scholarly journals The role of reproductive loss on flock performance – a comparison of nine industry flocks

2021 ◽  
Author(s):  
Paul R Shorten ◽  
Sara J Edwards ◽  
Jenny L Juengel
Keyword(s):  
Growth Rate ◽  
Reproductive Performance ◽  
Survival Probability ◽  
Ovulation Rate ◽  
Embryo Survival ◽  
Ewe Lambs ◽  
Reproductive Loss ◽  
Lamb Survival ◽  
Lamb Growth

Abstract The reproductive performance of a sheep flock is dependent on a multitude of complex interacting factors. Attaining optimal flock performance requires information about how the reproductive steps are linked and relate to readily available measurements of the state of the flock. The goal was to use data from nine commercial flocks (greater than 300,000 records) to investigate and model the key reproductive steps affecting flock reproductive performance. We also developed a maximum-likelihood based methodology to predict flock ovulation rate based on measurements of the number of fetuses at mid-pregnancy (detected by ultrasound-scanning). The model was used to determine how changes in pre-mating liveweight, age, predicted ovulation rate, number of fetuses at mid-pregnancy, lamb survival and lamb growth rate affect the total lamb liveweight at weaning per ewe exposed to the ram in each flock. The data from the commercial flocks were also used to investigate the role of ewe age and pre-mating liveweight on each reproductive step. Sensitivity analyses were conducted to identify the key reproductive steps affecting flock reproductive performance, with a focus on understanding how these steps vary between flocks. The elasticity for embryo survival was 60% of that for lamb survival for these flocks and the elasticities for ovulation rate were highly variable between flocks (0.16 − 0.50 for mature ewes). This indicates that ovulation rate was near-optimal for some flocks, whereas there was potential to significantly improve flock performance in suboptimal flocks. The elasticity for ewe pre-mating liveweight was highly variable between flocks (-0.03 to 0.84 for mature ewes and -0.18 to 1.39 for ewe lambs), indicating that pre-mating liveweight ranged from optimal to suboptimal between flocks. For these suboptimal farms, opportunity exists to increase flock performance through improved management of ewe pre-mating liveweight. Reproductive loss was significantly greater in ewe lambs than mature ewes, although the difference is dependent on the stage of reproduction and flock. Predicted ovulation rate was 25% lower for ewe lambs and there was a 30% relative decrease in the predicted embryo survival probability from ovulation to scanning for ewe lambs. There was a 10% relative decrease in lamb survival probability from birth to weaning for ewe lambs and lamb growth rate was 25% lower for ewe lambs.

scholarly journals The effect of reproductive loss on the performance of a research flock

2020 ◽  
Vol 98 (3) ◽  
Author(s):  
Paul R Shorten ◽  
Sara J Edwards ◽  
Jenny L Juengel
Keyword(s):  
Reproductive Performance ◽  
Ovulation Rate ◽  
Relative Importance ◽  
Sheep Flock ◽  
Embryo Survival ◽  
Reproductive Loss ◽  
Selection For ◽  
Lamb Survival ◽  
And Performance

Abstract The reproductive performance of a sheep flock is dependent on a multitude of complex interacting factors. Achieving optimal flock performance requires knowledge of the reproductive steps and how these are linked and related to available measurements of the state and performance of the flock. The goal was to use previously collected data from a research flock that had undergone selection for fecundity (11,369 lambing records), to model the key reproductive steps affecting flock reproductive performance. The model was used to investigate how changes in liveweight, age, ovulation rate, number of fetuses at midpregnancy, number of lambs born, and birthweight affect the number of lambs weaned and the weaning weight of each lamb in this flock. The data available from the research flock were used to parameterize models of each reproductive step and assess the role of ewe age and premating liveweight on each reproductive step. These models were then linked together as a simulation tool to assess the role of different parameters on flock reproductive performance, which was defined as the total weight of lambs weaned per ewe exposed to the ram. Flock elasticities were calculated that characterize the relative importance of the effect of average premating ewe liveweight (0.81), average ovulation rate (0.33), variance in ovulation rate (−0.095), embryo survival (0.72), lamb survival (1.03), conception failure (0.35), and average ewe age (0.056) on the total kilograms of lamb liveweight at weaning per ewe exposed to the ram. The largest elasticity for lamb survival indicated that a 1% increase in lamb survival is expected to have a 1.03% increase in the total kilograms of lamb liveweight at weaning per ewe exposed to the ram in this flock. Assuming similar costs, interventions to increase lamb survival for this flock will provide the largest increase in the total kilograms of lamb liveweight at weaning per ewe exposed to the ram, which is a key metric of flock performance.

A comparison of ovulation rate and late embryonic mortality in ewe lambs and ewes and the rôle of late embryo loss in ewe lamb subfertility

1996 ◽  
Vol 62 (1) ◽  
pp. 79-83 ◽  
Author(s):  
N. F. G. Beck ◽  
M. C. G. Davies ◽  
B. Davies
Keyword(s):  
Reproductive Performance ◽  
Significant Contribution ◽  
Reproductive Function ◽  
Embryonic Mortality ◽  
Ovulation Rate ◽  
Embryo Survival ◽  
Ewe Lambs ◽  
Ewe Lamb ◽  
Late Embryo

AbstractAn investigation was conducted to compare late embryonic losses in ewe lambs and ewes and to determine the effect of inducing embryonic mortality on day 15 of pregnancy on reproductive function in ewe lambs. Ovulation rate and embryo survival were determined, at 15 and 30 days after mating, in a total of 83 ewe lambs and 67 ewes. Ovulation rate was lower, at spontaneous oestrus, in ewe lambs (1·07) than in ewes (1·25; P < 0·05). There was no difference in embryo survival at day 15, as 79% of ewe lambs and 80% of ewes contained expanded conceptuses. However, embryo survival was lower in ewe lambs (69%) than ewes (88%) at day 30 (P < 0·05). Embryonic mortality was induced in an additional 18 ewe lambs with an intrauterine injection of colchicine on day 15 post mating. Four of these animals had normal length oestrous cycles, six had inter-oestrus intervals ranging from 22 to 35 days and eight did not return to oestrus. Overall, the results of this study demonstrate that low ovulation rate and late embryonic losses make a significant contribution to subfertility in ewe lambs. Moreover, conceptus death is associated with luteal persistence, which may reduce reproductive performance by preventing remating.

scholarly journals Ewe reproductive performance and growth rate of suckling-lambs on endophyte-infected perennial ryegrass pasture

1999 ◽  
Vol 7 ◽  
pp. 19-26
Author(s):  
R.H. Watson ◽  
R.G. Keogh ◽  
M.F. Mcdonald
Keyword(s):  
Growth Rate ◽  
Perennial Ryegrass ◽  
Reproductive Performance ◽  
Growth Rates ◽  
Ovulation Rate ◽  
Grazing Management ◽  
One Year ◽  
Lamb Growth

Two groups (n=39) of Romney breeding ewes were maintained under the same grazing management on either endophyte-infected (E+) or endophytefree (E-) perennial ryegrass pasture for two years (1997-1998) following a one-year equilibration period. The ewes were naturally mated in March each year and ovulation rate at 1st mating was measured, and conception and the number of lambs born and weaned were recorded. All ewes were weighed monthly and lamb growth rates were determined between birth and weaning. Mean mating date was delayed by 1.8 days (P

Effect of premating shearing on reproductive performance in ewe lambs after oestrus synchronization

1991 ◽  
Vol 116 (1) ◽  
pp. 135-138
Author(s):  
J. V. O'Doherty ◽  
T. F. Crosby
Keyword(s):  
Growth Rate ◽  
Litter Size ◽  
Reproductive Performance ◽  
Medroxyprogesterone Acetate ◽  
Conception Rate ◽  
Factorial Experiment ◽  
Ewe Lambs ◽  
Significant Difference ◽  
Lamb Growth

SUMMARYOne hundred and fifty-four, March-born, lowland ewe lambs, on the Lyons Estate farm, were allocated to a 2×2 factorial experiment. In September 1987, half were shorn and 1 month later the lambs were treated with intravaginal sponges, containing either 60 mg medroxyprogesterone acetate or 40 mg fluorogestone acetate, for 12 days. Following sponge removal, ewes were mated to fertile rams at a ram: ewe ratio of 1:6. There was no significant difference in reproductive performance between the two progestagen treatments (P > 0·05). Premating shearing increased (P < 0·01) conception rate and reduced the percentage of barren ewes (P < 0·01) but there was no effect on litter size. Time of gestation following shearing was increased (P < 0·01) by 1·24 days. Lamb growth rate up to weaning was not affected by the shearing treatment. The results of this trial indicate positive advantages of premating shearing of ewe lambs.

A note on the reproductive performance of greyface ewes in moderately fat and very fat condition at mating

1984 ◽  
Vol 38 (2) ◽  
pp. 305-307 ◽  
Author(s):  
S. M. Rhind ◽  
R. G. Gunn ◽  
J. M. Doney ◽  
I. D. Leslie
Keyword(s):  
Reproductive Performance ◽  
Survival Rates ◽  
Ovulation Rate ◽  
Embryo Survival ◽  
Expected Time ◽  
Lambing Rate

ABSTRACTOestrous activity, ovulation rates and embryo survival rates were investigated in Border Leicester × Scottish Blackface (Greyface) ewes with condition scores of approximately 2·75 (moderately fat) or 3·5 (very fat) at mating. Four of a group of 20 very fat ewes failed to show oestrus at the expected time. Very fat ewes had a higher mean ovulation rate (3·36 v. 2·33; P < 0·05) but a slightly lower potential lambing rate (1·10 v. 1·42 lambs born per ewe put to ram) than the moderately fatewes.

scholarly journals Effects of ewe live weight and age on reproductive performance, lamb growth, and survival in Central Anatolian Merino sheep

2015 ◽  
Vol 58 (2) ◽  
pp. 451-459 ◽  
Author(s):  
A. H. Aktaş ◽  
Ş. Dursun ◽  
Ş. Doğan ◽  
Z. Kiyma ◽  
U. Demirci ◽  
...  
Keyword(s):  
Growth Rate ◽  
Reproductive Performance ◽  
Birth Rate ◽  
Live Weight ◽  
Fertility Rate ◽  
Multiple Birth ◽  
Growth And Survival ◽  
Merino Sheep ◽  
Lamb Growth ◽  
Selection Of

<p><strong>Abstract.</strong> The aim of this study was to evaluate the effects of premating ewe weight and age on ewe reproductive performance, lamb growth and survival in Central Anatolian Merino (CAM) sheep. <br><br> The trial included 4935 ewes and 5548 lambs from 23 breeder flocks in Eskişehir Province. The live weights (LWs) and ages of the ewes were recorded 1 week before the mating season. The number of lambs born, fertility rate, multiple birth rate (MBR), and lamb survival rate (SR) at days 75 and 120 were determined. The effects of the LW and age of the ewe were found to be important for the reproductive performance of ewes and for the lamb's growth rate (<i>P</i> < 0.05–0.001). Ewe MBRs and the birth weight (BW) and LW of the lambs at days 75 and 120 increased proportionally with the increase in LW in ewes prior to mating. The fertility rate and MBR were lower (<i>P</i> < 0.05–0.001) in 1.5-year-old ewes than in older ewes. However, lambs' SR at days 75 and 120 were not affected by the premating LW and age of the ewe. In summary, a better reproductive performance and lamb growth rate in CAM flocks may be achieved by the selection of breeding ewes from ewes weighing more than 60 kg.</p>

Fat lamb studies in Victoria. II. The interaction between pre- and post-natal planes of nutrition on the production of wool and lambs by crossbred sheep

1957 ◽  
Vol 8 (5) ◽  
pp. 471 ◽  
Author(s):  
JC Papadopoulos ◽  
TJ Robinson
Keyword(s):  
Growth Rate ◽  
Ewe Lambs ◽  
Wool Growth ◽  
Breed Difference ◽  
Plane Group ◽  
Nutritional Environment ◽  
The Mean ◽  
Lamb Growth ◽  
Pregnant Mare Serum Gonadotrophin ◽  
Restricted Feed Intake

The interactions between two planes of pre- and post-natal nutrition of grazing ewes and the level of fertility on: ( a ) birth weight of the lamb, ( b ) its subsequent growth rate, and ( c ) wool growth, were determined in 140 crossbred ewes (52 Romney Marsh X Merino, 88 Border Leicester X Merino). The effectiveness of pregnant mare serum gonadotrophin (PMS) , injected on the 12th to 14th day of the oestrous cycle, for raising fertility ' was also investigated. Romney cross ewes had commenced their breeding season before January 21, a t least 3 weeks earlier than Border Leicester cross ewes. They lambed correspondingly earlier. The overall lambing percentage was very high (139 per cent.). PMS had no significant effect. There was no breed difference. Low- and high-plane ewes gained an average of 20 and 54 lb respectively during pregnancy. The mean weight of the conceptus was 34 lb (twins 39 Ib, singles 25 lb). Hence low-plane ewes lost an average of 14 lb body tissue as compared with a gain of 20 lb by high-plane ewes. Mean birth weights of lambs - single and multiple pregnancies - from the two nutritional groups were indistinguishable. Lamb losses and lambing troubles were fewer in the low--plane group. There was no interaction of pre- and post-natal nutrition on subsequent lamb growth rate. Post-natal plane of nutrition, sex of the lamb, and number reared all had highly significant effects on lamb growth rate. There were also significant interactions between plane of nutrition of the ewe and number of lambs reared and sex of lambs. Wether lambs needed the best possible nutritional environment fully to exhibit their inherent superior growth rate over ewe lambs. Restricted feed intake either in pregnancy or in lactation reduced wool growth to approximately the same degree. Although birth and weaning weights were affected by the number of lambs born and reared, wool production of the dam was not affected.

scholarly journals Effects of flush feeding strategy before breeding on reproductive performance of modern replacement gilts: impacts on ovulation rate and litter traits

2020 ◽  
Vol 98 (6) ◽  
Author(s):  
André L Mallmann ◽  
Lidia S Arend ◽  
Gabriela S Oliveira ◽  
Ana P G Mellagi ◽  
Rafael R Ulguim ◽  
...  
Keyword(s):  
Litter Size ◽  
Reproductive Performance ◽  
Feeding Strategy ◽  
Early Embryo ◽  
Ovulation Rate ◽  
Breeding Cycle ◽  
Corpora Lutea ◽  
Embryo Survival ◽  
Estrous Cycles ◽  
Litter Traits

Abstract AbstractThe effects of two feed levels offered during two estrous cycles before insemination were evaluated on the reproductive performance of gilts. A total of 93 gilts (PIC Hendersonville, TN) were individually housed and manually fed twice a day with 2.1 or 3.6 kg/d of a corn and soybean meal-based diet (3.15 Mcal ME/kg and 0.64% standardized ileal digestible lysine), during two estrous cycles before breeding (cycle 1, between first and second estrus; cycle 2, between second and third estrus). Gilts were weighed at the beginning of the experiment, at second and third estrus, and at slaughter (30.2 ± 1.2 d of gestation). Follicles were counted at second estrus, and the embryo-placental units and the corpora lutea were individually counted, measured, and weighed at slaughter. Gilts fed 3.6 kg/d had greater BW gain during cycle 1 and cycle 2 (P &lt; 0.001; + 9.8 kg and + 10.0 kg, respectively) becoming heavier at second and third estrus (P &lt; 0.001). At second estrus, gilts fed 3.6 kg/d had 1.6 more medium-large follicles (P = 0.074) but no difference in follicle size (P = 0.530) was observed. Gilts fed 3.6 kg/d in cycle 1 or cycle 2 had a greater ovulation rate at third estrus (P &lt; 0.016) than those receiving 2.1 kg/d. Also, 3.6 kg/d in cycle 2 increased early embryo mortality (P = 0.006; 2.3 vs. 1.1 dead embryos) and consequently reduced total embryo survival (P = 0.002; 84.6 vs. 90.1%). Gilts fed 3.6 kg/d during cycle 1 had two more total embryos (P &lt; 0.001; 17.2 vs. 15.1) and two more vital embryos on day 30 (P &lt; 0.001; 16.7 vs. 14.5) in comparison with gilts fed 2.1 kg/d. The coefficient of variation for placental length was greater for gilts fed 3.6 kg/d during cycle 1 (P = 0.003). No further significant effects of feeding levels were observed on embryo and placental traits (P ≥ 0.063). These results suggest that the feeding level during the first cycle after pubertal estrus is crucial to set ovulation rate and potential litter size for breeding at next estrus. However, flush feeding gilts before insemination can negatively impact litter size by reducing embryo survival when breeding at third estrus.

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.

REPRODUCTIVE PERFORMANCE OF BOOROOLA × FINNISH LANDRACE AND BOOROOLA × SUFFOLK EWE LAMBS, HETEROZYGOUS FOR THE F GENE, AND GROWTH TRAITS OF THEIR THREE-WAY CROSS LAMBS

1990 ◽  
Vol 70 (1) ◽  
pp. 55-65 ◽  
Author(s):  
F. CASTONGUAY ◽  
F. MINVIELLE ◽  
J. J. DUFOUR
Keyword(s):  
Litter Size ◽  
Reproductive Performance ◽  
Growth Traits ◽  
Average Daily Gain ◽  
Ovulation Rate ◽  
The Other ◽  
F Gene ◽  
Ewe Lambs ◽  
Genetic Groups ◽  
Significant Difference

Reproductive performance of Booroola × Finnish Landrace (BFL, n = 19) and Booroola × Suffolk (BS, n = 18) ewe lambs heterozygous for the F gene were compared to Finnish Landrace (FL, n = 14) and Suffolk (S, n = 26) purebred controls. FL lambs reached puberty earlier (211.3 d, P < 0.001) than the other genetic groups (237.8, 233.0 and 232.9 d for S, BS and BFL, respectively) whereas weight at puberty was lower (P < 0.001) for BFL, FL and BS (36.8, 36.7 and 47.0 kg, respectively) than for S (61.1 kg). About 95% of BFL and BS ewe lambs had at least one record of three ovulations or more over the first three estruses, including puberty. Mean ovulation rates at breeding (second estrus after puberty) to a Hampshire (H) ram were 3.8, 3.3, 2.2 and 1.7 for BFL, BS, FL and S, respectively (BFL and BS vs. FL and S, P < 0.001). The corresponding litter sizes at birth were 2.5, 2.1, 1.6 and 1.3 (BFL and BS vs. FL and S, P < 0.001) which reflected a higher embryonic loss in the Booroola crosses. Percentage ova loss ranged between 32.8% (BFL) and 12.8% (S) and was related to the level of prolificacy. Lamb mortality at birth was high in BFL (23.7%) compared to BS, FL and S (6.5, 0.0 and 0.0%, respectively, P < 0.001). Litter size at weaning (50 d of age) averaged 1.9, 1.8, 1.5 and 1.3 for BS, BFL, FL and S ewe lambs (BS vs. S, P < 0.02). Growth performance of H-sired progeny from the four genetic groups of ewes showed that H × S lambs had the highest average daily gain in both preweaning and postweaning periods (preweaning ADG: 349.9 g d−1; postweaning ADG: 332.1 g d−1) while the other genotypes of lambs performed equally (preweaning ADG: 267.4, 249.5 and 246.8 g d−1 for H × FL, H × BFL and H × BS, respectively; postweaning ADG: 281.2, 276.8 and 281.8 g d−1 for the same genetic groups). Overall productivity of ewe lambs in terms of kilograms of lamb produced showed a slight, nonsignificant, advantage for Booroola-cross ewe lambs (55.8 and 54.5 kg for BS and BFL) over purebred S (51.6 kg) and FL (44.9 kg). These results indicate that ovulation rate and litter size can be increased by incorporating F gene in both prolific (FL) and nonprolific (S) background genotypes without resulting in any significant difference in total weight of lamb produced per ewe. Key words: Sheep, ewe productivity, Booroola, ovulation rate, crossbreeding

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