Yearling Body Weight Research Articles

Polymorphism of Melanocortin-4 Receptor Gene and Its Association with Growth Traits in Bali Cattle

The melanocortin-4 receptor (MC4R) is a gene that controls growth traits. This gene is embedded in the leptin-melanocortin pathway and regulates body weight. Previous studies have successfully identified the genetic diversity of the MC4R associated with growth traits. However, studies on Bali cattle are limited. This study aimed to identify the SNP markers of the MC4R gene and its effect on birth body weight, weaning body weight, weaning chest girth, weaning withers height, weaning body length, yearling body weight, yearling chest girth, yearling withers height, and yearling body length in Bali cattle (n=43). The MC4R genotype was identified by sequencing and aligned using BioEdit v.7.2.5. The association between genotype and growth traits was analyzed using the GLM procedure and DMRT in RStudio program v.2022.02. Four SNPs were identified in the exon region:  g.355GT, g.394CT, g.463GA, and g.682GA.  Based on the Chi-square test, the population was fitted with HWE (p0.05). Genotype-phenotype association based on SNPs showed no significant result (p0.05) where the g.682GA (AG) locus had values of WB (104.33+17.15 kg), WCG (112.83+3.66 kg), WBL (89.50+3.94 kg), YB (124.17+22.44 kg), YCG (120.50+5.50 kg), and YBL (92.83+4.31 kg) higher than the other genotypes. Association based on haplotype type showed significant results (p0.05) in BB, where haplotype 2 had the highest BB (21.17+0.75 kg). In conclusion, the SNP markers found in this study were polymorphic but did not affect growth traits in Bali cattle.

Efficiency of Growth in an Organized Herd of Gir cattle in North Saurashtra Agro-climatic Region of Gujarat

The present study was undertaken to find the efficiency of growth performance in Gir calves born (N=52) and raised at Bull Mother Farm, Kamdhenu University, Amreli. The overall birth weight in Gir calves was 24.66 ± 0.40 kg, male calves being significantly (P, 0.004) heavier (9.88%) at birth than female calves. Irrespective of sex, the Gir calves weighed 66.83 kg at 3 months and 109.25 kg at 6 months of age, whereas yearling body weight was 192.82 kg. At 2 years of age, the Gir heifers attained 263.57 ± 17.29 kg body weight, which was above the optimum/ desired breedable body (240-250 kg). The body weight gains from birth to 3 month and from 3 to 6 month growth phases were almost similar, values being 466.9 ± 12.81 and 468.94 ± 20.15 gm/day, respectively. After attaining 1 year of age, the rate of body weight gain showed a diminishing trend, from 312.37 to 270.61 gm/day, with advancement of age. Relative body weight gain, irrespective of sex, was a maximum of 172.88 ± 6.51 % in the birth to 3 month age group, followed by 63.66 ± 2.66% in the 3 to 6 month age group. The findings indicated that due care of the Gir calves, especially during birth to 3 month age is vital to explore their growth potential, as relative weight gain of calves during this phase is maximum (172.88%) for attaining early breedable body weight and in turn, reducing age at first calving.

Effect of breed and some non-genetic factors on growth performance of sheep under temperate conditions of Kashmir

The data pertaining to 4849 birth records spanning over a period of 21 years (1997–2017) of different genetic groups were collected from Mountain Research Centre for sheep and goat Station (MRCSG), Shere Kashmir University of Agricultural Science and Technology, Kashmir (SKUAST-K), Shuhama, Kashmir to investigate the effects of genetic group and non-genetic factors on growth performance of Bakarwal, Corriedale, Hampshire x Corrriedale Cross, Hampshire, Non-descript x Corriedale Cross, Non-descript x Polled Dorset Cross, Polled Dorset x Corriedale, Polled Dorset and South down sheep genetic groups. The non-genetic factors considered were period of birth sex of lamb whereas the growth profile traits considered were birth weight (BW), weaning weight (W3), six months body weight (W6), yearling body weight (W12), average daily gain from birth to weaning (ADG1), metabolic mass at weaning (W30.75), Kleiber ratio from birth to weaning (KR1), average daily gain from weaning to yearling age (ADG2), metabolic mass at yearling age (W120.75) and Kleiber ratio from weaning to yearling age (KR2). The overall least-squares means for BW, W3, W6, W12, ADG1, W30.75, KR1, ADG2, W120.75 and KR2 were 3.47 ± 0.04 kg, 13.30 ± 0.15 kg, 18.13 ± 0.19 kg, 23.79 ± 0.25 kg, 107.58 ± 1.54 g/day, 6.93 ± 0.06 kg, 15.20 ± 0.12, 37.21 ± 0.86, 10.81 ± 0.09 and 3.37 ± 0.06, respectively. The effect of genetic group and period was highly significant (p < 0.01) on all the traits under study whereas effect of sex was significant (p < 0.05) on BW, W3, W6, W12, ADG-1, ADG-2, W30.75 and W120.75 with sexual dimorphism of 1.03, 1.08, 1.09, 1.06, 1.03, 1.05, 1.07, 1.09, 1.05 and 1.04 for BW, W3, ADG1, W30.75, KR1, W6, W12, ADG2, W120.75 and KR2, respectively. The effect of interaction of genetic group and period of birth was highly significant (p > 0.01) whereas the effect of interaction of sex and period of birth was significant (p > 0.05) on all the traits under study. The effect of interaction of genetic group and sex was significant on BW, W3, ADG1 and W30.75 only. Pre-weaning average daily gains (ADG1) and Kleiber ratio (KR1) were higher than post-weaning average daily gains (ADG2) and Kleiber ratio (KR2), respectively in all genetic groups. Whereas the metabolic mass at weaning (W30.75) was lower than metabolic mass at yearling age (W120.75) in all genetic groups. The non-genetic factors of sex and period were observed to be important sources variation in the growth performance of sheep. The study concludes that Hampshire x Corrriedale cross outperformed other genetic groups with respect to ADG2 and W12. Further, environment plays significant role in performance of genotype. Hence, Hampshire x Corrriedale cross should intersemated to produce and evaluate F2 generation for post-weaning growth rate.

Estimates of (co)variance components and phenotypic and genetic parameters of growth traits and wool traits in Alpine Merino sheep.

The (co)variance components and corresponding phenotypic and genetic parameters for growth traits and wool traits of economic importance were estimated in the Alpine Merino sheep population maintained at Gansu Provincial Sheep Breeding Technology Extension Station in northwestern China. Data from a maximum of 49,474 animals sired by 526 rams and born from 22,531 ewes over 20years from 2000 to 2019 were used in this study. Birth type, age of dam, birth year, sex and/or management group, and age at measurement were initially fitted as fixed effects in an animal model with various random effects. Genetic groups were defined for all animals by the sire breed and breed genotype interacted with dam-strain flocks and were fitted as one of the random effects. Analyses were conducted using a residual maximum likelihood procedure (ASReml). Seven different animal models were fitted for all traits, and the most appropriate model with relevant random effects was selected through log-likelihood ratio testing. After identifying the appropriate model through single-trait analysis, bivariate analyses were used to obtain the phenotypic and genetic correlations among the traits. The estimates of additive direct heritability for birth weight (BWT), weaning weight (WWT), preweaning growth rate (prwADG), postweaning growth rate (powADG), yearling body weight (YWT), average fibre diameter (AFD), greasy fleece weight (GFW), clean fleece weight (CFW), yield (YLD), yearling wool staple length (YSL), coefficient of variation of average fibre diameter (FDcv) and wool visual fineness counts (VFC) were 0.30, 0.18, 0.18, 0.20, 0.29, 0.20, 0.19, 0.20, 0.35, 0.19, 0.16 and 0.13, respectively, with standard errors ranging from 0.02 to 0.05. The corresponding ratios of genetic group variance to additive genetic variance were significant and, respectively, 0.35, 0.80, 0.62, 0.26, 0.13, 1.06, 0.38, 0.64, 0.09, 0.12, 0.06 and 0.58. These results suggest for these traits that there is potential to exploit both the additive genetic variation and between genetic group variation although for most traits the between group variation was smaller than the variation within groups. Favourable genetic correlations were found among the growth traits, and between growth traits and fleece production traits, and among wool traits GFW, CFW, YSL and YLD. This study provides the required estimates of genetic parameters of both growth and wool traits of the new breed for the design of more effective breeding programmes.

Growth Performance of Purgi Goats under Field Conditions in Kargil District (Ladakh)

Background: Purgi goats are native to Ladakh. They are used for fibre production and are known for the quality chevon. A study was, therefore, undertaken to study the effect of non-genetic factors on growth traits of Purgi Goats in its breeding tract. Methods: Flocks of 80 farmers from 8 villages of district Kargil were monitored to collect the data pertaining to growth traits during 2017 and 2018. The data so collected were suitably classified to study the major fixed effects like birth year, kid, parity of dam, season of birth and type of birth. Result: The averages were1.21±0.02, 3.62±0.02, 5.82±0.02, 8.73±0.03, 10.71±0.04 and 13.49±0.09 for BW, WW, 6MW, 9MW, 12MW and 18MW, respectively. The coefficients of variations of all the traits were low. Highest variability of 13.49 was observed for 18MW. The values of least squares means (LSM’s) of 0.96±0.05, 3.74±0.03, 5.80±0.05, 8.74±0.06, 10.87±0.08 and 13.91±0.19 for birthweight (BW), weaning weight (WW), six months body weight (6MW), nine months weight (9MW), yearling body weight (12MW) and eighteen months (18MW) weight were observed in the present study. The effects of sex of kids, season of birth and year of birth were significant (p less than 0.05) on all traits under study, whereas effect of birth-type was significant (p less than 0.05) on BW and WW and effect of parity was non-significant on all traits under study. All the traits BW, WW and 6MW were positively correlated among themselves. The correlations ranged from low (between BW and WW ) to high (WW with 9MW and 12MW).

INFLUENCE OF QUALITATIVE TRAITS ON THE PERFORMANCE OF WEST AFRICAN DWARF GOATS

Data on coat colour pigmentation and incidence of wattle were combined with production records of 1407 West African dwarf goats to study their influence on litter traits and body weight. There was no significant (P&gt;0.05) difference among coat colours for litter size at birth and at weaning and birth weight. Basic white coloured goats were significantly (P &lt;0.05) heavier at weaning and one year of age than the basic brown and black goats. The trend was that the weight decreased with increased pigmentation. Presence or absence of wattle did not exert any influence on the traits studied except yearling body weight Bilaterally wattled goats were lighter (P&lt;0.01) than unilaterally wattled and non wattled goats.

ESTIMATES OF PHENOTYPIC AND GENETIC CORRELATIONS IN WEST AFRICAN DWARF GOATS

Records on 848 West African dwarf goat kids and 220 kiddings over a period of eight year's (1982-1989) were analyzed. The records were used to provide estimates of phenotypic and venetic correlations among parity, kidding interval, litter size at birth and body weight at various ages. Plenotypic correlation coefficients of +0.33 (P&lt;0.01) and -0,17 (P&lt;0.01) were obtained when parity was correlated with litter size at birth and kidding interval respectively. Phenotypic correlations among body weights were generally positive and significant (P&lt;0.01). Parity was positively correlated (P&lt;0.01) with body weight at the various ages except at 1 year (P&gt;0.05). Litter size was, however, negatively correlated (P&lt;0.01) with body weight at the various ages except at 1 year (P&lt;0.05). The genetic correlations among body weights at variuus ages were positive and significant (P&lt;0.01). Selection for body weight at in earlier age especially at 3 months is likely to result in improvement of yearling body weight.

Hierarchical cluster analysis of yearling body weight and linear body measurementsof sheep of Northern Nigeria and their crosses

This study was conducted at the Sheep Project Unit of Small Ruminant Research Programme (SRRP) of National Animal Production Research Institute (NAPRI), Ahmadu Bello University, Shika, Zaria. Balami, Uda and Yankasa breeds (sheep of Northern Nigeria) were crossed . A total of 65 Yankasa, 23 Uda and 16 Balami ewes were served by 4 Yankasa, 3 Uda and 3 Balami rams. The diallel breeding pattern produced 192 lambs. However, only the 65 yearling that survived up to 12 months of age (yearling) were used for this study. The yearling body weight and linear body measurement data were analysed using General Linear Model (GLM) procedures of SAS with model that incorporated lamb genotype as fixed effects. Pairwise difference was used to separate the mean (SAS, 2003). Distances were used to construct dendrogram using the Unweighted Pairs Group Method Analysis implemented in R 2.13.0 package. TREE procedure that prints the dendrogram based on the distances between the clusters was introduced in PROC CLUSTER procedure. Yearling genotype affected body weight and all the linear body measurements considered in this study (P&lt;0.05). The pure Balami yearling (BL X BL) had the highest birth weight at 12 months of age (29.10±4.02kg). Clumping structure of yearling body weight among sheep of Northern Nigeria and their crosses were grouped into two clusters at distance 2.656. Pure Balami (BL X BL) formed the first cluster while the rest of the genotypes belong to the second cluster. The second cluster was further divided into two sub-groups at 0.796. The first sub-group had yearlings from pure Uda (UD X UD), Uda ram and Yankasa ewe (UD X YK), Uda ram and Balami ewe (UD X BL), Balami ram and Uda ewe (BL X UD) and Yankasa ram and Uda ewe (YK X UD) at 0.514. Similar clumping structures with two clusters share among the nine genotypes at varied distances were recorded for all the linear body measurements studied. Patterns of similarities were established for yearling body weight and linear body measurements among sheep of Northern Nigeria and their crosses. Improvement plans for yearling growth traits of sheep in Nigeria should consider the genotypes with divergent genetic distances as sires and dams. This will ensure the best exploration of positive heterosis.&#x0D;

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.

Genetic evaluation of growth performance in Corriedale sheep in J&amp;K, India

The data pertaining to 6874 lambs born to a total of 145 sires spanning over a period of 49 years (1969–2017) were collected from Mountain Sheep and Goat Research Station, SKUAST-K, Shuhama, Kashmir for a comprehensive evaluation of the growth performance of Corriedale sheep under Indian (temperate) conditions to assess the random effect of sire and fixed effects of period, sex, and type of birth on its performance. All the 145 sires, during the study period, were selected from within the farm. Evaluation was done for 11 performance traits viz: birth weight (BW), weaning weight (WW), six months body weight (SMW), nine months body weight (NMW), yearling body weight (YBW), average daily gain from birth to weaning (ADG-1), metabolic mass at weaning (WW0.75), Kleiber ratio from birth to weaning (KR-1), average daily gain from weaning to yearling age (ADG-2), and metabolic mass at yearling age (YBW0.75) and Kleiber ratio from weaning to yearling age (KR-2). The overall least-squares means for BW, WW, SMW, NMW, YBW, ADG-1, WW0.75, KR-1, ADG-2, YBW0.75 and KR-2 were 3.66 ± 0.02 kg, 13.48 ± 0.14 kg, 18.79 ± 0.25 kg, 21.96 ± 0.19 kg, 25.23 ± 0.19 kg, 109.0.21 ± 1.56 gm/day, 7.01 ± 0.06 kg, 15.29 ± 0.10, 41.49 ± 0.42 gm/day, 11.23 ± 0.07 kg and 3.64 ± 0.29, respectively. The effect of sire and period was significant (p < 0.01) whereas effect of birth type was non-significant on all the traits. The effect of sex of animal was significant on growth performance traits and males were heavy at all age than females. The heritability estimates ranged from low to high indicated low to genetic variability. The genetic and phenotypic correlations between different traits also range from low to very high. The average breeding values of sires were 3.69 ± 0.02 kg, 13.46 ± 0.09 kg, 18.41 ± 0.15 kg, 21.73 ± 0.12 kg, 25.12 ± 0.12 kg, 108.66 ± 0.93 gm/day, 7.01 ± 0.03 kg, 15.24 ± 0.07, 41.75 ± 0.33 gm/day, 11.22 ± 0.03 kg and 3.67 ± 0.02 for BW, WW, SMW, NMW, YBW, ADG-1, WW0.75, KR-1, ADG-2, YBW0.75 and KR-2, respectively. The negative phenotypic and genetic trends were observed for all traits except KR-2. The environmental trend was positive for SMW, NMW, YMW, ADG-1 and KR-2. The results indicate selection based on SMW may improve growth performance in this flock as the trait has high heritability and positive genetic and phenotypic correlations with other body weight and growth performance traits. An optimal strategy for selection considering both genetic merits and coancestry of mates (avoiding close breeding) may be adopted which is also in consonance with the current breeding policy of the J&K.

Genome-wide scan highlights the role of candidate genes on phenotypic plasticity for age at first calving in Nellore heifers

Age at first calving (AFC) plays an important role in the economic efficiency of beef cattle production. This trait can be affected by a combination of genetic and environmental factors, leading to physiological changes in response to heifers’ adaptation to a wide range of environments. Genome-wide association studies through the reaction norm model were carried out to identify genomic regions associated with AFC in Nellore heifers, raised under different environmental conditions (EC). The SNP effects for AFC were estimated in three EC levels (Low, Medium, and High, corresponding to average contemporary group effects on yearling body weight equal to 159.40, 228.6 and 297.6 kg, respectively), which unraveled shared and unique genomic regions for AFC in Low, Medium, and High EC levels, that varied according to the genetic correlation between AFC in different EC levels. The significant genomic regions harbored key genes that might play an important biological role in controlling hormone signaling and metabolism. Shared genomic regions among EC levels were identified on BTA 2 and 14, harboring candidate genes associated with energy metabolism (IGFBP2, IGFBP5, SHOX, SMARCAL1, LYN, RPS20, MOS, PLAG1, CHCD7, and SDR16C6). Gene set enrichment analyses identified important biological functions related to growth, hormone levels affecting female fertility, physiological processes involved in female pregnancy, gamete generation, ovulation cycle, and age at puberty. The genomic regions highlighted differences in the physiological processes linked to AFC in different EC levels and metabolic processes that support complex interactions between the gonadotropic axes and sexual precocity in Nellore heifers.

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.

Genomic reaction norm models exploiting genotype×environment interaction on sexual precocity indicator traits in Nellore cattle.

Brazilian beef cattle are raised predominantly on pasture in a wide range of environments. In this scenario, genotype by environment (G×E) interaction isan important source of phenotypic variation in the reproductive traits. Hence, the evaluation of G×E interactions for heifer's early pregnancy (HP) and scrotal circumference (SC) traits in Nellore cattle, belonging to three breeding programs, was carried out to determine the animal's sensitivity to the environmental conditions (EC). The dataset consisted of 85874 records for HP and 151553 records for SC, from which 1800 heifers and 3343 young bulls were genotyped with the BovineHD BeadChip. Genotypic information for 826 sires was also used in the analyses. EC levels were based on the contemporary group solutions for yearling body weight. Linear reaction norm models (RNM), using pedigree information (RNM_A) or pedigree and genomic information (RNM_H), were used to infer G×E interactions. Two validation schemes were used to assess the predictive ability, with the following training populations: (a) forward scheme-dataset was split based on year of birth from 2008 for HP and from 2011 for SC; and (b) environment-specific scheme-low EC (-3.0 and -1.5) and high EC (1.5 and 3.0). The inclusion of the H matrix in RNM increased the genetic variance of the intercept and slope by 18.55 and 23.00% on average respectively, and provided genetic parameter estimates that were more accurate than those considering pedigree only. The same trend was observed for heritability estimates, which were 0.28-0.56 for SC and 0.26-0.49 for HP, using RNM_H, and 0.26-0.52 for SC and 0.22-0.45 for HP, using RNM_A. The lowest correlation observed between unfavorable (-3.0) and favorable (3.0) EC levels were 0.30 for HP and -0.12 for SC, indicating the presence of G×E interaction. The G×E interaction effect implied differences in animals' genetic merit and re-ranking of animals on different environmental conditions. SNP marker-environment interaction was detected for Nellore sexual precocity indicator traits with changes in effect and variance across EC levels. The RNM_H captured G×E interaction effects better than RNM_A and improved the predictive ability by around 14.04% for SC and 21.31% for HP. Using the forward scheme increased the overall predictive ability for SC (20.55%) and HP (11.06%) compared with the environment-specific scheme. The results suggest that the inclusion of genomic information combined with the pedigree to assess the G×E interaction leads to more accurate variance components and genetic parameter estimates.

Genome-wide scan reveals population stratification and footprints of recent selection in Nelore cattle

BackgroundThis study aimed at (1) assessing the genomic stratification of experimental lines of Nelore cattle that have experienced different selection regimes for growth traits, and (2) identifying genomic regions that have undergone recent selection. We used a sample of 763 animals genotyped with the Illumina BovineHD BeadChip, among which 674 animals originated from two lines that are maintained under directional selection for increased yearling body weight and 89 animals from a control line that is maintained under stabilizing selection.ResultsMultidimensional analysis of the genomic dissimilarity matrix and admixture analysis revealed a substantial level of population stratification between the directional selection lines and the stabilizing selection control line. Two of the three tests used to detect selection signatures (FST, XP-EHH and iHS) revealed six candidate regions with indications of selection, which strongly indicates truly positive signals. The set of identified candidate genes included several genes with roles that are functionally related to growth metabolism, such as COL14A1, CPT1C, CRH, TBC1D1, and XKR4.ConclusionsThe current study identified genetic stratification that resulted from almost four decades of divergent selection in an experimental Nelore population, and highlighted autosomal genomic regions that present patterns of recent selection. Our findings provide a basis for a better understanding of the metabolic mechanism that underlies the growth traits, which are modified by selection for yearling body weight.

Estimation of genetic parameters for production traits in Munjal sheep

Astudy was carried out to estimate the genetic parameters of production traits in Munjal sheep using 16 years (2001–2016) data of 462 sheep maintained at Lala Lajpat Rai University of Veterinary and Animal Sciences, Hisar Mixed model analysis included the sire as a random effect and effects of period of birth, sex, dam's age at lambing as fixed effects. Heritability estimates and genetic correlations for different traits were calculated by paternal half-sib correlation method using sire components of variance and covariance. Period of birth and sex of lamb had significant effect (P<0.05) on all traits except greasy fleece weight (GFW). Dam's age at lambing had significant (P<0.05) effect only on birth weight. The overall least squares means of production traits recorded for birth weight (BW), weaning weight (WW), six months body weight (SMW), yearling body weight (YBW) and annual GFW were 4.1±0.07, 15.57±0.22, 20.79±0.53, 26.40±0.41 and 1.84±0.04 kg, respectively and the corresponding heritability estimates were 0.35±0.18, 0.48±0.20, 0.57±0.24, 0.48±0.25 and 0.52±0.22, respectively. Genetic correlations among production traits were positive and low to high in magnitude (0.10±0.05 to 0.76±0.05) and the highest genetic correlation of 0.76±0.05 was found between SMW and YBW. Phenotypic correlations among various production traits were found to be positive and significant ranging from 0.17±0.04 to 0.81±0.03. It was concluded that selection on the basis of SMW would be the best approach to improve growth performance in Munjal sheep as the trait has high heritability and positive genetic correlation with other body weights.

Genetic analysis of performance traits in Harnali sheep

Harnali sheep is a new synthetic strain developed for superior carpet wool, better growth and adaptability. The present investigation was undertaken to evaluate the Harnali sheep for seven performance traits namely birth weight (BW), weaning weight (WW), six month body weight (SMW) , yearling body weight (YBW), adult body weight (ABW), age at first lambing (AFL) and grease fleece weight (GFW) with a mixed model methodology. The overall least squares means for BW, WW, SMW, YBW, ABW, GFW and AFL were estimated as 3.51±0.58 kg, 13.61±0.22 kg, 19.45±0.24 kg, 27.26±0.31 kg, 37.90±0.34 kg, 1662.65±35.46 gm and 789.98±10.40 days, respectively. The period of birth had significant effect on all the performance traits except GFW. The effect of sex was found significant on all the performance traits. The male lambs were significantly heavier than females at all ages. The effect of dam’s age at lambing was found non-significant on all the performance traits but dam’s weight at lambing significantly influenced all the performance traits and indicated heavier lambs born from heavier ewes. Heritability estimates were high for BW, WW, SMW, YBW, ABW and GFW as 0.68±0.19, 0.49±0.17, 0.65±0.15, 0.44±0.17, 0.42±0.17 and 0.54±0.17, respectively while moderate estimates was obtained for AFL as 0.38±0.16. The phenotypic correlations of WW and SMW were significant and positive with BW, YBW and ABW with moderate to high in magnitude ranging from 0.22±0.04 to 0.71±0.07. The phenotypic correlation between BW and SMW was high and positive (0.71±0.07). The genetic correlations among performance traits were low to high ranging from -0.03±0.04 to 0.61±0.12. Keeping in view the heritability and genetic correlations among performance traits it is concluded that SMW can serve as a good selection criterion in sheep at early age as it has high heritability and positive and high correlations with body weights at later ages and favourable correlation with age at first lambing.

Genetic analysis of growth traits in Harnali sheep.

Aim:The present investigation was to study genetic characteristics of Harnali sheep with respect to growth performance and to estimate genetic parameters.Materials and Methods:The 22 years (1992-2013) data of growth traits of a 1603 synthetic population of Harnali sheep maintained at Lala Lajpat Rai University of Veterinary and Animal Sciences, Hisar, was utilized for this study. A mixed methodology with regression on their dam's weight was used to study the effect of non-genetic factors on growth traits. Heritability, genetic and phenotypic correlations were estimated using paternal half-sib analysis for body weight at various ages and average daily gain (ADG) for different growth periods.Result:The overall least squares mean of body weights recorded for birth weight (BW), weaning weight (WW), six months body weight (SMW), one yearling body weight (YBW), average daily gain from birth to 3 months (ADG1) and average daily gain from 3 to 12 months (ADG2) were 3.35±0.05 kg, 12.41±0.08 kg, 16.30±0.12 kg, 21.88±0.08 kg, 100.66±0.86 g/day and 35.07±0.39 g/day, respectively. The effects of year of birth significantly (p<0.01) influenced the BW, WW, SMW, YWB, ADG1 and ADG2. The effects of sex of lamb significantly (p<0.01) influenced the BW, WW SMW, YWB, ADG1 and ADG2. The effects of dam's weight at lambing significantly (p<0.01) influenced BW, WW, SMW, YWB, ADG1 and ADG2. No definite trend was observed over the years for the averages of body weight and gain. The heritability estimates of BW, WW, SMW, YBW, ADG1 and ADG2 were 0.40±0.05, 0.38±0.05, 0.45±0.06, 0.29±0.05, 0.40±0.06 and 0.33±0.02, respectively. The male lambs were significantly heavier than females at all stages of growth. The heritability estimates were moderate for all the growth traits and high genetic correlations of BW and WW with SMW were found.Conclusion:Due to high heritability and positive correlations of SMW with other body weights and daily gain, it was concluded that selection on the basis of SMW would be the best approach to improve growth performance in Harnali sheep.

Estimates of genetic parameters for worm resistance, wool and growth traits in Merino sheep of Uruguay

The genotype of an individual and the environment as the maternal ability of its dam have substantial effects on the phenotype expression of many production traits. The aim of the present study was to estimate the (co)variance components for worm resistance, wool and growth traits in Merino sheep, testing the importance of maternal effects and to determine the most appropriate model for each trait. The traits analyzed were Greasy Fleece Weight (GFW), Clean Fleece Weight (CFW), average Fibre Diameter (FD), Coefficient of Variation of FD (CVFD), Staple Length (SL), Comfort Factor (CF30), Weaning Weight (WWT), Yearling Body Weight (YWT) and Faecal worm Egg Count (FEC). The data were recorded during a 15-year period from 1995 to 2010, from Uruguayan Merino stud flocks. A Bayesian analysis was performed to estimate (co)variance components and genetic parameters. By ignoring or including maternal genetic or environmental effects, five different univariate models were fitted in order to determine the most effective for each trait. For CVFD and YWT, the model fitting the data best included direct additive effects as the only significant random source of variation. For GFW, CFW, FD, SL and CF30 the most appropriate model included direct-maternal covariance; while for FEC included maternal genetics effects with a zero direct-maternal covariance. The most suitable model for WWT included correlated maternal genetic plus maternal permanent environmental effects. The estimates of direct heritability were moderate to high and ranged from 0.15 for log transformed FEC to 0.74 for FD. Most of the direct additive genetic correlation (rg) estimations were in the expected range for Merino breed. However, the estimate of rg between FEC and FD was unfavourable (−0.18±0.03). In conclusion, there is considerable genetic variation in the traits analyzed, indicating the potential to make genetic progress on these traits. This study showed that maternal effects are influencing most of traits analyzed, thus these effects should be considered in Uruguayan Merino breeding programs; since the implementation of an appropriate model of analysis is critical to obtain accurate estimates.

Across flock genetic parameter estimation for yearling body weight and fleece

Accurate genetic parameter estimates are needed upon which to perform multiple-trait across flock breed analyses. Genetic parameters for yearling body weight (BW), clean fleece weight (CFW) and mean fibre diameter (MFD) were estimated using records of 107 389 individuals (the progeny of 1 530 sires and 45 178 dams) collected between 1992 and 2004 in the South African Dohne Merino population. Fixed effects included in the model were flock-year-season-sex-management group (1 594 classes), type of birth (singles, multiples), age of dam (2 - 7+ years) and age at measurement, fitted as a linear covariate (385 ± 12 days). Six different single-trait animal models were fitted, where different combinations of the following random effects were fitted: direct additive, the sire-flock interaction, the sire-flock-year-season interaction (SFYS), the dam genetic effect, the direct-maternal correlation and the dam permanent environmental effect. These analyses were followed by a three-trait analysis structured according to the log likelihood ratios obtained for the single-trait analysis. This analysis allowed the calculation of relevant correlations among traits together with their respective standard errors. Direct heritability estimates from the three-trait analysis were 0.17 for BW, 0.19 for CFW and 0.45 for MFD. Maternal heritability estimates were 0.01 for BW and 0.006 for CFW, with corresponding dam permanent environmental ratios of respectively 0.03 and 0.02. The genetic correlation between animal effects amounted to 0.48 for BW. Derived proportions of the total phenotypic variance due to SFYS were 0.02, 0.02 and 0.02, respectively. Genetic correlations of BW with CFW and MFD were 0.11 and 0.13, respectively, and of CFW with MFD 0.16. It was concluded that the inclusion of some form of a genotype by environmental interaction as part of the national evaluation is essential, although it controlled only a modest portion of the overall phenotypic variation.

Short Communication Inbreeding in the Dohne Merino breed in South Africa

The actual level of inbreeding and the effect of inbreeding depression on yearling body weight and fleece traits in the South African Dohne Merino population were investigated. All available pedigree data, which comprised of 266 268 records (302 169 animals including base parents) for the period 1975 to 2003 were used for calculating individual inbreeding coefficients. Inbreeding depression was estimated as the regression of performance (corrected for fixed effects) on the individual and dam inbreeding coefficients, fitting an animal model. The rate of inbreeding (∆F) was estimated as the difference between the individual inbreeding (Ft) and the inbreeding of the parents (Ft-1) divided by (1-Ft-1). The level of inbreeding (F) in the SA Dohne Merino sheep population is very low. The proportion of animals that was inbred to some extent increased from 0.00 (average F = 0) in 1980 to 0.38 in 2003 (average F = 0.012). No significant inbreeding depression on body weight and fleece traits could be found. In general the results suggest that inbreeding at present is not a serious problem in the South African Dohne Merino breed.