Feeding ecology of four livestock species under different management in a semi-arid pastoral system in South Africa

The Leliefontein communal area in Namaqualand is grazed by mixed species herds that have multiple benefits for pastoralists. This study assessed how the management (herding and free-ranging) of different livestock herds affects their feeding ecology during the wet and dry seasons in a semi-arid shrubland. By using direct observations of livestock grazing in the field, we established their habitat preferences, diet selection and resources overlap. Results indicate that all free-ranging livestock can be considered grazers with cattle being selective. When sheep are herded, they tend to be more generalist feeders and herded goats are browsers. Livestock diet selection and forage preferences are largely linked to the habitats in which they graze and browse. Dietary overlap is highest between free-ranging livestock irrespective of season, whereas herded livestock are able to consume a food source with little potential competition from other livestock. Although the wet-season annual forage resources are able to sustain the livestock population in Leliefontein, this study concludes that the overdependence on annual vegetation would make livestock vulnerable during drought periods when forage production is low.     

Populations and production of fat-tailed and fat-rumped sheep in the Horn of Africa

The six countries comprising the Horn of Africa are Djibouti, Eritrea, Ethiopia, Kenya, Sudan and Somalia. Together, they cover an area of just under 5 million square kilometres and support a human population of 17.7 million at an average density of 38.15 people per square kilometre (although in the purely pastoral areas population density is probably of the order of 15–16 people per square kilometre). The Horn is a major repository of domestic animal biodiversity and genetic resources and is home to 15 million one-humped camels, 110 million cattle, 94 million goats and 102 million sheep. A list of 72 sheep “breeds” of which 23 can be considered fat-tailed or fat-rumped has been compiled for the area, although many of these are merely subtypes of a larger grouping and several are not native to the Horn. This paper provides information, where such is available, on the distribution, numbers and production parameters of the fat-tailed and fat-rumped sheep that occupy the Horn.     

Genetic parameters of production and fertility traits in Hungarian Merino sheep

Hungary has a long-standing tradition in Merino breeding and improvement. During the past decades several attempts have been made to introduce a number of other sheep breeds. Although this effort was not in vain the majority of the sheep population is still the Hungarian Merino breed. The adaptability, endurance and excellent wool-producing ability of this breed is first rate and is worth preserving (V eress et al. 1997). The profitability of a sheep production system is determined by both fertility and production traits. Reproduction performance is usually defined as litter weight per dam per year. Progress can be achieved through various ways. One of them is frequent lambing which also has the advantage that lamb production becomes more consistent throughout the year. Another possibility is producing larger litter sizes (LS), and yet a another opportunity for increased production is having lambs with larger weights (WT). Simultaneous enhancement can also be achieved if there is no antagonism between these traits. From these several fertility traits LS from the first to the fifth parity was chosen for analysis as LS is one of the most important traits concerning reproduction performance. Of the production traits, WT measured at various ages, greasy fleece weight (GFW) from the first five shearings, staple length (SL) and fibre diameter (FD) at the age of 1 year were taken into the analysis. According to other studies there are several factors influencing the above mentioned traits, namely age, season of previous lambing (PLS), type of birth (TOB), and sex. In general, LS increased with advancing age (L ong et al. 1989; B unge et al. 1990; A p D ewi et al. 1996). For GFW the peak of production was achieved in a relatively early age of 3 years, reported by V eress (1969) and by T urner and Y oung (1969). The effect of PLS on LS was that smaller litters were observed with previous lambing seasons of summer and autumn (L ong et al. 1989). TOB and sex effect on WT have been investigated by several authors (T urner and Y oung 1969, p. 46, 51.; S hrestha and H eaney 1985; M avrogenis 1988; B unge et al. 1990; J urado et al. 1994; V eress et al. 1995; S hrestha et al. 1996). Single-born lambs are heavier than multiples although this difference decreases with age. All authors also agree that male lambs are heavier than females. TOB and sex effect on GFW were reported by T urner and Y oung (1969). T urner and Y oung labelled the TOB effect as a ‘maternal handicap’ as the effect is noticeable even in maturity but decreasing by age. T urner and Y oung (1969) also observed that the WT and GFW of male animals exceeds that of the females, but, unlike with the previous effect, the difference increases with age. There was a negligible difference between sexes in SL and FD. Studying the results of numerous authors, estimates of the genetic parameters of LS, WT, GFW, SL, and FD were found to be generally consistent. Heritabilities of LS ranged from 0.05 to 0.08 (A l -S horepy and N otter 1996; A p D ewi et al. 1996; for litter size at first parity only). A p D ewi et al. (1996) found very high (>0.9) genetic correlations between the first and adult litter size. Heritabilities estimated for WT were higher than those of the fertility traits and ranged in the interval of 0.05–0.47 (S hrestha and H eaney 1985; L ong et al. 1989; B unge et al. 1990; K umar and R eheja 1993; J urado et al. 1994; A l -S horepy and N otter 1996). Genetic correlations between yearling and adult WT were high (J urado et al. 1994; 0.85; A l -S horepy and N otter 1996; 0.85–1.0). GFW heritabilities reported by B lair et al. (1985); T urner and Y oung (1969) were about 0.2 thus also exceeding those of the fertility traits. Regarding the genetic parameters of SL & FD, N otter and H ough (1997); M orris et al. (1996) reported that the heritability of SL and FD was higher than that of GFW (026–0.34; 0.47–0.58). Genetic correlations among production traits were mainly low (M orris et al. 1996; and T urner and Y oung 1969). The objectives of this paper were to determine whether the characteristics of the Hungarian Merino sheep population correspond with the features given in the literature review. Thus the objectives were to obtain the factors influencing the traits examined and to estimate genetic parameters of LS, WT, GFW, SL, and FD, respectively.     

Guinea-pig productivity under traditional management

Results of a 12 month study of traditional guinea-pig production in the western highlands of Cameroon are reported. The mean age of guinea-pigs (Cavia porcellus L.) at first parturition, kidding interval and litter size at birth were 126.30±10.40 d, 64.8±1.70 d and 1.63±0.26 kids respectively. The annual reproductive rate was 9.18 kids/breeding doe while the doe post-partum weight was 530 g. Mean body weights at birth, presumed weaning (21 d) and 15 weeks of age were 78.36±3.20, 147.51±8.10 and 418.88±32 g respectively. Type of birth and sex had a significant effect on body weight at all ages. Birth weight dropped significantly from 83.88±2.87 g for singles to 81.57±3.40 g for twins, 74.25±2.39 g for triplets and 73.75±4.12 g for quadruplets. These differences were maintained to maturity (15 weeks). Males were generally heavier than females. Mortality rates were relatively high among kids: 24% at birth, 39% at 3 weeks and 40% at 15 weeks. Productivity indices were 0.827 kg of young weaned per doe per year, 1560 g of young weaned per kg of doe per year and 2.52 kg of young weaned per kg metabolic weight (kg^0.75) of female per year.     

The impacts of season and livestock management strategy on the quality of diets selected by goats and sheep in the semi-arid rangelands of Namaqualand,South Africa

Access to good-quality forages is one of the major limitations to livestock production in semi-arid pastoral systems. This study aimed to determine whether there are differences in the nutritional quality of diets selected by herded and free-ranging goat and sheep flocks utilising Namaqualand Granite Renosterveld vegetation during the wet and dry seasons. Plant samples collected along the grazing routes of livestock were dried and analysed for their fibre, condensed tannin, total phenolic and mineral nutrient contents. The study showed that a large variety of forages were on offer and livestock groups selected different diets of which some were different to the total diet on offer. In general, significant deficiencies in phosphate, protein and energy in the diets selected by herded and free-ranging goats and sheep were observed in both wet and dry season. The quality of the diets selected by herded and free-ranging livestock was also found to be different from each other, with herded livestock generally selecting more nutrient-dense diets. Herding, therefore, allows livestock to access better-quality forage in the Namaqualand Granite Renosterveld rangeland, where it is generally poor.     

Livestock production in central Mali: Reproduction,growth and mortality of domestic fowl under traditional management

In an 18-month study the domestic fowl in 42 households in three traditional management systems were recorded to determine reproduction, growth and mortality parameters. There were significant differences for all systems combined in the number of clutches started per month with the lowest number being laid in the cool dry season of January and February. Mean number of eggs per clutch was 8.8; the number of eggs increased significantly throughout the career of the hen but there were no significant systems differences. Egg weight was 34.4g there being no significant differences due to age of hen or system. Intervals between clutches were 92 days, annual egg output was 35 per hen (assuming that birds were present in the flock for a year) equivalent to about 118% of mean adult hen body weight: hens actually in the flocks during the study had produced 2.1 clutches on average. Hatchability of eggs was 69.1% there being significant seasonal and systems differences in this parameter, lowest hatchability being in the hot dry season (March to June) and in the rainfed millet system. Mortality rates to eight weeks were 56% of chicks hatched. Growth to 10 weeks averaged 4g/d. Mature cocks weighted 1.60 kg and mature hens 1.02 kg: hen weights were significantly affected by reproductive state, laying hens being heavier than both incubating hens and those rearing chicks, while those rearing chicks were heavier than those incubating. Suggestions for improving productivity are made.     

Genetic parameters for resistance to Haemonchus contortus in Merino sheep in South Africa

Resistance to natural infections of Haemonchus contortus (wireworm) was studied in Merino sheep. From February 1995 to July 1996 data were collected from the OTK Merino Stud on the farm Wildebeesfontein near Hendrina in Mpumalanga province. From March 1998 to January 2000 another Merino flock at Irene in Gauteng province was included in the study. In both cases, 50 randomly-chosen animals from each group of lambs weaned were sampled weekly for faecal egg count (FEC) until a mean of 2500 eggs per gram faeces (epg) was reached. At this stage, all lambs in the group were sampled for FEC, packed cell volume (PCV) and live mass in the case of the Wildebeesfontein flock. Animals were monitored from weaning to about 1 year of age. Data from 5 different groups of lambs (583 animals and 1722 records in total) with genetic links were accumulated and analysed. Variance components and resulting heritabilities for logFEC and PCV were estimated using a bivariate animal model with repeated records. The estimated heritabilities were 0.24 +/- 0.02 for logFEC and 0.14 +/- 0.02 for PCV. A strong negative correlation (-0.84 +/- 0.06) existed between the 2 traits. The genetic correlation between PCV and live mass for the Wildebeesfontein flock was low (0.28 +/- 0.09), while that between logFEC and live mass was negative, although not significantly different from zero (-0.13 +/- 0.09). These results suggest that FEC can be used as a selection criterion for resistance to H. contortus infections in Merino sheep.     

Seasonal patterns of strongyle infections in grazing sheep under the traditional production system in the region of Trikala, Greece

Ten 4-month-old female sheep of the Karagouniko dairy breed were used to monitor the seasonal fluctuations of strongyle infections in sheep during the first year of grazing under the traditional production system in the region of Trikala, Greece, where control of nematodes is currently based exclusively on the frequent use of anthelmintics which might contribute to the appearance of anthelmintic resistance. The sheep grazed communal pasture plots and did not receive any anthelmintic treatment during the entire study period. Faecal egg counts (epg), plasma pepsinogen levels, blood values, and genera of parasitic strongyles recovered from coprocultures were recorded monthly. Mean epg for strongyle-type eggs were significantly higher during summer. Mean plasma pepsinogen levels were significantly higher during spring and summer. The genera of parasitic strongyles recovered from the faecal cultures were Haemonchus, Ostertagia, Trichostrongylus, Cooperia, Nematodirus, Oesophagostomum, and Chabertia. The percentages of larvae for Haemonchus, Ostertagia, Cooperia, and Oesophagostomum were significantly higher during winter. The percentages of larvae for Trichostrongylus were significantly higher during summer. During summer, levels of RBC, HGB, and HCT were depressed and levels of MCV, MCH, and MCHC were elevated. Mean epg for strongyle-type eggs had a significant inverse correlation with RBC, HGB, HCT, and positive correlation with MCH, MCHC, and percentages of eosinophils in differential leucocyte counts. The seasonal pattern of infection observed in the present study indicates that it is possible to decrease the number of treatments to one per year, thus, reducing the possibility for the appearance of anthelmintic resistance.     

肉羊生产日常管理系统的研制

在“现代肉羊生产管理系统”基础上，采用Access和VB6.0建立核心数据库和各种数据接口，为饲料配方、遗传育种分析、羊场管理、决策和疾病诊断等模块提供各种数据支持。所建立的“肉羊生产日常管理系统”在进一步加强功能的同时，内核更简洁、高效，字段更灵活、丰富，查询更快捷、准确，打印更方便、实用，适合于各种规律和生产用途的羊场管理。     

Population parameters for birth and ewe fleece weight at different parities in Baluchi sheep

ZUSAMMENFASSUNG: Populationsparameter für Geburts- und Vlie?gewicht von Baluchi Schafen Das Datenmarterial stammt von zwei Herden einer Schafzuchtstation in NO Iran aus den Jahren 1966-1989. Die Tiere waren unselektiert und stammten aus zuf?llig verteilten Paarungen. Es wurden Geburtsgewicht und Vlie?gewicht bei verschiedenen Altersstufen erhoben und Varianzkomponenten mittels Restringierter Maximaler Likelihood mit einem bivariaten Tiermodell mit fixen Wirkungen von Jahr, Geschlecht, Geburtstyp und Parit?t sowie Zufallswirkungen für additiven Genotyp des Lammes (direkt) und des Mutterschafes (maternal), gemeinsamer Umwelt (ausgenommen Vlie?gewicht) und Resteinflu? gesch?tzt. Direkte und maternale genetische Korrelationen zwischen Leistungen verschiedener Parit?ten wurden berechnet. In Herde 1 scheinen Varianzen und Heritabilit?tswerte für Lammgewicht bis Parit?t 5 zuzunehmen, kaum aber in Herde 2. Die durchschnittlichen Heritabilit?tswerte, direkt, maternal und gesamt waren 0.12, 0.11 und 0.26, die genetische Korrelation zwischen direkten und maternalen Wirkungen 0.42. Bei Vlie?gewicht waren in Herde 1 keine Ver?nderungen der Varianzen und Heritabilit?tswerte mit Alter zu erkennen, aber bei Herde 2 nahmen ph?notypische und Umweltvarianz mit Alter leicht zu. Durchschnittliche direkte, maternale und Gesamtheritabilit?t waren 0.19, 0.04 und 0.22, die genetische Korrelation zwischen direkten und maternalen Wirkungen geringgradig positiv in Herde 1, aber mit Alter zunehmend negativ in Herde 2. Die genetischen Korrelationen für direkte Wirkungen auf Geburtsgewicht waren hoch zwischen Parit?ten 1 bis 5, aber niedriger bei Parit?t 6 und jene zwischen maternal bedingten Wirkungen zeigten ?hnliche Trends. In Herde 2 waren Werte mit Parit?t 6 ?hnlich wie die zwischen den übrigen Parit?ten. Die die Vlie?gewichte betreffenden direkt genetischen Korrelationen zwischen Parit?ten waren in beiden Herden ?hnlich (0.73-0.92), jene, die maternale Wirkungen betreffen, deutlich geringer, besonders soweit sie Parit?ten 5 und 6 betroffen haben und zeigten besonders bei Herde 2 starke Schwankungen (-0.54 bis 0.74). SUMMARY: Direct and maternal performance of ewes at different parities were examined in Baluchi sheep. The data set was collected during the period 1966-1989 from two flocks at a sheep breeding station in the north-east of Iran. The animals included in the data set were unselected and randomly mated. The traits analysed were birth weight of lamb and fleece weight at different parities of the ewe. Variance components were estimated using Restricted Maximum Likelihood with a bivariate animal model including fixed effects of year, sex, type of birth and parity, and random effects of additive genotype of lamb (direct genetic effect), additive genotype of ewe (maternal genetic effect) and common environment (excluded for ewe fleece weight), and random residual effect. Direct and maternal genetic correlations between different parities were estimated. There was evidence of increasing phenotypic and genetic variances and heritabilities from parity 5 for birth weight of lamb in flock 1, but only evidence of a slightly increasing age trend for the environmental and phenotypic variance in flock 2. The average heritabilities over flocks and parities were 0.12, 0.11 and 0.26 for the direct, maternal and total heritability, respectively, while the average genetic correlation between direct and maternal effects for this trait was 0.42. There were no indications of any age changes in variances or heritabilities for ewe fleece weight in flock 1, but indications of slightly increasing age trends for the environmental and phenotypic variance. The average heritabilities over flocks and parities were 0.19, 0.04 and 0.22 for the direct, maternal and total heritability, respectively, while the average genetic correlation between direct and maternal effects was slightly positive in flock 1 but increasingly negative with age of the ewe in flock 2. Direct genetic correlations between parities 1-5 were very high for birth weight of lambs (on average 0.96) in contrast to the markedly lower correlations of parities 1-5 with parity 6 (on average 0.67) in flock 1 with a similar pattern for the maternal genetic correlations. In flock 2, these correlations were also high but without the marked decrease between parities 1-5 with parity 6 that was found in flock 1. Direct genetic correlations between the various parities for ewe fleece weight were similar for the two flocks, ranging from 0.73 to 0.92 and without any obvious differences between the various combinations of parities. However, the maternal were markedly lower than the direct genetic correlations, especially for the combinations of parity 5 and 6 with the earlier parities, and most pronounced in flock 2 fluctuating from -0.54 to 0.79. To obtain reliable estimates of breeding values for birth weight of lamb, it is recommended that the prediction should include not only earlier but also later parities (ages) of the ewe.     

Beef cattle productivity under traditional and improved management in Botswana

Summary A comparison of productivity over a 4-year period from indigenous type beef cattle under two production systems in Botswana is reported. The two systems are: the traditional system on unenclosed communal grazing (cattle post) and ranching within fenced paddocks. Calving percentages, 7-month old calf weight, calf mortality and post-weaning growth to 18 months of age under cattle post conditions were 46·4 per cent, 122·5 kg, 10·2 per cent and 88·5 kg respectively. Corresponding figures for cattle on the fenced ranches were 74·0 per cent, 177·4 kg, 8·5 per cent and 105·8 kg. These results indicate overall productivity estimates of 51 and 120 kg of weaner calf per cow per year and 86 and 188 kg of 18-month old calf per cow per year for the cattle post and fenced ranch respectively.

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Productividad Del Ganado De Carne Bajo Manejo Tradicional Y Mejorado En Botswana

Resumen Se describe y compara la productividad en un periodo de cuatro años, de ganado de carne indígena bajo dos sistemas de producción en Botswana. Los dos sistemas fueron el tradicional en pastoreo comunal (puestos ganaderos), y el de pastoreo en ranchos con división de potreros. El porcentaje de partos, el peso de los terneros a los siete meses de edad, la mortalidad en animales jovenes y el crecimiento hasta los 18 meses en pastoreo comunal fueron respectivamente 46·4 por ciento, 122·5 kg, 10·2 por ciento y 88·5 kg. Los valores correspondientes para el ganado en ranchos con división de potreros fueron 74·0 por ciento, 177·4 kg, 8·5 por ciento y 105·8 kg. Estos resultados indican estimativos de productividad general de 51 kg y 120 kg en terneros en crecimiento por vaca año y 86 kg y 188 kg en terneros de 18 meses de edad por vaca año para el ganado en pastoreo comunal y en ranchos respectivamente.

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Productivite De Bovins De Boucherie En Exploitation Traditionelle Et Amelioree Au Botswana

Résumé La productivité de bovins de boucherie de race locale élevés au Botswana suivant deux systèmes différents est comparée pendant une période de quatre ans. L'élevage traditionnel sur pâturage commun non clos et le ranching en enclos sont les deux systèmes utilisés. Les pourcentages de vêlage, le poids des veaux à sept mois, la mortalité des veaux et la croissance du sevrage à 18 mois sont respectivement de 46,4 p. 100, 122,5 kg; 10,2 p. 100 et 88,5 kg pour le bétail sur pâturage non clos et de 74 p. 100, 177, 4 kg, 8,5 p. 100 et 105,8 kg pour le bétail en enclos. Ces résultats entraînent une productivité totale de 51 kg et 120 kg de veau sevré par vache et par an et de 86 kg et 188 kg de taurillon de 18 mois par vache et par an respectivement pour l'élevage traditionnel et celui en enclos.

     

Epidemiology of gastrointestinal nematodes of sheep managed under traditional husbandry system in Kashmir valley

The present study was conducted with the objective to investigate the seasonal epidemiological prevalence of gastrointestinal tract (GIT) nematodes in different age groups, sexes and breeds (genotypes) of sheep through necropsy and faecal analysis over a period of 2 years in Kashmir valley, India. A total of 1533 sheep were examined [faecal examination: 1035 (year 1: 561, year 2: 474); necropsy: 498 (year 1: 232, year 2: 266)]. Out of these, 945 (61.64%) were found infected [faecal examination: 697 (67.34%, year 1: 390 (69.51%), year 2: 307 (46.99%); necropsy: 248 (49.79%, year 1: 123 (53.01%), year 2: 125 (64.69%)] with GIT nematodes. The over all prevalence of GIT nematodes in sheep in year 1 was 64.76 and 58.37% in year 2 (P=0.04). The parasites in decreasing order of prevalence (%) in sheep were Haemonchus contortus (59.6); Ostertagia circumcincta (38.0); Bunostomum trigonocephalum (37.7); Chabertia ovina (37.7); Trichostrongylus spp. (33.9); Nematodirus spathiger (29.4); Oesophagostomum columbianum (28.4); Trichuris ovis (23.5) and Marshallagia marshalli (22.1). Season, sex, age, and genotype were the factors that influenced the epidemiological prevalence of GIT nematodes in sheep in the present study. The maximum nematode infection was observed in summer season and lowest in winter (P=0.0005). Local Kashmiri breed was less infected as compared to other genotypes (P>0.05). Lower age groups were more infected than adult animals (P>/=0.05). Prevalence was higher in rams (males) than eves (females) (P>0.05). The present study will initially be of great significance to add to the existing knowledge of the epidemiology of GIT nematodes of small ruminants and the findings will be quite helpful to devise the appropriate control and prophylactic strategies for GIT nematodiasis of sheep reared under the temperate agro-climatic conditions.     

Effect of environmental factors on estrus synchronization and artificial insemination success in farmers flock in sheep under semi-arid tropical region

Environmental cues in the different seasons might influence the estrus and lambing percentages. The present study was conducted to assess the effect of environmental factors on estrus synchronization (ES) and artificial insemination success in sheep . During the period from 2012 to 2017, a total of 1,197 ewes of Kheri and Malpura breeds of 34 farms originating from 10 villages were synchronized for estrus and then fixed-time artificial insemination (FTAI) was done. Oestrous synchronization was done by intravaginal progesterone sponges and eCG protocol. Fixed-time cervical insemination was performed 48 and 56 hr after sponge removal in ewes exhibiting estrus, using liquid chilled semen containing 100 million sperm per dose of Patanwadi/Malpura rams. Mean sunshine hours, maximum and minimum ambient temperatures, temperature amplitude, mean relative humidity (RH), temperature-humidity index (THI), mean temperature during sponge-in to sponge-out—12-day period, sponge-out and next day, AI day and AI to next 15 days have been calculated. The estrus response and lambing percentage were higher (p < .05) when ES and FTAI were done during hot-humid with rainfall season. Successful (p < .05) ES occur when the minimum temperature was higher in cold-humid season, and the sunshine hour was higher in hot-humid with scanty rainfall season during sponge-in to sponge-out period. The success of the lambing percentage was higher (p < .05) when maximum temperature, minimum temperature, mean temperature and THI was higher on the day of AI and the next 15-day period, irrespective of the season. The success of FTAI indicates the adaptability of the local breed to tolerate the harsh climate of the hot semi-arid region without much hindrance in lambing percentages.     

半干旱区农田杂草的生活史对策研究

2008-2009年通过利用当地常见的10种杂草种植于不同处理的农田,研究半干早区农田杂草群落结构以及10种杂草群落组分种对环境因子的响应,结果表明,1)同一物种在不同的气候环境下,可以表现出不同的生活史策略.蝇虫实、田旋花和金荞麦2008年生活史策略分别具有竟争型(C)对策属性、胁迫忍耐型(S)对策属性和中间型(C-...     

Efficacy of 3 anthelmintics in communally grazed sheep as reflected by faecal egg count reduction tests in a semi-arid area of South Africa

A survey was conducted on the occurrence of anthelmintic resistance of nematodes in communally grazed sheep in a semi-arid area near Mafikeng, South Africa, from January to March 2006. In the herds belonging to twelve smallholder sheep farmers, the efficacies of albendazole, levamisole and closantel were tested by faecal egg count reduction tests where 80 % efficacy was considered the cut off for anthelmintic resistance. The results of the faecal egg count reduction tests showed more than 80% efficacy with all the drugs used in most cases, but there were notable exceptions. In 1 case, closantel had an efficacy of 72%, albendazole had an efficacy of 68% and levamisole showed efficacies of 58%, 60% and 75% respectively on 4 farms. The occurrence of anthelmintic resistance in this farming sector is of concern and steps should be taken to prevent its further spread and development to avoid a situation developing as on numerous commercial sheep farms in South Africa where resistance is common.     

Direct and maternal (co)variance components,genetic parameters and annual trends for growth traits of Dorper sheep in semi-arid Kenya

Genetic and phenotypic parameters were estimated for lamb growth traits for the Dorper sheep in semi-arid Kenya using an animal model. Data on lamb growth performance were extracted from available performance records at the Sheep and Goats Station in Naivasha, Kenya. Growth traits considered were body weights at birth (BW0, kg), at 1 month (BW1, kg), at 2 months (BW2, kg), at weaning (WW, kg), at 6 months (BW6, kg), at 9 months (BW9, kg) and at yearling (YW, kg), average daily gain from birth to 6 months (ADG_0–6, gm) and from 6 months to 1 year (ADG_6–12, gm). Direct heritability estimates were, correspondingly, 0.18, 0.36, 0.32, 0.28, 0.21, 0.14, 0.29, 0.12 and 0.30 for BW0, BW1, BW2, WW, BW6, BW9, YW, ADG_0–6 and ADG_6–12. The corresponding maternal genetic heritability estimates for body weights up to 9 months were 0.16, 0.10, 0.10, 0.19, 0.21 and 0.18. Direct-maternal genetic correlations were negative and high ranging between −0.47 to −0.94. Negative genetic correlations were observed for ADG_0–6–ADG_6–12, BW2–ADG_6–12, WW–ADG_6–12 and BW6–ADG_6–12. Phenotypic correlations ranged from 0.15 to 0.96. Maternal effects are important in the growth performance of the Dorper sheep though a negative correlation exists between direct and maternal genetic effects. The current study has provided important information on the extent of additive genetic variation in the existing flocks that could now be used in determining the merit of breeding rams and ewes for sale to the commercial flocks. The estimates provided would form the basis of designing breeding schemes for the Dorper sheep in Kenya. Implications of the study to future Dorper sheep breeding programmes are also discussed.