Over the years, the use of management and feeding strategies to enhance pig productivity while minimizing the use of antibiotic growth promoters has grown. Antibiotic growth promoters have been widely used as feed additives to reduce diet-related stress and improve pig performance. However, increasing concern about the consequences of long-term and increased use of antibiotic growth promoters in animal production has led to a paradigm shift towards the use of natural organic alternatives such as plant essential oils and organic acids in pig nutrition to enhance growth. Antibiotic growth promoters endanger human health by allowing multidrug-resistant genes to be transferred horizontally from non-pathogenic to pathogenic bacteria, as well as directly between animals and humans. Scientific research shows that alternative growth promoters such as essential oils and organic acids appear to improve pigs’ ability to prevent pathogenic bacteria from colonizing the intestinal system, stabilizing the gut microflora and promoting eubiosis, as well as improving immunity and antioxidant stability. The purpose of this review was to provide an in-depth review of organic acids and essential oils as growth promoters in pig production, as well as their effects on productivity and meat quality. Organic acids and essential oils in pig diets are a safe way to improve pig performance and welfare while producing antibiotic-free pork.

The investigation into the complementary roles of essential oils (EOs) and organic acids in enhancing rumen physiology is increasingly gaining recognition within the field of animal nutrition. Essential oils are known for their antimicrobial effects, which can specifically target certain microbial populations in the rumen, thereby impacting fermentation processes, methane output, and nutrient digestion. In addition, the integration of organic acids plays a crucial role in stabilizing rumen pH and steering the metabolic activities of bacterial populations toward propionate production, a process essential for energy metabolism in ruminants. The concurrent use of essential oils and organic acids may yield synergistic benefits that could further optimize ruminal fermentation efficiency, enhance feed conversion rates, and lower methane emissions. This systematic review used the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The literature search was meticulously designed to encompass parameters related to ruminant species, feed additives, essential oils, organic acids, synergistic effects, and rumen physiology. The efficacy of both organic acids and essential oils is highly dependent on their concentration and the specific combinations utilized. When certain essential oils are used in conjunction with selected organic acids, they may mitigate any potential negative effects on fermentation, thereby fostering a more favorable environment for the proliferation of beneficial microbial communities. Understanding the relationship between essential oils and organic acids is essential for the formulation of diets that enhance rumen health while concurrently reducing environmental pressures through diminished methane emissions. Future research should prioritize long-term in vivo investigations to gain more comprehensive insights into the interactions among these dietary components and identify the optimal combinations for ruminant feeding strategies.

The study investigated the effects of partially replacing soybean meal with fermented water hyacinth meal (FWHM) on oviduct morphometry and egg quality in Hy-Line hens. Ninety-six eighteen-week-old hens were randomly assigned to one of three dietary treatments: 0% (Control), 2.5%, or 5% FWHM. Following a 2-week dietary adaption period, hens were fed the experimental diets for twelve weeks. Internal egg quality, and eggshell traits were measured at regular intervals during the feeding trial, with freshly laid eggs stored at 4°C (39.2°F) under approximately 70-80% relative humidity and equilibrated at room temperature (21-25°C) for one hour prior to analysis to minimize condensation and thermal shock effects. Oviduct morphometric measurements were obtained at the end of the study, to evaluate dietary effects. Most oviduct morphometric parameters were unaffected by FWHM supplementation (P > 0.05). Notable exceptions were higher infundibulum weight in the 5% FWHM group (1.65 ± 0.46 g) compared to the 2.5% group (1.10 + 0.34 g; P < 0.05), and lower magnum weight in the 5% FWHM group (27.84 ± 7.24 g) relative to Control (38.28 ± 7.01 g; P < 0.05). Internal egg quality and eggshell characteristic traits: yolk and albumen weights, Haugh unit and eggshell thickness were largely unchanged. Yolk pH was lower in the 2.5% (6.63 ± 0.09) and 5% (6.60 ± 0.10) FWHM groups versus Control (6.70 ± 0.13; P < 0.05), while yolk diameter slightly decreased in FWHM-fed hens. These findings indicate that FWHM can be included in laying hen diets at levels up to 5% without adversely effecting reproductive tract development or core egg quality, while modulating yolk traits that may enhance egg shelf life.

The study assessed the apparent digestibility, nitrogen retention, and microbial protein production in goats fed a Macadamia oil cake-based diet. Sixteen mixed breed bucks about 34 kg and age ranging from18 to 24 months old, were randomly allocated to four dietary treatments of 0, 100, 150, and 200 g/kg macadamia oil cake in a complete randomised design and each goat was considered an experimental unit. Faecal digestibility and nitrogen balance were assessed through total faecal and urine collection. Microbial protein production was estimated using urinary purine derivatives allantoin method. The study lasted 21 days, with 14 days for acclimatization and 7 days for sample collection. Data were analysed using one way analysis of variance, through General Linear Models procedures. Treatment means were compared using Tukey's post-hoc test. Macadamia oil cake inclusion did not affect dry matter, organic matter, or crude protein intake. There were no differences in nitrogen retention and the apparent digestibility of dry matter, crude protein, neutral detergent fibre, and acid detergent fibre. Positive nitrogen retention was observed across treatments. Microbial protein yield increased with more than 10% macadamia oil cake supplementation. The findings supported its use as an alternative protein source in goat diets. Further research is recommended to determine the optimal dietary inclusion.