A comparative study on the occurrence, genetic characteristics, and factors associated with the distribution of Listeria species on cattle farms and beef abattoirs in Gauteng Province, South Africa.

These cross-sectional studies reported the occurrence, genetic characteristics, and factors associated with the distribution of Listeria species on cattle farms and beef abattoirs in Gauteng Province, South Africa. A total of 328 samples (faeces, feeds, silage, and drinking water) were collected from 23 cattle farms (communal, cow-calf, and feedlot), and 262 samples (faeces, carcass swabs, and effluents) from 8 beef abattoirs (low throughput and high throughput) were processed using standard bacteriological and molecular methods to detect Listeria species. The factors associated with the prevalence of Listeria species were investigated, and multiplex polymerase chain reaction (mPCR) was used to determine Listeria species, the pathogenic serogroups, and the carriage of eight virulence-associated genes by Listeria monocytogenes. The overall prevalence of Listeria species in cattle farms was 14.6%, comprising Listeria innocua (11.3%), Listeria monocytogenes (3.4%), Listeria welshimeri (0.0%) compared with 11.1%, comprising Listeria innocua (5.7%), Listeria monocytogenes (4.6%), Listeria welshimeri (0.8%) for beef abattoirs. Of the three variables (area, type of farm/abattoir, and sample type) investigated, only the sample types at abattoirs had a significant (P < 0.001) effect on the prevalence of L. innocua and L. welshimeri. The frequency of distribution of the serogroups based on 11 L. monocytogenes isolated from farms was 72.7% and 27.3% for the serogroup 1/2a-3a and 4b-4d-4e, respectively, while for the 12 L. monocytogenes isolates recovered from abattoirs, it was 25%, 8.3%, 50% and 16.7% for the serogroup 1/2a-3a, 1/2b-3b, 1/2c-3c, and 4b-4d-4e respectively (P < 0.05). All (100%) isolates of L. monocytogenes from the farms and abattoirs were positive for seven virulence genes (hlyA, inlB, plcA, iap, inlA, inlC, and inlJ). The clinical and food safety significance of the findings cannot be ignored.

Oocyte quality and viability in Nguni and Hereford cows exposed to different levels of dietary protein.

High blood urea nitrogen (BUN) concentration decreases fertility in ruminants. Nguni cattle are reported to maintain BUN concentration more efficiently than other beef breeds. Our objectives were to determine if BUN concentration differed between Nguni and Hereford cows exposed to a high protein ration, and if breed or BUN and serum protein concentrations at the time of oocyte pick-up affected oocyte quantity, quality, and viability. Twelve Nguni and 10 Hereford cows were randomized into high or normal BUN-inducing diets in a crossover design. Ultrasound-guided oocyte pick-up was performed twice weekly; oocytes were counted, visually graded and the viable oocytes were pooled by treatment and breed for in vitro maturation, fertilization, and culture. Nguni cows on the highest protein ration achieved lower mean BUN concentration than Herefords (P < 0.05), and Nguni cows reached BUN concentrations above 20 mg/dL less frequently than Herefords (P = 0.03). Donor BUN concentration above 20 mg/dL at the time of oocyte pick-up, but not breed, independently decreased the number of good quality oocytes harvested. Increasing weighted mean serum albumin of donor cows was independently associated with the number of oocytes that cleaved by day 2 and that reached morula stage by day 7 (P = 0.01). In conclusion, Nguni cows reached the critical threshold of 20 mg/dL BUN less frequently than Herefords; BUN of donor cows above 20 mg/dL negatively affected visual oocyte quality independent of breed, and increasing serum albumin of donor cows improved viability of bovine oocytes.