Short-Term Housing in Metabolic Caging on Measures of Energy and Fluid Balance in Male C57BL/6J Mice (Mus musculus)

Metabolic caging is an important tool for quantitative urine and feces collection in rodents, although significant limitationsand problems accompany its use. Despite strong opinions among investigators regarding the effects of metabolic caging onenergy and fluid homeostasis, careful quantitative analysis of the impact of this caging type—particularly when used for mice—is lacking. The current study assessed the effects of metabolic caging, with or without modifications such as plastic platform inserts, on ingestive behaviors, energy expenditure, accuracy of urine and fecal collection, and ambulatory activities in male C57BL/6J mice. Housing mice in metabolic cages, regardless of platform inclusion, increased energy expenditure without modifying food intake, presumably due to the inability of mice to perform normal thermoregulatory behaviors (burrowing and huddling). Surprisingly, mice in metabolic cages actively avoided platforms, and the inclusion of platforms modified the behavior of the mice and had position-dependent effects that reduced the accuracy of urine collection. Moving mice from cohousing to individual housing in home cages also increased ingestive behaviors and energy expenditure. We conclude that single housing of male C57BL/6J mice increases energy expenditure, that this increase is potentiated in metaboliccaging conditions, and that platforms in metabolic cages alter mouse behavior and urine collection. Additional future workis needed to determine the potential benefits of using higher ambient temperature for studies of mice in metabolic cagingand whether the above effects occur in females and other strains of mice and other rodent species.

Comparison of Fecal Collection Methods on Variation in Gut Metagenomics and Untargeted Metabolomics

The choice of fecal collection method is essential for studying gut microbe-human interactions in large-scale population-based research. In this study, we examined the effects of fecal collection methods and storage time at ambient temperature on variations in the gut microbiome community composition; microbial diversity metrics at the species, gene, and pathway levels; antibiotic resistance genes; and metabolome profiling.

Influence of a novel consensus bacterial 6-phytase variant on mineral digestibility and bone ash in young growing pigs fed diets with different concentrations of phytate-bound phosphorus

A 20-d experiment was conducted to test the hypothesis that phytase increases nutrient digestibility, bone ash, and growth performance of pigs fed diets containing 0.23%, 0.29%, or 0.35% phytate-bound P. Within each level of phytate, 5 diets were formulated to contain 0, 500, 1,000, 2,000, or 4,000 phytase units (FTU)/kg of a novel phytase (PhyG). Three reference diets were formulated by adding a commercial Buttiauxella phytase (PhyB) at 1,000 FTU/kg to diets containing 0.23, 0.29, or 0.35% phytate-bound P. A randomized complete block design with 144 individually-housed pigs (12.70 ± 4.01 kg), 18 diets, and 8 replicate pigs per diet was used. Pigs were adapted to diets for 15 d followed by 4 days of fecal collection. Femurs were collected on the last day of the experiment. Results indicated that diets containing 0.35% phytate-bound P had reduced (P < 0.01) digestibility of Ca, P, Mg, and K compared with diets containing less phytate-bound P. Due to increased concentration of total P in diets with high phytate, concentrations, apparent total tract digestible P and bone ash were increased by PhyG to a greater extent in diets with 0.29 or 0.35% phytate-bound P than in diets with 0.23% phytate-bound P (interaction, P < 0.05). At 1,000 FTU/kg, PhyG increased P digestibility and bone P more (P < 0.05) than PhyB. The novel phytase increased (P < 0.01) pig growth performance, and pigs fed diets containing 0.35 or 0.29% phytate-bound P performed better (P < 0.01) than pigs fed the 0.23% phytate-bound P diets. In conclusion, the novel phytase (i.e., PhyG) is effective in increasing bone ash, mineral digestibility, and growth performance of pigs regardless of dietary phytate level.

Apparent digestibility, fecal particle size, and mean retention time of reduced lignin alfalfa hay fed to horses

Reduced lignin alfalfa (Medicago sativa L.) has the potential to provide a higher quality forage source for livestock by improving forage digestibility. This study was conducted to evaluate apparent digestibility when feeding reduced lignin and non-reduced lignin alfalfa hay to adult horses, and to examine mean fecal particle size (MFPS) and mean retention time (MRT) between alfalfa forage types. In 2017, reduced lignin (‘54HVX41’) and non-reduced lignin (‘WL355.RR’) alfalfa hay was harvested in Minnesota at the late-bud stage. Alfalfa hays were similar in crude protein (CP; 199 g kg -1), neutral detergent fiber (NDF; 433 g kg -1), and digestible energy (DE; 2.4 Mcal kg -1). Acid detergent lignin (ADL) concentrations were lower for reduced lignin alfalfa hay (74 g kg -1) compared to non-reduced lignin alfalfa hay (81 g kg -1). Dietary treatments were fed to six adult, stock-type horses in a crossover study. Experimental periods consisted of a 9-d dietary adaptation phase followed by a 5-d total fecal collection phase, during which horses were housed in individual boxstalls and manure was removed on a continuous 24-h basis. At 12-h intervals, feces were thoroughly mixed, subsampled in duplicate, and used for apparent digestibility and MFPS analysis. On day 2 of the fecal collection phase, horses were fed two indigestible markers, cobalt (Co) and ytterbium (Yb), which were fed as Co-EDTA and Yb-labelled NDF residue, respectively. Additional fecal samples were taken at 2-h intervals following marker dosing until 96-h post-dosing to evaluate digesta MRT. Data was analyzed using the MIXED procedure of SAS, with statistical significance set at P ≤ 0.05. Dietary treatment (i.e., alfalfa hay type) was included as a fixed effect, while experimental period and horse were considered random effects. Dietary treatments were similar in dry matter intake (DMI; 1.6% BW) and time to consumption (TTC; 7.6 h). Apparent dry matter digestibility (DMD) was greater for reduced lignin alfalfa (64.4%) compared to non-reduced lignin alfalfa (61.7%). Apparent CP and NDF digestibility did not differ between dietary treatments, averaging 78% and 45%, respectively. Dietary treatments were similar in MFPS (0.89 mm) and MRT for both liquid (23.7 h) and solid (27.4 h) phase material. These results indicate an improvement in DMD for reduced lignin alfalfa hay when fed to adult horses, with no change in forage consumption, fecal particle size, or digesta retention time.

60 Effect of a Novel Consensus Bacterial 6-phytase Variant on Mineral Digestibility and Bone Ash in Young Growing Pigs Fed Diets with Different Concentrations of Phytate

An experiment was conducted to test the hypothesis that increasing levels of phytase increases mineral digestibility and bone ash by pigs fed diets containing 0.23%, 0.29%, or 0.35% phytate-P. Within each level of phytate, 5 diets were formulated based on corn, soybean meal, and canola meal to contain 0, 500, 1,000, 2,000, or 4,000 phytase units (FTU)/kg of a novel consensus bacterial 6-phytase variant (PhyG). In addition, 3 reference diets were formulated by adding a commercial Buttiauxella phytase (PhyB) at 1,000 FTU/kg to the 3 diets containing no PhyG. A randomized complete block design with 144 pigs (12.70 ± 4.01 kg), 18 diets, and 8 replicate pigs per diet was used. Pigs adapted to diets for 15 d followed by 4 d of fecal collection. Femurs were collected on the last day. Data were analyzed as a 3 × 5 factorial with 3 levels of phytate-P and 5 levels of phytase, and contrast statements were used to compare 1,000 FTU of PhyG with PhyB. Pig was the experimental unit. Diets containing 0.35% phytate-P had reduced (P < 0.01) apparent total tract digestibility (ATTD) of Ca, P, Mg, and K compared with diets containing 0.23% or 0.29% phytate-P, but inclusion of phytase increased (P < 0.01) ATTD of Ca, Na, and K (Table 1). Phytase increased ATTD of P and Mg, but to a greater extent in diets with 0.23 or 0.29% phytate-P than in diets with 0.35% phytate-P (interaction, P < 0.05). Phytase increased bone ash, but to a greater extent if there was 0.35 rather than 0.23 or 0.29% phytate-P in the diets (interaction, P < 0.05). PhyG increased ATTD of P more (P < 0.05) than PhyB. In conclusion, the novel consensus phytase is effective in increasing bone ash and ATTD of Ca, P, Na, Mg and K.

PSVIII-30 Reduced-lignin alfalfa digestibility and effects on performance of growing beef steers

Novel alfalfa varieties have been developed to have less lignin by genetic modification, (HarvXtra, Forage Genetics International) and by conventional breeding, (HiGest 360, Alforex Seeds). Second crop (d 29) of these alfalfas and a control, LegenDairy XHD (Winfield Solutions LLC), were harvested as high moisture wrapped bales (45.9–51.6 % DM) at the Arlington Agricultural Research Station (AARS) located near Arlington, WI, on July 5, 2017. The objectives of these experiments were to characterize novel reduced-lignin alfalfa varieties, assess their effects on growth of beef steers, and determine digestibilities using a total fecal collection trial. Treatments were fed ad libitum as alfalfa baleage to 300 kg (initial weight) black-hided beef steers, (n = 72, 4 pens/treatment, 83 d). Steers were fed solely alfalfa baleage and offered a trace mineral salt block by way of fence line feed bunks. Alfalfa lignin values were 7.56, 7.18, and 6.3% DM (P = 0.34) for LegenDairy, HiGest and HarvXtra, respectively. Steers gained 0.94, 1.00, and 1.07 kg hd-1 d-1 (P = 0.25) for LegenDairy, HiGest and HarvXtra, respectively. The same harvested alfalfa was used in a total collection fecal trial with fecal collection bags (Table 1). Numerical differences between alfalfa digestibilities were observed but no significant treatment effects were detected. Total tract NDF digestibilities (TTNDFD) for harvested alfalfas were 33.9, 35.0 and 40.3 % NDF (P = 0.079) for LegenDairy, HiGest and HarvXtra, respectively. Alfalfa lignin concentration differences were not detected through acid detergent-lignin analysis of harvested bales. While the ranking of lignin concentrations, digestibilities, and growth rates followed prevailing logic, alfalfa variety treatment effects were not detected. Experimental designs with greater sensitivity should be implemented in the future.

Effects of Collection Durations on the Determination of Energy Values and Nutrient Digestibility of High-Fiber Diets in Growing Pigs by Total Fecal Collection Method

This study was conducted to evaluate the effect of collection durations on the energy values and nutrient digestibility of high-fiber diets in growing pigs with a time-based total fecal collection method. A total of 24 barrows (body weight (BW): 31.1 ± 1.5 kg) were allotted to a completely randomized design with three diets. Diets included a corn–soybean meal (CSM) basal diet and two additional diets containing 20% sugar beet pulp (SBP) or defatted rice bran (DFRB) by replacing corn, soybean meal, and soybean oil in the CSM diet, respectively. Each diet was fed to eight barrows for a 7-day adaptation period followed by a 7-day total feces and urine collection period. The 7-day collection duration was divided into three collection phases, namely, phase 1 (days 8 to 11), phase 2 (days 11 to 13), and phase 3 (days 13 to 15). Then, similar portions of feces and urine from the different collection phases were composited into three additional samples (days 8 to 11, days 8 to 13, and days 8 to 15, respectively). The results showed that the digestible energy (DE), metabolizable energy (ME), and apparent total tract digestibility (ATTD) of gross energy (GE) and nutrient in experimental diets decreased linearly as the collection durations increased from a 3-day to a 7-day collection (p < 0.05). However, there were no differences in the energy values, GE, and nutrient digestibility of diets and of high-fiber ingredients between the 5-day and 7-day collection durations. In conclusion, this study suggests that a 5-day collection duration is adequate to determine the energy values and nutrient digestibility of high-fiber diets containing SBP or DFRB in growing pigs by the time-based total fecal collection method.

PSIV-13 Supplemental phytase increases phosphorus digestibility in pigs regardless of phytase source or feed pelleting

Two experiments were conducted to investigate the effects of phytase source and feed pelleting on digestibility of dry matter (DM), crude protein, organic matter (OM), and phosphorus (P) with different doses of phytase in pigs. In Exp. 1, ten barrows (31.4 ± 3.5 kg of BW) were individually housed in metabolic crates and allotted to a replicated 5 × 6 Latin square design with 5 diets and 6 periods. In Exp. 2, ten barrows (28.2 ± 3.2 kg of BW) were individually housed in metabolic crates and allotted to a replicated 5 × 5 Latin square design with 5 diets and 5 periods. Each period lasted 10 d consisted of a 5-d adaptation and a 5-d collection periods and the marker to marker method was used for fecal collection. In both experiments, a basal diet was prepared based on corn and soybean meal without phytase or inorganic P. Four additional diets were prepared in a 2 × 2 factorial treatment arrangement with 2 phytase sources (Buttiauxella spp. or Escherichia coli) and 2 feed forms (mash or pellet). Both experiments employed the same treatments but had different supplemental phytase doses (500 and 1,500 FTU/kg in Exp. 1 and 2, respectively). In Exp. 1, supplemental phytase increased standardized total tract digestibility of P (66.1 vs. 51.7%; P &lt; 0.001) with no effects of phytase source or feed pelleting. Feed pelleting increased digestibility of DM, crude protein, and OM (P &lt; 0.001). In Exp. 2, supplemental phytase increased standardized total tract digestibility of P (72.8 vs. 44.8%; P &lt; 0.001) with no effects of phytase source or feed pelleting. Feed pelleting increased digestibility of DM and OM (P &lt; 0.001). Taken together, supplemental phytase at 500 and 1,500 FTU/kg increases P digestibility regardless of phytase source or feed pelleting.

PSVII-2 Influence of source and concentration of phosphorus on apparent ileal digestibility and apparent total tract digestibility of phosphorus in growing pigs

A study was conducted to examine the influence of source and concentration of phosphorus (P) on the apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of P in growing pigs. Six diets were formulated in a 2 × 3 factorial arrangement with soybean meal (SBM) or corn distillers’ dried grain with solubles (DDGS) as sole sources of dietary P, and concentration of P at 2.0, 2.5 or 3.0 g/kg. Eighteen cannulated pigs (initial BW = 40 ± 5 kg) were allotted to triplicate 6 × 3 incomplete Latin square design with 6 diets and 3 periods, which consisted of 5 d adaption, 2 d fecal collection, and 2 d ileal digesta collection. The results indicated that AID of P was not different from ATTD of P in all diets (P = 0.45). The digestibility of P was affected by source of P (P &lt; 0.01), with mean of 33.7% in SBM and 50.3% in DDGS. The AID of P in SBM increased linearly (P &lt; 0.05) with increasing P concentrations; however, there was no effect of increasing P concentrations on AID and ATTD of P in DDGS. Determined by regression analysis, true ileal digestibility of P was 58.3% or 57.6%, and true total tract digestibility of P was 56.0% or 62.6%, for SBM or DDGS respectively. The estimated ileal endogenous P loss was 0.61 or 0.13 g//kg DMI, and total tract endogenous P loss was 0.53 or 0.35 g/kg DMI, for SBM or DDGS respectively. In summary, source and concentration of dietary P affect the digestibility of P in growing pigs but there was no difference between AID and ATTD of P.

255 Determining the optimal dose of microbial enzyme to enhance fiber digestion

Certain enzymes may enhance fiber digestion, but the optimum dosage for ruminants consuming bermudagrass hay is not known. The objective of this study was to determine the optimal dosage of a combination of a protease with Aspergillus oryzae and A. niger fermentation extract blend on fiber digestion and rumen fermentation of bermudagrass hay by sheep. Twenty ewes (30.3 ± 5.29 kg BW) were allocated randomly to 1 of 5 diets (n = 4/treatment). Bermudagrass hay was chopped and offered for ad libitum consumption to ewes housed individually in 1 × 1.5-m pens with plastic-coated grate flooring. Diets were supplemented with 0.25% BW of soybean meal and either no enzyme or 1.5, 3, 4.5, or 6 g of a mixture of a protease with A. oryzae and A. niger fermentation extracts in a calcium carbonate carrier. A 14-d dietary adaptation was followed by 7 d of total fecal collection. On d 21, 3 rumen samples per ewe were taken at 4 h intervals for analysis of pH and VFA concentrations. Data were analyzed using the MIXED procedure of SAS and orthogonal linear and quadratic contrasts were used to assess enzyme dosage effects. Dry matter and ADF digestibility increased quadratically (P &lt; 0.05), and NDF and OM digestibility tended (P ≤ 0.07) to increase quadratically across dosages. Ruminal acetate concentrations decreased quadratically and ruminal propionate increased quadratically (P &lt; 0.05) with increasing enzyme dosage (P &lt; 0.05). Total VFA concentrations were not affected by dosage (P = 0.71), but the acetate:propionate ratio decreased quadratically (P &lt; 0.05) with increasing enzyme dosage. In conclusion, a protease and A. oryzae and A. niger fermentation extract blend increased fiber digestion, but dosages over 3 g of enzyme did not further enhance DMD or DMI.