sodium bicarbonate was incorporated into the diet, with emphasis on a high grain diet to decrease the pH of the rumen to gain greater results when used. The inclusion of sodium bicarbonate increased the pH with the increasing inclusions in the diet. The high grain fed diet with each respective inclusion, was used to determine (using in vitro) the potential protein degradation and fractional rate of digestion due to the manipulation of the rumen. The optimum inclusion for tannins, lipids and sodium bicarbonate were determined, after each in vitro study was completed. This study will be especially beneficial for further research of the tannins used and determining the RUP available after in vitro trials. The inclusion of all three these supplementations to the diet manipulated did not show desired results in the manipulation of the rumen degradation. Even with the maximum inclusion of Farmatan D® and lipids in the diet, as theorized could lead to great protein availability, did not occur. Whereas the maximum inclusion of sodium bicarbonate did not have optimum availability of proteins, and did not show any significant results. This was determined by using in vitro methods for protein degradation and fractional rate of digestion for all the respective inclusion levels of the three supplementations, did not lead to rumen degradation.