A desired gains approach for the prediction of genetic gain in resistance to gastrointestinal nematodes in a multi‐trait breeding objective in Uruguayan Merino sheep

2021 ◽  
Author(s):  
Ana Laura Sánchez ◽  
Washington Bell ◽  
Raúl W. Ponzoni
Keyword(s):  
Genetic Gain ◽  
Gastrointestinal Nematodes ◽  
Merino Sheep ◽  
Breeding Objective

Genetic parameters and responses to selection for pre-weaning growth in suffolk and texel sheep

1995 ◽  
Vol 1995 ◽  
pp. 48-48
Author(s):  
I.W. Purvis ◽  
J.P. Hanrahan
Keyword(s):  
Growth Rate ◽  
Genetic Variation ◽  
Genetic Gain ◽  
Genetic Parameters ◽  
Growth Traits ◽  
Present Report ◽  
Growth Data ◽  
Genetic Trend ◽  
Breeding Objective ◽  
Selection For

In order to evaluate genetic gain in populations under selection it is necessary to be able to partition the observed response into genetic and environmental components. This requires estimates of the appropriate genetic and environmental (co)variances unless appropriate genetic controls are available. Growth rate is an important component of the breeding objective for sheep breeds used as terminal sires and, whereas older estimates of the contribution of genetic variation to differences in preweaning growth indicated heritabilities of the order of 0.1, more recent studies have indicated considerably higher values. The present report concerns analyses of preweaning growth data on purebred Suffolk and Texel sheep to estimate genetic parameters for preweaning growth traits and genetic trend in growth rate from birth to weaning.

Factors influencing the time required to shear Merino sheep and its importance as a breeding objective

1981 ◽  
Vol 21 (111) ◽  
pp. 387 ◽  
Author(s):  
BJ McGuirk ◽  
R Ponzoni ◽  
KD Atkins ◽  
AR Gilmour ◽  
FHW Morley ◽  
...  
Keyword(s):  
No Production ◽  
Merino Sheep ◽  
First Order ◽  
Merino Wool ◽  
Breeding Objective ◽  
Skin Fold ◽  
Fleece Weight ◽  
Time Required ◽  
Wool Industry ◽  
Australian Merino

Two sets of observations have been made on the time required to shear (TRS) Merino sheep. The first, in 1951, involved 98 rams and 75 ewes from one medium Peppin bloodline. Then, in 1975, TRS was recorded on 79 rams and 143 ewes from five different bloodlines, from a number of Merino strains. The effect of different production characters on TRS was estimated by least squares analysis, in models that included the effects of shearer, sex, bloodline (1975 only) and all first order interactions. In the 1951 data, TRS increased with increasing greasy fleece weight and with increasing skin fold in the rams (P <0.05). No production character had a significant effect on TRS in the ewes. In the 1975 data, TRS increased with increasing greasy fleece weight, skin fold, face cover and body weight in at least one sex, and when data from the two sexes were pooled (P <0.05). Skin fold and greasy fleece weight had the largest and most consistent effect. There were also significant differences between the bloodlines in TRS, which were found to be associated with differences between the bloodlines in skin fold, greasy fleece weight, and to a lesser extent, face cover. After studying the likely economic benefit of reducing TRS by selection, we concluded that under current economic situations, where any reduction in TRS would lower only the ancillary costs associated with shearing (shed hands, classing, etc.). TRS is not an important breeding objective for the Australian Merino wool industry.

scholarly journals Epidemiology and Multidrug Resistance of Strongyle Nematodes in Ordos Merino Sheep

2020 ◽  
Author(s):  
Ledege Eye ◽  
Jiya Wuen ◽  
Xiuling He ◽  
Buhe Buyin ◽  
Ying Hai ◽  
...  
Keyword(s):  
Anthelmintic Resistance ◽  
Gastrointestinal Nematode ◽  
Gastrointestinal Nematodes ◽  
Infection Rates ◽  
Merino Sheep ◽  
Predominant Species ◽  
Anthelmintic Efficacy ◽  
Nematode Eggs ◽  
Repeated Use

Abstract Background: Regular whole-flock treatments and long-term repeated use of similar anthelmintics has led to the development of anthelmintic resistance and widespread epidemic of sheep nematodiasis. The current work was carried out to understand the prevalence of gastrointestinal nematodes in Ordos merino sheep and to evaluate the efficacy of currently used anthelmintics. Results: A total of 4014 fresh fecal samples were collected from sheep from March 2017 to April 2019 and fecal nematode eggs were qualitatively and quantitatively analyzed for understanding the prevalence of sheep nematodiasis. The anthelmintic efficacy of currently used drugs was evaluated in naturally infected sheep. The gastrointestinal nematode infection was serious in Ordos merino sheep. The infection rates of nematodes in three consecutive years were 84.3%, 36.9%, and 42.3%, respectively. The Hemonchus contortus and Nematodirus sp. were the dominantly infected species with the infection rates of 84.3% and 65.6% in 2017. Moreover, these species were acquired highly resistance to the Ivermectin, Doramectin, Albendazole and Levamisole. The percentages of FERC were 6.9%, 1.7%, 3.5% and 79.0%, respectively, following single administration. However, Nitroxynil and Closantel showed a strong anthelmintic efficacy on popular dominant species Haemonchus contortus and some other nematodes, while almost no effect on Nematodirus sp. Conclusions: The prevalence of gastrointestinal nematodes in Ordos merino sheep and their resistance to commonly used anthelmintics were comprehensively understood, and the high efficacy drugs on predominant species were screened out. The results will pay a good foundation for developing of reasonable drug use.

scholarly journals Breeding objectives for three silvicultural regimes of radiata pine

2001 ◽  
Vol 31 (4) ◽  
pp. 654-662 ◽  
Author(s):  
Luis A Apiolaza ◽  
Dorian J Garrick
Keyword(s):  
Genetic Gain ◽  
Genetic Correlations ◽  
Pulp Mill ◽  
Radiata Pine ◽  
Breeding Strategy ◽  
Breeding Objective ◽  
Breeding Objectives ◽  
The Difference ◽  
Average Wood

A generic vertically integrated firm, comprising a production forest, a sawmill, and a pulp mill was modelled under three silvicultural regimes: direct to pulp, intermediate (includes production thinning), and intensive (includes production thinnings and pruning). The harvest age traits included in the breeding objective were total volume (m3/ha) and average wood density (kg/m3). Economic values for each trait were calculated as the difference in discounted profit for a unit marginal increase of volume or density, and expressed as relative weights to facilitate comparisons between the objectives. The methodology was applied to a Chilean case study using representative economic and production circumstances. The breeding objectives so derived were 1vol + 2.4den for pulp, 1vol + 1.1den for intermediate, and 1vol + 1.2den for the intensive regime, where vol and den are the breeding values for volume and density, respectively. The firm was profitable under all regimes. Genetic correlations between the objectives for each regime were higher than 0.9, indicating that a single breeding strategy with objective 1vol + 1.5den could be adopted, with almost no loss of genetic gain relative to selecting for a particular silvicultural regime.

Genetic parameters and responses to selection for pre-weaning growth in suffolk and texel sheep

1995 ◽  
Vol 1995 ◽  
pp. 48-48
Author(s):  
I.W. Purvis ◽  
J.P. Hanrahan
Keyword(s):  
Growth Rate ◽  
Genetic Variation ◽  
Genetic Gain ◽  
Genetic Parameters ◽  
Growth Traits ◽  
Present Report ◽  
Growth Data ◽  
Genetic Trend ◽  
Breeding Objective ◽  
Selection For

In order to evaluate genetic gain in populations under selection it is necessary to be able to partition the observed response into genetic and environmental components. This requires estimates of the appropriate genetic and environmental (co)variances unless appropriate genetic controls are available. Growth rate is an important component of the breeding objective for sheep breeds used as terminal sires and, whereas older estimates of the contribution of genetic variation to differences in preweaning growth indicated heritabilities of the order of 0.1, more recent studies have indicated considerably higher values. The present report concerns analyses of preweaning growth data on purebred Suffolk and Texel sheep to estimate genetic parameters for preweaning growth traits and genetic trend in growth rate from birth to weaning.

scholarly journals Epidemiology and Multidrug Resistance of Strongyle Nematodes in Ordos Merino Sheep

2020 ◽  
Author(s):  
Ledege Eye ◽  
Jiya Wuen ◽  
Xiuling He ◽  
Buhe Buyin ◽  
Ying Hai ◽  
...  
Keyword(s):  
Haemonchus Contortus ◽  
Anthelmintic Resistance ◽  
Severe Infection ◽  
Nematode Species ◽  
Gastrointestinal Nematodes ◽  
Infection Rates ◽  
Merino Sheep ◽  
Predominant Species ◽  
Anthelmintic Efficacy ◽  
Nematode Eggs

Abstract Background: Regular whole-flock treatments and long-term use of similar anthelmintics have led to the development of anthelmintic resistance and widespread epidemics of nematodiasis in sheep. This study was performed to understand the prevalence of gastrointestinal nematodes in Ordos Merino sheep and evaluate the efficacy of currently used anthelmintics. Results: Between March 2017 and April 2019, a total of 4014 fresh fecal samples were collected from sheep, and fecal nematode eggs were qualitatively and quantitatively analyzed to understand the prevalence of sheep nematodiasis. The anthelmintic efficacy of currently used drugs was evaluated in naturally infected sheep. Severe infection by gastrointestinal nematodes was observed in the Ordos Merino sheep. The infection rates of the nematodes in 3 consecutive years were 84.3%, 36.9%, and 42.3%. Haemonchus contortus and Nematodirus sp. were the predominant nematode species, with infection rates of 84.3% and 65.6%, respectively, in 2017. Moreover, these species had acquired high resistance to ivermectin, doramectin, albendazole, and levamisole; the fecal egg count reduction percentages were 6.9%, 1.7%, 3.5%, and 79.0%, respectively, after a single administration. Nitroxynil and closantel showed strong anthelmintic efficacy against the predominant species Haemonchus contortus and other nematodes, but they had almost no effect on Nematodirus sp. Conclusions: The prevalence of gastrointestinal nematodes in Ordos Merino sheep and their resistance to commonly used anthelmintics were comprehensively evaluated, and the drugs with high efficacy against the predominant species were identified. The findings of this study will provide a good foundation for the appropriate use of anthelmintics.

scholarly journals Effect of Gastrointestinal Nematodes on Reproduction and Lamb Growth in Australian Merino Sheep

2020 ◽  
Vol 5 (2) ◽  
pp. 1-5
Author(s):  
Hernández-Russo Z
Keyword(s):  
Natural Infection ◽  
Gastrointestinal Nematodes ◽  
Reproductive Rate ◽  
Economic Losses ◽  
Control Group ◽  
Merino Sheep ◽  
Proven Efficacy ◽  
Lamb Growth ◽  
Parasite Challenge ◽  
Australian Merino

Environmental conditions in Uruguay favour the development of gastrointestinal nematodes (GIN) throughout the year, with clinical or subclinical manifestations that cause significant economic losses. The aim of this study was to evaluate the effect of the GIN on fertility, fecundity, reproductive rate and lamb growth in Australian Merino sheep grazing on basalt fields. The study was carried out in a farm located in north of Uruguay. Sixty-eight Merino ewes facing a natural parasite challenge were divided into two groups. Control group was doused with active anthelmintic that have proven efficacy to minimize the effects of parasitic and the parasitized group that did not receive anthelmintic, except rescue dosages. Stool sample of each sheep was collected monthly for egg counts (EPG) of GIN using McMaster technique and nematode genders were identified from infective larvae obtained in cultures by Roberts O’ Sullivan technique. Artificial insemination and ewes were mated for new service, and pregnancy condition was diagnosed by ultrasound. Lambing control was made and lambs were weighed at birth and marking. The evolution of EPG values showed significant differences between groups at the end of gestation and lactation. Haemonchus spp. was the main gender of nematodes found, followed by Trichostrongylus spp. Fertility was 95 % versus 90 %; fecundity 87 % versus 63 % and reproductive rate 73 % versus 47 % for the control group and the parasitized one respectively. No significant differences were recorded in birth-weight. However market-weight and lamb daily gain were lower in the parasitized group. The effect of natural infection GIN was evident in lower reproductive performance of Australian Merino sheep.

scholarly journals CRANBERRY VARIETY FRUIT YIELD AND YIELD COMPONENETS

HortScience ◽  
1993 ◽  
Vol 28 (4) ◽  
pp. 258E-258
Author(s):  
Elissa M. Novy ◽  
Nicholi Vorsa
Keyword(s):  
Regression Analysis ◽  
Genetic Gain ◽  
Yield Components ◽  
Fruit Set ◽  
Unit Area ◽  
Fruit Yield ◽  
Parental Selection ◽  
Breeding Objective ◽  
Berry Weight ◽  
Yield And Yield Components

Accurate estimates of yield and yield components for parental selection would facilitate cranberry breeding efforts. A study was designed to obtain value estimates for traits related to yield. Ten commonly-cultivated varieties grown in a replicated planting, were evaluated in 1991 and 1992 for fruit yield per unit area (FY), average berry weight (BW) and number of berries per unit area, or berry concentration (BC). Averaged over all varieties, FY was significantly greater in 1992. BC was responsible for higher yields in 1992. Regression analysis revealed that BC accounted for more of the variation in FY than did BW in both years. BW accounted for some variation, however, in 1991 when FY was lower. Varieties differed significantly in FY, BW and BC. Hybrid varieties bad significantly greater FY and BW than wild selections. Variation for yield components exists among varieties tested, suggesting genetic gain is possible for yield with additional breeding efforts. In particular, greater fruit set should be emphasized as a breeding objective.

The influence of stocking rate and mixed grazing of Angora goats and Merino sheep on animal and pasture production in southern Australia. 4. Gastrointestinal parasitism

2014 ◽  
Vol 54 (5) ◽  
pp. 587 ◽  
Author(s):  
B. A. McGregor ◽  
P. J. A. Presidente ◽  
N. J. Campbell
Keyword(s):  
Management Practices ◽  
Gastrointestinal Nematode ◽  
Gastrointestinal Nematodes ◽  
Stocking Rate ◽  
Sources Of Information ◽  
Pasture Production ◽  
Merino Sheep ◽  
Sheep And Goats ◽  
Gastrointestinal Parasitism ◽  
The Impact

Gastrointestinal nematodes limit the growth, production and welfare of goats but there are few reliable sources of information for recommending management practices across flocks. The effects of animal species (Angora goat, Merino sheep, mixed-grazed goats and mixed-grazed sheep at the ratio of 1 : 1) and stocking rate (SR: 7.5, 10, 12.5 animals/ha) on gastrointestinal parasitism were determined in a replicated experiment on improved annual temperate pastures in southern Australia, from 1981 to 1984. Detailed monitoring of gastrointestinal nematodes was undertaken on animals before, during (five times per year) and at the conclusion of studies using faecal strongyle egg counts (WEC) and total worm counts. Sheep had a greater proportion of nematodes as Teladorsagia spp. and goats a greater incidence of Trichostrongylus spp. Both goats and sheep developed resistance to Nematodirus spp. during the experiment. WEC was similar in goats and sheep at the start of the experimental period but, thereafter, was consistently greater in goats than in sheep. While WEC was highly related to total worm count, the regressions for sheep and goats were different. Increasing the SR increased the WEC of goats and mixed-grazed goats but not of sheep. During the experiment, WEC declined at 7 and 10 animals/ha but increased at 12.5/ha. Mixed grazing with goats provided beneficial effects for sheep at all stocking rates, but the effects for goats were dependent on the stocking rate, being beneficial at 7.5 and 10/ha but harmful at 12.5/ha. The WEC of separately grazed goats were generally higher than the WEC of mixed grazed goats. The WEC of mixed sheep were lower than those of separately grazed sheep. During the experiment, the WEC of mixed grazed sheep declined faster than the WEC of separately grazed sheep but the WEC of separately grazed goats at 12.5/ha and of mixed grazed goats at 10 and 12.5/ha increased. Under the environmental and pastoral conditions examined, Angora wether goats should not be grazed at SR above those recommended for wether sheep. In the present study, the impact of gastrointestinal-nematode infections in goats was reduced at lower SR. Further, mixed grazing of Angora wether goats with wether sheep at or below the recommended SR resulted in reduced gastrointestinal parasitism for both sheep and goats, compared with monospecific grazing conditions. Goats did not represent a gastrointestinal-nematode hazard to sheep.

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