The Suitability of test-day models for genetic evaluation of dairy cattle in South Africa

In this study the possibility to change to test-day models for genetic evaluation of production traits and somatic cell score of South African dairy breeds (i.e. Ayrshires, Guernseys, Holsteins and Jerseys) was investigated. Fixed Regression BLUP Animal Models were therefore developed, using test-day records of the first three lactations as repeated measures of the same trait. Milk, butterfat and protein yields were included in multitrait evaluations. A permanent environmental effect was fitted across lactations. Heritabilities estimated were comparable with other yield and somatic cell score estimates obtained from test-day models. Breeding values of qualifying sires were presented to INTERBULL for participation in the March 2005 test-runs. Genetic correlations between South Africa and other participating countries compared well with those amongst other countries, participating in these international evaluations. Trend validation tests were successful for all traits and breeds except for somatic cell score of the Guernsey breed, due to insufficient data for this trait. South Africa is now participating in routine INTERBULL evaluations in order to obtain MACE (multiple across country evaluation) breeding values, using this methodology. Further refinement of the model was tested, i.e. inclusion of a fixed calving year effect in the model and pre-adjusting records for heterogeneous variances due to days in milk and parity. This was investigated for the Jersey breed and recommended for implementation in the other South African breeds. South Africa’s methodology is now more comparable to that of the leading dairy producing countries of the world.Thesis (PhD (Animal and Wildlife Sciences))--University of Pretoria, 2007.Animal and Wildlife Sciencesunrestricte

Genetic analysis of pre-weaning survival and inbreeding in the Boxer dog breed of South Africa

Members of the Federation of Boxer Clubs in Southern Africa (FBCSA) have participated in official recording for many years. The aim of the study was to estimate genetic parameters and trends for pre-weaning survival and to assess inbreeding in the South African Boxer, based on performance and pedigree data. Fitness records were included from 2138 litters recorded between 1988 and 2012 and pedigree information of 32 029 Boxer dogs recorded from 1950 to 2012. The average litter size was 6.14 ± 2.43. More male puppies were born per litter (3.23 ± 1.79) than female puppies (2.91 ± 1.72), with an increase in the proportion of males in larger litter sizes. Heritability values of 0.23 ± 0.08 and 0.25 ± 0.08 were estimated for litter size (LS) and number of puppies alive at two weeks after birth (NA), respectively. Litters larger than five tended to have more puppies born dead or with low survivability. Number of puppies born dead or that died within two weeks after birth increased from 0.43/litter at first parity to 0.82/litter at fifth parity, with a substantial increase of 2.25/litter with low survivability at seventh parity. Average inbreeding levels of the Boxer breed were above 10%, with an inbreeding rate of 0.14%/year since 1982. These results indicate that FBCSA should focus on lowering the levels of inbreeding by avoiding mating closely related animals. The complete recording of fitness traits is encouraged for effective genetic management of the breed.http://www.sasas.co.zaam201

Short communication: Analysis of inbreeding of the South African Dairy Swiss breed

In South Africa, the Dairy Swiss breed, which originated in Switzerland, consists of 27 breeders and 1135 breeding cows. Pedigree information on the breed was analysed to determine its effective population size (Ne) and rate of inbreeding. The rate of inbreeding was 0.08% per year and 0.38% per generation. It was estimated that in 2008, over 90% of the animals were inbred. This is within the acceptable recommendation for an effective population size of 50 - 100, with an Ne value of 89. However, the high percentage of inbred animals may start to have a detrimental impact on the effective population size and breeders need to exercise caution in their breeding decisions.http://www.sasas.co.zaam201