Dietary Glycerol Research Articles

Evaluation of the nutritional value of glycerol for nursery pigs1

In Exp. 1, a total of 144 pigs (BW, 6.68 ± 0.17 kg) were weaned at 21 d, blocked by BW, and allocated to 48 pens with 3 pigs per pen. Pens were randomly assigned to 1 of 6 dietary treatments (0, 2.5, 5, 7.5, and 10% glycerol supplemented to replace up to 10% lactose in a basal starter 1 diet containing 20% total lactose, which was fed for 2 wk), and a negative control diet with 10% lactose and 0% glycerol. A common starter diet was fed for the next 2 wk. In Exp. 2, a total of 126 pigs (BW, 6.91 ± 0.18 kg) were weaned at 21 d of age, blocked by BW, and allocated to 42 pens with 3 pigs per pen. Pigs were assigned to 1 of 6 treatments in a 2 × 3 factorial arrangement in a randomized complete block design with factors being 1) glycerol inclusion in replacement of lactose in starter 1 diets (0 or 5%) fed for 2 wk, and 2) glycerol inclusion in starter 2 diets (0, 5, or 10%) fed for 3 wk. In Exp. 1, glycerol supplementation at 10% improved (P=0.01) ADG (266 vs. 191 g/d) and G:F (871 vs. 679 g/kg) during the starter 1 period when compared with the negative control. Incremental amounts of glycerol linearly (P<0.05) increased ADG and ADFI, but did not affect G:F during starter 1. There was no effect of feeding glycerol during the starter 1 phase on subsequent performance during the starter 2 phase or overall. Serum glycerol concentrations increased linearly (P=0.003) with increasing dietary glycerol, and serum creatinine (P=0.004) and bilirubin (P=0.03) concentrations decreased with increasing glycerol. In Exp. 2, glycerol did not affect performance during starter 1, but it linearly increased (P≤0.01) ADG and ADFI during starter 2 (464, 509, and 542 and 726, 822, and 832 g/d, respectively) and overall (368, 396, and 411 and 546, 601, and 609 g/d, respectively). At the end of the study, pigs were 1.0 and 1.5 kg heavier when fed 5 and 10% glycerol, respectively (linear, P<0.01). Serum glycerol concentrations increased linearly during starter 2 (P<0.001), but were not affected during starter 1. Glycerol supplementation increased serum urea N quadratically (P<0.001) and decreased creatinine linearly (P<0.05) in the starter 2 phase. Overall, data indicate that glycerol can be added to nursery pig diets at 10%, while improving growth performance.

Replacing corn with glycerol in diets for transition dairy cows

Expansion of the biofuels industry has increased the availability of glycerol as an alternative feed for dairy cows. The objective of this study was to determine the effects of glycerol on feed intake, milk production, rumen volatile fatty acids, and metabolic parameters in transition dairy cows. Multiparous Holstein cows were fed diets containing either high-moisture corn (n=11) or glycerol (n=12) from −28 to +56 d relative to calving. Glycerol was included at 11.5 and 10.8% of the ration dry matter for the pre- and postpartum diets, respectively. Prepartum feed intake was not changed by glycerol feeding (14.9 vs. 14.6 kg/d, control vs. glycerol) nor did postpartum feed intake differ (19.8 vs. 20.7 kg/d, control vs. glycerol). Overall milk yield did not differ (35.8 vs. 37 kg/d, control vs. glycerol) and milk composition, milk urea nitrogen, somatic cells, and energy balance were not different with glycerol feeding. Blood glucose content was decreased in cows fed glycerol during the prepartum period (59.1 vs. 53.4 mg/dL), and β-hydroxybutyrate concentration was increased (0.58 vs. 0.82 mmol/L, control vs. glycerol). Concentrations of blood nonesterified fatty acids did not differ between the treatment groups, and no response to glycerol for blood metabolites during the postpartum period was observed. Total rumen volatile fatty acid concentrations (mmol/L) did not differ between treatments, but proportions of rumen propionate and butyrate were greater for cows fed glycerol (22.7 vs. 28.6% of propionate, control vs. glycerol; and 11.5 vs. 15.3% of butyrate, control vs. glycerol) at the expense of acetate (61.4 vs. 51.5%, control vs. glycerol). These data indicate that glycerol is a suitable replacement for corn grain in diets for transition dairy cows.

Effects of differing levels of glycerol on rumen fermentation and bacteria

The effects of substituting corn with glycerol as a feed alternative were investigated using continuous fermenters. Four fermenters were used in a 4 × 4 Latin square design with four 10 days consecutive periods. Treatments diets contained 0 (T1), 36 (T2), 72 (T3) and 108 (T4) g glycerol/kg dry matter (DM). Diets consisted of 600 g/kg alfalfa hay and 400 g/kg concentrate (DM basis) and glycerol replaced the corn in the concentrate. Effluents were collected from each fermenter during the last 3 days of each period and analyzed for nutrients composition. On day 10 of each period, additional samples were collected from each fermenter at 3 h after the morning feeding and analyzed for volatile fatty acids (VFA), ammonia-nitrogen (NH 3-N), and microbial DNA concentration. Results showed that neutral detergent fiber (aNDFom) digestibility decreased (P<0.05) with the T3 and T4 diets compared with the T1 diet. Glycerol substitution had no effects on fermenters pH, NH 3-N concentration, and digestibility coefficients of DM and acid detergent fiber (ADFom). The molar proportion for acetate decreased (P<0.05) while the molar proportions for butyrate, valerate and isovalerate increased (P<0.05) with the glycerol diets compared with the T1 diet. The DNA concentrations for Butyrivibrio fibrisolvens and Selenomonas ruminantium decreased (P<0.05) with the T3 and T4 diets compared with the T1 diet. The DNA concentration for Clostridium proteoclasticum also decreased (P<0.05) with glycerol substitution. No differences in the DNA concentrations for Ruminococcus albus and Succinivibrio dextrinosolvens among diets were observed. Results from this study suggest that substituting corn with glycerol at low level had no adverse affects on fermentation, digestion or ruminal bacteria. Higher substitution levels, however, may adversely affect rumen fermentation through reducing fiber digestion, acetate production and bacterial populations.

Metabolizable energy content of refined glycerin and its effects on growth performance and carcass and pork quality characteristics of finishing pigs

Two studies were conducted with refined glycerin (97.7 and 97.5% glycerin for studies I and II, respectively) to determine ME content and effects on growth performance and carcass and pork quality measures of finishing pigs. An energy balance study using 24 barrows (21.5 ± 0.6 kg initial BW) determined the apparent ME content of glycerin using a generalized randomized block design with 2 dietary treatments: 1) control (99.85% corn + vitamins and minerals) and 2) glycerin (30% of corn in the control diet replaced with glycerin). A 7-d adaptation was followed by a 5-d collection period for feces and urine. The energy content of diets, feces, and urine was determined by bomb calorimetry. The DE of the glycerin diet was greater (P < 0.01) than that of the control diet (4,298 vs. 3,902 kcal/kg of DM); however, the ME content of the 2 diets was similar (3,820 vs. 3,723 kcal/kg of DM). The ME of refined glycerin (estimated by difference) was 3,584 kcal/kg of DM. A growth study was conducted with 128 gilts housed in groups of 4 and reared from 92.5 ± 0.24 kg of BW for a 28-d period, using a split-plot design with a 4 × 2 factorial arrangement of treatments: 1) dietary glycerin level (0, 5, 10, and 15%) and 2) preslaughter handling (gentle vs. intense). The handling treatment was included to simulate the range in handling intensities that are likely to be experienced in practice. At the end of the 28-d period, one-half of the pens on study were slaughtered and used for carcass and pork quality evaluation with 2 pigs from each pen being subjected to each of the preslaughter handling treatments. There were no interactions (P > 0.05) between dietary glycerin and preslaughter handling treatment. Dietary glycerin had no effect (P > 0.05) on growth performance, carcass measures, or meat quality. There were no differences (P > 0.05) between the gentle and intense handling treatments for carcass or pork quality measures. In conclusion, feeding glycerin to finishing pigs at up to 15% of the diet had no negative effect on growth performance or carcass and pork quality characteristics.

Use of crude glycerol, a biodiesel coproduct, in diets for lactating sows1,2

An experiment was conducted to evaluate the effect of dietary crude glycerol in lactating sow diets on sow and litter performance under heat stress conditions. Mixed parity (range = 0 to 13) sows (n = 345; 253 +/- 24 kg of BW) were assigned randomly within gestation housing location and parity to 1 of 4 dietary treatments. Treatments consisted of a corn-soybean-based control diet (CON) and 3, 6, or 9% glycerol added at the expense of corn and soybean meal. Liquid crude glycerol was incorporated in the complete diet at the time of mixing. Dietary treatments were imposed on d 109 of gestation (2.25 kg/d) when sows were moved into farrowing rooms. Heat index during lactation in farrowing rooms exceeded 25 degrees C for all sows. At farrowing, sows were allowed ad libitum access to feed throughout lactation. Dietary treatment tended (P = 0.08) to influence ADFI of sows (CON = 6.04 kg/d; 3% = 6.21 kg/d; 6% = 5.69 kg/d; 9% = 6.00 kg/d; pooled SE = 0.18). Up to 9% crude glycerol in the diet had no effect on sow BW and backfat loss, weaning-to-estrus interval, preweaning mortality of piglets, and ADG of piglets. Increasing dietary glycerol linearly reduced (P = 0.10) litter size at weaning (CON = 9.50; 3% = 9.60; 6% = 9.36; 9% = 9.39; pooled SE = 0.08). Daily water consumption was not affected by dietary treatment. Crude glycerol did not affect respiration rates or rectal body temperatures, indicating no efficacy in reducing heat stress of sows. Plasma glycerol concentrations increased linearly (P < 0.05) as dietary crude glycerol increased (CON = 1.21 microM; 3% = 1.69 microM; 6% = 7.21 microM; 9% = 29.04 microM; pooled SE = 1.58), but plasma glucose concentrations were not affected. Crude protein content of the milk of sows was not affected (P = 0.16) by dietary treatment. Dry matter (P = 0.07) and crude fat (P = 0.09) content of the milk of the sows tended to increase linearly (DM basis: CON = 17.84%; 3% = 18.43%; 6% = 18.98%; 9% = 18.48%; pooled SE = 0.34; crude fat: CON = 4.78%; 3% = 4.91%; 6% = 5.50%; 9% = 5.24%; pooled SE = 0.30), whereas milk ash concentration tended (P = 0.09) to decrease linearly with increasing dietary glycerol (CON = 0.77%; 3% = 0.79%; 6% = 0.74%; 9% = 0.74%; pooled SE = 0.02). Increasing dietary crude glycerol linearly increased (P < 0.05) lactose concentration in the milk of sows (CON = 5.16%; 3% = 5.30%; 6% = 5.43%; 9% = 5.46%; pooled SE = 0.10). Results from this study indicate that lactating sows fed diets containing up to 9% crude glycerol perform similarly to sows fed a standard corn-soybean meal diet.

Effects of glycerol on performance, egg traits, some blood parameters and antibody production to SRBC of laying hens

This study was designed to investigate the effects of the usage of glycerol from biodiesel production from soybean oil in laying hen diets on laying performance, egg traits, heterophils to lymphocytes ratio (H/L), some blood parameters and antibody production to SRBC. A total of 180 Lohmann Brown laying hens 39 weeks of age were allocated to four dietary treatments with one control group and three treatment groups and fed for 16 weeks. Each group was divided into five replicates as subgroups, comprising of 9 hens each. Glycerol was used at the level of 2.5, 5 and 7.5% in the diets of the first, second and third treatment groups, respectively. The diets were formulated to be isocaloric and isonitrogenous. Dietary treatments did not significantly affect body weight, egg production, egg weight, feed efficiency, mortality, egg albumen index, egg yolk index and egg Haugh unit, yolk weight percentage, exterior egg quality characteristics, excreta moisture, H/L ratio, blood parameters and antibody production to SRBC. Hens fed diets with 7.5% glycerol consumed significantly less feed than those of the other groups. Egg yolk cholesterol concentration was significantly higher for hens fed diets with 5 and 7.5% glycerol as compared to those of the other groups ( P < 0.01). The ratio of monounsaturated fatty acids (MUFA) to saturated fatty acids (SFA) in eggs was decreased ( P < 0.01) with dietary glycerol supplementation. The inclusion of glycerol had no significant effects on blood parameters, H/L ratio, antibody titers to SRBC and excreta moisture. It is concluded that glycerol can be used at 2.5% in the diets of laying hens without adverse effects on the measured parameters. Dietary glycerol at the levels of 5 and 7.5% increased egg yolk cholesterol and decreased the ratio of MUFA/SFA without affecting performance, other egg traits, immune response, H/L ratio, blood parameters and excreta moisture.

Evaluation of Glycerol from Biodiesel Production as a Feed Ingredient for Channel Catfish,Ictalurus punctatus

Glycerol is the main by-product of biodiesel production from vegetable oils and animal fats. It has been evaluated as an energy source for several farm animals. A study was conducted to examine the effects of various levels of glycerol in channel catfish, Ictalurus punctatus, diets. Fish with mean initial weight of 6.8 ± 0.1 g were stocked in 110-L flow-through aquaria and fed practical diets containing 0, 5, 10, 15, and 20% glycerol for 9 wk. There were no significant differences in feed consumption, weight gain, feed efficiency ratio, and liver lipid level among fish fed diets containing 0, 5, and 10% glycerol. However, fish fed diets containing 15 and 20% glycerol had reduced weight gain, feed efficiency, and liver lipid content. Survival was not affected by dietary glycerol levels. Blood glucose level was significantly higher in fish fed 5% glycerol than fish fed other diets. Fillet protein and fat generally decreased and fillet moisture increased as dietary glycerol level increased. It appears that channel catfish can utilize about 10% glycerol in the diet without adverse effects on feed consumption, weight gain, feed efficiency ratio, hemoglobin, hepatosomatic index, and liver lipid.

The use of glycerol in diets for finishing pigs

The production of fuel from renewable energy sources has generated increasing interest in recent years and biofuel production is being encouraged within the United Kingdom. If current government targets are to be met, approximately 2.7 million tonnes of oil seed rape are needed to supply biodiesel which will result in a significant amount of the by-product glycerol. Glycerol may be a useful source of energy in diets for pigs but there is limited research on the optimum level of inclusion, digestible energy (DE) content or on the effect on performance. Research by Mourot et al (1994) suggested that glycerol tended to reduce performance but significantly improved meat quality as assessed by drip loss. The aim of this study was to investigate the effect of glycerol inclusion in finishing pig diets on performance and meat quality.

Glycerol enhances intestinal aquaporin expression and improves glucose tolerance

Glycerol absorption is facilitated by aquaglyceroporins including aquaporin 3 (AQP3) and aquaporin 7 (AQP7). However, little is known regarding the interactions of dietary glycerol and control of AQP3 or AQP7mRNA expression in the gastrointestinal epithelium. The aim of this study was to examine the effects of feeding a diet containing glycerol combined with either fructose or starch on intake, growth, glucose metabolism, and intestinal AQP3 and AQP7 mRNA abundance. Male Sprague‐Dawley rats (n=8 to 9/group) were fed either a starch‐based control diet (STA) containing 63% carbohydrate, 63% fructose (FRU), a 47% fructose plus 16% glycerol (FRUGLY) , or a 47% starch‐based mix plus 16% glycerol (STAGLY) for six weeks. Glucose tolerance was determined after 3 weeks of feeding. Rats on STAGLY diet ate less (P &lt; 0.05) food (g) during the six week experiment (561, 685, 802 and 817 ± 15.9 for STAGLY, FRUGLY, FRU and CON) and gained less (P&lt;0.05) weight (g per 6 weeks) (46.8, 167, 76 and 182 ± 5.7 for STAGLY, FRUGLY, FRU and STA) than the other treatments. Real‐time PCR revealed (P &lt; 0.05) at least a 5X greater abundance of AQP3 and AQP7 mRNA in STAGLY animals compared to STA. The data show that the addition of glycerol improved glucose tolerance and increased AQP mRNA expression regardless of dietary carbohydrate background.

A chemical analysis of samples of crude glycerol from the production of biodiesel in Australia, and the effects of feeding crude glycerol to growing-finishing pigs on performance, plasma metabolites and meat quality at slaughter

The aims of this study were to: (i) determine the chemical composition of 11 samples of crude glycerol collected from seven Australian biodiesel manufacturers; and (ii) examine the effects of increasing levels of crude glycerol fed to growing-finishing pigs on performance, plasma metabolites and meat quality at slaughter. Chemical composition of crude glycerol samples varied considerably; glycerol content ranged between 38 and 96%, with some samples containing up to 29% ash and 14% methanol. One of these samples (76.1% glycerol, 1.83% methanol) was then fed to 64 female pigs (50.9 ± 5.55 kg; mean ± s.d.) allocated to one of five dietary treatments (0, 4, 8, 12 and 16% crude glycerol) until they reached 105 kg liveweight. There were no statistical differences in performance indices with increasing levels of added glycerol, although there was an unexpectedly high variation between treatments. Blood glycerol levels were unaffected by diet in week two of the experiment, but increased linearly (P &lt; 0.001) with increasing levels of dietary glycerol before slaughter. The inclusion of crude glycerol did not influence any meat quality parameters at slaughter (P &gt; 0.05). Diets containing added crude glycerol were less dusty after mixing, but diets that contained 8, 12 and 16% glycerol all formed a firm aggregate within 24 h of mixing that presented some feeding difficulties. This might restrict inclusion of glycerol in mash diets to dietary levels less than 8%. Furthermore, levels of residues such as methanol and ash should be monitored to prevent excessive amounts of these compounds in pig diets.

Sensory characteristics of loins from pigs fed glycerol and ractopamine HCl during the last 28 days of finishing (2009)

Sensory characteristics were evaluated on a total of 80 loins from pigs fed diets containing glycerol, ractopamine HCl (RAC), and a combination of glycerol and RAC during the last 28 d prior to harvest. A total of 1,054 pigs were blocked by weight and randomly allotted to 1 of 4 dietary treatments with 10 replications per treatment. Pigs were fed corn-soybean meal-based diets. Dietary treatments were arranged in a 2 × 2 factorial design with main effects of glycerol (0% or 5%) and RAC (0 or 6.75 g/ton). Pork loins from 1 randomly selected barrow and gilt from each pen were used for sensory analysis. There were no glycerol × RAC interactions or main treatment effects for cooking loss or Warner-Bratzler shear force (WBSF). Additionally, there were no glycerol × RAC interactions or main treatment effects for the sensory traits including myofibrillar tenderness, overall tenderness, pork flavor intensity, or off-flavor intensity. There was a glycerol × RAC interaction (P < 0.01) for the sensory trait of connective tissue amount. The interaction was a result of increased connective tissue amounts when glycerol was added to the diet without RAC but numerically decreased amounts when glycerol was fed in combination with RAC. In conclusion, feeding dietary glycerol or RAC singularly or in combination for 28 d prior to slaughter did not influence sensory characteristics of center-cut pork loin chops.; Swine Day, Manhattan, KS, November 19, 2009

Glycerol from biodiesel production: the new corn for dairy cattle

Glycerol, also known as glycerin, is a colorless, odorless, hygroscopic, and sweet-tasting viscous liquid. It is a sugar alcohol with high solubility index in water and has a wide range of applications in the food, pharmaceutical, and cosmetic industries. The use of glycerol in diets for dairy cattle is not novel; however, this interest has been renewed due to the increased availability and favorable pricing of glycerol as a consequence of recent growth in the biofuels industry. Experimental evidence supports the use of glycerol as a transition cow therapy but feeding rates are low, ranging from 5 to 8 % of the diet DM. There is a paucity of research that examines the use of glycerol as a macro-ingredient in rations for lactating dairy cows. Most reports indicate a lack of effect of addition of glycerol to the diet when it replaces corn or corn starch. Recent feeding experiments with lactating dairy cows indicate replacing corn with glycerol to a level of 15% of the ration DM does not adversely effect milk production or composition. Milk production was 37.0, 36.9, 37.3, 36.4 ± 0.6 kg/d and feed intake was 24.0, 24.5, 24.6, 24.1 ± 0.5 kg/d for 0, 5, 10 and 15% glycerol treatments respectively and did not differ (P > 0.05) except for a modest reduction in feed intake during the first 7 days for the 15% glycerol treatment. Glycerol fed to dairy cattle is fermented to volatile fatty acids in the rumen and early reports indicated that glycerol is almost entirely fermented to propionate. In vitro data indicates glycerol fermentation increases the production of propionate and butyrate at the expense of acetate. Rumen microbes appear to adapt to glycerol feeding and consequently, cows fed glycerol also require an adaptation period to glycerol inclusion. Debate exists regarding the fate of glycerol in the rumen and although most reports suggest that glycerol is largely fermented in the rumen, the extent of rumen digestion may depend on level of inclusion in the diet. Data are lacking regarding the rates of rumen fermentation of glycerol at intake levels for high producing dairy cattle. Current data indicates that glycerol can be included in diets fed to dairy cattle at macro ingredient levels; however, additional information is needed to permit a full appreciation of the feeding value of glycerol and the resulting impact on cow health and productivity.

Effect of crude glycerol on pellet mill production and nursery pig growth performance1,2

The objective of this study was to determine the effects of diets containing crude glycerol on pellet mill production efficiency and nursery pig growth performance. In a pilot study, increasing crude glycerol (0, 3, 6, 9, 12, and 15%) in a corn-soybean meal diet was evaluated for pellet mill production efficiency. All diets were steam conditioned to 65.5 degrees C and pelleted through a pellet mill equipped with a die that had an effective thickness of 31.8 mm and holes 3.96 mm in diameter. Each diet was replicated by manufacturing a new batch of feed 3 times. Increasing crude glycerol increased both the standard (linear and quadratic, P < 0.01) and modified (linear, P < 0.01; quadratic, P </= 0.02) pellet durability indexes up to 9% with no further benefit thereafter. The addition of crude glycerol decreased (linear; P < 0.01) production rate (t/h) and production efficiency (kWh/t). In a 26-d growth assay, 182 pigs (initial BW, 11.0 +/- 1.3 kg; 5 or 6 pigs/pen) were fed 1 of 7 corn-soybean meal-based diets with no added soy oil or crude glycerol (control), the control diet with 3 or 6% added soy oil, 3 or 6% added crude glycerol, and 6 or 12% addition of a 50:50 (wt/wt) soy oil/crude glycerol blend with 5 pens/diet. The addition of crude glycerol lowered (P < 0. 01) delta temperature, amperage, motor load, and production efficiency. The addition of crude glycerol improved (P < 0.01) pellet durability compared with soy oil and the soy oil/crude glycerol blend treatments. Pigs fed increasing crude glycerol had increased (linear, P = 0.03) ADG. Average daily gain tended to increase with increasing soy oil (quadratic; P = 0.07) or the soy oil/crude glycerol blend (linear, P = 0.06). Adding crude glycerol to the diet did not affect G:F compared with the control. Gain:feed tended to increase with increasing soy oil (linear, P < 0.01; quadratic, P = 0.06) or the soy oil/crude glycerol blend (linear, P < 0.01; quadratic, P = 0.09). Nitrogen digestibility tended (P = 0.07) to decrease in pigs fed crude glycerol compared with pigs fed the soy oil treatments. Apparent digestibility of GE tended (P = 0.08) to be greater in the pigs fed soy oil compared with pigs fed the soy oil/crude glycerol blends. In conclusion, adding crude glycerol to the diet before pelleting increased pellet durability and improved feed mill production efficiency. The addition of 3 or 6% crude glycerol, soy oil, or a blend of soy oil and glycerol in diets for 11- to 27-kg pigs tended to increase ADG. For pigs fed crude glycerol, this was a result of increased ADFI, whereas, for pigs fed soy oil or the soy oil/crude glycerol, the response was a result of increased G:F.

Effects of increasing glycerol and dried distillers grains with solubles on the growth performance and carcass characteristics of finishing pigs (2008)

A total of 1,160 barrows (PIC, initially 68.4 lb) were used in a 97-d study to determine the influence of glycerol and dried distillers grains with solubles (DDGS) on growing-finishing pig performance, carcass characteristics, and fat quality. Pigs were blocked by weight and randomly allotted to 1 of 6 dietary treatments with 7 replications per treatment. Pigs were fed corn-soybean meal-based diets arranged in a 2 × 3 factorial with main effects of glycerol (0, 2.5, or 5%) and DDGS (0 or 20%). Overall (d 0 to 97), there were no glycerol × DDGS interactions (P > 0.12) for growth performance, carcass characteristics, and carcass fat iodine value (IV). Increasing glycerol did not affect (P > 0.14) ADG or F/G. Adding 20% DDGS to the diet did not affect ADG. However, pigs fed diets with 20% added DDGS had greater (P < 0.02) ADFI resulting in poorer (P < 0.01) F/G than pigs fed diets with no DDGS. For carcass characteristics, pigs fed increasing glycerol tended to have increased (linear, P < 0.11) yield. Pigs fed diets with added DDGS had increased (P < 0.01) jowl fat, belly fat, and backfat IV compared with pigs fed diets with no DDGS. However, increasing dietary glycerol tended to decrease (linear, P < 0.11) backfat IV. In conclusion, feeding pigs 20% DDGS worsened F/G and increased carcass fat IV, whereas feeding glycerol did not influence growth performance but tended to improve carcass yield and reduce backfat IV.; Swine Day, 2008, Kansas State University, Manhattan, KS, 2008

Influence of glycerol and added fat on finishing pig performance (2008)

A 28-d study was conducted to determine the influence of dietary glycerol on growfinish pig performance. The experiment was conducted at a commercial swine research facility in southwest Minnesota. A total of 1,093 pigs (initially 171.3 lb, PIC) were blocked by weight and randomly allotted to 1 of 6 dietary treatments. Pigs were fed corn-soybean mealbased diets. The treatments were arranged in a 2 × 3 factorial with main effects of glycerol (0, 2.5, or 5%) and added fat (0 or 6%). Overall (d 0 to 28), there was a fat × glycerol interaction (P < 0.04) for ADFI. When 5% glycerol was added to diets without added fat, ADFI decreased; however, ADFI did not change when glycerol was added to diets containing 6% added fat.

Effects of glycerol and ractopamine hcl (paylean) on growth performance, carcass characteristics, and loin quality of finishing pigs (2008)

A total of 1,054 barrows and gilts (PIC, initially 207.8 lb) were used in a 28-d study to determine the influence of glycerol and ractopamine HCl (Paylean) on growing-finishing pig performance, carcass characteristics, and loin quality. The experiment was conducted in a commercial swine research facility in southwest Minnesota. Pigs were blocked by weight and randomly allotted to 1 of 4 dietary treatments with 10 replications per treatment. Pigs were fed corn-soybean meal-based diets. Dietary treatments were arranged in a 2 × 2 factorial with main effects of glycerol (0 or 5%) and ractopamine HCl (0 or 6.75 g/ton). Overall (d 0 to 28), there were no glycerol × ractopamine HCl interactions (P > 0.10) observed for growth performance. Pigs fed dietary glycerol had improved (P < 0.04) F/G, but ADG and ADFI (P > 0.40) were not affected. Pigs fed diets with added ractopamine HCl had improved (P < 0.01) ADG and F/G with a tendency (P > 0.08) for lower ADFI than pigs fed diets with no ractopamine HCl. For carcass characteristics, there were glycerol × ractopamine HCl interactions observed (P < 0.05) for percent yield and fat free lean index (FFLI). Adding either ractopamine HCl or glycerol to the control diet increased yield and FFLI; however, there were no additive effects when the combination of glycerol and ractopamine HCl was fed. Pigs fed ractopamine HCl had increased (P < 0.04) HCW, yield, loin depth, and FFLI. There was a glycerol × ractopamine HCl interaction (P < 0.01) observed for loin chop drip loss. Loin chop drip loss was numerically improved when glycerol and ractopamine HCl were added separately to the control diet; however, loin chop drip loss numerically decreased when the combination of glycerol and ractopamine HCl was fed. Glycerol did not affect (P > 0.22) loin characteristics. Ractopamine HCl tended to improve (P < 0.08) sirloin chop a* (redness) color. Neither ractopamine HCl nor glycerol influenced iodine value of belly fat, jowl fat, or backfat. In conclusion, pigs fed 5% glycerol had improved F/G, whereas pigs fed ractopamine HCl had improved growth and carcass characteristics and a tendency for improved loin a* color.; Swine Day, 2008, Kansas State University, Manhattan, KS, 2008

A simple wheat germ diet for studying the nutrient requirements of the Indian meal moth, Plodia interpunctella (Hübner)

Indian meal moth infestation of processed cereal products during storage could be managed with little or no use of conventional pesticides if there was a greater recognition and use of the moth's innate vulnerabilities. Slowing the growth rate of the infesting larvae is a simple strategy that can decrease the amount of damage and decrease the frequency of pesticide intervention. The growth rates of Indian meal moths on different cereal products varies widely indicating product-related differences in nutrient availability for the insects. Nutrient availability depends upon both the amounts of nutrients available in the cereal product and upon physical characteristics of the product that restrict the assimilation of nutrients. The development of control strategies for protecting processed cereal products based upon nutrient availability requires a simple, palatable test diet of known composition. Wheat germ mixed with 30% glycerol (w/w) provides a suitable growth medium for the Indian meal moth whose nutrients have been largely identified and quantified. Our studies indicate that dietary glycerol augments Indian meal moth growth and development on wheat germ by moisturizing the diet and probably provides a source of carbon and energy for larval growth.

Dietary glycerol and adult access to water: effects on fecundity and longevity in the almond moth

The quality of food eaten by larval insects will affect traits such as gamete production, fat reserves, muscle bulk and body size in the adult. Moreover, larvae also depend on high moisture content in the diet for survival. The almond moth ( Ephestia cautella) (W.) (Lepidoptera; Pyralidae) does not feed as an adult although it continues to drink water. We tested the idea that an almond moth could compensate for a low-water diet as a larva by increasing its water intake as an adult. We reared larvae on two different food sources with different moisture regimes; standard laboratory diet with glycerol (relatively wet) and standard diet without glycerol (relatively dry). Half the adult moths from each treatment were given water to drink before their first and only mating. Our results show that wet larval diets (i.e. containing glycerol) significantly decreased fecundity (total number of eggs laid and the proportion of hatched larvae), whilst it significantly increased male and female longevity. The interaction effect of water access for adult males and females was significant, independent of the glycerol in the larval diet. Longevity in females that were not presented with water as adults was slightly higher if mated with a male that had had access to water, suggesting a mating donation of water. However, females that received water as adults showed a decreased longevity if mated with a male who had also had access to water as an adult, indicating a negative effect of water if received by both males and females. In addition, when the larval diet included glycerol, increased number of eggs laid decreased female longevity, whilst an absence of glycerol in the larval diet resulted in low female longevity that was unlinked with fecundity. Glycerol is used in many artificial insect diets and the fact that it shows a strong effect on key life-history traits (reproductive output and longevity in this species), merits careful re-examination of its effects on these important traits in other laboratory models. We also discuss the possibility that larval diet can affect female reproductive decisions.

Effects of dietary glycerol on the expression of pterin carbinolamine dehydratase in the rat.

Earlier studies have shown that the abundance of hepatic phenyl-alanine hydroxylase (PAH) diminishes to 60% of control values in rats fed with a diet composed of 40% (w/w) glycerol [Guerin, Walsh, Donlon and Kaufman (1998) Int. J. Biochem. Cell Biol. 30, 1047-1054]. In this experimental model, there are corresponding decreases in the hepatic concentrations of both the hydroxylase cofactor, tetrahydrobiopterin, and the nucleotide guanosine triphosphate. We now show that the cytoplasmic activities of hepatic pterin-4a-carbinolamine dehydratase (PCD) are also lower in these animals, by approx. 50% compared with control values. Immunoblotting confirmed a diminution of protein abundance in vivo. PCD also functions as a dimerization cofactor (DCoH) for the hepatocyte nuclear factor 1alpha (HNF1alpha) and the relative abundance of PCD/DCoH in the nucleus is also decreased. There is a small reduction in the mRNA levels for PAH and for PCD/DCoH in the glycerol-fed animals. In the kidney, there is also a diminution in the abundance of both PAH and PCD proteins. Hepatic GTP cyclohydrolase I activity was not altered and the abundance of hepatic HNF1alpha remained unchanged. HNF1alpha is required for the expression of PAH in the liver and our results support a role for PCD/DCoH, through its interaction with HNF1alpha, in regulating the expression of PAH.

Retrotransposition of Glycerol Kinase-Related Genes from the X Chromosome to Autosomes: Functional and Evolutionary Aspects

Glycerol kinase catalyzes the metabolism of endogenously derived and dietary glycerol. GyK is a member of a small group of kinases termed ambiquitous enzymes, which are found either in the cytosol or as membrane-bound complexes associated with the voltage-dependent anion channel of the mitochondrial outer membrane. In Homo sapiens, the GyK gene family consists of an X-encoded locus and several X-linked and autosomal intronless retroposons, which, apparently, comprise both functional genes and processed pseudogenes. To study the role of the autosomal genes in mammalian physiology, we have isolated two murine GyK-like genes, determined their structures and chromosomal locations, and examined their functions. These sequences are intronless retroposons, which appear to be paralogues of the X-encoded, brain-specific GyK isoform and are expressed only in the testes. Though both retrotransposition events appear to have occurred prior to the primate–rodent divergence of some 65–80 million years ago, only one of the retrotransposed murine gene sequences, based upon its chromosomal location, is conserved with modern H. sapiens. To test the hypothesis that the murine GyK-like genes encode functional GyK activity, transient transfection of the gene sequences into COS7 cells was carried out. While in vitro translation confirmed that the transcripts could direct the synthesis of proteins of the appropriate size, no GyK activity was detected. Such data suggest that the autosomal GyK-like genes have evolved novel, testis-specific functions. A comparison of the human and mouse GyK-like gene sequences demonstrates the evolutionary relationships between each autosomal isoform and its corresponding X-linked ancestral locus.