Maataloustieteellinen Aikakauskirja Vol. 59: 355—360, 1987 Effects of dietary supplement of methionine and lysine on blood parameters and fur quality in blue fox during low-protein feeding JOUKO TYÖPPÖNEN 1 , HANS BERG 2 and MAIJA VALTONEN 3 ' College of Veterinary Medicine, Department of Biochemistry, BOX 6, SF-00551 Helsinki, Finland 2 Finnish Fur Breeders Association, BOX 92, SF-65101 Vaasa, Finland 3 Finnish Fur Breeders Association, BOX 5, SF-01601 Vantaa, Finland Abstract. Four groups of blue fox (Alopex Lagopus) were fed from weaning to pelting with feed of two different proteinlevels. The metabolizable energy (ME) from protein amounted to 35/30 % in the control group and to 22/18 % in three low-protein groups during the early and late growth period, respectively. One of the low-protein groups received an unsupplemented diet. The second low-protein diet was fortified with methionine, and the third with methionine and lysine to the same level as in the control diet. Hematological values, urea and creatinine were lower in all low-protein groups as compared to the control group. The activities of amino acid metabolizing enzymes ASAT, ALAT and GOT in plasma were lower in the low- protein groups although the relative sizes of the liver and kidneys were greater. The lowered protein content in the feed was sufficient for growth, and only a slight negative effect on fur characteristics was observed. The dietary supplementation of methionine and lysine yielded no improvement in the fur quality or other parameters as compared to the unsupplemented low-protein feed, indicating that there was no deficiency of these amino acids in these low- protein feeds. Index words; methionine, lysine, low-protein feeding, blue fox Introduction In order to produce high-quality furs the feeds for fur-bearing animals contain a rela- tively high proportion of energy as protein. At the same time, protein is a decisive price factor in feeds. Moderately decreased protein content in mink feed has reduced feeding ex- penses without affecting the quality of the fur (Glem-Hansen 1980, Berg et ai. 1983, Työp- pönen et ai. 1986). Attempts to compensate a markedly lowered protein content in mink feed by the addition of some essential amino acids have not been very successful (Milova- nov 1963, Jorgensen & Glem-Hansen 1970, Skrivan 1977, Työppönen et ai. 1987). The present paper describes an experiment where the possible beneficial effects of supplemental 355 JOURNAL OF AGRICULTURAL SCIENCE IN FINLAND https://www.c-info.fi/en/info/?token=hmi9RWLuw_GAxKBc._SqVlbi9eILyAZ-3GiPF3Q.eJ49LeJ5auHXXr-pojRhKmqi5yiLJPLwbXagQM2icfqG0YVBdt3lgbvOUgQLz2IL-VBxz9Jx9fWVUyH0BxRJOjp-TeKdcECNmk_rUWa15fF6KsQMYC-lqhu6vDq4h1PZ4FRb6hglcgihrM2oQELn7AiAY_PvhR4fj0RVMXWXjlWX-pu6DN8r2W3SigkR5QojgDF9RKpcCDS2lG_VMhFs67ilzR1fbg methionine and lysine were studied in blue fox fed with diets of low protein content. Materials and Methods Animals and diets Four groups of healthy weaned male blue fox (Alopex lagopus) were used in the ex- periment. The groups consisted of 30 foxes, housed individually in cages. The control group was fed with a diet of standard protein content, i.e. 35 % of metabolizable energy (ME) from protein, from weaning to the end of August and 30 % from September to pelting (Table 1). The three low-protein groups received 22/18 °7o of ME from protein during the early/late growth period. One of the low-protein groups received an un- supplemented diet, the second diet was supple- mented with methionine (DL-Methionine, Feed Grade, 98 %), the third with methionine and lysine (L-Lysine, Monohydrochloride, 98 %). The levels of methionine and lysine added in the low-protein feeds shown in Table 2 were calculated to be equivalent to the control diet as based on the methionine and lysine content in the raw materials (Berg 1986). At pelting time, in the beginning of Decem- ber, blood was collected by cardiac punc- ture into heparinized tubes, and hematologi- cal parameters were determined. For chemi- cal analyses, plasma samples were stored at —2O °C until analysed. After blood sampling, the foxes were killed, weighed and the pelt length was measured. The quality and colour of the fur were graded at Finnish Fur Sales Ltd. Table 1. Composition (%) of experimental diets during early (I) and late (II) growth period. Control Low-protein II I II 15.0 16.0 12.0 13.0 6.0 5.0 6.0 2.0 2.0 10.0 4.0 4.0 5.0 2.0 2.0 2.5 2.0 2.5 8.5 8.0 11.5 8.5 8.0 11.5 1.2 1.0 1.2 5.0 6.2 7.8 1.0 1.2 1.0 1.2 24.1 42.8 39.3 37.7 32.6 38.4 2.6 1.8 1.7 12.3 8.4 8.1 8.5 8.8 10.2 14.3 13.6 18.5 30.1 22.2 18.2 45.2 51.6 50.8 24.7 26.2 30.9 17 150 18 070 17 900 28.0 20.7 17.0 I Slaughter offal 16.0 Cod offal 14.0 Lessen Sand Eel 7.0 Herring-fish 10.0 Fish meal 3.0 Fish silage 2.0 Wheat 6.5 Wheat, precooced 6.5 Oats bran 1.0 Fat mixture" 3.0 Brewer's yeast 0.5 Vitamin and mineral mixture 1.0 Water 29.5 Dry matter 31.6 Ash 2.4 Protein 11.5 Fat 6.4 Carbohydrate 11.3 Distribution of metabolizable energy (ME) percent from protein 34.7 percent from fat 41.7 percent from carbohydrate 23.7 ME, kJ/kg dry matter 16 740 Apparently digestible protein g/100 kj 32.3 a 60 °?o animal fat, 40 % soybean oil 356 Analytical methods Hemoglobin (Hb), hematocrit, and leuko- cyte count were determined by standard meth- ods (Schalm et al. 1975). Plasma urea was analysed according to Gutmann & Bergmeyer (1974), creatinine with Jaffe reaction (Slot 1965), albumin as described by Gindler & Westgard (1973) and total protein according to Weichsel- baum (1946). Aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT) and gamma-glutamyl transferase (GGT) were determined according to the Committee on enzymes (1974). All the chemical analyses de- scribed above were performed with a Gilford System 3500 Computer Directed Analyzer. Between-group comparison was performed using Student’s t-test. Results and Discussion Blood hemoglobin and hematocrit were significantly reduced in fox fed a low-pro- tein feed as compared to the control group (Table 3). Low-protein feeding in mink has resulted in decreased (Työppönen et ai. 1986) or unchanged (Työppönen et ai. 1987) hema- tological parameters. Leukocyte counts were similar in all groups of blue fox (Table 3). The content of urea and creatinine in plas- ma tended to be lower in low-protein groups as compared to the control group (Table 4). The lowered plasma urea concentration re- flects the smaller amount of protein avail- able for energy production in these animals. A similar decreasing tendency in plasma urea has previously been observed in mink on low- protein rations (Työppönen et ai. 1986, Työp- pönen et ai. 1987). Plasma creatinine content correlates with muscle mass of the body. Thus, the slightly lowered creatinine content in low-protein groups probably reflects the slower rate of muscle protein synthesis and turnover as compared to the control group (Table 4). Albumin and total protein content in plas- ma were similar in all groups except for the low-protein group supplemented with me- thionine and lysine where a significant de- crease of albumin and an increase of total protein content were observed (Table 4). The reason for this phenomenon remained un- known, but increased content of plasma pro- teins has previously been observed also in Table 2. Protein levels and amino acid supplements in experimental diets. Group Early growth period Late growth period Protein Met Lys Protein Met Lys (% ME) (g/MJ) (g/MJ) (% ME) (g/MJ) (g/MJ) Control 35 30 Low-protein 22 18 Low-prot +Met 22 2.68 18 3.35 Low-prot +Met +Lys 22 2.68 7.25 18 3.35 9.38 Table 3. Hematological values and leukocyte count at pelting time (MeanlSD, n= 10). Control Low-protein Low-protein Low-protein + Met + Met + Lys Hemoglobin (g/1) 171.416.7 154.6+15.1" 163.2 + 9.1* 159.6 + 7.l** Hematocrit (%) 46.912.2 42.9 + 5.5** 46.012.9 44.5 + 2.o** Leuk (lOVmm') 7.613.2 9.2 + 5.5 8.513.6 8.612.6 * P<0.05; ** P