Impact of Agro-industrial Byproducts on Bioconversion, Chemical Composition, in vitro Digestibility, and Microbiota of the Black Soldier Fly (Diptera: Stratiomyidae) Larvae.

The interest in using byproducts from agro-food industries as a rearing substrate for insects is increasing rapidly. We investigated the influence of byproducts of vegetal origin (okara-a byproduct of soy milk production, maize distillers with solubles, brewer's grains), used as rearing diet for black soldier fly larvae (BSFL), on the following parameters: biomass production, substrate reduction (SR), nutritional profile and in vitro digestibility, and larval gut microbiota. Hen diet was used as a control substrate. The highest larval biomass was collected on maize distillers, whereas the highest SR was observed on okara. The rearing substrate affected ash, ether extract, and chitin larval content. The BSFL reared on okara were characterized by a lower lauric acid content (17.6% of total fatty acids). Diets also influenced in vitro crude protein digestibility (%) for monogastrics, with the highest values for BSFL reared on maize distillers (87.8), intermediate for brewer's grains and okara BSFL, and the lowest for hen BSFL (82.7). The nutritive value for ruminants showed a lower Net Energy for lactation for BSFL reared on hen diet than okara and dried maize distillers BSFL. The different byproducts showed an influence on the larval gut microbiota, with a major bacterial complexity observed on larvae fed with the hen diet. The neutral detergent fiber concentration of dietary substrate was negatively correlated with Firmicutes and Actinobacteria relative abundance. Insects valorized byproducts converting them into high-value larval biomass to be used for feed production. The results evidenced the effects of the tested byproducts on the measured parameters, underling the chemical composition importance on the final insect meal quality.

An In Vitro Study on the Role of Cellulases and Xylanases of Bacillus subtilis in Dairy Cattle Nutrition.

The administration of Bacilli to dairy cows exerts beneficial effects on dry matter intake, lactation performance, and milk composition, but the rationale behind their efficacy is still poorly understood. In this work, we sought to establish whether cellulases and xylanases, among the enzymes secreted by B. subtilis, are involved in the positive effect exerted by Bacilli on ruminal performance. We took advantage of two isogenic B. subtilis strains, only differing in the secretion levels of those two enzymes. A multi-factorial study was conducted in which eight feed ingredients were treated in vitro, using ruminal fluid from cannulated cows, with cultures of the two strains conveniently grown in a growth medium based on inexpensive waste. Feed degradability and gas production were assessed. Fiber degradability was 10% higher (p < 0.001) in feeds treated with the enzyme-overexpressing strain than in the untreated control, while the non-overexpressing strain provided a 5% increase. The benefit of the fibrolytic enzymes was maximal for maize silage, the most recalcitrant feed. Gas production also correlated with the amount of enzymes applied (p < 0.05). Our results revealed that B. subtilis cellulases and xylanases effectively contribute to improving forage quality, justifying the use of Bacilli as direct-fed microbials to increase animal productivity.

In vitro effects of different levels of quebracho and chestnut tannins on rumen methane production, fermentation parameters, and microbiota.

Both condensed and hydrolysable tannins (CTs and HTs, respectively) have the ability to reduce enteric CH4 production in ruminants. However, the precise mechanism of action is not fully understood. Among the proposed hypotheses are the reduction of ruminal digestibility, direct control action on protozoa, reduction of archaea, and a hydrogen sink mechanism. In this in vitro study, which simulated rumen fermentation, two additives, one containing CTs (70% based on DM) from quebracho and one with HTs (75% based on DM) from chestnut, at four levels of inclusion (2, 4, 6, 8% on an as-fed basis) were added to the fermentation substrate and tested against a negative control. Both types of tannins significantly reduced total gas (GP) and CH4 (ml/g DM) production during the 48 h of incubation. The lower GP and CH4 production levels were linked to the reduction in dry matter digestibility caused by CTs and HTs. Conversely, no significant differences were observed for the protozoan and archaeal populations, suggesting a low direct effect of tannins on these rumen microorganisms in vitro. However, both types of tannins had negative correlations for the families Bacteroidales_BS11 and F082 and positive correlations for the genera Prevotella and Succinivibrio. Regarding the fermentation parameters, no differences were observed for pH and total volatile fatty acid production, while both CTs and HTs linearly reduced the NH3 content. CTs from quebracho were more effective in reducing CH4 production than HTs from chestnut. However, for both types of tannins, the reduction in CH4 production was always associated with a lower digestibility without any changes in archaea or protozoa. Due to the high variability of tannins, further studies investigating the chemical structure of the compounds and their mechanisms of action are needed to understand the different results reported in the literature.

Impact of Rearing Strategies on the Metabolizable Energy and SID Lysine Partitioning in Pigs Growing from 90 to 200 kg in Body Weight.

The current nutrient recommendations focus on pigs fed ad libitum up to 140 kg in body weight (BW). It remains unclear whether this applies to pigs weighing above 140 kg in BW under different rearing conditions. This study aimed to estimate protein (Pd) and lipid (Ld) depositions and the metabolizable energy (ME), standardized ileal digestible lysine (SID lysine) requirement and partitioning in 224 C21 Goland pigs (90−200 kg in BW). The control pigs (C) received diets limiting ME up to 170 kg in slaughter weight (SW) at 9 months of age (SA); older (OA) pigs had restricted diets limiting ME and SID lysine up to 170 kg in SW at >9 months SA; younger (YA) pigs were fed nonlimited amounts of ME and SID lysine up to 170 kg in SW at <9 months SA; and greater weight (GW) pigs were fed as the YA group, with 9 months SA at >170 kg in SW. The estimated MEm averaged 1.03 MJ/kg0.60. An 11% increase in MEm was observed in OA pigs compared to the controls. Energy restriction had negligible effects on the estimated MEm. The marginal efficiency of SID lysine utilization for Pd averaged 0.725, corresponding to a SID lysine requirement of 9.8 g/100 g Pd.

Effect of Linseeds and Hemp Seeds on Milk Production, Energy and Nitrogen Balance, and Methane Emissions in the Dairy Goat.

The effect of whole linseeds or hemp seeds on milk production, energy and nitrogen balance, and methane emission was studied in 12 Alpine goats using respiration chambers. Diets tested were a control diet (C) and two diets supplemented with whole linseeds (L) or hemp seeds (H) at 9.3% on a dry matter (DM) basis. DM intake was similar among treatments, whereas DM and organic matter digestibility were lower for L compared to C. Milk yield (2.30 kg/d on average) and rumen fermentation profile were not affected by treatments. Treatment also did not affect the milk composition, with the exception of fat, which was higher in H and L compared to C (4.21, 3.94, and 3.20%, respectively). Oilseed supplementation caused a reduction in the concentration of de novo fatty acids (FA) (41.1, 48.8, and 64.1% of FA, for L, H, and C, respectively). Moreover, L and H diets reduced the sum of saturated FA, and increased monounsaturated FA, whereas only the L diet increased the concentration of polyunsaturated FA. Regarding methane production, and nitrogen and energy balances, no differences were registered among the diets. Our research indicates that including whole linseeds and hemp seeds in the dairy goat diet is an effective strategy for increasing milk fat content and positively modifying the milk FA composition, without a change in nitrogen and energy balances, but also without a reduction in enteric methane emission.

Effect of a Polyphenol-Based Additive in Pig Diets in the Early Stages of Growth.

The weaning period is a stressful period for the gastrointestinal tract (GIT) of piglets. This work aims to evaluate the effects of the commercial polyphenol-based product GreenFIS® on: (1) GIT health and performance of 60 weaned piglets; (2) digestibility in 18 growing pigs. Three diets were tested: a control diet (C), C plus 2.5 g of GreenFIS®/kg C (T1), and C plus 5 g of GreenFIS®/kg C (T2). After the post-weaning trial three piglets per treatment were sacrificed for the GIT histological analysis. No differences between diets were recorded in terms of growing performance or clinical and biochemical blood parameters. The GIT histological analysis did not show any indicators of inflammation for any of the groups. The feces of the two extreme treatments (C and T2) were analyzed for microbiota, revealing a greater presence of the Ruminococcus bromii group, positively associated with starch degradation, in T2. In the second experiment six pigs per treatment were randomly chosen for the digestibility study. The inclusion of GreenFIS® at both levels led to a higher fecal digestibility of gross energy (86.2%, 89.1%, and 89.5%, for C, T1, and T2, respectively) and crude protein (87.0%, 90.2%, and 90.0%). In conclusion, the additive did not improve, in the excellent experimental hygienic conditions, the gut health, but it did increase nutrient digestibility.

Use of Undigested NDF for Estimation of Diet Digestibility in Growing Pigs.

Undigested neutral detergent fibre (uNDF) is commonly used as an internal marker for the estimation of diet digestibility in ruminants. This work aimed to verify (i) whether the in vivo method with uNDF could be used to evaluate diet digestibility in growing pigs, and (ii) whether pre-treating the samples with neutral detergent solution (NDS) and α-amylase improves the accuracy of the estimates. Samples from a previously published work of two diets with known in vivo digestibility values estimated by the total faecal collection method and 16 individual samples of faeces were used. For each sample, four Ankom F57 bags were weighed. Before the incubation, two F57 bags were pre-treated with NDS and α-amylase. All the samples were incubated for 240 h in the Ankom DaisyII incubator and then analysed for their uNDF contents. Dry matter, organic matter, and neutral detergent fibre digestibilities were estimated using the uNDF contents, and the results were compared with those of the former study. The digestibility values obtained using the uNDF method with pre-treatment were not statistically different from those determined with the total faecal collection. On the contrary, the uNDF method without the pre-treatment could not satisfactorily predict the digestibilities of pig diets.

The Effects of Substituting Dietary Soybean Meal with Maize Grain on Milk Production in Dairy Goats.

In view of better environmental sustainability, livestock diets must not exceed protein requirements, as often happens with lactating goats reared in semi-intensive systems. The aim of this experiment was to verify in real-breeding conditions the influence of two diets with different protein contents (% crude protein (CP) on dry matter (DM)): 16.0 (high-protein diet; HP) vs 12.2 (low-protein diet; LP) on milk production in dairy goats. The diets differed only in the replacement-in the LP diet-of 250 g soybean meal with 250 g maize grain meal. Twenty-three Alpine goats were divided into two groups and used in a cross-over feeding trial for 2 months. Animals were weighed at the beginning of each month of the trial, and feed intake and milk yield and composition were recorded weekly. HP and LP did not differ statistically for milk yield and composition (3.32 vs 3.42 kg milk/d, 3.21% vs 3.27% fat, 3.31% vs 3.27% protein for HP and LP, respectively), but the HP diet determined a higher milk urea content (51.2 vs 36.6 mg/dL, p < 0.001) and a worse efficiency of nitrogen utilization (28.0% vs 37.2%). In conclusion, the LP diet resulted in a reduction of urinary nitrogen excretion by 28% and of the feed cost by about 10%.

Comparison of Faecal versus Rumen Inocula for the Estimation of NDF Digestibility.

Cow faeces have been investigated as alternative inoculum to replace rumen fluid to determine neutral detergent fibre (NDF) digestibility (NDFD). Aims of this study were to estimate: (1) the NDFD (48 h) of feed ingredients using a rumen inoculum in comparison with faecal inocula from cows fed diets with different forage basis; (2) the undigestible NDF (uNDF) at 240 and 360 h with ruminal fluid and faecal inocula from lactating cows fed two different diets. At 48 h incubation, the NDFD was affected both by feed and type of inoculum (p < 0.01) and by their interaction (p = 0.03). Overall, the mean NDFD was higher for rumen inoculum than for faecal inocula (585 vs. 389 g/kg NDF, p < 0.05), and faecal inoculum obtained from cows fed hay-based diets gave lower NDFD than those from cows fed maize silage (367 vs. 440 g/kg, p < 0.05). At long incubation times, the average uNDF was affected by substrate, inoculum and incubation time (p < 0.01), but not by their interactions. For each inoculum, significantly lower values were obtained at 360 than at 240 h. Regressions between uNDF with rumen and with the tested faecal inocula resulted in r2 ≥ 0.98. Despite the differences at 48 h, the uNDF showed that faecal inoculum could replace rumen fluid at longer incubation times.

Blood parameters in fattening pigs from two genetic types fed diet with three different protein concentrations.

The study aimed to evaluate possible differences between two genetic groups (GG) of pigs, fed diets varying in dietary CP level, in hematological and biochemical plasma profiles. The study was carried out in an experimental farm and involved 36 barrows (average BW 129 ± 11 kg) from two GG: group A (18 Italian Duroc boars × Italian Large White sows) and group D (18 DanBred Duroc), fed three experimental diets: a conventional diet and two low-protein diets (LP1 and LP2). A digestibility/balances trial was carried out on 12 pigs A and 12 pigs D that were housed individually in metabolic cages during four digestibility/balances periods. The experimental design was a factorial design, with 3 diets × 2 GG × 4 periods. The experiment lasted 56 d. Blood was sampled from jugular vein in the morning before feed distribution from all barrows in pens at the start and the end of the experimental period; a supplementary blood sample was collected from the 24 pigs at the end of the four digestibility periods (six pigs per period). Blood was analyzed for hematological and biochemical parameters and serum protein profile using automated analyzers. The GG D showed lower white blood cells (WBC), lymphocyte, and monocyte counts than A group. The GG affected several plasma metabolite concentrations: triglycerides, creatinine, Cl, Fe, alkaline phosphatase, and tartrate-resistant acid phosphatase activities were higher in D groups, while urea, albumin, Ca, Na, total bilirubin, and albumin as percentage of total protein were lower than A group. On the contrary, the dietary protein level neither affects WBC nor their populations; only a trend was reported for erythrocytes (red blood cell) and platelets. The diet affected only plasma urea and total bilirubin concentrations.

Effects of Cocoa Husk Feeding on the Composition of Swine Intestinal Microbiota.

A two-diet/two-period change over experiment was performed to investigate the effects of cocoa husks, as a source of dietary fiber and polyphenols, on pig intestinal microbial composition. Six pigs were fed a conventional cereal-based diet or a diet obtained by substitution of 7.5% of the conventional diet with cocoa husks for 3 weeks. Experimental diets were isoproteic and isoenergetic. At the end of each 3 week testing period, samples of fresh feces were collected and analyzed for microbial composition by fluorescence in situ hybridization. Cocoa husks did not affect feed intake, weight gain, and feed efficiency. Analysis of fecal microbial populations, grouped by phyla, showed a decrease of Firmicutes and an increase of Bacteroidetes in cocoa husk-fed pigs. Particularly, cocoa husks reduced fecal populations of the Lactobacillus-Enterococcus group and Clostridium histolyticum and increased the Bacteroides-Prevotella group and Faecalibacterium prausnitzii, suggesting a potential for cocoa husks in the improvement of intestinal microbial balance.

Effects of a selection of additives on in vitro ruminal methanogenesis and in situ and in vivo†NDF digestibility.

The effects of 18 essential oils, yeast, Quebracho tannin and Quillaja saponin on ruminal methane and gas production (GP) were studied in vitro. A lactating cow diet was incubated with rumen inoculum. Doses of the additives (mg/L) were: essential oils = 500; tannin = 67; yeast = 8.35 and 16.7; and saponin = 300. Lemongrass, estragole, eugenol, geraniol, limonen, thyme oil and thymol produced less gas (overall mean 33.8 mL/200 mg dry matter (DM)) than control (43.6 mL/200 mg DM; P < 0.001). Methane produced (mL/200 mg DM) by guaiacol (10.7), lemongrass (9.6), limonene (11.4), thyme oil (10.9) and thymol (2.1) was lower than control (12.5) (P < 0.001). Methane percentage on total GP was lower (P < 0.001) for cinnamic alcohol (25.4), guaiacol (24.5), thymol (19.7) and vanillin (26.3) than control (28.8). In a second experiment, thymol, guaiacol and yeast were added to the diet of dry fistulated cows to determine in situ neutral detergent fiber digestibility (NDFD) of six forages and in vivo dietary NDFD. Thymol and yeast decreased in situ NDFD after 24 h (33.9% and 33.5% vs. 38.1%; P = 0.008). Thymol decreased in vivo total tract NDFD (40.8% vs. 51.4%; P = 0.02). Differences in GP and methane levels were registered within classes of additives. A careful selection of additives may allow for the manipulation of ruminal fermentation.