Polled Hereford Cattle Research Articles

Reconciling the Protean Manifestations of Arrhythmogenic Cardiomyopathy

Medical conception of a disease begins with in vivo observation and develops with recognition of cognate findings on gross anatomy, histology, and cellular pathology. It was histopathology that established myocyte disarray as the cardinal feature of hypertrophic cardiomyopathy, present even in cases where left ventricular (LV) hypertrophy is subtle or absent. To this day, clinical-pathological association retains its historical value as the primary means of gaining insight into underlying disease processes. Enhancing its appeal is its accessibility to physicians, most of whom are familiar with histopathology from medical school and attuned to visual diagnosis. Article see p 632 With the advent of molecular genetics, however, the limitations of clinical-pathological association have become apparent and nowhere more so than in the inherited arrhythmia syndromes. In the long-QT and Brugada syndromes and catecholaminergic polymorphic ventricular tachycardia, a structurally normal heart belies the propensity to ventricular arrhythmia and sudden cardiac death (SCD). How this might be possible began to unravel with the isolation of mutations in genes encoding ion channels, transporters, and binding proteins. Genetic studies also have provided fresh insights into diseases with an obvious pathological substrate, such as hypertrophic cardiomyopathy, in which sarcomeric mutations predominate. Families with a high incidence of SCD and myocyte disarray but minimal LV hypertrophy were found to have mutations in troponin T,1 lending further support to the inclusion of this phenotype within the spectrum of hypertrophic cardiomyopathy. Redefining diseases according to their genetic etiology, while attractive, is less straightforward than immediately obvious. Defects in sarcomeric components, for example, have been implicated in both hypertrophic cardiomyopathy and dilated cardiomyopathy. In some heritable disorders, such as dilated cardiomyopathy, marked locus heterogeneity precludes delineation of a single genetic determinant. The ultimate solution to disease classification involves going 1 step further and identifying a unifying molecular mechanism, which may …

A mutation in NFκB interacting protein 1 causes cardiomyopathy and woolly haircoat syndrome of Poll Hereford cattle

Cardiomyopathy and woolly haircoat syndrome (CWH) of Poll Hereford cattle is a lethal, autosomal recessive disorder. Cardiac and haircoat changes are congenital, neonatal ocular keratitis develops in some cases and death usually occurs within the first 12 weeks of life. We undertook a homozygosity mapping approach to identify the chromosomal location of the causative gene. Seven candidate genes were examined for homozygosity in affected animals: desmoplakin and junction plakoglobin (both previously implicated in human cardiocutaneous syndromes), desmocollin 2, desmoglein 2, plakophilin 2, nuclear factor kappa B (NFKB1) and NFkappaB interacting protein 1 (PPP1R13L, also known as NKIP1). Homozygosity in 13 affected animals was observed at the PPP1R13L locus, located on bovine chromosome 18. Subsequent sequence analysis revealed a 7-bp duplication (c.956_962dup7) in exon 6 of this 13-exon gene. This frameshift variant is predicted to result in the substitution of three amino acids and the introduction of a premature stop codon at position 325 of the protein product (p.Ser322GlnfsX4). PPP1R13L interacts with NFkappaB, a family of structurally related transcription factors that regulate genes controlling inflammation, immune responses and cell proliferation and survival. CWH represents a large-animal model for cardiocutaneous disorders caused by a mutation in the PPP1R13L gene. The identification of this bovine mutation also indicates that PPP1R13L and other genes affecting NFkappaB activity may be candidate genes in the study of human cardiovascular disease.

Estimates of heritabilities and genetic correlations in polled Hereford cattle selected for feed conversion (1999)

Performance records of 1459 Polled Hereford cattle were analyzed to estimate heritabilities and genetic correlations of beef cattle traits from birth to maturity. Estimates of heritability (h2) for birth weight (BWT), weaning weight (WWT), yearling weight (YWT), scrotal circumference (SC), yearling height (YHT), mature height (MHT), and mature weight (MWT) were moderate to high, with the exception of WWT (h2 = .14), and ranged from .38 to .72. The traits associated with feed conversion, daily feed intake (INT), average daily gain (ADG), and feed conversion (CONV) had heritabilities of .24, .25, and .14, respectively. Genetic correlations (rg) between the growth traits (BWT, WWT, YWT, YHT, MHT, MWT, and SC) were positive and ranged from .20 to .88. The rg=.99 between milk production (MILK) and maternal weaning weight (MWW) indicates that the traits are essentially the same and supports the method in which many breed associations calculate and report expected progeny differences (EPDs) for milk production. The rg = .42 between ADG and INT, rg = .27 between INT and CONV, and the rg = -.82 between ADG and CONV suggest that faster gaining cattle have greater feed intakes and are more efficient.

Selection response for feed conversion and growth traits in polled Hereford cattle (1999)

Direct and correlated responses to selection for improved feed conversion were estimated from performance records of 1459 Polled Hereford cattle born from the spring of 1967 through the spring of 1979. Data were analyzed using a multiple-trait, derivative-free, restricted maximum likelihood (MTDFREML) procedure. A full animal model was used to calculate genetic and phenotypic (co)variances. The withinherd breeding values that resulted from the solution of the mixed model equations were regressed on year to create selection response curves. Feed conversion was shown to respond favorably to direct selection, with feed/gain changing -.005 per year.

Genetic associations of growth and lactation curve components in polled Hereford cattle (1999)

Growth improvement is an emphasis of most breeding programs. Mathematical components of growth curves provide a means to evaluate various aspects of animal growth. Milk production has a major influence on calf weaning weights. The ability to predict milk production can be useful in improving calf weaning weight and matching cows to various environments. Total milk production per lactation can be predicted by inputting daily milk records into lactation curves. The purpose of this study was to estimate the heritabilities and genetic correlations of growth curve and lactation curve components.

Genetic parameters for cow weight and condition score in Angus, Hereford, and Poll Hereford cattle

Heritabilities and genetic correlations for cow weight and body condition score were estimated from field data for 3 beef breeds in Australia. In all, 8177 cows of mixed ages were weighed and scored for body condition at calf weaning time in seedstock herds as part of a large research project. The average weaning age was 212, 221, and 218 days for Angus, Hereford, and Poll Hereford, respectively. Cow weights and condition scores were analysed separately for each breed and estimates of genetic parameters were obtained by Restricted Maximum Likelihood (REML). Cow weight and condition score were moderately heritable: h2 = 0.43 and 0.21 for Angus, 0.39 and 0.14 for Hereford, and 0.48 and 0.17 for Poll Hereford. The genetic correlation between CW and CS was 0.49, 0.65, and 0.58 for Angus, Hereford, and Poll Hereford, respectively. There is potential for providing a genetic evaluation for cow weight using field data in Australian beef cattle. Its modelling for inclusion in a multiple trait genetic evaluation system such as BREEDPLAN is discussed.

Heterozygote detection for maple syrup urine disease in cattle.

The clinical, pathological and biochemical manifestations of maple syrup urine disease (MSUD) are similar in Poll Hereford and Poll Shorthorn x Poll Hereford calves. No significant differences were observed in branched-chain amino acid concentrations in plasma, or of branched-chain keto acid dehydrogenase activity in fibroblasts, between Poll Herefords homozygous normal and heterozygous for the mutation responsible for MSUD. Haemopoietic chimerism resulted in incorrect diagnosis of the MSUD genotype in 30% of non-identical twins when blood DNA was analysed using allele-specific amplification. Hair roots are shown to be a suitable source of target DNA for genotyping Poll Hereford cattle for the MSUD mutation. Twelve of 203 (5.8%) aged Poll Hereford bulls, sampled at saleyards during the last 4 months of 1993, were found to be heterozygous for the mutation. In contrast, the mutant sequence was detected in only 1 of 150 (0.7%) 2- and 3-year-old Poll Hereford bulls offered for sale at 2 stud sales held during 1993, suggesting that the prevalence of the disease may decline over the next few years.

Relationships between weaning weight, maternal weaning weight, and milk production in polled Hereford cattle (1995)

Performance data from a Polled Hereford herd selected for improved feed conversion were used to calculate a variety of genetic parameters. Heritabilities were .14 for weaning wt, .18 for maternal weaning wt., and .19 for milk production. The genetic correlations were -.10 between weaning weight and maternal weaning weight and 0 between weaning weight and milk production. However, the genetic correlation between maternal weaning weight and milk was . 99, indicating they are essentially the same trait. Milk EPDs published by most breed associations are calculate d as the maternal weaning weight. Our study strongly supports this method of estimating an animal's genotype for milk production.

Selection response and genetic parameter estimation for feed intake, gain, and feed conversion (1995)

Performance records of 1459 Polled Hereford cattle born from 1967 through 1979 were analyzed to estimate genetic parameters and the direct and correlated responses that were due to selection for feed conversion. Heritabilities were .24 for intake, .25 for gain, and .14 for feed conversion. The genetic correlation between average daily gain and feed conversion was -.82; correlation between average daily gain and feed intake was .42. Faster-gaining cattle have greater feed intakes and are more efficient. Feed conversion was improved by direct selection. However, it is more economically feasible for breeders to improve feed conversion by selecting for faster rates of gain, rather than selecting for the trait directly.

Heritabilities and genetic correlations for birth weight, weaning weight, and yearling weight in polled Hereford cattle

Performance data from a Polled Hereford herd selected for feed conversion were used in the calculation of heritabilities and genetic correlations for birth weight (BWT), weaning weight (WWT), and yearling weight (YWT). Direct heritabilities for BWT, WWT, and YWT were .31, .16, and .25, respectively. Corresponding maternal heritabilities for BWT, WWT and YWT were .04, .01, and .18, respectively. With the exception of the correlation between WWT and YWT (.98), the other genetic correlations were low to moderate, ranging from -.27 to .12.

Heritabilities and genetic correlations for birth weight, weaning weight, and yearling weight in polled Hereford cattle (1994)

Performance data from a Polled Hereford herd selected for feed conversion were used in the calculation of heritabilities and genetic correlations for birth weight (BWT), weaning weight (WWT), and yearling weight (YWT). Direct heritabilities for BWT, WWT, and YWT were .31, .16, and .25, respectively. Corresponding maternal heritabilities for BWT, WWT and YWT were .04, .01, and .18, respectively. With the exception of the correlation between WWT and YWT (.98), the other genetic correlations were low to moderate, ranging from -.27 to .12.

Covariance matrices for growth traits of Australian Polled Hereford cattle

AbstractEstimates of covariance components due to direct and maternal effects among birth, weaning, yearling and final weight for Australian Polled Herefords were obtained by restricted maximum likelihood fitting an animal model. Data were obtained from commercial herds participating in the National Beef Recording Scheme and an across-herd genetic evaluation service. Analyses were carried out considering nine subsets of data, each comprising at least 3000 weaning, 1000 yearling and 500 final weight records which yielded a total of 30 506,17 105 and 9486 records for the three weights, respectively. Estimates of variances and genetic parameters varied considerably between data sets. Both genetic and permanent environmental effects were found to affect all traits except final weights significantly, with maternal environmental effects explaining proportionately more than 0·20 of the total variation in weaning weight. Estimates of the direct-maternal genetic correlation were consistently negative and moderate to strong, ranging from -0·34 to -0·82 for weaning weight. Maternal correlations between weaning and yearling weights were close to unity. Estimates of the direct genetic correlations among the three later weights were 0·8 or larger. Problems with this kind of analysis are discussed.

Genetic and environmental parameters for mature weight and other growth measures in Polled Hereford cattle.

Variances and covariances were estimated for birth weight (BWT), weaning weight (WW), yearling gain (YG), yearling weight (YW), yearling height (YH), relative growth from birth to weaning (RGW) and weaning to yearling (RGY), and mature weight (MW). Field records on 572,446 Polled Hereford cattle were analyzed. Because multiple dam weights were collected on a cow the MW used in the analysis was calculated using a nonlinear regression correction factor computed by fitting a quadratic with a plateau to the data. If the cow had an observation(s) beyond the inflection point (IP), the closest weight to that point was used. If the cow only had observation(s) before the IP the closest weight to that point was nonlinearly adjusted to the plateau. The IP for this data set was 1,506 d and the plateau was 554.7 kg. Heritabilities and genetic and environmental correlations were calculated from the appropriate (co)variances and phenotypic correlations were computed. Heritability estimates for BWT, WW, YG, YW, YH, RGW, RGY, and MW were .49, .24, .23, .30, .59, .24, .15, and .52, respectively. Genetic correlations between MW with BWT, WW, YG, YW, YH, RGW, and RGY were .64, .80, .76, .89, .73, -.29, and .35, respectively, environmental correlations were .15, .43, .05, .40, 1.03, .32, and -.10, respectively, and phenotypic correlations were .33, .32, .28, .46, .70, .00, and .07, respectively.

Epidemiologic findings in congenital anemia, dyserythropoiesis, and dyskeratosis in polled Hereford calves.

Congenital dyserythropoiesis and dyskeratosis occur within certain lines of Polled Hereford cattle. Eighty-nine of 90 alleles in 45 affected calves had a mechanism in which they could be identical by descent from an identified common ancestor. The line allele may have been a recurrence of the mutation, or the mutation may have occurred earlier in the breed's history and been distributed throughout the breed by the extensive use of several ancestors. No evidence of disease has been identified in sire and dams of affected calves, suggesting that the allele is not acting in a dominant or incompletely dominant manner. Even distribution of cases between sexes suggests that the disease is not sex linked or sex influenced. A higher degree of inbreeding in the affected calves and temporal and spatial features that separated individual cases also suggest a genetic cause. Segregation ratios were not significantly different from those of the hypothesized simple autosomal recessive inheritance.

Live animal measurement of carcass traits: estimation of genetic parameters for beef cattle

Ultrasound measurements by trained and accredited sonographers on 9,232 Angus, Hereford, and Polled Hereford cattle at an average age of 450 d were used to estimate genetic and environmental (co)variances for weight at scanning (Wt), longissimus muscle area (LMA), longissimus muscle area adjusted to a constant weight of 400 kg (LMAawt), and fat depths at the rump and 12/13 rib sites. Estimated kilograms (ESMkg) and percentage of saleable meat yield (ESM%) were also calculated and analyzed. Subjective muscle scores, available for 2,488 animals, were also included in the analysis. Estimated heritabilities were 46% for Wt, 21% for LMA and LMAawt, 37% for rump fat, 30% for rib fat, 15% for muscle score, 44% for ESMkg, and 36% for ESM%. The two measurements, LMA and LMAawt, had high genetic (.82) and environmental (.91) correlations. The two fat depths were also highly correlated (.86 genetic; .67 environmental). Weight at scanning was moderately correlated with LMA (.45 genetic; .41 environmental). Differences between breeds could not be detected, but some variation in parameter estimates between data sets of the same breed was observed. Environmental correlations between fat depths or muscle score and Wt were approximately .3; genetic correlations were .07 to .12. Subjective muscle score had marginally higher genetic correlations with LMA than with LMAawt (.22 vs .08) but similar environmental correlations (.31 vs .27). Results show that carcass traits measured by ultrasound and predictions of meat yield have genetic variability, are moderately heritable, and that genetic progress based on genetic evaluation by mixed-model analysis can be made.

Increased γ‐Aminobutyric Acid Receptor Function in the Cerebral Cortex of Myoclonic Calves with an Hereditary Deficit in Glycine/Strychnine Receptors

Inherited congenital myoclonus (ICM) of Poll Hereford cattle is a neurological disease in which there are severe alterations in spinal cord glycine-mediated neurotransmission. There is a specific and marked decrease, or defect, in glycine receptors and a significant increase in neuronal (synaptosomal) glycine uptake. Here we have examined the characteristics of the cerebral gamma-aminobutyric acid (GABA) receptor complex, and demonstrate that the malfunction of the spinal cord inhibitory system is accompanied by a change in the major inhibitory system in the cerebral cortex. In synaptic membrane preparations from ICM calves, both high-and low-affinity binding sites for the GABA agonist [3H]muscimol were found (KD = 9.3 +/- 1.5 and 227 +/- 41 nM, respectively), whereas only the high-affinity site was detectable in controls (KD = 14.0 +/- 3.1 nM). The density and affinity of benzodiazepine agonist binding sites labelled by [3H]diazepam were unchanged, but there was an increase in GABA-stimulated benzodiazepine binding. The affinity for t-[3H]butylbicyclo-o-benzoate, a ligand that binds to the GABA-activated chloride channel, was significantly increased in ICM brain membranes (KD = 148 +/- 14 nM) compared with controls (KD = 245 +/- 33 nM). Muscimol-stimulated 36Cl- uptake was 12% greater in microsacs prepared from ICM calf cerebral cortex, and the uptake was more sensitive to block by the GABA antagonist picrotoxin. The results show that the characteristics of the GABA receptor complex in ICM calf cortex differ from those in cortex from unaffected calves, a difference that is particularly apparent for the low-affinity, physiologically relevant GABA receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of the branched-chain α-ketoacid dehydrogenase and elucidation of a molecular basis for maple syrup urine disease

The hepatic branched-chain α-ketoacid dehydrogenase complex plays an important role in regulating branched-chain amino acid levels. These compounds are essential for protein synthesis but toxic if present in excess. When dietary protein is deficient, the hepatic enzyme is converted to the inactive, phosphorylated state to conserve branched-chain amino acids for protein synthesis. When dietary protein is excessive, the enzyme is in the active, dephosphorylated state to commit the excess branched-chain amino acids to degradation. Inhibition of protein synthesis by cycloheximide, even when the animal is starving for dietary protein, results in activation of the hepatic branched-chain α-ketoacid dehydrogenase complex to prevent accumulation of branched-chain amino acids. Likewise, the increase in branched-chain amino acids caused by body wasting during starvation and uncontrolled diabetes is blunted by activation of the hepatic branched-chain α-ketoacid dehydrogenase complex. The activity state of the complex is regulated in the short term by the concentration of branched-chain α-ketoacids (inhibitors of branched-chain α-ketoacid dehydrogenase kinase) and in the long term by alteration in total branched-chain α-ketoacid dehydrogenase kinase activity. cDNAs have been cloned and the primary structure of the mature proteins deduced for the E1α subunit of the human and rat liver branched-chain α-ketoacid dehydrogenase complex. The cDNA and protein sequences are highly conserved for the two species. Considerable sequence similarity is also apparent between the E1α subunits of the human branched-chain α-ketoacid dehydrogenase complex and the pyruvate dehydrogenase complex. Maple syrup urine disease is caused by an inherited deficiency in the branched-chain α-ketoacid dehydrogenase complex. The molecular basis of one maple syrup urine disease family has been determined for the first time. The patient was found to be a compound heterozygote, inheriting an allele encoding an abnormal E1α from the father, and an allele which is not expressed from the mother. The only known animal model for the disease (Polled Hereford cattle) has also been characterized. The mutation in these animals introduces a stop codon in the leader peptide of the E1α subunit, resulting in premature termination of translation. Two thiamine responsive patients have been studied. The deduced amino acid sequences of the mature E1α subunit and its leader sequence were normal, suggesting that the defect in these patients must exist in some other subunit of the complex. 3-Hydroxyisobutyrate dehydrogenase and methylmalonate-semialdehyde dehydrogenase, two enzymes of the valine catabolic pathway, were purified from liver tissue and characterized. The cDNA encoding the former enzyme was cloned. Isolation of the latter enzyme establishes that methylmalonate semialdehyde can be converted directly to propionyl-CoA and the nature of previously uncertain steps in the pathway of valine catabolism in animal tissues.

Cardiomyopathy and woolly haircoat syndrome of Poll Hereford cattle: electrocardiographic findings in affected and unaffected calves.

Electrocardiograms were recorded from 4 calves with cardiomyopathy and woolly haircoat syndrome (CWH), a lethal autosomal recessive trait of Poll Hereford cattle and from 9 unaffected calves. Electrocardiograms of calves with CWH were characterised by multifocal ventricular premature contractions which occurred singly, in pairs, in runs and as episodes of ventricular tachycardia. Bigeminal rhythms were recorded occasionally. The frequency of ventricular premature contractions ranged from 5 to 120.min-1. Ventricular premature contractions in calves with CWH were attributed to myocardial degeneration and fibrosis which were observed grossly and microscopically. Electrocardiograms in unaffected calves were characterised by normal sinus rhythm and by variation in the morphology of wave forms between animals. The durations of the various wave forms were less than those previously recorded from adult cattle.

Evaluation of performance characteristics in a diallel among Simmental, Limousin, Polled Hereford and Brahman beef cattle. I. Growth, hip height and pelvic size.

Progeny of a diallel among Simmental, Limousin, Polled Hereford and Brahman breeds of cattle were evaluated over 5 yr for preweaning and postweaning growth, hip height and pelvic size. Calves from Brahman and Simmental dams had the highest preweaning gains and weaning weights, and those from Polled Hereford dams had the lowest (P less than .05). Differences in the availability of milk and postpartum compensatory gains in progeny of Brahman dams could have contributed to these results. However, calves from Simmental, Limousin and Polled Hereford dams had significantly greater feedlot daily gains than those from Brahman dams. Yearling hip height and pelvic area were lower for progeny of Polled Hereford dams, whereas calves from Simmental, Limousin and Brahman dams were not different for these traits. A series of linear comparisons among these four breeds using least-squares means to estimate general and specific combining ability and maternal effects found significant, negative maternal effects for Polled Hereford for preweaning gain and weaning weight. A positive maternal effect (P less than .05) for Limousin was found for feedlot gain. General combining ability and maternal estimates were significant and variable in most comparisons for yearling hip height and pelvic area. Heterosis estimates were positive and significant in all crosses with Brahman for preweaning gain, weaning weight, yearling weight, hip height and pelvic area. Significant, positive heterosis was also found in Polled Hereford crosses with Limousin and Simmental for preweaning gain, weaning weight and yearling weight.

Evaluation of performance characteristics in a diallel among Simmental, Limousin, Polled Hereford and Brahman beef cattle. II. Carcass traits.

Evaluations of steer and heifer progeny from a diallel mating design of Simmental, Limousin, Polled Hereford and Brahman beef cattle over 5 yr are presented. Traits evaluated included final weight, hot carcass weight, ribeye area, 12th rib fat thickness, marbling score, yield grade, dressing percentage and percentage of kidney, pelvic and heart fat. Progeny of Simmental sires were heavier at slaughter than those with Brahman sires (P less than .05), but no differences were found for carcass weight. Dressing percentage was higher for Limousin crosses compared with progeny of other sire breeds (P less than .05). Similar results were found for dam breeds, except that progeny of Limousin dams had heavier carcasses with a higher dressing percentage (P less than .05) than Brahman crosses. Crosses of Limousin and Simmental had larger ribeye areas (P less than .05) compared with calves of the other breeds. Progeny of Polled Hereford dams had higher marbling scores and were fatter than progeny of dams of other breeds (P less than .05). Heterosis estimates were significant for all Brahman crosses for final weight, carcass weight and ribeye area, but these contrasts were negligible for other traits. Estimates of general combining ability were positive and significant for Simmental for final weight, carcass weight, ribeye area and marbling score and were significant and negative for Limousin for final weight, fat thickness and yield grade. Maternal values were generally small.