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.

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.

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.

Divergent selection for ovulation rate in sheep : effect on embryo survival

1992 ◽  
Vol 1992 ◽  
pp. 44-44
Author(s):  
J.P. Hanrahan
Keyword(s):  
Genetic Variation ◽  
Litter Size ◽  
Mammalian Species ◽  
Divergent Selection ◽  
Ovulation Rate ◽  
Relative Importance ◽  
Embryo Survival ◽  
Breed Differences ◽  
Selection For ◽  
The Relationship

The relative importance of genetic variation in ovulation rate and in embryo survival together with the genetic relationship between these traits are important issues in terms of manipulating prolificacy in all multitocous mammalian species. Evidence in sheep, primarily from study of breed differences but also based on results of selection for litter size, shows that genetic variation in litter size is essentially attributable to differences in ovulation rate although genetic differences in embryo survival have been identified. Results from selection on litter size also suggest that genetic variation in ovulation rate is independent of any variation in embryo survival. The evaluation of the relationship between these traits in sheep is somewhat problematical in most populations due to the low level of ovulation and particularly the associated high proportion of ewes which shed a single ovum. The objective of the present study was to use lines of Finn Sheep, a breed with a high ovulation rate and in which single ovulations are rare, which have been developed by divergent selection on ovulation rate to evaluate the genetic association between ovulation rate and embryo survival.

A study of factors which influence the job satisfaction of stockpeople on commercial pig farms

1990 ◽  
Vol 1990 ◽  
pp. 95-95
Author(s):  
R C Segundo ◽  
P R English ◽  
G Burgess ◽  
S A Edwards ◽  
O MacPherson ◽  
...  
Keyword(s):  
Job Satisfaction ◽  
Reproductive Performance ◽  
Research Work ◽  
Farm Animals ◽  
Considerable Influence ◽  
Pig Farms ◽  
And Performance ◽  
The Uk ◽  
Farm Livestock

The role of stockmanship in relation to the wellbeing of farm animals has been emphasised in the UK Codes of Recommendations for the Welfare of Farm Livestock (MAFF, 1983). Moreover, previous research work has demonstrated important effects of good and bad stockmanship not only on welfare but also on growth, lactational and reproductive performance of pigs and other farm livestock (Hemsworth et al, 1987). There is a need, therefore, to establish the factors which motivate and demotivate stockpeople since the degree of job satisfaction is likely to have a considerable influence on the attitude and performance of stockpeople and on their empathy with the animals in their care. With this objective in mind, a questionnaire was designed to investigate the aspects which could have an influence on the job satisfaction of the stockpeople involved in pig production.

Effect of selection for increased litter size on ovulation rate and embryo survival in sheep

1990 ◽  
Vol 1990 ◽  
pp. 32-32 ◽  
Author(s):  
J.P. Hanrahan
Keyword(s):  
Litter Size ◽  
Ovulation Rate ◽  
Control Line ◽  
Selection Experiment ◽  
Embryo Survival ◽  
Relative Contribution ◽  
Variation Data ◽  
Component Traits ◽  
Selection For ◽  
The Impact

Variation in litter size in sheep is essentially attributable to variation in ovulation rate and embryo survival. Genetic variation in litter size, both among and within breeds, is largely attributable to variation in ovulation rate. While there is evidence for genetic differences among breeds in embryo survival the contribution of this component to within breed variation appears to be minor (Hanrahan, 1982). The impact of selection based on litter size on its component traits should reflect the relative contribution of these components to within breed variation. Data from two lines of Galway sheep, a Control line and one selected for increased prolificacy (Hanrahan and Timon, 1978), have been used to provide evidence on this point.Details relating to the selection experiment which provided the data for the present study are in Hanrahan (1984). Briefly a flock of Galway sheep was assembled from industry sources (both pedigree and non-pedigree) between 1963 and 1965.

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 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.

Reproductive performance and milk production of the improved Awassi breed as compared with its crosses with the Booroola Merino

1995 ◽  
Vol 60 (1) ◽  
pp. 109-115 ◽  
Author(s):  
E. Gootwine ◽  
A. Bor ◽  
R. Braw-Tal ◽  
A. Zenou
Keyword(s):  
Milk Production ◽  
Survival Rates ◽  
Ovulation Rate ◽  
Corpora Lutea ◽  
Embryo Survival ◽  
Average Birth Weight ◽  
Significant Difference ◽  
Per Se ◽  
Lamb Survival ◽  
Awassi Breed

AbstractOvulation rate, embryo survival, lamb production, lamb survival and milk production of Awassi and BooroolaAwassi crossbred ewes, kept indoors, were compared. Awassi were non-carriers while Booroola × Awassi (F1) and about half of 3/4 Awassi-1/4 Booroola (BQ) ewes were heterozygous at the FecB gene. Mean ovulation rate increased by 1·5 to 1·6 corpora lutea per ewe ovulating and prolificacy by 0·7 lambs born per ewe lambing in Fj and BC1 (B+) ewes as compared with Awassi. Embryo survival rates in BC1 ewes with two, three and four ovulations were 0·83, 0·68 and 0·71, respectively. Lamb survival rates at 1 day of age were 0·93, 0·90 and 0·77 and average birth weight was 4·9, 4·0 and 3·0 kg for lambs born as singles, twins and triplets, respectively. Average milk production of the Awassi was 506 I per ewe per lactation. F1 and BC1 ewes produced respectively, proportionately 0·48 and 0·63 of the Awassi milk production and there was no significant difference in milk production between BC1,(B+) and BC1(++) ewes. The relatively low milk production of the Booroola Awassi crosses suggests that heterosis and recombination effects on milk production were negative. It is concluded that incorporation of the B allele per se can increase lamb production in the Awassi without affecting its milk production.

Genetic implications of a simulation model of litter size in swine based on ovulation rate, potential embryonic viability and uterine capacity: II. Simulated selection.

1990 ◽  
Vol 68 (4) ◽  
pp. 980-986 ◽  
Author(s):  
G. L. Bennett ◽  
K. A. Leymaster
Keyword(s):  
Simulation Model ◽  
Litter Size ◽  
Selection Pressure ◽  
Selection Response ◽  
Ovulation Rate ◽  
Direct Selection ◽  
Weak Selection ◽  
Embryo Survival ◽  
Swine Population ◽  
Selection For

Abstract Direct selection for ovulation rate, uterine capacity, litter size and embryo survival and selection for indexes of ovulation rate with each of the remaining traits were simulated for a swine population. The relationships among these traits were determined from a simulation model that assumed that litter size was always less than or equal to both ovulation rate and uterine capacity. Heritabilities of ovulation rate and uterine capacity were assumed to be .25 and .20, respectively, and uncorrelated genetically and phenotypically. No additional genetic variation was assumed. Responses to weak selection pressure were simulated by recurrent updating of phenotypic variances and covariances combined with the heritabilities of ovulation rate and uterine capacity. Two indexes of ovulation rate and uterine capacity each resulted in 37% greater increase in litter size than direct selection for litter size. Indexes of ovulation rate and either litter size or embryo survival increased litter size by 21% more than direct selection for litter size. Selection for ovulation rate, uterine capacity or embryo survival was 6, 35 and 79%, respectively, less effective than direct selection for litter size. Responses to intense selection pressure were determined by direct simulation of genotypes and phenotypes of individuals. The two indexes of ovulation rate and uterine capacity exceeded direct selection for litter size by 39 and 27%. The indexes of ovulation rate and either litter size or embryo survival exceeded direct selection for litter size by 19 and 13%, respectively. Intense selection for ovulation rate or uterine capacity decreased selection response by 26 and 67%, respectively, relative to direct selection for litter size. Intense selection for embryo survival decreased litter size slightly.

The effect of protein restriction during the rearing period and age on reproductive function in the gilt

1998 ◽  
Vol 1998 ◽  
pp. 155-155
Author(s):  
VL Glasgow ◽  
SA Edwards ◽  
TG McEvoy ◽  
M Shanks
Keyword(s):  
Body Composition ◽  
Reproductive Performance ◽  
Present Experiment ◽  
Protein Quality ◽  
Reproductive Function ◽  
Early Embryo ◽  
Protein Restriction ◽  
Ovulation Rate ◽  
Embryo Survival ◽  
Early Embryo Development

Reproductive performance of gilts/sows can be influenced by metabolic state at crucial points in the reproductive cycle and indeed at a crucial age. It has generally been found that moderate to severe protein restriction has no effect on litter size or embryo survival at day 28 (Pharazyn et al, 1991) when given to gilts over the gestation period. However protein quality and quantity can affect reproductive performance in gilts when imposed over the prepubertal period as indicated previously by lower ovulation rate at an induced puberty and poorer expression of a second oestrus (Cia et al, 1996). In the present experiment the effects of two diets differing in lysine:energy ratio on body composition and subsequent oestrus response, ovulation rate and early embryo development in gilts of two different ages were studied.

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