Seasonality and species are key aspects of the abiotic and biotic environment, respectively, that influence nutrient, phytochemical and antioxidant profiles of invasive alien plants leaf-meals. The current study investigated the effects of season on nutrient, amino acid, fatty acid, mineral, bioactive polyphenolic composition and antioxidant activity of Acacia mearnsii and A. dealbata leaf-meals. Overall, A. mearnsii leaf-meal harvested in the hot-dry-season had greater crude protein, ether extract, neutral detergent soluble fibre, 24 and 48 h in vitro neutral detergent fibre digestibility, macro-mineral contents, individual polyphenols, C18:1n9 and C18:2n6 compared to other leaf-meals. Regardless of the season, A. mearnsii leaf-meals had greater amino acid concentrations than A. dealbata leaf-meals. Hot-dry-season leaf-meals had a greater concentration of total flavonoids than the leaf-meals in the cool-wet-season irrespective of species. Antioxidant potency composite of the Acacia leaf-meals was in the order of A. dealbata × hot-dry-season > A. mearnsii × hot-dry-season > A. mearnsii × cool-wet-season > A. dealbata × cool-wet-season. The findings suggested that A. mearnsii leaf-meal harvested in the hot-dry-season has superior nutritional and polyphenolic profiles, which could support its use as a nutraceutical and preservative for the enhancement of ruminant production and product quality compared to other leaf meals.

The high mortality rate associated with human infections caused by Escherichia coli strains of the serotype O157:H7 has brought to public attention the importance of ruminants as reservoirs of food-borne pathogens. In addition to established examples such as salmonella, campylobacter and listeria, recent evidence is emerging of the role of food in the transmission of Helicobacter pylori and Mycobacterium paratuberculosis. Food-borne pathogens harboured by ruminants are spread through shedding in the faeces and subsequent faecal contamination of raw food. Ruminant shedding appears to be affected by diet and, of particular concern, may be increased during fasting regimens imposed during transport to the slaughterhouse. The survival of food-borne pathogens in the ruminant gut is affected by many factors including microbe–microbe interactions, interactions involving plant metabolites and the presence of inhibitory end-product metabolites such as short-chain fatty acids. The potential importance of digesta flow and bacterial detachment in shedding of food-borne pathogens is discussed. Experimental procedures with dangerous pathogens have constraints, particularly in animal experimentation. This situation may be overcome by the use of rumen-simulating fermentors. One such system which, like the natural rumen, has a different turnover rate for solid and liquid digesta, was found to maintain rumen-like variables over an 11 d period. This system may prove useful for the study of dietary effects on food-borne pathogens.