Nitrogen metabolism and growth performance of gilts fed standard corn-soybean meal diets or low-crude protein,amino acid-supplemented diets

Two experiments were conducted to determine the CP concentration below which N retention and growth performance are reduced when low-protein, amino acid-supplemented, corn-soybean meal diets are fed. In a N balance trial (Exp. 1), 12 gilts (initial weight 41 kg) were fitted with urinary catheters and fed six different diets during three 7-d periods in an incomplete block design. The diets were: 1) 18% CP; 2) 14% CP + AA, 3) 16% CP; 4) 12% CP + AA; 5) 14% CP; and 6) 10% CP + AA. Amino acids (lysine, threonine, tryptophan, and methionine) were supplemented such that the concentrations in the low-protein diets were equal to those in their standard (4% CP higher) counterparts. Nitrogen retention (g/d) decreased (P < 0.01) as CP decreased, in both standard (27.10, 24.53, and 20.99) and low-protein (21.51, 19.18, and 15.83) diets, but was lower (P < 0.01) in low-protein diets. There were no differences among treatments (P > 0.05) in biological value (68.2% standard vs 71.0% low-protein). In a growth performance trial (Exp. 2), 36 gilts (initial weight 19.5 kg) were penned individually and fed one of six diets for 35 d in a randomized complete block design. Dietary treatments were a 16% CP standard diet and low-protein diets formulated to contain 15, 14, 13, 12, and 11% CP supplemented with crystalline lysine, tryptophan, threonine, and methionine to equal the total concentrations in the standard diet. Protein concentration affected (P < or = 0.05) ADG, ADFI, feed efficiency, fat-free lean gain, longissimus muscle area, plasma urea, and plasma concentrations of most essential AA. For most of these traits, the major difference was poor performance of pigs fed the 11% CP diet. Thus, in Exp. 1, at AA concentrations from deficient to excess, low-protein, amino acid-supplemented diets failed to produce the same N retention as the equivalent corn-soybean meal diets. However in Exp. 2, the same performance was obtained with 16, 15, 14, 13, and 12% CP. Based on these data, we suggest that N balance is more sensitive than growth to amino acid adequacy andthat other AA (e.g., isoleucine and valine) may limit growth performance when the protein concentration is reduced by more than four percentage units.     

Effects of amino acids supplementation in low crude protein diets on growth performance,carcass traits and serum parameters in finishing gilts

This study investigated the effects of amino acids (AA) supplementation in low crude protein (CP) diets on growth performance and carcass characteristics in finishing gilts. One hundred and eighty gilts (59.1 ± 5.1 kg) were randomly allotted to one of five diets which consisted of a high CP (15.6%) diet or four low CP (11.6%) diets for 50 days. The low CP diets were supplemented with lysine + threonine + methionine (LCM), LCM + tryptophan (LCT), LCT + valine (LCV) or LCV + isoleucine (LCI), respectively. Gilts were housed at six pigs per pen with six pens per treatment. At the end of the 50‐day experiment, 30 gilts (one pig per pen) with average body weight (BW) of 98 kg were killed to evaluate carcass traits. The pigs fed the diet supplemented with LCV obtained the highest average daily gain (ADG), which was higher than those of pigs fed the diet supplemented with LCM (P < 0.05). Dietary supplementation with tryptophan, valine and isoleucine in low CP diets increased ADG (linear and quadratic effect, P < 0.05), serum levels of valine (quadratic effect, P < 0.05) and isoleucine (linear and quadratic effect, P < 0.05) and immunoglobulin G (IgG) and IgA (linear and quadratic effect, P < 0.05) in finishing gilts. © 2016 Japanese Society of Animal Science     

Dietary protein levels and amino acid supplementation patterns alter the composition and functions of colonic microbiota in pigs

Different dietary nitrogen (N) patterns may have different effects on gut microbiota. To investigate the effects of different crude protein (CP) levels or essential amino acids (EAA) supplementation patterns on the structure and functions of colonic microbiota, 42 barrows (25 ± 0.39 kg) were randomly assigned to 7 dietary treatments including: diet 1, a high CP diet with balanced 10 EAA; diet 2, a medium CP diet with approximately 2% decreased CP level from diet 1 and balanced 10 EAA; diets 3, 4, 5, 6 and 7, low CP diets with 4% decreased CP level from diet 1. Specifically, diet 3 was only balanced for Lys, Met, Thr and Trp; diets 4, 5 and 6 were further supplemented with Ile, Val and Ile + Val on the basis of diet 3, respectively; and diet 7 was balanced for 10 EAA. Results over a 110-d trial showed that reducing the CP level by 2% or 4% dramatically decreased N intake and excretion (P < 0.05) in the presence of balanced 10 EAA, which was not observed when altering the EAA supplementation patterns in low CP diet (−4%). With balanced 10 EAA, 2% reduction in dietary CP significantly reduced Firmicutes-to-Bacteroidetes (F:B) ratio and significantly elevated the abundance of Prevotellaceae NK3B31 (P < 0.05); whereas 4% reduction evidently increased the abundances of Proteobacteria, Succinivibrio and Lachnospiraceae XPB1014 (P < 0.05). Among the 5 low CP diets (−4%), supplementation with Ile, or Val + Ile, or balanced 10 EAA increased F:B ratio and the abundance of Proteobacteria. In addition, the predicted functions revealed that different CP levels and EAA balanced patterns dramatically altered the mRNA expression profiles of N-metabolizing genes, the “N and energy metabolism” pathways or the metabolism of some small substances, such as amino acids (AA) and vitamins. Our findings suggested that reducing the dietary CP levels by 2% to 4% with balancing 10 EAA, or only further supplementation with Ile or Val + Ile to a low protein diet (−4%) reduced the N contents entering the hindgut to various degrees, altered the abundances of N-metabolizing bacteria, and improved the abilities of N utilization.     

Nitrogen balance in barrows fed low-protein diets supplemented with essential amino acids

This study was conducted to determine the effect of addition of essential amino acids (EAA) to low-protein diets on N balance in barrows. Thirty barrows (Duroc × Yorkshire) with an initial BW of 36 kg were fed 5 corn- and soybean meal-based diets containing 13.6 to 18.2% crude protein (CP) for 10 d in a randomized complete block design. The 18.2% CP diet was formulated without addition of EAA (Lys, Met or Thr). The other diets contained 13.6 to 16.5% CP and were supplemented with EAA to provide 0.83% true digestible lysine equal to that in the 18.2% CP diet. Fecal, urinary, and total N excretion as well as N retention (g/d) decreased with decreasing dietary CP level (P < 0.01). The apparent digestibility of N was almost the same for the 18.2 and 16.5 CP diets, but the value was 2% higher (P = 0.07) than that for the 13.6% CP diet. These findings indicate that, compared with the 18.2% CP diets, supplementation with three EAA to the lowest-protein diets (13.6 CP) is inadequate for maximum intestinal protein digestion, amino acid absorption, or tissue protein deposition in growing barrows.     

Effect of cellulase supplementation in low-crude protein diets on performance, nitrogen excretion, fat deposition, hepatic lipogenic and lipolytic enzyme activity in broilers

1. Two experiments were conducted to investigate the effect of dietary enzyme supplementation of a low-protein diet on performance, nitrogen excretion, fat deposition, hepatic lipogenic and lipolytic enzyme activity in 7-21- (Experiment 1) and 21-42-d-old (Experiment 2) male broiler chicks. 2. Chicks were given diets containing 210 g (Experiment 1) or 170 g (Experiment 2) crude protein (CP)/kg (Control), amino acid-fortified diets 190 g (Experiment 1) and 150 g (Experiment 2) CP/kg (Low-protein), and a low-protein diet supplemented with 1000 U/kg of cellulase. 3. In Experiment 1, growth performance and abdominal fat deposition were not affected by dietary treatments, and birds given low-protein diets excreted less nitrogen. The activities of hepatic lipogenic and lipolytic enzymes were not different among the three dietary groups. 4. In Experiment 2, the dietary treatment did not affect growth performance or abdominal fat weight. Nitrogen excretion was significantly lower in chicks given the 150 g/kg CP diet than those on the 170 g/kg CP diet; however, nitrogen retention was no different among the treatments. Dietary CP and enzyme supplementation did not significantly affect hepatic enzyme activities. 5. These results suggest that CP content in the broiler diet can be reduced by 20 g/kg without lowering performance by the supplementation of crystalline amino acids, and can reduce nitrogen excretion by about 25%. Cellulase supplementation of a low-CP diet slightly lowered abdominal fat deposition; however, it did not significantly affect hepatic lipogenic and lipolytic enzyme activity.     

Effect of micronized pea and enzyme supplementation on nutrient utilization and manure output in growing pigs

An experiment was done to determine manure output, N and P excretion, and apparent digestibilities of AA, CP, P, and DM in growing pigs fed barley-based diets containing micronized or raw peas with or without supplementation with enzyme containing primarily beta-glucanase and phytase (Biogal S+). Eight barrows (21.5 +/- 1.2 kg of initial BW) fitted with T-cannulas at the distal ileum were used in a 40-d trial and housed in metabolism cages. Pigs were assigned in a replicated 4 x 4 Latin square design to 4 experimental diets: 1) barley-raw peas control (BRP), 2) barley-micronized peas (BMP), 3) BRP plus enzyme, and 4) BMP plus enzyme (BMP+E). Pigs received 2.6 times maintenance energy requirements based on BW at the beginning of each experimental period. During each experimental period, pigs were acclimatized to their respective diets for 5 d followed by a 3-d period of total fecal and urine collection and another 2-d period of ileal digesta collection. Samples were analyzed for DM, AA (diets and digesta only), N, and P. Wet fecal output of BRP plus enzyme-fed pigs tended to be lower (P = 0.07) than the amount produced by BMP-fed pigs. The amounts of dry feces and urine produced were not different among treatments (P > 0.10). Supplementing the BRP and BMP diet with enzyme increased (P = 0.002) the daily P retained per pig. Pigs fed the enzyme-supplemented diets tended to have lower (P = 0.06) fecal P excretion and greater urinary P excretion (P = 0.001) compared with pigs fed the nonsupplemented diets, but total P excretion was not influenced by diet (P > 0.10). Pigs fed the BMP+E diet retained more (P = 0.006) N per day than pigs fed the BMP diet. However, N excretion was not influenced by dietary treatment (P > 0.10), although BMP+E-fed pigs excreted 13.2% less N in the feces compared with those fed the nonenzyme supplemented controls. Inclusion of micronized peas with or without enzyme supplementation did not affect urinary or fecal N excretion (P > 0.10) compared with the BRP. Dietary treatment had no effect (P > 0.10) on ileal or fecal DM or CP digestibilities. Apparent ileal digestibilities of AA were usually lower (P < 0.05) in the BRP diet compared with the other diets. Enzyme supplementation improved P digestibility at the ileal and fecal level. The current results indicate that utilizing micronized peas in barley-based pig grower diets enhances P retention.     

Effect of dietary crude protein level on growth performance,blood characteristics,and indicators of intestinal health in weanling pigs

An experiment was conducted to test the hypothesis that reducing crude protein (CP) in starter diets for pigs reduces post-weaning diarrhea and improves intestinal health. In total, 180 weanling pigs were allotted to 3 diets containing 22, 19, or 16% CP. Fecal scores were visually assessed every other day. Blood samples were collected from 1 pig per pen on days 1, 6, 13, 20, and 27, and 1 pig per pen was euthanized on day 12. Results indicated that reducing dietary CP reduced (P < 0.01) overall average daily gain, gain to feed ratio, final body weight, and fecal scores of pigs. Pigs fed the 16% CP diet had reduced (P < 0.01) serum albumin compared with pigs fed other diets. Blood urea nitrogen, haptoglobin, interleukin-1β, and interleukin-6 concentrations in serum were greatest (P < 0.01) on day 13, whereas tumor necrosis factor-α and interleukin-10 concentrations were greatest (P < 0.01) on day 6. Villus height in the jejunum increased (P < 0.05) and crypt depth in the ileum was reduced (P < 0.01) if the 19% CP diet was fed to pigs compared with the 22% CP diet. A reduction (P < 0.05) in mRNA abundance of interferon-γ, chemokine ligand 10, occludin, trefoil factor-2, trefoil factor-3, and mucin 2 was observed when pigs were fed diets with 16% CP. In conclusion, reducing CP in diets for weanling pigs reduces fecal score and expression of genes associated with inflammation.     

Limited and excess dietary protein during gestation affects growth and compositional traits in gilts and impairs offspring fetal growth

The aim of this study was to investigate whether dietary protein intake during gestation less than or greater than recommendations affects gilts growth and body composition, gestation outcome, and colostrum composition. German Landrace gilts were fed gestation diets (13.7 MJ of ME/kg) containing a low (n = 18; LP, 6.5% CP), an adequate (n = 20; AP, 12.1%), or a high (n = 16; HP, 30%) protein content corresponding to a protein:carbohydrate ratio of 1:10.4, 1:5, and 1:1.3, respectively, from mating until farrowing. Gilts were inseminated by semen of pure German Landrace boars and induced to farrow at 114 d postcoitum (dpc; Exp. 1). Energy and protein intake during gestation were 33.3, 34.4, and 35.8 MJ of ME/d (P < 0.001) and 160, 328, and 768 g/d, respectively, in LP, AP, and HP gilts (P < 0.001). From insemination to 109 dpc, BW gain was least in LP (42.1 kg), intermediate in HP (63.1 kg), and greatest in AP gilts (68.3 kg), whereas increase of backfat thickness was least in gilts fed the HP diet compared with LP and AP diets (3.8, 5.1, 5.0 mm; P = 0.01). Litter size, % stillborn piglets, and mummies were unaffected (P > 0.28) by the gestation diet. Total litter weight tended to be less in the offspring of LP and HP gilts (14.67, 13.77 vs. 15.96 kg; P = 0.07), and the percentage of male piglets was greater in litters of HP gilts (59.4%; P < 0.01). In piglets originating from LP and HP gilts, individual birth weight was less (1.20, 1.21 vs. 1.40 kg; P = 0.001) and birth weight/crown-rump length ratio was reduced (45.3, 46.4 vs. 50.7 g/cm; P = 0.003). Colostrum fat (7.8, 7.4 vs. 8.1%) and lactose concentrations (2.2, 2.1 vs. 2.6%) tended to be reduced in LP and HP gilts (P = 0.10). In Exp. 2, 28 gilts (LP, 10; AP, 9; HP, 9) were treated as in Exp. 1 but slaughtered at 64 dpc. At 64 dpc, LP gilts were 7% lighter than AP gilts (P = 0.03), whereas HP gilts were similar to AP gilts. Body composition was markedly altered in response to LP and HP feeding with less lean (P < 0.01) and greater fat content (P = 0.02 to 0.04) in LP and less fat content (P = 0.02 to 0.04) in HP gilts. Fetal litter weight and number, and embryonic survival at 64 dpc were not affected by the diets. These results indicated that gestation diets containing protein at 50 and 250% of recommendations and differing in protein:carbohydrate ratio led to marked changes in protein and fat metabolism in gilts resulting in fetal growth retardation of 15%, which mainly occurred during the second half of gestation.     

Effect of supplementation of fresh and ensiled clovers to ryegrass on nitrogen loss and methane emission of dairy cows

Two experiments were carried out to compare white clover with red clover as supplementation to ryegrass, in ensiled and fresh form, for differences in nitrogen loss and methane emission by dairy cows. In experiment 1, fresh ryegrass was mixed with fresh white (WF) or red clover (RF) (60/40 on dry matter basis). Experiment 2 involved similar mixed diets in ensiled form (WS and RS, respectively), and two ryegrass silage diets, without (GS) or with supplementary maize gluten meal (600 g protein/kg DM; GS+). Barley was supplemented to meet the calculated requirements for milk production. The type of clover did not affect crude protein (CP) intake in experiment 1. In experiment 2, the highest CP intakes were observed for cows on the GS+ diet (P < 0.05), followed by the WS and RS diet, compared to the GS diet. Within experiments, no treatment effects occurred for intake of digestible organic matter, milk and milk protein yield, while milk urea and urine N excretion mostly reflected the differences in CP intake in experiment 2. The highest absolute N excretions (P < 0.001) occurred with the GS+ diet, compared to the other diets. Per unit of N intake, a tendency for highest urine N losses with GS+ was still noticeable. The slurry characteristics were not affected by clover type during storage in experiment 1. In experiment 2, initial treatment differences in ammonia-N levels (P < 0.01) in the slurry were still observed after 8 weeks of storage. Clover supplementation, but not clover type, slightly enhanced gaseous N losses per cow per day in relation to GS, but not as much as GS+ (+53%). Gaseous N losses relative to milk N yield were slightly lower (P < 0.1) with fresh red clover compared to white clover, a trend not apparent in experiment 2 with silages where levels were elevated with GS+. Methane emissions were not affected (P > 0.05) either by clover supplementation or by clover type in both experiments. This study illustrates that the white and red clovers investigated were widely similar for their effects on N losses and methane emission in dairy cows. Our findings imply that supplementation of white or red clover to a high-protein ryegrass could enhance nitrogen losses to the environment, and would not be beneficial in terms of reducing methane emissions.     

不同蛋白质水平条件下氨基酸平衡日粮对生长猪氮、磷及能量代谢的影响

选用平均体重为(40±2)kg杜长大三元杂交去势公猪3头,按3×3的拉丁方进行试验设计,试验分3期,每期为7 d,采用全收粪法,研究不同蛋白质(CP)水平的氨基酸平衡日粮CP水平分别为14%、16%和18%)对氮、磷及能量代谢的影响。结果表明:不同蛋白质水平日粮处理间的氮表观消化率差异不显(著P>0.05),氮的沉积率以14%CP和16%CP组显著高于18%CP组(P<0.05),而14%CP和16%CP组之间无显著差异(P>0.05)。粪氮排出量14%CP日粮组显著低于16%CP和18%CP日粮组(P<0.05),16%CP日粮组和18%CP日粮组间无显著差异(P>0.05)。随着日粮蛋白质水平下降,生长猪的氮排出量、粪氮和尿氮均减少,总排泄氮中尿氮的比例较大,而粪氮则较少。不同蛋白质水平日粮对磷和能量的消化利用无显著影响(P>0.05)。     

Effects of feeding diets containing low crude protein and coarse wheat bran as alternatives to zinc oxide in nursery pig diets

Two experiments were conducted to determine the effects of crude protein (CP) level in diets containing coarse wheat bran (CWB) with or without pharmacological levels of Zn (provided by zinc oxide: ZnO) on growth performance and fecal DM of nursery pigs. In experiment 1, 360 barrows (Line 200 × 400, DNA, Columbus, NE, initially 5.6 kg) were allotted to 1 of 6 dietary treatments from d 0 to 21 after weaning with 5 pigs per pen and 12 pens per treatment. Treatments included a positive control diet (21% CP) with 3,000 mg/kg Zn in phase 1 and 2,000 mg/kg in phase 2; negative control (21% CP) with 110 mg/kg added Zn, and 4 diets containing 4% CWB and 110 mg/kg added Zn formulated to contain 21%, 19.5%, 18%, or 16.5% CP. The 2 control diets and 21% CP CWB diet contained 1.40% standardized ileal digestible (SID) Lys in phase 1 and 1.35% SID Lys in phase 2, while the 19.5%, 18%, and 16.5% CP diets contained 1.33, 1.25 and 1.20% Lys, respectively, in both phases. Pigs fed the positive control diet containing pharmacological ZnO had increased (P < 0.05) ADG and G:F compared with the negative control and the 21% CP CWB diet. Reducing CP (concurrently with SID Lys) in diets containing CWB decreased ADG and G:F (linear, P = 0.002); however, fecal DM increased (linear, P = 0.005). In experiment 2, two groups of 300 and 350 pigs, initially 7.0 and 6.2 kg, respectively, were used with 5 pigs per pen and 26 pens per treatment. The objective was to determine if adding back essential AA would improve growth performance of pigs fed the low CP diets. All dietary treatments were fed for 13 days, contained 4% CWB, and consisted of: (1) positive control with 2,000 mg/kg of Zn and 21% CP (1.35% SID Lys); (2) no ZnO and 21% CP; and 3 diets with no ZnO formulated to 18% CP and (3) 1.2% SID Lys; (4) 1.35% SID Lys by the addition of feed grade amino acids (AA), and (5) diet 4 with non-essential amino acids (NEAA; Gly and Glu). Pigs fed 21% CP with ZnO had increased (P = 0.001) ADG compared to those fed 18% CP (1.35% SID Lys) with high levels of feed grade amino acids or those fed the reduced SID Lys (1.2%) diet. Overall, G:F was improved (P < 0.001) for pigs fed 21% CP diets and those fed the 18% CP diet with NEAA compared to pigs fed 1.2% SID Lys and pigs fed high levels of feed grade amino acids. Fecal DM was increased for pigs fed the reduced SID Lys diet. In summary, pharmacological levels of Zn improve pig growth performance, but reducing CP (and subsequently SID Lys) decreased nursery pig growth performance.     

低蛋白饲粮添加植酸酶和非淀粉多糖酶对生长猪生长性能和养分排泄量的影响

试验旨在研究低蛋白质饲粮添加植酸酶和非淀粉多糖(NSP)酶对生长猪生长性能、养分排泄量的影响。54头平均初始体重为(41.92±2.6)kg的杜长大三元杂交猪分为3组,每组3个重复,每个重复6头猪。1组为对照组(饲粮粗蛋白质水平为17.4%),2、3组为试验组,2组在1组基础上,饲粮粗蛋白质水平降至14.3%、总磷水平降低0.1个百分点,添加植酸酶;3组在2组基础上添加NSP酶,试验期38 d。试验结果表明,2组的平均日增重、料重比比1组分别提高7.64%和1.94%(P0.05),其余各组间差异不显著(P0.05);粪N浓度2、3组比1组分别降低18.58%、23.01%(P0.05);粪P浓度2、3组比1组分别降低40.23%、39.08%(P0.01)。由此可见,将常规饲粮粗蛋白质水平降低3个百分点、总磷水平降低0.1个百分点,并添加植酸酶,能显著提高生长猪平均日增重,显著减少粪氮含量,极显著减少粪磷含量;在此基础上,继续添加NSP酶不影响生长猪生长性能和粪中养分含量。     

Optimum grape pomace proportion in feedlot cattle diets: ruminal fermentation,total tract nutrient digestibility,nitrogen utilization,and blood metabolites

Because of its high content of polyphenolic compounds, the dietary inclusion of grape pomace (GP) in ruminant diets can reduce reactive nitrogen (N) and methane emissions and enhance the shelf life and beneficial fatty acids (FAs) content of meat. However, the dietary inclusion of GP beyond a threshold that is still to be determined for feedlot cattle can also compromise nutrient supply and, thus, growth performance. This study investigated the optimum proportion of GP in finishing cattle diets. Nutrient intake and apparent total tract digestion, ruminal pH and fermentation, estimated microbial protein synthesis, route of N excretion, and blood metabolites were measured. Six ruminally fistulated crossbred beef heifers (mean initial body weight ± SD: 714 ± 50.7 kg) were used in a replicated 3 × 3 Latin square with 21-d periods. Dietary treatments were 0%, 15%, and 30% of dietary dry matter (DM) as GP, with diets containing 84%, 69%, and 54% dry-rolled barley grain, respectively. There was a linear increase (P = 0.07) in DM intake and quadratic change (P ≤ 0.01) in neutral detergent fiber (NDF) intake. There was a quadratic change (P ≤ 0.04) in apparent total tract DM, NDF, and crude protein digestibility as dietary GP content increased. However, there were no treatment effects (P ≥ 0.18) on total ruminal short-chain FA concentration and duration and area pH < 6.2, 5.8, and 5.5. Although N intake did not differ (269, 262, 253 g/d; P = 0.33) across dietary treatments, feeding GP led to a tendency for a quadratic change (P ≤ 0.07) in ruminal ammonia-N and plasma urea-N concentrations. Total N excretion also changed (quadratic, P = 0.03) because of changes (quadratic, P = 0.02) in fecal N excretion as urinary excretion of N and urea-N did not differ (P ≥ 0.15) across treatments. Feeding GP led to quadratic changes (P ≤ 0.01) in fecal excretion of fiber-bound N. Microbial N flow and apparent N retention also changed (quadratic, P ≤ 0.04) as dietary GP proportion increased. In conclusion, responses to dietary GP proportion were mostly quadratic with indications that nutrient supply as reflected by changes in apparent total tract nutrient digestibility, microbial N supply, and apparent N retention could be compromised beyond a 15% dietary inclusion level.     

Effects of magnesium on the performance of sows and their piglets

The objective of this study was to evaluate the effects of supplemental magnesium (Mg) on the performance of gilts and parity 3 sows and their piglets. Fifty-six gilts (Trial 1) and 56 sows (Trial 2) were assigned to one of 4 treatments according to their mating weight, respectively. The treatments comprised corn-soybean meal based gestation and lactation diets (0.21% magnesium) supplemented with 0, 0.015, 0.03, or 0.045% Mg from mating until weaning. The results showed that magnesium supplementation significantly (P < 0.05) reduced the weaning to estrus interval in both gilts and sows. There were significant effects (P < 0.05) of supplemental magnesium on the total number of piglets born, born alive and weaned in sows. In late gestation and lactation, the digestibility of crude fiber (quadratic effects, P < 0.05), and crude protein (P < 0.05), were significantly influenced by magnesium in gilts and sows, respectively. There were differences among the 4 groups in terms of the apparent digestibility of dry matter and crude fiber in sows (P < 0.05) during both early and late gestation. The apparent digestibility of gross energy was increased for sows in late gestation (P < 0.05), and lactation (quadratic effects, P < 0.05). At farrowing and weaning, serum prolactin levels and alkaline phosphate activities linearly increased in sows as the Mg supplementation increased (P < 0.05). Serum Mg of sows at farrowing and serum urea nitrogen of sows at weaning was significantly influenced by Mg supplementation (P < 0.05). The Mg concentration in sow colostrum and the serum of their piglets were increased by supplemental magnesium (P < 0.05). In addition, growth hormone levels were linearly elevated (P < 0.05) in the serum of piglets suckling sows. Our data demonstrated that supplemental magnesium has the potential to improve the reproduction performance of sows, and the suitable supplemental dose ranged from 0.015% to 0.03%.     

Impacts of dietary protein level and feed restriction during prepuberty on mammogenesis in gilts

The possible roles of dietary protein level and feed restriction in regulating mammary development of prepubertal gilts were investigated. Cross-bred gilts were fed a commercial diet until 90 d of age and then divided into four nutritional regimens based on two pelleted diets (as-fed basis): a high-protein diet (HP = 13.8 MJ of ME, 1.0% total lysine, 18.7% CP) and a low-protein diet (LP = 13.8 MJ of ME, 0.7% total lysine, 14.4% CP). Nutritional regimens were as follows: 1) HP ad libitum until slaughter (n = 22, T1); 2) HP ad libitum until 150 d of age followed by LP until slaughter (n = 20, T2); 3) LP ad libitum until slaughter (n = 21, T3); and 4) HP with a 20% feed restriction until slaughter (n = 19, T4). Gilts were weighed, their backfat thickness was measured, and jugular blood samples were obtained on d 90, 150, and at slaughter to determine concentrations of prolactin, IGF-I, leptin, and glucose. Gilts were slaughtered 8+/-1 d after their first or second estrus (202.7+/-14.5 d of age). Mammary glands were excised, parenchymal and extraparenchymal tissues were dissected, and composition of parenchymal tissue (protein, fat, DM, DNA, protein/DNA) was determined. The T4 gilts weighed less (P < 0.01) and had less backfat (P < 0.01) than did gilts on other treatments on d 150 and at slaughter. Treatments had no significant effects on prolactin, IGF-I, or glucose concentrations, but there was a treatment x day interaction (P < 0.01) for leptin, with concentrations being lower at slaughter in restricted-fed (T4) vs. LP (T3) gilts (P < 0.05). There was less extraparenchymal mammary tissue (P < 0.01) in T4 gilts than in gilts from the other groups and a tendency (P = 0.13) for the amount of parenchymal tissue to be lower in T4 gilts. In conclusion, a lower lysine intake during prepuberty did not hinder mammary development of gilts, but a 20% feed restriction decreased mass of parenchymal and extraparenchymal tissues. The effect of feed restriction on extraparenchymal tissue is most likely associated with the lower fat deposition.     

Nutrient utilization and manure P excretion in growing pigs fed corn-barley-soybean based diets supplemented with microbial phytase

The effect of high levels of microbial phytase supplementation in diets for growing pigs was studied in a 2‐week performance and nutrient digestibility trial involving 28 growing pigs weighing 16.4 ± 1.06 (mean ± SD) kg. Seven corn‐barley‐soybean meal‐based diets consisting of a positive control (PC) formulated to meet or exceed NRC nutrient requirements; a negative control (NC) with non‐phytate P reduced by 0.1% unit from NRC requirement and fed without or with 500 or 1000 U/kg; a doubled negative control (DNC) with no added inorganic P and fed without or with 2000 or 4000 U/kg. Chromic oxide was added as an indigestible marker and all diets were fed as mash. Pigs fed the PC diet had a higher P digestibility compared with those fed the NC (P < 0.02) and the DNC (P < 0.001) diets. Supplementing the NC diet with pyhtase tended to improve P digestibility (P < 0.10). However, addition of phytase to the DNC diet resulted in linear (P < 0.001) and quadratic (P < 0.03) increases in P digestibility with an overall improvement of 8% and 121% at 4000 phytase U/kg of diet, respectively, compared with the PC and DNC diets. Apparent total tract digestibility of N, OM and DM were higher (P < 0.05) in the PC diet compared with the DNC diet, but not the NC diet (P < 0.10). No effect of phytase addition to NC was observed on Ca, N, DM and OM digestibility. Phytase addition to the DNC diet resulted in a linear increase (P < 0.05) in N, DM and OM digestibility but not Ca. Increasing the levels of phytase supplementation in the NC and the DNC diets linearly decreased fecal P (P < 0.05) content by 45 and 42%, respectively. Adding phytase at 1000 or 4000 U/kg increased P retention (P < 0.05) by 14.3 or 15.6% units, respectively, compared with the PC diet. Urinary P excretion was higher in the group fed the PC diet compared with those fed the NC and DNC diets (P < 0.05). The results of this study show that complete removal of inorganic P from growing pig diets coupled with phytase supplementation improves digestibility and retention of P and N, thus reducing manure P excretion without any negative effect on pig performance.     

Effects of exposure to high ambient temperature and dietary protein level on performance of multiparous lactating sows

Fifty-nine multiparous Large White x Landrace sows were used to determine the effects of high ambient temperature and level of dietary heat increment on lactation and reproductive performance. During a 28-d lactation and the 14-d postweaning period, ambient temperature was maintained constant at 20 or 29 degrees C. Experimental diets fed during lactation were a control diet (NP; 17.6% crude protein) and two low-protein diets obtained by reduction of CP level (LP; 14.2% CP) and both reduction of CP and addition of 4% fat (LPF; 15.2% CP); the NE:ME ratio was 74.3, 75.6, and 75.8% for NP, LP, and LPF diets, respectively. All diets provided 0.82 g of digestible lysine/MJ of NE, and ratios between essential amino acids and lysine were above recommendations. During the ad libitum period (i.e., between d 7 and 27 of lactation), ADFI and NE intake decreased, respectively, from 7.63 to 4.22 kg and 82.0 to 43.3 MJ of NE when the temperature increased from 20 to 29 degrees C. Exposure to 29 degrees C reduced litter BW gain (2,152 vs 2,914 g/d) and increased lactation BW loss (34 vs 16 kg) but increased postweaning BW gain (2 vs - 4 kg). Expressed per kilogram of feed intake, water intake increased from 4.0 to 7.5 L between 20 and 29 degrees C. Compared with the NP diet, low-CP diets (LP or LPF) maintained performance and reduced total N excretion (-22.5%) in lactating sows at thermoneutrality and attenuated the negative effects of high temperature on NE intake and BW loss (40.9 vs 47.9 MJ of NE/d and 41 vs 30 kg for NP and LP + LPF diets, respectively). Temperature and diet composition did not affect the reproductive performances, and the mean weaning-to-estrus interval was 4.9 d. The respiratory rate and skin, udder, and rectal temperatures increased markedly at 29 degrees C (105 vs 33 breaths per min and 37.8 vs 36.1 degrees C, 38.9 vs 38.2 degrees C, and 39.5 vs 38.8 degrees C, respectively) without any effect of diet. In conclusion, low heat increment diets (i.e., with reduced CP/NE ratio) did not affect lactation performance of sows at thermoneutrality and attenuated the effects of high ambient temperature on energy intake and BW loss. At any ambient temperature, N excretion can be markedly reduced.     

The effects of pharmacological levels of zinc,diet acidification,and dietary crude protein on growth performance in nursery pigs

This experiment was conducted to evaluate potential replacements for pharmacological levels of Zn (provided by Zn oxide), such as diet acidification (sodium diformate) and low dietary crude protein (CP: 21 vs 18%) on nursery pig performance and fecal dry matter (DM). A total of 360 weaned pigs (Line 200 × 400, DNA, Columbus, NE; initially 5.90 ± 0.014 kg) were used in a 42-d growth study. Pigs were weaned at approximately 21 d of age and randomly assigned to pens (five pigs per pen). Pens were then allotted to one of eight dietary treatments with nine pens per treatment. Experimental diets were fed in two phases: phase 1 from weaning to day 7 and phase 2 from days 7 to 21, with all pigs fed the same common diet from days 21 to 42. The eight treatment diets were arranged as a 2 × 2 × 2 factorial with main effects of Zn (110 mg/kg from days 0 to 21 or 3,000 mg/kg from days 0 to 7, and 2,000 mg/kg from days 7 to 21), diet acidification, (without or with 1.2% sodium diformate), and dietary CP (21% or 18%, 1.40% and 1.35% in phases 1 and 2 vs. 1.20% standardized ileal digestible Lys, respectively). Fecal samples were collected weekly from the same three pigs per pen to determine DM content. No 2- or 3-way interactions (P > 0.05) were observed throughout the 42-d study for growth performance; however, there was a Zn × acidifier × CP interaction (P < 0.05) for fecal DM on day 7 and for the overall average of the six collection periods. Reducing CP without acidification or pharmacological levels of Zn increased fecal DM, but CP had little effect when ZnO was present in the diet. From days 0 to 21, significant (P < 0.05) main effects were observed where average daily gain (ADG) and gain:feed (G:F) increased for pigs fed pharmacological levels of Zn, sodium diformate, or 21% CP (P < 0.065). In the subsequent period (days 21 to 42) after the experimental diets were fed, there was no evidence of difference in growth performance among treatments. Overall (days 0 to 42), main effect tendencies were observed (P < 0.066) for pigs fed added Zn or sodium diformate from days 0 to 21, whereas pigs fed 21% CP had greater G:F than those fed 18% CP. Pig weight on day 42 was increased by adding Zn (P < 0.05) or acidifier (P < 0.06) but not CP. In summary, none of the feed additives had a major influence on fecal DM, but dietary addition of pharmacological levels of Zn or sodium diformate independently improved nursery pig performance.     

The effect of short-term phytase supplementation on the apparent total tract digestibility of calcium and phosphorus and the reproductive performance of late gestation and lactating sows fed diets without mineral phosphorus

The objective of this study was to measure apparent total tract digestibility (ATTD) of Ca and P as well as reproductive performance in late gestation and lactating sows supplemented with a novel phytase and to compare the response to phytase supplementation between late gestation and lactating sows. A total of 45 late gestation sows and 45 lactating sows were used in experiments 1 and 2, respectively, in a completely randomized design. The sows were provided with a control diet or the control diet supplemented with 187.5 or 375 FYT phytase/kg feed for 10 days. The diets were prepared according to the formulas in use for production but without any inorganic P supplement. Titanium dioxide was included at 3 g/kg feed as an indigestible marker. Each dietary treatment was replicated with 15 sows individually housed in farrowing stalls. The sows were allowed to adapt to the experimental diets for 5 days before a 5-d fecal collection by grab sampling, and the performance of the sows and their litters were measured until weaning. The results showed that the ATTD of Ca increased linearly (P < 0.001), while the ATTD of P increased both linearly and quadratically (P < 0.01) with increasing supplementation of phytase in both late gestation and lactating sows. There was no significant effect of phytase on the ATTD of dry matter, crude protein, and gross energy, and the performance of the sows and their progenies. The phytase added at 187.5 and 375 FYT/kg feed released 0.07% and 0.10% digested P, respectively, in late gestation sows, which compared with 0.09% and 0.12% digested P in lactating sows. In conclusion, a novel phytase at 187.5–375 FYT/kg feed could release 0.07–0.12% digestible P for sows. It appeared that using the P digestibility values of feed ingredients listed by NRC to formulate a diet for sows might overestimate dietary P supply and a greater response to phytase supplementation could be expected in lactating sows than in late gestation sows.     

Isoleucine and valine supplementation of a low-protein corn-wheat-soybean meal-based diet for piglets: growth performance and nitrogen balance

The effects of Ile and Val supplementation of a low-CP, corn-wheat-soybean meal-based piglet diet on growth performance, incidence of diarrhea, and N balance were studied using 60 Landrace x Duroc male piglets in a 4-wk experiment. The 60 individually caged piglets were divided into 5 dietary treatments, each consisting of 12 piglets. Diet 1 was a positive control diet (20% CP); diet 2 was a low-CP negative control diet (17% CP); diets 3, 4, and 5 were low-CP diets to which Ile, Val, or the combination of Ile and Val were added, respectively. All diets were supplemented with Lys, Met, Thr, and Trp to provide the required concentrations of these AA according to the 1998 NRC. Average daily gain and ADFI were similar among pigs fed the positive control, Val-added, and the Val plus Ile-added diets. On wk-2 and wk-4, fecal score was greater (softer feces) in piglets fed the 20% CP level compared with the remaining treatments (P < 0.01). Nitrogen intake was decreased (P < 0.0001) in pigs fed diets containing low levels of CP compared with pigs fed the 20% CP diet. Fecal N excretion (g/d) was decreased (P < 0.05) in piglets fed low-CP diets at wk 1 and wk 4 of feeding, and in urine at wk 4 of feeding. Crude protein levels or AA supplementation had no effect on N retention efficiencies. These results indicate that the supplementation of Val alone, or in combination with Ile, to a low-CP piglet diet with adequate levels of Lys, Met, Thr, and Trp is necessary to achieve maximum performance in pigs consuming corn-wheat-soybean meal-based diets.