Controlling ocular squamous cell carcinoma in Hereford cattle

In 3 herds 737 Hereford cattle were examined for neoplastic ocular lesions at intervals ranging from 20 to 242 days. Initially all lesions greater than 3 mm diameter were treated by cryosurgery; smaller lesions were left untreated. At subsequent inspections, lesions which had increased to 5 mm diameter were treated. The prevalence of ocular lesions in the herds ranged from 8.1 to 45.7% at the commencement of the study, and from 1.5 to 8.8% after 3.5 years. In treated cattle 71% of lesions regressed after one or two treatments. Seventy-five percent of the small untreated lesions regressed. The progression of lesions and occurrence of new lesions was highest during summer and lowest during winter. It was concluded that inspection of eyes for lesions should be at intervals of 3 to 4 months, and include one during the summer. It is feasible for owners to detect and identify cattle with ocular lesions and to present for treatment those that have grown since the preceding inspection to a size nearing or exceeding 5 mm diameter.     

Hereditary lymphedema in Hereford cattle

Congenital lymphedema is described in Hereford cattle. The disease was characterized by edema of the hind limbs, sometimes forelimbs, tail, and prepuce. Lymphatic system lesions were hypoplasia and aplasia of lymph vessels and prescapular, iliofemoral, and popliteal lymph nodes. Test matings demonstrated the transmission of the disease by an autosomal dominant trait with variable expressivity and incomplete penetrance.     

Genetic analyses of nematode egg counts in Hereford and crossbred Hereford cattle in the subtropics of New South Wales

A total of 438 calves was produced by 123 sires of Hereford, Simmental, Friesian and Brahman breeds when mated to Hereford cows. Faecal egg counts and larval differentiation of nematode species were undertaken on one or two occasions prior to weaning at 7 to 8 months. Significant breed of sire and sire within breed effects were observed, but heritabilities, repeatabilities and phenotypic correlations were generally low to moderate.     

A prototype national cattle evaluation for sustained reproductive success in Hereford cattle

The objective of this research was to develop a prototype system for national cattle evaluation that would facilitate selection for improved fertility of daughters from Hereford sires. Raw data for this analysis were the birth dates of calves as reported by breeders to the American Hereford Association. Records from females entered this analysis with the reporting of a birth date for their first calf. At that time, females were required to be in contemporary groups of at least 3 animals and to have at least 2 additional paternal half-sibs also represented in the data. To explicitly define "sustained reproductive success," the philosophy taken was that a female that maintained a calving interval of 425 d or less would be considered successful. Females failing to meet this criterion were considered to be at the end of their successful lifetime. Data were analyzed using methodology for survival analysis with grouped data. Fixed contemporary groups were modeled as being time dependent, reflecting the females exposed for breeding in the same herd-year-season. Sire effects were time independent and considered random. Also included in the analysis were time-independent covariates for maternal weaning weight and total maternal calving ease from the national cattle evaluation of the American Hereford Association. Records from females still successfully in production at the time of this analysis, those that were transferred, those with calving intervals less than 280 d, and those that were successful until becoming donor dams for embryo transfer were considered censored. A total of 36,866 females contributed to this analysis, with 14,143 of these having censored records. The median number of females in a contemporary group was 6. A total of 3,323 sires had daughters with records. The median number of daughters per sire was 7. Heritability of sustained reproductive success on the underlying scale estimated from these data was approximately 0.05. Additional data accumulated over time will improve this genetic evaluation. Sustained reproductive success is important to the commercial beef industry, and results from this evaluation are expected to enhance the assessment of economic value of Hereford seedstock.     

Selection in Hereford cattle. II. Expected and realized response

Data from 14 inbred lines and 14 linecross groups of Hereford cattle at the San Juan Basin Research Center, Hesperus, were used to evaluate expected and realized response in birth and weaning traits and postweaning traits in males and females over a 28-yr period. There were large differences in the means and variances of the performance traits among the inbreds and linecrosses, with the inbreds showing inbreeding depression and greater variability among lines, while the linecrosses manifested within-breed heterosis. Except for gain from weaning to 12 mo, in females, genetic progress was expected in all traits studied, mainly due to sire selection. Regressions of annual trait means on years indicated positive phenotypic trends in the inbreds for heart girth circumference at birth, adjusted weaning weight (adjusted for inbreeding), weaning score, final weight, feed consumption and the yearling weights and gains in females. Changes were negative for other traits. In the linecross group phenotypic trends were positive in all traits except heart girth circumference, weaning age, initial test weight and feed efficiency. Estimated genetic progress per generation due to within-line selection was negative in most of the traits in the inbreds but was considerably positive for the linecrosses for most of the traits. As expected, between-line selection yielded greater genetic improvement in the inbred than in the linecross population. The different patterns of response in the two populations are attributed to high rates and levels of inbreeding. Although variable, the actual progress was below prediction in most of the traits studied.     

Dwarfism in Hereford cattle: a genetic morphological and biochemical study

A study of 40 Hereford cattle dwarfs in New Zealand confirmed that dwarfism in this country was morphologically the same as that described in North American Herefords and that its mode of inheritance was as an autosomal recessive trait. The histological architecture of growth plates was essentially normal but palisading columns were shorter and more irregular than in controls. A small proportion of chondrocytes in dwarf cartilage showed increased areas of cytoplasmic metachromasia, which probably coincided with increased cystic dilations of endoplasmic reticulum containing granular material as noted by electronmicroscopy. The above growth-plate abnormalities were neither prominent nor consistent enough to be of diagnostic significance; nor do they currently help understanding of the underlying pathogenic mechanism of dwarfing. Histological and mucopolysaccharide excretion studies unequivocally demonstrated that this disease is not a mucopolysaccharidosis as had previously been reported.