Reproductive performance of ewe lambs: genetic correlation with weaning weight and subsequent reproductive performance

1976 ◽  
Vol 16 (80) ◽  
pp. 321 ◽  
Author(s):  
R Barlow ◽  
CJ Hodges
Keyword(s):  
Genetic Correlation ◽  
Reproductive Performance ◽  
Agricultural Research ◽  
Reproductive Rate ◽  
Research Station ◽  
Weaning Weight ◽  
Net Reproductive Rate ◽  
Ewe Lambs ◽  
Ewe Lamb ◽  
Selection For

The reproductive performance of Merino ewe lambs was examined in flocks with different selection histories for growth to weaning and net reproductive rate. These ewes were drawn from selection flocks maintained at the Agricultural Research Station, Trangie. There was evidence of a positive genetic correlation between weaning weight and reproductive performance of ewe lambs. Selection for weaning weight had a significant effect on the percentage of ewes lambing (P < 0.05). This appeared to be a function of a higher level of fertility (P <0.05) and a higher proportion of ewes mating (n.s.). The proportion of ewes apparently in oestrus during a 39 day teasing period, prior to joining, was significantly influenced by selection for weaning weight (P < 0.05). Simultaneous selection for increased net reproductive rate, weaning weight and clean fleece weight did not result in higher ewe lamb performance than that achieved by selection for increased weaning weight alone. No conclusion could be drawn from these data about the correlation between net reproductive rate and reproductive performance of ewe lambs.

Skin folds and Merino breeding. 2. The relative influence of the ram and the ewe on fertility and perinatal lamb mortality in flocks selected for and against skin fold

1965 ◽  
Vol 5 (18) ◽  
pp. 236 ◽  
Author(s):  
RB Dun ◽  
BA Hamilton
Keyword(s):  
Birth Weight ◽  
Genetic Correlation ◽  
Reproductive Performance ◽  
Maternal Effect ◽  
Reproductive Rate ◽  
Independent Data ◽  
Net Reproductive Rate ◽  
Skin Fold ◽  
Cent Mortality ◽  
The Difference

Reciprocal matings were carried out between the Trangie Folds Plus and Folds Minus selection Aocks in March 1961 and 1962. Folds Minus rams were more fertile than Folds Plus rams as shown by ewes lambing per insemination (72 per cent versus 48 per cent, P&0.01) and by incidence of twinning per ewe lambing (57 per cent versus 34 per cent, P<0.05). Folds Plus and Folds Minus ewes showed a similar reproductive performance if mated to the same rams. 236 There was a 17 per cent mortality in single lambs born to Folds Plus ewes compared with 4 per cent (P<0.05) for single lambs born to Folds Minus ewes. This increased mortality was caused by dystocia in association with relative oversize of the lamb. A positive genetic correlation of 0.32 � 0.21 between fold score and corrected birth weight was calculated using independent data. The mortality of twin lambs born to Folds Minus ewes was higher than for Folds Plus ewes (18 per cent versus 11 per cent). There was a maternal effect on the birth weight of twins, which were relatively much heavier from Folds Plus ewes. Approximately 80 per cent of the difference in net reproductive rate between the Folds Minus and Folds Plus flocks was explained on the basis of infertility of Folds Plus rams and excessively heavy birth weights of Folds Plus lambs.

Single female offspring born to primiparous ewe-lambs are lighter than those born to adult multiparous ewes but their reproduction and milk production are unaffected

2012 ◽  
Vol 52 (7) ◽  
pp. 552 ◽  
Author(s):  
M. F. P. Loureiro ◽  
S. J. Pain ◽  
P. R. Kenyon ◽  
S. W. Peterson ◽  
H. T. Blair
Keyword(s):  
Milk Production ◽  
Reproductive Performance ◽  
Crude Protein ◽  
Female Offspring ◽  
Productive Performance ◽  
Single Female ◽  
Ewe Lambs ◽  
Ewe Lamb ◽  
Generation Offspring

Little is known about the long-term impacts of selecting progeny born to ewe-lambs (EL) as replacements. This study investigated whether being born to a ewe-lamb affected the liveweight, milk production and reproductive performance of the offspring to 3 years of age in comparison with those born to adult multiparous ewes. Twenty-seven and 28 single-born Romney ewe progeny (G1) were born to either EL or to adult ewes (AE), respectively. Offspring born to ewe-lambs (ELG1) were lighter (P < 0.001) at birth and up to 12 months of age compared with offspring born to adult ewes (AEG1). Reproductive performance of AEG1 and ELG1 did not differ in regards to puberty attainment, pregnancy rate and number of fetuses. First lactation milk production, fat, crude protein, total protein, casein, lactose and total solids yield did not differ (P > 0.05). The second generation offspring born to ELG1 and AEG1 did not differ in birthweight in the first parity, but it did differ in the second parity and those lambs born to ELG1 were heavier from birth to weaning compared with those lambs born to AEG1. Combined, these results indicate, in the animals used in our study that productive performance of ewes born to EL does not differ to 3 years of age to that of ewes born to AE.

scholarly journals Abortion and Lamb Mortality between Pregnancy Scanning and Lamb Marking for Maiden Ewes in Southern Australia

Animals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 10
Author(s):  
Thomas Clune ◽  
Amy Lockwood ◽  
Serina Hancock ◽  
Andrew N. Thompson ◽  
Sue Beetson ◽  
...  
Keyword(s):  
Cohort Study ◽  
Reproductive Performance ◽  
Important Contributor ◽  
Ewe Lambs ◽  
Ewe Lamb ◽  
Overall Mortality

The contribution of abortions to the overall mortality of lambs born to maiden (primiparous) ewes in Australia remains unclear. This cohort study aimed to quantify abortion and lamb mortality for ewe lambs and maiden Merino two-tooth ewes. Lamb mortality from pregnancy scanning to marking were determined for 19 ewe lamb and 11 Merino two-tooth ewe flocks across southern Australia. Average lamb mortality from scanning to marking was 35.8% (range 14.3–71.1%) for the ewe lambs and 29.4% (range 19.7–52.7%) for the two-tooth ewes. Mid-pregnancy abortion was detected in 5.7% of ewes (range 0–50%) in the ewe lamb flocks and 0.9% of ewes (range 0–4.4%) in the two-tooth ewe flocks. Mid-pregnancy abortion affecting ≥2% of ewes was observed in 6/19 ewe lamb flocks and 2/11 two-tooth ewe flocks. Lamb mortality from birth to marking represented the greatest contributor to foetal and lamb mortality after scanning, but mid-pregnancy abortion was an important contributor to lamb mortality in some ewe lamb flocks. Variability between the flocks indicates scope to improve the overall reproductive performance for maiden ewes by reducing foetal and lamb losses. Addressing mid-pregnancy abortion may improve the reproductive performance in some flocks.

Response of additional ewe lamb liveweight during gestation on birth and weaning weight of offspring and liveweight of the ewe lamb at weaning

2010 ◽  
Vol 50 (6) ◽  
pp. 528 ◽  
Author(s):  
N. M. Schreurs ◽  
P. R. Kenyon ◽  
F. J. Mulvaney ◽  
P. C. H. Morel ◽  
D. M. West ◽  
...  
Keyword(s):  
Management Practices ◽  
Analytic Approach ◽  
Gestation Period ◽  
Third Trimester ◽  
Management Options ◽  
Weaning Weight ◽  
Early Gestation ◽  
Positive Effects ◽  
Ewe Lambs ◽  
Ewe Lamb

Increasing the liveweight of ewe lambs during gestation may have positive effects on lamb birthweight and weaning weight and also on ewe lamb liveweight at weaning. Specific times during the gestation period of the ewe lamb may be more responsive to improved nutrition and increases in liveweight. The objective of this work was to use a meta-analytic approach to investigate the effects of ewe lamb liveweight at mating and during pregnancy on lamb birth and weaning weights, and the ewe lamb’s liveweight at weaning. Increasing ewe lamb liveweight in early gestation and in particular before mating gave the greatest increases in the birth and weaning weight of the lambs, and also of the ewe lamb’s liveweight at weaning compared with increasing liveweight in the second and third trimester of gestation. This indicates that management practices for ewe lambs that generate higher liveweight at mating are likely to result in increased lamb survival, higher weaning percentages, greater lamb weaning weights and create rising 2-year-old ewes with better liveweight for mating in the subsequent season. Compared with ewe lambs that gave birth and reared singletons to weaning, those ewe lambs that gave birth to twins and reared twins had greater increases in lamb birthweights, lamb weaning weights and ewe lamb weights at weaning for each extra kilogram of ewe lamb liveweight during gestation. For ewe lambs, especially those that birth and rear twins, management options that increase the pre-mating weights will have the greatest response in lamb birthweight, weaning weight and liveweight of the ewe lamb itself at weaning.

Effect of timing of exposure to vasectomised rams and ewe lamb body condition score on the breeding performance of ewe lambs

2012 ◽  
Vol 52 (7) ◽  
pp. 471 ◽  
Author(s):  
L. M. Cave ◽  
P. R. Kenyon ◽  
S. T. Morris
Keyword(s):  
Body Condition ◽  
Reproductive Performance ◽  
Body Condition Score ◽  
Breeding Period ◽  
Breeding Performance ◽  
Ewe Lambs ◽  
Percentage Points ◽  
Condition Score ◽  
Ewe Lamb ◽  
Timing Of Exposure

The aims of this study were to examine the effects of exposing Romney ewe lambs (8–9 months of age) to vasectomised rams across three studies in the February–March period and to determine the influence of body condition score (CS) in two of the studies on their reproductive performance. In all studies, ewe lambs exposed to vasectomised rams had greater (P < 0.05) conception rates to the first 17 days of breeding by 6–12 percentage points. However, Studies 2 and 3 indicated that exposing ewe lambs to vasectomised rams did not increase (P > 0.05) the percentage of ewe lambs conceiving over a 34-day breeding period, nor did it increase the number of fetuses per ewe lamb presented for breeding. The results of Study 1 suggest that there is a limit to how early in the year ewe lambs can be exposed to vasectomised rams. In Study 2, a greater (P < 0.05) percentage of Teased CS 2.0 or 2.5+ ewe lambs conceived during the first 17 days of breeding than those which were Unteased. This effect was not observed (P > 0.05) in CS 1.5 ewe lambs. In Study 3, a greater (P < 0.05) percentage of CS 2.5+ ewe lambs conceived over the 34-day breeding period than ewe lambs of lower CS. In Studies 2 and 3, ewe lambs with a CS of 2.5+ had a greater (P < 0.05) number of fetuses per ewe lamb presented for breeding than CS 1.5 ewe lambs. In conclusion, exposing ewe lambs to vasectomised rams in the late February or March period increased the proportion of ewe lambs successfully bred in the first 17 days of breeding. Further achieving higher CS and heavier liveweights of ewe lambs at breeding should result in improved reproductive performance.

Skin folds and Merino breeding. 8. Fertility of individual rams in flocks selected for high and low skin fold

1969 ◽  
Vol 9 (37) ◽  
pp. 147 ◽  
Author(s):  
BJ McGuirk
Keyword(s):  
Artificial Insemination ◽  
Agricultural Research ◽  
New South ◽  
New South Wales ◽  
Research Station ◽  
South Wales ◽  
Skin Fold ◽  
Single Character ◽  
Lower Fertility ◽  
Selection For

Single character selection flocks-Folds Plus (selection for high fold score) and Folds Minus (selection for low fold score) were established in 1951 from a Peppin Merino flock at Trangie Agricultural Research Station, New South Wales. For the period 1951 to 1966, 25 per cent of rams selected for the Folds Plus flock were rejected following semen examination before joining, compared to only three per cent of Folds Minus rams (P<0.05). The fertility of individual rams in the two flocks has been estimated from the lambing performance of the ewes to which they were mated in the period 1951 to 1963. Averaged over the twelve joinings, a higher proportion of ewes mated to Folds Minus rams lambed following both artificial insemination (53 v. 45 per cent) and paddock joinings (57 v. 47 per cent). The lower fertility of the Folds Plus rams was not due to a higher proportion of completely infertile rams.

Early reproductive losses are a major factor contributing to the poor reproductive performance of Merino ewe lambs mated at 8–10 months of age

2014 ◽  
Vol 54 (6) ◽  
pp. 762 ◽  
Author(s):  
B. L. Paganoni ◽  
M. B. Ferguson ◽  
S. Fierro ◽  
C. Jones ◽  
G. A. Kearney ◽  
...  
Keyword(s):  
Reproductive Performance ◽  
First Record ◽  
Reproductive Rate ◽  
Ovulation Rate ◽  
Corpora Lutea ◽  
Mating Period ◽  
Breeding Values ◽  
Pregnancy Failure ◽  
Ewe Lambs ◽  
Reproductive Losses

The reproductive performance of Merino ewe lambs is lower than that achieved by mature ewes and is highly variable. It is likely that embryo loss represents a major source of reproductive wastage in Merino ewe lambs, but to our knowledge no studies have attempted to determine when the major reproductive losses occur or identify predisposing factors that are likely to lead to high rates of pregnancy failures in ewe lambs. After characterising where reproductive losses occurred in Merino ewe lambs mated at 8–10 months of age, we tested the hypothesis that pregnancy failure in ewe lambs is influenced by nutrition and liveweight change around conception and the genetic potential for growth of the ewe lamb. Two-hundred and twenty-four Merino ewe lambs born from 10 sires with Australian Sheep Breeding Values were teased for 14 days using vasectomised rams, and then fed two different diets for 68 days during mating. All ewe lambs were weighed and the appearance of crayon marks on their rump was recorded most days. Blood samples for progesterone assay were collected on Days 5, 12 and 17 after the first record of a crayon mark. Ultrasonography using a trans-rectal probe was used to measure the number of corpora lutea present, as a proxy for ovulation rate, 9 days after the first record of a crayon mark during the mating period. A further trans-rectal ultrasonography was undertaken 30 days after marking from the entire ram to determine pregnancy status and count the number of embryos. Over the entire mating period 54% of ewe lambs were pregnant with 66 fetuses per 100 ewes mated. The average ovulation rate was 150% however up to 84% of this potential was lost by weaning and the major contributor to this apparent deficit was the loss that occurred during the first 17 days after mating. Pregnancy failure was not significantly related to nutrition or liveweight change during mating however, there were significant differences in pregnancy failure between different sire groups. Pregnancy failure was significantly less for ewe lambs from sires with higher breeding values for weight and fat at post-weaning age (8–10 months). Only 60% of ewe lambs had achieved puberty when rams were introduced and only 83% by 35 days after mating. In addition, almost half of the ewe lambs that were mated for the first time during the first 35 days after rams were introduced, but failed to get pregnant, then seemed to skip a cycle or did not cycle again before the end of the 68-day mating period. Liveweight at introduction of entire rams was positively related to fertility, ovulation rate and reproductive rate. This study confirms that selection of sires with higher breeding values for post-weaning weight and fat will increase the fertility and reproductive rate of Merino ewe lambs mated at 8–10 months. This response is due in part to enhancing the onset of puberty and increasing the proportion of ewe lambs cycling at the start of mating and reducing pregnancy failure.

The comparative reproductive performance of polled and horned Merino rams

1965 ◽  
Vol 5 (17) ◽  
pp. 102
Author(s):  
RB Dun ◽  
DS Douglass
Keyword(s):  
Reproductive Performance ◽  
Agricultural Research ◽  
Research Station ◽  
Agricultural Research Station

The reproductive performance of genetically polled and horned Merino rams has been compared at Trangie Agricultural Research Station and at two commercial properties-one from the Trangie and one from the Wentworth district of N.S.W. There was no consistent result although statistically significant differences were recorded favouring one or other type of ram in a particular season. Absence or presence of horns, as determined by the poll gene, had little effect overall on the reproductive performance of the Merino ram.

Effect of selection for leanness on overall reproductive performance in Large White sows

1995 ◽  
Vol 61 (3) ◽  
pp. 561-564 ◽  
Author(s):  
J. B. Gaughan ◽  
R. D. A. Cameron ◽  
G. McL. Dryden ◽  
M. J. Josey
Keyword(s):  
Birth Weight ◽  
Reproductive Performance ◽  
Live Weight ◽  
The Other ◽  
Large White ◽  
Weaning Weight ◽  
Weaned Piglet ◽  
Selection For ◽  
Weight Number ◽  
M 14

AbstractReproductive records from 1072 Large White sows (3589 litters) were used to examine the effect ofbackfat depth (Bd) and live weight (Lw) at selection on first litter and lifetime reproductive performance. The variables investigated included mating age, total piglets born, total born alive, piglet birth weight, number weaned, piglet weaning weight, weaning to remating period and number of litters produced. Using backfat depth, sows were categorized into three groups: L, 9 to 13 mm; M, 14 to 16 mm; and F, ≥17 mm. Bd had no significant effect (P > 0·05) on the measured traits for the sows grouped by fat at first parity. When lifetime reproductive data were analysed, the L group had fewer litters (P < 0·05), and weaned fewer pigs (P < 0·01) than either the M or F group. The birth weight for piglets from L sows were significantly higher (P < 0·05) than for piglets from the other groups. The data suggest that the reproductive performance of L sows is not as good as that of M or F sows.

Selection for crimp frequency in the wool of Merino sheep. 1. Direct response to selection

1967 ◽  
Vol 7 (29) ◽  
pp. 552 ◽  
Author(s):  
GE Robards ◽  
WA Pattie
Keyword(s):  
First Generation ◽  
Agricultural Research ◽  
Steady Increase ◽  
Research Station ◽  
Direct Response ◽  
Satisfactory Explanation ◽  
Gene Frequencies ◽  
Selection For ◽  
Contrast Response ◽  
Large Response

Two selection flocks consisting of 100 ewes mated to five rams were established at the Agricultural Research Station, Trangie, in 1950. One flock was selected for high crimp frequency (Crimps Plus), and the other for low crimp frequency (Crimps Minus). Responses in these flocks were measured against a randomly selected control flock maintained in the same environment and with the same management. The Crimps Plus flock showed a steady increase in crimp frequency with realized heritabilities of 0.46 � 0.14 for ewes and 0.38 � 0.15 for rams, calculated over five generations of selection. In contrast, response in the Crimps Minus flock was not linear as there was a large response in the first generation but very little after that. Dam-offspring heritabilities calculated for sheep entering the flocks after the first generation were 0.40 � 0.14 for the Crimps Minus flock and 0.47 � 0.15 for the Crimps Plus flock. It is suggested that prior selection in the base population may have resulted in unequal gene frequencies, and hence the reduction of response in the Crimps Minus flock. No satisfactory explanation could be given for the large response to the first generation of selection in this flock.

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