Cattle are widely used in cultural landscape management in Sweden today. However, there are few recent studies concering what types of cattle or what breeds of cattle that are being used for cultural landscape management. The aim of this study is to examine the use of cattle in cultural landscape management in Sweden, focusing on the aims and the types of cattle and cattle breeds that are used. I will also examnine why these specific types of cattle and cattle breeds are being used. To answer these questions a literature study, combined with three case studies and interviwes was conducted. The results show that there are a series of aspects that effect what type of cattle that is being used for cultural landscape management. These aspects range from the aim of the cultural landscape management, the modern breeding objectives, animal welfare and the milk and meat yield of the different breeds. The result also show a need for further studies on the subject.

Thesis advisor: Katie Rapier / Through the years, people began to breed their dogs and cats with the intention for the pets to be useful in a certain skill. However, that has shifted to focus on their looks rather than their skills thanks to kennel clubs imposing standards on each breed. This has led irresponsible breeding practices to occur which in turn caused breeds to evolve negatively as breeds began to suffer from preventable genetic disorders and negative physical changes. Genetically manipulating soon shifted from pets to humans with PGD/IVF and CRISPR-Cas9. At first, there was a focus to use these methods to help cure and prevent genetic disorders. That has since shifted to people wanting to create the perfect child. In this thesis I will argue that designer breeds help lead the way to designer babies, and that any genetic manipulation to embryos should only be done if a medical reason is present. / Thesis (BA) — Boston College, 2020. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Departmental Honors. / Discipline: Philosophy.

Some dairy breeds have too few animals genotyped for within breed genomic selection to be carried out with sufficient accuracy. As such, the level of linkage disequilibrium within each breed as well as consistency of gametic phase across breeds was studied. High correlations of phase (>0.9) were found between all breed pairs at this same SNP density. The efficacy of imputing animals genotyped on lower density (6k and 50k) panels was then explored in order to increase the size of the reference population with 777k genotypes in a cost-effective manner. These results showed high accuracies (>0.92) in all imputation scenarios studies, using both a within breed and a multi-breed reference population for imputation. It was concluded that given the results of both of these studies, pooling breeds into a common reference population for genomic selection should be a viable option for accurate genomic selection in breeds with few genotyped individuals. / NSERC, USDA, CDN, DairyGen, Ayrshire Canada, Guernsey Canada, Semex, L'Alliance Boviteq Inc.

A genetic study of four commercial goat breeds in South Africa was performed using microsatellite markers. The commercial breeds included the Boer goat, Savanna, Kalahari Red and the Angora goat. Indigenous goat populations from Delftzijl and Groblersdal were also included in this study. Seventeen microsatellite markers were tested to determine the genetic variation. Genetic variation within the breeds were relatively high with heterozygosity values ranging from 57% for the Boer goat, 68% for the Kalahari Red, 69% for the Savanna goats and 70% for the Angora goats. First values indicated that the Savanna and Boer goat are genetically the closest (0.114), while the Kalahari Red and Boer goat are the least related (0.237). Phenotypic measurements included height, length, depth, heart girth, pelvic length and width for a phenotypic description. Significant differences were observed in the phenotypic measurements among all the breeds. The genetic and phenotypic differences indicate that these goats can be distinguished as different breeds. Results of this study contribute genotypic information of the commercial goats in South Africa. Copyright / Dissertation (MSc)--University of Pretoria, 2007. / Animal and Wildlife Sciences / unrestricted

No description available.

Thesis (M. Tech.) - Central University of Technology, Free State, 2010

Thesis (MScAgric)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Research conducted on beef cattle in Botswana investigated both growth and reproduction. These studies however, did not specifically determine the influence of the different environmental factors on growth in the Tswana and Composite beef cattle breeds. The establishment of a national beef herd recording and performance testing scheme requires knowledge on the appropriate adjustment methods of field data for the fixed effects such as sex of calf and age of dam. A fair comparison of birth and weaning weights between male and female calves, and calves born from young, mature and old dams will be derived from these adjustment factors. There is no information on adjustment factors for the Tswana and Composite cattle breeds in the country. Genetic parameters for growth traits in these breeds are not known and are needed for the implementation of the performance scheme in Botswana. The Composite breed resulted from a controlled crossbreeding programme using the Simmental, Brahman, Tswana, Tuli and the Bonsmara breeds. The Tswana animals are indigenous to the country and were sourced locally at the beginning of the growth evaluation trial in the two breeds. The objectives of the study were to use data collected from Tswana and Composite cattle breeds to estimate the influence of non-genetic factors on growth traits in the two breeds; to develop adjustment factors for the effects of sex of calf and age of dam; and to estimate genetic parameters (heritabilities and genetic correlations) for future genetic evaluations in both breeds. Data were collected over the period 1988 to 2006. A total of 2 257 records for the Composite breed and 5 923 records for the Tswana breed were available for analyses. Growth characteristics of interest in this study were birth weight (BW), weaning weight (WW), pre-weaning average daily gain (ADG1), 18 months weight (18MW) and post-weaning average daily gain (ADG2). Study 1 indicated that non-genetic effects of breed of calf, sex of calf, month and year of birth, previous parous state, weight of cow at parturition, age of dam, and age of calf at weaning significantly affected BW, WW, 18MW, ADG1 and ADG2 in both breeds. The Composite breed had higher BW, ADG1 and WW whereas the Tswana had higher ADG2 and 18MW. Pre-weaning growth rate increased with an increase in the age of the dam, reaching a peak in mature (5-12 years) cows and declined in cows 13 years and older. Conversely, post-weaning growth rates declined as age of dam advanced but increased in old (13 years and older) dams. Male calves were heavier than female calves for all the growth traits. Birth weight increased as calving season progressed whilst a decrease in WW was observed over the same period. Heifers gave birth to lighter calves when compared to mature multiparous dams. The Composite breed can therefore be considered for weaner production under ranch conditions while the Tswana can be reared under extensive systems due to its adaptability to the environment. Additive correction factors for effects of sex of calf and age of dam on BW and WW were studied separately for the Tswana and Composite in study 2. The least squares means procedure was used to derive age groups and the adjustment factors. The three age groups were young (4 years and below) dams, mature (5-12 years) dams and older (13 years and above) dams. Male calves were heavier than their female counterparts. The sex of calf adjustments for BW and WW were 2.75 and 8.21 kg in the Tswana, and corresponding values for the Composite 2.84 and 10.11 kg, respectively. Birth weight and WW increased as age of dam increased, reached maximum in mature dams and declined in older dams. Age of dam adjustment factors for BW in the 3, 4 and 13+ years age groups for the Tswana were 1.74, 0.96 and 1.87 kg, respectively. The corresponding values for the Composite were 2.28, 0.94 and 2.06 kg, respectively. Age of dam adjustment factors for weaning weight in the Tswana were 10.36 and 5.46 kg for age groups 3-4 and 13+ years, respectively. Adjustment factors for WW in the Composite were 13.84, 3.20 and 9.58 kg for age groups 3, 4 and 13+ years. The differences in adjustment factors obtained between the two breeds emphasize the need to compute and apply these factors within breed. Study 3 involved the estimation of genetic parameters for BW, WW, ADG1, 18MW and ADG2. Single-trait and multi-trait analyses were used in the estimation of (co)variance components by fitting an individual animal model (AM) and the animal maternal model (AMM) for the two breeds. Direct heritabilities for BW, WW, ADG1, 18MW and ADG2 in the Tswana were 0.45, 0.32, 0.37, 0.31 and 0.31, respectively from a single-trait AM analysis. Fitting the AMM resulted in direct heritabilities of 0.31, 0.20 and 0.16 for BW, WW and ADG1, respectively, while the maternal heritabilities were 0.11, 0.15 and 0.21, respectively. For the Composite the direct heritabilities for BW, WW and ADG1 were 0.58, 0.32 and 0.30, respectively with single-trait AM. Partitioning using the AMM resulted in the direct heritabilities for BW, WW and ADG1 of 0.55, 0.17 and 0.14, respectively, while corresponding maternal effects were 0.09, 0.15 and 0.15, respectively. The genetic correlations between direct and maternal effects were positive and ranged from 0.20 to 0.89. When using the multi-trait analysis and fitting the AM, the direct heritabilities for the Tswana were 0.45, 0.37, 0.34, 0.39 and 0.31 for BW, WW, ADG1, 18MW and ADG2, respectively. Genetic correlations between the growth traits ranged from 0.16 to 0.97. Direct (and maternal) heritabilities for BW, WW and ADG1 were 0.31(0.11), 0.19(0.15) and 0.14(0.17), respectively, in the Tswana. Correlations between direct heritabilities for BW, WW and ADG1 ranged from 0.45 to 0.95, while maternal effects ranged from 0.12 to 0.99. The magnitude of the heritabilities indicates an existence of the opportunity to make genetic progress through selection in both breeds. Selection based on WW seems to be the ideal procedure to bring genetic improvement in the Tswana without detrimental long term effects. / AFRIKAANSE OPSOMMING: Navorsing wat op die vleisbeesrasse in Botswana gedoen is, het hoofsaaklik op beide groei en reproduksie gehandel. Hierdie studies het egter nie spesifieke gefokus op die bepaling van die invloed wat verskillende omgewingsfaktore op die groei van saamgestelde (d.i. Composite) en die Tswana vleisbeesrasse het nie. Die bepaling van ʼn nasionale vleisbees rekordhouding- en prestasietoetsskema verg kennis van die mees gepaste metode om velddata vir vaste effekte soos geslag van die kalf en ouderdom van die moeder aan te pas. Hierdie aanpassingsmetodes sal lei tot die regverdige vergelyking van geboorte- en speengewigte tussen manlike en vroulike diere, sowel as van kalwers gebore van jong, volwasse of ou moeders. Tans is daar geen inligting oor aanpassingfaktore vir die Tswana en saamgestelde vleisbeesrasse in Botswana bekend nie. Geen genetiese parameters vir groei-eienskappe vir geeneen van die rasse is beskikbaar nie en word benodig vir die implementering van die prestasie skema in Botswana. Die saamgestelde ras is die produk van ʼn beheerde kruisteeltprogram, wat onderskeidelik die Simmental, Brahman, Tswana, Tuli en die Bonsmara beesrasse ingesluit het. Die Tswana ras is inheems aan Botswana en vanaf plaaslike bronne vir die groei evaluasie studie bekom. Die doelwitte van die studie was eerstens die analisering van data wat van beide die Tswana en saamgestelde rasse ingesamel is, om die invloed van nie-genetiese faktore op die groei eienskappe te bepaal om ten einde aanpassingsfaktore vir die effek van geslag van die kalf en ouderdom van die moederdier te ontwikkel. ʼn Tweede doelwit was die bepaling van genetiese parameters (oorerflikhede en genetiese korrelasies) vir die gebruik in toekomstige genetiese evaluering van beide rasse. Data is vanaf 1988 tot 2006 ingesamel. ʼn Totaal van 2 257 waarnemings vir die saamgestelde ras en 5 923 waarnemings vir die Tswana ras is ontleed. Groei eienskappe wat in die studie ondersoek is, het geboortegewig (BW), speengewig (WW), voorspeen gemiddelde daaglikse toename (ADG1), 18-maand gewig (18MW) en naspeense gemiddelde daaglikse toename (ADG2) ingesluit. Studie een het aangedui dat nie-genetiese effekte van die ras van die kalf, die geslag van die kalf, maand en jaar van geboorte, vorige dragtigheidsstatus, koei se gewig met geboorte van kalf, ouderdom van die moederdier en die speenouderdom van die kalf het ʼn betekenisvolle invloed op BW, WW, 18MW, ADG1 en ADG2 van beide rasse gehad. Die saamgestelde ras het hoër waardes vir BW, ADG1 en WW gehad, terwyl die Tswana ras hoër waardes vir ADG2 en 18MW geopenbaar het. Voorspeense groeitempo het toegeneem met ʼn toename in die ouderdom van die moederdier, met ʼn piek in volwasse (d.i. 5-12 jaar ouderdom) moeders en ʼn afname in koeie 13 jaar en ouer. Omgekeerd het naspeen groeitempo afgeneem met ʼn toename in die ouderdom van die moederdier en weer begin toeneem vir ou (d.i. 13 jaar en ouer) koeie. Geboortegewig het toegeneem met die verloop van die kalfseisoen, terwyl ʼn afname in WW vir dieselfde periode aangeteken is. Verse het, wanneer hulle met volwasse koeie vergelyk is, het geboorte aan ligter kalwers gegee. Die saamgestelde ras kan dus oorweeg word vir die produksie van speenkalwers onder kommersiële intensiewe toestande, terwyl die Tswana ras, op grond van sy beter aanpassing by ekstensiewe omstandighede waar die moederlike invloed nie voorkom nie, vir produksie onder ekstensiewe omstandighede gebruik kan word. In studie 2 is die additiewe korreksie faktore vir die invloed van geslag van die kalf en moederouderdom op BW en WW apart vir die twee rasse bestudeer. Die geslag van die kalf x ouderdom van die moederdier interaksie was nie betekenisvol vir enige van die rasse nie. Dus kan geen aanpassing vir die ouderdom van die moeder binne geslagte vir enige van die twee rasse gemaak word nie. Die kleinste kwadraat gemiddeldes metode is gebruik om die ouderdomsgroepe en aanpassingsfaktore te bepaal. Die drie ouderdomsgroepe was jong (d.i. 4 jaar en jonger) koeie, volwasse (d.i. 5-12 jaar ouderdom) en ouer (d.i. 13 jaar en ouer) koeie. Daar is gevind dat manlike kalwers swaarders as hulle vroulike eweknieë is. Die aanpassingswaarde vir die geslag van die kalf vir BW en WW was 2.75 kg en 8.21 kg in die Tswana en 2.84 kg en 10.11kg vir die saamgestelde ras. Geboortegewig en WW het toegeneem met ʼn toename in die ouderdom van die moeder. Dit het ʼn maksimum bereik in volwasse koeie en afgeneem vir koeie ouer as 13 jaar. Die aanpassingsfaktore vir die ouderdom van die moederdier vir BW in die 3, 4 and 13+ jarige ouderdomsgroepe vir die Tswana ras was onderskeidelik 1.74 kg, 0.96 kg en 1.87 kg. Die ooreenstemmende waardes vir die saamgestelde ras was onderskeidelik 2.28 kg, 0.94 kg en 2.06 kg. Aanpassingsfaktore vir WW vir die Tswana ras was 10.36 kg en 5.46 kg vir onderskeidelik die 3-4 jaar en 13+ jaar en ouer ouderdomsgroepe. Aanpassingsfaktore vir WW in die Composite ras was 13.84 kg, 3.20 kg en 9.58 kg vir onderskeidelik die 3 jaar, 4 jaar en 13 jaar en ouer ouderdomsgroepe. Verskille in die onderskeie parameters vir die twee rasse beklemtoon die noodsaaklikheid vir die berekening en toepassing van die onderskeie aanpassingfaktore vir en binne elke ras. Studie 3 het die bepaling van die genetiese parameters vir BW, WW, ADG1, 18MW en ADG2 behels. Enkel- en multivariaat analises is gebruik vir die skatting van die (ko)variansie komponente deur ʼn direkte diermodel (AM) en ʼn dier-maternale model (AMM) vir die twee rasse te pas. Direkte oorerflikhede vir BW, WW, ADG1, 18MW en ADG2 vir die Tswana ras was onderskeidelik 0.45, 0.32, 0.37, 0.31 en 0.31, vir ʼn enkelvariaat AM analise. Die pas van ʼn AMM het direkte oorerflikhede van 0.31, 0.20 en 0.16 vir onderskeidelik BW, WW and ADG1 gegee, terwyl die maternale oorerflikhede onderskeidelik 0.11, 0.15 en 0.21 was. Vir die saamgestelde ras was die direkte oorerflikhede vir BW, WW en ADG1 onderskeidelik 0.58, 0.32 en 0.30 vir die enkelvariaat AM analise. Verdeling (partisie) van die AMM het direkte oorerflikhede vir BW, WW en ADG1 van onderskeidelik 0.55, 0.17 en 0.14 gegee, terwyl die ooreenstemmende maternale effekte onderskeidelik 0.09, 0.15 en 0.15 was. Die genetiese korrelasies tussen die drekte en maternale effekte was positief en tussen 0.20 en 0.89. Met die multivariaat analise en die pas van die AM, is direkte oorerflikhede van 0.45, 0.37, 0.34, 0.39 en 0.31 vir onderskeidelik BW, WW, ADG1, 18MW en ADG2, vir die Tswana ras bereken. Genetiese korrelasies tussen die groei eienskappe het gewissel tussen 0.16 tot 0.97. Direkte (en maternale) oorerflikhede vir BW, WW en ADG1 was onderskeidelik 0.31(0.11), 0.19(0.15) en 0.14(0.17), vir die Tswana ras. Korrelasies tussen die direkte oorerflikhede vir BW, WW en ADG1 het gewissel tussen 0.45 en 0.95, terwyl die maternale effekte tussen 0.12 en 0.99 gewissel het. Die grootte van die oorerflikhede dui op die moontlikheid van genetiese vordering wat deur seleksie in beide rasse gemaak kan word. Seleksie op grond van WW blyk die mees gepaste wyse te wees waarmee genetiese vordering binne die Tswana ras gemaak kan word, sonder enige langtermyn nadelige effekte.

Daugelis kačių veislių yra imlios įvairioms ligoms ir patologijoms. Kai kurios iš šių mutacijų nėra pavojingos kačių sveikatai, kitos sukelia sunkias ligas, trečios yra veislės požymis. Genetinės ligos ir ydos skirstomos į fenokopijas, dizgenetines anomalijas ir įgimtas ligas ir ydas. Dažniausiai paplitusios genetinės ligos tarp atskirų kačių veislių yra šios: hipertrofinė kardiomiopatija (HCM), inkstų policistozė (PKD), progresuojanti tinklainės atrofija (rdAc-PRA), gangliozidozė (GM1, GM2), piruvato kinazės trūkumas (PK), glikogeno kaupimosi liga IV tipo (GSD-IV), stuburo raumenų atrofija (SMA). Ydos: plokščios krūtinės kačiukų sindromas, bambinė išvarža, įgimta veido kaulų anomalija, Vandenburgo sindromas, polidaktilija, ektrodaktilija, sindaktilija, nesuaugęs kietasis gomurys, kriptorchizmas. Genetiniam tyrimui atlikti imamas mėginys iš katės skruosto vidinės pusės (reikalingos žando ląstelės) tamponėlio pagalba. Paėmus mėginį, tamponai įdedami į specialų voką su užpildytų blanku ir siunčiami paštu į laboratoriją. Laboratorijoje, atliekant genetinius tyrimus, naudojama DNR polimerazės grandinės reakcija bei genų sukibimo metodas. Genetinį tyrimą galima atlikti bet kurio amžiaus gyvūnui. Nustatėme, kad Lietuvoje per 2009-2013 metus mano tirtose veterinarijos klinikose daugiausia diagnozuota inkstų policistozės, kriptorchizmo, aklumo, bambinės išvaržos ir kurtumo atvejų. Iš kačių genetinių ligų Lietuvoje dažniausiai pasitaiko tik inkstų policistozė ir hipertrofinė... [toliau žr. visą tekstą] / Many cat breeds are susceptible to various diseases and pathologies. Some of these mutations are not dangerous to the health of cats, others cause severe diseases, third ones, are the feature of breed. Genetic diseases and vices are divided into phenocopies, dysgenetic anomalies, and congenital diseases and defects. Most prevalent genetic diseases among different cat breeds are: hipertrophic cardiomyopathy (HCM), polycystic kidney disease (PKD), progressive retinal atrophy (rdAc-PRA), gangliosidosis (GM1, GM2), pyruvatkinase deficiency (PK), glycogen storage disease IV type (GSD-IV), spinal muscular atrophy (SMA). Vices: flat chest kitten syndrome, umbilical hernia, congenital abnormality of the facial bones, Vandenburg‘s syndrome, polydactyly, ectrodactyly, syndactyly, cleft hard palate, cryptorchidism. Use brushes to collected cells from inside the cheek (buccal cells). Place all sample containing sample brushes and completed submission forms into a suitable envelope and male to laboratory. During the genetic research, laboratories are refering to the DNA polymerase chain reaction and gene bonding method. Genetic testing can be performed to the animal of any age. We found out, that in Lithuania in the years of 2009-2013, in veterinary clinics, where I did my research, the following diseases were diagnosed the most: kidney polycystosis, cryptorchidism, blindness, deafness and umbilical hernia. Among feline genetic diseases, only kidney polycystosis and hypertrophic... [to full text]

Institute for Rural Development / MRDV

Thesis (MScAgric) -- University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Experiment 1: Two studies were conducted to research the effect of divergent selection for multiple rearing ability on carcass weight, mutton production, meat quality and carcass characteristics of similar-aged Merino sheep. Data of 114 19-month-old Merino sheep, 40 ewes and 74 rams were used in this study. The study was done in two parts over 2 years. Only rams (52) were slaughtered over a two-week period in study A. Twenty-two rams and 40 ewes were slaughtered over a three-week period in study B. The sheep were descended from two selection lines that have been divergently selected for maternal multiple rearing ability since 1986. In brief, ewe and ram progeny of ewes rearing more than one lamb per joining (i.e. that reared twins at least once) were preferred as replacements in the high (H) line. Descendants of ewes that reared fewer than one lamb per joining (i.e. that were barren or lost all lambs born at least once) were preferred as replacements in the low (L) line. In study A the mean (±SE) slaughter weight of H line rams . were 12% heavier (P<O.OI) than that of L line contemporaries. A corresponding difference (P<O.OI) of 13% was found for carcass weight Adjustment for the higher live weight by analysis of covariance ofH line rams resulted in most of the line differences being eliminated (P>0.05). The difference between the weight of the loin retail cut remained significant (P<O.OI) in favour of the H line (1.64±0.04 vs. 1.37±0.08 kg, respectively). Skin weight (3.93±0.15 vs. 3.34±0.07 kg respectively; P<O.OI) and skin thickness (2.28±0.1l vs. 1.97±0.06 mm respectively; P<0.05) were greater in L line rams than in H line contemporaries. Rams in the L line also had heavier (P<0.05) trotters than the H line (l.05±0.03 vs. 0.96±0.02 kg respectively). In study B there were no interaction between line and sex and the data were pooled to present the main affects of sex and line. In study B the mean (±SE) slaughter weight of H line animals was 7% heavier (P=0.05) than that of L line contemporaries (44.02±0. 7 vs. 41.2±1.2 kg, respectively). A corresponding difference (P<0.05) of 11% was found for carcass weight between the two lines (pooled sexes) (l6.1±0.3 vs. 14.4±0.5 kg, respectively). There was no difference in the tenderness of the meat between the two selection lines but L line animals tended (P<0.16) to have more tender meat than H line contemporaries. Adjustment for the higher live weight of H line animals by analysis of covariance resulted in most of the line differences being eliminated (P>0.05). Hindquarter weight still remained significantly (P<O.OI) in favour of the H line after correction for live weight. Meat of L line animals was healthier based on their PUF A/SF A ratio. Experiment 2: This experiment was conducted to quantify the effect (noted in the first experiment) of selection for and against multiple rearing ability in Merino sheep on m. longissimus dorsi postmortem pH profiles. Data of 20 Merino sheep (10 rams and 10 ewes) were used. The sheep were slaughtered at a commercial abattoir. After slaughter pH was measured at 45 min, 2, 4, 8, 10, 12, 16, 20, 24, 33 and 48 h post slaughter, respectively. The pH was measured on the right side of each carcass in the m. longissimus dorsi between the 1st and the 6th lumbar vertebrae. The m. longissimus dorsi between the 1st and the 6th lumbar vertebrae of the left side was used for meat quality analysis. The initial pH of H line animals tended to be higher than that of L line contemporaries. At 48 h post-slaughter the pH of L line was higher (P<0.05) compared to that of H line animals. The meat of H line animals was tougher (99.79±3.58 vs. 88.32±3.38, P<0.05) than that of L line contemporaries, but there were no differences in the other meat quality characteristics. A higher initial pH (found in the first experiment, with a similar tendency in the second experiment) could indicate a lower susceptibility to stress in the H line. Experiment 3: An experiment was done to compare the meat-production potential between Merino and South African Mutton Merino (SAMM) ewes with increasing age. Slaughter data of . 653 Merino and SAMM ewes were used. Animals were slaughtered between 220 and 2719 days of age, which encompassed a range of slaughter weights from 27 to 100 kg. The ewes were differentiated according to age, 219 ewes being younger than 600 days and 416 being older than 600 days at slaughter. Young SAMM ewes had 10% heavier carcass weights than young Merino ewes and the difference was 47% between mature ewes. Mean maximum carcass weights of 33.44 and 22.65 kg were derived for the SAMM and Merino, at respective age of 2100 and 1900 days. SAMM ewes had a 47% thicker fat depth. Although Merinos were earlier maturing than the SAMM ewes, the latter breed had more subcutaneous fat at the mature stage. Experiment 4: The fourth experiment examined the effect of breed and sex on the carcass composition, yield of retail cuts, fat depth and chemical composition of meat from 35 South African Mutton Merino (SAMM) (17 rams and 18 ewes) and 61 Dormer (21 rams and 40 ewes) sheep. As there was no breed x sex interaction, the data were pooled to present the main effects of breed and sex. There were no differences in slaughter and carcass weight between Dormer and SAMM sheep. Dormers' had more fat (kidney, back fat depth) than SAMM sheep. The eye-muscle area of the Dormers' was 13% larger than that of the SAMM sheep. Rams were heavier (64.86±0.85 vs. 44.55±0.74 kg) than the ewes at slaughter. All the traits that were recorded, were heavier or higher in rams (P<0.05). After adjustment for higher live weight of the rams, the proportion of neck retail cut from the rams was higher than that from ewes and the proportion of hindquarter weight from the ewes was higher (P<0.05) than that from rams. After adjustment for the higher live weight of the rams, the moisture (75.35±0.37 and 73.35±0.37%) and lipid (2.68±0.33 and 3.80±0.33%) contents differed significantly (P<0.05) between the rams and ewes, respectively. With the significantly higher SFA value of the SAMM sheep and higher MUF A value of the Dormer sheep, meat from Dormer sheep could be regarded as healthier from a human prospective than that from SAMM sheep. Experiment 5: A study was done to test an ultrasound scanner (used on pigs) for the prediction of subcutaneous backfat and m. longissimus dorsi depth on Merino (52 rams), SA Mutton Merino (17 rams and 18 ewes) and Dormer (21 rams and 40 ewes) sheep. The sheep were scanned with an ultrasound scanner to predict the backfat and eye-muscle depth on the live animal. All animals were slaughtered to measure the true values of the fat depth and eye-muscle depth (25 and 45mm from the midline at the 13th rib). Overall regression equations over breeds (SAMM and Dormer, pooled breeds), and lines (H and L line Merinos, pooled lines) were obtained. Compared to previous research, the correlations between scanned values and true values were comparatively low (r = 0.07 - 0.25). Evidence from the literature suggested higher correlations of r = 0.53 - 0.56. Higher correlations could be achieved in older and fatter animals. The fact that the operator had no experience of scanning sheep could also have contributed to the low correlations. / AFRIKAANSE OPSOMMING: Eksperiment 1: Twee studies is gedoen om te kyk na die invloed van seleksie vir meerling grootmaakvermoe by Merino's op karkas-, vleiseienskappe en vleiskwaliteit is. Data van 114 19 maand oue Merino skaap, 40 ooie en 74 ramme is in die studie gebruik. Die studie is gedoen in twee dele oar 'n tydperk van twee jaar. Slegs ramme (52) is geslag oor 'n tydperk van twee weke in studie A. Twee en twintig ramme en 40 ooie is in studie B geslag oor 'n pericde van drie weke. Merino-ooie en -ramme afkomstig van 'n hoe (Il-lyn) en lae (L-lyn) lyn geselekteer vir rneerling grootmaakverrnoe is gebruik in 'n studie wat oor twee jaar uitgevoer is. Die twee lyne is intensief geselekteer vir en teen meerling grootmaakverrnoe vanaf 1986. Ram- en ooi-nageslag wat afkomstig is van ooie wat een of meer keer tweelinge in haar lewe per lam kans groot gemaak het is gebruik vir die H-lyn, terwyl ram en ooi nageslag afkomstig van ooie wat een of minder as een lam per lamkans groot gemaak het is gebruik vir die L-Iyn. In studie A is 52 rarnme (42 H-Iyn en 10 Llyn) geslag en slag- en karkaseienskappe is bestudeer. In ondersoek B is 22 ramme (16 l-l-lyn en 6 L-lyn) en 40 coie (34 H-Iyn en 7 L-Iyn) gebruik. Slag-, karkas- en vleiseienskappe is bestudeer. In ondersoek A is gevind dat die slagmassa van die Il-Iyn ramme 12% hcer en die karkasmassa 13% hcer is as die van die L-lyn ramme. Na kovariansie ontleding van die swaarder slagmassa van die H-Iyn diere, was die pote (1.05±0.03 vs. 0.96±0.02 kg; P<0.05) en velie swazrder (3.93±0.15 vs. 3.34±0.07 kg; P<O.Ol) en die velle dikker (2.28±0.11 vs. 1.97±0.06 mm; P<0.05) by L-Iyn diere as by H-lyn diere. Die groothandel lende snit van die H-Iyn diere was swaarder (1.64±0.04 vs. 1.37±0.08 kg; P<0.05) as die van L-Iyn diere. By studie B was daar geen interaksie tussen lyn en geslag nie, dus is die data verpoel om die betekenisvolheid van die hoofeffekte van lyn en geslag weer te gee. 'n Sewe persent hoer slagmassa is by H-Iyn diere waargeneem (44.02±0.7 vs. 41.20± 1.2 kg; P<0.05). 'n Ooreenstemmende verskil van (P<0.05) 11% is gevind in karkas massa tussen die twee lyne (16.1±0.3 vs. 14.4±0.5 kg). Daar was geen veskil in taaiheid van die vleis nie, maar diere van die H lyn se vleis het geneig (P<0.06) om taaier te wees. Na die kovariansie ontleding met massa as kovariant was die boude (P<O.OI) van die H-lyn diere en die lende (P<O.OI) groothandel snit van die ooie swaarder, verder was die verskille dieselfde as in ondersoek A Die vetsuurresultate toon dat net by die verhouding tussen die poli-onversadigde en vesadigde vetsure (PUF A/SF A) 'n verskil tussen die Iyne was. Die vetsuur resultate dui daarop dat die Llyn diere gesonder vleis vir menslike voeding het as die van die H Iyn diere. Eksperiment 2: In 'n tweede eksperiment is gekyk wat die invloed van seleksie vir meerling grootmaakvermoe by Merino skape op post mortem m. longissimus dorsi pH profiele is. Daar is gebruik gemaak van 20 Merino skape (10 ooie en 10 ramme), 10 H lyn en 10 Llyn diere. Die skape is geslag by 'n kornrnersiele abattoir. Die pH metings is geneem, 45 min, 2, 4, 6, 8, 10. 12, 16, 20, 24, 33 en 48 uur na slag. Die pH is geneem in die m. longissimus dorsi van die regter sy tussen die 1ste en 6de lumblale werwels. Die linker kant is gebruik vir vleiskwaliteits toetse Die pH lesing van H lyn diere wat 45 min na slagting geneem is het hoer geneig as in Llyn, terwyl pH lesings van die Llyn diere 48 h na slagting hoer was. Die vleis van die H lyn diere was taaier (99.79±3.58 vs. 88.32±3.38; P<0.05) as die van die Llyn diere, maar daar was geen verskille in die ander vleiskwaliteits toetse nie. Die hoe begin pH kan daarop dui dat die H lyn skape minder spanning voor slag ervaar he! Eksperiment 3: Die invloed van ouderdom op vleis produksie potensiaal, slag en karkasmassa en vetdikte by Suid Afrikaanse Vleis Merino (SAVM) en Merino ooie is ondersoek. Data van 635 Merino en SAVM ooie is gebruik. Die ooie was tussen 220 en 2719 dae oud met slagting en slagmassas wat gewissel het tussen 27 en 100 kg. Die ooie is opgedeel ten opsigte van ouderdorn. Die jong groep was ooie wat jonger as 600 dae oud was en die die res was bestempel as die ou groep. Die karkas massa van die jong SAVM ooie was 10% hcer as die van die Merino ooie en by die ou groep was die verskil 47% Ouer SAVM ooie het 52% dikker vet as die Merino ooie gehad. Merino ooie het 'n maksimum karkas massa van 22.65 kg op 'n ouderdom van 1900 dae gehad terwyl SAVM ooie 'n maksimum karkas massa van 33.44 kg op 'n ouderdom van 2100 dae gehad he! Al is die Merino 'n vroer ryp skaap as die SAVM, het die SAVM meer vet as volwasse dier. Eksperiment 4: In die experiment is gekyk na die effek van ras en geslag op slagmassa, karkasmassa, vleiseienskappe asook chemiese en vetsuur samestelling van die vleis van SAVM en Dormer skape. Slagdata van 61 Dormers' (21 ramme en 40 ooie) en 35 SAVM's (17 ramme en 18 ooie) is gebruik, Daar was geen interaksie tussen ras en geslag nie en dus is die data verpoel om die invloed van die hoof effekte (ras en geslag) te toets. Geen verskille is in die slagmassa tussen die Dormers en SAVM gevind nie. Die vet (onderhuids en niervet) van die Dormers was meer en die oogspier oppervlakte was 13% groter as die van SAVM skape. Ramme was swaarder (64.86±0.85 vs. 44.55±0.74 kg) as die ooie met slag. Na kovariansie ontleding van swaarder slagmassa van die ramme was die groothandel nek snit van die ramme swaarder (P<0.05) as die van die ooie en die boude van die ooie swaarder (P<O.Ol) in vergelyking met die van die ramme. Die voginhoud van vleis vanaf ramme was hoer (77.35±0.37 vs 75.35±0.37) as die van die coie. Ooie het 'n hcer persentasie vet in die vleis van die 11113de ribsnit gehad (2.68±0.33 vs. 3.80±0.33 %) Volgens die vetsuur analises het SAVM diere 'n hoer persentasie versadigde vetsure en die Dormers 'n groter persentasie mono-onversadigde vetsure gehad. Dit kan 'n aanduiding wees dat vleis vanaf Dormer skape gesonder is vir menslike gebruik. Eksperiment 5: Hierdie studie is gedoen om 'n ultraklank apparaat (gebruik by varke) te toets vir voorspelling van onderhuidse vet en oogspierdiepte by skape. Daar is gebruik gemaak van 52 Merino ramme (42 van die H-lyn en 10 van die Llyn), 61 Dormer skape (21 ramme en 40 ooie) en 35 SAVM skape (17 ramme en 18 ooie). Die vetdikte en oogspierdiepte op die lewende diere is bepaal met 'n ultraklank apparaat, waarna die diere geslag is en die werklike waardes direk op die koue karkas gemeet is. Regressie vergelykings is opgestel om korrelasies tussen ultraklank waardes en werklike waardes te kry. In hierdie proef was die korrelasies tussen geskatte en werklike waardes swak (r = 0.07-0.25). Beter korrelasies is egter weI deur ander navorsers gekry (r = 0.53- 0.56) Beter korrelasies kan in ouer en vetter diere verkry word. Die feit dat die operateur nie baie ondervinding met die skandering van skape gehad het nie kon bydrae tot die swak korrelasies.