W.H. Hendriks’s research while affiliated with Wageningen University & Research and other places

Housefly ( Musca domestica L.) larvae can convert animal manure into valuable protein and fat but little is known about their nutritional requirements. We assessed the effects of differential starch content in unsterilised (UE) and heat sterilised (SE) chicken excreta on larval performance and bioconversion. Gelatinized corn starch was added to excreta resulting in 11 diets with 0 to 50% starch of dry mass. Individual larval mass increased from (mean ± SD) 12 ± 0.2 (UE) and 13 ± 0.4 (SE) mg at 0% starch up to 18 ± 0.4 (UE) and 18 ± 0.5 (SE) mg at 15% starch and decreased to 5 ± 0.4 (UE and SE) mg in 50% starch. Higher starch concentrations resulted in non-normal distributions of individual larva mass. Larval wet yield showed a curvilinear relation with starch content, with maxima of 39 ± 2.3 g in UE at 10% starch, and 43 ± 2.8 g in SE at 15% starch. The decrease in yield after the maxima was faster in UE compared to SE. Larval survival was highest in 0% starch, 80 ± 8% (UE) and 72 ± 13 % (SE), linearly decreasing to 14 ± 7% (UE) and 18 ± 3% (SE) in 50% starch. Dry matter bioconversion increased from 4 ± 0.1% (UE) and 4 ± 0.3% (SE) in 0% starch to 6 ± 0.2 in UE with 10% starch and 7 ± 0.3 in SE with 15% starch, decreasing to close to 0 in 50% starch. Highest nitrogen bioconversion was 15 ± 0.5% in UE with 10% starch and 15 ± 0.5% in SE with 15% starch. Optimal starch inclusions increased nitrogen bioconversion with 40% (UE) and 100% (SE) compared to pure excreta. Finally, around 20 to 25% starch uric acid and ammonia contents, pH, and diet residue C/N decreased, indicating a tipping point. In conclusion, adding starch to chicken excreta can substantially increase larval yield and bioconversion while reducing ammonia content in the substrate residue.

Omitting or shortening the dry period may result in a fairly constant ration throughout the transition period of dairy cows, reducing the need for adaptation of cow metabolism and rumen function to a new lactation. The objective of this study was to determine the effect of dry period length on rumen adaptation and cow metabolic state during the transition period. Twelve pregnant, rumen-cannulated Holstein Friesian dairy cows at the end of their first lactation were assigned to one of 3 treatments: a conventional (60 d), short (30 d) or no dry period (0 d). At dry-off, cows received a dry cow ration until calving. Lactating cows received a lactation ration. Cows were monitored from 8 wk before calving until 8 wk after calving for milk yield and dry matter intake (DMI). Rumen biopsies were taken from 3 locations in the rumen at 60, 40 and 10 d before calving and 3, 7, 14, 28 and 56 d after calving to assess papillae dimensions. Blood was sampled weekly from 3 wk before until 8 wk after calving, and liver biopsies were taken at wk −2, wk 2 and wk 4 relative to calving. Prepartum, DMI and milk yield were greater for cows with a short or no dry period, compared with cows with a conventional dry period. Postpartum, DMI was greater for cows with a short dry period compared with cows with a conventional dry period. Plasma glucose concentration was greater for cows without a dry period, compared with the other dry period lengths postpartum. Plasma concentrations of nonesterified fatty acids and β-hydroxybutyrate, and liver triglyceride content, did not differ among dry period. Rumen papillae differed in size based on biopsy location, but there was no interaction between biopsy location and the effect of dry period length. Rumen papillae surface area for cows managed for a 30 d or 60 d dry period decreased toward calving. At 40 d prepartum, papillae surface area was greater for short and no dry period treatment compared with a conventional dry period. At 10 d prepartum, papillae surface area was greater for the no dry period treatment compared with both other treatments, and this difference was still present 3 d postpartum. Cows managed for a short dry period showed faster increase in papillae dimensions after calving compared with cows managed for a conventional dry period. From d 28 onwards, no differences in papillae surface area were observed. The faster rumen adaptation postpartum may be related to the increased DMI during the first weeks postpartum for cows managed for a short dry period. However, this did not result in improved metabolic status or milk yield. The results from the present study demonstrate that the dietary changes related to a conventional dry period length affected rumen papillae development, not only prepartum but also early postpartum. Further optimization of dry period length as well as dietary composition throughout the transition period may support cows in their adaptation to a new lactation.

Enhanced dietary Ca intake linearly increases intestinal Ca absorption in pigs, but not in broilers, suggesting potential differences in whole body Ca homeostasis. To determine the role of kidney in Ca homeostasis in these species, we varied in growing pigs in experiment ( Exp ) 1, the dietary Ca content 2.0 vs. 9.6 g/kg and phytase 0 vs. 500 FTU/kg, in broilers, in Exp 2 the dietary Ca/retainable P from 1.3 to 2.8 and phytase 0 vs. 1000 FTU/kg, and in Exp 3 dietary Ca/P from 0.50 to 1.75. Increasing dietary Ca reduced renal mRNA expression of Ca-related transporters (TRPV5, TRPV6, CaBP-D28k, NCX1) and tight junctions (CLDN-12 and -16) in pigs, indicating Ca reabsorption was reduced to maintain Ca homeostasis. In broilers (Exp 2), high dietary Ca increased renal TRPV6, CaBP-D28k and CLDN-2 mRNA, indicating an increased capacity for Ca reabsorption. Moreover, the effect of dietary Ca was enhanced by inclusion of dietary phytase in pigs but reduced in broilers. Furthermore, increasing dietary Ca upregulated PiT-1 while phytase downregulated XPR1 mRNA expression in pigs; in broilers dietary Ca downregulated renal mRNA expression of NaPi-IIa, PiT-1, PiT-2 and XPR1, while phytase downregulated NaPi-IIa but upregulated PiT-2 and XPR1 mRNA expression. In Exp 3, Ca/P effect on transporter mRNA expression was largely consistent with Exp 2. In conclusion of this study, together with previously measured data about Ca and P homeostasis, in pigs the kidneys play a more regulatory role in Ca homeostasis than in broilers where the intestine is more important for regulation.

The present study aimed to confirm the previously reported ‘recovery’ effect to a challenging diet (CD) of a Lactobacilli‐ based probiotic (Pro) and its derived postbiotic (Post) in broilers. Identical diet compositions were used, and observations were extended to a second CD diet. A completely randomised block design of 2 × 3 treatment groups with two CDs and three additive conditions (Control, Pro, Post) was used. One additional group received a standard diet (SD). The study involved 1600 one‐day‐old Ross 308 male broilers. All diets, fed from d1 to 35, were formulated to contain identical nutrients levels, with CDs formulated to be greater than SD in nonstarch polysaccharides using rye and barley (Rye CD) or dry distiller grains with soluble, sunflower and rapeseed meal (DDGS CD). Growth performance parameters, footpad lesions (FPL) score and plasma Ca, P and uric acid concentrations were measured. Compared to SD, birds fed Rye CD and DDGS CD had a higher 1–35 days feed conversion ratio (+3.4 and +4.1%, respectively), due to a higher feed intake for Rye CD (+2.9%) and a lower body weight for DDGS CD (−4.1%). An effect of additive was restricted to Rye CD where Post depressed BW at d28 and d35 (−3.7 and −2.4%, respectively). Compared to Rye CD, DDGS CD lowered plasma Ca/P at d21 (−9.0%) and d35 (−8.1%) and uric acid at d21 (−26%). Pro increased plasma Ca in Rye CD at d21 (+12%) and Post decreased plasma uric acid in DDGS CD at d35 (−25%). All other plasma parameters were not affected. The previously observed recovery effect of a commercial probiotic and postbiotic were not reproducible under highly similar growth conditions, which suggests that both may have specific physiological effects which are only expressed under specific circumstances.

This study investigated the diet–additive interactions of a Lactobacilli-based probiotic (Pro) and postbiotic (Post) on immune parameters and cecal microbiota composition, with subsequent effects on the metabolome in broilers. A completely randomized block design was employed with 2 diets [standard (SD), and challenge (CD)] and 3 additive conditions (Control, Pro, Post) involving 1,368 one-day-old male Ross 308 broilers equally distributed among 36 pens in a 42 d study. Diets were formulated to contain identical nutrient levels, with CD higher than SD in non-starch polysaccharide content by including rye and barley. Total non-specific serum Ig A, M and G concentrations were determined weekly from d14 to 35. Following vaccination, titres of specific antibodies binding Newcastle disease virus (NDV) and infectious bursal disease virus (IBDV) were measured. Microbiota composition was analyzed by 16S rRNA gene sequencing at d14 and 35, and α- and β-diversity indexes (Observed, Chao1, Bray, Jaccard) were calculated. Cecal short-chain fatty acids and the semi-polar metabolome were determined in the Control SD and all CD groups at d35. At d35, a diet–additive interaction was observed on cecal microbiota composition. Within SD, Pro and Post did not affect operational taxonomic units (OTU) abundance (adjusted-P > 0.05) and diversity indexes (P > 0.05). Within CD, Pro and Post affected the relative abundances of 37 and 44 OTUs, respectively (adjusted-P < 0.05), with Post but not Pro affecting β-diversity indexes (P = 0.041 and 0.064 for Bray and Jaccard, respectively). Within CD, Post increased cecal acetate (21%; P = 0.007) and butyrate (41%; P = 0.002) concentration and affected the concentration of 2 metabolites (adjusted-P < 0.05), while Pro affected 240 metabolites (adjusted-P < 0.05). No diet–additive interactions were observed on serum Ig (P > 0.05), except for IgM at d14 (P = 0.004). Diet composition, but not the additives, affected immune status parameters. The Pro and Post affected cecal microbiota composition only under dietary challenging conditions as previously reported for growth.

Fermentation of dietary and endogenous protein in the hindgut is generally considered detrimental to the health of pigs. We investigated the in vitro fermentation potential of porcine endogenous protein in ileal digesta and colonic mucus, using a N-free buffer with an excess of fermentable carbohydrates. Urea, whey protein isolate (WPI, positive control), WPI hydrolysate (WPIH), and combinations of the latter two were used to validate the assay. A new biphasic model, including a linear end simulation, fitted to the gas production data over a 48-h period identified the time point when substrate fermentation ended. A higher degree of hydrolysis of WPI resulted in a higher maximum gas production rate (Rmax, P < 0.01). Differences in Rmax and the time required to reach Rmax were observed among ileal digesta samples, with Rmax increasing with the insoluble protein content, and highest Rmax occurring with colonic mucus samples (P < 0.05). The endogenous proteins entering the large intestine of pigs can ferment more rapidly compared to highly soluble and digestible protein sources, with Rmax positively correlated with decreasing solubility of endogenous nitrogenous components.

This study evaluated the protein quality of small mammalian prey and its body organs by analyzing amino acid (AA) composition and digestibility of wild adult rats and their body organs (skin/fur, bone, muscle, intestine, liver, kidney, spleen, brain, heart, and lung) utilizing an in vitro digestion method. The average dry matter (DM) digestibility of whole rats was 89.9%. The digestibility of total AA (TAA), total indispensable AA (TIAA), and total dispensable AA (TDAA) in whole rats was 85.6, 87.0, and 87.6%, respectively. Differences in DM digestibility were observed among rat organs, ranging from 59.0% in bone to 99.8% in muscle (P < 0.001). Highly digestible organs generally exhibited AA digestibility exceeding 90%, except for cysteine (Cys) in the intestine and kidney (83.8% and 88.9%, respectively). The digestibility of AAs in skin/fur ranged from 19.7% for Cys to 81.0% for glycine (Gly). In bone, the digestibility spanned from 56.9% for Gly to 81.1% for tyrosine (Tyr). Additionally, examining the digestible indispensable AA score (DIAAS) gives us an idea of the protein quality of small mammalian prey and their body organs. Our results complement information on AA supply and digestion during prey ingestion by felids.

The relationship between DM yield/cutting and the fermentable organic matter (FOM) content of tropical grasses was appropriately investigated to re-assess optimal grass maturity to feed dairy cattle. Nine different grass species belonging to the genera Brachiaria spp. (Mulato II, Ruzi), Panicum spp. (Guinea, Hamil, Mombasa, TD58), and Pennisetum spp. (King, Napier, VA06) were chemically analysed and subjected to an in vitro gas production (IVGP) test. For 72 h, gas production (GP) was continuously recorded with fully automated equipment. A triphasic, nonlinear, regression procedure was applied to analyse GP profiles. Across all the grasses, it was found that the neutral detergent fibre (NDF) contents increased with increasing maturity of the grass while the CP contents decreased with increasing NDF contents. In all nine grasses, digestible organic matter (dOM) was significantly affected by the week of cutting but IVGP was similar between the weeks of cutting in Ruzi, Hamil, Mombasa, and Napier grasses. Except for Guinea grass, the lowest dOM values were found when the grasses were cut after ≥5 weeks of regrowth. Harvesting grass one or two weeks earlier than the normal cutting time is a practically relevant intervention in increasing forage quality and productivity of dOM and fermentation potential.

Context A great body of evidence is available on the in vitro efficacy of white-rot fungi (WRF) to degrade lignin in fibre-rich biomass (e.g. wheat straw, wood chips and rice straw (RS)) and improve the biomass’ nutritive value for ruminants. Aims Determining the impact of incubation temperature of three WRF to improve the nutritional value of rice straw. Methods Growth of Ceriporiopsis subvermispora, Lentinula edodes and Pleurotus eryngii on RS for 26 days at the following six temperature regimes: continuous at 24°C, 30°C, 35°C and 40°C, and 3 days at 35°C and 40°C, with subsequent days at 24°C. In a follow-up experiment, improvement in fermentability in buffered rumen fluid of RS treated by the three WRF at 24°C and 30°C for up to 8 weeks was investigated. Key results All three fungi grew at temperatures up to 35°C, with no growth observed at 40°C, with C. subvermispora being more temperature sensitive. There were significant differences in cellulose, hemicellulose and lignin degradation of RS at 24°C and 30°C, with C. subvermispora degrading 69% and 90% of the hemicellulose and lignin respectively at 30°C, greater than at 24°C (55% and 80% respectively). For L. edodes, there were significant differences in cellulose degradation between 24°C and 30°C, with 12% more degradation at 30°C, but not for hemicellulose and lignin. In vitro gas production showed no significant differences between the two incubation temperatures for either of the two fungi. Pleurotus eryngii treatment did not show any improvement in terms of in vitro gas production. Conclusions Treatment of RS with L. edodes and C. subvermispora, but not P. eryngii, is robust and temperature changes will not have a major impact on their efficacy as long as the temperature remains below 30°C. Implications Temperature during the incubation of WRF with rice straw needs to be below 30°C for this biotechnology to be applied in practice.