Effects of Saccharomyces cerevisiae supplementation on ruminal parameters, nutrient digestibility and growth in sheep: A meta-analysis

The role of olive leaves and saccharomyces cerevisiae supplementation in enhancing the performance and economic feasibility of fattening lambs

Objectives were to assess the use of olive leaves (OL) to replace wheat straw, the forage source, and the supplementation of Saccharomyces cerevisiae (SC) on nutritional intake, growth performance, blood parameters, and carcass quality in lambs. A total of twenty-one newly weaned Awassi lambs, weighing an average of 19 ± 0.6 kg, were randomly distributed to three groups. These three diets were: CON: 0% OL control diet; OL diet of 25%; and OL plus 0.4 g SC/head/d (OLSC) diet of 25% of dietary dry matter (DM). The first seven days were devoted to adaptation and the next sixty days were devoted to gathering data. Daily records of nutrient intake were made. On the 49th day of data collection, four animals were randomly selected from each group and kept in individual metabolism cages (1.0 × 0.8 m) with slatted mash for eight days (four days for data collection and four days for cage adaptation) to evaluate N balance and nutrient digestibility. All lambs were slaughtered after the study to assess the quality of the meat and the carcass features. No difference in DM consumption (P > 0.05) between the treatment groups. When OL-containing diets were compared to the CON diet, the consumption of acid detergent fiber and neutral detergent fiber (NDF) was lower (P ≤ 0.0002), whereas metabolizable energy and ether extract were higher (P < 0.0001). While the OL diet was intermediate, the final BW, total gain, and average daily gain for the OLSC diet tended to be higher (P < 0.087) than the CON diet. Lambs fed the OL-containing diets had a lower (P = 0.0020) cost of growth ($US/kg) than lambs in the CON group. All other nutrient digestibilities were comparable between the treatment diets, except NDF digestibility, which was greater (P = 0.045) in the OLSC group than in the CON group. The N balance variables showed a similarity between the various diets (P > 0.05). Lambs fed the OLSC diet tended to have higher weights (P ≤ 0.098) for fasting live weight, hot carcass weight, carcass cuts weights, and cold carcass weight than lambs on the CON diet. The OLSC diet resulted in higher (P < 0.025) loin weight and intermuscular fat in comparison to the CON and OL diets. No difference (P ≥ 0.05) in the dissected tissues between diets. The longissimus dorsi muscle's dimensions and physicochemical characteristics did not alter (P > 0.05) across the treatment diets. In comparison to the CON and OL diets, the OLSC diet resulted in higher serum glucose levels (P = 0.044). Nonetheless, there were similarities (P ≥ 0.05) in various serum blood parameters between the treatment diets. In conclusion, using OL or/and supplemented SC is positively associated with nutrient intake, growth performance, some carcass parameters, and loin cut tissue, and the most effective aspect is decreasing production cost ($US/kg gain), which makes it a good solution to pass inflation feedstuff prices and cover animal needs.

Yeast Products Mediated Ruminal Subenvironmental Microbiota, and Abnormal Metabolites and Digestive Enzymes Regulated Rumen Fermentation Function in Sheep

Yeast products (YP) are commonly used as rumen regulators, but their mechanisms of action are still unclear. Based on our previous studies, we questioned whether yeast products would have an impact on rumen solid-associated (SA) and liquid-associated (LA) microorganisms and alter rumen fermentation patterns. Thirty 3-month-old male sheep weighing 19.27 ± 0.45 kg were selected and randomized into three groups for 60 days: (1) basal diet group (CON group), (2) basal diet add 20 g YP per day (low YP, LYP group) and (3) basal diet add 40 g YP per day (high YP, HYP group). The results demonstrated that the addition of YP increased rumen cellulase activity, butyrate and total volatile fatty acid (TVFA) concentrations (p < 0.05), while it decreased rumen amylase activity and abnormal metabolites, such as lactate, lipopolysaccharides (LPS) and histamine (HIS) (p < 0.05). Metagenomic analysis of rumen microorganisms in three groups revealed that YP mainly influenced the microbial profiles of the SA system. YP increased the relative abundance of R. flavefaciens and decreased methanogens in the SA system (p < 0.05). With the addition of YP, the abundance of only a few lactate-producing bacteria increased in the SA system, including Streptococcus and Lactobacillus (p < 0.05). However, almost all lactate-utilizing bacteria increased in the LA system, including Megasphaera, Selenomonas, Fusobacterium and Veillonella (p < 0.05). In addition, YP increased the abundance of certain GHs family members, including GH43 and GH98 (p < 0.05), but decreased the abundance of some KEGG metabolic pathways involved in starch and sucrose metabolism, biosynthesis of antibiotics and purine metabolism, among others. In conclusion, the addition of YP to high-concentrate diets can change the abundance of major functional microbiota in the rumen, especially in the solid fraction, which in turn affects rumen fermentation patterns and improves rumen digestibility.

Influence of yeast on rumen fermentation, growth performance and quality of products in ruminants: A review

This review aims to give an overview of the efficacy of yeast supplementation on growth performance, rumen pH, rumen microbiota, and their relationship to meat and milk quality in ruminants. The practice of feeding high grain diets to ruminants in an effort to increase growth rate and weight gain usually results in excess deposition of saturated fatty acids in animal products and increased incidence of rumen acidosis. The supplementation of yeast at the right dose and viability level could counteract the acidotic effects of these high grain diets in the rumen and positively modify the fatty acid composition of animal products. Yeast exerts its actions by competing with lactate-producing (Streptococcus bovis and Lactobacillus) bacteria for available sugar and encouraging the growth of lactate-utilising bacteria (Megasphaera elsdenii). M. elsdenii is known to convert lactate into butyrate and propionate leading to a decrease in the accumulation of lactate thereby resulting in higher rumen pH. Interestingly, this creates a conducive environment for the proliferation of vaccenic acid-producing bacteria (Butyrivibrio fibrisolvens) and ciliate protozoa, both of which have been reported to increase the ruminal concentration of trans-11 and cis-9, trans-11-conjugated linoleic acid (CLA) at a pH range between 5.6 and 6.3. The addition of yeast into the diet of ruminants has also been reported to positively modify rumen biohydrogenation pathway to synthesise more of the beneficial biohydrogenation intermediates (trans -11 and cis -9, trans -11). This implies that more dietary sources of linoleic acid, linolenic acid, and oleic acid along with beneficial biohydrogenation intermediates (cis-9, trans-11-CLA, and trans-11) would escape complete biohydrogenation in the rumen to be absorbed into milk and meat. However, further studies are required to substantiate our claim. Therefore, techniques like transcriptomics should be employed to identify the mRNA transcript expression levels of genes like stearoyl-CoA desaturase, fatty acid synthase, and elongase of very long chain fatty acids 6 in the muscle. Different strains of yeast need to be tested at different doses and viability levels on the fatty acid profile of animal products as well as its vaccenic acid and rumenic acid composition.

Effects of inclusion of corn gluten feed in dairy rations on dry matter intake, milk yield, milk components, and ruminal fermentation parameters: a meta-analysis

Corn gluten feed (CGF) is a co-product of wet milling that can replace energy or fiber ingredients in dairy cow rations. The present meta-analysis examines how inclusion of CGF can affect dry matter intake (DMI), milk yield (MY), milk components, and ruminal fermentation parameters. A literature search was conducted to identify papers published from 1990 to 2018. Effect size for all parameters was calculated as standardized mean difference with a 95% confidence interval. Heterogeneity was determined using Q test and I² statistic, while meta-regression was used to examine factors influencing heterogeneity. Results indicate that feeding CGF increased the effect size for DMI and MY. No differences were observed for effect size for percentage milk fat or protein; however, increases were observed in the effect size for milk fat yield, milk protein yield, milk lactose percentage, and milk lactose yield. Ruminal fermentation parameters revealed a decrease in the effect size for pH and acetate and an increase for propionate. No differences were observed in the effect size for total VFA or butyrate. The Q test demonstrated heterogeneity (P < 0.1) for MY, MFP, and pH. The results indicate differences in forage intake between groups receiving CGF and control as an important factor contributing to heterogeneity for DMI, MFP, and pH. It can be concluded from this meta-analysis that in addition to increased DMI, inclusion of CGF in cow diets increases MY and improves milk components. Furthermore, inclusion of CGF in the diet lowers ruminal pH while decreasing acetate and increasing propionate contents.