饲粮中添加抗菌肽对肉鸭增重及血清尿素氮、总蛋白水平的影响

240只1日龄肉鸭随机成分4组,每组设3个重复,对照组用基础日粮,试验组在基础日粮上每千克分别添加1、2、3mL抗菌肽制剂。结果显示:1)2、3mL/kg添加量组增重效果显著(P<0.05),3mL/kg添加量组最佳;净肉率升高,达到显著水平(P<0.05),其中主要是胸肌率上升;腹脂率降低但差异不显著(P>0.05);料重比无显著变化(P>0.05)。2)血清总蛋白浓度差异不显著(P>0.05),但尿素氮浓度下降,2、3mL/kg添加量组达显著水平(P<0.05),3mL/kg添加量组最低。     

Effect of protein and lysine levels in the diet on body gain composition and energy utilization in growing pigs

Eight replicates of four Large White littermate female pigs were used to evaluate the effect of protein and lysine levels in the diet on the efficiency of protein and energy utilization. In each replicate, one pig was slaughtered at about 20 kg live weight and the others received three diets that contained (per Mcal digestible energy) 37.5 and 2.00 g (diet pl), 37.5 and 2.35 g (diet pL) or 45.0 and 2.35 g (diet PL) of digestible protein and lysine, respectively. Pigs were slaughtered after a 7-wk period. Tissue and chemical composition of the gain and energy and nitrogen gain were determined by using the comparative slaughter technique. Metabolizable energy (ME) intakes were similar in the treatments. Pigs fed the pl diet had a smaller body weight and muscle gain and retained less nitrogen and more lipids than pigs fed pL and PL diets. The decrease in the level of nonessential nitrogen in the diet (pL vs PL) did not affect body weight and muscle gain and the amount of nitrogen retained in muscle tissues. However, pigs given the PL diet had a higher total nitrogen retention and a lower fat deposition and exhibited a higher heat production. For each gram of additional protein catabolized for energy purposes (PL vs pL), heat production was increased by 1.8 kcal. The amount of lysine per unit of muscle gain (38 g/kg) or protein deposited (120 g/kg) was independent of protein and lysine levels in the diet. Estimates of energy (indirect calorimetry) and nitrogen (balance technique) retention were also obtained on the same animals; results were comparable with data obtained by direct measurements.     

Effects of protein deprivation on subsequent growth performance,gain of body components,and protein requirements in growing pigs

Forty-eight barrows were used in a 2 x 6 factorial arrangement to test a hypothesis that feeding a protein-deficient diet affects subsequent growth response by altering the efficiency of protein utilization. Barrows were individually fed either a 9% crude protein (CP) diet or an 18% CP diet from 20 to 30 kg of body weight (BW) (depletion phase). From 30 to 45 kg BW (realimentation phase), pigs were fed one of six experimental diets with CP levels of 11.8, 13.1, 14.3, 15.6, 18.8, and 21.8%. Four pigs were slaughtered at 20 kg BW to determine initial body composition. Four pigs from each treatment in depletion phase (a total of eight) were slaughtered at 30 kg BW, and all pigs from each treatment in realimentation phase (a total of 36) were slaughtered at 45 kg BW for subsequent compositional analysis. Pigs were bled at 20, 30, and 40 kg BW for blood urea nitrogen (BUN), insulin-like growth factor (IGF)-I, and IGF-binding protein (IGFBP) assays. Pigs were given three times the maintenance digestible energy requirement (3 x 120 kcal BW(-0.75) x d(-1)) in three equal meals daily. The feed allowance was adjusted every 3 d. During the depletion phase, pigs fed the 18% CP diet grew faster and more efficiently (P < 0.01) and gained more (P < 0.01) water and protein than did pigs fed the 9% CP diet. Pigs fed the 18% CP diet showed higher (P < 0.01) BUN values, IGF-I concentrations, and IGFBP ratios than pigs fed the 9% CP diet. During the realimentation phase, pigs fed the 9% CP diet during the depletion phase grew faster (P < 0.05), tended to grow more efficiently (P = 0.066), gained more water (P < 0.01), and tended to gain more protein (P = 0.068) than pigs fed the 18% CP diet during the depletion phase. Pigs fed the 9% CP diet during the depletion phase tended (P = 0.069) to have a higher protein requirement during the realimentation phase than pigs fed the 18% CP diet during the depletion phase. When measured at 40 kg BW, pigs fed the 9% CP diet had a lower (P < 0.05) BUN than pigs fed the 18% CP diet during the depletion phase. However, the plasma IGF-I concentration and IGFBP ratio at 40 kg BW were not affected by dietary CP level fed during the depletion phase. This study indicates that pigs fed a protein-deficient diet exhibit compensatory growth. During the period of compensatory growth, the requirement of CP for those pigs is higher than that of pigs previously fed an adequate diet. This study also suggests BUN can be used as an indicator of protein utilization efficiency and compensatory growth.     

The influence of empty body weight and mature weight of the genotype on energy density of empty body gain in growing lambs

From data reported by authors who had serially determined the chemical composition of the empty body of growing lambs of a wide range of genotypes, the energy density of empty body gains (E/G) at intervals from 20 to 50 kg empty body weight (EBW) were estimated. Energy density of empty body gain was related to the EBW of these lambs and to an approximation of the mature weight for the genotype (MW) obtained from a separate data set. The addition of MW to the function relating E/G to EBW increased the r2 from .793 to .940 and reduced the residual standard deviation from .550 to .300 Mcal/kg. Combining EBW and MW as predictors of E/G provided the following function: E/G = 5.718 + .093 (EBW) - .036 (MW). Energy density of empty body gain was approximately constant across all genotypes when comparisons were made at a constant EBW/MW. Thus, both EBW and mature weight of the genotype are closely related to E/G and should be considered important for accurately predicting net energy of gain requirements for growing lambs.     

Influence of sarsaponin on growth, feed and nitrogen utilization in growing male rats fed diets with added urea or protein

Two experiments were conducted with growing male rats to determine the effects of 120 ppm of dietary sarsaponin (S) on nitrogen (N) metabolism when urea or protein are added to the diet. Growth, feed efficiency, N digestibility and balance, urinary N and ammonia-N (NH3-N), and cecal urease and NH3-N were measured. Growth and feed utilization were unaffected by dietary S. Adding urea or protein to the diet increased apparent N digestibility and increased urinary-N excretion. Urea did not affect N balance, whereas growth, feed utilization and N balance were maximized with 22% compared with either 16 or 28% dietary protein. Urinary NH3-N excretion was decreased by S when urea was added to the diet but was not affected when fed with increasing dietary protein. Cecal urease was decreased by S when urea was added or when the protein level was increased in the diet; effects on cecal NH3-N varied between the two experiments. Plasma urea-N was decreased by S. It is concluded that S has minor effects on N metabolism in rats and that NH3-N formation or excretion is only marginally affected by dietary S. If S decreases NH3-N level in confinement facilities, it is concluded that the effect is after the waste material is excreted by the animal, perhaps through reduced urease activity.     

The effects of dietary crude protein level on rate, efficiency and composition of gain of growing beef bulls

Two experiments were conducted to evaluate the effects of dietary CP level on rate, efficiency and composition of gain of growing beef bulls. In Exp. 1, 59 bulls (333 +/- 15.8 kg) were used. Eleven bulls were slaughtered on d 0 to provide an estimate of initial carcass composition (9-10-11 rib section chemical analyses), and remaining bulls were assigned to treatment diets containing 10, 12 or 14% dietary CP. Bulls fed the 10% CP diet grew slower (P less than .05) than bulls fed the 12 or 14% CP diets, although dry matter intake and feed-to-gain ratio did not differ. Bulls fed the 12% CP diet had fatter carcasses (P less than .05) than bulls fed the 10 or 14% CP diets and had greater daily fat accretion than bulls fed the 10% CP diet. In Exp. 2, 60 bulls (318 +/- 9.0 kg) were used. Bulls were assigned to initial slaughter (n = 6) or to one of three dietary treatments, 10, 12 or 14% CP, and were slaughtered after feeding for 66, 136 or 202 d (n = 6 . treatment -1 . slaughter time -1). Bulls fed 10% CP diets had lower (P less than .05) rates of carcass protein accretion during d 0 to 136 and d 0 to 202. Carcass fat gain was similar among treatments over the entire experiment, although bulls fed the 14% CP diet gained more fat during d 0 to 136 than bulls fed the other treatments.(ABSTRACT TRUNCATED AT 250 WORDS)     

The influence of photoperiod on body weight gain, body composition, nutrient intake and hormone secretion

Increasing daily light exposure from 8 to 16 h increases average daily body weight gains of sheep and Holstein cattle but reduces gains of white-tailed doe fawns. Some of these effects on average daily gain in sheep are the result of increased gut fill and pelt weight. Increasing daily exposure to light increases feed intake when sheep or cattle are fed ad libitum. However, increased feed intake is not a prerequisite for the anabolic effects of long duration exposures to light because increased growth occurs in the animals given 16 h light:8 h dark (16L:8D) even when feed intake is restricted. The anabolic effects of increased duration photoperiods in sheep are independent of the gonads, whereas in cattle they are dependent on the gonads. Consistent increases in average daily gains of cattle in response to longer duration photoperiods have not always been achieved. The lack of consistency may be associated with sexual maturity or rate of fattening of the animal. For example, the stimulatory effects of 16L:8D photoperiods on live weight gain are not readily manifested in immature prepubertal heifers, but occur primarily during the peripubertal period. Short days are conducive to deposition of fat, which may account for the stimulatory effects of short days on live weight gain of white-tailed doe fawns and excessively fattened Holsteins. In contrast, long duration photoperiods stimulate protein accretion in cattle. The hormonal signals that mediate the anabolic effects of increasing exposure to light are not associated with change in insulin, thyroxine or growth hormone concentrations in the blood. Glucocorticoid concentrations in serum decrease with longer duration photoperiods which is consistent with an anabolic effect. Increasing daily light exposure to 16 h/d hastens the increase in concentrations of progesterone and testosterone in sera of peripubertal heifers and prepubertal bulls, respectively. Thus, change in secretion of reproductive hormones in the peripubertal period of cattle may be associated with the anabolic effects previously described and is consistent with gonad dependency. Prolactin concentrations in serum increase in sheep and cattle as duration of light exposure increases. But, there is no irrefutable proof that prolactin is responsible for the increased rates of gain or change in carcass composition associated with longer exposures to light. Thus, the hormonal mechanisms involved in photoperiod-induced alterations in growth remain to be established.     

Studies on nitrogen metabolism in rats of different age fed on a protein-free diet. 1. Changes of body mass

The changes of body mass of rats of different age fed on a protein-free diet (PFD) were investigated. An experiment was conducted on 350 male Wistar rats in 14 age groups ranging from 23 to 275 days and an initial individual shrunk body mass ranging from 37 to 470 grams. Each group of 25 rats of the same age was divided randomly into 5 subgroups corresponding to the PFD feeding periods of 3, 6, 9, 12 and 16 days. Before starting and after finishing each feeding period, the rats were fasted for 14 to 20 hours and weighed, thus determining the initial and the final shrunk body mass (SBi and SBf), respectively. SBf was closely correlated with SBi in all age groups (Table 3). SBf was corrected for SBi by linear covariance. Corrected SBf means are presented in Table 4. Logarithms of SBf means from this table were processed by linear regression method against log t (where t = 3, 6, 9, 12 and 16 days on PFD). Coefficients of regression between age groups (k) did not differ significantly and the common bc = -0.062 +/- 0.002 less than 0**. Changes of body mass of rats during 16 days of ad libitum feeding on PFD are described be the equation: Y = Ak X t-0.062 in which: Y = SBf (in grams) and the values of Ak correspond to SBi in age group k. This demonstrates that the changes of shrunk body mass did not significantly depend on the age but SBf was significantly related to SBi, the latter depending on the age of rats. SBf expressed as percentage of SBi (Figure 1) demonstrates that the losses of body mass were greatest during the first 6 days of feeding on PFD; during this period SBf decreased to about 91% and, during the subsequent 10 days, to about 84% of SBi. The results of this experiment suggest that the body mass of rats fed on PFD, for which the nitrogen balance was determined, should be expressed by the body mass actually linked to the endogenous nitrogen metabolism and not by the mean, or by the initial, body mass.     

The influence of dietary protein content on the performance of genetically lean or fat growing chickens

Genetically lean or fat male chickens were fed from 3 to 8 weeks of age on four diets of different protein content: 152, 172, 191 or 211 g/kg. The two lower protein contents depressed growth of lean chickens but had no adverse effects on fat chickens. In both lines increasing dietary protein decreased food: gain ratio and abdominal fat desposition relative to live body weight. Protein deposited and the efficiency of utilisation of dietary protein were higher in all instances in lean birds.     

Influences of dietary protein level,amino acid supplementation and environmental temperature on performance,body composition,organ weights and total heat production of growing pigs

The study was conducted to determine the effects of feeding a 16% CP diet, a 12% CP diet, or a 12% CP diet supplemented with crystalline Lys, Trp, and Thr (12% CP + AA diet) in a thermal-neutral (23 degrees C) or heat-stressed (33 degrees C) environment on various body and physiological measurements in growing pigs. Heat-stressed pigs were given a 15% lower daily feed allowance than thermal-neutral pigs to remove the confounding effect of feed intake caused by high temperature. No diet x temperature interaction was observed for any variables (P > 0.09) except for pig activity and pancreas weight. At 33 degrees C, pig activity and pancreas weight did not differ among dietary treatments (P > 0.05). In contrast, at 23 degrees C, pigs fed the 12% CP diet had greater activity than those fed the 16% CP diet or the 12% CP + AA diet (P < 0.05). Pancreas weight was greater for pigs fed the 12% CP + AA diet than those fed the 12% CP diet (P < 0.05) when maintained at 23 degrees C. Compared with 23 degrees C, the 33 degrees C temperature decreased pig activity, heat production, daily gain, feed efficiency, and affected the concentration and accretion of empty body protein and ash, as well as weights of heart, pancreas, stomach, and large intestine (P < 0.05). Pigs fed the 12% CP + AA diet attained similar levels of performance and rates of empty body water, protein, lipid, and ash deposition as pigs fed the 16% CP diet (P > 0.10). Pigs fed the 12% CP + AA diet had lower serum urea plus ammonia nitrogen concentrations (P < 0.01) and total heat production (P < 0.05) compared with those fed the 16% CP diet or the 12% CP diet. These results confirm that, with crystalline AA supplementation, growing pigs fed a 12% CP diet will perform similar to pigs fed a 16% CP diet. The data further indicate that lowering dietary CP and supplementing crystalline AA will decrease total heat production in growing pigs whether they are housed in a thermal-neutral or heat-stressed environment.     

Influence of chlortetracycline and dietary protein level on visceral organ mass of growing beef steers

Thirty-two beef steers (285 +/- 3 kg BW) were used to determine the effects of chlortetracycline and dietary protein level on visceral tissue mass, chemical composition, intestinal morphology, and proliferation rate indices. Steers were allotted randomly by weight to a factorial arrangement of dietary treatments consisting of either 10 or 13% CP diets top-dressed with a corn meal carrier (500 g/d) containing either 0 or 350 mg of chlortetracycline. After 84 d, steers were slaughtered and visceral organs removed and separated. Rinsed wet tissue mass was recorded; total RNA, total DNA, tissue DM, and tissue N content were determined; and tissue sections were prepared for immunohistochemical analysis. Thin tissue sections were evaluated to determine crypt depth and villus height as well as proliferation rate by immunohistochemical detection of the nuclear antigen Ki67. Rumen and abomasum weights and small intestinal length were greater (P < 0.04) in steers fed the 13% CP diet than in those fed the 10% CP diet on both an absolute weight basis and a percentage of empty BW. Chemical composition of the small intestinal and ruminal segments were largely unaffected by increased dietary protein. Increasing the dietary CP also increased the villus height in duodenal (P = 0.02) and the crypt depth of jejunal (P = 0.03) sections. Dietary administration of chlortetracycline decreased (P < 0.01) small intestinal weight both on absolute and empty BW bases. Nitrogen and RNA concentrations of the small intestinal segments were unaffected (P > 0.1) by dietary administration of subtherapeutic levels of chlortetracycline; however, because of increases (P < 0.05), or tendencies for an increase (P < 0.1), in the tissue content of DNA, the ratio of N to DNA was decreased (P < 0.05) or tended to be decreased (P < 0.1) in the small intestinal segments of the chlortetracycline-treated animals. The observed decrease in small intestinal epithelial mass does not appear to be due to alterations in cell proliferation rate but rather cell size. Consistent with this finding, cell proliferation, as determined by Ki67 antigen staining, was not affected by dietary treatment. Chlortetracycline administration decreased small intestinal mass that may be a result of decreased cell size.     

The effect of feeding low-phytate barley-soybean meal diets differing in protein content to growing pigs on the excretion of phosphorus and nitrogen

An experiment was conducted with growing pigs to determine the excretion of P and N in 4 barley-based diets formulated to contain 18 or 15% CP by using a normal barley (NB) or a low-phytate barley (LPB). The NB contained 0.31% total P and 0.19% phytate P; the LPB contained 0.32% total P and 0.01% phytate P. The diets were supplemented, when so required, with lysine, methionine, threonine, and tryptophan to meet their apparent ileal digestible supplies according to the NRC (1998). The diets containing NB were supplemented with inorganic P to meet the NRC (1998) recommendation for available P (0.23%). The diets containing LPB were not supplemented with inorganic P because these contained sufficient available P (0.27%). Eight barrows with an average BW of 20.9 kg were assigned to the 4 dietary treatments according to a repeated 4 x 4 Latin square design. The diets were fed at a rate of 2.5 times the ME requirement for maintenance. The barrows were fed twice daily, at 0800 and 1500, equal amounts each meal. Water was added to the feed at a ratio of 2.5:1. Each experimental period consisted of a 7-d adaptation period followed by a 5-d collection of feces and urine. The substitution of NB with LPB decreased (P < 0.001) the total P excretion by 38 and 43% for the 18 and 15% CP diets, respectively. Reducing the CP content from 18 to 15% decreased (P < 0.001) the N excretion by 29 and 32% for the NB and LPB diets, respectively. With the reduction in CP content, there was a decrease (P < 0.001) in the amount of N retained. The N:P ratio in manure of pigs fed the LPB diets was greater (P < 0.001) than from pigs fed the NB diets. These data indicate that P and N excretion can be greatly reduced by substitution of NB by LPB, and also by the reduction of the CP content, in diets for growing pigs.     

Effect of rumen-degradable protein balance deficit on voluntary intake, microbial protein synthesis, and nitrogen metabolism in growing double-muscled Belgian Blue bulls fed corn silage-based diet

Two trials were conducted to evaluate the effect of rumen-degradable protein balance (OEB) deficit on voluntary intake (trial 1), microbial protein synthesis, and N metabolism (trial 2) in growing double-muscled Belgian Blue bulls. In trial 1, six bulls (339 +/- 26 kg of initial BW) were used in a replicated 3 x 3 Latin square and received a diet of 60% corn silage and 40% concentrate with ad libitum intake (DM basis). Three concentrates were formulated by adding urea at the expense of barley to give similar dietary contents of intestinal digestible proteins, NE for fattening, and fermentable OM, but with different levels of OEB. Thus, 2 levels of OEB deficit (-23.7 and -9.2 g of OEB/kg of DM) were compared with a diet providing a slight OEB surplus (5.3 g of OEB/kg of DM). Voluntary DMI decreased linearly (P = 0.02) with decreasing rumen-degradable protein balance. This decrease in intake could explain the linear decrease in ADG observed when negative OEB diets were fed. In trial 2, six bulls (304 +/- 12 kg of initial BW) with cannulas in the rumen and proximal duodenum were used in a replicated 3 x 3 Latin square and fed diets similar to those used in trial 1 at an intake level of 85 g of DM/kg of BW(0.75). Diurnal variations of ruminal NH(3)-N and plasma urea-N concentrations were greatly influenced by the level of OEB in the diet. No differences in NDF and starch degradation in the rumen, microbial N flow at the duodenum, or efficiency of microbial protein synthesis in the rumen were noted among the levels of OEB in diets. The reductions of the OEB value from 5.3 g/kg of DM to -9.2 g/ kg of DM and -23.7 g/kg of DM were associated with reductions of 26.5 and 48.8% in urinary N output. Absolute amounts of N retained by the bulls increased significantly with the level of OEB in diets. Indeed, 51.4% of the incremental supply of N was excreted between -23.7 and -9.2 g of OEB/kg of DM diets, and 74.6% of the incremental supply of N was excreted between -9.2 and 5.3 g of OEB/kg of DM diets. Feeding diets characterized by an adequate intestinal digestible protein supply and a OEB close to -10 g of OEB/kg of DM could be a feeding strategy to reduce N losses from the farm with little effect on the animal performance and voluntary intake. Reduced OEB may reduce N excretion in the environment but may also result in decreased N retention.     

Effect of dietary protein level on nitrogen metabolism in the growing bovine: I. Nitrogen recycling and intestinal protein supply in calves

Eight Angus heifer calves (234 kg) were assigned to either a high (HP; 126 g N/d) or low (LP; 66.5 g N/d) protein intake. Calves received 4.8 kg DM/d consisting of 30% cottonseed hulls and 70% corn-soybean meal in equal portions at 4-h intervals. Single doses of 14C- and 15N-urea and 15N-ammonium sulfate were injected into the blood urea-N (BUN) and ruminal NH3-N (RAN) pools, respectively, to measure rate of flux through, and transfer of N between, these and bacterial N. Nitrogen balance was greater (P less than .05) for HP than for LP (56.9 vs 25.1 g N/d), but abomasal N flow as a percentage of N intake was greater (P less than .05) for LP than for HP (124 vs 71.1%). Pool size and net synthesis rate for both RAN and BUN pools were greater (P less than .05) for HP than for LP. Calves fed HP degraded more (P less than .05) BUN in the gastrointestinal tract than calves fed LP (37.4 vs 14.0 g N/d). Quantities of RAN absorbed from the rumen also were greater (P less than .05) for HP than for LP (14.2 vs 2.8 g N/d). The proportion of total gastrointestinal BUN degradation occurring in the rumen averaged 53 and 26% for LP and HP. Data are interpreted to suggest that net incorporation of BUN into bacterial protein (urea recycling) is inversely related to level of protein intake.     

Effects of dietary protein level and clinoptilolite on the weight gain and liver mineral response of growing lambs to copper supplementation

Growing male Synthetic I (1/2 Finnish Landrace x 1/4 Dorset x 1/4 Rambouillet) lambs were used in two experiments (64 lambs in Exp. 1 and 63 in Exp. 2) to test the hypothesis that dietary CP level (9 or 14% of diet as fed) and(or) clinoptilolite (clino; 0 or 2% of diet) affects growth and tissue mineral concentrations of growing lambs fed supplemental Cu. Lambs were individually fed their respective diets ad libitum and killed after 12 wk (Exp. 1) or 16 wk (Exp. 2) to obtain carcass measurements, organ weights and liver mineral concentrations. In Exp. 1, 20 ppm added Cu (as CuSO4.5H2O) increased mortality and depressed BW gain (P less than .01) and daily feed intake (P less than .05) in the presence or absence of clino and at both levels of CP. Liver Cu concentration was greater (P less than .01) in lambs fed added Cu than in those not fed Cu (408 ppm vs 110 ppm, respectively). Neither CP nor clino affected liver Cu concentration. Clinoptilolite increased daily gain of lambs fed high CP but not low CP (P less than .01). In Exp. 2, clino in the diet had no effect on daily gain or daily feed, but 20 ppm Cu addition depressed daily gain (P less than .01) and gain/feed (P less than .07). Organ weights and levels of trace elements other than Cu in the liver generally were not affected by diet in either experiment. It is concluded that high dietary CP or 2% dietary clino did not protect against toxic signs of Cu when Cu was added to the basal diet (10 ppm Cu) at 10 or 20 ppm.     

The influence of cellulose and various starches in feed on nitrogen metabolism in growing swine

In N-balance experiments with a total of 49 female fattening pigs with a live weight between 33 and 47 kg the influence of cellulose supplements (exchanger principle) and changing quotas of maize starch and maize soak starch in semisynthetic feed mixtures on parameters of N-utilization was studied. The results show that there may be a positive influence of the supplement of cellulose on total N utilization (b-value, Gebhardt, 1963). One can conclude that, apart from a shift of the ways of N-excretion through faeces and urine, the utilization of products of microbial protein synthesis for N-retention is possible to a nutrition-physiologically relevant degree. The influence of the kind of starch on N-utilization was small.     

Effect of dietary protein level on nitrogen metabolism in the growing bovine: II. Diffusion into and utilization of endogenous urea nitrogen in the rumen

Six Angus heifer calves (234 kg) were assigned to either a high (HP; 126.1 g N/d) or low (LP; 66.5 g N/d) protein intake to evaluate ruminal criteria associated with movement of blood urea-N (BUN)-derived NH3-N from the rumen wall into interior ruminal digesta. Calves received 4.8 kg DM/d of diets containing 30% cottonseed hulls and 70% cornsoybean meal in equal portions at 4-h intervals. Following single i.v. injections of 15N-urea, ruminal fluid was collected serially for 4 h postinjection from digesta located adjacent to the rumen wall (wall-proximate digesta; WPD) and from the center of the rumen digesta mass after manual agitation (center mixed digesta; CMD). Mean ruminal NH3-N (RAN) concentrations were higher (P less than .05) for HP than for LP, but were not affected (P greater than .05) by digesta sampling site. Ruminal urease activity was higher (P less than .05) for LP than for HP and tended (P = .14) to be higher for WPD than for CMD. Area under the 15N enrichment curve (AUC) ratios between sampling sites (WPD/CMD x 100) for RAN were greater (P less than .05) for LP than for HP. However, AUC ratios for bacterial N were not affected (P greater than .05) by protein level. Whereas BUN-derived 15NH3 appeared to thoroughly equilibrate with RAN in interior ruminal digesta with HP, there appeared to be a declining enrichment gradient for RAN from the rumen wall to the interior ruminal digesta with LP. Data are interpreted to suggest that bacteria at or near the rumen wall may preferentially utilize some BUN-derived NH3-N entering through the rumen wall in calves fed LP diets.     

日粮中不同类型大麦和不同蛋白质含量对生长猪氮、磷排泄量的影响

本试验研究了含有普通大麦（NB）或低植酸大麦（LPB）日粮（含有18％和15％蛋白质）对生长猪的氮和磷排泄量的影响。NB含有0．31％总磷和0．19％植酸磷;LPB含有0．32％总磷和0．01％植酸磷。结果表明：日粮中LPB代替NB,极显著地降低磷的排泄量：含有18％和15％蛋白质日粮,分别降低了38％和43％的磷排泄量（P〈0．001）。日粮CP含量从18％降到15％。极显著降低了N的排泄,含有NB和LBP日粮分别降低了29％和32％氮的排泄量（P〈O．001）。随着日粮蛋白质含量降低,极显著地降低了总氮的保留量（P〈0．001）。生长猪饲喂LPB型日粮的粪中的N：P比值比饲喂NB型日粮的高（P〈0．001）。总之,降低生长猪磷和氮的排泄量．可以通过LPB代替NB和也可以通过降低日粮中的CP含量。