Genetic background of juniper (Juniperus spp.) consumption predicted by fecal near-infrared spectroscopy in divergently selected goats raised in harsh rangeland environments.

BACKGROUND: Junipers (Juniperus spp.) are woody native, invasive plants that have caused encroachment problems in the U.S. western rangelands, decreasing forage productivity and biodiversity. A potential solution to this issue is using goats in targeted grazing programs. However, junipers, which grow in dry and harsh environmental conditions, use chemical defense mechanisms to deter herbivores. Therefore, genetically selecting goats for increased juniper consumption is of great interest for regenerative rangeland management. In this context, the primary objectives of this study were to: 1) estimate variance components and genetic parameters for predicted juniper consumption in divergently selected Angora (ANG) and composite Boer x Spanish (BS) goat populations grazing on Western U.S. rangelands; and 2) to identify genomic regions, candidate genes, and biological pathways associated with juniper consumption in these goat populations. RESULTS: The average juniper consumption was 22.4% (± 18.7%) and 7.01% (± 12.1%) in the BS and ANG populations, respectively. The heritability estimates (realized heritability within parenthesis) for juniper consumption were 0.43 ± 0.02 (0.34 ± 0.06) and 0.19 ± 0.03 (0.13 ± 0.03) in BS and ANG, respectively, indicating that juniper consumption can be increased through genetic selection. The repeatability values of predicted juniper consumption were 0.45 for BS and 0.28 for ANG. A total of 571 significant SNP located within or close to 231 genes in BS, and 116 SNP related to 183 genes in ANG were identified based on the genome-wide association analyses. These genes are primarily associated with biological pathways and gene ontology terms related to olfactory receptors, intestinal absorption, and immunity response. CONCLUSIONS: These findings suggest that juniper consumption is a heritable trait of polygenic inheritance influenced by multiple genes of small effects. The genetic parameters calculated indicate that juniper consumption can be genetically improved in both goat populations.

Serologic and bacteriologic culture prevalence of Corynebacterium pseudotuberculosis infection in goats and sheep and use of Bayesian analysis to determine value of assay results for prediction of future infection.

OBJECTIVE: To determine the serologic and bacteriologic culture prevalence of Corynebacterium pseudotuberculosis infection in sheep and goats and the value of such assays for prediction of future development of caseous lymphadenitis (CL). DESIGN: Observational study. ANIMALS: 919 goats and sheep in 3 herds in southwest Texas. PROCEDURES: During an initial evaluation, serologic and bacteriologic culture status for CL was determined for all animals. Subsequently, animals were evaluated every 6 months for a 13-month period to detect external CL lesions. Affected animals in 2 herds were treated with tulathromycin or a control treatment; affected animals in 1 herd were culled. The value of assays for prediction of future development of CL lesions was determined. RESULTS: The serologic prevalence of CL in herds at the start of the study ranged from 7.52% to 69.54%. The bacteriologic culture prevalence of CL ranged from 0% to 6.12% at the start of the study and 0% to 9.56% at the end of the study. Synergistic hemolysin inhibition results were poor predictors of future development of CL lesions in animals during the study period; however, animals with positive bacteriologic culture results for CL were more likely to develop lesions in the future than were animals with negative bacteriologic culture results. CONCLUSIONS AND CLINICAL RELEVANCE: Caseous lymphadenitis was detected in animals in this study despite prior management of affected animals in herds via culling. Use of a synergistic hemolysin inhibition test for management of CL may cause unnecessary culling of animals; treatment might allow retention of genetically valuable CL-affected animals in a herd without substantially increasing the prevalence of CL.

Extended scrapie incubation time in goats singly heterozygous for PRNP S146 or K222.

Scrapie is the transmissible spongiform encephalopathy (TSE) of sheep and goats, and scrapie eradication in sheep is based in part on strong genetic resistance to classical scrapie. Goats may serve as a scrapie reservoir, and to date there has been no experimental inoculation confirming strong genetic resistance in goats. Two prion protein variants (amino acid substitutions S146 and K222) in goats have been significantly underrepresented in scrapie cases though present in scrapie-exposed flocks, and have demonstrated low cell-free protein conversion efficiency to the disease form (PrP(D)). To test degree of genetic resistance conferred in live animals with consistent exposure, we performed the first oral scrapie challenge of goats singly heterozygous for either PRNP S146 or K222. All N146-Q222 homozygotes became clinically scrapie positive by an average of 24months, but all S146 and K222 heterozygotes remain scrapie negative by both rectal biopsy and clinical signs at significantly longer incubation times (P<0.0001 for both comparisons). Recent reports indicate small numbers of S146 and K222 heterozygous goats have become naturally infected with scrapie, suggesting these alleles do not confer complete resistance in the heterozygous state but rather extend incubation. The oral challenge results presented here confirm extended incubation observed in a recent intracerebral challenge of K222 heterozygotes, and to our knowledge provide the first demonstration of extended incubation in S146 heterozygotes. These results suggest longer relevant trace-back histories in scrapie-eradication programs for animals bearing these alleles and strengthen the case for additional challenge experiments in both homozygotes to assess potential scrapie resistance.

Evaluation of homologous and heterologous protection induced by a virulent field strain of orf virus and an orf vaccine in goats.

OBJECTIVE: To evaluate cross protection provided by administration of contagious ecthyma vaccines against strains of orf virus in goats. ANIMALS: 126 Boer-Spanish crossbred goats (3 to 20 days old). PROCEDURES: 85 goats were vaccinated with a goat-derived contagious ecthyma vaccine. Of these, 41 were challenge exposed with the virus strain for the contagious ecthyma vaccine, 40 were challenge exposed with a more virulent field strain of orf virus, and 4 were lost to predation or died. Another 41 goats were vaccinated with a vaccine produced from a more virulent field strain of orf virus; of these, 18 were challenge exposed with the virus strain of the goat-derived contagious ecthyma vaccine, 18 were challenge exposed with the more virulent field strain of orf virus, and 5 were lost to predation or died. RESULTS: Vaccination with the goat-derived contagious ecthyma vaccine did not significantly reduce the number of goats with lesions or lesion severity caused by challenge exposure with the more virulent field strain of orf virus. Vaccination with the vaccine produced from the more virulent field strain of orf virus significantly reduced the number of goats with lesions attributable to challenge exposure with the virus strain of the goat-derived contagious ecthyma vaccine, but it failed to significantly reduce lesion severity. CONCLUSIONS AND CLINICAL RELEVANCE: Vaccination did not result in cross protection for the 2 strains of orf virus. This may have been attributable to antigenic differences and may be a factor in outbreaks of contagious ecthyma in vaccinated goats.