Printer Friendly

EFFECT OF DIETS WITH HIGH METHIONINE LEVELS ON GROWTH PERFORMANCE, HEALTH STATUS, NUTRIENT DIGESTIBILITY AND NITROGEN RETENTION IN ARCTIC FOXES.

Byline: A. Gugolek, T. Wyczling, J. Strychalski, D. Kowalska, M. Konstantynowicz and C. Zwolinski

Abstract

The aim of the present experiment was to evaluate the influence of diets with high methionine content on growth performance, health status, nutrient digestibility and nitrogen balance in Arctic foxes ( Vulpeslagopus). The experimental materials consisted of 120 blue Arctic foxes divided into three equal groups. Control group (C) animals were fed diets with standard methionine content. Diets for experimental groups E1 and E2 were supplemented with liquid methionine at 3 and 6 g kg-1 fresh matter. The following parameters were determined in the study: body weight, body conformation, feed intake, length of the rearing period. Blood was sampled for hematological and serum biochemical analyses. Pelt quality was evaluated. Two digestibility trials were performed. It was found that diets with increased methionine content improved the growth performance of Arctic foxes.

Increased dietary methionine concentrations had no negative influence on the health status of foxes, and they supported protein digestibility and nitrogen retention. However, the highest dietary methionine level (6 g kg-1 fresh matter) in group E2 did not lead to a further improvement in the analyzed parameters, compared with the methionine content of diets fed to group E1 animals.

Keywords: digestibility, health status, methionine, nitrogen retention, pelt quality, Vulpeslagopus.

INTRODUCTION

The rations for carnivorous fur animals are often formulated to contain high amounts of offal-based feeds, which may lead to dietary amino acid imbalance. The amino acid content of the ration may vary depending on the amino acid content of feed ingredients. In the nutrition of farmed-raised Arctic foxes (Vulpeslagopus), an important role is played by sulphur-containing amino acids. Methionine and cystine are the first-limiting amino acids for fur animals, which have a significant effect on fur growth and quality (Dahlman et al., 2004). Currently farmed Finnish blue foxes are characterized by increased pelt size and improved fur quality, compared with their ancestors (Peura et al., 2005). Previous research has demonstrated that increased dietary inclusion levels of methionine contribute to improved growth performance and fur quality in Arctic foxes.

In the experiments conducted to date, the methionine content of fox diets ranged from 4.0 to 10.0 g kg-1 feed DM (Lorek et al., 2002a; Dahlman et al., 2002a,b, 2003, 2004; Matusevicius et al., 2004, Gugolek et al., 2012). Beneficial effects of supplementary methionine have also been observed in raccoon dogs (Nyctereutesprocyonoides) (Liu et al., 2012; Zhang et al., 2012b). In mink (Neovison vison), the optimum methionine levels were found to be 13.87 - 16.36 g kg-1 feed DM (Zhang et al., 2012a). Higher inclusion levels of methionine in fox diets have not been tested.

The objective of this study was to evaluate the influence of diets with high methionine content on growth performance, health status, nutrient digestibility and nitrogen balance in Arctic foxes, and to identify the maximum recommended inclusion rates of this amino acid in diets fed to farmed foxes.

MATERIALS AND METHODS

A total of 120 farmed blue foxes, the offspring of animals imported from Finland, were assigned to three equal groups (n = 40), with 20 males and 20 females per group. The groups were identical in terms of sex ratio and origin. The animals were placed in standard cages (1 m x 2 m x 0.8 m), with two animals (one male and one female) per cage, in the same pavilion, on a farm in the Province of Pomerania (northern Poland). The experiment began in June, when the animals were 10 weeks of age, and ended in December.

Feed and water were available ad libitum. The diets were composed of typical feed ingredients available on the Polish market (Table 1). The chemical composition, nutritional value and energy content of diets are shown in Table 2. Metabolisable energy concentration was determined based on digestibility coefficients, using the following energy conversion factors: protein - 18.8 MJ kg-1, fat - 39.8 MJ kg-1, carbohydrates - 17.2 MJ kg-1. All diets were formulated to meet the Nutrient Requirements of Mink and Foxes (1982). The experimental factor was dietary methionine content. The diets administered to control group (C) animals (AC and BC) were supplemented with methionine at the recommended level (NRC 1982). The composition of diets was validated by chemical analysis. Diets A were administered from June to September, and diets B from October to December.

Diets for groups E1 and E2 were supplemented with liquid methionine - ALIMET (88% pure) supplied by Adisseo, at 3 (AE1, BE1) and 6 g kg-1 fresh matter (AE2, BE2), i.e. approximately 2 and 4 g methionine per 100 g total protein in the ration.

Foxes were weighed at the beginning and at the end of the experiment, before feeding, within an accuracy of 0.1 kg, with the use of an automatic-indicating scale. At the end of the furring period, the body size, body conformation, fur quality and coat characteristics of foxes were evaluated in accordance with the Polish Arctic Fox Standard (1999). Feed intake, expressed as the difference between the amount of feed supplied and consumed, was determined once a week. The length of the rearing period was expressed as the number of days from birth to slaughter.

At 24 weeks of age, blood for hematological and serum biochemical analyses was sampled (approx. 5 ml) from the small saphenous vein of 10 males and 10 females, randomly selected from each group. The analyses were performed by standard methods (Winnicka, 2004). White blood cell (WBC) counts, red blood cell (RBC) counts, hemoglobin (HGB), hematocrit (HCT), platelets (PLT), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentrations (MCHC), red blood cell distribution width (RDW), mean platelet volume (MPV), glucose (GLU) and urea (UREA) levels, and the activities of creatine kinase (CK), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were determined.

In August and October, two digestibility trials were carried out on 18 females selected from six litters, and divided into three equal groups (n=6). Their genetic origin was the same as that of the animals used in the production trial. Diet A was tested in August, and diet B was tested in October. The animals were placed in individual metabolism cages for the collection of urine and faeces. A five-day experimental period was preceded by a five-day adjustment period. Water was available ad libitum, and the animals received 600 g (3.9 MJ ME) of feed once a day, at the same time. Leftovers and faeces were collected every day, and were weighed within an accuracy of 1 g. Faeces samples were frozen. Next, samples of faeces and feed were partially dried and ground. 20% sulphuric acid was used to preserve urine samples. The total volume of the collection was determined at the end of the experiment.

Foxes were slaughtered at the optimum date, when their coats were thickest, upon the approval of the Local Ethics Committee for Animal Experimentation (opinion No. 54/2007N), in accordance with the relevant EU regulations. Coat thickness was estimated with the use of organoleptic methods. Pelts were processed by standard methods, and were graded based on size, quality and external appearance according to the International Trading System. To facilitate comparison, the grades were assigned the following numbers: Saga - 1, B - 2, C - 3 (Hryckiewicz, 1994).

The following determinations were performed: nutrient content of feed, the proportion of nutrients excreted in faeces and urinary nitrogen content - by standard methods (AOAC, 2003); dry matter (DM) content - by drying at a temperature of 103AdegC; crude ash content - by mineralization in a muffle furnace (Czylok, JastrzebieZdroj, Poland) at a temperature of 600AdegC; total nitrogen - by the Kjeldahl method, in the FOSS TECATOR Kjeltec 2200 Auto Distillation Unit, ether extract content - by the Soxhlet method, in the FOSS SOXTEC SYSTEM 2043; crude fibre content - in the FOSS TECATOR Fibertec TM 2010 System. The coefficients of apparent nutrient digestibility were calculated using the formula: a-b/a, where: a - nutrient intake, b- faecal nutrient excretion.

The dietary levels of methionine and cystine were estimated with the use of the Biochrom 20 plus amino acid analyzer, Biochrom amino acid analysis reagents (Biochrom Ltd., Cambridge, England), and the following standards for amino acid analysis offered by Sigma-Aldrich: Amino Acid Standard Solution (AASS-18), L-methionine sulphone, L-cysteic acid.

Data were analysed statistically by one-way ANOVA and Tukey's HSD post hoc test, with the use of STATISTICA software (StatSoft Inc., 2007), at a significance level of p a$? 0.05. Nutrient digestibility and nitrogen balance parameters were expressed as arithmetic means +- standard deviations (SD). The results were compared within trials.

RESULTS AND DISCUSSION

No significant differences were found in the average initial body weight of Arctic foxes between groups. At 26 weeks of age, the body weights of foxes were as follows: group C - 11.5 +- 1.0 kg, group E1 - 12.8 +- 1.2 kg, group E2 - 12.4 +- 1.0 kg (Table 3). The final body weights of the animals examined in our study may be regarded as typical of Finnish giant foxes. In a study by Dahlman et al. (2003), the average body weight at slaughter of Arctic foxes of the Finnish type ranged from 10.68 kg to 11.47 kg, and in an experiment by Gugolek et al. (2012) it reached 10.99-11.47 kg. Dietary supplementation with methionine has been found to stimulate weight gain by enhancing protein synthesis in the body. Dahlman et al. (2002b) demonstrated that diets with a low content of methionine and lysine reduced the growth rate of Arctic foxes. In a study by Gugolek et al. (2012), the final body weights of Arctic foxes fed diets supplemented with methionine increased by 0.26 and 0.48 kg.

In mink, an increase in the methionine content of diets improved the weight gains of animals, but to a certain level only - a further increase in methionine concentrations had no influence on growth performance (Zhang et al., 2012a). Foxes of all groups scored the highest number of points for body size and conformation. Trunk length was higher in experimental than in control animals (group E1 - 78.3 cm, group E2 - 76.0 cm, group C - 71.5 cm). This parameter was comparable to that reported by other authors. In experiments performed on blue foxes, average trunk length was 69-72 cm and 66-69 cm, respectively (Dahlman et al., 2002a, 2003).

In the present study, dietary methionine supplementation had no influence on colour type, the purity of coat colour, body size or constitution of Arctic foxes. However, differences in fur quality were noted. The absence of differences in colour type and the purity of coat colour could be attributed to adequate nutrition in all groups, and the fact that both traits are genotype-dependent. Quality is considered to be the most important attribute of fur. Foxes from group E1 had the highest-quality furs (difference between group E1 and group C - 0.9 points, difference between group E2 and group C - 0.8 points). A correlation between fur quality and increased dietary methionine content has also been reported by other authors (Dahlman, 2002b; Gugolek et al., 2012).

The overall score for body conformation was also higher in experimental groups E1 and E2 than in the control group. The results of experiments conducted by Zhang et al. (2012c) and Dahlman et al. (2002b) revealed that methionine supplementation improved the overall fur quality of blue foxes fed the lowest protein diet. In our study, higher levels of dietary methionine speeded up fur growth by 4-7 days. The rearing period was longer in group C than in groups E1 and E2 (203.4 days vs. 197.2 and 199.6 days, respectively; statistically significant differences). Average feed intake was comparable in all groups.

The values of pelt length were similar in all groups, but Arctic foxes from experimental groups tended to have longer pelts. Average pelt length was 126.4 +- 8.1 cm in control group C, 128.7 +- 5.3 cm in group E1 and 128.4 +- 5.0 cm in E2. Handling and stretching affect pelt length. Pelt size is proportional to the final body weights and body conformation scores of foxes. Previous research has revealed a positive correlation between body weight and pelt length (Gugolek et al. 2002). The pelt length determined in our study was comparable with the values reported by Scandinavian researchers. In experiments conducted by Dahlman et al. (2002a,b, 2003), average pelt length ranged from 116 to 122 cm and from 114 to 117 cm, respectively. The pelts of foxes from experimental groups E1 and E2 were characterized by the best quality, comparable with the highest grade, Saga (1).

As expected , the results of pelt quality assessment were consistent with body conformation scores because fur parameters are known to affect overall pelt appearance.

The hematological and serum biochemical parameters of Arctic foxes are shown in Table 4. There were significant differences between groups in MCV values, which reached 59.6 +- 2.6 in group C, 55.0 +- 1.0 in group E1, and 56.8 +- 1.1 in group E2. Diets with increased methionine content had also a significant effect on RDW and MPV. Increased dietary methionine concentrations had no adverse influence on the health status of animals. The results of blood analyses were similar to those reported in earlier studies (Lorek et al., 2002; Lorek et al., 2005; Saba et al., 2008). Blood urea levels were higher in group C than in experimental groups E1 and E2, which could be due to the more desirable amino acid profile of methionine-supplemented diets. The activities of liver-specific enzymes, ALT and AST, were lower in experimental groups (non-significant differences), which indicates that methionine contributed to regulating liver metabolism and promoted normal liver function in foxes.

Similar results were reported for other carnivorous animals, cats (Fau et al., 1987) and rats (Rana and Chauhan, 2000). Methionine has many important physiological functions in the body, and it is required for the optimal growth and productivity of animals. Methionine participates in the methylation process and in the regulation of antioxidant status, and affects nutrient metabolism and cell function. Methionine and arginine are also known to play a vital role in epidermal keratinisation (Tesseraud et. al., 2009).

The results of digestibility trials are shown in Table 5. Protein digestibility was higher in groups E1 and E2 than in group C, and it reached the highest level in group E1. The digestibility coefficients of the remaining nutrients were similar in all groups. The digestibility coefficients determined in our study are specific to blue foxes. Protein digestibility did not increase in response to methionine levels exceeding 14.87 in diets A and 17.66 g kg-1 DM in diets B. The coefficients of protein digestibility were high. Dahlman et al. (2003) reported protein digestibility of 78-83%. The cited authors observed no significant differences in protein digestibility between groups of blue foxes fed diets supplemented with methionine at 4 to 10 g kg-1 DM, but they found that digestibility increased with an increase in methionine inclusion levels.

In a study by Lorek et al. (2001), crude protein digestibility reached 86-87%, and it was comparable with the values noted in groups fed diets without the addition of methionine (AC, BC).

Daily nitrogen balance is presented in Table 6. In both diets, nitrogen retention was significantly higher in groups E1 and E2 than in group C (for nitrogen retention calculated as % of N intake in diets A and B). The highest nitrogen retention calculated as % of digested N in diets A was noted in group E1 (45.8 +- 4.8), and in diets B in group E2 (51.6 +- 3.1). The effects of dietary methionine levels on nitrogen retention noted in our study are similar to those reported by Dahlman et al. (2002a, 2003) and Gugolek et al. (2012) who also found that higher methionine concentrations in fox diets were correlated with higher nitrogen retention.

In mink, an increase in dietary methionine levels to 14 g kg-1 feed DM supported nitrogen retention, but a further increase in methionine concentrations had no effect on retained nitrogen (Zhang et al., 2012b). Such a trend was also noted in our study where no significant differences were found between groups E1 and E2. It appears that the optimal amino acid ratio improves the availability of nitrogen and protein, which was observed in a study by Zhang et al. (2012c) where the most satisfactory results were reported for diets supplemented with both methionine and lysine.

Table1. Diet composition (g kg-1 fresh matter)

###Diet

###Ingredients

###AC###AE1###AE2###BC###BE1###BE2

flatfish offal###30###30###30###0###0###0

hard filleted cod offal###30###30###30###42###42###42

hard poultry offal###241###241###241###168###168###168

soft poultry offal###402###402###402###362###362###362

cooked pork offal###42###42###42###84###84###84

preserved poultry blood###16###16###16###28###28###28

meat and bone meal###30###30###30###57###57###57

sour milk###5###5###5###5###5###5

extruded barley###15###15###15###18###18###18

cooked ground wheat###76###76###76###74###74###74

wheat bran###3###3###3###2###2###2

steamed potatoes###0###0###0###82###82###82

vegetable oil###2###2###2###3###3###3

fruit and vegetables###5###5###5###4###4###4

Arbocel*###2###2###2###2###2###2

vitamin and mineral supplement###1###1###1###1###1###1

liquid methionine###0###3###6###0###3###6

water**###100###97###94###68###65###62

Total###1000###1000###1000###1000###1000###1000

Table2. Chemical composition (g kg-1DM) and nutritional value (%) of basal diets

Specification###Diet

###AC###AE1###AE2###BC###BE1###BE2

DM (g kg-1)###330.20###326.38###324.65###343.50###341.98###336.11

In DM:

Ash###71.30###71.04###71.01###78.31###78.08###78.65

Crude protein###362.11###370.62###376.09###342.40###346.12###350.53

Crude fat###264.87###259.04###254.98###262.57###260.71###258.82

Crude fibre###22.65###22.05###21.89###26.78###25.69###25.10

N-free extractives###279.07###277.25###276.03###289.94###289.40###286.90

Methionine###7.09###14.87###22.07###10.13###17.66###24.44

Cystine###2.28###2.29###2.52###2.09###2.06###2.19

ME (MJ kg-1) DM###19.61###19.84###20.02###19.41###19.33###19.33

% ME from:

protein###30.45###32.16###32.17###28.44###29.62###30.15

fat###52.20###51.11###51.30###52.85###52.06###51.52

carbohydrate###17.35###16.73###16.53###18.71###18.32###18.33

Table 3. Performance traits of foxes (mean+-SD)

###Group

Specification

###C###E1###E2

Body weight (kg)###Initial (10 weeks)###3.1 +- 0.5###3.2 +- 0.5###3.1 +- 0,4

###Final (26 weeks)###11.5 +- 1.0B###12.8 +- 1.2A###12.4 +- 1.0 A

Body conformation###Trunk length (cm)###71.5 +- 5.5B###78.3 +- 5.7A###76.0 +- 4.9A

(points)###Body size and constitution (0-6)###6.0 +- 0.0###6.0 +- 0.0###6.0 +- 0.0

###Colour type (0-3)###3.0 +- 0.0###2.9 +- 0.3###3.0 +- 0.0

###Colour purity (0-3)###2.9 +- 0.3###2.7 +- 0.4###2.9 +- 0.3

###Fur quality (0-8)###5.1 +- 1.3b###6.0 +- 1.0a###5.9 +- 1.4a

###Total scores (0-20)###17.0 +- 1.4b###17.7 +- 1.3a###17.7 +- 1.5 a

Average feed intake (g/day)###910.0 +- 170.0###905.0 +- 160.0###903.0 +- 160.0

Duration of the rearing period (days)###203.4 +- 9.0Aa###197.2 +- 7.5 B###199.6 +- 6.4b

Pelt evaluation###Pelt length (cm)###126.4 +- 8.1###128.7 +- 5.3###128.4 +- 5.0

###Pelt quality (1-3)###1.5 +- 0.2###1.3 +- 0.6###1.4 +- 0.5

Table 4.Hematological and serum biochemical parameters (mean+-SD)

Specification###Group

###C###E1###E2

WBC (109/l)###9.3 +- 0.9###14.2 +- 1.1###11.7 +- 0.5

RBC (1012/l)###8.5 +- 0.5###9.2 +- 0.4###8.8 +- 1.0

HGB (mmol/l)###18.5 +- 1.3###18.9 +- 1.0###18.8 +- 2.3

HCT (l/l)###50.6 +- 3.5###50.9 +- 1.6###50.4 +- 6.1

PLT (109/l)###195.4 +- 70.9###154.8 +- 59.7###246.4 +- 116.7

MCV (fl)###59.6 +- 2.6Aa###55.0 +- 1.0B###56.8 +- 1.1b

MCH (fmol)###1.3 +- 0.1###1.3 +- 0.1###1.3 +- 0.1

MCHC (mmol/l)###22.6 +- 0.1###23.0 +- 0.6###23.1 +- 0.6

RDW (%)###15.4 +- 0.5a###14.8 +- 0.4b###15.1 +- 0.3

MPV (%)###10.5 +- 1.1B###13.2 +- 1.1A###11.9 +- 0.90

GLU (mmol/l)###18.8 +- 10.0###20.8 +- 9.0###19.7 +- 10.3

UREA (mmol/l)###2.6 +- 0.2###2.1 +- 0.5###2.2 +- 0.8

CK (U/l)###613.0 +- 223.1###558.8 +- 277.8###679.0 +- 414.7

AST (U/l)###193.8 +- 29.5###185.0 +- 20.0###184.0 +- 20.0

ALT (U/l)###632.8 +- 258.2###510.1 +- 196.4###415.2 +- 175.4

Table 5. Effect of diets with different methionine levels on nutrient digestibility (%) in foxes (mean+-SD)

Specification###Group

###AC###AE1###AE2

DM###83.54 +- 1.02###87.56 +- 1.27###86.19 +- 1.12

Crude protein###87.72 +- 1.79b###91.55 +- 1.09a###91.07 +- 1.89a

Crude fat###97.12 +- 0.23###98.34 +- 0.55###97.38 +- 0.65

N-free extractives###65.87 +- 2.74###64.98 +- 2.05###65.04 +- 1.16

Specification###BC###BE1###BE2

DM###86.71 +- 1.08###85.48 +- 1.15###84.92 +- 0.87

Crude protein###85.77 +- 1.79b###89.05 +- 1.92a###88.76 +- 1.34

Crude fat###98.17 +- 0.19###98.12 +- 0.45###97.99 +- 0.43

N-free extractives###67.12 +- 1.66###66.26 +- 0.91###65.02 +- 2.42

Table 6. Effect of diets with different methionine levels on N balance in foxes (mean+-SD)

Specification###Group

###AC###AE1###AE2

N intake (g/day)###8.2 +- 0.1B###9.0 +- 0.1A,B###9.4 +- 0.1A

Faecal N (g/day)###1.0 +- 0.1###1.1 +- 0.2###1.0 +- 0.1

Urinary N (g/day)###4.4 +- 0.2###4.3 +- 0.4###4.1 +- 0.1

Digested N (g/day)###7.2 +- 0.2B###7.9 +- 0.2A,b###8.3 +- 0.1A,a

Retained N (retained) (g/day)###2.8 +- 0.4B###3.6 +- 0.5A###4.2 +- 0.3A

N retention as % of N intake###34.0 +- 4.0B###40.2 +- 4.7A###45.2 +- 4.0A

N retention as % of digested N###38.6 +- 4.8B###45.8 +- 4.8A###50.8 +- 3.0A

Specification###BC###BE1###BE2

N intake (g/day)###8.6 +- 0.2B###9.5 +- 0.1A,B###10.1 +- 0.1A

Faecal N (g/day)###1.0 +- 0.2###1.0 +- 0.2###1.1 +- 0.1

Urinary N (g/day)###4.6 +- 0.3###4.5 +- 0.6###4.3 +- 0.2

Digested N (g/day)###7.6 +- 0.3B###8.5 +- 0.2A,b###9.0 +- 0.2A,a

Retained N (g/day)###2.9 +- 0.5B###4.0 +- 0.5A###4.6 +- 0.4A

N retention as % of N intake###34.2 +- 5.3B,b###41.8 +- 5.4a###45.8 +- 3.1A

N retention as % of digested N###39.0 +- 4.9B,b###46.9 +- 6.4a###51.6 +- 3.1A

Conclusions: Our findings indicate that dietary supplementation with methionine at 14.87 (AE1) and 22.07 (AE2) g kg-1 feed DM from June to September, and at 17.66 (BE1) and 24.44 (BE2) g kg-1 feed DM from October to December, at relatively stable cystine levels, had a beneficial influence on growth performance, protein digestibility and nitrogen retention in blue Arctic foxes. Increased dietary methionine concentrations had no negative effect on the health status of foxes. The highest dietary methionine level in group E2 did not lead to a further improvement in the analyzed parameters, compared with the values noted in group E1.

REFERENCES

AOAC (2003). Official Methods of Analysis.17th Edn. Association of Official Analytical Chemists, Arlington.

Arctic Fox Standard (1999). Central Animal Breeding Office, Warszawa.

Dahlman, T., T. Kiiskinen, J. Makela, P. Niemela, L. Syrjala-Qvist, J. Valaja, and T. Jalava (2002a). Digestibility and nitrogen utilisation of diets containing protein AT different level and supplemented with DL-methionine, L-methionine and L-lysine in blue fox (Alopexlagopus). Anim. Feed Sci. Technol. 98: 219-235.

Dahlman, T., J. Valaja, P. Niemela, and T. Jalava (2002b). Influence of protein level and supplementary L-methionine and lysine on growth performance and fur quality of blue fox (Alopexlagopus). Acta Agr. Scand. A-AN. 52: 174-182.

Dahlman, T., J. Valaja, T. Jalava, and A. Skrede (2003). Growth and fur characteristics of blue fox (Alopexlagopus) fed diets with different protein levels and with or without DL-methionine supplementation in the growing-furring period. Can. J. Anim. Sci. 83(2): 239-245.

Dahlman, T., J. Valaja, E. Venalainen, T. Jalava, and I. Palonen (2004). Optimum dietary amino acid pattern and limiting order of some essential amino acids for growing-furring blue foxes (Alopexlagopus). Anim. Sci. 78(1): 77-86.

Fau, D., J. G. Morris and Q. R. Rogers (1987).Effects of high dietary methionine on activities of selected enzymes in the liver of kittens (Felisdomesticus). Comp. Biochem. Physiol., Part B: Biochem. Mol. Biol. 88: 551-555.

Gugolek, A., M. O. Lorek, and D. Zalocka (2002). Studies on the relationship between the body weight, trunk length and pelt size in Arctic foxes. Czech J. Anim. Sci. 47(8): 328-332.

Gugolek, A., T. Wyczling, P. Janiszewski, P. Sobiech, P. Wyczling, and M. Konstantynowicz (2012). The effect of dietary methionine levels on the performance parameters of Arctic Foxes (Vulpeslagopus). Ann. Anim. Sci. 12(3): 393-401.

Liu, H., G. Li, W. Zhong, D. Li, F. Liu, and W. Sun (2012). Supplemental dietary methionine affects the pelt quality and nutrient metabolism of raccoon dogs (Nycter eutesprocyonoides). Asian J. Anim. Vet. Adv. 7: 61-67.

Lorek, M. O., A. Gugolek, and A. Hartman (2001). Nutrient digestibility and nitrogen retention in arctic foxes fed a diet containing cultures of probiotic bacteria. Czech J. Anim. Sci. 46: 485-488.

Lorek, M. O., A. Gugolek and A. Hartman (2002). Effect of feeding pellets to arctic foxes on their performance and selected morphological-biochemical blood indices. Czech J. Anim. Sci. 47(8): 333-338.

Lorek, M. O., A. Hartman, A. Gugolek, and P. Matusevicius (2005). Effects of synthetic amino acids on morphological and biochemical blood parameters and health status of arctic foxes. Vet. ir Zoot. 30(52): 54-59.

Matusevicius, P., A. Januskievicius, A. Gugolek, and A. Zilinskiene (2004). Sintetiniom etioninoef ektyumaslapiu (Alopexlagopus L.). Vet. ir Zoot. 25(47): 71-75.

NRC (1982). Nutrient Requirements of Mink and Foxes.National Research Council.Second revised edition by the National Research Council, Subcommittee on Furbearer Nutrition.National Academic Press, Washington.

Peura, J., I. Stranden, and E.A. Mantysaari (2005). Genetic parameters in Finish blue fox population: Pelt character and live animal grading traits. Acta Agr. Scand. A-AN. 55(4): 137-144.

Rana, S. V. S. and A. Chauhan (2000). Influence of methionine and zinc on liver collagen in molybdenotic rats. Relationship with lipid peroxidation. Biol. Trace Elem. Res. 73: 85-91.

Saba, L., B. Likos-Grzesiak, B. Nowakowicz-Debek, H. Bis-Wencel, J. Martyna, and W. Wnuk (2008). Effect of synthetic antioxidant on biochemical indices in blood of arctic fox (Alopexlagopus). Annales UMCS, Lublin - Polonia Sectio EE, XXVI 3: 3-18.

Statistica P L (data analysis software system), StatSoft, Inc. 2007.version 8.0. www.statsoft.com.

Tesseraud, S., S. Metayer Coustard, A. Collin, and I. Seiliez (2009). Role of sulfur amino acids in controlling nutrient metabolism and cell functions: Implications for nutrition. Brit. J. Nutr. 101(8): 1132-1139.

Winnicka, A. (2004). Wartosci referencyjne podstawowych badan laboratoryjnych w weterynarii. Reference values of basic research in veterinary medicine. (in Polish) Wydawnictwo S G G W Warszawa.

Zhang, H. H., G. Y. Li, E. J. Ren, X. M. Xing, Q. Wu, and F. H. Yang (2012a). Effects of diets with different protein and DL-methionine levels on growth performance and N-balance of growing minks. J. Anim. Phys. Anim. Nutr. 96: 436-441.

Zhang, H. H., A. G. Yue, F. H. Liu, X.Y. Cao, F.H. Yang, and G.Y. Li (2012b). Effect of growth performance and N-balance of growing raccoon dogs fed r39+educed crude protein, lysine and DL-methionine supplementation diets. J. Anim. Vet. Adv. 11: 2187-2190.

Zhang, H. H., F. H. Yang, Q. K. Jiang, Z. G. Yue, X. M. Xing, W. L. Sung, and G.Y. Li (2012c). Effect of low-protein, DL-methionine and lysine - supplemented diets on growth performance of blue fox (Alopexlagopus) during the growing-furring period.Proc. Xth Intern.Sci. Congress in Fur Anim. Prod. 25-31.
COPYRIGHT 2017 Asianet-Pakistan
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2017 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Publication:Journal of Animal and Plant Sciences
Geographic Code:0ARCT
Date:Dec 31, 2017
Words:5175
Previous Article:Short Communication - MIR-378 INDUCES APOPTSIS OF GRANULOSA CELLS DURING FOLLICLE DEVELOPMENT IN CATTLE.
Next Article:SEMEN CHARACTERISTICS AS INFLUENCED BY SEASONAL AND CLIMATIC VARIATIONS IN NILI-RAVI BUFFALO BREEDING BULLS.
Topics:

Terms of use | Privacy policy | Copyright © 2018 Farlex, Inc. | Feedback | For webmasters