Feeding value of glycerol as a replacement for corn grain in rations fed to lactating dairy cows

Characterization of crude glycerol and glycerol pitch from palm-based residual biomass

Crude glycerol (CG) and glycerol pitch (GP) are highly alkaline residues from biodiesel and oleochemical plants, respectively, and have organic content which incurs high disposal cost and poses an environmental threat. Characterization of these residues for composition and properties could provide insight into their quality for proper disposal and can help the biodiesel industry to adopt more sustainable practices, such as reducing waste and improving the efficiency of the production process, hence minimizing the impact of the biodiesel supply chain to the environment. These data also allow the identification and exploration of new ways for their utilization and transformation into highly value-added products. In this study, we evaluated four CG samples (B, C, D, and E) and two GP samples (F and G) obtained from Malaysian palm oil refineries, and the results were compared with pure glycerol (A). Spectroscopic analysis was performed using FTIR, 1H-, and 13C-NMR. All samples had similar density to A (1.26 g/cm3), except for F (1.31 g/cm3), while the density for E and G could not be determined due to their physical states. The pH and viscosity largely varied in the range of 7.26-11.89 and 43-225 cSt, respectively. The glycerol content of CG (B, C, D, and E) was high and consistent (81.7-87.3%) whereas GP F and G had 71.5 and 63.9% glycerol content, respectively. Major contaminants in CG and GP were water and matter organic non-glycerol (MONG), respectively. The water, ash, soap, and salt content were considerably low, which varied from 3.4 to 14.1%, 3.9 to 13.0%, 0.1 to 5.7%, and 4.1 to 9.2% respectively. Thermal analysis of CG and GP exhibited four phases of decomposition attributed to the impurities compared to the single phase in A. All samples had calorific values lower than A (18.1 MJ/kg) between 9.0 and 17.7 MJ/kg. Based on the results, CG and GP have high glycerol content which reveals their potential to be used as feedstock in bioconversion and chemical or thermal treatment while impurities may be removed by pre-treatment if required. As palm oil is one of the main feedstocks for the oleochemical industry, this work underlines the importance of characterization of the residue generated to provide additional data and information on palm-based agricultural industry wastes, minimize the impact of palm oil supply chain on the environment, and explore its potential usage for value-addition.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13399-023-04003-4.

Crude glycerin in the supplementation of crossbred heifers in tropical pastures

Crude glycerin (CG) is a biodiesel byproduct that has been tested as an alternative feed additive for use in beef production. After being absorbed, it is used in the liver to produce glucose, an important precursor of intramuscular fat in ruminants. This study aimed to evaluate the effect of CG (439 g/kg glycerol) on the performance and meat quality of crossbred heifers finished in Urochloa brizantha cv. Marandu. Thirty-six heifers with an initial BW of 301.5 ± 23.02 kg were used. They were supplemented for 154 days with the following levels of CG: mineral mixture (without CG), 33.3, 66.6 and 99.9 g/kg CG in the DM of the supplement. Supplement or pasture DM intakes, slaughter BW and carcass traits were not influenced (P > 0.05) by increasing levels of CG. The total fat content of the meat, the vaccenic (18:1 n-7t) and conjugated linoleic acid (18:2 c9-t11) increased with the addition of CG in the diet (P < 0.05). Crude glycerin can be included up to 99.9 g/kg of the total diet without changing the performance of crossbred heifers finished in the tropical pasture.

Meat goat diet supplementation with crude glycerine: Ruminal fermentation metabolism, blood chemistry profile, animal performance and carcass traits

The objective of this experiment was to determine the effects of feeding varying levels of crude glycerine (CG) on dry matter intake (DMI), animal performance, carcass traits and rumen volatile fatty acids (VFA) concentration in meat goats. Twenty-four intact male Boer goats (23.9 ± 1.0 kg initial BW and 4-5 months of age) were randomly assigned to one of four experimental diets (n = 6) containing 30% bermudagrass hay plus 70% concentrate mix with 0, 5, 10 or 15% CG in the diet on an as-fed basis, substituted for the corn portion of the concentrate. Feed offered and refusals were monitored daily for 84 days. Goats were weighed at 28-days interval. Blood and rumen samples were collected on day 84. At the end of the 84-days feeding period, goats were harvested, and carcass characteristics measured. Feed intake, average daily gain (ADG), gain-to-feed ratio (G:F), carcass traits and VFA concentrations were analysed as a completely randomized design. The CG did not influence animal body weight (BW) changes, ADG and G:F ratio but tended to (p = 0.06) decrease DMI. Molar per cent propionic acid increased linearly (p < 0.05) with increasing CG. The acetate: propionate (A:P) ratio decreased (p < 0.05) with increasing amounts of CG in the diet. The CG addition tended to increase (p = 0.09) the longissimus muscle (LM area) in meat goats. In conclusion, CG can replace corn in diet for growing meat goats when fed up to 15% of diet, improving ruminal propionate concentration, but decreasing A:P ratio without affecting animal performance and carcass traits.

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).

Corn silage rehydrated with crude glycerin in lambs' diets

We investigated whether the feed intake efficiency, digestibility, microbial efficiency, and nitrogen balance would be affected by inclusion of rehydrated corn grain silage with crude glycerin or water to substitute the dry corn in diets for feedlot lambs. Ten crossbred (Santa Ines × Dorper) uncastrated male lambs (25.6 ± 4.0 kg body weight) were assigned in a replicated 5 × 5 Latin square design and subjected to five experimental diets, one containing dry corn and four diets containing corn grain silage rehydrated with crude glycerin in levels of 0, 75, 150, and 225 in g/kg of natural matter. The moisture of 32.5% was maintained in all silages. The inclusion of crude glycerin represented 0, 40, 80, and 120 g/kg of total diet. The inclusion of rehydrated corn silage did not affect the DM, CP, EE, and ED intake. The diets with rehydrated corn silage improved the digestibility of DM, without affecting the fiber digestibility. The nitrogen losses were insignificant, resulting in the efficient use of dietary nutrients. In conclusion, corn silage rehydrated with 150 g/kg NM of crude glycerin is recommended as a feed to substitute dry corn diet, as it did not influence the nutrients intake, increased the dry matter digestibility with efficient use of the dietary nutrients, improving the animal performance in the feedlot.

Metabolism, Ketosis Treatment and Milk Production after Using Glycerol in Dairy Cows: A Review

Simple Summary

Glycerol, as well as being an attractive feed ingredient for cattle, is also a by-product of a wide range of industrial applications. Glycerol has potential value in farming since it improves metabolism, feed efficiency, and can alleviate the symptoms of ketosis. Data indicate that glycerol can be a suitable partial grain replacement in the diet of cows during the transition period and at the beginning of lactation. The impact on milk yield is not significant, but glycerol mostly decreases milk fat content. The inclusion of dietary glycerol in the ration of dairy cows has an affect on ruminal fermentation patterns. Glycerol is rapidly fermented in the rumen into propionate, and it is metabolized to glucose in the liver through the process of glycogenolysis. Additionally, glycerol administration to ruminants can reduce greenhouse gas emissions. The purpose of this review is to highlight the potential benefits and drawbacks related to the use of glycerol in cattle.

Abstract

The aim of this paper is to review and systematize the current state of knowledge on glycol metabolism in cattle. Glycerol, derived from biodiesel production, must be purified in order to be a useful product for feeding livestock. The use of glycerol in the feeding of ruminants can be justified for several reasons: (i) it is a source of energy in the ration, (ii) it is a glucogenic precursor, and (iii) it may have an effect on milk composition. The high energy value of glycerol provides the opportunity to use this raw material as a partial grain substitute in cattle feed rations. Dietary supplementation of glycerol is associated with increased propionate, butyrate, valerate, and isovalerate concentrations in the rumen. Glycerol can be used at up to 10%–15% of the dietary dry matter (DM) and is well-established as a treatment for ketosis in cows. Glycerol increases plasma glucose and may reduce non-esterified fatty acids and β-hydroxybutyrate levels. The use of glycerol does not have a clear effect on DM intake, milk yield, or milk composition. However, some authors have reported an increase in milk yield after glycerol supplementation associated with decreased milk fat concentration. It is also possible that the concentration in the milk of odd-chain fatty acids and cis-9, trans-11 conjugated linoleic acid may increase after glycerol application.

Linseed and glycerol in forage diets effect methane production and rumen fermentation parameters in a Rusitec semi-continuos system

Context The use of oilseeds as a feed ingredient has been proposed to improve fatty acid profiles and reduce methane (CH4) emissions. Glycerol has been used as a common additive in ruminant feeding systems with variable effects on CH4 production. The effects of the combination of these ingredients remain unknown. Aims The aim of this study was to assess the effects of feeding linseed and increasing concentrations of glycerol in forage diets supplemented with corn grain on nutrient disappearance, CH4 production and rumen fermentation parameters. Methods Experimental diets were: control (70:30% hay:corn); linseed (70:15 :15% hay:corn:linseed); 5% glycerol (70:10:15:5% hay:corn:linseed:glycerol); 10% glycerol (70:5:15:10% hay:corn:linseed:glycerol). Diets were incubated in a completely randomised design with four replicates per treatment in a Rusitec apparatus for 15 days (10 days adaptation, 5 days sampling). Key results Total VFA production (VFA, mmol/day) was quadratically increased due to glycerol concentration in the diets (P = 0.009). Acetate:propionate (A:P) decreased by the inclusion of linseed (P &lt; 0.001) and glycerol into the diets (P &lt; 0.001). Linseed inclusion in the diet reduced CH4 production, mg/DM disappeared (P = 0.004) by up to 36%. These effects were not altered by the addition of glycerol into the diets. Ammonia nitrogen (NH3-N) production increased 2-fold in the linseed-added diets, but this effect was partially reverted by increasing glycerol concentrations in the diets (P &lt; 0.001). Crude protein (CP) disappearance increased (P &lt; 0.001) in the linseed added diets, with no effect of glycerol addition. Neutral detergent fibre (aNDFom; P = 0.005) disappearance was increased by the addition of linseed to the diet. Conclusions The use of linseed in ruminant diets reduces CH4 emissions but increases NH3-N production in a Rusitec system. This latter effect is partially reverted by glycerol inclusion in the diet. Propionate production increases with the inclusion of glycerol, but does not alter CH4 production. Including linseed increases the in vitro CP disappearance without affecting DM total disappearance. Implications Care should be taken with the use of oilseeds in ruminant diets as it can reduce CH4 emissions but may cause important increases in NH3 emissions. Inclusion of glycerol may partially overcome this latter issue.

Symposium review: Decomposing efficiency of milk production and maximizing profit

The dairy industry has focused on maximizing milk yield, as it is believed that this maximizes profit mainly through dilution of maintenance costs. Efficiency of milk production has received, until recently, considerably less attention. The most common method to determine biological efficiency of milk production is feed efficiency (FE), which is defined as the amount of milk produced relative to the amount of nutrients consumed. Economic efficiency is best measured as income over feed cost or gross margin obtained from feed investments. Feed efficiency is affected by a myriad of factors, but overall they could be clustered as follows: (1) physiological status of the cow (e.g., age, state of lactation, health, level of production, environmental conditions), (2) digestive function (e.g., feeding behavior, passage rate, rumen fermentation, rumen and hindgut microbiome), (3) metabolic partitioning (e.g., homeorhesis, insulin sensitivity, hormonal profile), (4) genetics (ultimately dictating the 2 previous aspects), and (5) nutrition (e.g., ration formulation, nutrient balance). Over the years, energy requirements for maintenance seem to have progressively increased, but efficiency of overall nutrient use for milk production has also increased due to dilution of nutrient requirements for maintenance. However, empirical evidence from the literature suggests that marginal increases in milk require progressively greater marginal increases in nutrient supply. Thus, the dilution of maintenance requirements associated with increases in production is partially overcome by a progressive diminishing marginal biological response to incremental energy and protein supplies. Because FE follows the law of diminishing returns, and because marginal feed costs increase progressively with milk production, profits associated with improving milk yield might, in some cases, be considerably lower than expected.

Glycerol use in dairy diets: A systemic review

There is an increasing interest in the production of biodiesel as bio-renewable fuel source, with numerous biofuel byproducts becoming available. The annual productions of biodiesel and crude glycerol were 34.5 and 3.8 billion liters, respectively, in 2016 and that of biodiesel is expected to reach 41 billion liters in 2019. Glycerol is a sugar alcohol without a color or odor, but with a sweet taste and high solubility index in water. Experiments support the use of glycerol at low levels ranging from 5% to 8% of the diet dry matter as a transition cow therapy. Administration of glycerol increases serum glucose and decreases ketone bodies. Glycerol is very rapidly fermented in the rumen to propionate and butyrate, at the expense of acetate, resulting in a decreased milk fat. Because glycerol is highly fermented in the rumen, it requires an adaptation period at the beginning of feeding. Administration of glycerol in the diet of lactating animals was paralleled with a decreased or an unaffected feed intake in most experiments. Improved ruminal environment to enhance nutrient digestibility was observed in many experiments; however, others observed reduced digestion of dietary fiber with feeding glycerol. Enhanced, lowered, or unaffected milk production and composition were observed with the administration of glycerol in lactating animal diets; however, in most cases, glycerol decreased milk fat content. The inconsistencies between results of experiments are due to the level and the purity of glycerol, diets, production stage of the animals, and other factors. Therefore, further research should be conducted to establish the efficacy of different levels, purity and administration periods of glycerol, and production stage of dairy animals fed glycerol-based or supplemented diets.

Effects of replacing wheat starch with glycerol on methane emissions, milk production, and feed efficiency in dairy cows fed grass silage-based diets

To lower the effect of climate change from cattle production, we should aim at decreasing their enteric methane emissions per kilogram of milk or meat. Glycerol may be absorbed through the rumen epithelium and would consequently be less available to microbes in the rumen. Glycerol could thus supply dairy cows with energy for milk production without contributing much to methane production. This study evaluated the effect of replacing wheat starch with glycerol on milk production, feed intake, and methane emissions. Twenty-two Swedish Red cows in mid lactation were used in a switch-back, change-over experiment with 3 periods of 21 d. The 2 dietary treatments consisted of a total mixed ration based on (g/kg of dry matter) grass silage (605), rapeseed meal (120), and barley (70) and either wheat starch or refined glycerol (200) fed ad libitum. The glycerol diet resulted in higher dry matter intake (21.6 vs. 20.1 kg/d) and methane emissions (482 vs. 423 g/d) compared with the diet containing wheat starch, whereas no difference was found in energy-corrected milk yield (28.4 vs. 29.7 kg/d). These results indicate that when glycerol is mixed with the feed, it is available to rumen microbes to a larger extent than initially assumed. Compared with wheat starch, adding refined glycerol (200 g/kg of dry matter) to the feed of dairy cows does not seem to have the potential to decrease enteric methane emissions.

Evaluation of glycerol encapsulated with alginate and alginate-chitosan polymers in gut environment and its resistance to rumen microbial degradation

OBJECTIVE

To determine the effect of gut pH and rumen microbial fermentation on glycerol encapsulated in alginate and alginate-chitosan polymers.

METHODS

Glycerol was encapsulated at 2.5%, 5%, 7.5%, or 10% (w/w) with sodium alginate (A) and alginate-chitosan (AC) polymers. Surface morphology and chemical modifications of the beads were evaluated using scanning electron microscopy and Fourier transform infrared (FTIR) spectra. Encapsulation efficiency was determined at the 5% glycerol inclusion level in two experiments. In experiment 1, 0.5 g of alginate-glycerol (AG) and alginate-chitosan glycerol (ACG) beads were incubated for 2 h at 39°C in pH 2 buffer followed by 24 h in pH 8 buffer to simulate gastric and intestinal conditions, respectively. In experiment 2, 0.5 g of AG and ACG beads were incubated in pH 6 buffer at 39°C for 8 h to simulate rumen conditions. All incubations were replicated four times. Free glycerol content was determined using a spectrophotometer and used to assess loading capacity and encapsulation efficiency. An in vitro experiment with mixed cultures of rumen microbes was conducted to determine effect of encapsulation on microbial fermentation. Data were analyzed according to a complete block design using the MIXED procedure of SAS (SAS Institute, Cary, NC, USA).

RESULTS

For AG and ACG, loading capacity and efficiency were 64.7%, 74.7%, 70.3%, and 78.1%, respectively. Based on the FTIR spectra and scanning electron microscopy, ACG treatment demonstrated more intense and stronger ionic bonds. At pH 6, 36.1% and 29.7% of glycerol was released from AG and ACG, respectively. At pH 2 minimal glycerol was released but pH 8 resulted in 95.7% and 93.9% of glycerol released from AG and ACG, respectively. In vitro microbial data show reduced (p<0.05) fermentation of encapsulated glycerol after 24 h of incubation.

CONCLUSION

The AC polymer provided greater protection in acidic pH with a gradual release of intact glycerol when exposed to an alkaline pH.

Effects of crude glycerin from biodiesel on the diets of lambs: intake, digestibility, performance, feeding behavior, and serum metabolites

This study was conducted to test the hypothesis that the inclusion of crude glycerin of up to 21% of DM in the diets of lambs will not compromise variables related to animal production or health. Forty-four uncastrated Santa Inês crossbreed lambs with an average age of 5 mo and a BW average of 23.9 ± 0.34 kg (mean ± SD) were distributed into four treatment groups (11 replicates per group) including 0%, 7%, 14%, or 21% crude glycerin on a DM basis. The inclusion of crude glycerin in the diets promoted a quadratic increase in DM (P = 0.018), CP (P = 0.004), and TDN (P = 0.017). There was a linear decrease (P < 0.001) in NDF and nonfibrous carbohydrate (NFC) intake caused by glycerin in the diets. There was a linear increase (P < 0.001) in ether extract (EE) intake. There was a linear reduction in NDF (P = 0.011) and NFC (P < 0.001) for effective consumption of the diets. There was a linear increase (P < 0.001) in EE effectively consumed by the lambs, and there were no differences in the CP that was effectively consumed (P = 0.267) by glycerin. Digestibility coefficients of DM, CP, NDF, NFC, and TDN presented a linear decrease in crude glycerin inclusion. The EE digestibility presented a linear increase. The inclusion of crude glycerin in the diets promoted a quadratic increase in final BW (P = 0.015), ADG (P < 0.001), and G:F ratio (P < 0.001). There was no effect (P > 0.05) of crude glycerin inclusion in the diets on time spent (%); number of events per day; duration of events (minutes) for feeding, rumination, and idling; number of chews per bolus; or total chewing time for the lambs. The inclusion of crude glycerin in the diets improved feeding efficiency of DM (P = 0.005) and NDF (P = 0.004). The rumination efficiency of DM (P < 0.001) and NDF (P < 0.001) presented a linear decrease. The total protein, albumin, globulin, albumin:globulin ratio, triglycerides, alanine aminotransferase levels, aspartate aminotransferase, and gamma glutamyl transferase serum concentrations did not differ (P > 0.05) through the addition of crude glycerin to the diets of the lambs. However, the crude glycerin in the diets led to a linear decrease in urea-N (P = 0.004) and glucose (P <0.001), as well as a linear increase in the cholesterol (P = 0.043) serum concentrations of the lambs. The recommended inclusion of crude glycerin is up to a 4.7% DM level because of improved performance growth without compromising feeding behavior and blood metabolites.

Effects of high concentrations of crude glycerin in diets for feedlot lambs: feeding behaviour, growth performance, carcass and non-carcass traits

The effects of high concentrations of crude glycerin were investigated in diets for feedlot lambs. Forty crossbred (Santa Ines × Dorper) uncastrated male lambs (21.7 ± 2.7 kg bodyweight) were assigned to a complete randomised block and subjected to four experimental diets containing 0, 100, 200, or 300 g crude glycerin/kg DM. Animals were weighed at 14-day intervals and were harvested when they reached ~35 kg bodyweight. The feed intake, feeding behaviour, growth performance, carcass and meat traits, and edible non-carcass components were evaluated. The inclusion of more than 100 g/kg crude glycerin in the diets increased days on feed and decreased DM intake and average daily gain. Crude glycerin increased number of chews and the time spent chewing per feed bolus. There were no effects of crude glycerin on pH and colour of Longissimus muscle at 45 min or 24 h after slaughter, as well as on other carcass and edible non-carcass characteristics. The addition of crude glycerin reduced perirenal fat without detrimental effect on others fat deposition sites. In conclusion, the addition of up to 100 g/kg DM in diets for crossbred finishing lambs seems to be the most interesting strategy, as it promotes greatest animal performance. However, the inclusion of up to 300 g/kg DM of the by-product could be possible depending on glycerin market price and the structure of feedlot operation, with favourable economic results despite high inclusions reflect in greater number of days on feed.

Lactobacillus reuteri suppresses E. coli O157:H7 in bovine ruminal fluid: Toward a pre-slaughter strategy to improve food safety?

The bovine gastrointestinal tract (GIT) is the main reservoir for enterohaemorrhagic Escherichia coli (EHEC) responsible for food-borne infections. Therefore, it is crucial to develop strategies, such as EHEC suppression by antagonistic microorganisms, to reduce EHEC survival in the GIT of cattle and to limit shedding and food contamination. Most human-derived Lactobacillus reuteri strains produce hydroxypropionaldehyde (HPA), an antimicrobial compound, during anaerobic reduction of glycerol. The capacity of L. reuteri LB1-7, a strain isolated from raw bovine milk, to produce HPA and its antimicrobial activity against an O157:H7 EHEC strain (FCH6) were evaluated in bovine rumen fluid (RF) under strict anaerobiosis. EHEC was totally suppressed when incubated in RF inoculated with L. reuteri LB1-7 and supplemented with 80 mM glycerol (RF-Glyc80). The addition of LB1-7 or glycerol alone did not modify EHEC survival in RF. Glycerol was converted to HPA (up to 14 mM) by LB1-7 during incubation in RF-Glyc80, and HPA production appeared to be responsible for EHEC suppression. The bactericidal activity of L. reuteri LB1-7, the concentration of glycerol required and the level of HPA produced depended on physiological and ecological environments. In vitro experiments also showed that EHEC inoculated in rumen fluid and exposed to L. reuteri and glycerol had a very limited growth in rectal contents. However, L. reuteri exerted an antimicrobial activity against the rumen endogenous microbiota and perturbed feedstuff degradation in the presence of glycerol. The potential administration of L. reuteri and glycerol in view of application to finishing beef cattle at the time of slaughter is discussed. Further in vivo studies will be important to confirm the efficiency of L. reuteri and glycerol supplementation against EHEC shedding in ruminants.

Crude glycerin decreases nonesterified fatty acid concentration in ewes during late gestation and early lactation

Crude glycerin is a gluconeogenic substrate in ruminants and may help to decrease the occurrence of pregnancy toxemia. The objective in this trial was to determine the effects of feeding a diet containing crude glycerin on DMI, milk yield, milk composition, and blood metabolites in periparturient ewes and lamb performance. One hundred eighteen 90 (±1.1)-d pregnant Santa Inês ewes were used. After lambing, 32 ewes (62.8 ± 1.3 kg BW) were allotted in a randomized complete block design defined by prelambing diet, BW, BCS, lambing date, type of birth (single or twin), and sex of offspring. Diets were isonitrogenous (13.0 ± 0.3% CP, DM basis), composed of concentrate and raw sugarcane bagasse (70:30 ratio, DM basis), and fed ad libitum daily. Crude glycerin (83.6% glycerol) levels were 0 or 10% (DM basis), corresponding to the experimental diets G0 and G10, respectively. From 8 until 56 d of lactation, DMI was determined. In the same period, once a week at 1000 h, the ewes were separated from the lambs and mechanically milked after intravenous administration of 10 IU of synthetic oxytocin. Three hours after the first milking, ewes were milked again and milk yield and composition were determined. Glucose, NEFA, and β-hydroxybutyrate (BHBA) were determined at -14, -7, 0, 7, 14, 28, and 56 d relative to lambing and insulin was determined at -14, -7, 0, and 7 d. Crude glycerin did not affect DMI (2.2 kg/d for G0 vs. 2.2 kg/d for G10; = 0.93) or milk production (171 g/3 h for G0 vs. 164 g/3 h for G10; = 0.66). However, there was a decrease ( = 0.01) in milk fat percentage (8.1% for G0 vs. 7.0% for G10) for ewes fed glycerin. Ewes fed the G10 diet had decreased ( < 0.01) NEFA concentration (0.27 mmol/L for G0 vs. 0.18 mmol/L for G10). There was an interaction between diet × time for glucose ( = 0.04), insulin ( = 0.05), and BHBA ( = 0.01); feeding glycerin increased glucose (5.61 mmol/L for G0 vs. 7.42 mmol/L for G10; < 0.01) and insulin concentrations (10.5 μIU for G0 vs. 24.5 μIU for G10; < 0.01) at parturition compared with G0. The BHBA was less ( = 0.02) on the day of lambing (0.40 mmol/L for G0 vs. 0.29 mmol/L for G10) and it was greater ( < 0.01) on d 56 for ewes fed the G10 diet (0.46 mmol/L for G0 vs. 0.61 mmol/L for G10). There was no effect of diets fed to ewes on lamb growth from birth to weaning. Crude glycerin improved energy balance of periparturient ewes, suggesting a reduced risk of developing clinical metabolic-related disorders. Crude glycerin can be added at 10% of ewes' diets without affecting DMI and milk yield.

Crude glycerin as a replacement for corn in starter feed: performance and metabolism of pre-weaned dairy calves

The purpose of this study was to evaluate the effect of partial replacement of corn in the starter feed with crude glycerin on performance and energy metabolism of liquid-fed dairy calves. Twenty-four newborn individually housed Holstein calves were blocked according to weight and date of birth and randomly assigned to different starter feed treatments during 8 weeks: no crude glycerin; 5% crude glycerin; 10% crude glycerin on dry matter basis. All calves were individually fed daily 4 L of a commercial milk replacer (22.3% crude protein and 19.3% fat). Calves had individual access to starter diet and ad libitum access to water daily. Individual feed intake and faecal scores were recorded daily. Bodyweight and corporal measurements (heart girth, hip width, and withers height) were weekly recorded. From the second week of age, blood samples were collected weekly, 2 h after morning feeding, for determination of plasma glucose and β-hydroxybutyrate concentrations. Ruminal fluid was collected at 4, 6 and 8 weeks of age for determination of pH and short-chain fatty acids. At the end of the eighth week, animals were harvested to evaluate development of the proximal digestive tract. Feed intake, average daily gain, bodyweight or body measurements were not affected (P > 0.05) by the inclusion of crude glycerin in the starter feed. Faecal scores indicated that most of the calves had mild diarrhoea, with no treatment effect. Total short-chain fatty acids and the concentration of individual acids, as well as blood parameters, were not affected (P > 0.05) by the feed treatments. The total forestomach weight, the average weight of each compartment, the maximum capacity of reticulum-rumen, and papillae number, height and width were not affected (P > 0.05). In conclusion, crude glycerin can be used as an alternative energy source, replacing corn up to 10% in the starter feed for liquid-fed dairy calves without affecting growth, rumen development or metabolism.

Biorefinery for Glycerol Rich Biodiesel Industry Waste

The biodiesel industry has the potential to meet the fuel requirements in the future. A few inherent lacunae of this bioprocess are the effluent, which is 10 % of the actual product, and the fact that it is 85 % glycerol along with a few impurities. Biological treatments of wastes have been known as a dependable and economical direction of overseeing them and bring some value added products as well. A novel eco-biotechnological strategy employs metabolically diverse bacteria, which ensures higher reproducibility and economics. In this article, we have opined, which organisms and what bioproducts should be the focus, while exploiting glycerol as feed.

Effects of Elevated Crude Glycerin Concentrations on Feedlot Performance and Carcass Characteristics in Finishing Steers

Twenty crossbred steers (400±40.1 kg of initial body weight) were used to assess the effects of a dietary supplementation with crude glycerin (CG) as a substitute for corn grain on performance, carcass traits, and meat quality. Four isocaloric and isonitrogenous diets were offered to the experimental animals (5 steers per treatment) for 121 days using randomized complete block design. The steers individually received dietary treatments containing 0%, 7%, 14%, and 21% of CG (88.91% pure) on a dry matter (DM) basis. The diets were offered ad libitum as total mixed rations twice daily. Weight gain and carcass traits were determined. At the end of the experimental period, the harvest data and carcass characteristics of the steers were recorded, and meat quality was determined. No significant effect of CG inclusion was observed in any of the growth performance and carcass characteristics traits studied. Also, there were no apparent effects of diets (p>0.05) on meat quality (pH, water holding capacity, drip losses, and cooking losses). The study concluded that CG could be used as a substitute for corn grain up to the level of approximately 21% of DM in the diets of finishing steers.

Effect of glycerol in combination with alfalfa on in vitro gas production and microbial protein synthesis

Alfonso-Ávila, Á. R., Charbonneau, E., Lafrenière, C. and Berthiaume, R. 2015. Effect of glycerol in combination with alfalfa on in vitro gas production and microbial protein synthesis. Can. J. Anim. Sci. 95: 577–588. This study sought to determine the effect of added glycerol on microbial protein synthesis, ruminal degradation and utilization of alfalfa at different concentrations of nonstructural carbohydrates (NSC), using in vitro gas production. The 2×3 factorial plus one treatment consisted of oven-dried alfalfa with two NSC levels [high: 17.9 (HNSC) or low: 7.4% dry matter (DM) (LNSC)] and three glycerol treatments [control without glycerol, 15% crude glycerol (CG) and 15% pure glycerol (PG)], the additional treatment was LNSC+exogenous sugars (LNSC+ES: LNSC with 5% sucrose+5% starch). Five pre-planned contrasts were evaluated from the seven treatments: (1) HNSC vs. LNSC alfalfa; (2) with glycerol vs. without; (3) interaction of alfalfa and glycerol; (4) CG vs. PG, and; (5) LNSC+ES vs. HNSC. Gas production over 24 h was higher for HNSC than LNSC (202 vs. 179 mL g−1 DM) and with glycerol than without glycerol (202.2 vs. 168 mL g−1 DM). A decrease in the acetate:propionate ratio was observed for HNSC compared with LNSC (2.87 vs. 3.27) and for the addition of glycerol vs. no glycerol (2.78 vs. 3.65). Reduced microbial mass (185.5 vs. 240.5 mg g−1 DM) was observed for CG compared with PG. The LNSC+ES treatment had lower microbial protein synthesis and propionic acid production in relation to HNSC. No significant interaction was observed between the effect of NSC content of alfalfa and glycerol utilization. When effects were studied separately, results indicate that increasing NSC in alfalfa stimulates the synthesis of microbial protein. Also, the addition of glycerol promotes the synthesis of glucose precursors. Finally, the type of glycerol has an impact on results obtained suggesting caution when extrapolating results for PG to CG.

Short communication: Regulation of hepatic gluconeogenic enzymes by dietary glycerol in transition dairy cows

Nutritional status and glucose precursors are known regulators of gluconeogenic gene expression. Glycerol can replace corn in diets fed to dairy cows and use of glycerol is linked to increased rumen propionate production. The effect of dietary glycerol on the regulation of gluconeogenic enzymes is unknown. The objective of this study was to examine the effect of glycerol on expression of pyruvate carboxylase (PC), cytosolic and mitochondrial phosphoenolpyruvate carboxykinase (PEPCK-C and PEPCK-M), and glucose-6-phosphatase. Twenty-six multiparous Holstein cows were fed either a control diet or a diet where high-moisture corn was replaced by glycerol from -28 through +56 d relative to calving (DRTC). Liver tissue was collected via percutaneous liver biopsy at -28, -14, +1, +14, +28, and +56 DRTC for RNA analysis. Expression of PC mRNA increased 6-fold at +1 and 4-fold at +14 DRTC relative to precalving levels. Dietary glycerol did not alter expression of PC mRNA expression. Expression of PEPCK-C increased 2.5-fold at +14 and 3-fold at +28 DRTC compared with +1 DRTC. Overall, dietary glycerol increased PEPCK-C expression compared with that of cows fed control diets. The ratio of PC to PEPCK-C was increased 6.3-fold at +1 DRTC compared with precalving and tended to be decreased in cows fed glycerol. We detected no effect of diet or DRTC on PEPCK-M or glucose-6-phosphatase mRNA, and there were no interactions of dietary treatment and DRTC for any transcript measured. Substituting corn with glycerol increased the expression of PEPCK-C mRNA during transition to lactation and suggests that dietary energy source alters hepatic expression. The observed increase in PEPCK-C expression with glycerol feeding may indicate regulation of hepatic gene expression by changes in rumen propionate production.

Carcass characteristics and meat quality of lambs fed high concentrations of crude glycerin in low-starch diets

In this study, we evaluated the effects of total corn replacement with crude glycerin on carcass characteristics and meat quality of feedlot lambs fed high-concentrate diets with low starch. Forty non-castrated Santa Ines lambs (23.5 ± 3.56 kg BW) were assigned to a randomized complete block design with five dietary treatments: 0%, 7.5%, 15%, 22.5%, or 30% crude glycerin, replacing corn. Animals were slaughtered at a BW of 38 kg after 72 ± 20 days. The addition of up to 30% crude glycerin reduced carcass weight and yield (P ≤ 0.02). Odd-chain fatty acids, oleic, palmitoleic, total unsaturated, and monounsaturated fatty acids were increased (P ≤ 0.01) while CLA tended to increase in glycerin-fed lambs (P = 0.06). Crude glycerin decreased stearic, palmitic, transvaccenic, total saturated fatty acids, and atherogenicity index (P < 0.01). High concentrations of crude glycerin in low-starch diets reduced carcass weights, nevertheless improved meat quality by increasing unsaturated and odd-chain fatty acid contents.

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.

Metabolic effects of glycerol supplementation and aerobic physical training on Wistar rats

We evaluated the effects of oral glycerol supplementation on trained rats fed a normal diet. Wistar rats were distributed among 6 groups in a completely randomized 2 × 3 factorial design. The animals were subjected to 6 weeks of aerobic training. In the last 4 weeks, the animals’ diet was supplemented with saline, glucose, or glycerol. Data were subjected to one-way analysis of variance (ANOVA) followed by a Student–Newmann–Keuls test, with values for P < 0.05 considered statistically significant. The change in body mass was lower in the trained groups, and their food and water consumption were higher. Glycerol supplementation resulted in an increase in the levels of triacylglycerol (TAG) and total cholesterol, as well as in the area and diameter of adipocytes. When associated with training, these parameters were similar to those of other trained groups. Levels of low-density lipoprotein + very-low-density lipoprotein cholesterol decreased in the trained animals that received glycerol compared with the non-trained ones. Glycerol consumption caused a reduction in food intake and increased the villous:crypt (V:C) ratio. No changes in glycemia, high density lipoproteins, or density of adipocytes were observed. Supplementation with glycerol together with aerobic physical training promoted beneficial metabolic effects. However, in non-trained rats glycerol increased the diameter and area of adipocytes, as well as the levels of TAG and total cholesterol.

Effects of dietary crude glycerin supplementation on nutrient digestibility, ruminal fermentation, blood metabolites, and nitrogen balance of goats

This experiment was conducted to evaluate the effects of increasing concentrations of crude glycerin (CGLY) in diets on nutrient utilization, ruminal fermentation characteristics, and nitrogen utilization of goats. Four male crossbred (Thai Native×Anglo Nubian) goats, with an average initial weight of 26±3.0 kg, were randomly assigned according to a 4×4 Latin square design with four 21 days consecutive periods. Treatments diets contained 0%, 5%, 10%, and 20% of dietary DM of CGLY. Based on this experiment, there were no significant differences (p>0.05) among treatment groups regarding DM intake and digestion coefficients of nutrients (DM, OM, CP, EE, NDF, and ADF). Likewise, mean serum glucose, BHBA, and PCV concentrations were not affected (p>0.05) by dietary treatments, whereas serum insulin concentration linearly increased (L, p = 0.002) with increasing the amount of CGLY supplementation. Ruminal pH, NH₃-N, and BUN concentration were unchanged by dietary treatments, except for 20% of CGLY, NH₃-N, and BUN were lower (p<0.05) than for the diets 10% of CGLY, while the difference between the diets 0%, 5%, and 20% of CGLY were not significant. The amount of N absorption and retention were similar among treatments. Based on this study, CGLY levels up to 20% in total mixed ration could be efficiently utilized for goats and this study elucidates a good approach to exploiting the use of biodiesel production for goat production.

Effects of feeding dry glycerol to primiparous Holstein dairy cows on follicular development, reproductive performance and metabolic parameters related to fertility during the early post-partum period

This study examined the effects of dry glycerol supplementation on follicular growth, post-partum interval to first ovulation, concentration of serum metabolites and hormones related to fertility, body condition score (BCS) and body weight (BW) in primiparous Holstein dairy cows. Sixty primiparous Holstein dairy cows were randomly assigned to two groups (control: n = 30 and glycerol supplemented: n = 30). Dry glycerol (250 g/day/cow) was fed as a top dressing to the common lactating total mixed ration (TMR) from parturition to 21 days post-partum. Ovaries were examined four times using ultrasonography on days 13, 19, 25 and 36 post-partum to determine ovarian follicular growth. Concentration of serum metabolites and hormones was determined weekly. Body condition score was evaluated weekly from weeks 1 to 5 after parturition, and BWs were recorded three times on days 1, 11 and 21 during the experimental period. The cows fed dry glycerol had more large follicles (p < 0.0001) and corpora lutea (CL) (p = 0.02) compared with the control cows. Days to the first ovulation (p = 0.06), days to first oestrus (p = 0.05), services per conception (p = 0.06) and days open (p = 0.004) were positively affected by dry glycerol supplementation. Serum concentration of glucose and insulin was higher in dry glycerol-supplemented cows (p = 0.1; p = 0.06, respectively). Feeding glycerol had no effect on mean serum concentrations of β-hydroxybutyrate, non-esterified fatty acids and IGF-1 during the experimental period. However, significant differences were observed at concentration of BHBA and IGF-1 (p = 0.02 and p = 0.04, respectively) between two groups on day 21 after calving. The cows in the glycerol-fed group had higher serum progesterone concentrations on days 33 (p = 0.007) and 36 (p = 0.004) after calving. Supplemented cows had lower body condition loss during weeks 1-5 after calving compared with the control cows (0.34 vs 0.41 BCS). In week 13 post-partum, the proportion of cycling cows was 83.3 and 69.9% for those which received supplemented or non-supplemented diet, respectively. These results demonstrated that feeding dry glycerol as a glucogenic supply may be useful to improve negative energy balance and reproductive efficiency in young cows which calve with high requirement of energy.