Glycerine as a feed supplement for beef and dairy cattle: A meta-analysis on performance, rumen fermentation, blood metabolites and product characteristics

This study aimed to comprehensively evaluate the effects of glycerine supplementation at various concentrations on performance, rumen fermentation, blood metabolites and product characteristics of beef and dairy cattle in vivo by using a quantitative meta-analysis approach. Meta-analysis was performed by integrating a total of 52 studies from 39 articles and 182 treatments into a database. Data were constructed into an intact database and did not distinguish between beef and dairy cattle, except for the parameters of production performance and product characteristics. Data summarized were analysed by using a statistical meta-analysis that employed a fixed effect of glycerine supplementation level and a random effect of various studies for both beef and dairy cattle. Significance of an effect was stated at the probability level of p < .05, and p < .1 was considered as a tendency of significant. Results revealed that there was a linear decrease on dry matter intake (p < .01) and daily gain (p < .05) of beef cattle with the increasing levels of glycerine supplementation. Glycerine supplementation did not decrease milk production of lactating dairy cows. Molar proportion of acetate in the rumen was decreased (p < .001), whereas propionate and butyrate proportions were increased (both at p < .001) by glycerine supplementation. Generally, glycerine did not change nutrient digestibility except that it reduced fibre digestibility (p < .001). Glycerine supplementation linearly lowered triglyceride and NEFA concentrations (both at p < .05) in the blood serum, but not other blood metabolites. Glycerine tended to linearly increase (p < .1) carcass percentage in beef cattle. Increasing dietary glycerine levels decreased milk fat (p < .01) but elevated milk protein (p < .001). Glycerine tended to increase milk lactose (p < .1) by following a quadratic pattern. The proportion of MUFA was increased quadratically by glycerine supplementation (p < .05), whereas glycerine tended to decrease SFA by following a quadratic pattern (p < .1).

Effect of glycerol feed-supplementation on seabass metabolism and gut microbiota

Dietary glycerol supplementation in aquaculture feed is seen as an alternative and inexpensive way to fuel fish metabolism, attenuate metabolic utilization of dietary proteins and, subsequently, reduce nitrogen excretion. In this study, we evaluated the impact of dietary glycerol supplementation on nitrogen excretion of European seabass (Dicentrarchus labrax) and its effects on metabolite profile and bacterial community composition of gut digesta. These effects were evaluated in a 60-day trial with fish fed diets supplemented with 2.5% or 5% (w/w) refined glycerol and without glycerol supplementation. Nuclear magnetic resonance spectroscopy and high-throughput 16S rRNA gene sequencing were used to characterize the effects of glycerol supplementation on digesta metabolite and bacterial community composition of 6-h postprandial fish. Our results showed that ammonia excretion was not altered by dietary glycerol supplementation, and the highest glycerol dosage was associated with significant increases in amino acids and a decrease of ergogenic creatine in digesta metabolome. Concomitantly, significant decreases in putative amino acid degradation pathways were detected in the predicted metagenome analysis, suggesting a metabolic shift. Taxon-specific analysis revealed significant increases in abundance of some specific genera (e.g., Burkholderia and Vibrio) and bacterial diversity. Overall, our results indicate glycerol supplementation may decrease amino acid catabolism without adversely affecting fish gut bacterial communities.Key points• Glycerol can be an inexpensive and energetic alternative in fish feed formulations.• Glycerol did not affect nitrogen excretion and gut bacteriome composition.• Glycerol reduced uptake of amino acids and increased uptake of ergogenic creatine.• Glycerol reduced putative amino acid degradation pathways in predicted metagenome.

Effect of glycerin supplementation on the expression of antioxidant and mitochondrial genes in broilers

Crude glycerin has been used as an alternative energy source in animal feeding and can thus change both the animal’s performance and the levels of gene expression related to energy production process and the antioxidant system, since the effect of glycerin depends on its degree of purity in the diet. The aim of this study was to evaluate the effect of crude glycerin inclusion (0, 6 and 12%) in the diet has on performance characteristics and mRNA abundance of genes associated with the mitochondrial function (uncoupling protein (UCP), cytochrome C oxidase subunit III (COX III) and adenine nucleotide transporter (ANT)) and those that combat the reactive oxygen species (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx)) in the liver and muscle of broilers at 42 days of age. Total RNA was extracted from the tissues, and cDNA was amplified using specific primers for the genes under study through real-time reverse transcription polymerase chain reaction; the endogenous gene used was β-actin. There was no difference between glycerin concentrations for weight gain, feed intake or feed conversion. Greater expression of UCP at muscle and higher GPx expression at liver were observed in broilers fed 12% glycerin. In conclusion, the addition of 12% glycerin to broiler diets increased the expression of UCP and GPx, but did not change broiler performance. Therefore, glycerin can be used as an alternative ingredient without losses.

Using different levels of glycerine, glucose, or sucrose in broiler starter diets to overcome negative effects of delayed feed access on growth performance

Two trials were conducted to evaluate the inclusion of glycerine, glucose, or sucrose in broiler starter diets to overcome negative effects of delayed feed access. In trial 1, 2160 newly hatched chicks (mixed sexed) were randomly assigned to two feeding programs (immediate vs. 36 h delayed feed access). Nine starter diets prepared with crude glycerine, glucose, or sucrose fed at 0%, 4%, or 8% levels were fed during the first 14 d post hatch (PH). In trial 2, 720 male and 720 female newly hatched chicks were randomly assigned to two feeding programs (immediate vs. 48 h delayed feed access). Starter diets fed during the first 14 d of feed access, consisted of a control, 8% glycerine, or 8% glucose. In both trials, a common grower and finisher diet were fed during days 14–24 and 25–35, respectively. Body weight and feed consumed were measured on 7, 14, 24, and 35 d. In trial 1, all 8% diet-fed birds were heavier compared with the control on day 35 PH (2259 vs. 2198 g, P < 0.01). Birds fed glycerine starter diets had improved feed conversion ratio (FCR) during 22–35 d (P < 0.01). In trial 2, glycerine diet resulted in heavier birds after 35 d of feed access, compared with birds fed control and glucose diets immediately after hatch (2373 vs. 2276 g, P < 0.01). Dietary inclusion of 8% glycerine can assist newly hatched broiler chicks to overcome delayed feed access induced growth suppression.

The effect of replacing soya bean oil with glycerol in diets on performance, egg quality and egg fatty acid composition in laying hens

The objective of this experiment was to replace soya bean oil with glycerol in laying hen diets and assess the change's effect on performance, parameters of egg quality and the egg fatty acid profile. A total of 60 44-week-old Hy-Line W36 laying hens were distributed according to a completely randomised experimental design into four treatments consisting of glycerol substitutions for soya bean oil dietary at varying inclusion levels (0%, 25%, 50% and 75%), with five replicates of three birds each. Dietary treatments had no significant effect on BW change, egg production, feed intake, feed conversion ratio, egg weight and egg mass of laying hens. The inclusion of glycerol in the diet of laying hens had no significant effect on egg specific gravity, eggshell breaking strength, eggshell weight, eggshell thickness, egg shape index, albumen index, yolk index, haugh unit, albumen pH, yolk pH and egg yolk colour values. The inclusion of glycerol in the diet of laying hens had no significant effect on palmitic, palmitoleic, stearic, oleic and linolenic acid contents of the egg yolk. The linoleic acid and polyunsaturated fatty acid contents of the egg yolk significantly decreased with the higher levels of dietary glycerol supplementation (P<0.05). The results of this study show that it is possible to replace 75% of soya bean oil (4.5% in diet) with glycerol.

Effects of dietary glycerin inclusion at 0, 5, 10, and 15 percent of dry matter on energy metabolism and nutrient balance in finishing beef steers

Expansion of the biodiesel industry has increased the glycerin (GLY) supply. Glycerin is an energy-dense feed that can be used in ruminant species; however, the energy value of GLY is not known. Therefore, the effects of GLY inclusion at 0, 5, 10, and 15% on energy balance in finishing cattle diets were evaluated in 8 steers (BW = 503 kg) using a replicated Latin square design. Data were analyzed with the fixed effects of dietary treatment and period, and the random effects of square and steer within square were included in the model. Contrast statements were used to separate linear and quadratic effects of GLY inclusion. Glycerin replaced dry-rolled corn (DRC) at 0, 5, 10, and 15% of dietary DM. Dry matter intake decreased linearly (P = 0.02) as GLY increased in the diet. As a proportion of GE intake, fecal energy loss tended to decrease linearly (P < 0.07), and DE also tended to increase linearly (P = 0.07) as dietary level of GLY increased. Urinary energy loss was not different (P > 0.31) as a proportion of GE as GLY increased in the diet. Methane energy loss as a proportion of GE intake tended to respond quadratically (P = 0.10), decreasing from 0 to 10% GLY inclusion and increasing thereafter. As a proportion of GE intake, ME tended to respond quadratically (P = 0.10), increasing from 0 to 10% GLY and then decreasing. As a proportion of GE intake, heat production increased linearly (P = 0.02) as GLY increased in the diet. Additionally, as a proportion of GE intake, retained energy (RE) tended to respond quadratically (P = 0.07), increasing from 0 to 10% GLY inclusion and decreasing thereafter. As a proportion of N intake, urinary and fecal N excretion increased linearly (P < 0.04) as GLY increased in the diet. Furthermore, grams of N retained and N retained as a percent of N intake both decreased linearly (P < 0.02) as GLY increased in the diet. Total DM digestibility tended (P < 0.10) to respond quadratically, increasing at a decreasing rate from 0 to 5% GLY inclusion. Overall, RE tended to decrease as GLY increased in the diet in conjunction with a decrease in N retention, which could indicate an increased metabolic cost to the animal associated with feeding GLY. Based on RE, the feeding value of GLY in high-concentrate diets is greater than DRC at 5 and 10% of DM but less at 15% of DM.

The energy value of biodiesel glycerine products fed to broilers at different ages

The objective of this study was to determine the apparent metabolisable energy corrected for nitrogen balance (AMEn) of some products containing glycerine from soybean oil (GOIL), a mixture of frying oil and lard (GMIX) and a semi-purified process (GSP) in broilers of different ages (10, 20, 30 and 40 days post-hatching), using two methodologies. In trial 1, the basal diets were replaced with 100 g/kg of each studied glycerine product and the diets were supplied ad libitum. Three hundred broilers were used in five replicates, with five, four, three and three animals per cage in each age group, respectively. The AMEn was calculated for each experimental unit. In trial 2, dietary treatments included the addition of glycerine at 0, 40, 80 or 120 g/kg for each crude glycerine product, with 900 broilers in six replicates, using the same number of animals per cage as described in trial 1. Depending on the experimental unit, the feeding was restricted in 88%, 92%, 96% and 100% of estimated intake according to the Cobb guide. The AMEn was determined using linear regression between the feed intake and the AMEn of each diet. In both trials, the total excreta collection method was used. Because of the chemical composition, GMIX was not considered crude glycerine. The mean AMEn values of the products were 20.55 MJ/kg, 15.80 MJ/kg and 15.05 MJ/kg for GMIX, GSP and GOIL, respectively. There was a linear decrease (p < 0.01) in the AMEn values with the increasing age of the broilers. Numerically, it was observed that the AMEn values decreased until 28-30 day post-hatching and then remained constant until the finishing phase. It is concluded that products containing glycerine can be used as an energy source for broilers, but that AMEn values can vary according to age. Younger broilers have a higher capacity of energy utilisation from these feedstuffs.