Physiologic nutrition studies in swine with ileorectal anastomoses. 2. The effect of nourseothricin on nutrient digestibility, amino acid absorption, protein utilization and mineral balance of a rye diet

The supplement of nourseothricin (NT) to a rye diet did not have an influence on the precaecal and total apparent digestibility of the crude nutrients or the total digestibility of the amino acids (AA). NT produced significantly higher absorption of some AA in pigs with ileo-rectal anastomoses (IRA) which were orally supplied with electrolyte solution (ES). In general, IRA pigs showed the same results with regard to precaecal apparent AA absorption influenced by the AA pattern of endogenous protein as pigs with ileal cannulae. Functions in the large intestine seem to be important for the effect of NT supplements, as NT supplements to the diet of intact animals tendentially had a positive effect on N, Ca and P balances, IRA animals, however, showed a contrary effect. In comparison with the intracaecal infusion of ES, the oral supply of the IRA pigs resulted in higher N, Ca and P balances. The level of N utilization (N balance in % of the digested N) of the IRA pigs supplied orally was equally high as that of the intact animals (both groups without NT). As derives from literature and the available N, Ca and P balances--significantly influenced by ES supplements--an additional supplement of rations poor in crude fibres of 1 g Na/animal and day seems sufficient for covering the requirement of IRA pigs of a weight of 30...40 kg. After 18 days a P supply below the requirement resulted in a significantly reduced P level (inorganic) in the serum in both animal groups, with the level of the IRA pigs being significantly below that of the INT animals. For this reason, the P requirement of fattening pigs should be fully covered in experiments with IRA pigs. Although the IRA pigs supplied caecally with ES showed typical appearances of Na deficiency, their Na level in the serum did not differ from that of the other animals.     

Prececal protein and amino acid digestibility and total crude nutrient digestibility of extracts of three rapeseed varieties, ascertained in ileorectostomized and intact swine

The apparent precaecal crude protein digestibility and amino acid absorption as well as the total digestibility of the nutrients organic matter, crude protein, crude fat and crude carbohydrates were determined of rations consisting of barley plus oilmeals of two rapeseed varieties of double quality (DQ) from Canada (Canola) and the GDR as well as of one variety of single quality (SQ) with 10 female pigs weighing between 120 and 140 kg with ileorectal anastomoses (IRA) and 4 intact (INT) female pigs weighing between 150 and 160 kg. The three rapeseed meals (RSM) were furthermore fed to IRA pigs as sole protein source together with protein-free feed. Based on the digestibilities of the crude nutrients determined with INT pigs and calculated with the difference method the energy content of RSM DQ "Canola", DQ GDR and SQ GDR could be calculated as 495, 633 and 500 EFUpig/kg DM (average: 543 EFUpig). The precaecal digestibility of the crude protein of the above mentioned RSM sorts determined with IRA pigs and calculated with the difference method amounts to 73, 76 and 75% resp. and is thus lower than the average absorption of all amino acids. The precaecal digestibilities of crude protein and essential amino acids for the mixtures calculated from the digestibility values of the individual feedstuffs barley and the above mentioned RSM largely agree with the experimentally determined digestibility values, i.e. there is additivity. On an average of the values known from literature for DQ RSM (including our own results), the precaecal digestibility of crude protein amounts to 70, of lysine to 74, of methionine to 82, of cystine to 82, of threonine to 69, of tryptophan to 72 and of isoleucine to 74%.     

Measuring energy turnover in the adult swine during feeding of rations with potato starch, potatoes, beets, pressed shreds and coarse fodder as supplements to a basic ration. 1. Energy turnover and energy utilization

25 rations with a wide variation of the content of various carbohydrates (crude fibre 36-185; water-soluble carbohydrates 25-306, starch 272-683 g/kg DM) were fed to male castrates (n = 8) of a live weight between 90 and 180 kg, and energy metabolism was measured. The rations were composed of a cereal basic ration and various feed-stuffs (potato starch-raw and soaked) potatoes (raw and steamed), sugar beet and products from it, maize pellets, dried roughage lucerne, clover, lupin, grass, rye straw meal) as supplements. The digestibility and metabolisability of the energy of the rations ranged between 88 and 62 or 86 and 60% resp. Between 2 and 4% of the consumed energy were lost in urine. The partial utilization of the metabolizable energy of the rations varied between 80% (processed supplement of potato starch) and 52% (supplement of rye straw). The rations with supplements of dried roughage were relatively well energetically utilized-between 63 and 70%. A regressively calculated difference of 17%-units was regressively calculated between the utilization of metabolizable energy of either precaecal or postileal origin.     

The energetic utilization of rations with dried concentrates, potatoes, sugar beets, apple pectin and cane sugar by growing, intact and ileorectostomized swine. 2. Comparison of results

Results of the measuring of the total metabolism of growing intact pigs (INT) and pigs with ileorectal anastomoses (IRA) are compared. The 16 comparisons are based on studies with rations of dried feedstuffs and rations containing between 30 and 50% of the DM raw or steamed potatoes and sugar beets, sucrose and apple pectin. On an average of all comparisons the relative values for the digestibility of energy, DM and the organic matter as well as for the metabolizability of the energy were between 81 and 82% (values measured at INT animals = 100). The comparison also refers to the crude nutrients, the water-soluble carbohydrates, the starch and the pectin. As a tendency, the IRA utilized the metabolizable energy better than the INT animals. The energy maintenance requirement of the IRA animals was--by 15%--significantly higher than that of the INT animals. There is not yet an answer to the question in how far comparative studies of INT and IRA animals make verified statements with regard to the differences in the energetic utilization of the precaecally and postileally digested nutrients possible. For this, further experiments will be necessary.     

Measuring of the energy turnover in adult swine during feeding of rations with potato starch, potatoes, beets, pressed shreds and coarse fodder as supplements to a basic ration. 2. Evaluation and discussion of the results for further development of energetic feed rating for swine

Energy metabolism measurings of male castrates of a live weight between 90 and 180 kg after feeding rations with a wide variety in the content of various carbohydrates (crude fibre 36-185, water soluble carbohydrates 25-306, starch 272-683 g/kg DM) formed the experimental basis of the considerations. Energy retention depended significantly on the digestibility and metabolizability of the energy, on energy concentration and the crude fibre content of the rations. By means of multiple regression analyses the energetic effect of 1 g digested matter of the carbohydrate fraction was assessed as follows: 12.9 kJ for starch, 12.1 kJ for disaccharides, 11.5 kJ for the remaining water soluble carbohydrates and 10.4 kJ for bacterially fermentable carbohydrates (BFC). There was a difference between the energetic effective value of starch and BFC. This corresponds completely to the difference in the utilization of metabolizable energy between exclusively precaecal and postileal digestion. The following conclusions are drawn for the further development of the energetic feed evaluation for pigs in the framework of the GDR feed evaluation system: --There are to be differentiated fixed values for the retention of digestible carbohydrates for the fractions starch, water soluble carbohydrates (pectin) and bacterially fermentable carbohydrates. --The influence of the digestibility of the energy in the ration on the energetic retention effect of BFC is small. The integration of these variables into an estimation equation for the energetic feed value is therefore not necessary.     

Effect of exogenous factors on prececal nutrient and amino acid reabsorption, ascertained in swine with ileorectal anastomoses. 1. Effect of the degree of grinding up of grain

Pigs fitted with ileo-rectal anastomoses (IRA) and in parallel experiments intact (INT) pigs were used to estimate the influence of the different grinding fineness of barley and wheat (coarse, medium, fine) on the apparent and true precaecal and total digestibility resp. absorption of various N free and N containing nutrients, among them crude protein and the indispensable and dispensable amino acids. Coarse grinding (25 ... 50% of the particles greater than 2 mm) resulted in significantly lower digestibility values than medium and fine grinding--with more striking differences in barley than in wheat. Precaecally most nutrients and amino acids are distinctly less digestible than at the end of the total tract. The precaecal lysine absorption determined with IRA pigs is remarkably low. The results are discussed. In order to attain a good utilization of the protein contained in cereals grains should be ground in hammermills with maximal sieve meshes of 3 mm. It is proposed to tabulate crude protein and amino acids in future on the basis of a standardized true precaecal digestibility resp. absorption.     

Precaecal and faecal digestibility of inulin (DP 10-12) or an inulin/Enterococcus faecium mix and effects on nutrient digestibility and microbial gut flora

The aim of the present study was to investigate the precaecal and faecal digestibility of inulin (DP 10-12) and inulin/Enterococcus faecium mix, and the effects of these substances on nutrient digestibility and microbial gut flora. For the experiment four of eight male pigs were fitted with an end-to-end ileo-rectal anastomosis (IRA) with preserved ileo-caeco-colic valve. The residual pigs were used as intact partner (IN). The animals received 1.5 kg/day of a diet based on corn, wheat, barley and soybean meal, supplemented with either 8 x 10(9) CFU E. faecium/kg, 2% inulin or a mixture of both substances. The digestibility trial was carried out from weeks 4 to 8 after surgery. Precaecal digestibility of inulin was assessed to be 57%. The addition of E. faecium to the diet resulted in a similar precaecal digestibility of inulin of 55%. Supplementation of E. faecium, inulin, and a mixture of E. faecium and inulin did not affect precaecal and faecal nutrient digestibility with the exception of the precaecal digestibility of CF which increased when inulin alone was supplemented. Bacterial population in the digesta of IRA and IN pigs were not affected by the experimental diets except the concentration of bifidobacteria and lactobacilli. The supplementation of E. faecium to the diet significantly decreased the concentration of bifidobacteria and the population of lactobacilli inclined to decrease when IN pigs received the probiotic diet. The combination of E. faecium and inulin prevented a reduction of enterococci in faeces of IN pigs. The daily digesta excretion (DM) tended to decrease in IRA and IN pigs when inulin was supplemented. The results indicate that inulin (DP 10-12) in pig nutrition did partly react as a prebiotic as has been confirmed for humans. A combination of E. faecium and inulin improves the survival of the probiotic strain through the upper intestinal tract and allocates the synbiotic effect. Furthermore inulin might be able to show positive effects on precaecal and faecal microbial characteristics.     

The energy metabolism of growing swine in the liveweight range of 10-50 kg. I. Study design, feed intake and digestibility

Studies of the energy metabolism at maintenance and growth levels after the feeding of rations with a crude protein content of 17-24% and 44-47% resp. were carried out with hybrid pigs of line 150 in the live weight range between 10 and approximately 50 kg. This paper gives information on the methods and the outlay of the experiment and presents results concerning feed intake, live weight development and digestibility. Feed intake increased on average with growing live weight by 30-35 g DM/kg live weight. Feed conversion ranged from 1.2 to 1.8 kg DM/kg live weight gain in the first period and from 2.3 to 3.2 kg DM/kg live weight gain in the last period. The digestibility of the energy in the rations with a crude protein content of between 17 and 24% averaged 80% and that of the rations with a crude protein content of 44-47% averaged 86%. In the course of ontogenetic development the digestibility increased up to about 30 kg LW. The influence of the nutritional level on the level of digestibility was unequal in the experiments. In one experiment a decrease (1% unit) and in two experiments an increase (1-3% units) of the digestibility after the feeding of growth level in contrast to maintenance level could be observed. The change of rations with a varying protein content did not result in an influence on the digestibility level in comparison with the constant feeding of one ration.     

Comparison of methods for determining the prececal nutrient digestibility and amino acid absorption of swine with ileorectal anastomoses and ileocecal bridge cannulas]

The apparent precaecal nutrient digestibility and amino acid (a.a.) absorption of 10 diets were estimated in pigs with end-to-side ileorectal anastomoses (IRA) as well as with ileocaecal re-entrant cannulae (IZB). The digestibilities of organic matter and crude carbohydrates were significantly higher in IRA pigs than in IZB pigs in two resp. three diets only. There were no practical important differences for the digestibilities of crude protein and crude fat in all diets. Out of the 180 a.a. absorption comparisons only 20 (i.e. 11%) showed differences larger than 5%-units. The absorption rates of several a.a. were lower in IRA than in IZB pigs and of some other a.a. on the contrary. The methionine absorption of five legume diets and one barley + lysine diet were up to 15% resp. 4%-units lower in IRA pigs. Possibly this was due to the activity of microbes in the rectum in connection with a small intake level of protein bound methionine. In order to minimize such a falsification it is proposed to use the end-to-end anastomosis. The deviations in the apparent a.a. absorption between IRA and IZB pigs can be explained partly by differences in the quantity of precaecally excreted endogenous a.a. per 100 g DM intake.     

The energetic utilization of rations with steamed potatoes in growing swine]

The energetic utilization of rations with steamed potatoes (40 and 50% of DM of ration) was measured in 8 growing pigs, live weight 30-70 kg by means of respiration experimental techniques. The experiments were carried out using the difference method (3 periods feeding basal diet and 3 periods feeding basal diet plus potatoes). The digestibility of energy of the steamed potatoes amounted to 94%, that of organic substances 96% and that of crude protein 77%. The metabolizable energy amounted to 16.1 and the energy deposition to 12.0 MJ/kg DM of steamed potatoes, 74.5% utilization respectively. The results in growing pigs are very similar to the results in adult pigs.     

Digestibility and nitrogen utilization in sheep fed enset (Ensete ventricosum) pseudostem or corm and graded levels of Desmodium intortum hay to wheat straw‐based diets

The aim of this study was to investigate the effects of different levels of Desmodium intortum (Desmodium) hay supplementation in sheep fed fixed amounts of enset pseudostem or corm and a basal diet of wheat straw on intake, digestibility and nitrogen utilization. Eighteen male sheep with a mean (± SD) live weight of 20.5 ± 1.45 kg were assigned to six treatments in a completely randomized design and fed either 108 g dry matter (DM) enset pseudostem or 165 g DM enset corm each with three levels (100, 200 and 300 g) of hay supplementation. For the pseudostem diets, there was no significant difference in total DM intake. Total crude protein (CP) intake and N retention increased with increasing levels of hay in both pseudostem and corm diets. The apparent digestibility of DM, OM, CP, acid detergent fibre and neutral detergent fibre (NDF) and microbial nitrogen supply (MN) at 100 g was lower that other levels of supplementation. For the corm diets, total DM and OM intake and MN supply increased with increasing levels of hay. The digestibility decreased (p < 0.001) with increasing levels of supplementation. The results suggest that at least 300 g (395 g/kg dietary DM) of Desmodium hay is required in pseudostem diets, whereas 200 g (337 g/kg dietary DM) may be sufficient in corm diets for efficient nutrient utilization.     

Apparent precaecal digestibility of nutrients and level of endogenous nitrogen in digesta of the small intestine of growing pigs as affected by various digesta viscosities.

Sixteen male growing pigs of about 24 kg BW were fitted with both a duodenal re-entrant and a post-valve T-shaped cannula inserted in the caecum. The animals were divided into four groups. Each group received one of the following diets: corn starch-soybean protein isolate-based diet without (diet C) and with carboxymethylcellulose (diet CMC) or a rye-wheat-based diet without (diet RW) and with xylanase addition (diet RWX). The diets provided similar levels of apparent precaecal digestible crude protein (CP), lysine, methionine + cystine, threonine and tryptophan. Additionally, [15N]-yeast was given with the diets during the first 10 days of the experiment. For estimation of digesta viscosity, N-flow of dietary and endogenous origin, apparent precaecal digestibilities of dry matter (DM), CP, amino acids and non starch polysaccharides (NSP) (only in pigs fed diets RW and RWX), ileal and duodenal digesta were quantitatively collected on day 16 and 17, respectively. The endogenous N-proportion was measured by the ratio of 15N enrichment in the digesta and urine. The duodenal and ileal digesta supernatant viscosity increased as carboxymethylcellulose was included into the diet. Xylanase addition to the rye-wheat based diet reduced the viscosity in the ileal digesta. There were no differences in precaecal digestibilities of DM, CP and amino acids between diet C and CMC. The precaecal digestibilities of DM and soluble and insoluble NSP increased from 69.5% to 73.9%, from 1.3% to 47.9% and from 17.0% to 35.4%, respectively, as xylanase was added to the rye-wheat-based diet. The apparent precaecal digestibility of most essential amino acids increased by 2 to 5 percent units. The amounts of endogenous N at the duodenal level were estimated to be 158, 233, 313 and 276 mg per 12 h per kg0.75 BW of pigs fed diets C, CMC, RW and RWX, respectively. The corresponding values at the ileal level were 95, 107, 164 and 150 mg per 12 h per kg0.75 BW. For endogenous N amounts, significant differences were observed between diets C and CMC (duodenum) and also between semi-purified and cereal-based diets (duodenum and ileum). Methodological aspects for the estimation of endogenous N using the isotope dilution technique are discussed. Obviously, the digesta viscosity per se does not affect the nutrient absorption and endogenous N flow within the small intestine of pigs. Other properties of complex dietary fibre, digesta passage rate or bacterial activity probably contribute to the observed changes.     

The energetic utilization of rations with dried concentrates, potatoes, sugar beets, apple pectin and cane sugar by growing, intact and ileorectostomized swine. 1. Results in swine with ileorectal anastomoses

Rations with dried feedstuffs and rations with between 30 and 50% raw potatoes in the dry matter as well as steamed potatoes and sugar beets, sucrose and apple pectin were tested in measurings of the total metabolism in growing pigs with ileo-rectal anastomoses. The prececal digestibility of the energy of the rations ranged between 42% (rations with raw potatoes) and 79% (rations with sucrose). The digestibility of the rations with a 50% quota of steamed potatoes was better by 30%--units than that of rations with raw potatoes. In addition to crude nutrient digestibility, data are given on the digestibility of starch, water soluble carbohydrates and pectin. The wide variation in the N retention of 6-25 g/animal.day can only be partly connected with energy retention. Urine energy amounted to between 2.5 and 5% of gross energy. The average utilization of metabolizable energy amounted to 69.4%. A connection is to be seen with the value of energy maintenance requirement of 646 kJ retention energy/kg LW0.62.d.     

The energy metabolism of growing swine in the body weight range of 10-50 kg. 2. Nitrogen and energy metabolism

Investigations were carried out about nitrogen and energy metabolism feeding rations with 17-24 and 44-47% crude protein content on maintenance and growing level to castrated male hybrid pigs of line 150. In growing periods the N deposition amounted to 10 g/animal.d (15 kg live weight), 18 g/animal.d (30 kg LW) and 21 g/animal.d (greater than 40 kg LW) on lower protein feeding level. In experiments with higher protein feeding level the corresponding results were 17, 22 and 22 g N deposition/animal.d. The partial utilization of metabolizable energy for deposition amounted to 70% for the rations with 17-24% protein content and to 59% for the rations with 44-47% protein content, without correlation to the animals development and the alternation in the protein feeding level. The results of regression analysis about maintenance requirement were 814, 775 and 806 kJ metabolizable energy/kg LW0.62.d in trials feeding rations with 17-24% crude protein content as well as 764, 846 and 818 kJ metabolizable energy/kg LW0,62.d in trials feeding rations with 44-47% crude protein content. 1,5-1,8 MJ metabolizable energy were used per MJ protein energy deposition and 1,3-1,4 MJ per MJ fat energy deposition respectively. The energy deposition per kg live weight gain amounted to values between 9 (10 kg LW) and 18 MJ (60 kg LW).     

Joint research on the precise determination of the energy and protein requirements of fattening pigs. 5. The effect of the crude protein concentration in the isocaloric diet on the fattening performance of swine of the Bulgarian Landrace

Live weight development and feed expenditure on 3 levels of crude protein supply and with isocaloric rations were investigated in scientific feeding experiments with 7 castrated male pigs each of the Bulgarian land race in the live weight range between 30 and 100 kg with a subdivision at 60 kg. The crude protein concentrations in the rations for the 3 groups were 17%, 15% and 13% in the first fattening period and 15% 13% and 11% in the second fattening period. In the two fattening periods the digestibility of the feed mixtures used was ascertained in experiments. The daily live weight gain in the three groups over the whole fattening period reached a high level of performance (836 g, 778 g and 757 g). The feed expenditure values were 3.3, 3.7 and 3.7 kg mixed feed (88% dry matter) per kg live weight gain. The highest protein supply resulted in the best weight gain performance and the lowest feed expenditure.     

Energetic utilization of sugar beets, dried shreds, sucrose and apple pectin by growing swine. 1. Study overview and composition and digestibility of feed and rations

Total metabolism experiments with a basic ration were carried out over two measuring periods and with a basic ration plus supplements of raw sugar beets, steamed sugar beets, dried sugar beet pulp, sucrose and apple pectin resp. with 4 pigs per test group and 4 test groups (LW 40-135 kg). Live weight gain was approximately equal after the feeding of raw and steamed sugar beets. It amounted to 650 g/animal and day in the first experimental period and to 715 g in the second. After feeding dried sugar beet pulp as supplement the corresponding weight gain was 525 and 565 g/animal and day. In the course of the ontogenetic development up to a live weight of about 70 kg an increase of digestibility could be observed. Adaptation cannot be excluded. This question will be pursued in the following experiments, so that consequences for energetic feed evaluation have to be postponed. For both raw and steamed sugar beets the digestibility of the organic matter was 88%, of NFE 95% and of water soluble carbohydrates 95%.     

Lysine requirement of fattening sows depending on their performance. 2. Relations between energy consumption and live weight increase

105 growing sows in the live weight range were fed with 7 test rations with graduated energy and amino acid levels. The growth intensity was very much influenced by the daily energy consumption. On the basis of regression analysis the following linear relation between daily weight increase (y in g per kg live weight0,75) and the daily energy consumption (x in energetic feed units for pigs per kg live weight0,75) was calculated: y = -13,79 + 0,7037 x (r = 0,84, sb -0,0295). The interpolation with regard to live weight balance resulted in a maintenance requirement of 19,8 energetic feed units for pigs resp. 70 kcal net energy fat for pigs per kg live weight0,75. The methods of assessment chosen showed an increase of the energy requirement per 100 g additional live weight increase per day of a constant amount, independent of the live weight, of 142 energetic feed units for pigs resp. 497 kcal net energy fat for pigs.     

Joint research on the precise determination of the energy and protein requirements of fattening pigs. 8. The effect of various protein levels on the performance and feed expenditure of fattening pigs

Live weight development and feed expenditure were investigated on 3 levels of protein supply and isocaloric rations in scientific feeding experiments with 10 castrated male pigs each of the genetic origin land race pig X large white fed individually in the live weight range between 30 and 100 kg with a subdivision at 60 kg. In the air-dried matter the crude protein content of the feed mixtures used in the first fattening period was 17.6; 15.7 and 13.7% resp. and in the second fattening period from 60 kg live weight onwards 14.9; 12.8 and 11.4% resp. for the 3 test groups. In both fattening periods the digestibility of the rations and the N-balance were determined at 3 representative animals from each of the 3 groups. The following average live weight gains were achieved in the 3 test groups: 1st fattening period: 662; 592 and 539 g resp.; 2nd X fattening period: 709; 676 and 644 g resp. Feed expenditure over the complete fattening period was 4.2; 4.5 and 5.2 kg air-dried matter per kg live weight gain. The highest protein supply resulted in the best live weight gain performance and the lowest expenditure.     

Vitamin A requirement of growing swine. 1. Effect of vitamin A supply on growth of piglets and fattening swine

For the purpose of ascertaining the vitamin A requirement seven experiments with 303 pigs in the live weight range between 6.5 and 114 kg were made. In three experiments under in practice conditions we checked the standard vitamin A supplement to the mixed feed with 1,732 pigs (live weight range between 8.5 and 110 kg). The supplement to vitamin-A-free rations and to those poor in or free of carotene amounted to between 0 and 8,000 IU/kg feed. Above that, between 0 and 16 mg beta-carotene and 1,000 mg nitrite/kg feed were supplemented. As long as the vitamin A store in the liver during weaning amounted to greater than 50 IU and greater than 100 IU/g at the beginning of fattening, feed intake, live weight growth and feed expenditure were not influenced by the supplement of vitamin and provitamin resp. The supplement of 250 IU resulted in the same weight growth from weaning to the end of fattening as that of 4,000 IU. Nitrite supplement had a negative effect at 250 IU, at 500 IU vitamin A consumption and weight growth tended to be only insignificantly lower. The methaemoglobin content decreasing in the course of the experiment reflects the adaptation of the pigs to the nitrite load. The consumption and growth depression caused by vitamin A deficiency could be observed from the 7th week of the experiment when casein-swelling starch rations were fed, but from the 13th week of the experiment only when cereal-soybean oilmeal rations were fed. The weight of liver, spleen, kidneys, heart and brain was not influenced by vitamin A supply. The same applies to the body composition and retention with the exception of two deficiency piglets, which contained less fat in the empty body than the control animals.     

Effects of dietary protein level on nutrients digestibility and reproductive performance of female mink(Neovison vison)during gestation

The objective of this study was to determine whether nutrient digestibility and reproductive performance of pregnant mink(Neovison vison) were affected by different dietary protein levels. One hundred and twenty female mink were randomly assigned to four groups, receiving diets of fresh material with different protein levels. The dietary protein levels,expressed as percentage of dry matter(DM),were 32,36, 40 and 44% respectively. These values corresponded to average 320, 360, 400 and 440 g protein/kg DM, respectively. Results were as follows. All of crude protein digestibility, nitrogen(N) intake, N retention increased along with dietary protein level increasing. Low protein level(32%) significantly reduced the above indicators(P 0.05). DM digestibility and ether extract digestibility were not affected by dietary protein level. Results of mated females, barren females, kids per litter, live born kids per mated female, birth survival rate, and birth weight showed that mink achieved optimal reproductive performance when dietary protein level was 36%. In conclusion, dietary protein was anticipated to significantly influence some nutrients' utilization. Adopting the appropriate dietary protein level allow better reproduction performance. The most preferable reproductive performance was achieved when diet contained 275.5 g digestible protein per kg DM for female mink in gestation.