Genetics of flight time and other measures of temperament and their value as selection criteria for improving meat quality traits in tropically adapted breeds of beef cattle

Flight time, an objective measure of temperament, was recorded in 3594 Brahman, Belmont Red, and Santa Gertrudis heifers and steers. Two subjective measures of temperament (crush score and flight speed score) were also available for over 2000 of these animals. Temperament measures were recorded post-weaning (average age 8 months) and again at the start of finishing (average age 19 months) on a subset of the animals. Nine meat quality traits were measured on these animals and included measures on 2 different muscles [M. longissimus thoracis et lumborum (LTL) and M. semitendinosus (ST)]. The heritability of flight time measured post-weaning and at the start of finishing was 0.30 and 0.34, respectively, with a repeatability of 0.46 across the measurement times. Heritabilities for scored temperament traits were 0.21, 0.19, and 0.15 for post-weaning flight speed score, post-weaning crush score, and start of finishing crush score, respectively. Genetic correlations across measurement times for flight time were 0.98 and 0.96 for crush score, indicating a strong underlying genetic basis of these temperament measures over time; however, the corresponding phenotypic correlations were lower (0.48 and 0.37, respectively). Longer flight times (i.e. better temperament) were genetically correlated with improved tenderness (i.e. lower shear force and higher tenderness scores), with genetic correlations of –0.42 and 0.33 between LTL shear force, and Meat Standards Australia (MSA) tenderness, respectively. Genetic correlations between post-weaning crush score and the same meat quality traits were 0.39 and –0.47, respectively. However, genetic and phenotypic correlations between measures of temperament and other meat quality traits were generally low, with the exception of crush scores with LTL Minolta a* value (–0.37 and –0.63 for post-weaning and start of finishing measurement time, respectively). Predicted correlated responses of –0.17 kg LTL shear force and 2.6 MSA tenderness points per generation were predicted based on the genetic parameter estimates and a recording regime of both flight time and crush scores. Selection based on the measures of temperament described in this study could be used to improve temperament itself and correlated improvements can also occur in meat tenderness and eating quality traits in tropically adapted breeds of cattle.

Download Full-text

Relationship between sire estimated breeding values and the meat and eating quality of meat from their progeny grown on two planes of nutrition

Australian Journal of Experimental Agriculture ◽

10.1071/ea03175 ◽

2005 ◽

Vol 45 (5) ◽

pp. 525 ◽

Cited By ~ 45

Author(s):

D. L. Hopkins ◽

R. S. Hegarty ◽

T. C. Farrell

Keyword(s):

Meat Quality ◽

Shear Force ◽

Best Practice ◽

Intramuscular Fat ◽

Eating Quality ◽

Quality Traits ◽

Breeding Values ◽

Meat Quality Traits ◽

Estimated Breeding Values

The meat of 140 female lambs was examined. These lambs were sired by 9 Poll Dorset sires (3 selected for growth, 3 for muscling and 3 control) and fed either a low or high plane of nutrition from birth to slaughter. All carcasses were electrically stimulated and portions of M. longissimus thoracis et lumborum (loin) aged for 5 days before freezing. Subsequently, 10 consumers tested each portion for eating quality traits. A portion of the same muscle from the opposing side of the carcass was divided into 3 sections and aged for either 1, 3 or 5 days and then used to measure shear force (objective tenderness). Portions of the M. semimembranosus (topside) were also aged for 3 or 5 days and subjected to shear testing. Low plane animals produced tougher loins (based on shear force). As ultimate pH increased, shear force of the loin increased for low plane animals, while for high plane animals there was no such effect. This latter group had significantly lower ultimate pH values in all 3 muscles tested. Plane of nutrition had the greatest effect on topside shear force with low plane lambs producing tougher topsides. As ultimate pH increased, the topsides became tougher and as expected ageing improved the tenderness. There was no effect of sire EBVs (estimated breeding values) on shear force or objective meat quality traits apart from loin lightness which increased as the EBV for post-weaning weight (PWWT) increased and intramuscular fat in the loin which decreased as sire EBV for post-weaning muscle depth (PEMD) increased. Plane of nutrition did not have a significant effect on eating quality attributes as assessed by consumers. There was, however, an effect of sire EBV for muscling (PEMD) on tenderness, juiciness, flavour and overall liking, such that increased EBV led to decreased scores for the sensory traits. The findings suggest selection of sires for increasing PEMD will have a detrimental affect on the eating quality of their progeny, but this will not be reflected in shear force values or other objective meat quality traits apart from intramuscular fat. The effects of a low plane of nutrition on eating quality were minimal and largely controlled by the use of best practice processing, but were evident for a number of meat quality traits.

Download Full-text

Genetic and phenotypic characterisation of animal, carcass, and meat quality traits from temperate and tropically adapted beef breeds. 4. Correlations among animal, carcass, and meat quality traits

Australian Journal of Agricultural Research ◽

10.1071/ar02088 ◽

2003 ◽

Vol 54 (2) ◽

pp. 149 ◽

Cited By ~ 73

Author(s):

A. Reverter ◽

D. J. Johnston ◽

D. M. Ferguson ◽

D. Perry ◽

M. E. Goddard ◽

...

Keyword(s):

Meat Quality ◽

Carcass Traits ◽

Genetic Correlations ◽

Quality Measures ◽

Quality Traits ◽

Eye Muscle ◽

Phenotypic Correlations ◽

Meat Quality Traits ◽

Genetic And Phenotypic Correlations ◽

Meat Colour

Beef cattle data from temperate (TEMP, n = 3947) and tropically (TROP, n = 4137) adapted breeds were analysed to compute estimates of genetic and phenotypic correlations between animal, abattoir carcass, and meat quality measures. Live animal traits included: liveweight (S2LWT), scanned subcutaneous rump fat depth (S2P8), scanned eye muscle area (S2EMA), flight time (S1FT), and finishing average daily gain (FADG). Carcass traits included: hot carcass weight (CWT), retail beef yield percentage (RBY), intramuscular fat percentage (IMF), subcutaneous rump fat depth (P8), eye muscle length by width (ELW), and meat colour score (MEATC). Meat quality measures taken on 2 muscles [M. longissimus thoracis et lumborum (LTL) and M. semitendinosus (ST)] included: shear force of LTL (LTL_SF) and ST (ST_SF); compression of the ST (ST_C); cooking loss % of the LTL (LTL_CL%) and ST (ST_CL%); Minolta LTL L* (LTL_L*), a* (LTL_a*), ST a* (ST_a*); and consumer-assessed LTL tenderness score (LTL_TEND). Genetic and phenotypic correlations between animal measures and related carcass traits were moderate to very high for TEMP and TROP. Genetic correlations between S2LWT and CWT were 0.89 and 0.82, between S2P8 and P8 0.80 and 0.88, and between S2EMA and ELW 0.62 and 0.68, for TEMP and TROP, respectively. Genetic correlations between animal measures and other carcass traits varied; moderate genetic correlations were estimated between S2P8 and RBY (–0.57, –0.19 for TEMP, TROP) and S2P8 and IMF (0.39, 0.23 for TEMP, TROP). Genetic correlations between animal and meat quality measures were moderate to low. For TEMP, moderate genetic correlations were estimated between S2P8 and LTL_TEND (0.38), FADG and ST_a* (–0.49), and FADG and LTL_TEND (0.45); and for TROP, S1FT and LTL_SF (–0.54), and S2EMA and LTL_L* (–0.46). Phenotypic correlations between animal and meat quality were generally low and close to zero. Several moderate to high genetic correlations existed between carcass and meat quality traits. In general, fatness measures were genetically correlated with tenderness (e.g. IMF and LTL_TEND 0.61, 0.31 for TEMP, TROP). CWT was genetically correlated with meat colour (CWT and LTL_L* 0.66, 0.60 for TEMP, TROP) and objective tenderness measures (CWT and ST_C –0.52, –0.22 for TEMP, TROP). Once again phenotypic correlations between carcass and meat quality were low, indicating that few phenotypic predictors of meat quality traits were identified. Several of the genetic correlations show that both animal and abattoir carcass traits may be of use as indirect measures for carcass and meat quality traits in multiple trait genetic evaluation systems.

Download Full-text

Genetic and phenotypic characterisation of animal, carcass, and meat quality traits from temperate and tropically adapted beef breeds. 3. Meat quality traits

Australian Journal of Agricultural Research ◽

10.1071/ar02087 ◽

2003 ◽

Vol 54 (2) ◽

pp. 135 ◽

Cited By ~ 50

Author(s):

D. J. Johnston ◽

A. Reverter ◽

D. M. Ferguson ◽

J. M. Thompson ◽

H. M. Burrow

Keyword(s):

Meat Quality ◽

Shear Force ◽

Genetic Correlations ◽

Cooking Loss ◽

Objective Measures ◽

Phenotypic Variance ◽

Quality Traits ◽

Genetic Expression ◽

Meat Quality Traits ◽

Meat Colour

Meat quality measures, including objective measures of tenderness (shear force and compression), were taken on 2 muscles [M. longissimus thoracis et lumborum (LTL) and M. semitendinosus (ST)] from 7566 carcasses from temperate (TEMP) and tropically adapted (TROP) beef cattle breeds. Animals were finished to 1 of 3 market carcass weight end-points (220, 280, or 340 kg) either on pasture or in a feedlot, and in 2 different geographic regions for TROP. Both the phenotypic and genetic expression of the traits were estimated at each market weight and for each finishing regime. Heritabilities and correlations between the traits were estimated for TEMP and TROP separately. Smaller additive variances and heritabilities were observed for temperate breeds compared with tropically adapted breeds for most of the traits studied. For TROP, the heritability of traits measured on the ST muscle [compression (ST_C), shear force (ST_SF), and L* Minolta lightness value (ST_L*)] was 0.27, 0.42, and 0.16, respectively, and for traits measured on the LTL muscle [compression (LTL_C), shear force (LTL_SF), L* Minolta lightness value (LTL_L*), a* Minolta redness value (LTL_a*), cooking loss% (LTL_CL%), and consumer assessed tenderness score (LTL_TEND)] 0.19, 0.30, 0.18, 0.13, 0.20, and 0.31, respectively. For TEMP, the heritability of traits measured on the ST muscle [ST_C, ST_SF, ST_L*, a* Minolta redness value (ST_a*), cooking loss % (ST_CL%)] was 0.12, 0.11, 0.17, 0.13, and 0.15, respectively, and of traits measured on the LTL muscle (LTL_C, LTL_SF, LTL_L, and LTL_TEND) were 0.08, 0.09, 0.17 and 0.18 respectively. Genetic correlations were moderate to high for tenderness measures (shear force and compression) between muscles for the same tenderness measure (e.g. LTL_SF and ST_SF was 0.46 for TROP) and within a muscle for the different measures (e.g. ST_C and ST_SF was 0.83 for TROP). Phenotypic and genetic correlations between LTL_L* and all objective measures of tenderness were negative (e.g. LTL_SF and LTL_L* for TROP was –0.40). The genetic relationship between LTL_SF and LTL_TEND was –0.79 and –0.49 for TROP and TEMP, respectively. Finishing system affected the phenotypic expression of all traits. Pasture-finished, compared with feedlot-finished, animals had higher shear force and compression measures, darker meat colour, and lower sensory tenderness scores for both TEMP and TROP. For TROP, heifers had higher shear force and compression measures, lower sensory tenderness scores, and darker meat colour (lower L* values) than steers. Genetic correlations between markets were generally high and close to unity with the exception of the ST_L*, LTL_L*, ST_C, and ST_SF for TEMP. Geographic region had little effect on the phenotypic and genetic expression of meat quality traits for TROP. Genetic correlations between finishing regimes for all traits were positive and close to unity, with the exception of ST_C and LTL_SF for TEMP, and LTL_L* and LTL_CL% for TROP. Genetic improvement of meat quality traits is a possibility for tropically adapted breeds given the moderate heritabilities, adequate phenotypic variance, generally favourable genetic correlations between traits, and little evidence of genotype by environment interactions.

Download Full-text

PSVIII-32 Estimates of genetic parameters for sub-primal and meat quality traits in Canadian commercial crossbred swine populations

Journal of Animal Science ◽

10.1093/jas/skz258.549 ◽

2019 ◽

Vol 97 (Supplement_3) ◽

pp. 270-271

Author(s):

Prince P Opoku ◽

Bimol Roy ◽

Graham Plastow ◽

huaigang Lei ◽

Chunyan Zhang ◽

...

Keyword(s):

Meat Quality ◽

Fixed Effects ◽

Genetic Relationships ◽

Genetic Correlations ◽

Eating Quality ◽

Quality Traits ◽

Muscle Weight ◽

Gene Effects ◽

Meat Quality Traits ◽

Insoluble Collagen

Abstract The hypothesis that genetic relationships exist between loin muscle collagen characteristics and sub-primal and meat quality traits was tested. Data from 500 pigs from crosses between Duroc sires and hybrid Large White ✕ Landrace sows with pedigree back to about eight generations were used. Significant fixed effects (slaughter group and company) and a random additive effect were fitted in bivariate animal models to estimate phenotypic and genetic correlations using ASReml 4.1. Moderate heritabilities were obtained for sub-primal traits ranging from 0.21 for bone weight to 0.44 for loin muscle weight with a low estimate of 0.10 being obtained for loin weight. Meat quality traits were low to moderately heritable with the highest estimate being found for intramuscular fat (0.42). The heritability estimates for percentages of heat soluble and insoluble collagen were 0.12 and 0.15, respectively, while 0.33 was found for total collagen. Moderate to relatively high heritabilities imply the possibility of improving these traits through selective breeding. In general, moderate to high phenotypic and genetic correlations were obtained for sub-primal traits, whilst meat quality traits had moderate phenotypic and moderate to high genetic correlations. Strong negative genetic correlations between moisture traits and fat traits and a further negative correlation between fat and muscling traits were estimated confirming that selecting for improved muscling over time can negatively affect fat traits and indirectly decrease meat eating quality. The strong genetic correlation between pH and L* (-0.95) suggested possible pleiotropic gene effects on these traits. Warner-Braztler shear force (WBSF) had moderate genetic correlations with insoluble collagen (0.42) and soluble collagen (-0.38) suggesting a potential relationship between some of the genes impacting these traits. Genetic correlations between WBSF and collagen characteristics indicate that despite the relative youthfulness of pigs at slaughter, genetic selection for collagen solubility may decrease pork toughness.

Download Full-text

Prediction of meat quality traits in the abattoir using portable near-infrared spectrometers: heritability of predicted traits and genetic correlations with laboratory-measured traits

Journal of Animal Science and Biotechnology ◽

10.1186/s40104-021-00555-5 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Simone Savoia ◽

Andrea Albera ◽

Alberto Brugiapaglia ◽

Liliana Di Stasio ◽

Alessio Cecchinato ◽

...

Keyword(s):

Meat Quality ◽

Near Infrared ◽

External Validation ◽

Genetic Correlations ◽

Genetic Selection ◽

Quality Traits ◽

Eye Muscle ◽

Meat Quality Traits ◽

Color Traits ◽

Selection Of

Abstract Background The possibility of assessing meat quality traits over the meat chain is strongly limited, especially in the context of selective breeding which requires a large number of phenotypes. The main objective of this study was to investigate the suitability of portable infrared spectrometers for phenotyping beef cattle aiming to genetically improving the quality of their meat. Meat quality traits (pH, color, water holding capacity, tenderness) were appraised on rib eye muscle samples of 1,327 Piemontese young bulls using traditional (i.e., reference/gold standard) laboratory analyses; the same traits were also predicted from spectra acquired at the abattoir on the intact muscle surface of the same animals 1 d after slaughtering. Genetic parameters were estimated for both laboratory measures of meat quality traits and their spectra-based predictions. Results The prediction performances of the calibration equations, assessed through external validation, were satisfactory for color traits (R2 from 0.52 to 0.80), low for pH and purge losses (R2 around 0.30), and very poor for cooking losses and tenderness (R2 below 0.20). Except for lightness and purge losses, the heritability estimates of most of the predicted traits were lower than those of the measured traits while the genetic correlations between measured and predicted traits were high (average value 0.81). Conclusions Results showed that NIRS predictions of color traits, pH, and purge losses could be used as indicator traits for the indirect genetic selection of the reference quality phenotypes. Results for cooking losses were less effective, while the NIR predictions of tenderness were affected by a relatively high uncertainty of estimate. Overall, genetic selection of some meat quality traits, whose direct phenotyping is difficult, can benefit of the application of infrared spectrometers technology.

Download Full-text

41 Estimating the heritability of meat quality traits in turkeys

Journal of Animal Science ◽

10.1093/jas/skaa278.035 ◽

2020 ◽

Vol 98 (Supplement_4) ◽

pp. 18-19

Author(s):

Ryley J Vanderhout ◽

Michelle Yahiro ◽

Benjamin Wood ◽

Shai Barbut ◽

Jeff S Mohr ◽

...

Keyword(s):

Meat Quality ◽

Shear Force ◽

Live Weight ◽

Drip Loss ◽

Quality Traits ◽

Breast Meat ◽

Meat Yield ◽

Meat Quality Traits ◽

White Striping ◽

Breast Meat Yield

Abstract Genetic selection for improved meat quality traits has been successfully implemented in many livestock species. The objective of this study was to estimate the heritability of several meat quality traits to assess their selection potential in turkeys. Pedigree toms (n = 1,033) were processed at a commercial facility and live weight, breast meat yield (as a percentage of live weight), ultimate pH, color (CIELAB values), drip loss, cooking loss, and shear force were recorded on M. pectoralis superficialis (fillet). White striping was also rated on a 1–4 scale. Heritabilities were estimated using univariate animal models in ASReml version 4.1. Hatch week and age at slaughter were included as fixed effects in the mode,l and 32 generations of pedigree records were used. Breast meat yield (h2 = 0.62; SE = 0.090) showed the highest heritability and was higher compared to previous estimates, probably due to the smaller sample size. Live weight (h2 = 0.31; SE = 0.078), ultimate pH (h2 = 0.36; SE = 0.087), lightness (h2 = 0.28; SE = 0.086), redness (h2 = 0.22; SE = 0.075), and white striping score (h2 = 0.27; SE = 0.085) all had moderate heritabilities. The estimate for ultimate pH was similar to previous studies in broilers but was high compared to previous studies in turkeys. Estimates for color were similar to those found in previous studies involving turkeys. Drip loss and cooking loss had similar heritability estimates of 0.13 (SE = 0.071) and 0.10 (SE = 0.064), respectively, which were akin to previous estimates in pork. Shear force (h2 = 0.02; SE = 0.056) was found to have a very low heritability. In conclusion, the heritability estimates provided in this study show great potential for the inclusion of meat quality traits in selection programs of turkeys. This study is part of a larger project working towards the implementation of genomic information in the selection of turkeys for improved meat quality.

Download Full-text

Phenotypic correlations among meat quality traits in broilers

Ciência Rural ◽

10.1590/s0103-84782011000800029 ◽

2011 ◽

Vol 41 (8) ◽

pp. 1475-1481 ◽

Cited By ~ 2

Author(s):

Luana Bertollini de Jesus Silva ◽

Leila de Genova Gaya ◽

Ana Paula Madureira ◽

Graziela Tarôco ◽

José Bento Sterman Ferraz ◽

...

Keyword(s):

Meat Quality ◽

Protein Denaturation ◽

The Other ◽

Poultry Meat ◽

Quality Traits ◽

Ph Measurements ◽

Water Losses ◽

Phenotypic Correlations ◽

Meat Quality Traits ◽

Initial Ph

The goals of this research were to estimate the phenotypic correlations among various meat quality traits from a male broiler line and to describe the relation among these variables. Phenotypical correlations were determined among quality traits, isolating the effects of slaughter date, the age of the mother and sex. The evaluated traits were pH measurements taken at time 0 and at 6 and 24 hours after slaughtering, color parameters, water loss due to exudation, thawing and cooking of the meat, and shear force. Important associations (P<0.01) were found to be significant and, in most cases, weak or moderate, varying from -0.35 to 0.28. The initial pH of the meat was not associated (P>0.05) to the other traits of the meat, whereas the pH at 24 hours after slaughter was able of directly interfering with the attributes of the meat, since this trait was inversely related with lightness and water losses, which indicates an effect of pH fall along 24h after slaughtering on protein denaturation. This study demonstrates that the variables of poultry meat quality are related and that there is a phenotypical association between lightness and cooking losses and the other attributes of the meat. The pH at 24 hours after slaughtering, lightness and cooking losses could be efficient meat quality indicators in this broiler line.

Download Full-text

Differences in carcass traits, meat quality and chemical composition between the pigs of different CAST genotype

Animal Production Science ◽

10.1071/an14732 ◽

2016 ◽

Vol 56 (10) ◽

pp. 1745 ◽

Cited By ~ 2

Author(s):

I. Djurkin Kušec ◽

G. Kušec ◽

R. Vuković ◽

E. Has-Schön ◽

G. Kralik

Keyword(s):

Chemical Composition ◽

Meat Quality ◽

Shear Force ◽

Carcass Traits ◽

Muscle Thickness ◽

Intensity Level ◽

Quality Traits ◽

Calpain Activity ◽

Meat Quality Traits ◽

Pig Carcasses

The study was carried out on 89 Pig Improvement Co. (PIC) pig carcasses, with the aim to investigate the differences between three CAST loci in carcass and meat-quality traits, as well as chemical composition of longissimus dorsi (LD) muscle. The differences among genotypes at CAST/HinfI locus were significant in all carcass traits measured, where AB genotype exhibited preferable values in carcass lengths, ham length, muscle thickness, loin eye area, fat thickness and fat area. Among meat-quality traits analysed, genotypes at CAST/HinfI locus differed in pH45 in SM muscle, both pH24 in semimembranosus (SM) and LD muscles, as well as luminosity; genotypes at CAST/MspI differed in pH24 and EC24 measured at LD muscle and in red colour intensity, level of yellowness and hue angle; while genotypes at CAST/RsaI differed in pH45 and EC45 in SM muscle, pH24 in LD muscle, paleness and redness, as well as in shear force and calpain activity. EF genotype at this locus exhibited the highest pH values and the lowest CIE L*, with more pronounced red colour, but also highest shear force and lowest calpain activity values. Furthermore, significant differences in chemical composition of LD muscle were found only among genotypes at CAST/RsaI loci, where FF genotype had the lowest intramuscular fat and the highest relative share of protein.

Download Full-text

Genetic evaluation of crossbred lamb production. 4. Genetic parameters for first-cross animal performance

Australian Journal of Agricultural Research ◽

10.1071/ar06368 ◽

2007 ◽

Vol 58 (8) ◽

pp. 839 ◽

Cited By ~ 14

Author(s):

V. M. Ingham ◽

N. M. Fogarty ◽

A. R. Gilmour ◽

R. A. Afolayan ◽

L. J. Cummins ◽

...

Keyword(s):

Genetic Variation ◽

Meat Quality ◽

Mixed Models ◽

Fixed Effects ◽

Growth Traits ◽

Genetic Correlations ◽

Fibre Diameter ◽

Quality Traits ◽

Meat Quality Traits ◽

Lamb Growth

The study estimated heritability for lamb growth and carcass performance, hogget ewe wool production, and worm egg count among crossbred progeny of maternal breed sires, as well as the genetic and phenotypic correlations among the traits. The data were from crossbred progeny of 91 sires from maternal breeds including Border Leicester, East Friesian, Finnsheep, Coopworth, White Suffolk, Corriedale, and Booroola Leicester. The sires were mated to Merino ewes at 3 sites over 3 years (and also Corriedale ewes at one site), with 3 common sires used at each site and year to provide genetic links. These sheep comprised part of the national maternal sire central progeny test program (MCPT) to evaluate the genetic variation for economically important production traits in progeny of maternal and dual-purpose (meat and wool) sires and the scope for genetic improvement. The matings resulted in 7846 first-cross lambs born, with 2964 wether lambs slaughtered at an average age of 214 days, and wool data from 2795 hogget ewes. Data were analysed using univariate mixed models containing fixed effects for site, year, sex and type of birth and rearing, dam source and sire breed, and random terms for sire and dam effects. Heritabilities and genetic correlations were estimated based on variances from progeny of 70 sires by fitting the same mixed models using a REML procedure in univariate and multivariate analyses. Estimates of heritability were low for lamb growth traits (0.07–0.29), meat colour and meat pH (0.10–0.23), and faecal worm egg count (0.10), moderate for carcass fat and muscle traits (0.32–0.47), and moderate to high for wool traits (0.36–0.55). Estimates of direct genetic correlations among liveweights at various ages were high and positive (0.41–0.77) and those between liveweights and most carcass and meat quality traits were small and varied in sign. Liveweights were moderately to highly positively correlated with most wool traits, except fibre diameter (–0.28–0.08). The study indicates that there is genetic variation for wool, growth, carcass, and meat quality traits, as well as for faecal worm egg count, with scope for selection within Australian maternal sire breeds of sheep.

Download Full-text