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Insulin-like peptide 3 (INSL3) is a constitutive product of mature, adult-type Leydig cells of the testes and consequently in most mammals is an ideal biomarker with which to monitor pubertal development. A new heterologous time-resolved fluorescence immunoassay was developed and validated to measure circulating INSL3 in the blood of adult male dogs. Compared to other species, INSL3 concentration is low with marked variation between individuals, which appears to be independent of breed, age, or weight. A model system was then used in which a cohort of beagle dogs was subject to a GnRH-agonist implant to suppress the HPG axis and spermatogenesis, followed by implant removal and recovery. Unlike testosterone, INSL3 levels were not fully suppressed in all animals by the GnRH agonist, nor was the recovery of Leydig cell function following implant removal uniform or complete, even after several weeks. In dogs, and dissimilar from other species (including humans), Leydig-cell INSL3 appears to be quite variable between individual dogs and only weakly connected to the physiology of the HPG axis after its suppression by a GnRH-agonist implant and recovery. Consequently, INSL3 may be less useful in this species for the assessment of testis function.

Ovine footrot is a complex multifactorial infectious disease, causing lameness in sheep with major welfare and economic consequences. Dichelobacter nodosus is the main causative bacterium; however, footrot is a polymicrobial disease with Fusobacterium necrophorum, Mycoplasma fermentans and Porphyromonas asaccharolytica also associated. There is limited understanding of the host response involved. The proinflammatory mediators, interleukin (IL)-1β and C-X-C Motif Chemokine Ligand 8 (CXCL8), have been shown to play a role in the early response to D. nodosus in dermal fibroblasts and interdigital skin explant models. To further understand the response of ovine skin to bacterial stimulation, and to build an understanding of the role of the cytokines and chemokines identified, primary ovine interdigital fibroblasts and keratinocytes were isolated, cultured and stimulated. The expression of mRNA and protein release of CXCL8 and IL-1β were measured after stimulation with LPS, D. nodosus or F. necrophorum, which resulted in increased transcript levels of IL-1β and CXCL8 in the M. fermentans-free cells. However, only an increase in the CXCL8 protein release was observed. No IL-1β protein release was detected, despite increases in IL-1β mRNA, suggesting the signal for intracellular pre-IL-1β processing may be lacking when culturing primary cells in isolation. The keratinocytes and fibroblasts naturally infected with M. fermentans showed little response to the LPS, a range of D. nodosus preparations or heat-inactivated F. necrophorum. Primary single cell culture models complement ex vivo organ culture models to study different aspects of the host response to D. nodosus. The ovine keratinocytes and fibroblasts infected with M. fermentans had a reduced response to the experimental bacterial stimulation. However, in the case of footrot where Mycoplasma spp. are associated with diseased feet, this natural infection gives important insights into the impact of multiple pathogens on the host response.

Potato (Solanum tuberosum L.) has low phosphorus (P) use efficiency as compared with other vegetable crops. This study was conducted at two commercial chipping potato farms (A and B) in Northeast Florida to evaluate different P rates for potato production. Plot size was 0.62 and 0.49 hectares for Farms A and B, respectively. The total trial area was 13.32 hectares per growing season for three consecutive years from 2018 to 2020. The randomized complete block design (RCBD) was employed with four replications per P rate. The chipping potato variety, ‘Atlantic’ was cultivated with three P rates: 0, 24.5, and 48.9 kg P ha−1 in 2018, and 12.2, 24.5, and 48.9 kg P ha−1 in 2019 and 2020. The soil of Farm A contained 497 mg kg−1 Mehlich-3 extractable P and 946 mg kg−1 aluminum (Al), and that of Farm B had 220 mg kg−1 Mehlich-3 extractable P and 253 mg kg−1 Al. The results showed that a P rate of 48.9 kg P ha−1 significantly improved tuber yield as compared to 0 in 2018 or 12.2 kg P ha−1 in 2019 and 2020. Application of 48.9 kg P ha−1 fertilizer P significantly increased the soil P level in 2018 and 2020, while the application of 24.5 kg P ha−1 fertilizer P increased the soil P level significantly in 2018 only. Tubers with 48.9 kg P ha−1 showed significantly lower external quality issues than 0 or 12.2 and 24.5 kg P ha−1. However, there were no significant differences in specific gravity, internal tuber quality, and tuber size among the different P rates. The tuber yield data show that potato plants grown on soil with high legacy P still require approximately 50 kg ha−1 P application for sustainable potato production in the area. This high P requirement results from the combination of high concentrations of active metals (Al and iron (Fe)) and a decrease in pH of one unit in the growing season. New P-fertilization programs with post-plant applications rather than with pre-plant application are urgently needed for minimizing P-immobilization by Al and Fe and improving P-use efficiency for potato production in the state.

Chlamydia abortus, the aetiological agent of enzootic abortion of ewes, is a major cause of reproductive loss in small ruminants worldwide, accounting for significant economic losses to the farming industry. Disease can be managed through the use of commercial inactivated or live whole organism-based vaccines, although both have limitations particularly in terms of efficacy, safety and disease-associated outbreaks. Here we report a comparison of two experimental vaccines (chlamydial outer membrane complex (COMC) and octyl glucoside (OG)-COMC) based on detergent extracted outer membrane preparations of C. abortus and delivered as prime-boost immunisations, with the commercial live vaccine Cevac® Chlamydia in a pregnant sheep challenge model. No abortions occurred in either experimental vaccine group, while a single abortion occurred in the commercial vaccine group. Bacterial shedding, as a measure of potential risk of transmission of infection to naïve animals, was lowest in the COMC vaccinated group, with reductions of 87.5%, 86.4% and 74% observed for the COMC, OG-COMC and live commercial vaccine groups, respectively, compared to the unvaccinated challenge control group. The results show that the COMC vaccine performed the best and is a safer efficacious alternative to the commercial vaccines. However, to improve commercial viability, future studies should optimise the antigen dose and number of inoculations required.