Lipid Metabolism, Carcass Characteristics and Longissimus dorsi Muscle Fatty Acid Composition of Tropical Crossbred Beef Cattle in Response to Desmanthus spp. Forage Backgrounding.

Lipid metabolism, carcass characteristics and fatty acid (FA) composition of the Longissimus dorsi (loin eye) muscle were evaluated in tropical crossbred steers backgrounded on Desmanthus spp. (desmanthus) with or without feedlot finishing. It was hypothesized that steers backgrounded on isonitrogenous diets augmented with incremental proportions of desmanthus will produce carcasses with similar characteristics and FA composition. Forty-eight Brahman, Charbray and Droughtmaster crossbred beef steers were backgrounded for 140 days on Rhodes grass (Chloris gayana) hay augmented with 0, 15, 30 or 45 percent desmanthus on dry matter basis. Lucerne (Medicago sativa) hay was added to the 0, 15 and 30 percent desmanthus diets to ensure that they were isonitrogenous with the 45 percent desmanthus diet. After backgrounding, the two heaviest steers in each pen were slaughtered and the rest were finished in the feedlot for 95 days before slaughter. Muscle biopsy samples were taken at the beginning and end of the backgrounding phase. Carcasses were sampled at slaughter for intramuscular fat (IMF) content, fat melting point (FMP) and FA composition analyses. Increasing the proportion of desmanthus in the diet led to a linear increase in docosanoic acid (p = 0.04) and omega-6/omega-3 polyunsaturated FA ratio (n-6/n-3 PUFA; p = 0.01), while docosahexaenoic acid decreased linearly (p = 0.01). Feedlot finishing increased hot carcass weight, subcutaneous fat depth at the P8 site and dressing percentage (p ≤ 0.04). The n-6/n-3 PUFA ratio was within the recommended < 5 for human diets. IMF was within the consumer-preferred ≥3% level for palatability. The hypothesis that steers backgrounded on isonitrogenous diets augmented with incremental proportions of desmanthus will produce similar carcass characteristics and FA composition was accepted. These findings indicate that a combination of tropical beef cattle backgrounding on desmanthus augmented forage and short-term feedlot finishing produces healthy and highly palatable meat.

Alkaline treatment for preventing acidosis in the rumen culture fermenting carbohydrates: An experimental study in vitro.

OBJECTIVE: The current research was carried out to evaluate the use of magnesium hydroxide as buffer to control acidosis in rumen culture fermenting carbohydrates in vitro. MATERIALS AND METHODS: The experiments were carried out in the chemostat system in which the reactor used was a 200 ml of working volume. A series of fed-batch trials were carried out in fed-batch system with hydraulic retention time of 4 days. All digesters were completely mixed with the rotation of 55 rpm, and the temperature was controlled at 39°C ± 0.5°C. RESULTS: Results showed that the supplementation of magnesium hydroxide (50 mM/day) to the corn starch feed (12.5 gm/l per day) for the rumen culture could prevent acidosis while at the same concentration of sodium bicarbonate addition to rumen culture, acidosis cannot be prevented in which lactic acid accumulated up to 200 mM. Supplementing magnesium hydroxide to the mixture of starch and sugar feeds prevented acidosis in which the major fermentation end product formed was acetate. A daily feeding with the ratio of 4.5:1 [starch: Mg(OH)2] was feasible to prevent rumen acidosis. CONCLUSION: Magnesium hydroxide added to the rumen culture could prevent lactic acid accumulation while sodium bicarbonate supplementation did not prevent acidosis and had lactic acid accumulation.

Prevalence of mastitis pathogens in South African pasture-based and total mixed ration-based dairies during 2008 and 2013.

Recent years have seen a change in the relative prevalence of environmental and contagious intramammary pathogens, as well as a change in the relative number of total mixed ration (TMR)-based and pasture (PAS)-based dairies in South Africa. The objectives of the study were to determine and compare the prevalence of mastitis pathogens in TMR and PAS dairies in South Africa during 2008 and 2013; furthermore, the within-herd prevalence of Streptococcus uberis in Str. uberis-positive herds was determined and compared. The prevalence of each pathogen, as well as the within-herd prevalence of Str. uberis, were compared between the two years and the two management systems using bacterial culture results from routinely collected composite cow milk samples submitted to the Onderstepoort Milk Laboratory, Faculty of Veterinary Science, University of Pretoria. Coagulase-negative staphylococci had the highest prevalence in both TMR and PAS dairies for both 2008 (29.60% [95.00% CI: 28.80% - 30.40%] and 26.90% [95.00% CI: 25.50% - 28.30%], respectively) and 2013 (20.20% [95.00% CI: 19.30% - 21.10%] and 22.70% [95.00% CI: 22.20% - 23.10%], respectively), which decreased significantly from 2008 to 2013 in both TMR and PAS dairies (p < 0.001). Streptococcus uberis showed an increase in prevalence in both TMR (p = 0.002) and PAS dairies (p = 0.001) from 2008 (2.36% [95.00% CI: 2.10% - 2.65%] and 2.63% [95.00% CI: 2.16% - 3.16%], respectively) to 2013 (3.10% [95.00% CI: 2.72% - 3.51%] and 3.64% [95.00% CI: 3.45% - 3.83%], respectively). Staphylococcus aureusshowed a significant decrease in both TMR (p = 0.011) and PAS (p < 0.001) dairies from 2008 (4.71% [95.00% CI: 4.34% - 5.10%] and 5.62% [95.00% CI: 4.94% - 6.36%], respectively) to 2013 (3.95% [95.00% CI: 3.52% - 4.40%] and 1.71% [95.00% CI: 1.58% - 1.84%], respectively). The median within-herd prevalence of Str. uberis for the combined dairy systems showed a significant increase from 2008 (1.72% [IQR: 0.88% - 5.00%]) to 2013 (3.10% [IQR: 1.72% - 4.70%]) (p < 0.001). Statistically significant differences were found in the prevalence of most of the major contagious and environmental mastitis pathogens between 2008 and 2013 and between TMR and PAS dairies. The within-herd prevalence of Str. uberis increased from 2008 to 2013, with the highest within-herd prevalence in PAS dairies in 2013.

First report of Cryptosporidium parvum in a dromedary camel calf from Western Australia.

Cryptosporidium is an important enteric parasite that can contribute large numbers of infectious oocysts to drinking water catchments. As a result of its resistance to disinfectants including chlorine, it has been responsible for numerous waterborne outbreaks of gastroenteritis. Wildlife and livestock play an important role in the transmission of Cryptosporidium in the environment. Studies conducted outside Australia have indicated that camels may also play a role in the transmission of zoonotic species of Cryptosporidium. Despite Australia being home to the world's largest camel herd, nothing is known about the prevalence and species of Cryptosporidium infecting camels in this country. In the present study, C. parvum was identified by PCR amplification and sequencing of a formalin-fixed intestinal tissue specimen from a one-week old dromedary camel (Camelus dromedarius). Subtyping analysis at the glycoprotein 60 (gp60) locus identified C. parvum subtype IIaA17G2R1, which is a common zoonotic subtype reported in humans and animals worldwide. Histopathological findings also confirmed the presence of large numbers of variably-sized (1-3 µm in diameter) circular basophilic protozoa - consistent with Cryptosporidium spp.- adherent to the mucosal surface and occasionally free within the lumen. Further analysis of the prevalence and species of Cryptosporidium in camel populations across Australia are essential to better understand their potential for contamination of drinking water catchments.

Optimum Drug Combinations for the Sedation of Growing Boars Prior to Castration.

Juvenile male pigs were sedated for castration. Eight five-month old boars were sedated twice (two weeks apart) with a combination of detomidine (0.1 mg/kg), midazolam (0.2 mg/kg) and either butorphanol (0.2 mg/kg) (Group MDB, n = 8) or morphine (0.2 mg/kg) (Group MDM, n = 8) intramuscularly. The boars were positioned in lateral recumbency and lidocaine (200 mg total) was injected into the testicle and scrotal skin. Castration of a single testicle was performed on two occasions. Sedation and reaction (to positioning and surgery) scores, pulse rate, respiratory rate, haemoglobin oxygen saturation, body temperature, arterial blood gas parameters and the times to immobility and then recovery were recorded. Atipamezole was administered if spontaneous recovery was not evident within 60 min of sedative administration. Data were compared with either a paired-sample t-test or a Wilcoxon-Signed Rank Test. There was no difference in sedation score, body temperature, respiratory rate and haemoglobin oxygen saturation between MDB and MDM. Mild hypoxaemia was noted in both groups. There was less reaction to castration after MDB. The pulse rate was higher after MDM sedation. The times to immobility and then recovery were similar. The combination of MDB provided more reliable sedation than MDM. MDB may be useful for sedation for short procedures in pigs, though oxygen supplementation is recommended to avoid hypoxaemia.