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.

Effect of exercise on apparent total tract digestibility of nutrients and faecal recovery of ADL and TiO2 in ponies.

Exercise and physical training are known to affect gastrointestinal function and digestibility in horses and can lead to inaccurate estimates of nutrient and energy digestibility when markers are used. The effect of exercise on apparent nutrient digestibility and faecal recoveries of ADL and TiO2 was studied in six Welsh pony geldings subjected to either a low- (LI) or high-intensity (HI) exercise regime according to a cross-over design. Ponies performing LI exercise were walked once per day for 45 min in a horse walker (5 km/h) for 47 consecutive days. Ponies submitted to HI exercise were gradually trained for the same 47 days according a standardized protocol. Throughout the experiment, the ponies received a fixed level of feed and the daily rations consisted of 4.7 kg DM of grass hay and 0.95 kg DM of concentrate. The diet was supplemented with minerals, vitamins and TiO2 (3.0 g Ti/day). Total tract digestibility of DM, organic matter (OM), CP, crude fat, NDF, ADF, starch, sugar and energy was determined with the total faeces collection (TFC) method. In addition, DM and OM digestibility was estimated using internal ADL and the externally supplemented Ti as markers. Urine was collected on the final 2 days of each experimental period. Exercise did not affect apparent digestibility of CP, crude fat, starch and sugar. Digestibility of DM (DMD), OM (OMD), ADF and NDF tended to be lower and DE was decreased when ponies received the HI exercise regime. For all treatments combined, mean faecal recoveries of ADL and Ti were 87.8±1.7% and 99.3±1.7%, respectively. Ti was not detected in the urine, indicating that intestinal integrity was maintained with exercise. Dry matter digestibility estimated with the TFC, ADL and Ti for ponies subjected to LI exercise were 66.3%, 60.3% and 64.8%, respectively, while DMD for HI ponies were 64.2%, 60.3% and 65.2%, respectively. In conclusion, physical exercise has an influence on the GE digestibility of the feed in ponies provided with equivalent levels of feed intake. In addition, the two markers used for estimating apparent DMD and OMD indicate that externally supplemented Ti is a suitable marker to determine digestibility of nutrients in horses performing exercise unlike dietary ADL.

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 preventive effects of two nutraceuticals on experimentally induced acute synovitis.

BACKGROUND: Nutraceuticals are often used in the management of equine osteoarthritis, but scientific evidence of their efficacy is lacking. OBJECTIVES: To study the preventive effects of two new nutraceuticals after the experimental induction of synovitis in comparison with positive and negative control treatments. STUDY DESIGN: Blinded, controlled, randomised experiment. METHODS: Twenty-four healthy Standardbred horses were randomly allocated to supplement AT (multi-ingredient, 28 days), supplement HP (collagen hydrolysate, 60 days), meloxicam (4 days) or placebo (60 days). Synovitis was induced in the right intercarpal joint by intra-articular injection of 0.5 ng lipopolysaccharide (LPS) of Escherichia coli while treatments were continued. Blood and synovial fluid were sampled before treatment, immediately prior to LPS injection, and at 8, 24 and 48 h post-injection. Synovial fluid samples were analysed for total nucleated cell count (TNCC), total protein (TP) and selected biomarkers (prostaglandin E2 [PGE2 ], interleukin-6 [IL-6], glycosaminoglycans [GAGs], type II collagen synthesis [CPII], matrix metalloproteinase [MMP]). Lameness was scored by visual examination and pressure plate analysis immediately prior to LPS injection, and at 8, 24 and 48 h post-injection. Clinical examinations were performed before treatment, immediately prior to LPS injection, at 2, 4 and 6 h post-injection, and then twice per day during the test period. RESULTS: Before treatment and intra-articular challenge, there were no statistically significant differences among the treatment groups for any of the parameters. After intra-articular challenge, the placebo group showed significantly higher synovial fluid TP, TNCC and PGE2 compared with the meloxicam group, although the model did not induce a relevant amount of lameness. Both nutraceuticals resulted in significantly lower synovial fluid TP, TNCC and PGE2 compared with placebo. No statistical differences in IL-6, GAGs, CPII or MMPs were observed among treatment groups. No adverse effects were observed. MAIN LIMITATIONS: Despite evidence of synovitis, lameness was too mild to detect. CONCLUSIONS: The preventive administration of these nutraceuticals showed anti-inflammatory effects in this validated synovitis model. Therefore, further studies of their clinical applicability are warranted.

Evaluation of methodological aspects of digestibility measurements in ponies fed different grass hays.

Methodological aspects of digestibility measurements of feedstuffs for equines were studied in four Welsh pony geldings consuming four grass-hay diets in a 4 × 4 Latin square design. Diets contained either a low (L), medium (M), high (H), or very high (VH) ADF content (264, 314, 375, or 396 g·kg DM, respectively). Diets were supplemented with minerals, vitamins, and TiO (3.9 g Ti·d). Daily feces excreted were collected quantitatively over 10 consecutive days and analyzed for moisture, ash, ADL, AIA, and titanium (Ti). Minimum duration of total fecal collection (TFC) required for an accurate estimation of apparent organic matter digestibility (OMD) of grass hay was assessed. Based on literature and the calculated cumulative OMD assessed over 10 consecutive days of TFC, a minimum duration of at least 5 consecutive days of fecal collection is recommended for accurate estimation of dry matter digestibility (DMD) and OMD in ponies. The 5-d collection should be preceded by a 14-d adaptation period to allow the animals to adapt to the diets and become accustomed to the collection procedures. Mean fecal recovery over 10 d across diets for ADL, AIA, and Ti was 93.1% (SE 1.9), 98.9% (SE 5.5), and 97.1% (SE 1.8), respectively. Evaluation of CV of mean fecal recoveries obtained by ADL, AIA, and Ti showed that variation in fecal Ti (6.8) and ADL excretion (7.0) was relatively low compared to AIA (12.3). In conclusion, the use of internal ADL and externally supplemented Ti are preferred as markers to be used in digestibility trials in equine fed grass-hay diets.

Repeated measurements of P retention in ponies fed rations with various Ca:P ratios.

This study addresses the question of whether feeding rations rich in P for a period of up to 42 d induces a positive P balance in adult ponies. Biochemical bone markers and parathyroid hormone (PTH; intact as well as whole PTH) were measured to obtain clues as to the effect of P loading on bone metabolism. The experiment had a Latin square design. Each feeding period lasted 42 d, and there were 2 balance trials (ECP1 and ECP2) within each feeding period. Each balance trial lasted 10 d (ECP1: d 11 to 21; ECP2: d 33 to 42). Six ponies aged 2.5 to 7 yr were fed a control diet that provided P and Ca according to the requirement (Control diet: 54 mg Ca·kg BW(-1) · d(-1); 36 mg P · kg BW(-1) · d(-1)), a diet high in Ca and P (HCaHP diet: 146 mg Ca · kg BW(-1) · d(-1); 121 mg P · kg BW(-1) · d(-1)), and a diet with a high P level only and Ca fed to the requirement (HP diet: 54 mg Ca · kg BW(-1) · d(-1); 122 mg P · kg BW(-1) · d(-1)). When fed the Control diet, the ponies showed a zero P and Ca balance over the 42-d period. The HCaHP diet resulted in both P and Ca retention (about 2 g Ca and P/d; P < 0.05). Phosphorus retention (about 2 g P/d) alone was observed when ponies were fed the HP diet, but P retention was only different (P < 0.05) from the Control diet in ECP1. The excretion of P in urine was reduced by greater Ca intake (P < 0.05), and Mg absorption was reduced by high P intake (P < 0.05). Plasma P concentration was raised by high P intake. Plasma Ca levels were not affected by dietary treatment. The greater (P < 0.05) P retentions observed for the HCaHP diet during ECP1 and ECP2 and HP diet during ECP1 could not be explained by processes that could have been indicated by the bone markers or PTH values. It was concluded that dietary-P-induced retention of P in ponies does not seem to be associated with altered bone metabolism in this study.

Influence of high phosphorus intake on salivary and plasma concentrations, and urinary phosphorus excretion in mature ponies.

This study addressed the question whether the concentration of phosphorus (P) in saliva of ponies is influenced by P intake. Six ponies were fed a diet high in P (HP treatment), providing 21 g P/day, and a diet low in P (LP treatment), supplying 7 g P/day. The two diets provided approximately 21 g calcium (Ca) and 6 g magnesium (Mg)/day. The experiment had an A-B-A design with treatment periods of 30 days. The ponies first received the HP diet (HP1), followed by the LP treatment and were then fed again the HP diet (HP2). Urinary P excretion was increased in both HP feeding periods and equalled approximately 7% of P intake vs. 0.5% on the LP diet. Plasma P concentration was higher for the HP treatment. The salivary P concentration ranged from 0 to 1.01 mmol P/l between ponies and there was no effect of P intake. It is suggested that saliva is not an important excretion route of P. The percentage of Ca and Mg in urine (% of intake) was higher for the LP treatment than for the HP treatments. The results of this study suggest that salivary Mg may contribute to Mg homeostasis.

The influence of calcium intake on phosphorus digestibility in mature ponies.

Literature data show conflicting results on the effect of feeding high calcium (Ca) levels on phosphorus (P) digestibility in ponies. None of the studies reported involved a dose response as to the effect of Ca intake on apparent P digestibility while keeping P intake constant. Thus, the influence of high dietary Ca level on apparent P digestibility was studied in balance trials by feeding six mature ponies three different Ca levels against a constant P intake. The ponies received 148, 316 and 535 mg Ca/kg BW/day with the low, intermediate and high Ca diet. Phosphorus intake was approximately 125 mg P/kg BW and magnesium (Mg) intake was approximately 35 mg Mg/kg BW/day. The intermediate and high Ca level decreased apparent digestibility, renal excretion and retention of P when compared with the low Ca level. However, apparent digestibility and renal excretion of P were not different between the intermediate and high Ca level. The high Ca level resulted in a retention of 66 mg Ca/kg BW/day. The percentage apparent digestibility of Ca was lower for the intermediate and high Ca level compared with the low Ca level. Magnesium digestibility was not affected by high dietary Ca level. In practice, high absolute amounts of Ca should be prevented especially when low amounts of P are fed; P digestibility will be depressed and a negative P balance may occur.

The apparent digestibility of phytate phosphorus and the influence of supplemental phytase in horses.

Availability of phytate-bound P as influenced by supplemental phytase was studied in eight horses consuming four diets in a 4 x 4 Latin square design experiment. The treatments were a control (containing a low P level, 18.4 g/d) and three high-P diets. These diets contained P as monocalcium phosphate (MCP; 43.7 g/d), myoinositol hexakisphosphate in the form of wheat and rice bran (MIHP; 41.8 g/d), or MIHP with microbial phytase (MIHPP; 42.5 g/d). The proportions of phytate-bound P were 3, 1, 55, and 56% for the control, MCP, MIHP, and MIHPP, respectively. The MIHPP diet was supplemented with 300 phytase units (FTU)/kg (as-fed basis). Feces and urine were collected quantitatively and analyzed for P, Ca, and Mg. Urinary P excretion was lower (P < 0.05) with the control diet (0 g of P/d) than with the MCP diet (1.0 g of P/d). The low urinary P excretion (0.3 g of P/d) for the MIHP diet suggested low P availability compared with the MCP diet, but apparent digestibility of P expressed as a percentage of intake did not differ (P = 0.065) between these diets. Apparent Ca digestibility was lower (P < 0.05) for the MIHP diet than for the MCP diet (26.4 vs. 42.4%). This difference may have been caused by the origin of the Ca in these diets. Phytase supplementation increased apparent Ca digestibility from 26.4 to 31.5% (P < 0.05). Magnesium was not influenced by the level of phytate in the diet. Our data indicate that phytase supplementation had more influence on Ca digestibility than on P digestibility and suggest that phytase supplementation may be beneficial for improving Ca digestibility for horses receiving a phytate-rich diet.