Bioavailability of the calcium salt of dl-methionine hydroxy analog compared with dl-methionine for nitrogen retention and the preference of nursery pigs for diets based on the 2 forms of methionine

Experiments were conducted to determine the relative bioavailability (RBV) of the calcium salt of the hydroxy analog of dl-methionine (MHA-Ca, 84%) to dl-methionine (dl-Met, 99%) as Met sources fed to pigs. In experiment 1, 42 crossbred barrows (initial BW of 15.0 ± 0.7 kg) were allotted to 7 treatments in an N-balance study. The basal diet (BD) was formulated to contain 15.4% CP and 0.22% Met (70% of requirement). Diets included (1) BD, (2) BD + 0.025% dl-Met, (3) BD + 0.050% dl-Met, (4) BD + 0.075% dl-Met, (5) BD + 0.038% MHA-Ca, (6) BD + 0.077% MHA-Ca, and (7) BD + 0.115% MHA-Ca. An increase in dietary inclusion rates of both Met sources linearly increased (P < 0.01) N retained (g/d) and N retention (% of intake). Using linear slope-ratio regression, the RBV value of MHA-Ca to dl-Met for N retained (g/d) was 63.0% on a product-to-product basis (75.0% on an equimolar basis). In experiment 2, 40 crossbred barrows (initial BW of 15.5 ± 1.5 kg) were allotted to 5 treatments in another N-balance study. The BD was formulated to contain 17.0% CP and 0.22% Met (70% of requirement). Diets included (1) BD, (2) BD + 0.030% dl-Met, (3) BD + 0.060% dl-Met, (4) BD + 0.046% MHA-Ca, and (5) BD + 0.092% MHA-Ca. Increasing levels of dl-Met or MHA-Ca increased N retained (g/d) and N retention (% of intake) linearly (P < 0.001) and quadratically (P < 0.05). Using linear slope-ratio regression, a product-to-product RBV value of MHA-Ca to dl-Met was 68.4% (81.4% on an equimolar basis) for N retained (g/d). In experiment 3, 276 pigs (12 barrow and 11 gilt replicates; initial BW of 7.09 ± 1.1 kg) were used in 3 diet preference studies. Pigs were randomly allotted to 1 of 3 treatment comparisons of feed choice: (1) BD (0.23% Met) or BD + 0.07% dl-Met; (2) BD or BD + 0.0825% MHA-Ca, and (3) BD + 0.07% dl-Met or BD + 0.0825% MHA-Ca. Pigs consumed a higher percentage (55 vs. 45%; P = 0.008) of their total feed intake from the diet supplemented with 0.07% dl-Met in Comparison 1, but a lower percentage (45 vs. 55%; P = 0.003) of their total feed intake from the diet supplemented with 0.0825% MHA-Ca in Comparison 2. There was no diet preference for dl-Met or MHA-Ca in Comparison 3. The observed Met source preference differences occurred in the barrow replicates but not in the gilt replicates. These results demonstrated the mean RBV of MHA-Ca to dl-Met of 65.7% on a product-to-product (wt/wt) basis or 78.2% on an equimolar basis and that a preference for Met sources was observed in barrows but not in gilts.     

Poultry offal ensiled with lactobacillus acidophilus for growing and finishing swine diets

Poultry offal (heads, feet, viscera) from a broiler processing plant was ground and mixed with corn, dried molasses and a Lactobacillus acidophilus culture. Fermentation was shown to be effective in batch sizes of 3.8, 75.7 and 208.1 liters, as well as a 1,360-kg silo. It was generally complete at 72 h. In trial 1, rats were fed silage mixtures of 60:30:5:5, 45:45:5:5 and 30:60:5:5, offal, corn, molasses and inoculant, respectively. Rats did not gain as well when fed the silage diets (P less than .05) as when fed the basal diet; however, the ranking of silages was 45:45, 60:30 and 30:60, offal-to-corn ratio for rat daily gains and feed conversions. In trial 2, growing-finishing pigs were fed the 60:30:5:5 silage at rates of 0, 10, 20 and 30% of the diet. Average daily gains and feed-to-gain ratios were not affected by including offal silage at up to 20% of the diet, but 30% offal silage in diets resulted in depressed gains (P less than .05) and increased feed-to-gain ratios. Carcasses were not different among treatments for dressing percentage, length, average backfat and percentage of ham, loin, shoulder, lean cuts and primal cuts. Carcasses from pigs fed 20 and 30% offal silage had significantly darker and firmer loin-eyes than those from control fed pigs. Marbling was higher (P less than .05) in loin-eyes from pigs fed 30% offal silage as compared with those from pigs fed 0% offal silage.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of copper addition to diets with various iron levels on the performance and hematology of weanling swine

A 2 x 6 factorial experiment with Cu added at 5 or 250 ppm and Fe added at 50, 100, 150, 200, 250, or 300 ppm was conducted using 480 crossbred weanling pigs with an average initial weight of 7.0 kg. The basal corn-soybean meal-whey diet contained 4 ppm Cu, 169 ppm Fe, and 199 ppm Zn. Pigs were allotted by weight, sex, and litter outcome group and had ad libitum access to feed and water during the 28-d trials. Animals were weighed and pen feed intake was recorded weekly. Blood samples were collected on d 1, 14, and 28 of the experiment. The addition of 250 ppm Cu increased ADG (P less than .001) and average daily feed intake (ADFI, P less than .01) during the 28-d trials. The addition of Fe had no effect on ADG and ADFI (P greater than .10). A Cu x Fe interaction (P less than .01) was observed for feed/gain. Increasing Fe levels linearly improved hematocrit status (P less than .05) on d 28 of the trial. A Cu x Fe interaction (P less than .08) was observed for hemoglobin at the end of the trial; hemoglobin levels were increased by the addition of Fe to the diet containing 250 ppm of Cu. Plasma Cu was increased (P less than .001) by the addition of 250 ppm of Cu. Plasma Fe was low when either 50 or 100 ppm of Fe was added in the presence of 250 ppm of Cu, but it was not affected at other levels, resulting in a Cu x Fe interaction (P less than .05). These data indicate that levels of added Fe up to 300 ppm may help to improve the hematological status of weanling pigs fed growth-promoting levels of Cu but that it has little effect on performance.     

Digestibility and digestive organ development in indigenous and improved chickens and ducks fed diets with increasing inclusion levels of cassava leaf meal

Growing indigenous Cambodian chickens and ducks, and broiler chickens and White Pekin ducks were fed diets containing 0%, 7%, 14% and 20% of cassava leaf meal (CLM) to study the effects of CLM level on diet digestibility and gastrointestinal tract (GIT) and organ development. The coefficient of total tract apparent digestibility (CTTAD) of dry matter (DM) and intake of digestible DM decreased with increased dietary CLM. DM and digestible DM intake was higher for local breeds than for the corresponding exotic breeds, and higher for ducks than for chickens (p < 0.001), although there were no species or breed effects on CTTAD of DM (p > 0.05). Weight of small intestine, caeca, gizzard and pancreas, expressed as per kg body weight, increased with increased CLM in the diet (p < 0.001). There was no consistent diet effect on liver weight. Length of small intestine and caeca, expressed on a mass-specific basis, increased with dietary CLM content (p < 0.001). When expressed as per kg body weight small intestine, proventriculus, gizzard, pancreas and liver weights, and small intestine length, were higher in ducks than in chickens (p < 0.001), and were higher in the indigenous than in the improved breeds (p < 0.01), except for small intestine weights, which were similar. However chickens had higher weight of caeca (p < 0.001) and colon (p < 0.01) in absolute units and per kg body weight.     

低蛋白质日粮对肥育猪生长性能的影响

试验选择初始体重为60kg左右的杜×大×长三元健康中猪76头,随机分为对照组和试验组。对照组日粮按照NRC(1998)营养需要量推荐配制,试验组在NRC推荐的日粮粗蛋白质水平上降低4个百分点。试验结果表明,试验组日增重较高,比对照组增加了20.95g,增幅为2.96%;试验组料肉比较对照组低了7.62%;增重成本节约了0.85元/kg;试验组瘦肉率与对照组相比没有显著差异。从各指标的趋势上看,试验组的生长表现和经济效益均优于对照组。     

低蛋白氨基酸平衡日粮对断奶仔猪生产性能的影响

试验选取38头35日龄±1日龄断奶、体重在5.9kg左右的杂交仔猪为试验动物。随机分为 3组，研究 3种不同蛋白质水平（17％、18％和20％）的玉米—膨化大豆型基础日粮对断奶仔猪生产性能的影响，试验期为28d。试验结果表明：①蛋白含量为 18％的试验组仔猪的腹泻率为最低（ 9.18％），与17％的试验组的差异不显著（ P>0.05），与20％的试验组差异极显著（ P<0.01）；②蛋白质含量为18％的试验组仔猪的料肉比为1.79，而蛋白为17％和20％的试验组则分别为1.97、1.94。说明低蛋白氨基酸平衡日粮对仔猪生产性能无影响，但可明显影响减少仔猪的腹泻率。     

日粮中添加脂肪酸钙对奶牛生产性能的影响

选取24头处于泌乳前期的中国荷斯坦奶牛,采用配对设计分成4组,研究奶牛日粮中分别添加200g棕榈油脂肪酸钙、大豆油脂肪酸钙和葵花籽油脂肪酸钙对奶牛采食量、产奶量及乳品质的影响。结果表明:日粮中添加3种脂肪酸钙均不影响奶牛采食量(P>0.05);添加棕榈油脂肪酸钙后产奶量提高10.45%、乳脂率提高7.42%、乳蛋白率降低4.67%、乳干物质提高1.41%(P>0.05);添加大豆油脂肪酸钙后产奶量提高4.25%、乳脂率提高8.54%、乳蛋白率降低4.64%、乳干物质提高2.67%(P>0.05);添加葵花籽油脂肪酸钙后产奶量提高4.76%、乳脂率提高3.52%、乳蛋白率降低3.35%、乳干物质提高1.42%(P>0.05)。     

Effect of enzyme addition to wheat-, barley- and rye-based diets on nutrient digestibility and performance of laying hens

1. Laying hen performance, egg quality, intestinal viscosity and nutrient apparent digestibility were evaluated with respect to the main cereal used in the diet and dosage rate of a fungal beta-glucanase/xylanase enzyme complex. 2. Twelve diets were arranged factorially, with three soluble fibre cereals (SFC); 500 g/kg of wheat or barley or 350 g/kg of rye, and 4 enzyme concentrations (0, 250, 1250 and 2500 mg/kg). An additional control diet based on maize was also included. 3. The use of SFC in the diet instead of maize did not affect egg production or food efficiency, but hens fed on SFC diets exhibited a higher incidence of dirty eggs than hens fed on the maize diet (8-6 vs 4.6%; P<0.01). 4. Laying hens fed on enzyme-supplemented diets produced more eggs (2.1%; P<0.05) and had better food efficiency per dozen eggs (2.5%; P<005) than hens fed on non-supplemented diets. An excess of enzymes in the diet (10 times the recommended dose) did not produce any deleterious effect on laying hen productivity. 5. Enzyme supplementation (ES) reduced intestinal viscosity (P<0.001) and the incidence of dirty eggs (P<0.01). The reduction in viscosity was more pronounced in barley than in wheat or rye diets (P<0.05). 6. Apparent nutrient digestibility in SFC diets was higher with ES, including dry matter (3.1%; P=0.08), fat (4.4%; P<0.001), non-starch polysaccharides (83.3%; P<0.01) and AMEn (2.5%, P<0.01). 7. It is concluded that substitution of maize by SFC is facilitated by ES, especially with respect to egg production, food conversion efficiency and egg shell cleanliness. An excess of enzymes did not produce any deleterious effect on nutrient digestibility or performance of laying hens.     

The effect of copper and fat addition to the diets of weanling swine on growth performance and serum fatty acids.

A 2 x 3 factorial experiment, encompassing three 28-d trials involving a total of 420 weanling pigs, was conducted to determine the effect of dietary Cu (5 or 250 ppm) and animal fat (0, 2.5, or 5%) on the performance and serum fatty acid profiles of weanling pigs. Pigs had ad libitum access to corn-soybean meal-based diets containing 10% whey and 5% fish meal and similar lysine:calorie ratios. Pigs were weighed and pen feed intakes were recorded weekly. Weekly blood samples were collected during the first two trials (n = 270) for serum fatty acid analysis. There was a Cu x fat interaction for ADG from d 1 to 14 (P less than .07) and over the 28-d experiment (P less than .05). The ADG of pigs fed 250 ppm of Cu increased, whereas the ADG of pigs fed 5 ppm of Cu was not affected as dietary fat increased. The addition of 250 ppm of CU increased (P less than .01) ADFI throughout the 28-d experiment. The addition of fat quadratically increased ADG (P less than .05) during d 14 to 28 and gain:feed ratios (P less than .01) during d 14 to 28 and over the 28-d experiment. The addition of fat decreased (P less than .05) the weight percentage of serum saturated fatty acids and increased (P less than .01) the weight percentage of serum monounsaturated fatty acids on d 28. The addition of 250 ppm of Cu decreased (P less than .01) the weight percentage of monounsaturated fatty acids on d 14 and 28.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bioavailability of the dl-methionine and the calcium salt of dl-methionine hydroxy analog compared with l-methionine for nitrogen retention in starter pigs

Two nitrogen balance studies were conducted to evaluate the relative bioavailability values (RBV) of dl-methionine (dl-Met) and dl-methionine hydroxy analog calcium salt (MHA-Ca) to l-methionine (l-Met) as Met sources fed to pigs. In experiment 1, 42 pigs were assigned to 7 treatments feeding with basal diet (BD) formulated to be deficient in Met (0.22% standardized ileal digestible basis) but adequate in other amino acids. Diets included (1) BD, (2) BD + 0.025% dl-Met, (3) BD + 0.050% dl-Met, (4) BD + 0.075% dl-Met, (5) BD + 0.025% l-Met, (6) BD + 0.050% l-Met, and (7) BD + 0.075% l-Met. Increasing levels of l-Met and dl-Met enhanced N retained (g/d) and N retention (% of intake) linearly (P < 0.01). Using a linear slope ratio procedure, a product-to-product RBV of dl-Met compared with l-Met was 94% (95% confidence limits: 65% to 123%) based on N retained expressed as g/d and 99% (95% confidence limits: 70% to 128%) for N retention expressed as % of intake. In experiment 2, 42 pigs were allotted to 7 treatments in another N-balance trial. Diets included (1) BD, (2) BD + 0.025% l-Met, (3) BD + 0.050% l-Met, (4) BD + 0.075% l-Met, (5) BD + 0.030% MHA-Ca, (6) BD + 0.060% MHA-Ca, and (7) BD + 0.089% MHA-Ca. An increase in dietary inclusion rates of l-Met increased (P < 0.01) N retained (g/d) linearly while increasing levels of MHA-Ca had no effects (P > 0.05) on N retained (g/d) and N retention (% of intake). Using linear slope-ratio regression, the RBV of MHA-Ca compared with l-Met was 70% (95% confidence limits: 59% to 81%) on a product-to-product basis or 83% on equimolar basis based on N retained expressed as g/d. Overall, the mean RBV of dl-Met to l-Met of 97% (95% confidence limits cover 100%) indicated that dl-Met and l-Met are equally bioavailable as Met sources in pigs. Compared with l-Met, the RBV of MHA-Ca was lower at 70% (95% confidence limits: 59% to 81%) on a product-to-product basis or 83% on equimolar basis in starter pigs.     

Comparison of rolled, NaOH treated and ensiled wheat grain in dairy cattle diets

The effect of three wheat grain treatments on the zootechnical performance (feed intake, milk production and milk fat and protein production) of dairy cattle was studied with 18 Holstein cows in each of two feeding trials (both a 3 × 3 Latin square design). Rolled wheat, NaOH treated wheat and immature wheat ensiled with Graintona-Plus (Vee-lik, Zuienkerke, Belgium) were compared in a ration with fixed DM proportions of wheat, maize silage and prewilted grass silage. The nutritive value of the three wheat treatments was derived from in situ rumen degradability studies and from in vivo digestibility experiments.

In situ rumen incubations showed that NaOH treatment strongly decreased protein and starch degradability of the wheat. Due to that importantly decreased starch degradability NaOH treated wheat may be a source of starch with a reduced risk of rumen acidosis as compared to rolled wheat. On the other hand, due to the ensiling, immature wheat had a very high washable starch fraction, despite the Graintona-Plus treatment. The protein value differed importantly, with the DPI (true protein digested in the small intestine; [Tamminga, S., van Straalen, W.M., Subnel, A.P.J., Meijer, R.G.M., Steg, A., Wever, C.J.G., Blok, M.C., 1994. The Dutch protein evaluation system: the DVE/OEB-system. Livest. Prod. Sci. 40, 139–155]) value being 103, 125 and 76 g/kg DM for rolled, NaOH treated and ensiled wheat, respectively. The RDPB (degraded protein balance; [Tamminga, S., van Straalen, W.M., Subnel, A.P.J., Meijer, R.G.M., Steg, A., Wever, C.J.G., Blok, M.C., 1994. The Dutch protein evaluation system: the DVE/OEB-system. Livest. Prod. Sci. 40, 139–155]) value of the NaOH treated wheat was − 51 vs. − 37 and− 33 g/kg DM for rolled and ensiled wheat. In vivo digestibility trials with Holstein cows indicated that the net energy value of the wheat treatments was not significantly different.

In Trial 1, all diets were formulated to supply 105% of the requirements of DPI and net energy lactation (NEL; [Van Es, A.J.H., 1978. Feed evaluation for ruminants: I. The system in use from May 1977 onwards in the Netherlands. Livest. Prod. Sci. 5, 331–345]) and a safe RDPB level (± 200 g/day). On average 4.6 kg wheat DM was fed daily. Following trial 1, trial 2 was carried out, with the maize silage, grass silage and wheat fed in the same proportions as in trial 1, but fed ad libitum, to compare the intake level of the three diets. In both trials, the NaOH treated wheat resulted in the best performance with importantly increased milk yield and the highest yield of fat and protein corrected milk. Ensiled immature wheat resulted in a significant lower milk production and milk protein yield and in a higher milk fat content. In trial 1, DM-intake of the three groups was comparable due to the experimental design. In trial 2 intake of the cows fed NaOH treated wheat was significantly higher (23.5 vs. 21.1 kg/day for the other two groups).     

Effects of dietary fat type and non-starch-polysaccharide-hydrolysing enzyme addition to rye-based diets on muscle protein turnover in broilers

1. Muscle protein turnover was measured in broilers fed on rye-based diets containing either beef tallow (T) or soybean oil (S) at an inclusion rate of 100 g/kg. Each of these diet types was tested either in the absence (S[-], T[-]) or presence (S[+], T[+]) of a xylanase-containing enzyme preparation. Protein turnover was measured in gastrocnemius muscle (GM) and pectoralis major muscle (PM). 2. Fractional rate of protein synthesis (FSR) was measured by the large dose technique using [15N]-labelled phenylalanine whereas fractional protein growth rate (FGR) was estimated by regressing tissue protein content over time. Fractional breakdown rates (FBR) were calculated by the difference between FSR and FGR. 3. In PM, FSR (%/d) was 22.1, 23.4, 21.5 and 24.4 in groups S[-], S[+], T[-] and T[+], respectively, and FBR (%/d) was 8.3, 9.8, 4.5 and 10.8 with the xylanase effect being significant. The FGR of 17.0%/d calculated for the broilers fed on the T[-] diet tended to be higher than for the other groups (13.6 to 13.8%/d). No significant effects were detected for these parameters in the GM. 4. The absolute amounts of protein which were synthesised daily and accreted in both muscles were significantly higher with xylanase supplementation in both fat type diets but at a significantly higher level when soybean oil was the dietary fat type. 5. The observed effects on protein turnover have to be seen in the context of an overall adverse effect of dietary soluble pentosans from rye in combination with tallow on physico-chemical chyme conditions, digestion and absorption of energy and nutrients and tissue-specific metabolic changes.     

Relation of feedlot performance and certain physiological responses to the metabolizable protein and urea content of cattle diets

An experiment was conducted to test the accuracy of the metabolizable protein system in predicting the amount of urea that would be useful in a corn-based cattle diet. Treatment diets included a basal, low-protein (7.8% CP) negative control (NC) with no supplemental N and a positive control (PC) that contained soybean meal. Urea was added to the NC diet in quantities calculated to be either 25% deficient (LU), equal to (MU) or 25% in excess (HU) of the urea fermentation potential ( UFP ). In vitro rumen fermentation studies were used to determine sequential ammonia production and digestible dry matter content of the diets. In a growth trial, 12 individually-fed Angus, Hereford and Angus X Hereford steers weighing an average of 213 kg were assigned randomly to each treatment diet. At the conclusion of the 112-d trial, rumen ammonia and jugular blood urea N (BUN) concentrations were determined on two steers from each treatment before feeding and at 1, 2, 3, 4 and 5 h postfeeding. In vitro ammonia concentrations of the NC and PC treatments were lower (P less than .05) than that of urea containing diets. In vivo rumen ammonia concentrations at 1 h postfeeding and BUN levels at 3 h postfeeding were low for both the NC and PC diets compared with urea-containing diets. Both of these values increased with each successive increase of added urea to the NC diet. During the initial 70 d of the growth trial, daily gains were improved (P less than .05) by addition of urea up to the MU level, which fulfilled the calculated UFP .(ABSTRACT TRUNCATED AT 250 WORDS)     

The performance of male ducklings given starter diets with different concentrations of energy and protein

1. Male ducklings were fed for 14, 21 or 28 d on diets containing 180, 200, 220 or 240 g of protein and 10.88 or 12.55 MJ of metabolisable energy (ME) per kg, followed by a common finisher diet until 56 d of age.

2. Birds given starter diets with 220 or 240 g of protein per kg were significantly heavier at 14 d than those given diets with 180 or 200 g protein per kg.

3. There was no significant benefit in feeding diets with protein levels greater than 180 g/kg for more than 14 d.

4. Diets with only 10.88 MJ of ME per kg produced significantly lighter birds at 28 and 56 d of age and significantly reduced food conversion efficiency up to 14 d.     

Possibility of fat addition in the rabbit diets

Baladi rabbits were fed on five-similar-experimental diets, except the replacement for starch in the 1st diet, cattle tallow in the 2nd, cotton seed oil in the 3rd, and hydrogenated palm oil in the 4th instead of 2% more wheat bran in the 5th (control) diet. All other husbandry conditions were the same for all groups of animals during the experimental period of 7 weeks. The cattle tallow in the second diet caused significant increase of feed intake, growth rate, relative weights of kidneys, lungs and heart and calcium of the tibia bone. This diet had tendency to diminish significantly blood contents of total nitrogen and cholesterol as well as vitamin A in the liver and tibia contents of silica, phosphorus and magnesium. Diet number 3 included cottonseed oil lowered blood contents of glucose, phosphorus, cholesterol and enzyme activity of glutamate oxaloacetate transaminase in the serum and specific gravity of tibia bone. On the other hand, it elevated significantly (P less than or equal to 0.01) stored vitamin A in the liver than on all other experimental diets. Feeding rabbits on diet including hydrogenated palm oil subsided liver contents of dry matter, ash and vitamin A and raised ether extract of the liver significantly. It reduced also dry matter content of the femoral muscle. Substitution for starch (instead of 2% of the diet fats or bran) increased blood content of haemoglobin and haematocrit (insignificant) but values of glucose and phosphorus as well as liver content of dry matter, content of femoral muscle of dry matter and ether extract and content of tibia bone of silica and phosphorus were significantly higher than the other experimental diets. It decreased relative weights of different organs (significantly) and liver contents of ether extract and vitamin A (insignificantly) than on control diet. It could be said that the addition of cattle tallow and cottonseed oil would be recommended to be included in rabbit diets after more studies to determine the effects of the different animal-vegetable mixtures of fats, the best ratio between the two sources of fats, the interrelationships between that mixtures and the energy of the diet, the dietary protein level, the rabbit breed and their weights and aim of the production under the seasonal variation of the weather.     

Effects of diets with different protein and DL-methionine levels on the growth performance and N-balance of growing minks

This study was performed to evaluate the effects of diets with different protein and dl-methionine (Met) levels on nitrogen (N) retention, nutrient digestibility, growth performance, and some blood parameters in growing minks. Eighty healthy male minks were selected and randomly divided into five groups with different types of diet. The dietary protein levels, expressed as percentage of dry matter (DM), were 36% (HP) and 28% (LP), corresponding to average 363g and 295g protein/kg DM, respectively. LP was supplemented with Met (0.3%, 0.6% and 0.9% DM); the codes were LP+M1, LP+M2 and LP+M3, respectively. From July to middle of September, the average daily gain and feed: gain ratio (F/G) of the minks that received the diet with 0.6% Met added to the low protein diet was better than feeding HP and other groups. Fecal N and Urinary N of group LP+M2 were the lowest one, in contrast, the daily retention of N was the highest one. Digestibility of DM and CP were not affected by different diets, but digestibility of fat declined with dietary protein level decreasing. Serum urea nitrogen (SUN) was affected by different protein and Met levels. Considering all factors the best performance could be observed offering LP+M2, the prime level of Met was 13.87 g/kg DM in dietary, and 258.5 g digestible protein kg(-1) DM was enough for mink in growing period. Furthermore, addition of Met in low protein diets for minks would be beneficial in terms of reduced feed expenses and lower nitrogen emissions to the environment.     

Effect of protein source and protease addition on performance,blood metabolites and nutrient digestibility of turkeys fed on low-protein diets from 28 to 55 d post hatch

1. The objective of this study was to investigate the effect of a monocomponent protease and dietary inclusion of canola meal (CM) and poultry by-product meal (PBM) on growth performance, carcass characteristics and blood metabolites of turkeys fed on low crude protein (CP) diets from 28 to 55 d post hatch.

2. Experimental treatments included control, maize–soybean meal diet including 258.3 g/kg CP; negative control 1 (NC1), maize–soybean meal diet with reduced CP (232.4 g/kg); NC2, control diet (CP, 258.3 g/kg) including CM (80 g/kg) and PBM (80 g/kg); NC3, maize–soybean meal diet with reduced CP (232.4 g/kg) including CM (80 g/kg) and PBM (80 g/kg). Also, the NC1 + P and NC3 + P diets were created by addition of protease enzyme (30 000 units/kg of diet) to the NC1 and NC3 diets, respectively.

3. The NC3 group had lower body weight gain (BWG) compared to those fed on the control diet, and no improvement with enzyme addition (NC3 + P) was achieved. The protease addition to the NC1 diet (NC1 + P) improved BWG to the level of the control diet. The NC1 group had higher feed conversion ratio (FCR) compared to the control and NC3 + P, but protease addition to the NC1 diet improved FCR.

4. Protease addition to the low CP diets resulted in higher nitrogen (N) retention than in the control and NC2 groups. Also, the NC1 + P and NC3 + P diets increased apparent ileal digestibility (AID) of CP compared to the control group.

5. It was concluded that addition of CM (up to 80 g/kg) and PBM (up to 80 g/kg) to turkey diets had no negative effect on growth performance from 28 to 55 d of age. The NC1 + P group achieved the BWG of the control group which was partially due to increases in N retention and AID of CP, but the NC3 + P group failed to recover the growth losses. This difference implies that the efficacy of the protease may depend upon the protein source in the ration.