Heterogeneity of lifetime reproductive performance, its components and associations with wool production and liveweight of Merino ewes

2009 ◽  
Vol 49 (7) ◽  
pp. 624 ◽  
Author(s):  
G. J. Lee ◽  
K. D. Atkins ◽  
M. A. Sladek
Keyword(s):  
Reproductive Performance ◽  
Agricultural Research ◽  
Fibre Diameter ◽  
Research Centre ◽  
Reproduction Rate ◽  
High Performing ◽  
Management Interventions ◽  
The Difference ◽  
Fleece Weight ◽  
Net Reproduction

The heterogeneity in lifetime (2–6 years of age) reproductive performance within three research flocks maintained at the Agricultural Research Centre, Trangie, in central-western New South Wales, was used to establish the potential to improve flock reproductive performance by identifying performance segments for either selection or for differential management. The data comprised a total of 32 716 records from 7322 ewes, collected over the period from 1977 to 2003. Within each of the flocks, there were large differences (P < 0.001) in lifetime net reproduction rate, and each of its components (fertility, fecundity and lamb survival), between each of the net reproduction rate quartiles. The difference in net reproduction between the ewes in the top quartile and those in the bottom quartile was equivalent to an additional lamb per ewe annually. These differences in reproduction rate between the quartiles were not related to pre-joining liveweight or condition score. Higher reproductive rates were associated with a cost to clean fleece weight, although the estimated effects on fibre diameter were small. Opportunities to use this variation to improve reproduction rates are discussed and include retaining high-performing ewes longer in the breeding flock, removing poor performers and targeting management interventions towards ewes that will yield the largest responses.

Genetic evaluation of production traits between and within flocks of Merino sheep. II. Component traits of the Hogget fleece

1993 ◽  
Vol 44 (7) ◽  
pp. 1523 ◽  
Author(s):  
SI Mortimer ◽  
KD Atkins
Keyword(s):  
Agricultural Research ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Matter Content ◽  
Research Centre ◽  
Production Traits ◽  
Merino Sheep ◽  
Phenotypic Correlations ◽  
Genetic And Phenotypic Correlations ◽  
Fleece Weight

Components of the fleece and wool quality traits were measured or assessed on Merino hogget ewes in an unselected multiple-bloodline flock over a 7-year period at Trangie Agricultural Research Centre, N.S.W. The traits recorded were face cover score (FC), leg cover score (LC), neck fold score (NF), body fold score (BF), wax content (W), suint content (S), vegetable matter content (VM), dust penetration (D), follicle density (N) and follicle ratio (RA). Genetic differences within and between flocks of Merino sheep were examined for the traits, and estimates of heritability and within-flock genetic and phenotypic correlations and between-flock genetic correlations among the traits were obtained. Genetic and phenotypic correlations were also estimated between these traits and the major wool production traits: greasy fleece weight (GFW), clean fleece weight (CFW), fibre diameter (FD), body weight (BWT) and staple length (SL). Significant strain. flock within strain and flock effects were wresent for all traits. The influence of environmental effects (birth-rearing type, age at measurement and age of dam) on the traits was estimated, with the birth-rearing type being significant and the largest effect for most traits. Paternal half-sib heritability estimates were 0.44� 0.06 for FC, 0.35� 0.06 for LC, 0.24�0.05 for NF, 0.23�0.05 for BF, 0.38�0.07 for W, 0.42�0.07 for S, 0.06�0.04 for VM, 0.22�0.06 for D, 0.20� 0.07 for N and 0.21�0.07 for RA. Estimates of within-flock phenotypic and genetic correlations were in broad agreement with available published estimates. The implications of the results for Merino breeding programs are discussed.

The influence of selection and plane of nutrition on the components of fleece weight in Merino sheep

1958 ◽  
Vol 9 (6) ◽  
pp. 802 ◽  
Author(s):  
RB Dun
Keyword(s):  
Fibre Diameter ◽  
Fibre Length ◽  
Small Contribution ◽  
Cross Sectional ◽  
Single Character ◽  
The Mean ◽  
Low Levels ◽  
The Difference ◽  
Fleece Weight ◽  
High Level

The components of clean fleece weight were examined in five experimental flocks of medium-wool Peppin Merinos. Four single-character selection groups – clean fleece weight plus, clean fleece weight minus, crimps per inch plus, and crimps per inch minus – were examined by measuring fleece production in 18-month-old ewe progeny. Measurements were also made on progeny from the "nucleus" flock, which was selected for clean fleece weight with subsidiary selection for crimps per inch and against fold score. Data were collected in 1952 and 1954. The 1954 figures were obtained from a nutrition experiment in which sheep mere grown from weaning to 18 months on a high and on a low plane of nutrition. The mean measurements of the components of clean fleece weight (W) were compared between flocks using the "percentage deviation" technique. Four comparisons were made: (1) Nucleus/Fleece minus; (2) Fleece plus/Fleece minus; (3) Crimps minus/Crimps plus; (4) high nutritional plane/low nutritional plane. In comparisons (1) , (2), and (3), difference in weight of wool per unit area of skin (w) accounted for nearly all the difference in W. Body weight (S) made a small contribution while difference in fold score (R) was negligible. Fibre density (N) accounted for +86 per cent., and fibre cross-sectional area (A) for –28 per cent., of the difference in W in comparison (1). In comparison (2) the figures were N +47 per cent., A +21 per cent., while the figures for comparison (3) were N –26 per cent., A +121 per cent. The increase in fleece weight was invariably accompanied by a decrease in crimps per inch. In all three comparisons primary density (P) was the major cause of change in N. Fibre length (L) made a uniform contribution of approximately +15 per cent. in the three comparisons.The relative importance of the components of fleece weight was similar at both high and low levels of nutrition.The effect of a high level of nutrition was to produce large increases in A, L, and S. The increase in S was compensated by an equal decrease in P. The increase in fibre diameter was not associated with any change in crimps per inch.

Corrigendum - Response to partial selection on clean fleece weight in South Australian strong-wool Merino sheep

1969 ◽  
Vol 20 (1) ◽  
pp. 151
Author(s):  
O Mayo ◽  
JC Potter ◽  
RE Brady ◽  
CW Hooper
Keyword(s):  
Fibre Diameter ◽  
Index Method ◽  
Visual Method ◽  
Merino Sheep ◽  
Index Group ◽  
Agricultural College ◽  
Selection For ◽  
The Difference ◽  
Fleece Weight ◽  
Selection Of

This paper reports the results of an experiment carried out at Roseworthy Agricultural College from 1953 to 1966 comparing two bases of selection of rams: (1) visual appraisal (the "visual" method); (2) visual culling of 70% of rams followed by selection of breeding animals from the remaining 30% on the basis of clean fleece weight (the "index" method). No selection for fleece weight was practiced on ewes. Seven rams were used in each of the two flocks, and six of the seven were replaced each year by 16-month-old animals from the succeeding drop, the seventh being a year older. Rams used for breeding in the Index flock were significantly higher in clean fleece weight than those of the Visual flock, and were higher, though not always significantly so, in greasy fleece weight. This led to a divergence between the flocks for clean fleece weight (P < 0.05), with an increase of c. 0.05 lb per year per head for the Index animals over the Visual animals. The Index rams were more wrinkly and lighter, on the whole, than the Visual rams, and the wrinkly effect carried over into their offspring with a slight divergence apparent, the Index animals becoming more wrinkled than the Visual (P < 0.05). In fibre diameter there were no differences between selected animals or between flocks. Visual rams tended to have more crimps per inch in their wool, and this was observed in the flocks also, but the divergence was not significant (P > 0.05). Index rams had longer wool than Visual rams, with the difference generally significant within years, and this tendency carried over in a lesser manner to the flocks. Fleece density was generally greater in the Index group, though not usually significantly so. This experiment did not include a randomly bred control flock, but was rather designed to compare two practical methods of selecting rams. Merits of this scheme are discussed in the light of both groups' failure to show increases in fleece weight over the course of the experiment

Effects of inbreeding on four families of Peppin Merinos. II. The influence of inbreeding on age trends

1958 ◽  
Vol 9 (2) ◽  
pp. 252 ◽  
Author(s):  
JM Doney
Keyword(s):  
Reproductive Performance ◽  
Fibre Diameter ◽  
Sampling Procedure ◽  
Age Trends ◽  
Fleece Weight ◽  
Staple Length

The effect of inbreeding on age trends in lambing performance and fleece characters is discussed. Inbred ewes take longer to reach their peak reproductive performance (5 years as against 4 pears for non-inbred ewes) and maximum fleece weight (4–5 years against 3–4 years). For fleece components, age trends and differences between inbred and non-inbred sheep do not appear to be large. In this material, differences between normal and inbred sheep exist only in characters which normally show big changes with increasing age. Dry ewes, in both groups, grow more wool than those rearing a lamb. This appears to be mainly due to the greater staple length in dry ewes. Differences in fibre diameter may be present, but would be masked by the flock sampling procedure.

Survival, growth and wool production of South Australian strong-wool Merino and first-cross Merino lambs from birth to 16 months of age

1983 ◽  
Vol 23 (122) ◽  
pp. 271 ◽  
Author(s):  
DO Kleemann ◽  
MLH South ◽  
CHS Dolling ◽  
RW Ponzoni
Keyword(s):  
Fibre Diameter ◽  
South Australia ◽  
Body Growth ◽  
Carcass Weight ◽  
Research Centre ◽  
Meat Production ◽  
Lower Grade ◽  
Wool Growth ◽  
Lamb Survival ◽  
The Difference

South Australian strong-wool Merino, Poll Dorset and Border Leicester rams were joined to 766 South Australian strong-wool Merino ewes at Minnipa Research Centre, South Australia. The survival, body growth and carcasses of the wether progeny were assessed at 3-4 1/2 months of age. The survival, body growth and wool growth of the ewe progeny were measured from birth to 16 months of age. There were no significant differences between breeds in lamb survival at birth or from 3 to 16 months of age. Merino lambs had the lowest lamb survival between birth and three months of age, the difference being significant (Pt0.05) with Border Leicester x Merino (BL x M) lambs and close to significance (P-0.07) with Poll Dorset x Merino (PD x M) lambs. At three months of age PD x M and BL x M lambs were 19 and 11% heavier respectively than Merino lambs (all differences P < 0.05). Corresponding differences at 16 months of age were 31 and 28% respectively (PD x M and BL x M did not differ significantly from each other; other differences P < 0.05). A greater percentage of BL x M (92 .5) and PD x M (89 .5) lambs grew to a marketable weight (27 kg or greater) than did Merino (63.8) lambs (P < 0.001). Dressing percentage and carcass weights were higher and mean grade scores lower for both PD x M and BL x M breeds compared with the Merino (P < 0.05). PD x M lambs had higher dressing percentages and lower grade scores than BL x M lambs (P < 0.05). Carcass weight, adjusted for differences in fasted liveweight, and carcass grade score, adjusted for differences in carcass weight, were higher in the PD x M breed than either the Merino or BL x M (P< 0.05). BL x M and strong-wool Merino ewe hoggets grew similar amounts of clean wool, and 26-31% more clean wool than the PD x M. There were differences (P< 005) between all breeds for both staple length and fibre diameter, the BL x M having the longest staples and greatest fibre diameter. We concluded that PD x M lambs were superior to the South Australian strong-wool Merinos for meat production, but BL x M and Merinos grew more wool to hogget age. The relative economic merit of the breeds may vary with the prices of the products measured in this study and with the value of the ewes for sale at hogget age.

Selenium supplementation increases wool growth and reduces faecal egg counts of Merino weaners in a selenium-deficient area

2010 ◽  
Vol 50 (7) ◽  
pp. 688 ◽  
Author(s):  
Pietro Celi ◽  
Jeff Eppleston ◽  
Annabel Armstrong ◽  
Bruce Watt
Keyword(s):  
Parasitic Infection ◽  
Fibre Diameter ◽  
Selenium Supplementation ◽  
Ctrl Group ◽  
Merino Sheep ◽  
Significant Difference ◽  
Faecal Egg Counts ◽  
The Difference ◽  
Fleece Weight ◽  
Deficient Area

This paper reports on the effects of selenium supplementation on liveweight (LW), greasy fleece weight (GFW), fibre diameter (FD), impact of parasite infection and plasma glutathione peroxidase (GSH-Px) activity in weaned Merino sheep reared in a selenium-deficient area (blood GSH-Px <40 U/g Hb). At weaning, 208 Merino wethers were assigned to two groups: control (CTRL) and treatment (SEL). The SEL group was injected with 0.5 mL of Deposel, a slow release selenium injection. LW, blood and faecal samples were taken at 6-week intervals over a 24-week period. At the end of the trial the animals were shorn and GFW and FD measurements were taken. The SEL group had significantly higher (P < 0.01) LW compared with the CTRL group at Weeks 6, 12, 18 and 24. There was a significant difference (P < 0.05) in GFW between the SEL and CTRL group, 2.93 and 2.75 kg, respectively. There was no difference in FD between the two groups. A trend (P < 0.06) towards lower faecal egg counts in the SEL group was seen but the difference between the two groups was not significant. As expected, the SEL group had significantly (P < 0.001) higher plasma GSH-Px activity compared with the CTRL group. In conclusion, selenium supplementation in weaned Merino sheep reared in a selenium-deficient area could increase the LW and GFW of the young sheep while perhaps reducing the level of parasitic infection.

Using partial records to identify productive older ewes to retain in the breeding flock to increase the flock net reproduction rate

2014 ◽  
Vol 54 (10) ◽  
pp. 1631 ◽  
Author(s):  
G. J. Lee ◽  
M. A. Sladek ◽  
S. Hatcher ◽  
J. S. Richards
Keyword(s):  
Reproductive Performance ◽  
Selection Criteria ◽  
Genetic Resource ◽  
New South ◽  
Later Life ◽  
Reproduction Rate ◽  
Western Region ◽  
South Wales ◽  
Selection Decisions ◽  
Net Reproduction

The reproductive performance of 7286 ewes from three Merino genetic resource flocks maintained in the central-western region of New South Wales was used to compare the use of fertility and fecundity information and net reproduction information whether recorded early (at 2 and 3 years of age) or later in life (at 4 and 5 years of age) with lifetime performance (at 2–6 years of age) as alternative selection criteria to identify productive older ewes to retain in the breeding flock. While the lifetime net reproduction rate is the best indicator of a ewe’s reproductive performance in later life, producers basing their selection decisions on pregnancy scanning data, which provides information on both fertility and fecundity, can improve the net reproduction rate of their flock by 2% regardless of the base reproduction rate. Despite little difference in likely flock reproduction rates between using early or later life scanning information as the selection criteria, early life performance is the best choice for commercial producers because it provides scope for eliminating twice-dry ewes from the breeding flock early in life, especially when combined with udder examination at marking.

Effect of previous reproductive performance on current reproductive rate in South Australian Merino ewes

2016 ◽  
Vol 56 (4) ◽  
pp. 716 ◽  
Author(s):  
David O. Kleemann ◽  
Simon K. Walker ◽  
Raul W. Ponzoni ◽  
Dennis R. Gifford ◽  
James R. W. Walkley ◽  
...  
Keyword(s):  
Reproductive Performance ◽  
Fixed Effects ◽  
Reproductive Rate ◽  
Breeding Cycle ◽  
Reproduction Rate ◽  
High Fertility ◽  
Lamb Survival ◽  
To Come ◽  
Net Reproduction ◽  
Australian Merino

Reproductive performance of ewes in the current year may be influenced by their performance in the previous year and by the ability of seasonal and management conditions to facilitate full recovery before the next breeding cycle. This possibility was tested by analysing reproductive data from 2100 South Australian Merino ewes mated to Merino rams annually from 1991 to 1997. The model fitted to the data included the fixed effects of previous reproductive performance (PRP) (no lambs born; single or multiple lambs born, none reared; single lambs born, singles reared; multiples born, singles reared; multiples born, multiples reared), age of ewe (2.5, 3.5, 4.5 years), year (1992–1997), bloodline (A, B, L, X) and all two-way interactions. Current-year parameters were net reproduction rate (NRR, lambs weaned of ewes joined) and its components of fertility (ewes lambing of ewes joined), fecundity (lambs born of ewes lambing) and lamb survival (lambs weaned of lambs born). Other parameters were lamb liveweight at weaning per ewe joined and pre-mating liveweight. In addition, repeatability values were calculated across ages for these parameters. NRR was higher in the current year for those groups of ewes that reared lambs in the previous year; this was associated with the highly productive multiple-bearing and -rearing groups having a liveweight at the next mating similar compared to that of groups that did not rear lambs. Repeatability values of 0.27 for NRR and 0.40 for fertility suggest there are genetic and permanent environmental components contributing to the differences observed among the PRP groups for NRR, particularly so for fertility. Selecting ewes after their first lambing opportunity on fertility alone at a rate of 90% would give a non-cumulative increase in fertility of 3.4% at subsequent lambing opportunities. Hence, improvements in the current ewe flock for NRR by graziers managing flocks of the South Australian Merino strain are likely to come from (1) identifying and selecting those ewes of high fertility from early records and (2) attending to management factors impacting on fecundity and lamb survival.

Crossbreeding for lamb production. 1. Survival and growth of first cross lambs

1972 ◽  
Vol 12 (56) ◽  
pp. 234 ◽  
Author(s):  
NM Fogarty
Keyword(s):  
Reproductive Performance ◽  
Agricultural Research ◽  
First Grade ◽  
Stages Of Growth ◽  
Survival And Growth ◽  
The Difference ◽  
Growth Characters

The reproductive performance was studied of two groups each of 450 Peppin Merino ewes joined to Merino, Border Leicester and Dorset Horn rams in two years at the Cowra and Glen Innes Agricultural Research Stations. The survival and growth of the progeny was assessed to weaning with the wether progeny subsequently slaughtered and carcase weight and grade compared. There was little difference in the survival of lambs sired by Border Leicester or Dorset Horn rams and, for both, survival was about three per cent lower than that of Merino lambs at birth and also from birth to weaning. The single crossbred lambs were markedly heavier than the single Merino lambs at all stages of growth, but the difference between twins was considerably reduced, which gave sigrdicant breed X type of birth interactions for all growth characters examined. The Dorset X Merino lambs were 2.5 per cent heavier at weaning and had three per cent heavier carcases than the Border X Merino lambs. The heavier carcas weights for the Dorset X Merino lambs was mainly due to higher dressing percentages. There were significantly more first grade carcases amongst the crossbred than the Merino lambs, with a higher proportion of Dorset X Merino carcases in the first grade than Border X Merino.

Hybrid vigour and lamb production. 2. Effects on survival and growth of first-cross lambs, and on wool and body measurements of hogget ewes

1978 ◽  
Vol 18 (95) ◽  
pp. 753 ◽  
Author(s):  
BJ McGuirk ◽  
ME Bourke ◽  
JM Manwaring
Keyword(s):  
Agricultural Research ◽  
Fibre Diameter ◽  
Fibre Length ◽  
Research Station ◽  
Hybrid Vigour ◽  
Body Measurements ◽  
South Wales ◽  
Survival And Growth ◽  
Lamb Survival ◽  
Fleece Weight

In an experiment at Cowra Agricultural Research Station, New South Wales, five drops of Border Leicester (BB), Merino (MM), Border Leicester x Merino (BM) and Merino x Border Leicester (MB) lambs have been compared to estimate hybrid vigour effects on lamb survival and growth, and on the wool and body measurements of ewe hoggets. Hybrid vigour has been estimated as the percentage superiority of the crossbreds 1/2(MB + BM) over the average of the purebred 1/2(BB + MM) flocks. Hybrid vigour was observed for lamb survival, with the crossbreds superior by 10 per cent in lambs weaned per lamb born (P < 0.05). The crossbred lambs were also heavier at birth (4 per cent) and weaning (6 per cent) and crossbred wether lambs were 11 per cent heavier at slaughter (all P < 0.05). The crossbred ewes were significantly superior to the average of the purebred flocks in both greasy (8 per cent) and clean fleece weight (12 per cent), liveweight (12 per cent) and chest depth (5 per cent) (all P < 0.05). There was no evidence that the crossbreds were superior in any component of wool production per unit area of the skin ; fibre length, fibre diameter or follicle density. Other evidence from this experiment indicates that the breeds and crosses differ in their susceptibility to pneumonia and that there may be heterosis for resistance. This situation could give rise to heterosis for production characters and the heterosis estimates obtained may only be applicable to first-cross flocks derived from Border Leicester studs which are susceptible to pneumonia. Lamb survival to weaning was higher for purebred Merinos (88 per cent) than for purebred Border Leicesters (73 per cent, P < 0.05). The Border Leicester lambs were heavier at all ages and in all years, although the magnitude of their superiority varied significantly between years (P < 0.05). This breed x year interaction was also significant for clean fleeca weight, but the average production of the two groups was similar over the five years. Variation, measured as the coefficient of variation, was generally lower within the crossbred flocks for those characters for which hybrid vigour effects were observed, but these differences were not statistically significant.

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