Effects of calcium feeding strategy on true ileal phosphorus digestibility and true phosphorus retention determined with growing broilers.

An experiment utilizing 960 Ross × Ross 708 male broilers was conducted to determine the effects of Ca feeding strategy on true ileal (prececal) P digestibility (TIPD) and true P retention (TPR) of corn. Experimental diets were formulated with 1 of 3 dietary Ca feeding strategies (0.95%, 0.13%, or variable Ca concentrations to maintain a 2.1:1 Ca:P ratio) and contain 0, 25, 50, or 75% corn. A practical corn-soybean meal diet (1.4:1 Ca:P ratio) was fed as a control. After receiving a common starter diet, experimental diets were fed from 19 to 26 d of age. After a 48-h dietary adaptation period, a 48-h retention assay was conducted. At 25 and 26 d of age, ileal digesta were collected from 8 birds per cage. Broilers consuming the control diet had higher (P<0.001) BW gain, feed intake, digesta P, and excreta P than broilers consuming the corn titration diets. Digesta and excreta P increased (linear, P<0.05) with graded increases of corn. True ileal P digestibility and TPR were highest (P<0.05) for diets with 0.13% Ca (57.3 and 69.5%, respectively) compared with diets formulated with a 2.1:1 Ca:P ratio (41.2 and 37.8%, respectively) or 0.95% Ca (25.4 and 39.0%, respectively). Values for TPR were higher (P<0.05) than those for TIPD except when the dietary Ca:P ratio was fixed. Additionally, negative endogenous P losses were predicted by regression equations when TPR was estimated for birds fed titration diets with the fixed Ca:P ratio. Changing the Ca concentration of the diets to maintain a fixed Ca:P ratio influenced (P<0.001) apparent P retention, which affected the estimate for TPR due to the prediction of negative endogenous P losses. These data demonstrated that regression analysis may have limitations when estimating the TIPD or TPR of corn when formulating diets with different Ca feeding strategies. More research is necessary to elucidate the factors that contributed to regression equations predicting negative endogenous P losses.

Effects of exogenous xylanase on performance, nutrient digestibility, volatile fatty acid production and digestive tract thermal profiles of broilers fed on wheat- or maize-based diet.

1. A previous experiment reported that caecal temperature was negatively correlated with d 49 feed conversion ratio (FCR). This increased temperature in the caeca may indicate a prebiotic effect. An experiment was designed to investigate whether caecal temperature was affected in diets based on maize and whether other portions of the tract were affected. 2. A total of 25 Ross 308-d-old male broilers were allocated to each of 8 replicate pens per treatment. Treatments followed a 2 × 3 factorial design: two diets based on wheat or maize and three levels of enzyme addition, 0, 16 000 or 32 000 BXU/kg. Growth performance was assessed between d 1 and 49. Digestibility measurements were taken at d 28 and 49. On d 49, the excised small and large intestine of each bird was thermally imaged, weighed and volatile fatty acids (VFA) measured. 3. On d 28 and d 49, birds on the maize diets had higher feed intake and weight gain than those offered wheat diets. Additionally, on d 28, birds that received the maize diet had lower FCR than those offered the wheat diet. Enzyme improved FCR at d 49, independently of cereal. On d 28, enzyme improved the coefficient of apparent ileal DM digestibility and the coefficient of apparent ileal nitrogen digestibility. Enzyme only improved apparent ileal digestible energy in wheat-based diets (interactive term). On d 49, all digestibility parameters were improved by enzyme. Enzyme increased gizzard weight in maize-fed birds and the caeca of those fed wheat were heavier. The higher enzyme dose decreased duodenal temperature. In summary of VFA data, wheat-based diets produced more total VFAs and the total amount also increased with enzyme. 4. It appears from this study that there is equal potential in both wheat and maize diets for xylanase to improve performance of broilers probably through different mechanisms.

Multicarbohydrase Enzymes for Non-ruminants.

The first purpose of this review is to outline some of the background information necessary to understand the mechanisms of action of fibre-degrading enzymes in non-ruminants. Secondly, the well-known and understood mechanisms are described, i) eliminating the nutrient encapsulating effect of the cell wall and ii) ameliorating viscosity problems associated with certain Non Starch Polysaccharides, particularly arabinoxylans and ß-glucans. A third, indirect mechanism is then discussed: the activity of such enzymes in producing prebiotic oligosaccharides and promoting beneficial cecal fermentation. The literature contains a wealth of information on various non starch polysaccharide degrading enzyme (NSPase) preparations and this review aims to conclude by discussing this body of work, with reference to the above mechanisms. It is suggested that the way in which multi- versus single-component products are compared is often flawed and that some continuity should be employed in methods and terminology.

Effects of exogenous xylanase on performance, nutrient digestibility and caecal thermal profiles of broilers given wheat-based diets.

1. Five dietary treatments were used in a 49 d broiler trial to assess the effect of xylanase on performance, nutrient digestibility and thermal profiles of the caeca and head. Treatments included an industry-standard control diet and four further diets where xylanase was introduced with or without a metabolisable energy density dilution either from day one or the introduction was delayed until d 28. 2. The addition of xylanase with no associated energy dilution from day one resulted in the most consistent beneficial effects on performance, with significant improvements in weight gain compared with the industry-standard to d 28 and at d 49. Addition of xylanase from d 28 (with no energy dilution) was the second most successful strategy and resulted in a significant improvement in feed conversion ratio (FCR) from d 29 to 49 and overall. 3. Addition of xylanase improved ileal digestible energy values at d 28 by around 0.35 MJ/kg and ileal nitrogen digestibility coefficients by around 3%. On d 49 xylanase improved ileal digestible energy values by around 0.9 MJ/kg and ileal nitrogen digestibility coefficients by around 4.6%. 4. Thermal imaging of the head and caeca of three birds per replicate on d 49 revealed a significant increase in caecal surface temperature following xylanase addition with no effect on head temperature profile. These increases were particularly large (around 1.4ºC, or 3.9%) when xylanase was added from day one with no corresponding energy dilution in feed formulation. 5. It can be concluded that supplemental xylanase is effective in improving performance and nutrient digestibility in broilers given wheat-based diets. The correlation between the magnitude of this effect and the increased temperature in the caeca presents additional evidence that the hind-gut microflora may play an important, if yet unquantified, role in the outworking of these mechanisms.

Effect of xylanase on performance and apparent metabolisable energy in starter broilers fed diets containing one maize variety harvested in different regions of china.

The objective of this study was to investigate the variability in broiler performance, apparent metabolisable energy (AME) and ileal digestible energy (IDE) between five different maize samples fed with and without xylanase at 16,000 U/kg. Various in vitro characterisations were conducted to determine if any could predict performance or AME. Samples of the maize were harvested in five diverse regions and fed individually in a mash diet as follows (g/kg): test maize 608.3; soya bean meal (SBM) 324.1; poultry fat 25.2; salt 4.6; met 2.6; lys 1.6; thr 0.5; limestone 9.7, dical 18.4; vit/min 5.0; CP 210 and ME (kcal/kg) 3,085. The diets were fed to 720 broilers with 6 replicates, each containing 12 birds per treatment, from 0 to 18 d of age. Maize samples were analysed for starch, protein, crude fibre, fat, protein solubility index (PSI) and vitreousness using near infra red reflectance spectroscopy (NIR). They were also assayed using an in vitro starch digestibility method. The results showed that there was no effect of harvest region on the feed intake (FI), body weight gain (BWG) or feed conversion ratio (FCR) of the broilers over the 18 d period (p = 0.959, 0.926, 0.819 respectively). There was an improvement in all parameters with the addition of xylanase (FI p = 0.011; BWG and FCR p<0.001). There was a significant positive effect of xylanase on IDE, AME, IDE Intake (IDEI) and AME intake (AMEI) (p<0.0001 in all cases). Although there was no significant effect of maize source, there was a strong trend towards variability in IDE (p = 0.066) and AME (p = 0.058). There were no significant correlations (p<0.05) between any proximate or physiochemical values and any performance or AME values. This may suggest that none of those selected were suitable predictors for performance or AME. The broilers performed well according to the breed guidelines, with slightly increased FI, increased BWG and similar FCR prior to the addition of xylanase. When FCR and BWG were analysed with FI as a covariate, xylanase addition remained significant suggesting that the improvement in BWG and FCR was driven by an increase in digestibility and nutrient availability.

The association between faecal host DNA or faecal calprotectin and feed efficiency in pigs fed yeast-enriched protein concentrate.

Gut cell losses contribute to overall feed efficiency due to the energy requirement for cell replenishment. Intestinal epithelial cells are sloughed into the intestinal lumen as digesta passes through the gastrointestinal tract, where cells are degraded by endonucleases. This leads to fragmented DNA being present in faeces, which may be an indicator of gut cell loss. Therefore, measuring host faecal DNA content could have potential as a non-invasive marker of gut cell loss and result in a novel technique for the assessment of how different feed ingredients impact upon gut health. Faecal calprotectin (CALP) is a marker of intestinal inflammation. This was a pilot study designed to test a methodology for extracting and quantifying DNA from pig faeces, and to assess whether any differences in host faecal DNA and CALP could be detected. An additional aim was to determine whether any differences in the above measures were related to the pig performance response to dietary yeast-enriched protein concentrate (YPC). Newly weaned (∼26.5 days of age) Large White × Landrace × Pietrain piglets (8.37 kg ±1.10, n = 180) were assigned to one of four treatment groups (nine replicates of five pigs), differing in dietary YPC content: 0% (control), 2.5%, 5% and 7.5% (w/w). Pooled faecal samples were collected on days 14 and 28 of the 36-day trial. Deoxyribonucleic acid was extracted and quantitative PCR was used to assess DNA composition. Pig genomic DNA was detected using primers specific for the pig cytochrome b (CYTB) gene, and bacterial DNA was detected using universal 16S primers. A pig CALP ELISA was used to assess gut inflammation. Dietary YPC significantly reduced feed conversion ratio (FCR) from weaning to day 14 (P<0.001), but not from day 14 to day 28 (P = 0.220). Pig faecal CYTB DNA content was significantly (P = 0.008) reduced in YPC-treated pigs, with no effect of time, whereas total faecal bacterial DNA content was unaffected by diet or time (P>0.05). Faecal CALP levels were significantly higher at day 14 compared with day 28, but there was no effect of YPC inclusion and no relationship with FCR. In conclusion, YPC reduced faecal CYTB DNA content and this correlated positively with FCR, but was unrelated to gut inflammation, suggesting that it could be a non-invasive marker of gut cell loss. However, further validation experiments by an independent method are required to verify the origin of pig faecal CYTB DNA as being from sloughed intestinal epithelial cells.

Amino acid digestibility of larval meal (Musca domestica) for broiler chickens.

Work was undertaken to investigate the potential use of housefly (Musca domestica) larvae reared on broiler manure as a source of nutrition for poultry production in the United Kingdom. Nutritional analysis showed that larvae have a high (>45% dry wt.) protein content and a favorable amino acid profile that is rich in key amino acids, such as lysine and methionine. A broiler digestibility trial was carried out to determine the apparent ileal digestibility coefficients (AIDC) and true ileal digestibility coefficients (TIDC) of amino acids (AA) from insect larval meal (ILM) from M. domestica and fishmeal (FM) in broiler chickens. This was calculated using multiple linear regression technique based upon 3 inclusions of each protein source in a semisynthetic diet. One-hundred-forty-four day-old male (Ross 308) broilers were fed from hatch on a commercial starter diet for 20 days. Experimental diets were fed from d 21 to 28, and feed intakes were measured daily. On d 28, the trial was terminated, ileal digesta were collected for the determination of AIDC and TIDC of AA, and inflammatory responses (gizzard erosion and eye discharge) were measured. No significant differences were observed in digestibilities between protein sources for any AA. Furthermore, ILM feeding did not induce gizzard erosion or eye discharge at any inclusion. These results provide strong evidence to suggest that ILM of the common housefly can provide a successful alternative protein source to FM in broiler diets.

Methodology affects measures of phosphorus availability in growing broilers: Effects of calcium feeding strategy and dietary adaptation period length on true ileal phosphorus digestibility and predicted endogenous phosphorus losses1.

An experiment was conducted to determine the effects of Ca feeding strategy and dietary adaptation period length (DAPL) on the apparent ileal P digestibility (AIPD) and apparent ileal myo-inositol 1,2,3,4,5,6 hexakis dihydrogen phosphate (IP6) hydrolysis (AIIP6H) of corn titration diets. Nine hundred sixty Ross × Ross 708 male broiler chicks were placed into 80 battery cages. Broilers received a common starter diet until 18 d of age and then were fed one of 10 experimental treatments from 19 to 21 d of age. Nine diets were formulated to evaluate 5 corn inclusion concentrations (15, 30, 45, 60, or 75%) and 2 Ca feeding strategies (fixed at 0.35% or 1.4:1 Ca:P) after 3 DAPL (zero, 24, and 48 h). As a control for DAPL, one treatment group received the common starter diet for the duration of the experiment. Broilers consuming the control diet had higher (P < 0.001) BW gain and feed intake than broilers fed the corn titration diets. Apparent ileal P digestibility of the control diet was affected (P = 0.038) by DAPL. For diets formulated with a 1.4:1 Ca:P ratio, negative linear effects (P < 0.05) on AIPD and AIIP6H were observed with increasing corn. Conversely, for diets formulated with 0.35% Ca, positive linear effects (P < 0.05) were measured for AIPD after a 48 DAPL while no linear or quadratic effects (P > 0.05) were measured for AIPD or AIIP6H for other DAPL. Broilers fed diets formulated with 1.4:1 Ca:P had variable (P < 0.05) true ileal P digestibility (TIPD; 32.2, 15.1, and 35.4%) and negative endogenous P losses (EPL; -190, -499, and -262 mg/kg DM intake) for zero, 24, and 48 h DAPL, respectively. Conversely, TIPD values (41.2, 39.1, and 47.3%) were similar (P > 0.05) and EPL were positive (102, 197, and 154 mg/kg DM intake), regardless of DAPL, for broilers fed diets formulated with 0.35% Ca. These data demonstrated that formulating diets with a 1.4:1 Ca:P ratio affected AIPD of the titration diets, shifting the regression line and predicted negative EPL and an underestimation of TIPD.

Methodology affects measures of phosphorus availability in growing broilers. 2. Effects of calcium feeding strategy and dietary adaptation period length on phytate hydrolysis at different locations in the gastrointestinal tract1.

An experiment was conducted to determine the effects of dietary adaptation period length (DAPL; 0, 24, and 48 h) and Ca feeding strategy (0.35% or 1.4:1 Ca:P ratio) on apparent phytate P (myo-inositol 1,2,3,4,5,6 hexakis dihydrogen phosphate; IP6) hydrolysis (AIP6H) and apparent digestibility (AΣIPD) of the sum of all inositol phosphate esters (ΣIP) of corn-titration diets at 3 locations (proventriculus/gizzard [Pro/Giz], jejunum, and distal ileum) in the gastrointestinal tract (GIT). Four hundred thirty-two Ross × Ross 708 male broilers were placed into 36 battery cages and fed a common starter diet until 18 d of age. Eight semipurified diets and a control diet for DAPL were fed from 19 to 21 d of age. Digesta were collected at each location from 4 birds per pen after each DAPL. Diets formulated with a 1.4:1 Ca:P ratio had higher (P < 0.001) AIP6H and AΣIPD when measured in the jejunum and ileum, but no differences were observed in the Pro/Giz. No interaction effects between DAPL and sampling location were observed for AIP6H and AΣIPD of the control diet. Conversely, interactive effects (P < 0.05) were measured for AIP6H and AΣIPD of the corn-titration diets. The highest values for both AIP6H (73.9%) and AΣIPD (80.7%) were measured in the Pro/Giz after 24 h. Phytate hydrolysis and AΣIPD were similar regardless of DAPL when sampled from the distal ileum. Concentrations of TiO2, IP6 and ΣIP also varied (P < 0.05) in response to DAPL and sampling location. Variability was likely due to inconsistencies in the flow of inositol phosphate esters and TiO2 through the GIT, specifically the Pro/Giz. Therefore, the use of TiO2 as an inert marker may have limitations when determining the hydrolysis and digestibility of phytate esters.

Interactive effects of dietary adaptation period length and titration diet type on apparent ileal phosphorus digestibility and phosphorus retention in growing broilers.

Two experiments were conducted to examine the effects of different corn titration diets and dietary adaptation period length (DAPL) on intestinal histology, apparent ileal P digestibility (AIPD), and apparent P retention (APR) in Ross × Ross 708 male broilers from 20 to 24 d of age. It was hypothesized that purified ingredients in nutrient-deficient titration diets may affect P availability with varying DAPL. In experiment 1, 1,152 broilers were utilized in a 3 × 3 factorial treatment structure with 3 diets (control, 25% corn titration diet [25CTD], or 75% corn titration diet [75CTD]) and 3 DAPL (0, 24, or 72 h). Experiment 2 was conducted with 576 broilers as a 4 × 3 factorial arrangement with 4 diets (control, 25CTD, 75CTD, or nitrogen-free diet [NFD]) and 3 DAPL (24, 48, or 72 h). All diets contained purified ingredients except for the control diet, which had the same formulation as the common starter and served as a control for DAPL. The NFD diet was fed as a highly purified protein-free diet. Broilers were fed a common diet until 19 d of age and then transferred to experimental diets at 20 d of age. In experiment 1, diet type did not affect (P > 0.05) intestinal histology. However, diet type and DAPL each influenced (P.≤.0.001) diet AIPD. Higher (P.≤.0.001) AIPD was measured for the control diet compared with the 75CDT, and the 25CTD had the lowest AIPD. Following a 24 h DAPL, AIPD was higher (P.≤.0.001) than after a DAPL of 0 or 72 h. In experiment 2, diet type × DAPL interactions (P.≤.0.001) were observed for APR of the control diet, 75CTD, and NFD, but not the 25CTD. Because APR of the control diet was affected by varying DAPL, factors other than differences in diet type may have been responsible for inconsistencies in the measure of P availability. Furthermore, no clear evidence was observed that broilers were able to adapt to P-deficient diets by increasing APR or AIPD. In conclusion, a standard DAPL should be established as a means to reduce variability associated with measuring of feedstuff P availability.

A comparison of the occurrence of common dental abnormalities in stabled and free-grazing horses.

The purpose of this study was to gain evidence on the prevalence of dental abnormalities in stable-kept horses in comparison with free-living horses. It is expected that free-living horses that graze for as much as 16 h/day will have fewer dental abnormalities than stable-kept horses. In this study, the latter group was fed a diet that was based on a relatively high-energy, cereal-based feed. This was thought to be a representative of common practice in domesticated, stable-kept horses. Compound diets such as this have previously been shown to increase the frequency of chewing cycles and decrease mediolateral excursion. The occurrence of 10 named dental abnormalities present in the dentition of 60 Thoroughbred-type horses was recorded. Half of the population was at grass all year round in New South Wales, Australia. The remainder were stabled for 24 h/day in Gloucestershire, UK. All horses were between 5 and 15 years of age. The same, experienced, equine dental technician examined all horses using a full-mouth speculum and produced a routine dental chart. Stable-kept horses had a significantly higher total occurrence of abnormalities (P < 0.001) than free-living horses. The stable-kept group had a significantly higher prevalence of exaggerated transverse ridging across the occlusal surface of the cheek teeth, focal or ramped overgrowths of the cheek teeth and periodontal disease (P < 0.01 in all cases). All horses in both groups had some occurrence of sharp edges of the buccal and lingual edges of the cheek teeth. The results are in agreement with anecdotal evidence that a fibre-based, grazed diet results in fewer dental abnormalities. However, sharp edges may occur even with what is perceived as a 'natural' diet.