Comparison of productive and reproductive efficiency of Afrino, Dorper and Merino sheep in the False Upper Karoo

The productive and reproductive performance of, as well as income generated by Afrino, Dorper and Merino sheep at two localities in the False Upper Karoo region were evaluated. A total of 1242 ewe reproductive records was available, while data of respectively 772 and 405 lambs were analysed for the growth traits and slaughter traits. Percentage of lambs weaned per ewe in the flock was 132.0%, 100.0% and 93.7% for Afrino, Dorper and Merino ewes at Grootvlei, respectively. Corresponding values for Twistkraal were 153.3%, 114.7% and 96.4%, respectively. Body weights of 52.3 ± 1.4 kg, 56.6 ± 1.4 kg and 43.4 ± 1.4 kg were recorded for Afrino, Dorper and Merino ewes, respectively. Merino ewes produced on average 1.3 kg more clean wool, of a 0.6 μm stronger diameter than Afrino ewes. At each locality Dorper lambs were the heaviest at weaning, followed by Afrino and then by the Merino lambs. Dorper lambs were slaughtered earlier than Afrino lambs, with Merino lambs taking the longest interval to reach slaughter weight. A definite seasonal effect was also evident, where the autumn-born lambs reached slaughter weight earlier than spring-born lambs in all breeds. With the current wool and mutton prices, Afrino sheep had the highest gross income per ewe, followed by Merino and Dorper ewes respectively. However, Merino sheep had the highest gross income per hectare at both localities, followed by Afrino and then Dorper sheep. The combination of low ewe body weights, high wool production and a relatively high reproductive rate, resulted in Merino sheep generating the highest income per hectare, compared to Afrino and Dorper sheep. Reproductive rate, mature body weight and fibre production are the primary factors determining profitability of a specific sheep enterprise. These parameters should thus be considered when changing from one breed or commodity to another. Keywords: Body weight; wool production; slaughter traits; income South African Journal of Animal Sciences Vol. 35 (2) 2005: pp.98-10

Genetic parameters for growth, reproductive and maternal traits in a multibreed meat sheep population

The genetic parameters for growth, reproductive and maternal traits in a multibreed meat sheep population were estimated by applying the Average Information Restricted Maximum Likelihood method to an animal model. Data from a flock supported by the Programa de Melhoramento Genético de Caprinos e Ovinos de Corte (GENECOC) were used. The traits studied included birth weight (BW), weaning weight (WW), slaughter weight (SW), yearling weight (YW), weight gain from birth to weaning (GBW), weight gain from weaning to slaughter (GWS), weight gain from weaning to yearling (GWY), age at first lambing (AFL), lambing interval (LI), gestation length (GL), lambing date (LD - number of days between the start of breeding season and lambing), litter weight at birth (LWB) and litter weight at weaning (LWW). The direct heritabilities were 0.35, 0.81, 0.65, 0.49, 0.20, 0.15 and 0.39 for BW, WW, SW, YW, GBW, GWS and GWY, respectively, and 0.04, 0.06, 0.10, 0.05, 0.15 and 0.11 for AFL, LI, GL, LD, LWB and LWW, respectively. Positive genetic correlations were observed among body weights. In contrast, there was a negative genetic correlation between GBW and GWS (-0.49) and GBW and GWY (-0.56). Positive genetic correlations were observed between AFL and LI, LI and GL, and LWB and LWW. These results indicate a strong maternal influence in this herd and the presence of sufficient genetic variation to allow mass selection for growth traits. Additive effects were of little importance for reproductive traits, and other strategies are necessary to improve the performance of these animals

Mapping quantitative trait loci (QTL) in sheep. I. A new male framework linkage map and QTL for growth rate and body weight

A male sheep linkage map comprising 191 microsatellites was generated from a single family of 510 Awassi-Merino backcross progeny. Except for ovine chromosomes 1, 2, 10 and 17, all other chromosomes yielded a LOD score difference greater than 3.0 between the best and second-best map order. The map is on average 11% longer than the Sheep Linkage Map v4.7 male-specific map. This map was employed in quantitative trait loci (QTL) analyses on body-weight and growth-rate traits between birth and 98 weeks of age. A custom maximum likelihood program was developed to map QTL in half-sib families for non-inbred strains (QTL-MLE) and is freely available on request. The new analysis package offers the advantage of enabling QTL × fixed effect interactions to be included in the model. Fifty-four putative QTL were identified on nine chromosomes. Significant QTL with sex-specific effects (i.e. QTL × sex interaction) in the range of 0.4 to 0.7 SD were found on ovine chromosomes 1, 3, 6, 11, 21, 23, 24 and 26

Vitamin D Deficiency and Its Health Consequences in Africa

Africa is heterogeneous in latitude, geography, climate, food availability, religious and cultural practices, and skin pigmentation. It is expected, therefore, that prevalence of vitamin D deficiency varies widely, in line with influences on skin exposure to UVB sunshine. Furthermore, low calcium intakes and heavy burden of infectious disease common in many countries may increase vitamin D utilization and turnover. Studies of plasma 25OHD concentration indicate a spectrum from clinical deficiency to values at the high end of the physiological range; however, data are limited. Representative studies of status in different countries, using comparable analytical techniques, and of relationships between vitamin D status and risk of infectious and chronic diseases relevant to the African context are needed. Public health measures to secure vitamin D adequacy cannot encompass the whole continent and need to be developed locally

Genetic analysis of body weight in South African Angora kids and young goats

The data used for this study consisted of 27 485 kid records, the progeny of 599 sires and 10 077 dams, and were collected on the 2000- to 2009-born kids of 11 Angora goat studs. Variance and covariance components and ratios pertaining to direct additive genetic variation, maternal additive genetic variation, maternal permanent environmental variation, and the relationship between direct and maternal effects for birth weight (BW; kg), weaning weight (WW; kg) and body weight at 8, 12 and 16 months (W8, W12 and W16; kg) were estimated with the ASReml program. Direct additive heritability estimates of 0.22, 0.20, 0.12, 0.34 and 0.58 were obtained for BW, WW, W8, W12 and W16, respectively. Maternal heritabilities were 0.10, 0.09, 0.03 and 0.06 for BW, WW, W8 and W12, respectively, while maternal environmental effects of 0.13, 0.11, 0.06 and 0.04 were estimated for the latter traits, respectively. An unfavourable correlation of –0.38 was obtained between direct and maternal genetic effects for BW. Low to medium positive direct genetic correlations were estimated between birth weight and body weights recorded at a later stage in life. High positive direct genetic correlations were estimated among WW, W8, W12 and W16. The maternal genetic correlations obtained between birth weight and the other body weights were medium to high. Phenotypic correlations among the traits ranged from low to high. Genetic trends of body weight at different ages indicate that although not many breeders use objective measurement as a selection tool, body weight increased slightly in the 11 studs over the 10-year study period. Since reproduction and body weight should be included in a selection programme for Angora goats, the relationship between the direct and maternal additive effects should be clarified. The importance of a sufficiently structured and related pedigree, especially on the part of the dams and maternal grand dams, has been highlighted in this study. As this is one of the constraints of this data set, data collection in the Angora goat industry should continue until a suitably structured data set has been built up that could be used to estimate multi-trait breeding values for the industry.Keywords: Birth weight, genetic parameters, maternal effects, weaning weigh

Factors affecting pre-weaning kid mortality in South African Angora goats

The data used for this study were collected in 12 different Angora goat studs from 2000 to 2004. Data collected on 17534 kids born alive in the different studs were included in the analyses. Average pre-weaning mortality rate was 11.5% and ranged from 8.6% to 16.5% (of the 17534 kids born alive, 2018 kids died between birth and weaning at four months of age). Mortality rate in male kids was higher than that recorded for female kids (11.9% vs. 11.1%). When comparing the management systems followed from mating up until weaning in the different studs with the corresponding pre-weaning mortality rates, it is obvious that there was no discernible trend. Of the 2018 deaths recorded, the probable cause for only 601 (29.8%) deaths was known. The most important problems were predators, small, unthrifty kids who needed help with suckling, does having little or no milk and does abandoning their kids. When combining the latter three causes with udder problems (3.5%), 35.7% of pre-weaning mortalities was due to these causes. Birth weight and sex of the kid had a significant influence on pre-weaning mortality rate. Single-born kids had the lowest mortality rate (10%), followed by twin-born (13%) and triplet-born (22%) kids. Despite large differences in mortality rate recorded between sires within flocks, a heritability of 0.04 ± 0.01 was estimated for pre-weaning mortality rate. This low overall heritability could be attributed to the fact that causes of mortality differed considerably among kids and many of these causes may have no genetic background.Keywords: Rearing environment, reproduction, weaning, birth weigh

Influence of body weight, age and management system on reproduction of South African Angora goat does

The effect of doe age, body weight and different management systems, as practiced in various Angora goat studs, on reproductive performance of does was investigated. The data used were collected from 2000 to 2004 on 12 Angora goat studs kept under different management systems. The data set analysed for this study contained data of 6271 does, each with a varying number of kidding opportunities. This amounted to 14644 doe records where each record included body weight before mating, body weight at scanning (ultrasound scanning for pregnancy diagnosis) and all reproductive performance data. There was a wide range pertaining to reproductive performance among the various studs. Apart from a high kid mortality rate, which is regarded by breeders as the most important factor contributing to low weaning percentages, nearly 20% of the does did not conceive or lost their foetuses before birth. Body weight of does before mating ranged from 13.0 kg to 59.6 kg (average = 34.6 kg) among animals, while body weight at scanning ranged from 18.0 kg to 67.0 kg (average = 38.6 kg). All reproductive parameters recorded had a typical inverted U-shaped relationship with age of dam, where the 2- and 3-year-old does and does older than 9 years of age fared significantly worse than the 4- to 9-year-old does. Management system had a significant influence on reproductive performance of does in the different studs. Higher reproductive rates were recorded under those management systems where additional or supplementary feeding at various stages of the reproductive cycle were supplied. Body weights before mating and at scanning had significant positive relationships with reproduction. For every kilogram increase in body weight before mating, 0.0237 and 0.0218 more kids will be born and weaned, respectively. Body weights before mating of young does that were kept on pastures until 18 months of age were higher than those of maiden does in the other management systems, resulting inhigher reproductive rates. Number of kids scanned, born and weaned per maiden doe at first kidding increased with an increase in body weight at first mating. From the results it is evident that body weight, age of the doe and management system all have a significant effect on the reproduction of Angora goats.Keywords: Nutrition, mating, pregnancy, kidding performanc

Studies on small ruminant breeds with inherent differences in fibre production and ewe productivity 1. Relationship between ewe productivity and wool production potential

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Genetic and environmental parameters of milk production and milk composition in South African Merinos

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