The present thesis is a study of the factors that affect the assessment of rate and efficiency of gain in Yorkshire swine in the pre and post-weaning stages of growth. Calculations from metabolism data for growing swine and measurement of the milk production of Yorkshire sows were used to demonstrate the inability of a sow to produce sufficient milk (energy) for her suckling young about 12 to 20 days post-farrowing. A well balanced high energy creep ration was used in a commercial swine herd to overcome the energy debt to suckling piglets and provide for attainment of maximum growth, and hence, reduce the time required by them to reach 200 pounds. The affect of subnormal hemoglobin levels on pre-weaning growth rates and weaning weights of suckling piglets was investigated. The need of a continuous supply of iron and energy (creep ration) for suckling piglets to produce normal hemoglobin levels and to permit them to grow at their genetic potential was demonstrated. Energy content of gain and resting energy metabolism data were used to calculate post-weaning feed requirements of four experimental litters that were 12½ percent inbred. The post-weaning growth studies show uniformity of litter averages for several economic characters of swine, but variations within litters were high as shown by large standard deviations. The relationship between post-weaning rate of gain, feed efficiency and dressed carcass is discussed. The results demonstrate the possibility of rapidly improving rate and efficiency of gain in swine if selection is based on the performance of individual animals. / Land and Food Systems, Faculty of / Graduate

A total of 7,472 progeny from 4 lines of chickens, a Black Australorp, a New Hampshire and 2 Leghorn lines, their crosses and reciprocal crosses were assessed for their pre- and post-hatching body weights, pre- and post-hatching growth rates and their associated egg weights. The interrelationships of these traits as they influenced growth and 7-week body weight were evaluated. The effects of these relationships were jointly considered as they influenced the genetic variation and subsequent estimates of the heritability (h²) of these traits. The results of the investigation showed that an adverse environmental effect due to hatching was definitely established. It took 2 weeks of growth after hatching for the chicken body weights to attain the same level of association with 7-week body weight that was previously shown in the body weights of 18-day old embryos. Multiple regression analyses showed that 1-week body weight and any subsequent growth periods successfully accounted for variation in 7-week body weight. The h² estimates obtained for all weekly growth rates as well as the 1-3, 3-7, and 1-7 week growth rates strongly indicated a major source of additive genetic variance was available in poultry populations that heretofore has not been directly utilized in body weight selection programs. / Land and Food Systems, Faculty of / Graduate

A general property of animal populations is their failure to continue increasing in number indefinitely, even when the habitat may contain enough resources to support more animals than are present at the time. Certain populations of blue grouse have expressed this property by failing to increase when the habitat has undergone changes that have produced striking increases in past cases. Other populations have expressed it by arresting their increase before the resources of the habitat were exhausted. In blue grouse populations on Vancouver Island, adult mortality is constant and it is restricted recruitment that has held these populations stable in the periods they have been studied, even though sufficient young have been produced to support an increase. The hypothesis that the behavior of territorial adult males affects the local occurrence of recruits and other grouse in general on the summer range was tested by studying dispersion during the breeding period. Information on dispersion and social behavior were obtained from nine grouse fitted with miniature radio transmitters. Data from non-instrumented birds supplement this work. The principal finding is that there was no evidence of social interaction causing females and immature males to occur in special places, and that no interaction of a sort that could affect recruitment occurs between blue grouse on their summer range. It is alternatively suggested that such behavior occurs in winter. Other conclusions are that the onset of estrus induces hens to seek out and become localized near a mate, that several hens may seek out the same mate, and that no lasting pair-bonds are formed. Each type of reproductive activity in blue grouse has a distinctive movement pattern, and perhaps movement rate, associated with it. Excepting for hens In estrus who briefly seek out mates, and some yearling males who are prevented by adults from remaining on territories, movements and local occurrence within the breeding range are unaffected by social interaction with other grouse. / Science, Faculty of / Zoology, Department of / Graduate

A study was conducted to make a genetic evaluation of egg mass (weight of the total eggs laid in a given period) in order to determine its genetic potential as a new criterion for selection as compared to the conventional selection program based on egg number (early and full production records). In addition, biometrical evaluations of some egg component traits: yolk weight, albumen weight, shell weight, percent yolk, percent albumen, percent shell, albumen percent solid, yolk percent solid, yolk percent protein, albumen percent protein, yolk solid and albumen solid were made. The aforementioned traits were measured on 3 random bred lines of chickens in quarterly periods through the laying year. Within each line, the heritability estimates of egg number and egg mass for any given period (275, 325, 450 and 540 days of age) were found to be in close agreement. In general, for egg number and egg mass, selection from early production records showed higher gains per unit of time than full year production records, A negative genetic correlation between egg number traits and egg weight traits and a positive genetic correlation between egg mass and egg weight traits was found, therefore, selection for egg mass was recommended. Relative merit of early and full year egg records as selection criterion was discussed in the light of the results obtained for the three lines. It was concluded that the decision as to which criterion should be used would have to depend upon the genetic properties of the population in question. Line effects were found to be significant for all the egg component traits studied, except percent shell, A season-age effect was also found to be significant in all the traits studied. Season-age by sire interactions were found to be non-significant for all the traits in all the three lines. The importance of yolk size from a human nutrition standpoint was discussed. A selection program based on total yolk weight produced by a hen in a given period (yolk mass) was suggested. Because of the water in the egg being an essential nutrient for the developing chick embryo, it was suggested that selection be made on the egg solid or egg solid mass (total amount of solid laid by a hen in a given period). The heritability estimates of albumen percent solid and albumen percent protein were high and of the same magnitude. It was, therefore, suggested that an increase in percent protein in albumen should be achieved by selection of albumen percent solid. / Land and Food Systems, Faculty of / Graduate

Please read the abstract in the section, 00front of this document</P< / Dissertation (MSc (Agric) Production Physiology)--University of Pretoria, 2008. / Animal and Wildlife Sciences / MSc Agric / unrestricted

In this study whole-genome SNP data from 1977 animals, originating from thirteen sheep breeds in South Africa was analysed. The animals were classified into three production types: dual-purpose (Afrino, Dohne Merino, Dormer, Merino, SA Mutton Merino), meat (Black Headed Persian, Damara, Dorper, Meatmaster, White Dorper) and indigenous (Fat-tailed, Namaqua Afrikaner, Pedi). All animals were genotyped using the Illumina Ovine 50K SNP BeadChip. The aim was to investigate the genetic diversity and inbreeding levels of both indigenous and commercial sheep breeds in South Africa. The populations were first investigated individually to analyse within population diversity, whereafter they were merged in order to perform between population diversity analysis. During sample-based quality control, a total of 207 animals were removed due to low call rates. The number of SNPs remaining after marker-based quality control ranged from 32 422 to 44 778. Average observed heterozygosity values of 0.360, 0.355 and 0.340 were observed for dual-purpose, meat and indigenous populations respectively. Average linkage disequilibrium (LD) estimates were highest for dual-purpose populations at 0.277, followed by meat type populations at 0.259, and the lowest LD was observed for indigenous populations at 0.255. Dual-purpose, meat and indigenous populations showed average minor allele frequencies (MAF) of 0.393, 0.427 and 0.444 respectively. Principal component analysis (PCA) and ADMIXTURE results showed a clear differentiation between the dual-purpose populations, and the meat and indigenous populations. Average inbreeding coefficient (Fis) estimates of 0.008, -0.029 and 0.003 was observed for dual-purpose, meat and indigenous populations respectively. All populations showed a decline in effective population size (Ne) across generations. For all populations, the highest percentage of ROH was found in the shortest length category (1-3.99 Mb), and the largest number of ROH were observed on the first ten chromosomes. The average FROH estimates was highest for dual-purpose populations at 0.015, followed by the meat type and indigenous populations at 0.011 and 0.005 respectively. An unrooted phylogenetic tree based on pairwise Fst estimates showed a divergence of the dual-purpose populations from the meat and indigenous populations. Results from this study indicated lower variation within dual-purpose populations, and higher variation within indigenous populations. High population differentiation was observed between the various production types. / Dissertation (MSc Agric) (Animal Science: Animal Breeding and Genetics))--University of Pretoria, 2020. / Animal and Wildlife Sciences / MSc Agric) (Animal Science: Animal Breeding and Genetics) / Unrestricted

This study aimed to identify genomic regions of significance that are associated with body weight traits and reproduction traits in sheep by using estimated breeding values in a genome wide association study (GWAS). The following traits were investigated: body weight recorded at selection age of 14 months (BW), number of lambs born (NLB), number of lambs weaned (NLW) and total weight of lamb weaned (TWW). A total of 411 animal were genotyped using the Illumina® Ovine SNP50 BeadChip, and consisted of 152 Afrino, 129 Cradock Merino and 130 Grootfontein Merino sheep. Quality control (QC) were implemented using PLINK v1.07 where the parameters were set as 90% for individual call rate, 95% for SNP call rate, minor allele frequency of less than 2% and P <0.001 for Hardy-Weinberg equilibrium. Population parameters were calculated per dataset. The average MAF values estimated for the populations were 0.252, 0.372 and 0.372 for the Afrino, Cradock Merino and Grootfontein Merino, respectively. Inbreeding coefficients were estimated at - 0.025 (Afrino), - 0.025 (Cradock Merino) and 0.002 (Grootfontein Merino). The expected heterozygosity was 0.363 for the Afrino and 0.369 for both Merino populations. All three sheep populations had low inbreeding levels and moderate genetic variation. The population genetic substructure, ancestry proportion and genetic relatedness between the populations were investigated via principal component analysis (PCA) and admixture plots. These plots corresponded to the populations’ selection practises and breeding programs as well as to the geographical locations where the individuals were kept. The GWAS was applied to each dataset separately and per trait using the efficient mixed model association eXpedited (EMMAX) software and visualised by Manhattan plots. Nine suggestive SNPs were identified to be in possible association with the traits. Of these nine, seven SNP were identified to be in close proximity or linked to previously annotated genes. Seven genes were identified which were in association with growth and reproduction traits. The genes SIX6, C14orf13 and TRPS1 showed the most promise for body weight and growth traits. For reproduction and fertility traits the genes LIG1, CABP5, GRIK3 and HDAC9 warrants further investigation. / Dissertation (MScAgric (Animal Science))--University of Pretoria 2020. / Grootfontein Agricultural Development Institute / Animal and Wildlife Sciences / MScAgric (Animal Science) / Unrestricted

The aim of this thesis was to evaluate alternative management options for the smallholder dairy cattle production system in South Africa (SA). Specific objectives included, were to benchmark cow performance in the smallholder (SH) against their counterparts in a high-input system (H), to develop a SH herd model, and to evaluate alternative management options for the improvement of smallholder dairy herd profitability. Data on production (305-day yields of milk, fat and protein), lactation length, somatic cell count (SCC), and reproductive traits (age at first calving (AFC), and calving interval (CI) obtained from the South African National Dairy Animal Improvement scheme (NDAIS) were used in a benchmarking study. Least squares means per trait were compared between the two systems, and lactation curves for roduction traits and SCC were plotted. Results revealed that mean yields of milk, fat and protein were significantly (P<0.05) lower in the SH (4 097±165, 174±5.1 and 141±4.5 respectively) compared to the H system (6 921±141, 298±4.7, and 245±4.1, espectively). Mean lactation length was significantly (P<0.05) shorter for the SH (308±15.1) compared to the H system (346±12.8). Log-transformed SCC was significantly (P<0.05) higher in the SH (2.41±0.01) relative to the H system (2.27±0.01). Cows in H herds exhibited typical lactation curves, in contrast to flat and low-peaking curves obtained for the SH system. SH cows had significantly (P<0.05) older AFC (30±0.5) than those in the H system (27±0.5). There was no significant difference (P<0.05) in CI between the two systems. A bio-economic SH herd model was developed by adapting a previously developed model for the H system in SA. Parameters used were obtained from NDAIS, survey data, personal communications, and literature. The model integrated herd dynamics, outputs, nutrient energy requirements, management, and their associated economics. Nutrient energy requirements were estimated for maintenance, growth, reproduction, and lactation. The developed SH herd model was used to evaluate alternative herd management options, using the partial budget approach. Milk yield (MY), live weight (LW), AFC, and CI were used as indicators of cow performance. Herd management practices studied were herd size (HS), replacement rate (RR), feeding system (FS), breeding methods (natural service vs artificial insemination), and source of replacement heifers (raising vs. buying in). Improvements in profitability were attained by increasing MY or increasing herd size, using small to medium sized cows, or reducing AFC, CI or RR. Break-even points were 3 687.4 l/year, 500 kg, 29 months, 420 days and 25% for MY, LW, AFC, CI, and RR, respectively. Profitability was mostly sensitive to the prices of milk and feed. A drop in the price of milk below R4.50/l or increase in the cost of feed above R5.60/kg DM generally resulted in non-profitability. Relying on pasture only for feed was non-viable, and supplementation of pasture with concentrate was the most profitable feeding system. Feeding systems based on supplementation of pasture with concentrate, and silage were resilient to fluctuations in the price of milk, remaining profitable even when the price dropped to R4.10/l. Using artificial insemination or buying-in replacement heifers are additional management strategies that increase SH dairy farming profitability. These recommended management options should be used in combination for achieving maximum herd profitability. / Thesis (PhD (Animal Science))--University of Pretoria, 2020. / UP Postgraduate/Doctoral Research Bursary / Animal and Wildlife Sciences / PhD (Animal Science) / Unrestricted

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