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Extensive farming systems require beef cows to cope with varying environmental conditions while repeatedly producing calves. Cows use body energy reserves as a buffer in times of feed shortage and ...

Facial eczema (FE) is a significant metabolic disease that affects New Zealand ruminants. Ingestion of the mycotoxin sporidesmin leads to liver and bile duct damage, which can result in photosensitisation, reduced productivity and death. Strategies used to manage the incidence and severity of the disease include breeding. In sheep, there is considerable genetic variation in the response to FE. A commercial testing program is available for ram breeders who aim to increase tolerance, determined by the concentration of the serum enzyme, gamma-glutamyltransferase 21 days after a measured sporidesmin challenge (GGT21). Genome-wide association studies were carried out to determine regions of the genome associated with GGT21. Two regions on chromosomes 15 and 24 are reported, which explain 5% and 1% of the phenotypic variance in the response to FE, respectively. The region on chromosome 15 contains the β-globin locus. Of the significant SNPs in the region, one is a missense variant within the haemoglobin subunit β (HBB) gene. Mass spectrometry of haemoglobin from animals with differing genotypes at this locus indicated that genotypes are associated with different forms of adult β-globin. Haemoglobin haplotypes have previously been associated with variation in several health-related traits in sheep and warrant further investigation regarding their role in tolerance to FE in sheep. We show a strategic approach to the identification of regions of importance for commercial breeding programs with a combination of discovery, statistical and biological validation. This study highlights the power of using increased density genotyping for the identification of influential genomic regions, combined with subsequent inclusion on lower density genotyping platforms.

Nitrogen (N) leached into groundwater from urine patches of cattle grazing in situ is an environmental problem in pasture-based dairy industries. One potential mitigation is to breed cattle for lower urinary nitrogen (UN) excretion. Urinary nitrogen is difficult to measure, while milk urea nitrogen concentration (MUN) is relatively easy to measure. For animals fed diets of differing N content in confinement, MUN is moderately heritable and is positively related to UN. However, there is little information on the heritability of MUN, and its relationship with other traits such as milk yield and composition, for animals grazing fresh pasture. Milk urea nitrogen concentration data together with milk yield, fat, protein and lactose composition and somatic cell count was collected from 133 624 Holstein-Friesian (HF), Jersey (J) and HF×J (XBd) cows fed predominantly pasture over three full lactations and one part lactation. Mean MUN was 14.0; and 14.4, 13.2 and 13.9 mg/dl for HF, J and XBd cows, respectively. Estimates of heritability of MUN were 0.22 using a repeatability model that fitted year-of-lactation by month-of-lactation by cow-age with days-in-milk within month-of-lactation and cow-age, and 0.28 using a test-day model analysis with Gibbs sampling methods. Sire breeding values (BVs) ranged from -2.8 to +3.2 indicating that MUN could be changed by selection. The genetic correlation between MUN and percent true protein in milk was -0.22; -0.29 for J cows and -0.16 for HF cows. Should the relationship between MUN and UN observed in dietary manipulation studies hold similarly when MUN is manipulated by genetic selection, UN excretion could be reduced by 6.6 kg/cow per year in one generation of selection using sires with low MUN BVs. Although J cows had lower MUN than HF, total herd UN excretion may be similar for the same fixed feed supply because more J cows are required to utilise the available feed. The close relationship between blood plasma urea N concentration and MUN may enable early selection of bulls to breed progeny that excrete less UN.

Multi-sire mating of a mob of ewes is commonly used in commercial sheep production systems. However, ram mating success (defined as the number of lambs sired by an individual) can vary between rams in the mating group. If this trait was repeatable and heritable, selection of rams capable of siring larger numbers of lambs could reduce the number of rams required for mating and ultimately lead to increased genetic gain. However, genetic correlations with other productive traits, such as growth and female fertility, could influence the potential for ram mating success to be used as a selection trait. In order to investigate this trait, parentage records (including accuracy of sire assignment) from 15 commercial ram breeding flocks of various breeds were utilised to examine the repeatability and heritability of ram mating success in multi-sire mating groups. In addition, genetic and phenotypic correlations with growth and female fertility traits were estimated using ASReml. The final model used for the ram mating success traits included age of the ram and mating group as fixed effects. Older rams (3+years old) had 15% to 20% greater mating success than younger rams (1 or 2 years of age). Increasing the stringency of the criteria for inclusion of both an individual lamb, based on accuracy of sire assignment, or a whole mating group, based on how many lambs had an assigned sire, increased repeatability and heritability estimates of the ram mating success traits examined. With the most stringent criteria employed, where assignment of sire accuracy wasgt;0.95 and the total number of lambs in the progeny group that failed to have a sire assigned waslt;0.05, repeatability and heritability for loge(number of lambs) was 0.40±0.09 and 0.26±0.12, respectively. For proportion of lambs sired, repeatability and heritability were both 0.30±0.09. The two ram mating traits (loge(nlamb) and proportion) were highly correlated, both phenotypically and genetically (0.88±0.01 and 0.94±0.06, respectively). Both phenotypic and genetic correlations between ram mating success and growth and other female fertility traits were low and non-significant. In conclusion, there is scope to select rams capable of producing high numbers of progeny and thus increase selection pressure on rams to increase genetic gain.

This experiment was originally structured as a genome-wide screen for quantitative trait loci (QTL) affecting resistance or susceptibility to facial eczema disease (FE), a liver mycotoxicosis. Two Finnish Landrace (F) rams were crossed to three Texel (T) ewes to produce three cross-breed (designated F × T) rams. The F × T rams were then outcrossed to 210–230 Coopworth ewes each to generate three half-sib families, and 200 progeny per sire family were used in the FE QTL experiment. In a FE-phenotyping trial, the 600 five-month old lambs were orally challenged with a fixed dose rate of sporidesmin (FE mycotoxin) to determine their disease status. About 217 informative microsatellite markers, which were evenly spaced throughout the 26 ovine autosomes, were analysed in the FE study. Genotyping for the FE experiment was conducted in two stages: a primary and a secondary screen. In the initial primary screen, 46 most FE-resistant and 46 most FE-susceptible progeny of each sire family were selectively genotyped with the markers and analysed. Resulting chromosomes carrying suggestive and significant FE QTL were then followed up in a secondary screen when all progeny were genotyped for final analysis; there were seven chromosomes that underwent secondary screening, viz. OAR1, OAR2, OAR6, OAR13, OAR18, OAR19 and OAR20. During the FE-phenotyping trial period, mid-side wool samples were collected from the unshorn lambs for fibre measurement; the wool traits measured included yield, staple length (StapLen), crimp frequency, fibre curvature (FCurv), fibre opacity (FOpac), fibre diameter mean (FDMean) and fibre diameter standard deviation (FDsd). In a linkage analysis of wool traits, using the Haley–Knott regression method with the available “FE-generated” genotypes, a highly significant QTL for fibre opacity was detected on OAR20.

Genetic parameters for ewes were estimated for stayability (STAY) and productive life (Prodlife). Records from 658,871 animals from 241 seed stock or ram breeder flocks and one research flock were used to estimate parameters for ram breeder flock STAY and Prodlife. These flocks would have a culling policy based on criteria typical of a commercial enterprise, but including culls based on knowledge such as estimated breeding values. A subset of 35,688 of these animals from 4 ram breeder and one research flock was used to infer the animals that might be culled based on the perspective of a commercial flock as these flocks recorded reasons for culling. These data were used to estimate parameters for commercial flock STAY and Prodlife. Heritability for ram breeder flock STAY until age 3 to 6 yr ranged from 0.07 to 0.09. The heritability of commercial flock STAY was similar in yr 5 and 6, but lower at 0.05 (age 3) and 0.07 (age 4). Heritability of Prodlife for ram breeder flock and commercial flock was respectively 0.10 and 0.13. The genetic correlations between ram breeder flock STAY and commercial flock STAY ranged from 0.20 to 0.99. Both STAY and Prodlife were most correlated genetically with the trait number of lambs born, at about 0.4, and to a lesser degree, live weight up to the age of 12 mo for the traits analyzed with lower genetic correlations estimated for the commercial flocks. Live weight at 18 mo and fleece weight had little or no correlation with STAY and Prodlife. From the data set used to estimate genetic parameters from a ram breeder flock, 4,330 animals were genotyped with the Illumina OvineSNP50 BeadChip and the genotypes used to develop genomic predictions via genomic best linear unbiased prediction. The animals used in the training data set were multibreed, but were heavily Romney breed based. The genomic prediction accuracy for ram breeder flock STAY, according to breed, was dependent on sample size and ranged from 0.4 to 0.44 for Romney and 0.26 to 0.4 for Coopworth. Accuracies for Perendale and Composites, for which sample sizes were less, were more variable. This study has derived genetic parameters for STAY and Prodlife and investigated genomic predictions for these traits. As these traits are of low heritability, sex limited and expressed late in life genomic selection will be useful.

The goal was to estimate the heritabilities and genetic variances for pregnancy rate (PR) and calving date (CD) in Angus cattle along with the effect of weight, age, and sire on PR and CD. The data consisted of 4,999 records on PR and CD. Statistical models included year as a fixed effect; premating/postmating weight and age as covariates; and sire of embryo, maternal grandsire (MGS), and permanent maternal environmental effects as random effects. The models also included the interactions between herd and weight (weight change). Direct and maternal effects on PR and CD were estimated using sire MGS and animal models in REML. Pregnancy rate increased from age 2 to 6 and decreased from age 7 to 11 (P < 0.01) and this effect was independent of the culling strategy. There was a quadratic effect of premating cow weight independent of age on PR, with lower PR for low weights (P < 0.01). Overall, cows with a premating weight of 550 kg had the greatest PR. Cows that lost weight during mating had lower PR (P < 0.01). The maternal additive heritability for PR was 0.001 ± 0.012 and the direct additive heritability was 0.024 ± 0.020. The ratio of permanent maternal environmental variance to phenotypic variance was significant (0.048 ± 0.017; P < 0.01). This demonstrates that permanent maternal environmental effects play a major role in the repeatability of PR (0.049 ± 0.015; P < 0.01). The maternal additive heritability for CD was 0.040 ± 0.022, and the direct additive heritability was 0.076 ± 0.045. The ratio of permanent maternal environmental variance to phenotypic variance was low (0.014 ± 0.017) and the repeatability for CD was significant (0.0544 ± 0.0180; P < 0.01). This suggests that maternal genetic effects are as important as direct genetic effects on CD. There was a positive quadratic relationship between premating cow weight and CD with delayed calving for low/high weights (P < 0.01). Cows that lost weight over mating also had a later CD (P < 0.01). Comparisons of a weight-selected herd to the control herd showed differences (P < 0.05) in the optimal premating weight for early calving (control, 480 kg, and weight selected, 615 kg). Calving date was also more sensitive to changes in weight over mating in the weight selection herd (P < 0.05). Therefore, the set point in the weight-fertility axis and the sensitivity of fertility to changes in weight both changed in the weight selection herd.

The goal was to estimate the heritabilities and genetic variances for embryo and fetal survival (ES) in sheep along with the effect of premating ewe weight, age, and bilateral or unilateral ovulation on ES. The data consisted of 11,369 records on ovulation rate and litter size. Statistical models for ES included year and ovulation rate as fixed effects, premating ewe weight, and age as covariates, and sire of embryo, maternal grandsire (MGS), and permanent maternal environmental effects of the ewe as random effects. The variance components were estimated using REML. In ewes that survived to yr 6, the mean litter size was 1.87, 2.05, 2.01, 2.07, and 1.91 ± 0.04 in ewes of age 2, 3, 4, 5, and 6 yr, respectively. Litter size was less in ewes of age 2 and 6 yr compared to ewes of age 3, 4, and 5 yr (P < 0.01). Ovulation rate was lower at age 2 yr and increased from age 2 to 6 yr (P < 0.05). Two-year-old ewes had lower ES than 3-yr-old ewes (P < 0.01) and the probability of ES decreased after age 3 yr (P < 0.01). Thus, ES contributes significantly to lower fertility in 2-yr-old ewes. In ewes with high ovulation rates (i.e., 5 corpora lutea, CL), more balanced ovulations (i.e., 2 or 3 CL on each ovary) tended (P = 0.06) to be associated with increased ES. A quadratic relationship was observed between ewe weight and litter size (P < 0.01) and a positive linear relationship between premating ewe weight and ovulation rate (P < 0.01). A quadratic effect of ewe weight on ES was observed, with decreased ES for low and high ewe weights (P < 0.01). The optimal ewe weight for ES increased with ovulation rate, which is consistent with the requirement of greater body reserves for maintaining a larger number of fetuses during gestation. A quadratic relationship between ewe weight and the probability that a ewe is able to maintain a pregnancy was also observed (P < 0.05). Pregnancy loss is due to failure of the embryo or fetus or failure of the dam to maintain the pregnancy. The sire of the embryo only influences the embryo, whereas the MGS influences both the ewe and the embryo. The heritability for the direct additive effect on ES in ewes that lambed was 0.0081 ± 0.0139, and the heritability for the maternal additive effect was 0.0447 ± 0.0242. The permanent maternal environmental variance component was significant and explained 8.5% of the phenotypic variance. Thus, genetically, the dam's ability to maintain a pregnancy has 5.5 times the effect on pregnancy loss than the embryo's ability to survive, and this, in turn, was only half the size of the permanent environmental effect. Therefore, selection among dams based on the mean embryonic survival of their embryos will provide an effective way to improve embryonic survival.

Genetic responses of sheep and dairy cattle to the hepatic mycotoxin, sporidesmin, were reviewed. The mycotoxin can lead to clinical facial eczema (FE) in the most susceptible and severely challenged animals. The extent of hepatic injury is normally assessed from an enzyme secreted into the blood, gamma-glutamyltransferase (GGT). Latest heritability estimates for the natural logarithm of GGT level, 21 days or more after a sporidesmin challenge, were 0.45±0.03 in sheep and 0.34±0.02 in dairy cattle. Clinical FE follows from phylloerythrin (from chlorophyll) spilling over from the bile duct. Upon exposure to sunlight, phylloerythrin absorbs ultraviolet radiation, becoming reactive. Neither its concentration in blood nor clinical cases of FE are likely to be good indicators of liver damage from FE for ranking sires. Gaps in knowledge about genetic factors relating to FE susceptibility are highlighted.

Beef with yellow fat is considered undesirable by consumers in most European and Asian markets. β-Carotene is the major carotenoid deposited in the adipose tissue and milk fat of cattle (Bos taurus), which can result in the yellowness. The effects of retinal short-chain dehydrogenase reductase (RDHE2) and β, β-carotene 9',10-dioxygenase (BCO2) were considered jointly as major candidate genes for causing the yellow fat colour, based on their genomic locations in the fat colour quantitative trait loci (QTL) and their roles in the metabolism of β-carotene. In a secondary pathway, BCO2 cleaves β-carotene into retinoic acid, the most potent form of vitamin A. RDHE2 converts trans-retinol to trans-retinal, a less active form of vitamin A. We evaluated the effects of two amino acid variants of the RDHE2 gene (V6A and V33A) along with a mutation in the BCO2 gene that results in a stop codon (W80X) in seven cattle populations. The RDHE2 V6A genotype affected several fat colour traits but the size of the effect varied in the populations studied. The genotype effect of the RDHE2 V33A variant was observed only in New Zealand samples of unknown breed. In general, the individual effects of RDHE2 V6A and V33A SNPs genotypes were greater in the random New Zealand samples than in samples from pedigreed Jersey-Limousin backcross progeny, accounting for 8-17 % of the variance in one population. Epistasis between the BCO2 W80X and RDHE2 variants was observed, and in some populations this explained more of the variation than the effects of the individual RDHE2 variants.

Summary A whole-genome scan was carried out in New Zealand and Australia to detect quantitative trait loci (QTL) for live animal and carcass composition traits and meat quality attributes in cattle. Backcross calves (385 heifers and 398 steers) were generated, with Jersey and Limousin backgrounds. The New Zealand cattle were reared and finished on pasture, whilst Australian cattle were reared on grass and finished on grain for at least 180 days. This paper reports on meat quality traits (tenderness measured as shear force at 4‐5 ages on two muscles as well as associated traits of meat colour, pH and cooking loss) and a number of metabolic traits. For meat quality traits, 18 significant QTL (P < 0.05), located in nine linkage groups, were detected on a genome-wise basis, in combined-sire (seven QTL) or within-sire analyses (11 QTL). For metabolic traits, 11 significant QTL (P < 0.05), located in eight linkage groups, were detected on a genome-wise basis, in combined-sire (five QTL) or within-sire analyses (six QTL). BTA2 and BTA3 had QTL for both metabolic traits and meat quality traits. Six significant QTL for meat quality and metabolic traits were found at the proximal end of chromosome 2. BTA2 and BTA29 were the most common chromosomes harbouring QTL for meat quality traits; QTL for improved tenderness were associated with Limousin-derived and Jersey-derived alleles on these two chromosomes, respectively.

A QTL study of live animal and carcass traits in beef cattle was carried out in New Zealand and Australia. Back-cross calves (385 heifers and 398 steers) were generated, with Jersey and Limousin backgrounds. This paper reports on weights of eight organs (heart, liver, lungs, kidneys, spleen, gastro-intestinal tract, fat, and rumen contents) and 12 fat composition traits (fatty acid (FA) percentages, saturated and monounsaturated FA subtotals, and fat melting point). The New Zealand cattle were reared and finished on pasture, whilst Australian cattle were reared on grass and finished on grain for at least 180 days. For organ weights and fat composition traits, 10 and 12 significant QTL locations (P

beta, beta-carotene-9', 10'-dioxygenase (BCO2) plays a role in cleaving beta-carotene eccentrically, and may be involved in the control of adipose and milk colour in cattle. The bovine BCO2 gene was sequenced as a potential candidate gene for a beef fat colour QTL on chromosome (BTA) 15. A single nucleotide base change located in exon 3 causes the substitution of a stop codon (encoded by the A allele) for tryptophan(80) (encoded by the G allele) (c. 240G>A, p.Trp80stop, referred to herein as SNP W80X). Association analysis showed significant differences in subcutaneous fat colour and beta-carotene concentration amongst cattle with different BCO2 genotypes. Animals with the BCO2 AA genotype had more yellow beef fat and a higher beta-carotene concentration in adipose tissues than those with the GA or GG genotype. QTL mapping analysis with the BCO2 SNP W80X fitted as a fixed effect confirmed that this SNP is likely to represent the quantitative trait nucleotide (QTN) for the fat colour-related traits on BTA 15. Moreover, animals with the AA genotype had yellower milk colour and a higher concentration of beta-carotene in the milk.

This paper reports genetic parameters for ewe performance traits in sheep breeders' flocks in New Zealand. Animal performance records from the AgResearch Lamb Survival Database and from Sheep Improvement Limited were used to generate data sets from 3 lambing years (2003 to 2005) in 24 flocks, and involving 31,651 ewes and many breeds and breed compositions (predominantly Romney, Coopworth, and Texel). The heritabilities and repeatabilities for the litter survival traits were very low. Litter weight traits had heritabilities ranging from 0.12 for BW of lamb weaned to 0.28 for total triplet litter weight at birth and repeatabilities ranging from 0.18 to 0.29. The repeatabilities of BCS and maternal behavior score were low to moderate. This study showed that there is little to be gained from including litter survival in sheep selection programs because heritabilities and repeatabilities for the litter survival traits were very low. However, genetic gains in BCS, maternal behavior score, litter weight at birth, and litter weight weaned are possible in this population. Incorporating these traits into sheep selection programs warrants investigation to improve ewe and therefore flock performance.

This study investigated the effects of a SNP in the myostatin gene (MSTN or growth differentiation factor 8, GDF8) on birth, growth, carcass, and beef quality traits in Australia (Aust.) and New Zealand (NZ). The SNP is a cytosine to adenine transversion in exon 1, causing an amino acid substitution of leucine for phenylalanine 94 (F94L). The experiment used crosses between the Jersey and Limousin breeds, with the design being a backcross using first-cross bulls of Jersey x Limousin or Limousin x Jersey breeding, mated to Jersey and Limousin cows. Progeny were genotyped for the myostatin SNP and phenotyped in Aust., with finishing on feedlot (366 calves, over 3 birth years) and in NZ with finishing on pasture (416 calves, over 2 birth years). The effect of the F94L allele (A allele) on birth and growth traits was not significant. The F94L allele in Limousin backcross calves was associated with an increase in meat weight (7.3 and 5.9% of the trait mean in Aust. and NZ, respectively, P < 0.001), and a reduction in fat depth (-13.9 and -18.7% of the trait means on live calves (600 d) and carcasses, respectively, Aust. only, P < 0.001), intramuscular fat content (-8.2% of the trait mean in Aust., P < 0.05; -7.1% in NZ, not significant), total carcass fat weight (-16.5 and -8.1% of the trait mean, Aust. and NZ; P < 0.001 and P < 0.05, respectively). Meat tenderness, pH, and cooking loss of the M. longissimus dorsi were not affected by the F94L variant. In the Jersey backcross calves, additive and dominance effects were confounded because the F94L allele was not segregating in the Jersey dams. The combined effects, however, were significant on LM area (4.4% in both Aust., P < 0.05, and NZ, P < 0.01), channel fat (-11.7%, NZ only, P < 0.01), rib fat depth (-11.2%, NZ only, P < 0.05), and carcass fat weight (-7.1%, NZ only, P < 0.05). The results provide strong evidence that this myostatin F94L variant provides an intermediate and more useful phenotype than the more severe double-muscling phenotype caused by knockout mutations in the myostatin gene.

In this study, a highly significant quantitative trait locus (QTL) for meat percentage, eye muscle area (EMA) and silverside percentage was found on cattle chromosome 2 at 0-15 cM, a region containing the positional candidate gene growth differentiation factor 8 (GDF8), which has the common alias myostatin (MSTN). Loss-of-function mutations in the MSTN gene are known to cause an extreme 'double muscling' phenotype in cattle. In this study, highly significant associations of MSTN with cattle carcass traits were found using maternally inherited MSTN haplotypes from outbred Limousin and Jersey cattle in a linkage disequilibrium analysis. A previously reported transversion in MSTN (AF320998.1:g.433C>A), resulting in the amino acid substitution of phenylalanine by leucine at position 94 of the protein sequence (F94L), was the only polymorphism consistently related to increased muscling. Overall, the size of the g.433C>A additive effect on carcass traits was moderately large, with the g.433A allele found to be associated with a 5.5% increase in silverside percentage and EMA and a 2.3% increase in total meat percentage relative to the g.433C allele. The phenotypic effects of the g.433A allele were partially recessive. This study provides strong evidence that a MSTN genotype can produce an intermediate, non-double muscling phenotype, which should be of significant value for beef cattle producers.

A selection experiment to change reproductive traits in Angus cattle was established in New Zealand in 1984/85. Alongside an unselected control line, three lines were set up, selected for increased age at puberty in heifers (AGE+ line), reduced age at puberty in heifers (AGE‐ line), or increased scrotal circumference (SC line), with the last two lines being merged at the 1992 matings (forming a new AGE— line, with continued heifer puberty selection). The heritability of the direct response (age at puberty) through to 2004 was 0.27 ± 0.04. The purpose of the present study was to investigate correlated responses in carcass composition and growth traits, in response to pubertal selection. Traits measured included weaning, yearling, and breeding‐cow weights, carcass weight, dressing percentage, the weights of pericardial, omental and kidney fats, and the percentages of meat, bone, and trimmed fat. The carcass study included selection‐line and control animals (n = 185; calf crops born in 1997–2002), a...

Milk samples from New Zealand dairy cows at pasture were analysed to investigate the relationship between β‐casein genotype and milk yield or composition traits. A total of 1661 milk samples from 21 North Island herds were analysed from individual cows in mid lactation, from a routine herd‐test taken between mid November 2000 and early February 2001. The cows, whose ages ranged from 2 to 11 years, were the daughters of 11 widely used Holstein‐Friesian bulls. The β‐casein genotypes of the sires (A1 or A2 alleles)were: A1A1 (n = 1), A1A2 (n = 7) and A2A2 (n = 3). The milk composition traits analysed were: protein%, fat%, somatic cell count (SCC), β‐casein%, κ‐casein%, β‐lactoglobulin%, lactoferrin%, and fatty acid composition (C4‐C24, including conjugated linoleic acid). Milk yield per day, fat colour (optical density measurement), milk‐fat melting point, and an index of milk value in dollars (combining the industry's economic values for milk yield, fat yield, and protein yield) were also analysed....

Micromolar calcium activated neutral protease (CAPN1) was evaluated as a candidate gene for a quantitative trait locus (QTL) on BTA29 affecting meat tenderness by characterization of nucleotide sequence variation in the gene. Single-nucleotide polymorphisms (SNP) were identified by sequencing all 22 exons and 19 of the 21 introns in two sires (Piedmontese x Angus located at the U.S. Meat Animal Research Center in Clay Center, NE; Jersey x Limousin located at AgResearch in New Zealand) of independent resource populations previously shown to be segregating meat tenderness QTL on BTA29. The majority of the 38 SNP were found in introns or were synonymous substitutions in the coding regions, with two exceptions. Exons 14 and 9 contained SNP that were predicted to alter the protein sequence by the substitution of isoleucine for valine in Domain III of the protein, and alanine for glycine in Domain II of the protein. The resource populations were genotyped for these two SNP in addition to six intronic polymorphisms and two silent substitutions. Analysis of genotypes and shear force values in both populations revealed a difference between paternal CAPN1 alleles in which the allele encoding isoleucine at position 530 and glycine at position 316 associated with decreased meat tenderness (increased shear force values) relative to the allele encoding valine at position 530 and alanine at position 316 (P < 0.05). The association of maternal alleles with meat tenderness phenotypes is consistent with the hypothesis of CAPN1 as the gene underlying the QTL effect in two independent resource populations and presents the possibility of using these markers for selective breeding to reduce the numbers of animals with unfavorable meat tenderness traits.

A study was carried out on New Zealand dairy cows at pasture, to test for evidence of genetic differences in immunological response to nematode parasites. Nine widely used Holstein‐Friesian artificial insemination bulls, with daughters in many herds, were evaluated for nematode antibodies by sampling milk of their daughters in mid lactation in each of 20 North Island herds. One milk sample was taken from each cow (ranging from 4 to 11 years of age), during a routine herd test in the period from mid November 2000 to early February 2001. Assays were undertaken subsequently on pooled samples of skim milk (0.2 ml per cow; up to 20 cows per sire x herd) to assess antibodies to both the infective third larval (L3) and adult parasitic stages of Cooperia oncophora and Ostertagia ostertagi. Sire effects were significant for all four antibody types (P < 0.001). For O. ostertagi L3, there was a 1.20‐fold range in the mean antibody levels of the sire groups; corresponding proportional ranges for the other th...

Carcass data from three large beef‐cattle breeding experiments in New Zealand were analysed. Regressions of saleable meat weight on carcass and liveweights were estimated as parameters for a modelling exercise where pasture was converted to carcass and liveweight, finishing cattle at different end points. The data were also used in order to estimate heritabilities for nine carcass traits and the relationships among them. Slaughter data were from 1962 cattle, sired by 199 different bulls from 13 sire breeds. Relationships were first estimated between hot carcass weight and either carcass components or pre‐slaughter weight, and then an “animal” model was used to estimate genetic parameters. On a log‐log basis, the overall regression of carcass weight on pre‐slaughter weight was 1.089±0.008. The corresponding log‐log regression of saleable meat weight on carcass weight was 1.002 ± 0.007, bone weight on carcass weight 0.779 ± 0.015, and trimmed fat weight on carcass weight 1.265 ± 0.041. The regressi...

Summary A quantitative trait locus (QTL) study of the concentrations of 14 trace and macro elements (minerals) in tissues of beef cattle was conducted in New Zealand. Back-cross calves with Jersey and Limousin ancestry (202 heifers and 211 steers) were generated using first-cross sires. This paper reports on testing for effects of QTL on the concentrations of minerals in liver, kidney and muscle in cattle at slaughter, following a growth phase during which rearing and finishing stages were on pasture. Fifteen QTL were identified (P

Genetic correlations were estimated between pubertal traits of males or females and yearling or lifetime pregnancy rate (PR) in beef cows, using 269 paternal half-sib groups. Lifetime PR was recorded from up to 5 mating/calving years for each cow. The genetic correlations between age at first oestrus (AFO) or standardised age at first oestrus (SFO) and yearling PR were −0.30 ± 0.26 and −0.67 ± 0.44, whilst corresponding estimates with lifetime PR were −0.29 ± 0.26 and −0.76 ± 0.68. For scrotal circumference (SC), genetic correlation estimates with yearling PR were 0.53 ± 0.66 and with lifetime PR 0.34 ± 0.40. The data generally supported the concept of a favourable genetic correlation between pubertal traits (higher SC or lower AFO and SFO) and lifetime PR.

A total of 3768 calves and 4950 cow mating-years were involved in a study of heterosis retention. Crosses included first and subsequent inter-crosses between Angus and Hereford breeds as far as the fifth calf generation (F1, F2,…F5), back crosses (B1) using both F1 sires and F1 dams, and rotation crosses as far as the fifth calf generation (R2, R3, R4 and R5). Records collected were calf traits to the yearling stage, cow reproduction and maternal traits, and steer carcass data. Effects were estimated for 27 breed types for calves and 23 for cows. Breed type effects were then replaced by multiple regression coefficients for genetic effects including: an average individual (Angus) breed effect (gI), average maternal (gM) and average grandmaternal (gMG) breed effects, individual (dI), maternal (dM) and paternal (dP) dominance effects, and epistatic effects. From these, individual (hI) and maternal (hM) heterosis and other parameters were derived. For the Angus breed, gI was generally negative and gM positive for direct calf weights and cow weight; gI was positive for calf weaning weight (WW) as a maternal trait. The Angus breed was superior to the Hereford for net reproduction, productivity (weight of calf weaned per cow mated) and an efficiency ratio (productivity/average cow weight). Relative to the average of the purebreds, the superiorities of F1, F3 to F5, and R4 animals were respectively 2.1, 3.2 and 5.0% for birth weight, 6.5, 3.7 and 7.9% for yearling weight, 6.7, −2.2 and 3.4% for cow weight, 10.3, 0.7 and 11.7% for calf WW as a maternal trait, 7.4, −1.3 and 5.7% for number of calves weaned per cow mated, 19.4, 1.0 and 18.4% for productivity, and 11.2, 2.1 and 14.0% for the efficiency ratio. For calf traits and cow weight, dM and hI were generally significant and positive (except negative for calving date), whilst only hI was generally significant for calf weights as maternal traits. For the reproductive traits, the trends were for hI to be positive, but standard errors were large. For carcass traits, the interbreds and rotation crosses were generally like the heavier, fatter (i.e. Hereford) purebred. Overall, for productivity and the efficiency ratio, the rotation crosses (especially R4) were superior to the purebreds but generally not to the Fls, whilst the interbreds were similar to the purebred average.

A total of 1088 females of 14 breed groups (Angus and Hereford purebreds, and 12 first-cross groups) were evaluated over two locations for lifetime survival, numbers of calvings, numbers of calves weaned and cow lifetime records of calf survival. These traits are known to be related to a cow's lifetime productivity. The animals were part of the Ruakura Beef Breed Evaluation, designed to compare the growth and carcasses of steers, and the reproductive and maternal performance of females of different breed groups. Data were from 4 birth years of females and 11 breed-groups at location 1, and from 5 and 10 respectively at location 2, with seven breed-groups common to both locations. Females were first mated as yearlings. Culling at ages 2·5 to 4·5 years was based mainly on females that were non-pregnant on two occasions, whereas in subsequent years any non-pregnant female was culled. At location 1, there was a maximum possible number of mating years of 22 for females in the 1st birth year, declining to a maximum of 9 for those in the 4th birth year; for each age group at location 2 there was a maximum of 9 mating years. The average cow survival (number of mating years) was 7·26 (s.d. 3·02) at location 1 and 5·81 (s.d. 2·31) at location 2, with a coefficient of variation similar at both locations and averaging 0·41. The performances from the poorest to the best breed groups had a 1·5-fold range for number of mating years and a 1·8-fold range for number of calvings and number of calves weaned. The heritability of number of mating years (no. = 150 sire groups) was 0·13 (s.e. 0·08), number ofcalvings 0·11 (s.e. 0·08), number of calves weaned 0·15 (s.e. 0·08), and calf survival as a cow trait 0·027 (s.e. 0·018). This last heritability increased to 0·093 if adjustment was made to the underlying liability scale. There was no significant effect of breed of cow on number of mating years, nor on number of calves weaned per 100 calvings at either location, whilst the effect was significant for number ofcalvings and for number of calves weaned per cow (P < 0·10). The wide breed variation pointed to opportunities for selection among breeds, whilst the low heritabilities suggested that within-breed selection will be slow unless early indicator traits can be found.

Angus (A) and Hereford (H) cows at one location and A cows at a second location were used to generate purebred controls and six first-cross (F1) types of calf. Foundation sires were A, H, Friesian (F), Jersey (J), and South Devon (Sd) at Location 1, generating FH, FA, JA, SdA, and HA (plus AH) Fl calves, and at Location 2 sires were A and Blonde d'Aquitaine (Ba), generating BaA F1s. Sire breeds were selected as potentially contributing to productive crossbred cows, based on previous F1 cow comparisons. In subsequent years F2, F3, and F4 calves were produced from each of the two-breed crosses, with overlapping generations and contemporary controls providing balanced comparisons of breed types and generations. The experiment consisted of 395 unique sires and 5243 calves born in 1973–88 at Location 1 and 105 different sires and 2404 calves born in 1976–86 at Location 2. Growth, reproduction, maternal, and carcass traits were studied. Heterosis was estimated from HA (plus AH) and purebred A and H ani...

Angus cows at two locations were used to generate purebred controls and three three-breed crosses, as a result of inter-mating two-breed (halfbred Angus) crosses. The three-breed crosses were: 25% Simmental, 25% Friesian, 50% Angus (SiFA) from reciprocal matings between SiA and FA crosses; 25% Maine Anjou, 25% Jersey, 50% Angus (MaJA) from reciprocal matings between MaA and JA crosses; and 25% Blonded' Aquitaine, 25% Jersey, 50% Angus (BaJA) both from matings between JA bulls and BaA cows, and from matings between BaJ bulls and A cows. Breed crosses for this experiment were selected as potentially contributing to productive crossbred cows, based on the early years of two-breed cross data. After producing the first generation (F1) of three-breed crosses, each cross was subsequently interbred to produce F2 and F3 calves (202 sire groups overall). There were overlapping generations and contemporary controls, to compare crosses for growth, reproduction, maternal and carcass traits. The three three-br...

A total of 161 bulls from 11 breeds were used to generate crossbred calves from Angus cows in 1973 to 1977 at each of three diverse New Zealand locations, and from Hereford cows at one of the locations in the same years. The bulls comprised four local breeds, Angus, Friesian, Hereford, and Jersey, and seven recently imported breeds, Blonde d'Aquitaine, Charolais, Chianina, Limousin, Maine Anjou, Simmental and South Devon. This paper reports the reproductive and maternal performance of the straightbred and first-cross cows over the first four calvings, with first mating as yearlings at 14 to 16 months of age. A total of 7575 mating records from 2109 cows were analysed. Location differences were greater for reproduction than for growth traits and resulted in genotype × environment interactions for some components of cow performance and particularly the composite traits, weight of calf weaned per cow joined (productivity) and cow ‘efficiency’ (the ratio of productivity to cow weight). At all locations the Friesian-cross cows weaned the greatest weight of calf per head but were matched or surpassed by the lighter Jersey crosses in terms of efficiency of calf production. Most of the European crosses performed relatively much better in the most favourable environment than in the harsh environment and this was particularly marked for the productivity of Simmental crosses. Heterosis as a proportion of the purebred mean was important for cow performance and particularly pregnancy rate (0·12), productivity (0·21) and the efficiency ratio (0·16). Heritabilities for weight and age at puberty were both 0·34 (s.e. 0·08). Repeatabilities and heritabilities for cow reproductive traits were low (0·0 to 0·10) but higher for calf weights up to weaning as a trait of the cow (0·09 to 0·38). In general, the large European breeds which excelled in growth and carcass production produced female progeny which reached puberty at greater ages, had lower reproductive performance (especially in less favourable environments) and larger mature size. Some breed utilization strategies to achieve trade-offs between these genetic antagonisms are discussed.

Data from a large Hereford bull breeding herd in South Canterbury, New Zealand, were analysed to estimate genetic parameters for liveweights and three reproductive traits. The records comprised yearling weight (YW) in both sexes, 18-month (final) weight (FW) on bulls, scrotal circumference (SC), and serving capacity of bulls recorded in two ways, first as the number of serves in a standard time (serving number, SN), and second as a grade (serving grade, SG). There were 8 years of data available (1982–89 calf crops), comprising 2414 YW records from both sexes (progeny of 63 sires) and 1090 and 923 SC and SN records respectively. Restricted maximum likelihood (REML) procedures were applied to each trait, with a numerator-relationship matrix to incorporate pedigrees of paternal grand-sires. Univariate heritability estimates were 0.17 ± 0.06 (YW), 0.21 ± 0.09 (FW), 0.36 ± 0.13 (SC), 0.15 ± 0.07 (SN), and 0.14 ± 0.07 (SG). Phenotypic and genetic correlations were about 0.5 between liveweights (YW or F...

Records from a crossbreeding experiment were analysed to estimate the genetic correlation between scrotal circumference in bulls and pubertal traits in heifers, using paternal half-sib relationships. There were 234 sire groups in common. Bull and heifer calves were selected at random at weaning to comprise about five and six potential replacements respectively per sire group. In total 1307 bulls (born in 1980–1985) were each recorded for scrotal circumference in May (8 months of age), August and October, and 1302 heifers (born in 1981–1985) were checked for puberty for a 7-month period (using chinball harnesses on bulls) from about the beginning of May until mid-December. The pubertal traits in heifers were age at first oestrus (AFO), standardised age at first oestrus (SFO) and weight at first oestrus (WFO). Live weights were recorded monthly on heifers and WFO was interpolated from these weights. The heritabilities and genetic correlations were estimated using restricted maximum likelihood. Heritabilities for scrotal circumference were 0.50 ± 0.11, 0.33 ± 0.10 and 0.29 ± 0.10 in May, August and October respectively (0.29 ± 0.07 for all ages combined), whilst those for AFO, SFO and WFO were 0.33 ± 0.12, 0.32 ± 0.10 and 0.40 ± 0.13, respectively. Genetic correlations between scrotal circumference and heifer puberty traits averaged −0.39 ± 0.22 for AFO, −0.19 ± 0.20 for SFO and −0.39 ± 0.20 for WFO.

A quantitative trait locus (QTL) study was carried out in two countries, recording live animal and carcass composition traits. Back-cross calves (385 heifers and 398 steers) were generated, with Jersey and Limousin breed backgrounds. The New Zealand cattle were reared on pasture to carcass weights averaging 229 kg, whilst the Australian cattle were reared on grass and finished on grain (for at least 180 days) to carcass weights averaging 335 kg. From 11 live animal traits and 31 carcass composition traits respectively, 5 and 22 QTL were detected in combined-sire analyses, which were significant (P < 0.05) on a genome-wise basis. Fourteen significant traits for carcass composition QTL were on chromosome 2 and these were traits associated with muscling and fatness. This chromosome carried a variant myostatin allele (F94L), segregating from the Limousin ancestry. Despite very different cattle management systems between the two countries, the two populations had a large number of QTL in common. Of the 18 traits which were common to both countries, and which had significant QTL at the genome-wise level, eight were significant in both countries.

A quantitative trait locus (QTL) was identified by linkage analysis on bovine Chromosome 19 that affects the fatty acid, myristic acid (C14:0), in subcutaneous adipose tissue of pasture-fed beef cattle (99% level: experiment-wise significance). The QTL was also shown to have significant effects on ten fatty acids in the milk fat of pasture-fed dairy cattle. A positional candidate gene for this QTL was identified as fatty acid synthase (FASN), which is a multifunctional enzyme with a central role in the metabolism of lipids. Five single nucleotide polymorphisms (SNPs) were identified in the bovine FASN gene, and animals were genotyped for FASN SNPs in three different cattle resource populations. Linkage and association mapping results using these SNPs were consistent with FASN being the gene underlying the QTL. SNP substitution effects for C14:0 percentage were found to have an effect in the opposite direction in adipose fat to that in milk fat. It is concluded that SNPs in the bovine FASN gene are associated with variation in the fatty acid composition of adipose fat and milk fat.

Single nucleotide polymorphisms (SNPs) in the calpain 1 (CAPN1) and calpastatin (CAST) genes were studied to determine their effects on meat tenderness in Bos taurus cattle. Strip loins (M. longissimus dorsi) were removed from cattle in four resource populations after slaughter (n = 1042), aged under controlled conditions until fixed times after rigor mortis, cooked and measured using a tenderometer. Animals were genotyped for the CAPN1 SNP c.947C>G (p.Ala316Gly; AF252504) and for the CAST SNP c.2959A>G (AF159246). Frequencies of CAPN1 C alleles ranged from 23% to 68%, and CAST A alleles from 84% to 99.5%. From all data combined, the CAPN1 CC genotype (compared with the GG genotype) was associated with a 20.1 +/- 1.7% reduced average shear force at intermediate stages of ageing (P < 0.001) and with a 9.5 +/- 1.3% reduction near ultimate tenderness (P < 0.001). The heterozygote was intermediate. For CAST, corresponding values for AA compared with AG genotypes were reductions of 8.6 +/- 2.0% and 5.1 +/- 1.6% respectively (both P < 0.001), but there were too few GG genotypes for comparison. There were small interactions between the CAPN1 and CAST genotypes. For the CAPN1 and CAST genotypes combined, the maximal genotype effect in average shear force was 25.7 +/- 5.5% (P < 0.001) at intermediate stages and 15.2 +/- 4.8% near ultimate tenderness (P < 0.01).

Background Single nucleotide polymorphisms (SNPs) are an abundant form of genetic variation in the genome of every species and are useful for gene mapping and association studies. Of particular interest are non-synonymous SNPs, which may alter protein function and phenotype. We therefore examined bovine expressed sequences for non-synonymous SNPs and validated and tested selected SNPs for their association with measured traits. Results Over 500,000 public bovine expressed sequence tagged (EST) sequences were used to search for coding SNPs (cSNPs). A total of 15,353 SNPs were detected in the transcribed sequences studied, of which 6,325 were predicted to be coding SNPs with the remaining 9,028 SNPs presumed to be in untranslated regions. Of the cSNPs detected, 2,868 were predicted to result in a change in the amino acid encoded. In order to determine the actual number of non-synonymous polymorphic SNPs we designed assays for 920 of the putative SNPs. These SNPs were then genotyped through a panel of cattle DNA pools using chip-based MALDI-TOF mass spectrometry. Of the SNPs tested, 29% were found to be polymorphic with a minor allele frequency >10%. A subset of the SNPs was genotyped through animal resources in order to look for association with age of puberty, facial eczema resistance or meat yield. Three SNPs were nominally associated with resistance to the disease facial eczema (P < 0.01). Conclusion We have identified 15,353 putative SNPs in or close to bovine genes and 2,868 of these SNPs were predicted to be non-synonymous. Approximately 29% of the non-synonymous SNPs were polymorphic and common with a minor allele frequency >10%. Of the SNPs detected in this study, 99% have not been previously reported. These novel SNPs will be useful for association studies or gene mapping.

The identification of genes that influence meat quality and meat yield has relevance for several livestock species. Candidate genes include those involved in the biochemical pathways controlling muscle differentiation, growth and development. Mutations in one such gene, myostatin, have previously been reported to have dramatic effects on muscle phenotype in cattle. Here we report a screening strategy for the discovery of novel mutations in 10 genes involved in muscle development using single-stand conformation polymorphism gels and DNA sequencing. Several novel mutations, both non-synonymous and synonymous were discovered, and some of these may alter gene function. In addition, we also conducted a meta-analysis of published quantitative trait loci from cattle, sheep, pigs and mice, identifying those muscle development genes most likely to contribute to variation in muscle traits within species. From this strategy we found several genes that map into regions that are part of the extended muscle development pathway.

An experiment was conducted under beef farming conditions to compare the reproductive performance of females originating from dairy herds or from a beef cattle herd. Hereford × Friesian (HF) and Angus × Jersey (AJ) females, bred in the dairy industry and born in the late winter/spring of 1978, 1979, and 1980 were transferred to a beef cattle herd in their first summer/autumn. They were farmed until their last calves were weaned in 1987 and they were compared with homebred FH and JA females born in the same years. The experiment comprised 213 females with an average of 4.0 mating records each, and included first mating at about 14 months of age. Heifers of dairy origin were older than their counterparts of beef origin, but were significantly heavier only in their first autumn and at first mating. The dairy heifers were lighter when compared at fixed ages (7 and 14 months). The weaning rates (numbers of calves weaned per 100 females" to the bull) from HF and FH crosses were 73.9 and 83.7 respective...

Genetic variation in host resistance to nematode infection was studied in two calf crops of Angus cattle under natural pasture challenge conditions in New Zealand, using faecal egg count (FEC) as a marker trait. Genetic and phenotypic correlations of FEC with anti-nematode antibody (Ab) level and live weights were also estimated. Ab to the third larval stages of Cooperia curticei (Cc), Cooperia oncophora (Co), Ostertagia ostertagi (Oo) and Trichostrongylus colubriformis (Tc) were assayed, along with Ab to the adult stages of Co and Oo. Calves were born in the late winter/early spring of 1995 and 1996 over a 7-week period each year; they were weaned at an average of 4 months of age, and faecal samples for FEC were taken at 10 months of age (1995 crop) and at 7 months of age (1996 crop). Blood samples for Ab were taken from both calf crops at intervals between 4 and 20 months of age, and later in peri-partum heifers and cows (23 to 25, and 36 to 37 months of age). For the two calf crops combined, there were 370 animals by 24 sires. Additional blood samples were taken on related animals from the 1993 and 1994 calf crops (218 extra animals, 19 different extra sires). The heritability of loge (FEC + 100) was 0•32 (s.e. 0•16), and heritabilities of loge Ab between 4 and 9 months of age averaged 0•30, between 11 and 20 months of age 0•22, and peri-partum 0•30. Between-animal repeatabilities of Ab levels from samples taken between 4 and 9 months of age averaged 0•40, between 11 and 20 months 0•48, and peri-partum 0•35. Genetic and phenotypic correlations among loge Abs for various nematode species (in hosts aged 4 to 9 months) averaged 0•82 and 0•61, respectively. The corresponding genetic and phenotypic correlations between loge Ab and loge(FEC + 100) averaged –0•48 and –0•07, respectively, whilst those between loge Ab and yearling weight averaged 0•29 and 0•13, respectively. It was concluded that direct selection to reduce FEC should be feasible if required, but index selection combining increased live weight and reduced FEC would often be preferable; anti-nematode Ab levels were repeatable, and FEC and Ab levels were negatively associated genetically.

A selection experiment to change reproductive traits in Angus cattle has been maintained for 14 years, with first calvings in 1985. Alongside an unselected control line, three lines were established, selected for increased age at puberty in heifers (AGE+ line), reduced age at puberty in heifers (AGE‐ line), or increased scrotal circumference (SC line). The last two lines were merged at the 1992 matings, with the revised objective of applying further selection in both sexes to reduce age at puberty in heifers. Dates at puberty in heifers from an average of 8 to 16 months of age and SC in bulls were recorded in all lines, along with the pregnancy rates (PR) and subsequent calving dates (CD) in heifers and all cow‐age groups. Heritabilities of single‐record SC, standardised age at first behavioural oestrus (SFO), and single‐record CD were 0.41 ± 0.04 (repeatability 0.70 ± 0.01), 0.27 ± 0.04, and 0.09 ± 0.04 (repeatability 0.19 ±0.03), respectively. Genetic correlations of SC with SFO and CD were ‐0....

A total of 528 calves from 3 calf crops, sired by 34 Friesian and 28 Jersey bulls, were challenged with sporidesmin, the toxin causing facial eczema (FE), in order to determine the genetic variation in susceptibility to FE. The challenge was either by grazing toxic pasture or by oral dosing, and the response was monitored by blood sampling to measure the elevations of serum gamma‐glutamyltransferase (GGT), glutamate dehydro‐genase (GDH), and other possible indicators (enzymes or metabolites: bilirubin, aspartate transaminase, ferroxidase, bile acids, and 5'nucleo‐tidase). The last calf crop was sired, in part, by bulls phenotypically selected from the second calf crop using GGT records. Data were analysed using the repeated records option of a restricted maximum likelihood programme. A sire model was used, with sires and maternal grandsires included to determine pedigree. The uni‐variate heritability estimates for logeGGT were 0.29 ± 0.15 in Friesians and 0.77 ± 0.13 in Jerseys, and for logeGDH t...

Two studies were carried out to measure variation in faecal nematode egg count (FEC) or serum anti‐nematode antibody (Ab) concentration in Friesian cattle, and correlations between these traits and subsequent milk yield traits. In Study 1, FEC and Abs were measured in 9‐month‐old calves and 21‐month‐old heifers (1996 and 1995 calf crops, respectively), and correlations with the subsequent first‐lactation yield traits were estimated in herds calving in late winter (July/August). In Study 2, Abs were measured in mixed‐age cows during lactation in each of four groups (summer, autumn, winter, and spring calving mobs), and correlations were estimated between Abs and yield in the current lactation. In Study 1, concentrations of the six different Abs (adult and/or third larval stages of four nematode parasite species) were moderately correlated with each other (average correlations of 0.57 in calves and 0.65 in heifers). In Study 2 the average correlation among Abs was 0.74. In Study 1, the average FEC ...