Articles 61-70

Dietary supplementation of polyunsaturated fatty acids in cats

U. Wehr, Sonja Wilhelm, D. Ranz, W.A. Rambeck

Institute for Animal Physiology, Physiological Chemistry and Animal Nutrition, Ludwigs-Maximilians University Munich, Germany

All vertebrate species so far studied have been shown to have a dietary requirement for polyunsaturated fatty acids (PUFA) which are essential for growth, development and health. In vivo and in vitro experiments suggest that dietary intake of PUFA can affect bone remodeling directly or indirectly. Like other mammals cats are not able to synthetize linoleic acid (LA, 18:2n-6) and alphalinolenic acid (ALA, 18:3n-3). These fatty acids are further converted into their respective essential long-chain metabolites of the n-6- and the n-3-families by several reactions of desaturation and elongation.Unlike other mammals cats lack the enzyme D-6-desaturase (Rivers et al.) and thus, the capacity to convert LA into arachidonic acid (AA, 20:4n-6) and ALA into eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3). As a consequence the adequate dietary provision of the above mentioned fatty acids presents a major point of interest in the nutrition of the cat. The aim of this study was to investigate the influence of omega-3 fatty acids on the serum fatty acid pattern and the effect on bone metabolism in cats. For this purpose a feeding study was performed with 16 European short-hair cats and a duration of 20 weeks (including a preperiod, test period 1, wash out period, test period 2). Two diets produced for this purpose and differing only in their source of fat were fed. Beef tallow was used in the control diet and fish oil in the test diet. Both diets contained nearly equal amounts of LA, ALA and AA whereas EPA and DHA were 0,095 % and 0,058 % in the test diet compared to 0,006 % in the control diet. Both diets were considered balanced in their mineral, vitamin and amino acid content.The animals were separated into two groups with regard to their age, sex and weight. After a preperiod (4 weeks) with the control diet group 1 was fed for 4 weeks the test diet and group 2 the control diet, followed by a 6 week wash-out period with the control diet. In test period 2 (4 weeks) group 1 was fed the control diet and group 2 the test diet. All animals were regularly clinically examinend and found in a good condition. Blood and urine samples were taken at the end of every period. Alkaline Phosphatase (serum) as a marker of bone formation and desoypyridinoline (urine) as a marker of bone resorption were assesed. Serum fatty acids from blood samples, taken at the beginning and at the end of the test period 1, were analysed by gaschromatography. Under our experimental conditions, in contrast to what has been reported in humans and in rats, no influence of omega-3 fatty acids on biochemical markers of bone turnover was observed. In both groups at least a 13-fold increase in EPA and a 4-fold increase in DHA was found. The results indicate that the serum level of n-3 polyunsaturated fatty acids may be increased by feeding a diet rich in n-3 fatty acids in healthy cats.

Rivers J. et al,1976. Proceedings of the Nutrition Society 35, 69A.

A model for the development of taurine deficiency in dogs by the use of cholestyramine

C.L. Tôrres, A.J. Fascetti and Q.R. Rogers

Department of Molecular Biosciences, School of Veterinary Medicine, University of California - Davis, USA

Cholestyramine is a resin used in human medicine to lower plasma cholesterol by enhancing bile salts excretion. Since taurocholic acid is the main bile salt secreted by the dog, we hypothesized that by feeding cholestyramine to dogs, taurocholic acid excretion would be enhanced and negative taurine balance would occur. The purpose of this study was to determine whether the use of cholestyramine depletes body taurine pools in dogs. Twelve adult dogs (29 - 43 Kg BW) were fed an experimental lamb-meal and rice-bran diet (18% Crude Protein, 14% Crude Fat, DM) to maintain body weight constant. At week 12, the experimental group (n=6) was given 4 grams of cholestyramine/day, added to their diet. Twelve weeks later the dose was increased to 8 grams of cholestyramine/day. The control group (n=6) received no cholestyramine throughout the study. At week 28, both groups were switched to a second batch of food (16% Crude Protein, ~ 21% Crude fat, DM) to enhance the rate of taurine depletion. Blood was collected every 4 weeks and muscle biopsies were taken at weeks 0, 4, 12, 20, and 36. Free catch urine was collected at weeks 0, 12, 28, and 36. Taurine concentrations were determined in plasma, whole blood, skeletal muscle and urine. Plasma taurine concentrations in the control group did not change over 40 weeks. In contrast, plasma taurine concentrations from the experimental group dropped to 21 nmol/mL by week 40. At this point, five of six dogs were below the critical range for taurine deficiency in plasma (< 40 nmol/mL). Whole blood taurine concentrations from the control group initially increased, then decreased to the initial values by week 20, and remained constant thereafter. By week 40, three of six dogs in the experimental group had whole blood taurine concentrations below 150 nmol/mL (range: 32 – 184 nmol/mL), whereas all dogs in the control group were above 210 nmol/mL (range: 216 – 270 nmol/mL). Muscle taurine concentrations and urinary excretion of taurine were also significantly lower in the experimental group compared to the control. These results indicate that it is possible to induce taurine deficiency in healthy adult dogs. This model for taurine deficiency promises to be an useful aid in studying the metabolic and pathological effects of taurine deficiency in dogs.

Six months taurine or methionine supplementation in Newfoundland Dogs suffering from low whole blood taurine

R Willis1, G. Desprez3, J. Dukes-McEwan2, V. Biourge3, R.C. Backus4, Q.R Rogers4

Hospital for Small Animal, 1University of Glasgow and 2University of Edinburgh, UK, 3 Royal Canin, Aimargues,4France, Dept of Mol. Biosciences, Un. California, Davis,USA.

Low blood taurine has recently been documented in a substantial proportion of Newfoundland dogs.1 In that population, blood taurine levels were found to be significantly lower in dogs with dilated cardiomyopathy (DCM) compared to normal dogs. The rationale for this study was therefore to investigate whether taurine deficiency in Newfoundlands could be corrected by taurine and/or methionine supplementation.

Material and methods:
Fifty three dogs with whole blood taurine (<200nmol/ml) were identified and echocardiography was used to classify dogs as either normal, having echocardiographic abnormalities that may precede dilated cardiomyopathy (such as decreased contractility or left ventricular enlargement) or having dilated cardiomyopathy. The dogs with DCM received 1000mg crystalline taurine PO q12h and the remaining dogs were age and sex matched before being randomly assigned to receive 250mg taurine PO q12h or methionine 750mg PO q12h and 4 dogs were assigned to receive a proprietary giant breed diet. Heperanized whole blood and urine were collected initially (To) and after 3 (T3m) and 6 (T6m) months of supplementation. Samples were frozen at –20°c pending analysis. Taurine was measured in plasma with an amino acid analyser following protein precipitation and filtration. Urine creatinine was assayed with a commercialy available enzymatic kit. Data were analyzed by repeated measure ANOVA. Data are expressed as a mean ± SEM.

48 dogs completed the study. Three dogs were excluded because of other pathologic conditions and 2 dogs were lost to follow-up. Whole blood taurine increased in all dogs from 144±8 nmole/ml at T0 to 324±14 nmole/ml at T3m and 275±10 nmole/ml at T6m. No difference was observed based on source and amounts of supplementation. Urine Taurine/creatinine ratio was minimal at baseline and increased significantly following methionine or taurine supplementation. More taurine was excreted in urine of dogs given the highest level of taurine.

These results suggest that 250 mg of taurine or 750 mg of methionine PO q12h as well as a dry expanded diet containing 1000 mg taurine/kg, as fed, will normalize taurine status in taurine deficient Newfoundland dogs. In the dogs of this study, low taurine status could not be explained by higher taurine losses nor their inability to use methionine as a precurssor.

1. Dukes-McEwan, J., Biourge, V., Ridyard, A., Corcoran, B. M., Rogers, Q. R., and Backus, R. C. Dilated cardiomyopathy in Newfoundland dogs: association with low whole blood taurine level. Proceedings of the British Small Animal Veterinary Association Congress J.Small Anim Pract 2001.

The minimal dietary lysine requirement of kittens for maximal growth

J.G. Morris and Q. R. Rogers

Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616

Three experiments using purified diets were conducted to determine the minimal lysine requirements of kittens for maximal growth. The diets used in all experiments were of the same basic composition (g/kg diet): isolated amino acids 240, chicken or turkey fat 250, starch 290.6, glucose 150, mineral mixture 40, sodium acetate 16.4 (to balance the hydrochlorides in arginine, histidine and lysine), vitamin mixture 10 and choline chloride 3. Diets were maintained isonitrogenous by substituting alanine for lysine. Kittens had free access to the diet at all times. Before entering the experiments weaned specific-pathogen-free kittens were accustomed to a complete purified diet.

In the first experiment, duplicate 5 x 5 Latin squares (one square for male and the other for female kittens) with 10 day periods were used. The five concentrations of lysine (free base) used were 5.5, 6.0, 6.5, 7.0, and 11 g/kg diet. Daily body weight gain was linearly related to lysine concentration in the diet from 5.5 to 7.0 g /kg diet (r2 = 0.980), but kittens given the diet containing 11g lysine/kg had higher weight gains (mean ±SEM) of 15.2 ± 1.7 versus 13.3 ± 3.3 g/day respectively These results indicate that the lysine requirement is greater than 7.0 g/kg diet.

In experiment 2, duplicate 6 x 6 Latin squares were used, one square allocated to six male kittens and another to six female kittens with 10 day periods. The six concentrations of lysine (free base) in the diets used were 4.0, 5.0, 6.0, 7.0, 8.0 and 11 g/kg. Body weight gain (g/day) was linearly related (r2 = 0.985) to lysine concentration in the diet for the treatments 4 to 8.0 g lysine/kg diet. Rate of gain was not significantly different between kitten given 8.0 and 11.0 g lysine/kg diet. These results indicated that the requirement for lysine is not greater than 8 g/kg diet.

In the third experiment a duplicate 4 x 4 Latin square design was used with dietary concentrations of 6.0, 7.0, 8.0 and 9.0 g lysine (free base)/kg diet. When kittens were given the diet that contained 8.0 g lysine/kg diet they had significantly higher rates of daily gain than when given diets containing 7.0 g lysine/kg, but not significantly different than kittens given the diet containing 9.0 g lysine/kg.

These three experiments indicate that the lysine requirement of kittens for maximal growth is 8.0 g (free base) lysine/kg diet in the free form. Higher dietary concentrations of lysine would be required in practical diets that have a lower lysine bioavailability than free lysine.

Hair pigmentation can be affected by diet in dogs

V. Biourge, R. Sergheraert

Centre de Recherche Royal Canin, Aimargues, France

There are reports from breeders that coat color of dogs changed from black to reddish brown when fed certain commercial petfoods. Until recently, this « Red Hair Syndrome » has been considered as anecdotal and unfounded. Lately, it has been reported that levels of tyrosine (Tyr) and phenylalanine (Phe) required to support maximal melanin synthesis in cats were above current recommendations for growth.(Yu et al. 2001, Morris et al. 2001) The purpose of this study was to evaluate if a similar observation could be made in dogs.

Materials and methods:
Twelve black puppies (6 Newfoundlands (6 sisters), 6 Labradors (3 brothers and 3 sisters from 2 different litters) were weaned on a large breed commercial puppy diet. They were then divided in 3 groups matched for breed and sex, fed 3 diets with similar guarantee analysis (A,B,C) but with levels of Phe+Tyr in diet A = 1.9 and diet B = 2.6 times the requirements recommended for growth by the American Association of Feed Control Official (AAFCO). Diet C was Diet B coated with free Tyr so to reach 3.2 times AAFCO requirements. Food intake, bodyweight and coat color were monitored for a year. Hair samples were collected monthly, pictures taken bimonthly and plasma samples for amino acid profiles every 3 months.

Dogs remained healthy and showed similar growth patterns on the 3 diets. After 2 months, hair was red in animals fed diet A, and was darker in animals fed diet C than in those on diet B. After 5 months of feeding, the coat of dogs fed diet A appeared reddish brown, and it was possible for a blinded researcher to distinguish between dogs fed diet B or C based on the intensity of the black color. Over the growth period, plasma tyrosine dropped in dogs fed diet A and B whereas it raised in dogs fed diet C supplemented with free Tyr.

In dogs, diet can affect hair pigmentation and could explain the « red hair syndrome » reported by breeders. Addition of free available Tyr to the food can prevent the « Red hair syndrome » and optimize hair pigmentation, even for diets that have a level of Phe+Tyr above current recommendations.

Yu S et al. Effect of low levels of dietary tyrosine on the hair colour of cats. J Small Animal Practice, 2001 :42,176-180.
Morris JG et al. « Red hair » in Black cats is reversed by addition of tyrosine to the diet. Proceeding of Waltham Symposium, 2001 :26

Feeding type (conventional versus organic) and lysine/energy ratio influence meat and carcass characteristics of organic fattening pigs

S. Millet*, M. Hesta*, M. Seynaeve#, E. Ongenae#, S. De Smet#, G.P.J. Janssens*

* Laboratory of Animal Nutrition, Ghent University, Heidestraat 19, B-9820 Merelbeke # Department of Animal Production, Ghent University, Proefhoevestraat 10, B-9090 Melle

As organic pigs have more space allowance and an outdoor area, and as the stable is not climatised, a higher basal energy requirement can be expected for organic pig fattening through increased energy needs for activity and thermoregulation. Because of specific feed formulation and the production of the ingredients according to organic guidelines, this can also affect meat and carcass characteristics. The results of two experiments on this topic will be presented.

Material and methods
In the first experiment, 2 groups of 32 pigs, the one grown and housed in a conventional way, the other in an organic way, were divided in 8 groups of 4 animals. In each stable, 4 groups received a conventional feed, the others an organic one, implying four replicates per diet and housing combination. The organic feed was formulated following the European regulations on organic farming, and the digestible lysine content was formulated to a 15% lower lysine content. In the second experiment, a group of 36 pigs was divided over 9 groups of 2 barrows and 2 gilts and randomly divided over three diets with either a high a medium or a low lysine content, implying three replicates per diet. The lysine content of the low lysine feed was 20% lower than the high lysine feed. In both experiments there was measured a set of carcass and meat characteristics.

In the first experiment, the organic diet led to a higher ultimate pH in loin and ham, a higher CIELAB a* score (redness) and a lower CIELAB L* score (lightness). The drip losses tended to be lower on the organic feed. Intramuscular fat content was higher on organic than on conventional feed. Meat percentage did not differ between the groups. In the second experiment, dietary lysine content influenced meat percentage and fat thickness. Differences in meat quality parameters could not be demonstrated.

These data allow to conclude that dietary lysine/energy ratio does not have a major influence on meat quality within the tested range, whereas it can influence meat percentage by changing fat thickness. Organic feeding can influence meat colour and ultimate pH as well as intramuscular fat content. This might be due to the ban of synthetic amino acids in the organic feed and to the lower lysine content. This study was supported by the Belgian Ministry of Small Enterprises and Agriculture.

BioProtein as protein source to growing mink kits and slaughter chickens -energy expenditure and nitrogen metabolism

A-H. Tauson, A.L. Frydendahl Hellwing, A. Chwalibog

The Royal Veterinary and Agricultural University, Copenhagen, Denmark

BioProtein is a bacterial protein grown with natural gas as carbon and energy source and ammonia as nitrogen (N) source. The crude protein content is ca 70% and the amino acid composition is resembling that of fish meal although the lysine content is somewhat lower. The tryptophan content is high. BioProtein contains ca 7% RNA and 2% DNA. Its apparent faecal N–digestibility is 79% (mink), and 81% (chicken) (Skrede et al., 1998). The objective of this study was to evaluate the effect of dietary supply of BioProtein on N–balance and energy expenditure (EE) in mink and chickens as representatives of rapidly growing animals.

Materials and methods
Both studies were carried out in 5 balance periods each with a 4 days total excreta collection period and comprising a 22 h respiration experiment by means of indirect calorimetry in an open-air circulation system. The mink study was carried out with 16 male mink kits of the standard brown colour type measured from the age of ca 2 months until they were 6 months old. Four dietary treatments were used and BioProtein replaced fish meal (LT quality) on an iso-N and iso-energetic basis. BioProtein supplied 0, 20, 40 and 60% of the digestible protein of the respective diets. The chicken study comprised 4 diets, each in 3 replicates. BioProtein replaced fish meal (LT), and made up respectively 0, 2, 4 and 6% of the diets. The initial 72 animals in week 1 were reduced to 24 in week 5. During weeks 1 and 2 groups of animals were measured in the respiration chambers (6 and 5, respectively), but from week 3 single animals were measured. SAS procedure MIXED was used for repeated measures analyses.

Results and conclusion
Food intake and live weight of the mink kits were not significantly affected by dietary level of BioProtein, but there was a tendency for decreasing values with increasing BioProtein supply. The apparent N digestibility (ADN) of the diets decreased with increasing BioProtein content whereas the amount of retained N (RN) was similar for all diets. The utilization of the digested N (DN) expressed as RN/DN was lowest for the BioProtein free diet while diets providing 20 and 40% of DN from BioProtein showed significantly higher RN/DN values. The age of the animals had a strong influence on ADN, which increased as the kits grew older, RN which declined and RN/DN which first declined and then levelled out. Energy expenditure was almost identical for the 4 diets and ranging from 647 to 660 kJ/kg0.75, whereas period effects were strongly significant and values decreasing from 828 (period 1) to 476 (period 5) kJ/kg0.75. In the chicken experiments animal food intake and gain were independent on diet, but strongly affected by period. Similar to in the mink experiment neither N metabolism nor EE were affected by diet, but strongly affected by period. Again, EE was almost identical between diets (range 849 to 869 kJ/kg0.75) but declining significantly from period 2 onwards with progressing age of the chickens (847, 975, 944, 824 and 688 kJ/kg0.75 in periods 1 through 5). In conclusion, BioProtein at the dietary levels used here did not affect N metabolism and energy utilization of growing mink kits and chickens.

Skrede, al., 1998. Anim. Feed Sci. Techn. 76, 103-116.

Rumen bypass of free methionine and lysine for double-muscled Belgian Blue bull

E. Froidmont1/2, P. Rondia1/2, Y. Beckers1, A. Thewis1

1Faculté universitaire des Sciences agronomiques, Passage des Déportés 2, 5030 Gembloux, Belgium
2Département Productions et Nutrition animales, Rue de Liroux 8 – 5030 Gembloux, Belgium

Double-muscled Belgian blue (dmBB) bulls have higher amino acid (AA) requirements than other beef cattle (Froidmont et al., 2000, 2001). Methionine (Met) and lysine (Lys) are the most limiting AA in several dietary conditions. Because rumen protected AA are not economical for such animals, our study investigates the proportion of these AA, supplied on a free form, susceptible to escape from rumen fermentations and be digested in the small intestine.

Six growing dmBB bulls (257 ± 9 kg), fitted with fistulas in rumen, duodenum and ileum, received a diet containing 13% straw and 87% concentrate, at an intake level of 85 g/kg0.75. Animals were submitted to three 1-d treatments consisting to supply in the rumen, during the morning meal, 40 g Met, 60 g Lys or 40 g Met + 60 g Lys in a cross-over design. Two days separated each treatment. At the beginning and at the end of the cross-over periods, two control periods were realized during which animals did not receive any AA supplement. Concentrations of Met and Lys in the rumen fluid were measured 1, 2, 4, 6, 8, 10 and 12 hours after AA administration. Plasma Met and Lys contents were also determined 3 h after treatments. CoEDTA was used as liquid phase marker in order to determine the volume and the outflow rate of rumen fluid as well as the outflow kinetics of AA according to equations proposed by Volden et al. (1998).
During control periods, free Met and Lys contents in the rumen fluid were negligible. Volume and outflow rate of rumen fluid did not vary between treatments and reached respectively 28.9 L and 9.5 %/h.

Total amounts of free Met escaping from rumen fermentations reached 15.7 ± 2.5 g/d and 13.9 ± 2.6 g/d when this AA was supplied alone or simultaneously with Lys and did not differ between these treatments (P > 0.05). Amounts of Lys leaving the rumen intact reached respectively 27.5 ± 5.5 g/d and 26.6 ± 5.5 g/d for individual or simultaneous supply and did not differ with the mode of administration (P > 0.05). Comparatively to control periods, a supplement of Met and Lys increased their plasma concentrations by 513 and 133%, respectively. This confirms the high availability of free AA bypassing the rumen. In this study, 37% of Met and 45% of Lys escaped from rumen fermentation and arrived into the duodenum. Bypass rates of AA were higher than those mentioned previously for dairy cows (Volden et al., 1998). The reason could come from the smaller rumen volume in growing dmBB bulls (29 vs 70 L), causing higher AA concentrations in the rumen fluid for a given AA supply. High AA concentrations decrease desaminase activity in rumen fluid and could increase, by this way, the proportion of free AA bypassing the rumen. Since the price of free AA are until five times lower than protected ones, their utilization in dmBB bull feeding appeared to be interesting to correct the AA pattern of metabolizable protein.

Froidmont E. et al., 2000. J. Anim. Sci. 78:233-241.
Froidmont E. et al., 2002. Can. J. Anim. Sci. 82: in press
Volden H. et al., 1998. J. Anim. Sci. 76: 1232-1240

Nitrogen requirements for maintenance of captive Aceros- and Buceros Hornbills

SG Foeken1, M de Vries1, EG Hudson, MA2, CD Sheppard PhD3, ES Dierenfeld PhD4

1 Van Hall Institute, P.O. Box 1528, 9801 BV Leeuwarden, The Netherlands;
2 St. Catherines Island Wildlife Survival Center, Midway, GA, 31320 USA;
3 Department of Ornithology, Wildlife Conservation Society, Bronx, NY, 10460 USA;
4 Department of Wildlife Nutrition, Wildlife Conservation Society, Bronx, NY, 10460 USA

In recent years hornbills have been identified as a group in need of proper husbandry guidelines and a priority for captive breeding, because of their threats in the wild and low reproductive successes (successfully raised chicks) in captivity. Diet could be a key factor in developing successful programs1 However, actual nutrient requirements for hornbills have not been determined; evaluations of diets therefore can only be extrapolated from other model species. Dietary protein is metabolically important because it can supply essential amino acids and through intermediary metabolism, it can give rise to energy. Excess protein in captive diets may result in nutritional imbalances, which may lead to stress in kidney function, reduced health and breeding condition. High levels of dietary protein cause acidosis, and may contribute to a variety of conditions in birds, including pour bone mineralization, thinning of eggshells, and poor growth3 . We quantified protein intake and utilization (following methods of 4 and 5) in captive Aceros and Buceros hornbills.

The goal of the study2 was to determine protein requirement (nitrogen requirement x 6.25) at maintenance level and to test differences in this requirement within Aceros (frugivorous) - and Buceros (moderately omnivorous) hornbills. The requirements were obtained from non-invasive feeding experiments. Over two months, seven feeding-trials were conducted at St Catherine’s Island, GA, USA. Three Aceros and two Buceros species were fed homogenous isocaloric diets. A mixture of bird of paradise pellet (Zeigler Bros., Gardners, PA, USA), grapes and raisins was offered to the birds as grape-sized balls, supplemented with diced cantaloupe to maintain hydration. To vary protein level (range 10,8 – 22,6 %) within the diets, different amounts of a powdered soy protein supplement (Protein booster, Naturade, Inc., Irvine, CA, USA) were added to the mixture.

Test diets were fed for three consecutive days. Birds were weighed at the beginning and the end of each trial by training onto a perch-scale. A loss of > 5% of the bodymass would indicate insufficient dietary protein (tissue catabolism) and would halt the feeding trial. All defections and diet samples were collected for nitrogen (Kjeldahl) analysis. A four-day period, in which the bird’s regular diet was fed, separated the feeding trials. Data were analysed for nitrogen balance, nitrogen equilibrium (regression of nitrogen intake vs. nitrogen excretion), body mass and endogenous nitrogen losses. Nitrogen equilibrium occurred at 0,284 g N/BW0,75/d. Endogenous loss was 0,139 g N/BW0,75/d. No differences in N balances were found between Aceros and Buceros hornbills, indicating a similar requirement for nitrogen. The methodology of this study suggested a dietary crude protein requirement of 5,2% DM in a diet containing 16,8 kJ or 13 mg protein/ Kcal (GE) on a dry matter basis. However, this value was determined by extrapolation and not has not been experimentally determined to be adequate. In this study, the hornbills maintained body mass on a diet containing 10,8% CP (4 Kcal/g DM).

1 Dierenfeld, E.S., Conklin, N.L., Sheppard, C.D. and Grajal, A. (1991). Of Hoatzins and Hornbills: Duplicating natural diets. Proc. 9th Ann Conf. Dr. Scholl Conf.Nutrition Captive Wild Animals, Chicago.
2 Foeken, S.G., and de Vries, M. (2001). Nitrogen requirements for maintenance of captive Aceros- and Buceros hornbills. BSc thesis, Van Hall Institute, Leeuwarden.
3 Klasing, K.C. (1998). Comparative Avian Nutrition. CAB international, New York.
4 Murphy, M.E., (1993). The protein requirement for maintenance in the White-crowned Sparrow, Zonotrichia leucophrys gambelli. Canadian Journal Of Zoology 71: 2111-2120.
5 Pryor, G.S.,Levey, D.J., Dierenfeld, E.S. ( 2001) Protein requirements of a specialized frugivore, pesquet’s parrot Psittrichas fulgidus). The Auk 118:1080-1088.

Blood serum branched chain amino acids and tryptophan modifications in horses competing in long distance rides of different length.

Assenza A.°, Bergero D*., Tarantola M.*, Piccione G.°, Caola G.°

°Dept. Of Morphology, Biochemistry, Physiology and Animal Production, University of Messina;
*Dept. Of Animal Production, Epidemiology and Ecology, University of Torino.

The role of protein catabolism, and the contribution of different amino acids (in particular branched chain amino acids, BCAA) to the energy supply during long distance exercise is now well documented for human athletes. The above mentioned catabolism could led to an increase in the Tryptophan/BCAA ratio. This could subsequently induce an higher serotonine production in the brain and an early onset of the “central fatigue” during exercise. Based on these considerations, we studied the modifications of blood serum BCAA and tryptophan (Try) levels in endurance horses competing in long distance rides of different length, during exercise. We considered 4 groups of horses ( GA, GB, GC and GD); GA and GB were composed of 6 horses each, aging from 6 t 12 years, competing respectively in 20 and 50 km rides. GC was composed of 10 horses aging from 7 to 10 years, competing in a 32 km lasting ride; GD was composed of 8 horses aging from 6 to 10 years, competing in a 72 km lasting ride. All horses were Arabian or Anglo Arabian; blood samples were drawn from jugular vein both before and just after the end of the ride for all the horses.

GA (20 km) GB (50 km) mmol/l At rest End race At rest End race
Leu 98.8± 8.0 152.8±10.9* 129.6±34.8 278.8±69.5°
Val 142.5±27.5 240.6±65.3° 171.4±37.8 254.8±47.5°
Iso 70± 33.9 92.3±52.6 112.8±30.4 115.8±28.3
Try 19.7±3.6 23.3±4.9^ 15.1±1.4 12.9±3.0
Try/BCAA 0.06±0.008 0.04±0.01 0.035±0.004 0.022±0.005
GC (32 km) GD (72 km)
mmol/l At rest End race At rest End race
Leu 139.1±23.3 179.3±31.6° 134.4±15.0 69.8±5.7*
Val 148.5±19.4 186.3±36.8* 175.6±17.4 123.6±17.7°
Iso 87.3±11.4 94.3±15.1° 132.4±14.5 102.4±32.2°
Try 21.3±1.8 39.6±3.9* 15.4±2.7 30.8±8.4°
Try/BCAA 0.06±0.004 0.08±0.009 0.038±0.002 0.10±0.003°
Legend: * p<0.001; ° p<0.01;^ p<0.05

All blood serum samples were analysed for their leucine (Leu), Valine (Val), Isoleucine (Iso) and Try levels, by amino acid derivation and HPLC detection. Mean values and their standard deviations are shown in the table. Student’s T test for paired data was used to study the differences between the different sampling moments for each group (at rest vs. after race). The horses in the 72 km race had an increase in serum try and a decrease in BCAA such that the Try/BCAA ratio increased about 2 fold, perhaps indicator of fatigue in long distance rides and long lasting exercise in general.