BackgroundCattle are bred for, amongst other factors, specific traits, including parasite resistance and adaptation to climate. However, the influence and inheritance of mitochondrial DNA (mtDNA) are not usually considered in breeding programmes. In this study, we analysed the mtDNA profiles of cattle from Victoria (VIC), southern Australia, which is a temperate climate, and the Northern Territory (NT), the northern part of Australia, which has a tropical climate, to determine if the mtDNA profiles of these cattle are indicative of breed and phenotype, and whether these profiles are appropriate for their environments.ResultsA phylogenetic tree of the full mtDNA sequences of different breeds of cattle, which were obtained from the NCBI database, showed that the mtDNA profiles of cattle do not always reflect their phenotype as some cattle with Bos taurus phenotypes had Bos indicus mtDNA, whilst some cattle with Bos indicus phenotypes had Bos taurus mtDNA. Using D-loop sequencing, we were able to contrast the phenotypes and mtDNA profiles from different species of cattle from the 2 distinct cattle breeding regions of Australia. We found that 67 of the 121 cattle with Bos indicus phenotypes from NT (55.4%) had Bos taurus mtDNA. In VIC, 92 of the 225 cattle with Bos taurus phenotypes (40.9%) possessed Bos indicus mtDNA. When focusing on oocytes from cattle with the Bos taurus phenotype in VIC, their respective oocytes with Bos indicus mtDNA had significantly lower levels of mtDNA copy number compared with oocytes possessing Bos taurus mtDNA (P < 0.01). However, embryos derived from oocytes with Bos indicus mtDNA had the same ability to develop to the blastocyst stage and the levels of mtDNA copy number in their blastocysts were similar to blastocysts derived from oocytes harbouring Bos taurus mtDNA. Nevertheless, oocytes originating from the Bos indicus phenotype exhibited lower developmental potential due to low mtDNA copy number when compared with oocytes from cattle with a Bos taurus phenotype.ConclusionsThe phenotype of cattle is not always related to their mtDNA profiles. MtDNA profiles should be considered for breeding programmes as they also influence phenotypic traits and reproductive capacity in terms of oocyte quality.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-017-0523-5) contains supplementary material, which is available to authorized users.
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.
Nine insect species endemic to tropical America have been released into the Northern Territory as biological control agents for Mimosa pigra L. (Mimosaceae). To date, few studies have been published that quantify the abundance of these agents post‐release. Hence, populations of adult agents in three stands of M. pigra were monitored using Malaise traps. Trap catches frequently contained the lepidopteran agents Carmenta mimosa Eichlin and Passoa and Neurostrota gunniella (Busck). Neurostrota gunniella, which was first released in 1989, was the most abundant of all the agents caught, irrespective of the stand of M. pigra where trapping was conducted. The three coleopteran agents (namely Acanthoscelides Schönherr spp., Chlamisus mimosae Karren and Coelocephalapion Wagner spp.) were caught less frequently. Two recently released beetles, Chalcodermus serripes Fåhraeus and Sibinia fastigiata Clark, were not caught. Trap catches of Acanthoscelides spp. were greatest during the late dry season with smaller catches during the mid‐ to late wet season. Chlamisus mimosae was most abundant during the dry to dry–wet transition. Neurostrota gunniella was generally most abundant during the dry season. The abundances of Ca. mimosa and Coelocephalapion spp. exhibited little seasonality. Malaise trapping is recommended as part of a long‐term monitoring program to quantify agent populations and their impact upon M. pigra.
The performance of Brahman heifers at their first mating as yearlings (4-year groups of ~100 per year) grazing on improved pasture in the Douglas Daly region and as 2 year olds (3-year groups of ~100 per year) grazing on native pasture in the Victoria River District was studied. The relationships between pre-mating weight and pregnancy rate were established for Brahman heifers mated as yearlings on improved pasture, and as 2 year olds on native pasture with pre-mating weights recorded in late October/early November (before the wet season starts) and in late December (just before the start of mating). These relationships were found to be different indicating that there is an interaction between age and weight that modifies the effect of weight. The relationships were used to model pregnancy rates that are likely to result from different pre-mating weights for these three scenarios. These estimates can be used to identify target mating weights for different situations, and to predict the pregnancy rates for groups of heifers, which will be useful in budgeting and assessing the profitability of different management strategies.
The performance of heifers from a Brahman herd that was selected for fertility was compared with Brahman heifers sourced from commercial properties using three year-groups of heifers. Each year, conception rates from yearling mating were significantly higher in heifers from the selected herd (SEL) than in heifers sourced from commercial properties (COM), despite the average joining weight of the SEL heifers being lower each year. The pregnancy rate in SEL heifers was 24% higher (P = 0.008) in the first year, 36% higher (P = 0.005) in the second year and 45% higher (P < 0.001) in the third year. Over the 3 years of the study, the conception rate was 35% higher (P = 0.009) in SEL heifers than in COM heifers. Joining weight also affected pregnancy rates. When heifers were split into weight ranges according to their pre-joining weight, pregnancy rates were significantly higher (P = 0.018) in the heavier weight range than the lighter one. The results indicate that selection for fertility has been successful in improving conception rates from yearling mating in SEL heifers.
The effects of low doses of melatonin (0.1, 0.5 and 1 mg) given at 16:00 h on induction and quality of sleep in the late afternoon (17:00-21:00 h), as well as on subjective fatigue and mood ratings before and after sleep were studied. Ten healthy male volunteers (age 26-30 years) were given on a doubleblind crossover basis, tablets containing melatonin, or placebo, with one day washout between treatments. Mood and fatigue were assessed before and after bedtime. Sleep quality was objectively monitored using wrist-worn actigraphs and subjectively by using sleep logs. Data were analysed by means of analysis of variance for repeated measures with a factor of group (placebo and the three melatonin doses).The analysis revealed dose-dependent increase by melatonin in subjective evaluation of fatigue and sleepiness, and decrease in alertness, efficiency, vigor and concentration before the nap. Melatonin did not significantly affect actigraph-measured nap sleep latency and efficiency but reduced wake time after sleep onset and delayed sleep offset time compared to placebo, Melatonin did not significantly affect sleep latency and sleep efficiency in the night following the treatment.These data indicate acute effects of low doses of melatonin given at 16:00h on sleepiness and fatigue but not on sleep efficiency or latency in healthy young individuals.
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 growth of 116 Brahman (BRAH) and 96 F1 Senepol × Brahman (F1 SEN) steers grazing improved Buffel pasture in the Northern Territory was compared. Average growth was 10 kg higher in F1 SEN during grazing in the 9 months following weaning. Twenty-five steers of each genotype were compared for feedlot performance and meat quality. There was no significant difference in feedlot growth over 73 days in a commercial feedlot. On average F1 SEN carcasses graded two boning groups lower in the Meat Standards Australia (MSA) grading system. While M. longissimus samples from both genotypes were quite tender (shear force <4 kg), F1 SEN samples were found to be significantly more tender than BRAH (−0.44 kg) by shear force testing. These results indicate that crossbreeding with a tropically adapted Bos taurus breed, such as the Senepol, may be a viable method for cattle producers with Brahman herds in northern Australia to improve the meat quality of the cattle they produce.
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