Weaner survival is heritable in Australian Merinos and current breeding objectives are potentially leading to a decline in survival

2019 ◽  
Vol 59 (1) ◽  
pp. 35
Author(s):  
S. F. Walkom ◽  
A. N. Thompson ◽  
E. Bowen ◽  
D. J. Brown
Keyword(s):  
Production Systems ◽  
Genetic Relationships ◽  
Survival Rates ◽  
Production Traits ◽  
Weaning Weight ◽  
Australian Sheep ◽  
Potential Impact ◽  
Selection For ◽  
Fleece Weight ◽  
The Relationship

There is little evidence to show that mortality rates during the period after weaning are improving over time in Australian sheep. The average mortality rate of Merino lambs during the post-weaning period has been estimated to be 5.2%. The present study explored the potential for producers to breed for improved survival rates during the post-weaning period and the potential impact this would have on key production traits. A total of 122526 weaner survival (mortality) records were obtained from 18 Merino flocks, between 1989 and 2014, encompassing a wide variety of Australian Merino sheep types and production systems. The heritability of weaner survival from a sire model was estimated to be 0.07 ± 0.01 and was significantly greater than zero. The survival of lambs post-weaning was significantly influenced by weaning weight, with higher survival rates observed in the heavier lambs. The phenotypic relationship with weight indicates that selection for heavier weaning and post-weaning weights, and in turn larger growth rates, will improve survival rates. There is genetic variation in weaner survival not explained by the relationship with weaning weight. Weight-corrected weaner survival was antagonistically genetically correlated with fleece weight. Due to these antagonistic genetic relationships selection based on popular MERINOSELECT indexes is leading to a very small reduction in the survival rate of lambs after weaning through to the post-weaning stage. To prevent a decline in weaner survival, producers are advised to record weaner survival and include it in their breeding objective.

Selection for weaning weight in Merino sheep. 2. Correlated responses in other production characters

1965 ◽  
Vol 5 (19) ◽  
pp. 361 ◽  
Author(s):  
WA Pattie
Keyword(s):  
Milk Protein ◽  
Survival Rates ◽  
Genetic Correlations ◽  
Negative Relationship ◽  
Weaning Weight ◽  
Merino Sheep ◽  
Selection For ◽  
The Difference ◽  
Fleece Weight ◽  
Lamb Growth

The heritabilities of seven production characters of Merino Sheep and their phenotypic and genetic correlations with corrected weaning weight have been calculated using half-sib and dam-daughter correlations. Realized genetic correlations calculated from responses in Weight Plus and Weight Minus selection flocks, which showed broad agreement with these correlations, were : 17-month body weight, 0.72 ; yield, 0.22 ; clean fleece weight, 0.24 ; and staple length, 0.17. There was zero relationship with greasy fleece weight and crimps per inch, and a large negative relationship between folds and high weaning weight. There were strong phenotypic correlations between lamb growth and milk production through the total weight of milk protein produced. The lamb's genotype was the most important contributor to the difference in weaning weight between the flocks. There were no differences in reproductive performance or survival rates between the flocks but twice as many twin rams and 20 per cent more twin ewes were mated in the Weight Minus flock over the selection period.

scholarly journals Within- and across-flock genetic relationships for breech flystrike resistance indicator traits

2010 ◽  
Vol 50 (12) ◽  
pp. 1060 ◽  
Author(s):  
D. J. Brown ◽  
A. A. Swan ◽  
J. S. Gill
Keyword(s):  
Genetic Relationships ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
The Body ◽  
Production Traits ◽  
Sheep Industry ◽  
Selection Strategies ◽  
Australian Sheep ◽  
Fleece Weight ◽  
Indicator Traits

Flystrike is a major cost for the Australian sheep industry. The industry is currently implementing selection strategies for flystrike resistance to reduce the need for breech flystrike prevention. The following indicator traits are used to select for breech flystrike resistance: wool cover, skin wrinkle on the body and breech, scouring (dags) and wool colour. The aims of this study were to estimate genetic correlations between these indicator traits and production traits using the Sheep Genetics database, to distinguish between within- and across-flock genetic relationships, and to quantify responses to selection using indexes that include breech wrinkle as a proxy trait for flystrike resistance. Breech flystrike indicator traits are all heritable; however, there are significant antagonisms between wrinkle score and some production traits, primarily fleece weight and fibre diameter. Thus, simultaneous improvement in both flystrike resistance and production will be most efficient when index selection is used. Our results show that, depending on the level of emphasis placed on breech wrinkle in the index, reductions in breech wrinkle score of 0.4–0.9 units can be achieved over a 10-year period. As across-flock relationships are generally stronger than within-flock relationships, breeders will be able to take advantage of this additional variation, depending on the relative merit of their flocks. Therefore, ram breeders should combine within-flock selection with across-flock selection where possible. Sheep Genetics released early breech wrinkle Australian Sheep Breeding Values in September 2009 to assist Merino breeders in making faster progress towards reducing breech wrinkle by using flock selection.

scholarly journals LAMB AND WOOL PRODUCTION FROM FIVE BREEDS ON RANGE

1966 ◽  
Vol 46 (1) ◽  
pp. 9-18 ◽  
Author(s):  
J. A. Vesely ◽  
H. F. Peters ◽  
S. B. Slen
Keyword(s):  
Body Weight ◽  
The Other ◽  
Production Traits ◽  
Weaning Weight ◽  
Wool Production ◽  
Breed Differences ◽  
Percentage Yield ◽  
Ewe Lamb ◽  
Fleece Weight ◽  
Staple Length

Rambouillet, Romnelet, Columbia, Targhee, and Suffolk sheep were evaluated under range conditions for the production of lamb and wool in the period 1960–1963. The production traits analyzed were: birth and weaning weight; face cover and neck wrinkling; fertility, prolificacy, weaned lamb production, and body weight of ewe; lamb survival to weaning; grease and clean fleece weight, staple length, wool grade, and percentage yield of clean wool by yearling and mature ewes.Lambs of Romnelet were lighter at birth than those of the other breeds. Targhee and Suffolk were the heaviest at birth. Romnelet and Columbia lambs were lighter at weaning than those of Rambouillet, Targhee, and Suffolk.Fertility, prolificacy, and weaned lamb production were essentially the same in the four range breeds. Suffolk produced more weaned lamb than the other four breeds. There were no breed differences in the survival of lambs.Columbia exceeded all other breeds in production of grease and clean fleece weight. Suffolk produced the smallest amount of wool. Staple length of Columbia ewes was 4.3, 7.5, 18.6, 23.7 mm longer than that of Romnelet, Targhee, Suffolk, and Rambouillet ewes.

The role of selection in the improvement of Welsh Mountain sheep

1958 ◽  
Vol 9 (6) ◽  
pp. 819 ◽  
Author(s):  
JM Doney
Keyword(s):  
Birth Weight ◽  
Maternal Environment ◽  
Weaning Weight ◽  
Phenotypic Correlations ◽  
Selection For ◽  
Heritability Estimates ◽  
Fleece Weight ◽  
Staple Length

Means and variances of several economic characters in Welsh Mountain sheep are given. The repeatabilities of, and phenotypic correlations between, these characters are generally within the range of similar estimates given for other breeds. Heritabilities, calculated from parent-offspring correlations, were : birth weight 0.39, weaning weight 0.68, 18-month weight 0.59, greasy fleece weight 0.61, and staple length 0.73. These values are in general higher than similarly derived estimates from other breeds. A method of correcting heritability estimates to remove the error due to correlation between maternal environment, and the character as measured in the dam, is described. This reduces the estimate for weaning weight to 0.48, and that for 18-month weight to 0.16, but does not change that for fleece weight. The use of such estimates in predicting the effect of selection is discussed, and it is concluded that accurate selection for the chosen economic characters will result in improvement at the present genetic stage of the breed.

The relationship between greasy fleece weight and clean fleece weight in the South Australian Merino

1961 ◽  
Vol 1 (1) ◽  
pp. 34
Author(s):  
GH Ford
Keyword(s):  
Genetic Variability ◽  
Covariance Analysis ◽  
The South ◽  
Weight Relationship ◽  
Different Seasons ◽  
Sire Group ◽  
Selection For ◽  
Fleece Weight ◽  
The Relationship ◽  
Australian Merino

The correlation between clean fleece weight and greasy fleece weight in South Australian strain Merino hoggets of both sexes in three widely different seasons was found to be Rams, 0.841, 0.890, 0.701 and Ewes, 0.846, 0.850 and 0.839. A covariance analysis of clean and greasy fleece weights showed no significant differences between slopes of individual sires, but significant differences between sire group means, indicating genetic variability for these two traits. It is concluded that the correlations are high enough to make selection for clean fleece weight by partial culling on the basis of greasy fleece weight, followed by scouring of midside samples of the fleece from the top sheep for greasy fleece weight, as advocated by Beattie (1956), practicable. The use of the clean fleece weight, greasy fleece weight relationship will rarely be sufficient on its own to formulate a selection plan. The conditions for the use of other aids to estimate clean fleece weight, such as the Neale squeeze machine, are discussed.

A genetic analysis of wool and lamb production traits in Scottish Blackface Sheep

2002 ◽  
Vol 2002 ◽  
pp. 21-21
Author(s):  
A. Murphy ◽  
J. Conington
Keyword(s):  
Genetic Relationships ◽  
Carcass Traits ◽  
Direct Selection ◽  
Meat Production ◽  
Production Traits ◽  
Selection For ◽  
Wool Quality ◽  
Sheep Production ◽  
The Uk ◽  
The Impact

Scottish Blackface sheep have a multi-purpose role in the UK to produce breeding females and lambs for meat consumption. Over the last fifty years, wool has accounted for a very low proportion of economical return from hill sheep production in the UK. In recent years, the ratio of the value of lamb meat to wool clip has altered, with wool becoming relatively more important in particular for hill breeds. The consequence of direct selection for improved carcass traits in these breeds on wool quality is unknown. With other sheep breeds such as Merino, selection for improved wool traits has largely been undertaken with little regard to the impact on meat production. The objectives of this study are to quantify wool quality traits and examine genetic relationships between wool quality and carcass traits in Scottish Blackface sheep.

Continued selection of Romney sheep for resistance or susceptibility to nematode infection: estimates of direct and correlated responses

2000 ◽  
Vol 70 (1) ◽  
pp. 17-27 ◽  
Author(s):  
C. A. Morris ◽  
A. Vlassoff ◽  
S. A. Bisset ◽  
R. L. Baker ◽  
T. G. Watson ◽  
...  
Keyword(s):  
Maximum Likelihood Estimates ◽  
Research Centre ◽  
Control Line ◽  
Production Traits ◽  
Correlated Responses ◽  
Breeding Lines ◽  
Nematode Parasites ◽  
Phenotypic Standard Deviation ◽  
Selection For ◽  
Fleece Weight

AbstractDivergent breeding lines of Romney sheep, selected as lambs for consistently high or low faecal worm egg count (FEC) following natural multi-species challenge by nematode parasites, were established in New Zealand at Wallaceville Animal Research Centre in 1979 and at Rotomahana Station in 1985. In 1988 the Rotomahana lines, including an unselected control line maintained under the same management conditions, were transferred to Tokanui Station where they remained for 4 years. In 1993 elite high and low FEC animals from Tokanui, along with the controls, were transferred to Wallaceville, where merged lines have since been managed together. Selection responses from the lines at Rotomahana and Tokanui, and from a further 5 years of divergent selection in the merged lines, are reported here. For the two most recent lamb crops (1996 and 1997 birth years), log-transformed FECs of the high and low lines were 1·27 and -1·46 phenotypic standard deviation units from the control. After back-transformation to the original scale, where the FEC for control line lambs averaged 1255 eggs per g, the means for the high and low lines were 3Ό5 and 0·27 times the control mean. Animal-model restricted maximum likelihood estimates of her it ability and repeatability for single-record FEC (following separate infections) were 0·28 (s.e. 0·02) and 0·42 (s.e. 0Ό1), respectively. Correlated responses in production traits include significantly decreased post-weaning weight gain and increased dags (breech soiling) in lambs, and decreased fleece weight in yearlings and ewes in the low FEC line, compared with those in the high line. However the low FEC line had proportionally 0·11 more lambs weaned per ewe mated than the high FEC line (F < 0·01). It is concluded firstly that selection for high or low FEC in Romney s has achieved an 11-fold difference between the divergent lines. Secondly, it will generally be necessary in a commercial environment to apply index selection for a combination of increased productivity, decreased FEC and possibly decreased dags, when potential candidates are recorded under conditions of nematode challenge.

Will genetics offer a permanent solution to breech strike?

2010 ◽  
Vol 50 (12) ◽  
pp. 1053 ◽  
Author(s):  
J. S. Richards ◽  
K. D. Atkins
Keyword(s):  
Low Cost ◽  
Management Strategies ◽  
Fibre Diameter ◽  
Production Traits ◽  
Predisposing Factor ◽  
Breeding Programs ◽  
Negative Effect ◽  
Selection For ◽  
Fleece Weight

There are several options for managing flystrike other than mulesing. Breeding for plainer animals that do not require mulesing is an attractive, permanent long-term solution. Breech wrinkle is the key predisposing factor for breech and tail strike. Little effort has been made to reduce wrinkle score in sheep because mulesing was so successful and because there is a perception that reducing wrinkle score will reduce fleece weight. Fleece weight will be reduced if single-trait selection for wrinkle is applied, but if breech wrinkle is included in an index, the negative effect of wrinkle on other production traits can be minimised using the same method as that used to accommodate the negative correlation between fibre diameter and fleece weight. Breeding programs for reduced breech wrinkle should be used in combination with short-term tactical management strategies, especially during the initial stages of the breeding program. The need for tactical management will decrease as the program progresses. This approach can be applied using information that can be recorded easily and at low cost.

Heritabilities of IgA and IgE activities against Teladorsagia and Trichostrongylus L3 larval antigens correlated with traits for faecal worm egg count, health and productivity in Merino sheep

2019 ◽  
Vol 59 (10) ◽  
pp. 1792 ◽  
Author(s):  
Zhongquan Zhao ◽  
Mengzhi Wang ◽  
Shimin Liu ◽  
Dieter Palmer ◽  
Richard Shaw ◽  
...  
Keyword(s):  
Immunoglobulin E ◽  
Genetic Relationships ◽  
Immunoglobulin A ◽  
Specific Ige ◽  
Breeding Value ◽  
Phenotypic Trait ◽  
Total Plasma ◽  
Sampling Protocols ◽  
Selection For ◽  
Fleece Weight

Low faecal worm-egg count (FEC) has been used as a phenotypic trait for breeding sheep for resistance to nematode infection. Application of this trait has resulted in a major reduction in worm-egg output in faeces, but in certain environments some of the resistant sheep develop what is believed to be a hypersensitivity-associated diarrhoea, resulting in soiling of the breech area (dags). To avoid breeding sheep with a propensity to scour, it, therefore, seems logical to combine selection for low FEC with selection for a trait based on the immune response to worm infection. We, therefore, investigated the relationships between immunoglobulin A (IgA) and immunoglobulin E (IgE) activities against L3 larval antigens of Teladorsagia circumcincta and Trichostrongylus colubriformis and measured their inheritance and their genetic relationships with FEC, dag traits and measures of production. Total plasma IgE concentrations were also determined and included in the study. We used 762 progeny from 23 Merino sires selected for resistance to helminths (the ‘Rylington Flock’) and to breech flystrike. Total plasma IgE and IgE activities against T. circumcincta were negatively correlated with liveweight, longissimus dorsi muscle depth, and fleece weight, but positively correlated with severity of dags, softer faeces and back-fat depth. The IgA activity against T. circumcincta was negatively correlated with liveweight and clean fleece weight, but positively correlated with back-fat depth and faecal consistency score. The IgA activity against T. colubriformis was not correlated with any measure, except the breeding value for dags around yearling age. The heritability for the IgA activity against T. circumcincta and T. colubriformis was 0.13 and 0.08 respectively. The heritability for both IgE activity against T. circumcincta and total plasma IgE concentration was 0.39. We conclude that it is feasible to combine FEC and dag traits with an immune trait (in this case, helminth-specific IgE activity and total plasma IgE concentration) and, thus, genetically select sheep for resistance to both helminths and diarrhoea. However, under natural worm-challenge conditions, blood sampling protocols need to developed, on the basis of animal age, season and environment, for optimum estimation of the immune trait and its relationships with other traits.

SHEARLING AND SECOND-YEAR CLEAN FLEECE WEIGHTS AS AN INDEX OF WOOL PRODUCTION IN THREE BREEDS OF RANGE SHEEP

1958 ◽  
Vol 38 (1) ◽  
pp. 53-60
Author(s):  
S. B. Slen ◽  
E. C. Banky ◽  
H. F. Peters
Keyword(s):  
Regression Coefficients ◽  
Reliable Estimate ◽  
Wool Production ◽  
Breed Differences ◽  
Mature Weight ◽  
Second Year ◽  
Selection For ◽  
Fleece Weight ◽  
Relationship Of ◽  
The Relationship

The relationship of shearling and second-year clean fleece weight to total wool production, i.e., first 5 years of life, was analysed in three breeds of range sheep (Canadian Corriedale, Rambouillet, and Romnelet) to determine its usefulness in selection for increased wool production.A correlation of +.67 (p <.01) between shearling clean fleece weight and the sum of the four mature fleece weights was obtained in the three breeds studied. When the first mature weight (second fleece) was correlated with the total weight of the three subsequent fleeces, the correlation was increased significantly (p <.01). Consequently, the second fleece appeared to be a more reliable estimate of lifetime production than shearling weight. No breed differences in these correlations were found when lifetime production was compared to shearling or to second-year fleece weights. The regression coefficients of lifetime production on shearling fleece weight showed that a shearling ewe which produced 1.0 lb. of clean wool above the average produced approximately 3.0 lb. more than the average during her productive life.Shearling fleece weight was found to represent 83, 77, and 80 per cent of the maximum mature fleece weight in the Canadian Corriedale, Rambouillet, and Romnelet, respectively. No breed differences were observed in this relationship.The repeatability of annual clean fleece weight was found to be.93,.83, and.76 for the Rambouillet, Romnelet, and Canadian Corriedale, respectively.

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