A.J. Parker

How feasible is it to replace urea with nitrates to mitigate greenhouse gas emissions from extensively managed beef cattle

Reducing methane emissions from cattle in Australia will be dependent upon finding a strategy that can be readily adopted by its northern beef industry. The majority of the herd are located in this region and they graze low-quality tropical (C4) pastures, resulting in high methane output. There are few mitigation options that can be readily applied to extensively grazed cattle. The addition of nitrate to the diet of cattle has been shown to reduce methane production and may be an applicable strategy in northern Australia. Nitrogen is often the primary limiting nutrient in low-quality tropical pastures and it is common practice by industry to supplement with urea. Supplying an equivalent dose of nitrogen using nitrate as an alternative to urea has been demonstrated in cattle without adverse impacts upon animal productivity or health. These findings may not be directly applicable to grazing cattle in northern Australian because the diets and feeding management are not representative of the region. Nitrite toxicity can result from feeding nitrates to livestock and there is evidence that the composition of the total diet and feeding pattern influences the risk of toxicity. If nitrate supplementation in grazing beef cattle in northern Australia can be demonstrated to reduce methane and be applied safely, adoption rates will still depend on carbon market pricing. Current modelling suggests that the cost of supplementing beef cows with nitrate in northern Australia would be at least double the cost of urea supplementation.

The effect of feeding frequency and dose rate of nitrate supplements on blood haemoglobin fractions in Bos indicus cattle fed Flinders grass (Iseilemia spp.) hay

Twelve Bos indicus steers (liveweight ± s.d., 317.8 ± 28.5) kg were used in an experiment to examine two factors: daily nitrate dose (0, 30, 40 or 50 g of nitrate/day) and feeding frequency (once or twice a day) on methaemoglobin concentration, daily peak methaemoglobin concentration, rate of incline for methaemoglobin concentration, carboxyhaemoglobin concentration, oxyhaemoglobin concentration, total haemoglobin concentration, haematocrit and dry matter intake of Flinders grass hay. Increasing the dose rate of nitrate increased the fraction of methaemoglobin in the blood of steers (P = 0.014). A highly significant effect was demonstrated for the interaction of dose rate × day (P < 0.001). For once a day intake of nitrate, the dose rates of 40 and 50 g per day showed a greater increase in mean methaemoglobin values than for the 0 and 30 g of nitrate per day. Increasing the dose rate of nitrate also increased the daily peak methaemoglobin fraction and the rate of incline to peak methaemoglobin values for both once and twice a day feeding of the nitrate supplements. However, increasing the dose of nitrate had no significant overall effect on total haemoglobin, deoxyhaemoglobin, carboxyhaemoglobin, haematocrit or dry matter intake. Twice a day feeding of nitrate decreased the formation of methaemoglobin in the blood of Bos indicus steers. This study demonstrates that caution should be exercised when feeding nitrates as a non-protein nitrogen source to cattle grazing low quality pastures in northern Australia.

A survey of the meat goat industry in Queensland and New South Wales. 2. Herd management, reproductive performance and animal health

An interview-based questionnaire survey was conducted on 31 goat properties in New South Wales and Queensland in 2013. This study has gathered information on goat herd management, reproductive performance and animal health, and has identified constraints that may limit goat productivity. Producers from high-rainfall regions reported having full blood Boer goats for stud breeding. In contrast, producers from pastoral regions had rangeland goats and Boer-cross goats. Overall, 87% of the producers identified a natural breeding season in goats and 61% separated kids from their mothers at weaning. The weaning age varied between 3.0 and 6.0 months. A total of 52% of producers castrated male kids. Only 10% of producers used ultrasound to conduct pregnancy diagnosis on their goats. The reported pregnancy rate was 60% for the pastoral regions and 94% for the high-rainfall regions. The average prolificacy was 1.4 kids/doe and the kidding interval was 12 months. Overall, 68% of producers fed their goat herd with supplements, with the exception that most producers from western New South Wales and south-western Queensland did not use supplements. Producers considered gastrointestinal parasites (61%) and body lice (48%) as the main diseases associated with their goat herds, although only 52% mentioned drenching the animals with anthelmintics. In general, properties in the pastoral regions showed low pregnancy and kidding rates, early age at first mating, high mortality rates, poor performance of Boer bucks and lower weights and weight gain compared with properties in the high-rainfall regions. The survey has highlighted areas that require further study to validate the observations of producers, for instance, factors that may be limiting the fertility of Boer goats in rangeland environments, the incidence of diseases, the use of Kidplan and management activities to improve goat productivity.

A technique for sampling blood from cattle during transportation

A technique for the safe sampling of blood from cattle during transportation is described. The technique was validated using four 2.5-year-old Bos indicus steers held in stalls on a stationary body truck for 2 h, transported for 4 h and then held on a stationary truck for a further 2 h. The length of time required to take a blood sample from one animal using this technique was 30 s. Information gathered using this technique will be helpful in understanding the physiological reactions of cattle to transportation.

An economic case study of entire male grain-fed beef from a north-western Queensland production system

Assessing the differences in gross margins for a north-western Queensland beef-production system was undertaken using herd-budgeting software. The analysis reviewed the viability of producing beef for the domestic market from either a steer or bull production system. A hypothetical herd of 1200 breeders was created for the case study evaluation. An integrated beef production system from breeding to feedlot finishing was found to be less profitable for bull beef production than for steers at the current market prices. Although bull production was more profitable than steer production during the feedlot phase, the production of bulls in this phase failed to compensate for the earlier economic losses in the weaning phase of –AU

Hypovitaminosis A in extensively grazed beef cattle

24.04 per adult equivalent for bulls. During the feedlot phase, bull production systems had lower break-even sale prices than did steer production systems. In reviewing two pricing scenarios for bulls, it was found that marketing bulls at the same price as steers was the most profitable production system. We conclude that the production of bull beef from a north-western Queensland production system can be profitable only if bulls can be sold without discount relative to steers.

Revisiting summer infertility in the pig: could heat stress-induced sperm DNA damage negatively affect early embryo development?

CASE REPORT Vitamin A deficiency was diagnosed in a herd of 97 19-month-old Braford heifers in the Mitchell Grass Downs (Astrebla spp.) bioregion of Hughenden in north-western Queensland during November 2015. Two heifers died after a 48-h history of sternal recumbency and of the 19 that had neurological signs, 7 were blind. Histological changes in the optic nerves of the two necropsied cattle were consistent with vitamin A deficiency. This diagnosis was supported by vitamin A concentrations in fresh liver samples of 5 and 6 mg/kg wet tissue (reference range, 100-175 mg/kg) despite treatment of the cattle with twice the recommended dose of parenteral vitamin A 3 weeks prior to sampling. Rainfall on the property during the 2 years before the outbreak was less than the annual rainfall average of 464 mm, with a total of 281 mm in 2014 and 117 mm from January to November in 2015, most of this falling in January. CONCLUSION Plant assays for both β-carotene and crude protein concentrations in dry matter (DM) were less than the recommended dietary requirements for beef cattle (0.30 mg/kg DM and 56 g/kg, respectively).

Vitamin A deficiency in Bos indicus heifers fed a wheat straw diet cannot be corrected with algae lick blocks or intramuscular injectable retinyl palmitate treatments

Temperature is a crucial factor in mammalian spermatogenesis. The scrotum, pampiniform plexus, and cremaster and dartos muscles in mammals are specific adaptations to ensure sperm production in a regulated environment 4-6°C below internal body temperature. However, the limited endogenous antioxidant systems inherent in mammalian spermatozoa compounded by the loss of cytosolic repair mechanisms during spermatogenesis, make the DNA in these cells particularly vulnerable to oxidative damage. Boar sperm is likely to be more susceptible to the effects of heat stress and thus oxidative damage due to the relatively high unsaturated fatty acids in the plasma membrane, low antioxidant capacity in boar seminal plasma, and the boar’s non-pendulous scrotum. Heat stress has a significant negative impact on reproductive performance in piggeries, which manifests as summer infertility and results in productivity losses that amount to millions of dollars. This problem is particularly prevalent in tropical and subtropical regions where ambient temperatures rise beyond the animal’s zone of thermal comfort. Based on preliminary studies in the pig and other species, this article discusses whether heat stress could induce sufficient DNA damage in boar sperm to significantly contribute to the high rates of embryo loss and pregnancy failure observed in the sow during summer infertility. Heat stress-induced damage to sperm DNA can lead to disrupted expression of key developmental genes essential for the differentiation of early cell lineages, such as the trophectoderm, and can distort the timely formation of the blastocyst; resulting in a failure of implantation and ultimately pregnancy loss. Confirming such a link would prompt greater emphasis on boar management and strategies to mitigate summer infertility during periods of heat stress.

Bos indicus cattle possess greater basal concentrations of HSP27, alpha B-crystallin, and HSP70 in skeletal muscle in vivo compared with Bos taurus cattle

Serum and liver retinol concentrations and blood β-carotene concentrations were studied in 30 Bos indicus heifers rendered deficient of vitamin A over 180 days and then given treatments of access to algae-based lick blocks (n = 10), injectable retinyl palmitate and molasses-based lick blocks (n = 10), or a negative control given access to molasses-based lick blocks only (n = 10). All heifers became deficient in blood and liver vitamin A, as well as blood β-carotene by 180 days. There was no treatment effect on bodyweight (P = 0.347). However, a highly significant effect of time (P = 0.001) was detected where all heifers achieved an average daily gain of 0.74 kg/day throughout the depletion phase of the study but lost 0.150 kg/day during the repletion phase. The concentrations of serum and liver retinol and blood β-carotene were not different between treatment groups (P = 0.362, P = 0.535 and P = 0.839) during the depletion or repletion phases of the study. All heifers continued to be rendered deficient in the concentrations of serum and liver retinol and blood β-carotene throughout the experiment demonstrating a highly significant effect of time (P = 0.001). Injectable retinyl palmitate (818 100 IU retinol) or access to algal lick blocks (4180 IU retinol) did not elevate blood or liver retinol concentrations in heifers rendered deficient of vitamin A. It is speculated that the protein-deficient diet fed to the heifers had an adverse effect on the blood retinol transport proteins.

Effect of hormonal synchronisation and/or short-term supplementation with maize on follicular dynamics and hormone profiles in goats during the non-breeding season.

The objectives of the present study were to evaluate the basal concentrations of heat shock proteins (HSP) between and cattle and to determine if HSP basal concentrations change as an animal matures. A total of 40 cattle were used in a 2 × 2 factorial design to evaluate the effects of genotype and age (heifers and mature cows) on basal concentrations of heat shock protein 27 (HSP27), α B-crystallin (Cryab), and heat shock protein 70 (HSP70). Each experimental group of 10 animals was sampled on a separate day over a period of 4 wk during July 2014. A muscle sample was collected from the longissimus thoracis (LT) and concentrations of HSP were quantified using ELISA. There were no significant differences in HSP concentration for the interaction between age and genotype or for age alone. cattle had greater ( < 0.05) basal concentrations of HSP27, Cryab, and HSP70 in the LT than cattle. The results of this study show that basal in vivo HSP concentrations differ between and cattle. However, further studies are needed to investigate the relationship between HSP concentrations and meat tenderness with respect to genotypes to see if HSP concentrations account for at least some variability in tenderness differences.