Impacts of major health conditions affecting the Australian sheepmeat value chain: a review

Major health conditions in sheep contribute to substantial economic losses throughout the sheepmeat supply chain in Australia. A systematic review was undertaken to explore the measurable impact of six conditions: arthritis, sheep measles, pleurisy, pneumonia, grass seeds and rib fractures, on the production of lamb and mutton across the meat value chain. Peer‐reviewed scientific literature from three databases and non‐peer‐reviewed articles and reports from Australian government and non‐government websites were searched between 11 and 17 November 2019. Original articles, including studies conducted in Australia and New Zealand, that had measurable impacts on conditions of interest were included. The search yielded 16 articles and reports and were classified as producer impact and/or processor impact studies. Mortalities were quantified for pneumonia and arthritis, with pneumonia having the highest impact for producers. Grass seed infestation resulted in the highest impact on carcase and liveweight losses compared to arthritis and pneumonia. Arthritis had the highest trim weight losses for both lamb and mutton and the highest rate of carcase condemnation. Grass seed was the only condition where other impacts on the processor (chain speed and staff relocation to the boning room) were quantified. Although quantifiable production and processing losses were available for some conditions, this review has highlighted that limited quantifiable data based on scientifically sound research were not available for other conditions. The evidence for some conditions found in this review can be used to target future research activities and to further assist producers in making informed management decisions on prevention and control.     

The use of toltrazuril for the prevention of coccidiosis in piglets before weaning

SUMMARY: To determine the efficacy of toltrazuril as a prophylactic treatment for coccidiosis in piglets caused by Isospora suis (I suis) , a single 1.0 mL dose of toltrazuril was administered orally to 1056 piglets between 3 and 6 days of age, in 5 piggeries. Prophylactic treatment of piglets reduced the occurrence of coccidiosis in litters from 71% to 22%. The number of antibacterial treatments given and the number of piglets affected per litter were also significantly reduced, resulting in some improvement in growth rates to weaning. The severity of diarrhoea was significantly reduced, as was the amount of oocyst excretion. The number of days that piglets excreted oocysts in the faeces was reduced from 4.9 days to 2.5 days. The detection of J suis in piglets with diarrhoea was reduced from 84% in the untreated piglets to 6% in the piglets given the prophylactic treatment.     

THE EFFECT ON FATTENING STEERS OF SUPPLEMENTING SILAGE WITH DRIED GRASS OR ROLLED BARLEY

Eighteen crossbred Aberdeen-Angus and six Shorthorn steers with an average liveweight of 382 kg were given silage (DM content 22.3%) ad lib., supplemented with 0, 1.2, 2.4 and 3.6 kg artificially dried grass, or 1.8 kg rolled barley, per day. A digestibility study carried out on the silage and dried grass showed that the concentration of the metabolizable energy was 52.7 and 45.6 kcal/100 kcal of food, respectively. Live-weight gain increased with each level of supplementation. Supplementation did not significantly affect the intake of silage DM, but differences in the intake of total DM were significant. The killing-out percentages of the steers were similar. The results suggest that dried grass pellets may be a usefid supplement for a silage diet. It was shown that 1.12 kg of dried grass was equivalent to 1.80 kg rolled barley as a supplement for silage.     

Effect of Different Manganese Concentrations during in vitro Maturation of Bovine Oocytes on DNA Integrity of Cumulus Cells and Subsequent Embryo Development

Manganese (Mn) is a trace element present in forages and cereals, and its concentration depends on soil status. Manganese deficiency in cattle, goats and ewes not only impairs oestrous cycle but reduces calf birth weight. The achievement of the first oestrus is delayed, and more attempts are necessary to obtain a successful conception. This study was conducted to investigate the effect of the availability of supplemental Mn during IVM on DNA damage of cumulus cells and total glutathione (GSH) content in oocytes and cumulus cells. The effect of supplementary Mn during IVM on subsequent embryo development was also studied. The results reported here indicate (i) DNA damage in cumulus cells decreased with 0, 2, 5 and 6 ng/ml Mn supplementation during IVM (p < 0.05). (ii) Intracellular GSH‐GSSG content increased (p < 0.01) with different Mn concentrations in oocytes and cumulus cells. Also, cumulus cell number per cumulus oocyte‐complexes (COC) did not differ either before or after IVM. (iii) Addition of Mn to maturation medium resulted in similar cleavage rates (p > 0.05) at 0, 2, 5 and 6 ng/ml Mn. However, subsequent embryo development to blastocyst stage was significantly higher (p < 0.01) in oocytes matured with 5 and 6 ng/ml Mn. (iv) There was also an increase (p < 0.05) in mean cell number per blastocyst obtained from oocytes matured with 5 and 6 ng/ml respect to zero Mn (IVM alone) and 2 ng/ml Mn. This study provides evidence that optimal embryo development to the blastocyst stage was partially dependent on the presence of Mn during IVM. Moreover, the availability of Mn during oocyte maturation ensures ‘normal’ intracellular GSH content in COCs and protects DNA integrity of cumulus cells.     

Distribution of prion protein genotypes in breeds of sheep in New Zealand

AIM: To use an established high through-put genotyping procedure to gain an estimate of the frequency of alleles of the prion protein (PrP) gene in some common sheep breeds in New Zealand.

METHODS: Using a genotyping procedure based on matrix-assisted laser desorption ionisation-time of flight (MALDI-TOF), DNA samples from 3,024 sheep from New Zealand, including breeds such as Romney, Texel, Coopworth, Merino and mixedbreed, were isolated, genotyped and the results analysed.

RESULTS: The 15 scrapie genotypes commonly reported, and derived from the five commonly reported allelic variants (ARR, ARQ, AHQ, ARH and VRQ), were all observed in the samples analysed. The estimates were indicative of the frequencies in the population of alleles present in breeds of sheep in New Zealand. There was a significant difference between the frequencies of alleles between breeds, but the ARQ, followed by the ARR allele, were, except in Carwell sheep, the most common alleles present.

CONCLUSION: This study gave an indication of the percentages of PrP gene alleles in sheep in New Zealand, including data previously unreported from breeds in this country. It is of interest because of the relatively large size of the sheep population in New Zealand compared with many countries, and it provides some useful information on the genetic susceptibility or resistance of the sheep population in New Zealand to scrapie. The frequencies of the alleles can be different for an individual breed compared between countries.