Age At First Lambing Research Articles

Genetic parameters for growth and reproductive traits in Santa Inês sheep

Although Santa Inês sheep demonstrate good adaptation to tropical environments, there is a need for effective breeding programs focused on growth and reproductive traits to harness the breed's full developmental potential. Thus, this study aimed to estimate (co)variance components and genetic parameters for weight at birth (WB), weight at 60 days (W60), age at first lambing (AFL), first lambing interval (FLI), and average lambing interval (AFI) in Santa Inês sheep. The data were obtained from the Sergipe Goat and Sheep Breeders' Association (ASCCO). (Co)variance components and genetic parameters were estimated by Bayesian analysis based on a bitrait model with Gibbs sampling using Multiple-Trait Gibbs Sampler for Animal Models (MTGSAM) software. Heritability estimates (h2) for WB, W60, AFL, ALI, and FLI were 0.11, 0.18, 0.028, 0.25, and 0.30, respectively. Positive correlations were observed between WB and W60, AFL and ALI, and AFL and FLI (0.31, 0.17, and 0.18, respectively). By contrast, negative correlations were obtained for WB and AFL (−0.55), WB and AFL (−0.42), WB and FLI (−0.39), W60 and ALI (−0.26), and W60 and FLI (−0.37), with magnitudes ranging from low to moderate. Correlation values for ALI and FLI and W60 and AFL were positive and strong (0.97 and 0.98, respectively). These results indicate that the studied traits can be used for indirect selection. Furthermore, the findings underscore the importance of determining genetic parameters when formulating strategies for the genetic improvement of Santa Inês sheep.

Evaluation of the Crossbreeding Scheme and Farmers’ Perception of Awassi and Dorper Crossbred Sheep

The objectives of this study were to characterize the performance of crossbred sheep and crossbreeding scheme and to solicit farmers’ opinions about crossbred sheep. A total of 238 respondents were selected from five districts and data were collected through a personal interview, focus group discussion, measurement of animals, and field observation. Continuous type of data were analyzed using different procedures of SAS, while the estimated breeding value (EBV) for distributed rams was estimated by the WOMBAT software fitting animal model. The findings showed that sheep were the most significant species and that they were primarily raised for meat consumption and income generation. The proportions of crossbred sheep were 79.6% in Angot, 61.3% in Dessie zuria, 64.2% in Gazo, 80.6% in Legambo, and 27.5% in the Kobo area. The sheep crossbreeding program was constrained by feed shortage, lack of improved genotype, and diseases. The ongoing sheep crossbreeding program lacks a proper recording scheme, rams were not selected based on genetic merit, not exchanged in time, lack periodic importation of genetically unrelated rams, and lacks fixing the maximum exotic gene level suitable for the production system. The EBVs of Dorper crossbred rams for birth weight and weaning weight were 0.007 kg and 0.273 kg, respectively. Tikur sheep had an earlier age at first lambing (AFL) than Awassi x Tikur sheep. Likewise, the indigenous Wollo sheep had earlier AFL, short lambing interval, and produced a large number of lambs per lifetime than their Awassi crossbreds. Dorper crossbreds were preferred (9.30 - 72.2 times greater and P < 0.001 ) for their growth rate, physical appearance, preference in the market or price, and milk production of ewes compared with indigenous Tumele sheep. The Awassi crossbred sheep were preferred (odds ratio = 12.7– 90.0 and P < 0.001 ) due to their good physical appearance, fast growth rate, wool yield, milk yield, and better preference in the market compared with Tikur and Wollo sheep breeds. The implementation of the crossbreeding program needs some sort of revision, monitoring, and periodic evaluation. Besides, it must be accompanied by improved management to exploit the expected benefits from the crossbreeding program in the low-input production system.

Socio-economic and phenotypic parameters of Purgi goats of Ladakh, India

A study on the socio-economic, phenotypic, and technical features of Purgi goats in Kargil was undertaken. A total of 215 Purgi goat breeders from 8 villages were interviewed and 215 kids born between 2016 and 2018 were studied. The study revealed that Purgi goat farming under the study area is mainly practiced by poor farmers having an education level of middle to matric standard and belonging to the middle age group and scheduled tribe (Muslims) community. The average annual income (Lakhs) from goat farming, livestock rearing, agriculture, other sources and overall were 0.20±0.00, 0.32±0.02, 0.59±0.01, 0.59±0.01 and 1.40±0.02, respectively. Animals in small flocks are maintained semi-intensively. The predominant coat colour was black. The overall body weight (kg) was 1.08±0.04, 3.60±0.02, 5.83±0.03, 8.70±0.04, 10.58±0.06 and 13.46±0.14 at birth, weaning, 6, 9, 12 and 24 months. The least-squares means (cm) for body measurements, viz. height at withers (BH), body length (BL), heart girth (HG), and paunch girth (PG) at birth to yearling age were 58.87±0.03, 76.45±0.03, 71.21±0.05 and 74.22±0.12 cm, respectively. The age at first estrus, weight at first estrus, age at first service (AFS), weight at first service (WFS), age at first lambing (AFL), gestation period (GP), and inter kidding interval (KI) were 310.39±3.82 days, 74.22±0.12 (kg), 332.56±3.00 (days), 12.71±0.05 (kg), 513.06±2.36 (days), 149.93±0.11 (days) and 288.16±2.98 (days), respectively. It can be concluded that the Purgi goat is a unique, dwarf, and very important genetic resource of the country and it should be characterized and conserved for further improvements.

Effects of inbreeding on reproduction and fitness traits in a closed flock of Nilagiri sheep, an endangered Indian breed

The objective of this study was to investigate the effect of inbreeding on reproductive and fitness traits in Nilagiri sheep. Information on pedigree of 6430 animals collected during the year of 1965–2015 by Sheep Breeding Research Station (SBRS) in Sandynallah were used for analysis. Inbreeding coefficient (F) was calculated from pedigree information using Wright’s method. The average inbreeding per cent was 1.82% in the whole population studies (6430 animals). The average inbreeding per cent was 3.9% for 3007 no. of inbred animals. The effect of inbreeding on most of the reproduction and fitness traits were significant and depression due to inbreeding was evident.The significant effect of inbreeding on reproduction traits viz., age at first service (AFS), weight at first service (WFS), age at first lambing (AFL) and fitness traits viz., tupping percent (TP), number of lambs weaned per ewe mated (NLWEM), number of lambs weaned per ewe lambing (NLWEL) and total lambs weaned per ewe over lifetime (TLWE) was studied using a general linear model, with individual inbreeding coefficient as covariate. The partial regression coefficient for AFC, WFS, AFL, TP, NLWEM, NLWEL and TLWE were 1.28 days, −0.25 kg, 8.13 days, −0.02%, −0.028, −0.017 and −0.182 per 1 per cent increase in inbreeding for Nilagiri sheep. Survival and litter size were not affected by inbreeding. In general, inbreeding had a depressive effect on most of the reproduction and fitness traits. Inbreeding in the population has to be restricted through methods such as introduction of unrelated animals or following co-ancestry based mating system.

Non-genetic factors affecting litter size, age at first lambing and lambing interval of Romanov sheep in Croatia

Reproductive traits are of paramountimportance in an efficient lamb production system. In Croatia, values of reproductive traits of Romanov sheep are below the average expected for this breed, indicating the need for improvement of these traits to exploit the breed’s full reproductive potential. This study was conducted on 260 Romanov ewes located at a commercial Romanov sheep farm in Croatia. All ewes were kept under similar conditions, and reproductive management was based on accelerated lambing with continuous mating. Linear models with fixed effects were used to estimate the influence of year of birth/lambing, season of birth/lambing, ram, parity and litter type on litter size (LS), age at first lambing (AFL) and lambing interval (LI). Average LS was 2.11 ± 0.71, while the year of lambing and parity were the most important factors affecting this trait. The smallest litters were recorded after 1st parity (1.77 ± 0.06), and the largest after 5th parity (2.21 ± 0.08). AFL averaged 388.5 ± 72.4 days. All investigated non-genetic factors had a significant (P<0.05) influence on AFL, with year of birth as most important. The average LI was 241.2 ± 70.8 days. A significant (P<0.05) influence of all factors on LI was observed. Ewes lambing in spring (200.2 ± 7.9 days) or summer (190.5 ±6.6 days) had a significantly (P<0.05) shorter LI than ewes lambing in autumn (227.7 ± 8.3 days) or winter (237.2 ± 6.7 days). The longest LI was observed after the first parity (284.0 ±5.5 days). Average values for reproductive traits in the examined population of Romanov sheep were higher than those reported in the official Croatian database for breeding sheep. Non-genetic factors have a significant influence on the variation of reproductive traits of Romanov sheep, and therefore should be considered when assessing ewes’ reproductive performance.

Application of structural equation models for genetic evaluation of lifetime reproductive traits and age at first lambing in Moghani sheep

The present study aimed to investigate the advantages of structural equation modeling for genetic evaluation of lifetime reproduction traits and age at first lambing in Moghani sheep. Data collected between 1988 and 2011 were retrieved from the Jafarabad Breeding Station of Moghani sheep, located in the north-west of Iran. The investigated traits were age at first lambing (AFL) and lifetime reproductive traits, including overall litter size at birth (OLSB), overall litter size at weaning (OLSW), overall litter weight at birth (OLWB), and overall litter weight at weaning (OLWW). Two multivariate animal models, including standard (SMM) and Inductive Causation algorithm-based structural equation models (IC-SEM), were compared in terms of deviance information criterion (DIC) and predictive ability measures, including the mean square of error (MSE) and Pearson's correlation coefficient between the observed and predicted values (r(y,yˆ)) of records. In general, IC-SEM performed better than SMM in terms of DIC, MSE, and r(y,yˆ) in such a way that the lowest DIC and MSE, and the highest r(y,yˆ) were obtained under IC-SEM. All the structural coefficients estimated by IC-SEM were statistically significant. Heritability estimates for the traits studied were low values of 0.11, 0.03, 0.07, 0.03, and 0.09 for AFL, OLSB, OLSW, OLWB, and OLWW, respectively, implying that the studied traits were mainly controlled by non-additive genetic and environmental effects. AFL had negative and statistically significant (95% highest posterior density (HPD) intervals did not include zero) genetic correlations with other traits studied, ranging from − 0.45 for AFL-OLSB to − 0.69 for AFL-OLWW; meaning that a fast-growing ewe lamb can achieve higher reproductive performance. Genetic correlations among lifetime reproductive traits were positive and statistically significant (99% HPD did not include zero), and varied from 0.36 (OLSB-OLWW) to 0.81 (OLSB-OLSW). According to the causal structure detected by the inductive causation (IC) algorithm, it can be concluded that OLSB, as a parent trait, had indirect causal effects on OLWW, as a composite reproductive trait, mediated via both OLSW and OLWB. AFL had no phenotypic causal impact on the lifetime reproductive traits of Moghani ewes but was negatively associated with these traits in terms of additive genetic effects.

Analysis of genetic parameters and genetic trends for early growth and reproductive traits of Doyogena sheep managed under community-based breeding program

This study aims to estimate genetic parameters and genetic trends for early growth and reproductive traits of Doyogena sheep. Data used in the study were collected over 6 years (2013–2018). Studied traits were birth weight (BWT), weaning weight (WWT), 6-month weight (SMWT), average daily gains from birth to weaning (ADG0-3), average daily gains from weaning to 6-month age (ADG3-6), average daily gain from birth to 6-month age (ADG0-6), litter size (LS), lambing interval (LI), age at first lambing (AFL), and annual reproductive rate (ARR). (Co) variance components and genetic parameters were estimated using restricted maximum likelihood (REML). The analyses were carried out using WOMBAT program. Univariate analysis was applied to estimate genetic parameters. Six different animal models were fitted by including or excluding maternal effects. The direct heritability estimates for BWT, WWT, SMWT, ADG0-3, ADG3-6 and ADG0-6 were 0.33 ± 0.06, 0.31 ± 0.06, 0.14 ± 0.06, 0.13 ± 0.04, 0.11 ± 0.07, and 0.02 ± 0.05 respectively. Direct heritability for LS, LI, and AFL were 0.28 ± 0.12, 0.20 ± 0.5, and 0.001 ± 0.3, respectively. The maternal heritability estimates for BWT, WWT, and LS were 0.24 ± 0.12, 0.60 ± 0.07, and 0.24 ± 0.08, respectively. The genetic correlation between BWT with WWT and BWT with SMWT were 0.21 ± 0.07 and 0.21 ± 0.09, respectively. Genetic progress for most of the studied traits has shown promising improvements. Thus, continuation of selection, therefore, suggested for more improvements in the performance of Doyogena sheep. Direct heritability estimates decrease as lamb age increases and selection based on earlier body weight will be more efficient.

Genetic and non-genetic effects associated with ewe productivity in Harnali sheep.

The objective of the current study was to estimate the genetic parameters for ewe productivity traits of Harnali sheep by examining non-genetic effects. The data records of 440 animals born to 85 sires and 259 dams were collected with respect to various traits such as litter size at birth (LSB), litter weight at birth (LWB), litter size at weaning (LSW), litter weight at weaning (LWW) and age at first lambing (AFL) for the period of 2001 to 2020. Genetic parameters were estimated by fitting a series of animal models using an average information restricted maximum likelihood (REML) algorithm in WOMBAT software. Least-squares analysis revealed significant (P < 0.05) influences of period of lambing, age and weight of ewe at lambing on the studied traits. These results indicated that heavier ewes had significantly higher (P < 0.05) values of litter weight traits than their counterparts. On the basis of likelihood ratio test, the estimates of direct heritability under best model for AFL, LSB, LWB, LSW and LWW were 0.06, 0.18, 0.09, 0.07 and 0.16, respectively. Maternal permanent environment effect made a significant contribution to the LSB trait (0.20). The genetic correlation between litter size and LWW was negative, while the remaining correlations were positive. The present results suggest that selection based on ewe productivity traits will result in low genetic progress and therefore the management role is more important for better gains.

The Impact of Age at First Lambing on Milk Yield and Lactation Length in a Population of Istrian Sheep under Semi-Intensive Management.

Simple SummaryThe impact of age at first lambing on dairy traits has been poorly investigated in sheep, especially in semi-intensive husbandry systems. Insufficient information on this issue, especially scientifically proven, leads to many speculations among breeders. The aim of this study was to examine the impact of age at first lambing on days in milk, daily milk yield, and total milk yield. The study was conducted on field data routinely collected in a population of Istrian sheep bred under selection. It was determined that the prolongation of the first mating of lamb ewes to the second year of life is not beneficial to milk production. In conclusion, ewes reared under semi-intensive dairy orientated systems could be successfully bred in their first year of life in order to reduce their unproductive non-milking phase. This study aimed to examine the impact of ewe’s age at first lambing (AFL) on days in milk (DIM), average daily milk yield (DMY), and total milk yield (TMY). Symmetrical bimodal distribution of AFL enabled classification of maidens in those mated in the first (47%) or second year of life (53%). After accounting for all available sources of phenotypic variability with the linear mixed model for repeated records, it was estimated that AFL had a statistically significant effect only on DIM (p < 0.001). The litter size had a significant effect only on TMY (p < 0.001), while the effect of the parity was significant for all the examined traits (p < 0.001). The results of the study suggest that prolongation of age at first mating to the second year of life is not justified in dairy-orientated sheep farms. However, more evidence on this issue is needed for generalization, especially considering some other traits that can impact profitability of dual-purpose sheep farms (reproduction traits, growth rate of lambs, etc.).

Effect of Inbreeding Coefficient on Growth and Fitness Traits in a Closed Flock of Corriedale Sheep

Background: The corriedale sheep breed was imported into J and K during sixties for use in improvement of local sheep and are maintained at Mountain Research Station of Sheep and Goat, SKUAST- K. The animals over the years were allowed to mate within the selected animals of the flock as there was hardy any fresh importation of exotic animals from last 49 years due to which closed flock population was established within the farm. This has led to apprehensions over the loss of genetic diversity through years.Methods: The present study was to undertaken to evaluate the performance of Corriedale sheep under temperate climate and to estimate the inbreeding coefficient and its effect on growth and fitness traits of Corriedale sheep maintained at Mountain Research Centre for Sheep and Goat (MRCSG), F.V.Sc and A.H, SKUAST-K Shuhama, Kashmir. The information on performance and pedigree spanning over a period of 49 years (1969-2017) was collected and utilized for the study. The traits studied were birth weight (BW), weaning weight (WW), 6 months weight (6MW), 9 months weight (9MW) and 12 months weight (12MW) age at first lambing (AFL), litter size (LS), total lambs born per ewe (TLB) and survival rate (SR). Result: The averages estimates for BW, WW, 6MW, 9MW, 12MW, AFL, LS, TLB and SR were 3.72±0.01 kg, 13.31±0.07 kg, 18.65±0.05kg, 22.15±0.04 kg, 25.84±0.06 kg 807.20±4.34 days, 1.08±0.00, 4.83±0.03 and 80.76±1.98, respectively. The overall inbreeding coefficient (F) and proportion of population inbred (per cent) for Corriedale sheep were 18.3 and 43.3, respectively. The increased inbreeding coefficient had negative impact and highly significant (p less than 0.01) on all the traits under study except LS. The increased inbreeding coefficient (F) also had a negative impact on all the traits under study. With increase in the level of inbreeding there was a decrease in total body weight traits, lambs born per ewe and survival rate where as age at first lambing was increasing with the increase. he results indicated as decrease of 0.25 kg, 1.45 kg, 5.04 kg, 5.53 kg and 5.48 kg in body weight of the animals at birth, weaning weight, six months, nine months and twelve months from 1969-2017. To overcome the negative impact of inbreeding coefficient in the flock introduction of genetic variability through importation of Corriedale germplasm into the farm is highly recommended.

Estimates of genetic parameters and trends for reproduction traits in Bonga sheep, Ethiopia.

Investigation was carried out to assess the effects of environmental factors and to estimate genetic parameters and trends for reproductive traits in Bonga sheep, Ethiopia. Animals used in this study were managed by two communities involved in a community-based breeding programs (CBBPs) from 2009 to 2018. The database consisted of 15,595 individual phenotypic information from about 1500 ewes with variable number of records for each trait. The traits analyzed were age at first lambing (AFL), lambing interval (LI), and litter size (LS). Fixed effect analysis was done using the general linear model procedures of SAS. The Average Information Restricted Maximum Likelihood method of WOMBAT, fitting univariate animalmodel, was used to estimate heritabilities, repeatabilities and breeding values. Results showed that Bonga sheep had overall mean AFL, LI, and LS of 453 ± 109days, 254 ± 51days, and 1.43 ± 0.008, respectively. All traits were influenced (p < 0.01) by lambing year, lambing season, breeder communities, and parity of ewes. Estimates of heritability for AFL, LI, and LS were 0.015 ± 0.143, 0.009 ± 0.070, and 0.085 ± 0.110, respectively. The low heritabilities for the traits are expected and indicate low possibility of achieving rapid genetic progress through phenotypic selection. The repeatability estimates for LI and LS were low (0.109 and 0.196, respectively) indicating that non-genetic factors had significant influence to the variation in these traits among parities; therefore, selection decision on ewes should consider repeated records. The genetic trend for AFL, LI, and LS over the years was significant (p < 0.01). Positive values for LS and negative for AFL and LI were recorded, implying that the well-structured CBBPs have resulted in measurable genetic gains for the reproductive traits.

Estimation of co-variance components, genetic parameters, and genetic trends of reproductive traits in community-based breeding program of Bonga sheep in Ethiopia.

ObjectiveThe objectives of the study were to evaluate reproductive performance and selection response through genetic trend of community-based breeding programs (CBBPs) of Bonga sheep.MethodsReproduction traits data were collected between 2012 and 2018 from Bonga sheep CBBPs. Phenotypic performance was analyzed using the general linear model procedures of Statistical Analysis System. Genetic parameters were estimated by univariate animal model for age at first lambing (AFL) and repeatability models for lambing interval (LI), litter size (LS), and annual reproductive rate (ARR) traits using restricted maximum likelihood method of WOMBAT. For correlations bivariate animal model was used. Best model was chosen based on likelihood ratio test. The genetic trends were estimated by the weighted regression of the average breeding value of the animals on the year of birth/lambing.ResultsThe overall least squares mean±standard error of AFL, LI, LS, and ARR were 375± 12.5, 284±9.9, 1.45±0.010, and 2.31±0.050, respectively. Direct heritability estimates for AFL, LI, LS, and ARR were 0.07±0.190, 0.06±0.120, 0.18±0.070, and 0.25±0.203, respectively. The low heritability for both AFL and LI showed that these traits respond little to selection programs but rather highly depend on animal management options. The annual genetic gains were −0.0281 days, −0.016 days, −0.0002 lambs and 0.0003 lambs for AFL, LI, LS, and ARR, respectively.ConclusionImplications of the result to future improvement programs were improving management of animals, conservation of prolific flocks and out scaling the CBBP to get better results.

Effects of non-genetic factors on growth traits and age at first lambing in Corriedale sheep

Data pertaining to Corriedale sheep (4,367 birth records) spanning over a period of 25 years from 1989 to 2013 was analyzed with the Mixed Model Least Square and Maximum Likelihood algorithms to assess fixed effects of year, sex, type of birth and age of dam on various growth traits and age at first lambing. The averages were 3.69, 12.16, 17.65, 22.45, 34.59 and 893.41 for birth weight (BW), weaning weight (WW), 6 month body weight (W6), 12 month body weight (W12), 18 month body weight (W18) and age at first lambing (AFL) respectively. The overall least square means (kg) for BW, WW, W6, W12, W18 and AFL (day) were 3.20±0.091, 11.05±0.408, 16.06±0.452, 21.69±0.722, 33.425±0.776 and 882.50±11.33 respectively. Year of birth had a highly significant influence on all the studied traits. The effect of type of the birth was significant on BW, WW, W6 but non-significant on W12, W18 and AFL. Sex of the lamb had a significant effect on BW, WW, W6 and W12 and non-significant effect on W18. Dam age had a significant effect on all the body weight traits except W18. It also had a significant effect on AFL. The overview of the study reveals that the non-genetic factors affected growth traits and age at first lambing therefore should be taken into consideration while evaluating the performance of the animals. The germplasm of the Corriedale breed which is a mutton breed of sheep can be improved by selection of good animals and improving the management conditions.

Estimation of genetic, phenotypic and environmental trends for production and reproduction traits in a flock of Corriedale sheep

The aim of the present study was to estimate genetic, phenotypic and environmental trends for birth weight (BW), weaning weight (WW), six months body weight (W6), yearling body weight (W12) and age at first lambing (AFL). The genetic trends (gm), respectively, for BW, WW, W6 and W12 were 8, 44.22, 8.05 and 29.45 whereas for AFL it was –0.03 (day/year). The phenotypic trends (gm), respectively for BW, WW, W6 and W12 were –1.3, 36.06, –30.77 and 32.90 whereas for AFL it was 4.39 (day/year). The environmental trends (gm / year) respectively for BW, WW, W6, W12 were –9.3, –8.2, –38.83 and 3.45 whereas for AFL it was –4.36 (day/year). Positive and statistically significant genetic trends were recorded for all studied body weight traits whereas for AFL it was nonsignificant. Phenotypic trends for all the traits under study were statistically non-significant.

Estimation of genetic parameters for production and reproduction traits in Kashmir Merino sheep

Data pertaining to 6,300 birth records spread over 21 years of Kashmir Merino sheep maintained at Government Sheep Breeding Farm Kralapathri and Government Sheep Breeding Farm Goabal Kashmir and Fleece Testing Laboratory were used to estimate the genetic parameters. The genetic parameters for birth weight (BWT), 6 months body weight (6-MWT), yearling body weight (12 MWT), greasy fleece yield of first clip (GFY-1), greasy fleece yield of second clip (GFY-2), fiber diameter (FD), staple length (SL), age at first lambing (AFL) and inter-lambing period (ILP) were estimated by paternal half-sib correlation method using sire components of variance and covariance. The heritability estimates for BWT, 6-MWT, 12-MWT, SL, GFY-1, GFY-2 were moderately high whereas the estimates of heritability for FD, SL, AFL and ILP were low respectively. The genetic correlation between different traits ranged from - 0.73±0.10 to 0.87±0.04 while as phenotypic correlation different traits ranged from - 0.66±0.07 to 0.54±0.01. Keeping in view its high heritability of SMW and favorable correlations with birth weight, yearling body weight, wool traits and age at first lambing, it is concluded that selection on basis of 6-MWT would be effective to improve growth, quality wool production and age at first lambing in Kashmir Merino sheep.

Genetic parameter estimates for reproductive traits in Chokla ewes of India.

Early selection of ewes for better reproductive performance may reduce generation interval and increase genetic gains. Considering this, the present study aimed to derive the genetic parameter estimates of ten reproductive traits in 1172 maiden Chokla ewes over a period of 22years. Initially, the traits, namely age at first service (AFS), weight at first service (WFS), age at first successful service (ASS), weight at first successful service (WSS), age at first lambing (AFL), ewe's weight at first lambing (WFL), first lambing interval (LI1), first service period (SP1), first parity lamb survival (SUR1) and first service fertility rate (FER1) were analysed for the effects of genetic and non-genetic factors. The significant effects were fitted into six animal models to estimate the genetic parameters. The heritability estimates were low for the age traits and FER1 (0.06-0.09) but moderate for the rest of the traits (0.16-0.23), indicating the suitability of these traits for improvement through direct selection. The maternal direct and permanent effects were meagre for all the traits. The ewe weights had strongly negative correlations with the age of sexual maturity and positive correlations with lamb survival. The results emphasise the need to optimize the weights of maiden ewes to improve reproductive performance.

Evaluation of some reproductive traits of Pelibuey ewes under humid tropical conditions of Mexico

ABSTRACT We evaluated the effect of some environmental factors on age at first lambing (AFL) and lambing to conception interval (LCI) of Pelibuey ewes under the humid tropical conditions of Mexico. Ewes grazed on Tanzania (Panicum maximum), Bermuda (Cynodon dactylon), and Brachiaria grass (Brachiaria humidicola) and received hay in the corral in the months of grass scarcity. Reproduction was continuous during the year. Data of 839 lambings from 334 ewes registered from 2009 to 2017 were analyzed using survival analysis [...]

Short communication: Genetic parameters for post-weaning visual scores and reproductive traits in Suffolk sheep

The aim of this study was to estimate the coefficients of heritability and genetic correlations among visual scores (conformation, CPW; precocity, PPW; musculature, MPW) and reproductive traits: age at first lambing (AFL) and scrotal circumference (SC) evaluated at 180 days of age in Suffolk lambs. In the statistical model only the additive genetic effect was considered as random effect. The heritability estimates by univariate analyses for CPW, PPW, MPW, AFL and SC were 0.08, 0.12, 0.09, 0.20 and 0.22, respectively. The genetic correlations among AFL and CPW, PPW, MPW were -0.26, 0.19, and 0.08, respectively. The genetic correlation among SC and CPW, PPW, MPW were, respectively, 0.54, 0.88 and 0.86, and between AFL and SC was 0.26. The direct selection for conformation, precocity and musculature at 180 days of age and age at first lambing will provide slow genetic progress due to low heritability estimates. It is possible to obtain genetic gain in sexual precocity through selection on scrotal circumference in Suffolk rams. The favorable genetic correlation among visual scores and SC and between CPW and AFL, indicated the possibility to gain in genetic progress for reproductive traits through indirect selection of the visual scores in Suffolk sheep.

Estimation of Genetic Parameters for Reproduction Traits in Munjal Sheep

Estimates of genetic parameters are important to determine the selection criterion and future breeding strategies. Munjal is one of the heaviest breed of sheep and is popular among farmers for faster growth rate and efficient reproduction. The data of reproduction traits of 287 Munjal sheep maintained at Lala Lajpat Rai University of Veterinary and Animal Sciences, Hisar for 16 years (2001-2016) were utilized to estimate the genetic parameters. The mixed linear model used for analysis included the sire as a random effect and period of birth and dam’s age at lambing as fixed effects. Heritability and genetic correlations for different traits were estimated by paternal half-sib correlation method using sire components of variance and covariance. All the reproduction traits under study viz., Age at first service (AFS), weight at first service (WFS), age at first lambing (AFL), weight at first lambing (WFL) and first lambing interval (FLI) were significantly affected by period of birth. However, effect of dam’s age at lambing was non-significant on all traits. The overall least squares mean for AFS, WFS, AFL, WFL and FLI were estimated as 563.08±14.43days, 29.06±0.16 kg, 713.48±14.02 days, 31.30±0.16 kg and 351.82±1.12 days, respectively. Heritability estimates for AFS, WFS, AFL, WFL and FLI were obtained 0.19±0.12, 0.24±0.15, 0.17±0.10, 0.27±0.15 and 0.05±0.01, respectively. The genetic correlation of AFS with AFL (0.96±0.01) and WFS with WFL (0.94±0.03) was high and positive indicating that ewes in good body condition at service maintaining it after lambing. Low estimates of heritability for reproduction traits indicated that these traits have low additive genetic variance and mostly influenced by environment. So, these traits can be improved by better managemental practices.

Farmers' Trait Preferences for Breeding of Small Ruminants in Ada Barga and Ejere Districts of West Shoa Zone, Oromia, Ethiopia

The productive and reproductive performances of small ruminants and producers’ traits preferences were studied in three agro- ecologies (AEZs) of Ada Barga and Ejere districts, West Shoa Zone, Oromia, Ethiopia. The two districts were stratified into highland (HL), midland (ML) and lowland (LL) agro ecologies. A total of 180 households of which 69 from HL, 74 from ML and 37 from LL were purposively selected for this study. Detailed structured questionnaires, respondent interviews and farmers’ group discussions (FGD) were employed to capture relevant information. The overall age at first lambing (AFL) / age at first kidding (AFK), weaning age, age at sexual maturity of male (ASMM), reproductive life span of both sheep and goat were significantly affected by AEZs. The overall mean of slaughter age and ASMM was 6.43, 8.91 in sheep and 6.27, 8.39 in goat, respectively. High intensive kidding and lambing months was April to June.