Crossbreeding with a tropically adapted Bos taurus breed (Senepol) to improve meat quality and production from Brahman herds in Northern Australia. 1. Steer performance

The performance of four year groups of Brahman and F1 Senepol × Brahman steers was compared grazing buffel pasture at the Douglas-Daly Research Farm, Douglas-Daly, NT, Australia. F1 Senepol × Brahman steers were on average 32 kg heavier at turnoff at ~18 months of age (P < 0.001) as a result of higher average weaning weights (+19 kg, P < 0.001) and higher growth during the post-weaning year (+12 kg, P < 0.001). These results, combined with previous studies that found that F1 Senepol × Brahman steers had more tender meat and performed better than Brahman in an Indonesian feedlot, indicate that crossbreeding with a tropically adapted Bos taurus breed, such as Senepol, could be an effective way for north Australian cattle producers with Brahman herds to produce cattle that perform well under northern conditions, and are suited to both the live export and domestic markets.

Managing plasma P concentrations in beef heifers with a slow release vitamin D supplementation

Context In extensive northern grazing systems, supplementation of P is recommended to maximise cattle growth rates and reproduction. Improving the absorption of P for the animal by influencing metabolic pathways has the potential to improve both the productivity and profitability of extensive livestock enterprises. Aims This study evaluated the efficacy of rumen bolus containing 25-hydroxyvitamin D (25OHD), commercially available as Hy-D®, and/or monensin on blood P and Ca concentrations in young cattle. Methods A total of 84 heifers, initial liveweight (mean ± s.e.m.) 184 ± 2.0 kg, were allocated to four groups, dosed with one of four slow release bolus: (1) placebo (control), (2) monensin (120 mg/day), (3) Hy-D® (6 mg/day), or (4) monensin with Hy-D®, and managed on a common unimproved native pasture from August 2012 to February 2013. On four occasions postdosing, liveweight, hip height and body condition scores were recorded, and individual faecal and jugular blood samples were collected. Key results Supplementation with monensin had a significant effect (P < 0.05) on average daily gains for the first 25 days. Interactions between 25OHD and monensin and time × monensin were also significant (P < 0.05). After 188 days, heifers receiving monensin or 25OHD + monensin were 5 and 10 kg heavier respectively, compared with their counterparts in the control and 25OHD groups. Plasma P concentrations at 25 days were 6.6 mg/dL, then increased to between 8.5 and 9.0 mg/dL and maintained this level for up to 109 days with a bolus releasing 6.0 mg/day 25OHD. Conclusions The study demonstrated that sustained and elevated plasma concentrations of both 25OHD and P, compared with control animals, can be achieved. The slow release rumen bolus maintained an elevated plasma concentration of 25OHD, and indicated that a target plasma concentration for 25OHD for increasing P absorption in beef cattle is between 200 and 300 ng/mL. Implications Supplementation of a metabolite of vitamin D influences P metabolism in Brahman heifers under grazing conditions. Integration with standard supplementation practices would optimise growth rates and reproductive performance.

The economics of phosphorus supplementation of beef cattle grazing northern Australian rangelands

Context Phosphorus (P) deficiency occurs in beef cattle grazing many rangeland regions with low-P soils, including in northern Australia, and may severely reduce cattle productivity in terms of growth, reproductive efficiency and mortality. However, adoption of effective P supplementation by cattle producers in northern Australia is low. This is likely to be due to lack of information and understanding of the profitability of P supplementation where cattle are P-deficient. Aims The profitability of P supplementation was evaluated for two dissimilar regions of northern Australia, namely (1) the Katherine region of the Northern Territory, and (2) the Fitzroy Natural Resource Management (NRM) region of central Queensland. Methods Property-level, regionally relevant herd models were used to determine whole-of-business productivity and profitability over 30 years. The estimated costs and benefits of P supplementation were obtained from collation of experimental data and expert opinion of persons with extensive experience of the industry. The economic consequences of P supplementation at the property level were assessed by comparison of base production without P supplementation with the expected production of P-supplemented herds, and included the implementation phase and changes over time in herd structure. In the Katherine region, it was assumed that the entire cattle herd (breeders and growing cattle) grazed acutely P-deficient land types and the consequences of (1) no P supplementation, or P supplementation during (2) the dry season, or (3) both the wet and dry seasons (i.e. 3 scenarios) were evaluated. In the Fitzroy NRM region, it was assumed that only the breeders grazed P-deficient land types with three categories of P deficiency (marginal, deficient and acutely deficient), each with either (1) no P supplementation, or P supplementation during (2) the wet season, (3) the dry season, or (4) both the wet and dry seasons (i.e. 12 scenarios). Key results In the Katherine region, year-round P supplementation of the entire cattle herd (7400 adult equivalents) grazing acutely P-deficient pasture resulted in a large increase in annual business profit (+AU$500000). Supplementing with P (and N) only in the dry season increased annual business profit by +AU$200000. In the Fitzroy NRM region, P supplementation during any season of the breeder herd grazing deficient or acutely P-deficient pastures increased profit by +AU$2400–AU$45000/annum (total cattle herd 1500 adult equivalents). Importantly, P supplementation during the wet season-only resulted in the greatest increases in profit within each category of P deficiency, comprising +AU$5600, AU$6300 and AU$45000 additional profit per annum for marginal, deficient and acutely P-deficient herds respectively. Conclusions The large economic benefits of P supplementation for northern beef enterprises estimated in the present study substantiate the current industry recommendation that effective P supplementation is highly profitable when cattle are grazing P-deficient land types. Implications The contradiction of large economic benefits of P supplementation and the generally low adoption rates by the cattle industry in northern Australia suggests a need for targeted research and extension to identify the specific constraints to adoption, including potential high initial capital costs.

Effect of high-intensity rotational grazing on the growth of cattle grazing buffel pasture in the Northern Territory and on soil carbon sequestration

Context Scientific and anecdotal reports conflict on the effects of intensive rotational grazing (IRG) on cattle growth, and very limited objective data are available from cattle grazing in northern Australia that producers can use to decide whether to adopt IRG. Aims This study aimed to compare liveweight gain and sequestration of soil organic carbon when cattle grazed buffel grass (Cenchrus ciliaris L.) under either continuous grazing (CG) or IRG. Methods In each year of this 9-year study, a cohort of Brahman and Brahman-cross weaners was randomly allocated to IRG and CG treatments. They grazed predominantly buffel pasture at Douglas Daly Research Farm from shortly after weaning for about a year, at which time they were replaced by the next year’s group, and the average liveweight gains of the treatments over the post-weaning year were compared each year for 9 years. Soil organic carbon was measured in the topsoil (0–30 cm) twice each year for 5 years (2009–14) and changes in carbon stocks over time were compared between treatments. Key results In each year of this study, the growth of cattle grazing buffel pasture was lower under IRG than CG. In each year, liveweight gain was lower (P < 0.05) per head and per hectare under IRG. Topsoil soil organic carbon stocks did not increase in the IRG treatment over the 5 years of this study. Conclusions This study found that cattle growth, both per head and per hectare, was lower under IRG than CG, and that IRG did not result in any increase in soil organic carbon over time. Implications The lower per head and per area production from the IRG system, combined with the extra infrastructure and operating costs for IRG systems, make it unlikely that adoption of IRG would improve the profitability of cattle-grazing operations on similar pasture systems in northern Australia. However, the findings of this study may not apply to other pasture systems and environments.

Functional profiling of live melanoma samples using a novel automated platform

Aims

This proof-of-concept study was designed to determine if functional, pharmacodynamic profiles relevant to targeted therapy could be derived from live human melanoma samples using a novel automated platform.

Methods

A series of 13 melanoma cell lines was briefly exposed to a BRAF inhibitor (PLX-4720) on a platform employing automated fluidics for sample processing. Levels of the phosphoprotein p-ERK in the mitogen-activated protein kinase (MAPK) pathway from treated and untreated sample aliquots were determined using a bead-based immunoassay. Comparison of these levels provided a determination of the pharmacodynamic effect of the drug on the MAPK pathway. A similar ex vivo analysis was performed on fine needle aspiration (FNA) biopsy samples from four murine xenograft models of metastatic melanoma, as well as 12 FNA samples from patients with metastatic melanoma.

Results

Melanoma cell lines with known sensitivity to BRAF inhibitors displayed marked suppression of the MAPK pathway in this system, while most BRAF inhibitor-resistant cell lines showed intact MAPK pathway activity despite exposure to a BRAF inhibitor (PLX-4720). FNA samples from melanoma xenografts showed comparable ex vivo MAPK activity as their respective cell lines in this system. FNA samples from patients with metastatic melanoma successfully yielded three categories of functional profiles including: MAPK pathway suppression; MAPK pathway reactivation; MAPK pathway stimulation. These profiles correlated with the anticipated MAPK activity, based on the known BRAF mutation status, as well as observed clinical responses to BRAF inhibitor therapy.

Conclusion

Pharmacodynamic information regarding the ex vivo effect of BRAF inhibitors on the MAPK pathway in live human melanoma samples can be reproducibly determined using a novel automated platform. Such information may be useful in preclinical and clinical drug development, as well as predicting response to targeted therapy in individual patients.

Abstract P6-04-06: Stratification of Breast Cancers Based on Functional Phosphoprotein Signaling Profiles Elicited from Live Tumor Cells

Background: Abnormal signal transduction networks are frequent targets of existing and emerging molecularly targeted agents (MTAs). Unfortunately, most predictive biomarkers to guide therapeutic selection are based on indirect assessment of signal transduction through DNA mutations or transcriptional profiles rather than dynamic assessment of signal transduction proteins themselves. Classification of breast cancer based on functional signaling profiles derived from a set of signaling phosphoproteins induced upon growth factor stimulation of live breast cancer cells is likely to provide a more accurate system for MTA selection than indirect methods utilizing fixed or frozen tissue. Objective: This study aimed to demonstrate stratification of multiple breast cancer model systems based on functional signaling profiles elicited from live tumor cells in response to ex vivo stimuli. Methods: Breast cancer cell lines (MCF-7, HCC-1937, MDA-MB-231, BT474, and SKBR3) were exposed to either vehicle (control) or stimulated with 200 ng/ml epidermal growth factor (EGF) for 5 minutes then lysed and proteins extracted. Mean Fluorescence Intensity (MFI) levels of six phosphoproteins (pEGFR, pErk, pAkt, pP70S6K, pGSK3β, and pSTAT3) were determined in sextuplet using a multiplexed bead-immunoassay (BioPlex, BioRad) and a modulation score (MS), defined as the log 2 (MFI stimulated /MFI contrd), calculated for each. Scores were ranked by percentile relative to the median (0.66) and inter-quartile range (IQR) (154). Moderate responders were classified as those with MS between the 75th percentile (2.20) and the 75th percentile plus the IQR (3.74). High responders were those MS > 3.74. Low responders were those MS falling between the IQR and 75th percentile (1.54-2.20) whereas non responders were classified as MS < 1.54 Results: EGF stimulation resulted in high levels of EGFR-phosphorylation in all cells except BT474, which responded moderately (2.57). MS for pErk were high in MCF-7 cells (3.92), moderate in HCC -1937 (2.89) and none for the other lines tested. Moderate STAT-3 phosphorylation was observed in only MCF-7cells (2.34) whereas low pAkt MS were observed in only SKBR3 (1.78). All other markers across the five cell lines tested were non responders (< 1.54), with pGSK3β and pP70S6K yielding MS < 1.0 for all five cell lines. Interestingly, the relative MS rank order of all six proteins differed across each cell line suggesting further opportunity for stratification. Conclusions: Our data demonstrate that different breast cancer cell lines display unique functional phosphoprotein signaling profiles, thereby providing a mechanism for stratifying tumors based on individual signal transduction pathway activation. Further studies are underway to correlate the functional signaling profiles identified here to sensitivity and resistance to specific MTA treatment.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-04-06.

Two alternative structures can be formed by IHF protein binding to the plasmid R6K gamma origin

Escherichia coli integration host factor (IHF) contributes to the regulation of R6K plasmid copy number by counteracting the inhibitory activity of the plasmid-encoded replication protein pi. Two IHF-binding sites (ihf1 and ihf2) flank seven iterons in the origin which bind pi protein. As previously shown by electron microscopy, IHF can compact a large segment of the R6K gamma origin DNA, encompassing site ihf1, an AT-rich domain containing ihf1, and some of the seven iterons located downstream of ihf1. We termed this phenomenon IHF-mediated DNA folding. This folding requires a high IHF concentration, and the region of the origin (replication enhancer) located to the left of the AT-rich domain. However, site ihf2 is not necessary in forming the folded structure. As reported here, IHF binding to ihf2 can be detected in gel mobility shift assays only if the leftmost enhancer region is absent. Sites ihf1 and ihf2 each contain two consensus IHF sequences. Site-directed mutagenesis was performed to determine which sequences are recognized by IHF protein and which sites are involved in forming the various gamma origin-IHF complexes. Finally, we define the boundaries of protection from DNaseI digestion when IHF is bound to ihf2. We propose a model in which IHF protein bound to ihf1, in the absence of the enhancer region, facilitates IHF binding to ihf2.