Plant extracts have been used over time in traditional medicine, mainly for their antimicrobial activity as well as for their medicinal effects. Plant-derived products contain secondary metabolites that prevent pathogenic microbial growth similar to conventional medicines. These secondary metabolites can enhance animal health and production in a more natural or organic manner and may contribute to the reduction in the use of pharmacological drugs in animal feed, which is of great concern for emerging microbial resistance. Plant secondary metabolites can be cost effective, while improving the production efficiency of ruminants, non-ruminants, and aquatic food animals. Among the plant-derived products is the Yucca schidigera extract (YSE), containing steroidal saponins as their main active component. YSE has multiple biological effects, including inhibition of some pathogenic bacteria, protozoa, and nematodes. YSE is used to control odor and ammonia and consistently enhance poultry production by enhancing intestinal health and function. In pigs, results are as yet inconclusive. In ruminants, YSE works against protozoa, has selective action against bacteria, and reduces the archaea populations; all these effects are reflected in the reduction in emissions of polluting gases, mainly methane, although the effects are not observed in all feeding conditions. These effects of YSE are discussed in this review. YSE has potential as a natural feed additive for sustainable animal production while contributing to the mitigation of contaminant gas emissions.

Conjugated linoleic acid (CLA), has been shown to have protective effects against various diseases, such as obesity, arteriosclerosis, diabetes, chronic inflammatory diseases, and cancer. This fatty acid in ruminants results from two processes, biohydrogenation, which takes place in the rumen, and de novo synthesis, carried out in the mammary gland, and it has linoleic and α-linolenic acids as its precursors. The amounts of precursors in the diets of animals are related to the amounts of CLA in milk. In the literature review, it was found that the milk of cows fed fresh forage has a higher amount of CLA because they have a higher amount of linoleic acid and α-linolenic acid compared to other foods used in the diets of cows. The amount of CLA precursors in pastures can be increased through agronomic practices, such as nitrogen fertilization, and regrowth age. It is also a technique used to increase the amount of CLA in milk to obtain a greater benefit regarding its nutritional value.

<![CDATA[This study was undertaken to evaluate the influence of daily pasture allowance and concentrate supplementation on dairy cows during autumn. The study lasted 56 days using 30 Holstein Friesian cows. The treatments resulted from a combination of two pasture allowances (L = low allowance, 20 and H = high allowance, 30 kg of DM cow-1 day-1, measured at ground level) and three concentrate levels (0, 3 or 6 kg cow-1 day-1). All the cows received 4.5 kg cow-1 day-1 of grass silage. The increase in pasture allowance had no effect on milk production (P > 0.05), but increased the protein concentration in milk (from 3.02% to 3.21%) (P < 0.05), body weight gain (0.336 to -0.121 kg) and the grazing time (299 min cow-1 day-1 to 411 min cow-1 day-1) (P < 0.001). Concentrate supplementation increased milk production (15.1, 19.2 and 21.7 kg cow-1 day-1) (P < 0,001), fat yield (+0.1 kg cow-1 day-1) and protein yield (+0.1 kg cow-1 day-1), decreasing milk urea (-0.25 mmol/L-1 day-1), (P < 0.001). Increasing pasture allowance or the concentrate offered had effect on NEFA and plasma urea-N concentration during the experiment. High pasture allowance increased (P < 0.05) purine derivatives excretion and PDPD/CT ratio, but not effect was observed by concentrate supplementation. Supplementation with concentrate had a positive impact on performance as a result of a better protein-energy balance of the diet.]]>