Apparent digestibility of wheat bran and extruded flax in horses determined from the total collection of feces and acid-insoluble ash as an internal marker

Several studies have reported data on comparisons between two methods: the total collection of feces and the internal markers method. The aim of this study was to assess the apparent digestibility of two concentrates and to compare the apparent digestion coefficients using the total collection of feces and acid-insoluble ash (AIA) as the internal marker method. In 2009, six adult geldings aged between 3 and 11 years, with an average weight per trial of 543, 540 and 542 kg, respectively, were used to determine the apparent digestibility by means of three in vivo digestibility trials on hay, hay plus wheat bran (60 : 40) and hay plus extruded flax (80 : 20). Feces were collected over a 6-day period with a previous 14-day adaptation period. The three digestibility trials were carried out to determine the digestion coefficients of the three diets and, indirectly, of the two concentrates. The digestion coefficients of the diets were determined for the dry matter, organic matter, crude protein and gross energy, whereas the apparent digestion coefficients of the same parameters were calculated for wheat bran and extruded flax, by calculating the difference from the previous results. The data were analyzed using the Student t-test for paired samples. The digestion coefficients obtained were similar when the total collection of feces and the AIA method were used. Higher data variability, confirmed by a greater standard deviation, was observed using the AIA method to estimate the apparent digestion coefficients. It can be concluded that the use of AIA as an internal marker in digestibility trials on average leads to values similar to those obtained with the total collection of feces and can therefore be considered a less-expensive method to determine apparent digestion coefficients. Nevertheless, the total collection of feces should still be considered the best choice to determine the digestibility of some specific feedstuffs.     

Digestibility contributes to between-animal variation in feed efficiency in beef cows

Residual feed intake (RFI) is an alternative measure of feed efficiency (FE) and is calculated as the difference between actual and expected feed intake. The biological mechanisms underlying animal-to-animal variation in FE are not well understood. The aim of this study was to investigate the digestive ability of beef cows selected for RFI divergence as heifers, using two contrasted diets. Fifteen 4-year-old beef cows were selected from a total of 69 heifers based on their RFI following the feedlot test. The selected heifers were ranked into high-RFI (+ 1.02 ± 0.28, n = 8) and low-RFI (−0.73 ± 0.28, n = 7), and a digestibility trial was performed after their first lactation. Both RFI groups were offered two different diets: 100% hay or a fattening diet which consisted of a DM basis of 67% whole-plant maize silage and 33% high starch concentrates over four experimental periods (two per diet). A diet effect was observed on feed intake and apparent digestibility, whereas no diet × RFI interaction was detected (P > 0.05). Intake and apparent digestibility were higher in cows fed the fattening diet than in those fed the hay diet (P < 0.0001). DM intake (DMI) and organic matter apparent digestibility (OMd) were repeatable and positively correlated between the two subsequent periods of measurements. For the hay and fattening diets, the repeatability between periods was r = 0.71 and r = 0.73 for DMI and r = 0.87 and r = 0.48 for OMd, respectively. Moreover, both intake (r = 0.55) and OMd (r = 0.54) were positively correlated (P < 0.05) between the hay and fattening diets. Significant differences between beef cows selected for divergence in RFI as heifers were observed for digestive traits (P < 0.05), DM and organic matter (OM) apparent digestibility being higher for low-RFI cows. Overall, this study showed that apparent digestibility contributes to between-animal variation in FE in beef cows.     

Apparent digestibility of broken rice in horses using in vivo and in vitro methods

The aim of this study was to assess the apparent digestibility of broken rice using total collection of feces and the pepsin-cellulase in vitro technique to provide updated and more accurate digestion coefficients for this by-product when fed to horses. The in vivo digestibility trial was consecutively performed, using five adult geldings, weighing 555.6 kg on average. First, hay was given as the only feedstuff, while second, the experimental diet consisted of the same hay plus broken rice at a forage-to-concentrate ratio of 70/30 (on dry matter (DM) basis). Feces were collected over 6 days preceded by a 14-day adaptation period. The digestibility trial was carried out to determine the digestion coefficients for DM, organic matter (OM), CP and gross energy in both diets, while apparent digestion coefficients for the same parameters were calculated for broken rice alone, using the difference between the two sets of results. At the same time, an in vitro trial was carried out using pepsin-cellulase technique on the samples of hay and broken rice tested during the in vivo trial. As expected, supplementation with broken rice increased digestibility according to all the parameters used. The high OM digestion coefficients of broken rice were confirmed both by the calculated in vivo method and by the predicted results of pepsin-cellulase technique (92.6% and 87.1%, respectively), underlining the high digestibility of this by-product when fed to horses.     

Digestibility by cattle of diets containing dried pig faeces

The apparent digestibility of diets in which dried pig faeces replaced 0, 15, 30 and 45% of hay (diets A, B, C and D, respectively) was compared using four steers in an experiment of 4 × 4 Latin square design.All rations were readily consumed and no undesirable effect on animal health was observed. Each increase in the proportion of pig faeces in the diet reduced the apparent digestibility of the dietary components. The dry matter digestibility of diets A, B, C and D was 57.9, 52.4, 50.0 and 44.5%, respectively. Similar reductions occurred in the apparent digestibility of crude protein, crude fibre, ether extract and nitrogen-free extract.     

Evaluation of methodological aspects of digestibility measurements in ponies fed different haylage to concentrate ratios

Methodological aspects of digestibility measurements were studied in four Welsh pony geldings consuming haylage-based diets with increasing proportions of a pelleted concentrate according to a 4×4 Latin square design experiment. Ponies were fed four experimental, iso-energetic (net energy (NE) basis) diets (i.e. 22 MJ NE/day) with increasing proportions of a pelleted concentrate (C) in relation to haylage (H). The absolute amounts of diet dry matter fed per day were 4.48 kg of H (100H), 3.36 and 0.73 kg of H and C (75H25C), 2.24 and 1.45 kg of H and C (50H50C) and 1.12 and 2.17 kg of H and C (25H75C). Diets were supplemented with minerals, vitamins and TiO₂ (3.7 g Ti/day). Voluntary voided faeces were quantitatively collected daily during 10 consecutive days and analysed for moisture, ash, ADL, acid-insoluble ash (AIA) and Ti. A minimum faeces collection period of 6 consecutive days, along with a 14-day period to adapt the animals to the diets and become accustomed to the collection procedure, is recommended to obtain accurate estimations on dry matter digestibility and organic matter digestibility (OMD) in equids fed haylage-based diets supplemented with concentrate. In addition, the recovery of AIA, ADL and Ti was determined and evaluated. Mean faecal recovery over 10 consecutive days across diets for AIA, ADL and Ti was 124.9% (SEM 2.9), 108.7% (SEM 2.0) and 97.5% (SEM 0.9), respectively. Cumulative faecal recovery of AIA significantly differed between treatments, indicating that AIA is inadequate to estimate the OMD in equines. In addition, evaluation of the CV of mean cumulative faecal recoveries obtained by AIA, ADL and Ti showed greater variations in faecal excretion of AIA (9.1) and ADL (7.4) than Ti (3.7). The accuracy of prediction of OMD was higher with the use of Ti than ADL. The use of Ti is preferred as a marker in digestibility trials in equines fed haylage-based diets supplemented with increasing amounts of pelleted concentrate.     

The effect of dietary carbohydrate composition on apparent total tract digestibility,feed mean retention time,nitrogen and water balance in horses

A total of four diets with different carbohydrate composition were investigated in a 4×4 Latin square design experiment with four Norwegian Coldblooded trotter horses. The objective of the present study was to increase the fermentable fibre content and reduce the starch intake of the total ration obtained by partly substituting mature hay and barley with sugar beet pulp (SBP), a soluble fibre source. The diets investigated were hay only (HAY), hay (85% of dry matter intake (DMI)) and molassed SBP (15% of DMI) (SBP), hay (68% of DMI) and barley (32% of DMI) (BAR), and hay (68% of DMI), barley (26% of DMI) and SBP (6% of DMI) (BAR+SBP). The feeding level was 18.5, 17.3, 15.7 and 15.7 g DM/kg BW per day for the HAY, SBP, BAR and BAR+SBP diets, respectively. Each diet was fed for 18 days followed by 10 days of data collection, where apparent total tract digestibility (ATTD), total mean retention time (TMRT) of ytterbium-labelled hay, water balance, digestible energy (DE) intake and nitrogen balance were measured. An enzymatic chemical dietary fibre (DF) method was used to get detailed information on the composition and ATTD of the fibre fraction. Inclusion of SBP in the diet increased the ATTD of the constituent sugars galactose and arabinose (P<0.01). Feeding the HAY and SBP diets resulted in a lower TMRT owing to a higher DF intake than the BAR and BAR+SBP diets (P<0.01). There was no difference in water intake between HAY and SBP, but faecal dry matter was lower for HAY than the other diets (P=0.017), indicating that water was more tightly bound to fibre in the HAY diet. The diets were iso-energetic and provided enough DE and protein for light to moderate exercise for a 550 kg horse. In conclusion, this study showed that the DF intake had a larger effect on TMRT than partly substituting hay or barley with SBP, and that highly fermentable pectin-rich soluble DF from SBP maintains high nutrient utilization in horses.     

A comparison of total collection and marker technique for the measurement of apparent digestibility of diets for growing pigs

Use of markers for the measurement of digestibility is a less labour intensive method than total faecal collection. The objectives of the present study were: (1) to evaluate chromic oxide (Cr₂O₃), titanium dioxide (TiO₂) and acid-insoluble ash (AIA) markers for the calculation of digestibility and (2) to examine the reliability of grab sampling as a technique for measuring digestibility in group-housed animals. For marker comparison, eight entire males were housed in individual metabolism crates and offered a cereal-based diet. Pigs were randomly allotted to treatments for total collection period one, four to the diet with 1 g chromic oxide and 1 g titanium dioxide added per kilogram (Treatment A) and four to the same the diet without marker (Treatment B). During total collection period two, the treatments were reversed. AIA was measured for all animals in crates. For grab sampling study, grouped-housed animals (13–14 per pen) were fed the same cereal-based diet as for marker comparison above and AIA marker was used. Faecal samples were taken from a representative number of animals (minimum eight) in a pen while held in a weighing scales. All feed and faeces samples were analysed for marker content and digestibility. Feed analysis showed 0.93 g/kg of Cr₂O₃ and 1.02 g/kg of TiO₂ added to the diet. Faecal marker recovery was 96, 92.3 and 99.9% (S.E. 2.27) for Cr₂O₃, TiO₂ and AIA, respectively. Mean energy digestibility values were 0.858, 0.848, 0.844 and 0.855 (S.E. 0.003, P<0.01) for total collection, Cr₂O₃, TiO₂, AIA, respectively. Energy digestibility coefficients were 0.852 and 0.861 (S.E. 0.004, P>0.10) for total collection (as measured in marker comparison) and grab sampled animals, respectively. In conclusion, acid-insoluble is a reliable marker for the measurement of digestibility and grab sampling offers a rapid and reliable alternative to the labour intensive metabolism crate method.     

Acid‐insoluble ash as a measure of dry matter digestibility in captive African elephants (Loxodonta africana)

There are limited data on the diet dry matter digestibility (DMD) of captive African elephants. Although the total fecal collection method is the standard for determining DMD, it is labor‐intensive, time‐consuming, and expensive. The acid‐insoluble ash (AIA) marker technique has been used successfully to determine DMD in ruminants and monogastrics. The objective of this study was to assess how accurately the AIA marker technique could estimate the DMD of captive African elephants (Loxodonta africana). Three mature male African elephants at Disney's Animal Kingdom in Florida were used in this study. The animals were offered a Bermuda grass hay‐based ration, and the total dry matter intake (DMI) and total fecal output were measured daily over a 7‐day period to determine the total collection DMD. The feed ingredients and fecal samples were also analyzed for AIA. Although there were differences (P<0.05) in total DMI and total fecal outputs, the DMD values did not (P>0.05) differ (35.1±0.72 vs. 37.1±0.72 for total collection and AIA, respectively). There was a linear (y=0.9461x; R²=0.74) relationship between the total collection and AIA marker technique DMD values. These results suggest that AIA can be used to accurately estimate the DMD of captive African elephants. Zoo Biol 0:1–5, 2005. © 2005 Wiley‐Liss, Inc.     

The effects of barley, unmolassed sugar-beet pulp and molasses supplements on organic matter, nitrogen and fibre digestion in the rumen of cattle given a silage diet

In a 4 × 4 Latin-square experiment with a 2 × 2 factorial arrangement of treatments, 4 cattle fitted with a rumen and duodenal cannula were given four grass-containing diets [480 g kg⁻¹ of the total dry matter (DM) intake] and barley (BU), barley + molasses (2:1) (BM), sugar-beet pulp (SU) or sugar-beet pulp + molasses (SM). Duodenal flow was estimated using Cr-mordanted straw and CoEDTA as markers, and microbial nitrogen entering the small intestine using purine bases of nucleic acids.

Molasses-containing diets had a higher (P < 0.01) organic matter (OM) digestibility. The proportion of digestible OM apparently disappearing in the rumen averaged 0.72 and was not significantly affected by the diet. When cattle received molasses, the quantity of microbial N entering the small intestine was higher (P < 0.05) and there was a trend towards a higher efficiency of microbial N synthesis (28.8 vs. 25.6 g N kg⁻¹ OM apparently digested in the rumen). When S diets were consumed, total non-ammonia N flow at the duodenum exceeded N intake by 7.0 g day⁻¹ and when B diets were consumed, it was 0.7 g day⁻¹ less than N intake. Feed N degradability in the rumen and apparent N digestibility of S diets were lower (P < 0.05; P < 0.001) than those of B diets.

Rumen (P < 0.05) and total (P < 0.001) digestibility of neutral detergent fibre (NDF) and acid detergent fibre (ADF) was higher when S diets were given. The proportion of digestible fibre disappearing in the rumen was not affected by the diet. The rate and extent of silage and hay DM degradation were not significantly affected by the diet. However, dietary inclusion of molasses decreased (P < 0.05) the lag time of both hay and silage DM degradation.

The rumen dilution rate of liquid averaged 0.097 and that of particles, 0.049; neither was significantly different for either B and S diets or U and M diets. Duodenal liquid flow was higher (P < 0.05) for M diets.

Average rumen pH was not affected by the diet, but the molasses diets increased (P < 0.05) the range in rumen pH. The BM diet was associated with higher (P < 0.01) rumen ammonia concentration than the other diets. Low rumen ammonia concentrations (< 2 mM) were observed for long periods between feeds. The molar proportion of butyrate was higher on B diets and there was a trend towards a higher proportion of acetate and propionate on S diets. Molasses tended to increase the molar proportion of propionate and butyrate.     

Nutritional methods to decrease N losses from open-dirt feedlots in Nebraska

Nitrogen (N) losses from cattle feedlots are of concern due to loss of valuable N and enrichment of the atmospheric N pool. Nutritional methods to decrease such losses would have economic and environmental benefits. One method to decrease N losses is by increasing carbon (C) on the pen surface. The most cost effective method of decreasing N losses with C may be feeding diets lower in digestibility compared to adding C directly to pens. Therefore, three experiments evaluated feeding corn bran (which is less digestible than corn) as either 0, 15, or 30% of the diet. The 15- and 30%-bran diets increase organic matter (OM) excretion by approximately 0.5 and 1.0 kg per steer per day, respectively. Compared with no bran, feeding 15 and 30% decreased feed efficiency by 7.8 and 10.4%, respectively. Nutrient balance was assessed in two trials from October through May and in one trial from June to September. During the trials from October to May, N losses were decreased by 14.5 and 20.7% for the 15- and 30%-bran diets compared with no bran. Feeding 15 or 30% bran did not influence N losses in the experiment from June to September. Increasing the C:N ratio of manure prior to cleaning open-dirt feedlots had variable results depending on time of year.     

Effect of microbial phytase on apparent ileal amino acid digestibility of phosphorus-adequate diets in growing pigs

Six ileally cannulated pigs (mean initial body weight 34.8 kg) were used to study the effect of microbial phytase on apparent ileal digestibility of P, total N and amino acids. Three P-adequate diets (digestible P concentration 2.3 g kg(- )l) containing barley (B), soyabean meal (S) or a mixture of the two (BS) with or without phytase supplement (1000 FTU x kg(-1)) were fed to pigs using a 6 x 6 Latin square design. The addition of phytase increased (p < 0.05) apparent ileal P digestibility of diets B, S and BS by 16.5, 19.2 and 19.2%, respectively. There was no effect of phytase on the ileal digestibility of total N. Apparent ileal digestibility of amino acids tended to increase in the BS diet supplemented with phytase (mean improvement of 2.2%); but no significant difference was found for any amino acid as compared with the unsupplemented diet. To asses the additivity of apparent amino acid digestibility, the determined values for the BS diet were compared to those calculated from digestibilities found in diets B and S. There were no significant differences between the determined and calculated values. It is concluded that the addition of microbial phytase to P-adequate diets does not affect ileal amino acid digestibility in growing pigs and that the apparent amino acid digestibility values determined in single ingredients may be additive when included into a complex diet.     

Utilization by sheep of dried pig faeces containing a high concentration of copper

Seven groups of three sheep were given pelleted diets as follows: A, 97% hay + 3% molasses; B, C, D, 82% hay + 3% molasses + 15% dried pig faeces; E, F, G, 67% hay + 3% molasses + 30% dried pig faeces. In an attempt to counteract potential toxic effects of copper in the pig faeces (613 mg/kg dry matter), molybdenum was added to diets C and F at the rate of 90 mg/kg diet, and to diets D and G at the rate of 175 mg/kg diet. Sulphate was included in all diets at the rate of 1.08% of diet. Measurements were made of digestibility, copper retention, and plasma glutamic oxaloacetic transaminase (GOT) values during a 70-day feeding period, after which the animals were slaughtered.Dry matter digestibility coefficients were : diet A, 49.2; diets B, C, D, 44.4; diets E, F, G, 42.5, from which the coefficient for pig faeces alone is calculated to be < 30. Mean copper retention over the 70 days ranged from 210 mg for diet A to 1225 mg for diet G (excluding diet E which showed an aberrant retention of 53 ± 185 mg). Plasma GOT values fluctuated between diets and between sheep with a maximum value of 182 units/ml. Mean liver copper concentrations ranged from 718 mg/kg dry matter for diet A to 1740 mg/kg for diet E. Necrotic lesions occurred in some livers. Kidneys were apparently normal. There were no clear differences in copper status of animals receiving 15% versus 30% pig faeces except for a tendency for liver damage to be greater in the latter. There were no apparent effects of additions of molybdenum.The pig faeces were poorly utilized and, because of the high copper content, potentially hazardous to the health of the sheep.     

长吻对鱼粉等六种商品饲料中粗蛋白和能量的消化率

本试验以三氧化二铬（Ｃｒ２Ｏ３）为指示物测定Ⅰ龄长吻对鱼粉、猪血粉、豆饼粉、菜籽饼粉、小麦粉和玉米蛋白粉等六种商品饲料原料粗蛋白和总能量的消化率。试验饲料由参考饲料和试验原料以７０∶３０的比例混合挤压制成颗粒饲料。试验鱼粪便样品用虹吸方式收集,并将测试的消化率结果经过降低１０％的校正。由此所得消化率值更能反应长吻的消化生理状况。另外本文对六种饲料的消化率结果进行了讨论。     

Influence of different dietary calcium levels on the digestibility of Ca,Mg, and P in captive‐born juvenile Galapagos giant tortoises (Geochelone nigra)

Calcium (Ca) and phosphorus (P) are very important minerals in reptile nutrition, but many diets still are not balanced. To achieve optimal growth, including a healthy skeleton and a strong shell, a well‐balanced supply with these minerals is prerequisite. The purpose of this study was to evaluate the digestibility of diets with different calcium levels, with special emphasis on the digestibility of minerals. Fourteen captive‐born juvenile Galapagos giant tortoises of the Zurich and Rotterdam Zoos were used. The animals were housed indoors at a mean temperature of 23°C and 25°C, and at 65% and 60% humidity, respectively. The animals from the same zoo were fed the same diet, which consisted of vegetables, herbs, and a mixture of different Ca sources. Daily mixed fecal samples of all tortoises were collected from day 8 to day 18. A Weender analysis was performed and the HCl‐insoluble ash was used as an indigestible indicator (marker) for the determination of the apparent digestibility. The Ca content of the mixed feedstuffs of diet I was 1.43% on a dry matter basis, and the Ca:P ratio in the food was 3.9:1. In diet II, the Ca content was 2.06% on a dry matter basis, and the Ca:P ratio in the food was 4.8:1. Diet III contained 7.33% of Ca on a dry matter basis, and the Ca:P ratio in the food was 6.7:1. The digestibility of Ca in diet I was 42%. The other examined minerals, Mg and P, had a digestibility of 54% and 84%, respectively. In diet II, the digestibility of Ca was 63%, of Mg 76%, and of P 88%, and in diet III the digestibility of Ca was 82%, of Mg 92%, and of P 91%. The results of this study indicated that higher Ca concentrations in the diet led to an increased apparent digestibility of Ca, Mg, and P. The influence of an increased fat and decreased fiber content in diet III concerning digestibility is discussed. Zoo Biol 20:367–374, 2001. © 2001 Wiley‐Liss, Inc.     

Evaluation of titanium dioxide and chromic oxide as digestibility markers in ponies fed alfalfa hay in relation to marker dosing frequency

In equines, Cr₂O₃ is widely accepted as an indigestible marker, but there are health concerns regarding the carcinogenic properties of Cr₂O₃. Recently, TiO₂ has been suggested to be an alternative digestibility marker in equines. However, a comparison between Cr₂O₃ and TiO₂ has not been made in equines. Six Welsh pony geldings (initial BW: 254±3 kg; 7 years of age) fed chopped alfalfa hay were used to evaluate the use of TiO₂ (Ti) and Cr₂O₃ (Cr) as markers for calculating apparent digestibility and to investigate the effect of frequency of marker administration on the measurement of digestibility values. Diets contained 4.65 kg dry matter (DM) chopped alfalfa hay supplemented with minerals, vitamins, TiO₂ (3.3 g Ti/day) and Cr₂O₃ (3.2 g Cr/day). Ponies were dosed with either 3.3 g Ti and 3.2 g Cr once daily (DF1) or with 1.65 g Ti and 1.60 g Cr twice daily (DF2). After adaptation to the diets and procedures for 14 days, voluntary voided faeces were collected quantitatively over 7 days and analysed for moisture, ash, Ti and Cr. Apparent total tract DM digestibility (DMD) and organic matter digestibility (OMD) were calculated using the total faecal collection (TFC) and marker method (Ti and Cr). The overall mean cumulative faecal recovery of Cr and Ti (as % of intake) were 102.0% and 96.6%, respectively. Mean daily faecal recoveries of Cr as well as of Ti were not different (P=0.323; P=0.808, respectively) between treatments. Overall daily faecal recovery of Cr differed (P=0.019) from 100% when the marker was dosed once daily, whereas overall daily faecal recovery was similar to 100% for both administration frequencies when Ti was used as a marker. For both markers, the coefficient of variation of the mean faecal marker recovery between horses was lower when the markers were administrated twice per day. Across treatments, cumulative DMD and OMD estimated with Ti were similar (P=0.345; P=0.418, respectively) compared with those values determined by TFC method. When Cr was used, the calculated cumulative DMD tended (P=0.097) to be greater compared with those estimated with TFC, and cumulative OMD values were overestimated (P=0.013). Orally supplemented Ti recovery in the faeces of ponies fed chopped alfalfa hay with Ti administered once or twice daily was close to 100%, making it the preferred marker for digestibility trials in equines.     

Effects of Tasco (a seaweed extract) and heat stress on N metabolism and meat fatty acids in wether lambs fed hays containing endophyte-infected fescue

Wether lambs (n = 27, average BW = 40 kg) were used to test response to forage treated with Tasco-Forage (an extract of the brown kelp Ascophyllum nodosum) prior to conserving, or to direct feeding of the extract (Tasco-EX). Hays made from endophyte (Neoyphodium coenophialum)-infested tall fescue (Festuca arundinacea)-based pasture received 0 or 3 kg of Tasco/ha prior to harvest. Lambs, blocked by weight, were randomly allotted to three diets: (1) control hay, (2) treated hay, and (3) #1 + Tasco-EX fed at 1% of the diet. Hays were low in CP (<7%) so all lambs were fed soybean meal (12% of the diet) in addition to trace mineralized salt. Diets were fed at 1.5% BW to prevent refusals. Total collections (7 d) were made during periods without or with applied heat stress. After each period, rumen contents were obtained to determine pH, NH₃ and VFA. Lambs were sacrificed post-trial. A subset was used to evaluate sensory traits and muscle fatty acids. Lambs were in negative N balance during the study and Tasco treatments did not affect N metabolism. Fecal N tended (P < 0.10) to increase with short duration heat stress causing a concomitant decrease (P < 0.05) in apparent N digestibility (58.6 versus 56.1%; S.E. = 0.7). Urinary N loss decreased (P < 0.001) with heat stress (8.0 versus 5.9 g/d; S.E. = 0.2), resulting in increased (P < 0.001) N retention (−2.1 versus −0.3 g/d; S.E. = 0.2). Apparent OM digestibility was not affected by heat stress but was greater (P < 0.05) for lambs fed Tasco-EX treatment than those fed treated hay. Treatment diets decreased (P < 0.05) ruminal butyrate. Heat stress increased (P < 0.05) acetate and total VFA and decreased (P < 0.01) ruminal pH. A tendency (P < 0.11) of increased 14:1ω5, decreased (P < 0.05) 18:0 and total saturated fatty acids in muscle was observed with Tasco diets. Meat sensory characteristics were not affected by treatment. Tasco may alter some aspects of rumen or lipid metabolism but has no effect on N metabolism or meat sensory characteristics of sheep fed restricted, low-quality diets.     

Ileal endogenous losses in pigs feeding a protein-free diet or diets with different contents of casein or crystalline amino acids

The common usage of protein-free diets to estimate unspecific AA losses has been criticised as unphysiological and incorrect. Therefore, in this study different diets were tested for the determination of endogenous losses (EL) of amino acids (AA) and nitrogen (N) assuming a complete absorption in the small intestine. Seven cannulated gilts received a protein-free diet (Diet PF) or diets with 3%, 6% or 10% crude protein (CP) from crystalline AA (Diets CA) or casein (Diets CAS) according to a 7 × 7 Latin square design. After 6 d adaptation to the diet, ileal digesta was collected for 24 h and thereafter analysed for AA, N and the digestibility markers Cr₂O₃ and acid insoluble ash (AIA). Generally, among all AA, the highest amounts of EL were found for Pro, Glu and Gly, and the smallest for Met. Different levels of CP in Diets CA and CAS had no effect on EL. Significant differences between treatments were observed only for the EL of Glu, Ile, Ser (higher in Diets CA and PF), Pro and Tyr (higher in Diet PF) (p < 0.05). There were no differences in determined EL using Cr₂O₃ or AIA as digestibility markers.     

Impact of barley form on equine total tract fibre digestibility and colonic microbiota

This study aimed at assessing the impact of four barley forms on total tract apparent digestibility of dietary fibre in horses fed a large amount of starch in the morning meal (0.27% BW). Processed barley forms had a greater pre-caecal starch digestibility than the whole form. Based on this result, we hypothesised that using barley-processing methods would limit the potential dumping of undegraded starch in the hindgut of horses and, consequently, the potential negative effect on fibre degradation in the hindgut. In a 4×4 latin square design, four mature geldings fitted with a right ventral colon-fistula were fed a meadow hay : concentrate (62 : 38; dry matter (DM) basis) diet at 1.7% BW. The concentrate was made of 80% barley distributed either as whole grain or as processed forms: 2.5 mm ground, pelleted or steam-flaked. For each period, total tract apparent digestibilities of DM, NDF and ADF were determined over 3 consecutive days by total faecal collection, whereas pH, volatile fatty acids (VFA) concentrations and cultural functional bacteria counts (total anaerobic, cellulolytic bacteria, lactic acid producers, amylolytic bacteria and lactic acid utilisers) in colonic content were evaluated on 1 day 4 h after the morning meal. Total tract apparent digestibility of DM and dietary fibre was influenced (P<0.05) by barley form. Diets including thermo-mechanically treated barley forms led to a higher (P<0.05) total tract apparent digestibility of NDF than those constituted of ground barley and also led to a greater (P<0.05) total tract apparent digestibility of ADF than those made of whole or ground barley forms. However, no significant difference was observed in colonic pH, VFA concentrations and cultural bacteria concentrations. Owing to a high starch supply in the morning meal, the concentration of the functional bacteria in the colonic content averaged 7.8 log CFU/ml, 5.9 NPM/ml, 6.9 and 7.3 CFU/ml for total anaerobic, cellulolytic, amylolytic and lactic acid-utilising bacteria, respectively. Consequently, providing horses with pelleted or steam-flaked instead of ground barley forms may limit the negative impact of starch on fibre digestibility in horses fed a high level of starch in the morning meal (0.27% BW). Moreover, the fibre-to-starch ratio fed in this experiment did not cause any digestive upset.     

Equine pre-caecal and total tract digestibility of individual carbohydrate fractions and their effect on caecal pH response

The working hypothesis was that a minor postprandial caecal pH decline would affect apparent total tract digestibility (ATTD) of the fibre fraction in horses and, hence, that soluble fibre would amplify fermentation and consequently increase ATTD of fibre. This study was a 4 × 4 Latin Square design with a sequence of 17 days adaptation to the ration followed by 8 sampling days. The feed rations consisted of only timothy hay (Group H), hay plus molassed sugar beet pulp combined with either whole oats (Group OB) or barley (Group BB) and hay plus loose chaff based concentrate (Group M). Four horses fitted with permanent caecal cannulas and collection harnesses were used. A pH electrode with logger was inserted through the cannula and caecal pH was recorded at 1 min intervals for 8 h. The mobile nylon bag technique was used to quantify pre-caecal loss (PCL) of individual feedstuffs. Fibre was analysed as dietary fibre (DF), non-starch polysaccharides, soluble non-cellulosic polysaccharides (S-NCP), insoluble non-cellulosic polysaccharide (I-NCP) and neutral detergent fibre. The ATTD of the S-NCP fraction was above 0.8, which was 60% higher than for the I-NCP fraction. The PCL of starch were 0.98 (oats) and 0.75 (barley). The BB diet lowered (p < 0.001) postprandial caecal pH more than the other diets and a significant correlation was found between the lowest pH and ATTD of I-NCP (r = ?0.66; p = 0.005). In conclusion, this study successfully measured the in vivo digestibility of individual fibre fractions and found that S-NCP was more digestible than the I-NCP, and that a single meal of unprocessed barley was sufficient to decrease caecal pH to such an extent that the fibre digestibility of the whole diet was negatively affected.