Effects of dietary urea supplementation on performance of selected insect species.

Feeding costs of farmed insects may be reduced by applying alternative nitrogen sources such as urea that can partly substitute true proteins. The aim of this study was to examine the effects of different nitrogen sources on body weight (BW) and survival rate (SR) of the Jamaican field cricket (JFC, Gryllus assimilis), the house cricket (HC, Acheta domesticus), yellow mealworm larvae (YM, Tenebrio molitor) and superworm larvae (SW, Zophobas morio). Crickets were either housed individually or in groups, and larvae were group-housed. Six isonitrogenous feeds composed of 3.52% nitrogen were designed for all four insect species using four independent replicates with micellar casein: urea proportions of 100-0%, 75-25%, 50-50%, 25-75%, 0-100% and 100% extracted soybean meal. All selected insect species were able to utilise urea. However, urea as the only nitrogen source resulted in low final BW. In the HC, the JFC, and the YM on nitrogen basis urea can replace 25% of micellar casein without having any negative effects on BW and SR in comparison to the 100% micellar casein group. In the SW, a 25% urea level did not have a significant effect on final BW, but SR decreased significantly.

Fructose, glucose and fat interrelationships with metabolic pathway regulation and effects on the gut microbiota.

The purpose of this 30-day feeding study was to elucidate the changes, correlations, and mechanisms caused by the replacement of the starch content of the AIN-93G diet (St) with glucose (G), fructose (F) or lard (L) in body and organ weights, metabolic changes and caecal microbiota composition in rats (Wistar, SPF). The body weight gain of rats on the F diet was 12% less (P = 0.12) than in the St group. Rats on the L diet consumed 18.6% less feed, 31% more energy and gained 58.4% more than the animals on the St diet, indicating that, in addition to higher energy intake, better feed utilisation is a key factor in the obesogenic effect of diets of high nutrient and energy density. The G, F and L diets significantly increased the lipid content of the liver (St: 7.01 ± 1.48; G: 14.53 ± 8.77; F: 16.73 ± 8.77; L: 19.86 ± 4.92% of DM), suggesting that lipid accumulation in the liver is not a fructose-specific process. Relative to the St control, specific glucose effects were the decreasing serum glucagon (-41%) concentrations and glucagon/leptin ratio and the increasing serum leptin concentrations (+26%); specific fructose effects were the increased weights of the kidney, spleen, epididymal fat and the decreased weight of retroperitoneal fat and the lower immune response, as well as the increased insulin (+26%), glucagon (+26%) and decreased leptin (-25%) levels. This suggests a mild insulin resistance and catabolic metabolism in F rats. Specific lard effects were the decreased insulin (-9.14%) and increased glucagon (+40.44%) and leptin (+44.92%) levels. Relative to St, all diets increased the operational taxonomic units of the phylum Bacteroidetes. G and L decreased, while F increased the proportion of Firmicutes. F and L diets decreased the proportions of Actinobacteria, Proteobacteria and Verrucomicrobia. Correlation and centrality analyses were conducted to ascertain the positive and negative correlations and relative weights of the 32 parameters studied in the metabolic network. These correlations and the underlying potential mechanisms are discussed.

Effect of fulvic and humic acids on copper and zinc homeostasis in rats.

The objective of this study was to investigate the effects of fulvic acid (FA) and humic acid (HA), the two main compounds of humic substances (HSs), on copper (Cu) and zinc (Zn) homeostasis. Seventy-two male Wistar rats were randomly divided into nine experimental groups. The control diet (AIN-93G formula) and the diets supplemented with 0.1%, 0.2%, 0.4% and 0.8% FA or HA were fed for 26 days. Cu and Zn concentrations of the large intestinal content (LIC), liver, kidney, femur and hair were determined. FA and HA did not influence significantly the Cu or Zn contents of the experimental diets, the rats' feed intake, weight gain and the feed to gain ratio. Both FA and HA decreased the Cu concentrations of the LIC significantly and in a dose-related manner; however the absorption-stimulating effect of HA was more pronounced. FA increased the Cu content of the liver, but neither FA nor HA had a dose-dependent effect on it. FA or HA supplementations had no significant effect on the Cu concentration of the kidney. At the concentrations used, dietary FA or HA supplementations are not promising growth promoters. FA influences the Cu homeostasis unlike HA, because FA not only stimulates Cu absorption, but the extra quantity of absorbed Cu is retained in the organism. The stimulatory effect of HA on Zn absorption may not be manifested in Cu and Zn homeostasis, because of the tight connection of these microelements to FA and HA, which prevents the transmission of Zn from the ZnHA complex to the organs. As regards the effect of FA and HA on Cu and Zn homeostasis, both FA and HA stimulated the absorption of these microelements, but only FA increased the retention of Cu (in the liver) and Zn (in the kidney).

Effect of fulvic and humic acids on iron and manganese homeostasis in rats.

The objective of this study was to investigate the effects of fulvic acid (FA) and humic acid (HA) as the two main compounds of humic substances, separately on Fe and Mn homeostasis. Seventy-two male Wistar rats were randomly divided into 9 experimental groups. The control diet (AIN-93G formula) and diets supplemented with 0.1%, 0.2%, 0.4% and 0.8% HA or FA were fed for 26 days. Fe and Mn concentrations of the large intestinal content, liver, kidney, femur and hair were determined. No significant differences were observed in the production parameters. The effects of FA and HA on iron homeostasis were significantly different. FA proved to be a good iron source, and slightly increased the iron content of liver and kidney, but - up to a dietary iron level of 52.7 mg/kg - it did not influence the efficiency of iron absorption. Above a dietary iron level of 52.7 mg/kg down-regulation of Fe absorption can be assumed. HA significantly stimulated the iron uptake and there was no down-regulation of Fe absorption up to 0.8% dietary HA supplementation level (61.5 mg Fe/kg diet). In the HA groups the iron content of the liver and kidney decreased significantly, suggesting that in spite of the better Fe absorption, the HA-Fe complex does not provide iron to the investigated organs. Neither FA nor HA supplementation influenced the Fe content of the femur and hair and slightly decreased the Mn concentration in the large intestinal content. This effect was significant (with a 22.7% Mn concentration decrease) only at the HA supplementation rate of 0.8%. Neither FA nor HA influenced significantly the Mn concentrations of the liver, kidney and femur. The Mn concentration of the hair in rats receiving FA- or HA-supplemented diets was higher than in the control rats; however, this result needs further confirmation.

Effect of arginine or glutamine supplementation on production, organ weights, interferon gamma, interleukin 6 and antibody titre of broilers.

The objective of this study was designed to test whether supplementation of the diet with arginine (Arg) or glutamine (Gln) or their combination influences the production, organ weights and humoral immune response of broilers. A total of 432 one-day-old male Ross 308 broiler chickens were divided into 6 treatment groups: control, Arg-0.5%, Arg-1%, Gln-0.5%, Gln-1% and Arg-0.5%+Gln-0.5%. Drinking water and feed were provided ad libitum. On day 18 of the experiment 50% of chickens in each treatment group were immunised with bovine serum albumin. Ten and 21 days after immunisation blood samples were collected to determine the anti-albumin IgY titre, interleukin 6 (IL6) and interferon gamma (IFNG) and to measure the weight of the liver, spleen, bursa of Fabricius and thymus. Arg or Gln supplementation of the diets influenced neither the production nor the organ weights until 18 days of age. Between 18 and 39 days of age both Arg (0.5% and 1%) and Arg + Gln supplementation improved the feed conversion ratio (FCR) by 3.7%, 6.3% and 4.9%, respectively, while Gln-1% worsened it by 15%. Immunisation slightly (-0.79%) depressed the body weight gain of broilers fed the control diet, which was significantly improved by both Arg (0.5 or 1%) and Arg + Gln supplementation. Immunisation increased the weight of the spleen, bursa and thymus and decreased that of the liver. Supplementation with 1% Gln depressed (-5.13%) the body weight gain of the immunised chickens but strongly stimulated the immune response. Supplementations with Arg and Gln did not influence the IL6 and IFNG level of the blood; however, on day 10 after immunisation these two parameters showed a negative correlation with each other. Regarding production, organ weights and immunity, Arg supplementation should be recommended in the grower phase, while Gln supplementation can be useful in pullets raised for egg production, where a good immune response to vaccinations is an important factor.

Effects of two dietary vitamin and mineral supplements on the growth and health of Hermann's tortoise (Testudo hermanni).

The aim of the study was to determine the long-term effects of two different vitamin and mineral supplements on the growth and health of Hermann's tortoises. Twelve one-month-old tortoises were randomly divided into two groups of six animals (group A and B). Diets were supplemented on a daily basis with two different products ("A": vit. D350 000 IU/kg, 150 g/kg Ca or "B": vit. D3, 2000 IU/kg, 148 g/kg Ca) for 12 months. Product "B" was richer in most of the vitamins. Weight and shell parameters were measured weekly. After one year animals in group B had significantly higher final body weights than those in group A (186.7 g vs. 131.6 g). The shell of the individuals in group A was firm and healthy, while all the tortoises in group B (in different levels) had weakened shells. The loss of bone tissue was not so serious to have visual signs on x-rays. High amount of vitamins (vitamin E, K, B1, 2, 6, 12, biotin) given for safety reasons and relatively low level of vitamin D3 (like in product "B") applied on a daily basis seem to be disadvantageous. The moderate metabolic bone disease that developed in group B during the experiment could be treated after the study by using the supplement "A". The authors recommend such supplements which have similar ingredients to product "A" for growing tortoises housed indoor with low or without irradiation exposure to UVB.

Effect of dietary electrolyte balance on production, immune response and mineral concentrations of the femur in broilers.

The aim of this study was to assess the age-related effects of dietary electrolyte balance (DEB) on the performance, immune response (from day 0 to 42) and macromineral content of femur ash of broilers. The DEB values of the purchased commercial broiler diets were modified with the addition of NH4Cl or NaHCO3 to formulate the diets (DEB 325, 250, 175, 100, 25 and -50 mmol/kg) for this investigation. A total of 396 chickens were divided into 6 treatment groups and fed with the experimental diets for 6 weeks. During the first two weeks of life, DEB did not influence feed intake and body weight gain; however, by the 21st day of age DEB 175 and between 22 and 42 days of age DEB 250 mmol/kg gave significantly better results than the control. DEB did not affect the macromineral concentrations of bone ash. The immune response of broilers on low DEB (< 175 mmol/kg) was faster and more intensive than that of chickens on diets with medium or high DEB (> 175 mmol/kg). It can be concluded that the optimal DEB value required for the best body weight gain is significantly influenced by the age of broilers. Our results call attention to the discrepancy between the decreasing DEB level of commercial broiler diets and the age-related increase of 'electrolyte requirements' of broilers. It is also interesting that DEB may influence not only the performance but also the immune response of broilers.