Studies on the tryptophan requirement of lactating sows. Part 1: Estimation of the tryptophan requirement by performance

Mature sows were evenly assigned to six dietary treatments, which differed only in the concentration of total (apparent ileal digestible, AID) tryptophan (Trp) amounting per kg feed to 1.2 g (0.8 g) to 4.2 g (3.8 g) in diets 1-6. For a total of 72 lactations (28 days) sows' feed intake was measured daily and body weight was measured on day 110 of pregnancy and on days 1 and 28 of lactation. Litter size was standardized to 10-12 piglets within 1 week after farrowing. The piglets were weighed at days 1, 21 and 28. Milk yield was recorded by the weigh-suckle-weigh method on days 20 and 21. Concentrations of milk fat and protein were measured in manually drawn samples (days 20 and 21) by infrared spectroscopy. Average daily feed intake of the sows was 3.4, 4.7, 4.7, 6.1, 5.1 and 4.7 kg (diets 1-6 respectively, p < 0.001). Body weight losses of the sows during lactation were 30.8, 16.9, 19.2, 9.5, 14.1 and 13.1 kg (diets 1-6 respectively, p < 0.05). Milk output in the average of days 20 and 21 was 6840, 8192, 8362, 9035, 8618 and 8140 g/day, respectively (p < 0.01). There were no differences in milk fat or protein contents. Daily weight gain of the piglets in the average of lactation was 157, 184, 184, 187, 185 and 177 g, respectively (p < 0.10). Based on the results of this study the estimated Trp requirement of lactating sows for optimal performance was calculated with 1.9 g AID Trp/kg in the lactation diet (according to 2.0 g true ileal digestible Trp and approximately 2.6 g Trp on total basis).     

Tryptophan requirement of growing pigs at various body weights

The purpose of this study was to determine the tryptophan (Trp) requirement of growing pigs at different body weight (BW) ranges. Three performance experiments were conducted with female pigs in the BW ranges of 25-50, 50-80 and 80-115 kg. In addition to the performance experiments, nitrogen balance experiments were carried out in which pigs weighing 56, 66 and 86 kg were used. Trp-deficient basal diets were formulated to which varying amounts of l-Trp were added. The amino acid concentrations of the diets were analysed; concentrations of standardized digestible amino acids were calculated on the basis of tabular values. The calculated concentrations of standardized ileal digestible tryptophan were 0.81, 1.11, 1.41, 1.71, 2.01 g/kg diet in the lower BW range (25-50 kg), 0.71, 0.96, 1.21, 1.46, 1.71 g/kg diet in the middle BW range (50-80 kg), and 0.49, 0.69, 0.89, 1.09, 1.29 g/kg diet in the upper BW range (80-115 kg). Dose-response relationships were evaluated by means of an exponential regression model. In all three age ranges, performance parameters as well as nitrogen retention were strongly influenced by the dietary concentration of standardized ileal digestible tryptophan. According to the exponential model, in the 25-50 kg BW range, 95% of the maximum feed consumption, BW gain and nitrogen retention were achieved at concentrations between 1.96 and 2.00 g of standardized ileal digestible Trp per kilogram diet, corresponding to 3.32-3.39 g/day. In the BW range of 50-80 kg, 95% of the maximum of these parameters occurred at concentrations of standardized ileal digestible tryptophan in excess of the highest concentration of 1.71 g/kg diet, corresponding to 3.71 g/day. In the BW range of 80-115 kg, 95% of the maximum of BW gain and nitrogen retention were recorded at concentrations of 1.22 and 0.84 g standardized ileal digestible Trp per kilogram diet, corresponding to 3.77 and 2.25 g/day, respectively. Related to the energy value of the diets, the optimal concentration of standardized ileal digestible tryptophan are between 140 and 143 mg/MJ metabolizable energy (ME) in the BW range of 25-50 kg, in excess of 127 mg/MJ ME in the BW range of 50-80 kg and between 62 and 90 mg/MJ ME in the BW range of 80-115 kg. In conclusion, it is suggested that the requirement of standardized ileal digestible tryptophan for growing pigs might be higher than currently assumed.     

Performance of lactating sows in response to the dietary valine supply

In order to determine the requirement of lactating sows for valine (Val) the effects of graded Val supplementations on feed intake, milk yield and changes of body weight of sows and piglets were examined using 54 multiparous sows over a total of 72 lactations (35 days). The sows were randomly assigned to six treatments (1-6). Each group received the same basic diet, covering the requirements of energy and nutrients except Val (4.5 g native Val, i.e. 3.5 g apparent ileal digestible Val). Adding crystalline l-Val dietary Val concentrations of 5.5, 6.5, 8.5, 10.5 and 14.5 g/kg, respectively, were realized. Feed intake of the sows was determined daily, body weight was determined on day 110 of gestation and day 1, 22 and 35 of lactation. The piglets were weighed on day 1, 21 and 35. The intake of piglet feed, which was offered from day 21, was determined at day 35 for each litter. Milk yield was determined using the weigh-suckle-weigh-method at day 13, 14, 20 and 21, fat and protein contents were analysed in hand-milked samples with infrared spectroscopy. Feed intake (kg/day) of the sows during lactation averaged 2.9, 4.3, 4.6, 4.6, 4.9 and 5.1 for treatments 1-6, respectively. For treatments 1 and 2 body weight losses of the sows during lactation were higher (1207 and 805 g/day, respectively) and milk production was lower (7076 and 8686 g/day, respectively), compared with the average of treatments 3-6 (625 g/day body weight loss; 9263 g milk/day). Daily weight gain of the piglets was also lower (146 and 171 g/day vs. 200 g/day) leading to lower weaning weights of 6.6 and 7.5 vs. 8.5 kg. As a consistent growth depression of the piglets in Val deficiency must be assumed, at least 6.5 g Val corresponding to 5.5 g apparent ileal digestible Val per kg lactation feed must be recommended.     

True ileal digestible tryptophan to lysine ratios in ninety- to one hundred twenty-five-kilogram barrows

Three experiments were conducted to determine the optimal true ileal digestible (TID) Trp:Lys ratio for 90- to 125-kg barrows. Basal diets contained 0.55% TID Lys and were either corn-based (Exp. 1) or corn- and soybean meal-based (Exp. 2 and 3) diets supplemented with crystalline AA. In addition, each experiment contained a corn-soybean meal control diet. The number of pigs per pen progressively increased, with pigs housed in 2 (n = 82; initial and final BW of 88.5 and 113.6 kg, respectively), 7 (n = 210, initial and final BW of 91.2 and 123.3 kg, respectively), or 20 to 22 (n = 759; initial and final BW of 98.8 and 123.4 kg, respectively) pigs per pen for each successive experiment. Pigs in Exp. 1 were fed 6 incremental additions of L-Trp, equating to TID Trp:Lys ratios of 0.109, 0.145, 0.182, 0.218, 0.255, and 0.290. For the 28-d period, there was a quadratic improvement in G:F (P = 0.05) and ADG (P = 0.08) with increasing TID Trp:Lys, characterized by an improvement in performance of pigs fed the basal diet compared with those consuming diets with a 0.145 TID Trp:Lys ratio, with a plateau thereafter as TID Trp:Lys increased. Pigs fed the control diet had less increase in backfat depth than the average of pigs fed the titration diets (1.30 vs. 4.09 mm, respectively; P = 0.02), but pork quality was unaffected by dietary treatment. Pigs in Exp. 2 were fed 4 incremental additions of L-Trp, equating to TID Trp:Lys ratios of 0.130, 0.165, 0.200, and 0.235. Average daily gain and ADFI increased in a linear fashion with increasing TID Trp:Lys for the 29-d trial (P < 0.01), with quadratic improvements in d-29 BW (P = 0.06) and G:F (P = 0.05). Pigs fed the diet containing a TID Trp:Lys ratio of 0.165 had greater d-29 BW, ADG, G:F, and lower serum urea N concentration than pigs fed the basal diet (P < 0.05), but were similar to pigs fed TID Trp:Lys ratios of 0.200 and 0.235 for all criteria measured. In Exp. 3, TID Trp:Lys ratios of 0.13, 0.15, 0.17, 0.19, and 0.21 were evaluated. The response to increasing TID Trp:Lys was limited to a quadratic (P < 0.10) improvement in G:F with increasing TID Trp:Lys ratios. Maximum G:F was noted at a TID Trp:Lys ratio of 0.17. No relationship was noted between TID Trp:Lys and carcass characteristics. These experiments demonstrate that the minimum TID Trp:Lys ratio for pigs from 90 to 125 kg of BW is at least 0.145, but not greater than 0.17.     

True ileal amino acid digestibility and endogenous ileal amino acid losses in growing pigs fed wheat shorts- or casein-based diets

Use of dietary AA in growing pigs reflects digestion and use of digested AA for various body functions. Before evaluating dietary effects on use of digestible AA intake for body protein deposition, a digestibility study was conducted to investigate true ileal AA digestibility and endogenous ileal AA losses in growing pigs fed graded levels of wheat shorts (WS) or casein (CS; control). A casein-based basal diet (basal) was formulated to contain 0.27 g of standardized ileal digestible (SID) Lys per MJ of DE, to which extra Lys was added from WS (WS2, +0.10 g of SID Lys per MJ of DE; WS3, +0.20 g of SID Lys per MJ of DE) or casein (CS3, +0.20 g of SID Lys per MJ of DE). A fifth diet was formulated to be similar in CP level and source as CS3 but in which 6% pectin, a source of soluble non-starch polysaccharides (NSP), was included at the expense of cornstarch (CS3 + pectin). Five Yorkshire barrows (17.5 +/- 1.5 kg of BW) were fitted with a T-cannula at the distal ileum and randomly assigned to 1 of the 5 experimental diets in a 5 x 5 Latin Square design. Apparent ileal digestibility (AID), true ileal digestibility (TID), and endogenous ileal protein losses (EPL) were determined using the homoarginine method. Diet CS level did not influence (P > or = 0.10) TID of most essential AA or EPL (10.4 g/kg of DM intake). Including pectin in the diet did not influence TID of AA (P > or = 0.10) but increased EPL (15.6 g/kg of DM intake; P > or = 0.01). Inclusion of WS in the diet reduced TID of most essential AA (P < 0.01). The TID values for most essential AA, however, were the same (P > or = 0.10) for both dietary WS levels, except for Lys and Met, which were further reduced at the greatest dietary WS level. Increased EPL (P < 0.01) was only observed for WS3 (16 g/kg of DMI). We concluded that (1) the effects of dietary protein source on AID of AA can be attributed both to reduced TID of AA and increased EPL, (2) the impact of dietary WS level on TID of AA and EPL does not seem to be linear, (3) soluble NSP from pectin or WS exerts a greater effect on EPL than insoluble NSP, and (4) because of the metabolic cost associated with EPL and the impacts of feed composition on microbial fermentation in the gut lumen, the effects of feed ingredients on the use of ileal digestible AA for protein deposition should be investigated further.     

Digestible tryptophan requirements of starting, growing, and finishing pigs.

Seven hundred eight crossbred pigs were used in growth and digestion trials to determine the digestible tryptophan (Trp) requirement of starting (6 to 16 kg), growing (22 to 50 kg), and finishing (55 to 97 kg) pigs. Each growth trial evaluated a corn-fish meal-corn gluten meal basal diet, the basal diet with five incremental additions of L-Trp, and a control corn-soybean meal diet. The tryptophan content of the six incremental diets ranged from .13 to .255% for starting pigs, .08 to .18% for growing pigs, and .063 to .163% for finishing pigs. Lysine contents of basal diets were 1.38, .90, and .72% for starting, growing, and finishing diets, respectively. In all trials, ADG, ADFI, and gain/feed increased (P less than .001) linearly and quadratically as dietary Trp increased. Broken-line regression analyses determined the total dietary Trp requirements needed to optimize performance to be .19, .13, and .09% (as-fed basis) for starting, growing, and finishing pigs, respectively. These concentrations equated to Trp intakes of .96, 2.18, and 2.88 g/d. A digestion trial using growing pigs (29 kg initially) determined the apparent ileal digestibility of Trp in the basal starting and growing diets to be 72 and 70%, respectively; a similar trial with finishing pigs (55 kg initially) found 59% Trp digestibility for the basal finishing diet. Mean digestibility of L-Trp was 97%. Based on these values and the total Trp requirements given above, the digestible Trp requirements are .15, .10, and .06% for starting, growing, and finishing pigs, respectively.     

Nutritional requirement of digestible tryptophan for white-egg layers of 60 to 76 weeks of age

The objective of this study was to determine the nutritional requirement of digestible Trp for white egg layers in the period from 60 to 76 wk of age. A total of 180 Dekalb White layers with an average weight of 1,345 kg were distributed in a completely randomized design with 5 increasing levels of digestible Trp (0.167, 0.175, 0.183, 0.191, and 0.199%), 6 replicates, and 6 birds per experimental unit. The diets of the treatments contained 0.759% of digestible Lys, which was obtained using the prediction equation of the Brazilian Tables for Poultry and Swine, and each treatment consisted of a digestible Trp-to-Lys ratio of 22, 23, 24, 25, or 26%. The digestible Trp levels in the diet had a quadratic effect on egg production, egg mass, and conversion per mass and per dozen eggs, and a linear effect on egg weight. In conclusion, a diet with 0.192% digestible Trp, in a 25.33% ratio with digestible Lys or 212 mg/bird per day, can be recommended for white egg layers of 60 to 76 wk of age.     

Estimation of endogenous protein and amino acid ileal losses in weaned piglets by regression analysis using diets with graded levels of casein

Background： Many studies have investigated endogenous loss of proteins and amino acids （AAs） at the ileal level in growing pigs. However, only a few studies have researched this subject in piglets. Knowledge regarding AA ileal digestibility in piglets would be helpful during the formulation of diets for weaning piglets, rather than just using coefficients obtained in growing pigs. Therefore, in this study, we sought to estimate endogenous protein and AA ileal losses in piglets. Furthermore, apparent and true ileal digestibility （AID and TID） of protein and AAs from casein were measured. Results： The average flow of protein was 20.8 g/kg of dry matter intake （DMI）. Basal protein loss, as estimated by regression, was 16.9 g/kg DMI. Glutamic acid, arginine, and aspartic acid （2.2, 1.4, and 1.2 g/kg DMI, respectively） were the AAs for which greater losses were seen. The AID of protein and AAs increased as the protein level in the diet increased. A higher increment in AID was observed between diets with 80 and160 g CP/kg of feed; this finding was mainly attributable to increases in glycine and arginine （46.1% and 18%, respectively）. The TID of protein was 97.8, and the TID of AAs varied from 93.9 for histidine to 100.2 for phenylalanine. Conclusions： The basal endogenous protein loss in piglets was 16.9 g/kg DMI. Endogenous protein was rich in glutamic acid, aspartic acid, and arginine, which represented 32.7% of endogenous protein loss in weaning piglets. The TID of casein was high and varied from 93.0 for histidine to 100.2 for phenylalanine.     

Dietary lysine and threonine requirements of the pregnant sow estimated by nitrogen balance

Two experiments were conducted to determine the lysine and threonine requirements of gestating sows. In the first experiment, four levels of lysine (0.34,0.42,0.48, and 0.56% crude lysine, and 0.24,0.31, 0.38, and 0.45% standardized ileal digestible lysine) were compared in eight multiparous Large White sows. Each sow received successively the four diets according to a Latin-square experimental design. Nitrogen balance was measured over 11 d after a 10-d period of adaptation to the experimental diet. In the second experiment, four threonine/lysine ratios (0.63, 0.73, 0.80, and 0.89 on a crude basis and 0.61, 0.71, 0.77, and 0.87 on a standardized ileal digestible amino acid basis) were compared in 16 multiparous sows, according to a Latin-square experimental design. The standardized ileal digestibility of amino acids in the experimental diets was determined with ileo-rectal anastomized growing pigs. In the first experiment, nitrogen retention was affected by lysine supply (linear, P < 0.001; quadratic, P < 0.04). Nitrogen retention was lowest for treatment 1 (8.0 g/ d) and highest for treatments 3 and 4 that did not differ. Nitrogen retention plateaued at 14.7 g/d in sows consuming 10.5 g/d of digestible lysine. The maintenance requirement for digestible lysine was calculated to be 27 mg/kg BW(0.75) with an efficiency of utilization of digestible lysine above maintenance at 59%. In the second experiment, nitrogen retention was affected (P < 0.03) by the threonine:lysine ratio. It was lower for the lowest threonine:lysine ratio (0.63) than for the other three treatments that did not differ among each other. These results indicate that the optimal standardized digestible threonine:lysine ratio appears to be about 0.71 for multiparous gestating sows.     

Valine requirement of nursery pigs

Six experiments were conducted to determine the true digestible valine requirement of 5- to 20-kg pigs. In Exp. 1, a valine-deficient diet for 5- to 10-kg pigs was developed and validated in terms of growth performance in response to supplemental L-valine. A different basal diet was validated for 10- to 20-kg pigs in Exp. 2. Both diets were demonstrated to be deficient in valine and to support performance equivalent to typical nursery diets when fortified with L-valine. In Exp. 3, true ileal digestibility of valine in the two basal diets was determined in eight pigs fitted with a simple T-cannula at the terminal ileum. Another four pigs received an enzymatically hydrolyzed casein-based diet to determine endogenous contributions to collected ileal digesta. The two diets were found to have true valine digestibilities of 82% (5- to 10-kg pigs) and 86% (10- to 20-kg pigs). In Exp. 4, 80 weaned pigs (5.8 kg) were offered the basal diet fortified with five incremental doses (0.08%) of L-valine. Weight gain increased quadratically (P < 0.05) with increasing levels of valine. Broken-line analysis revealed a true digestible valine requirement of 0.86 +/- 0.03%. In Exp. 5, the true digestible valine requirement of 10- to 20-kg pigs was estimated with 120 pigs (10.9 kg) using the second basal diet fortified with six incremental doses (0.05%) of L-valine. The data suggested a digestible valine requirement level of about 0.775%, which was reevaluated in Exp. 6, wherein pigs did not respond to levels of digestible valine higher than 0.775%. In conclusion, requirement estimates were 2.50 and 2.22 g of true digestible valine per megacalorie of ME for 5- to 10- and 10- to 20-kg pigs, respectively. These empirical estimates are in close agreement with recent estimates of the National Research Council Subcommittee on Swine Nutrition of 2.48 and 2.11 g of true digestible valine per megacalorie of ME, respectively.     

Threonine and tryptophan ratios fed to nursery pigs*

The optimal ratio of tryptophan (Trp):lysine (Lys) relative to the ratio of threonine (Thr):Lys was studied in 288 crossbred (Cambrough 15 x Canabrid) nursery pigs from 7.1 to 15.6 kg BW. Treatments were arranged in a 3 x 3 factorial with three calculated ratios of true digestible Thr:Lys (0.55, 0.60, or 0.65) in combination with three Trp:Lys ratios (0.145, 0.170, or 0.195). Treatments were replicated with eight pens of four pigs each. The experiment lasted 28 day with Phase II (222.6 g CP and 11.9 g true digestible Lys/kg diet, initially 24 day of age and 7.1 kg BW) and Phase III (196.2 g CP and 10.1 kg true digestible Lys/kg diet, initially 38 day of age and 9.8 kg BW) diets each fed for 14 day. Threonine by Trp interactions were observed for average daily gain during each period, and for daily feed intake during Phase III and overall. Generally, Trp addition linearly increased gain and feed intake at a Thr:Lys ratio of 0.60 and 0.65 but not at a Thr:Lys ratio of 0.55. Gain:feed was increased linearly with increasing levels of Trp during both periods. There were no main effects of Thr in either time period or overall. Overall, optimal performance was obtained in pigs fed the true digestible Trp:Lys ratio of 0.195 at Thr:Lys ratios 0.60 or 0.65. These results indicate that Trp:Lys ratios above 0.195 may be needed to maximize performance in diets containing wheat and barley.     

Performance of sows fed high levels of nonstarch polysaccharides during gestation and lactation over three parities

The effect of feeding sows a starch diet or a diet with a high level of nonstarch polysaccharides (NSP) during gestation, lactation, or both gestation and lactation during the first three parities on reproductive performance, body weight, and backfat was studied. Four-hundred and forty-four postpuberal gilts were allotted to a 2 x 2 x 2 factorial experiment. Treatments were diet composition during gestation (including the weaning-to-estrus interval; G-Starch: 274 g/kg of starch and 123 g/kg of fermentable NSP or G-NSP: 86 g/kg of starch and 300 g/kg of fermentable NSP), diet composition during lactation (L-Starch: 293 g/kg of starch and 113 g/kg of fermentable NSP or L-NSP: 189 g/kg of starch and 216 g/kg of fermentable NSP) and group-housing system during gestation (free access stalls or electronic feeding). Both gestation diets were formulated to be isoenergetic. During lactation, sows were given free access to the lactation diets from d 6 after parturition onwards. Body weight and backfat gains during gestation were lower in sows fed the G-NSP diet than in those fed the G-starch diet (P < 0.001). The effects were more pronounced in the electronic feeding system than in the free access stalls. These results indicate an overestimation of the energy value of fermentable NSP. Body weight and backfat losses during lactation were less in sows fed the G-NSP diet during gestation than in those fed the G-starch diet (P < 0.05),which can be explained by a 0.4 kg/d higher (P < 0.001) feed intake during lactation of the sows fed the G-NSP diet. Sows fed the L-NSP diet lost more backfat during lactation than sows fed the L-starch diet (P < 0.05). The number of total piglets born and live-born piglets was 0.5 piglet higher in sows fed the G-NSP diet than in those fed the G-starch diet (P < 0.05). Lactation diet did not affect the number of total piglets born or live-born piglets. This study shows that, although high NSP diets negatively influence body weight and backfat thickness of the sows, it is possible to feed sows a diet with a high level of fermentable NSP diet during both gestation and lactation without negative effects on reproductive performance. Under the conditions of this study, feeding sows a diet with a high level of fermentable NSP during gestation and a high level of starch during lactation seems the most favorable feeding strategy.     

Energy balance of lactating primiparous sows as affected by feeding level and dietary energy source

The effects of feeding level and major dietary energy source used during lactation on sow milk composition, piglet body composition, and energy balance of sows were determined. During a 21-d lactation, 48 primiparous sows were fed either a Fat-rich (134.9 g/kg fat; 196.8 g/kg carbohydrate) or a Starch-rich (33.2 g/kg fat; 380.9 g/kg carbohydrate) diet at either a High (44 MJ NE/d; 1,050 g protein/d) or a Low (33 MJ NE/d; 790 g protein/d) feeding level. Within each feeding level, the two diets were fed to provide an isocaloric and isonitrogenous intake. At the Low feeding level, no differences in milk production, milk composition, or piglet body composition were found as a result of feeding the two dietary energy sources. However, at the High feeding level, sows fed the Fat-rich diet produced higher milk fat (8.4 vs 6.9%) and milk energy (5.38 vs 4.77 kJ/g) concentrations and a higher piglet body fat concentration (152.1 vs 135.4 g/kg) than sows fed the Starch-rich diet. At the Low feeding level, the energy balance (d 6 to d 20) of the sows was similar when fed either the Fat- or the Starch-rich diet (-558 and -515 kJ x BW(-.75) x d(-1)), but at the High feeding level, the energy balance was more negative in sows fed the Fat than those fed the Starch-rich diet (-544 vs -372 kJ x BW(-.75) x d(-1)). This suggests that at the High feeding level, dietary energy in the form of fat is preferentially used for milk fat synthesis, resulting in growth and in fatter piglets. Alternatively, at the High feeding level, Starch as the major energy source is used only for growth of the piglets, as confirmed by protein deposition, and also results in a less-negative energy balance for the sows. From this experiment, it can be concluded that effects of substituting cornstarch for fat in the diet of lactating sows on milk composition, piglet body composition, and energy balance of the sows are dependent on feeding level.     

Effect of nutrient intake in lactation on sow performance: determining the threonine requirement of the high-producing lactating sow

Reproductive performance is steadily increasing within the pork industry; logically, amino acid requirements need to be redefined for sows producing larger litters. The objective of this study was to determine the threonine requirement of the high-producing lactating sow and to determine the effect of lysine on this requirement. A total of 419 PIC C-15 sows were assigned randomly to treatment within parity groups (1, 2, and 3+) and gestation treatment at d 110 of gestation. Lactation diets were formulated to contain 0.80% total lysine (tLYS) with 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, or 0.65% total threonine (tTHR) or 1.06% tLYS with 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, or 0.70% tTHR. Litters were standardized to a minimum of 11 piglets within 48 h after farrowing, and sows had free access to feed throughout lactation (lactation length = 20.1 +/- 0.1 d). Sow ADFI exceeded expectation, averaging 6.90, 7.40, and 7.20 kg/d for Parities 1, 2, and 3+, respectively. Daily tLYS intake was 58 g/d (47 g of apparent ileal digestible lysine [dLYS] per day) and 74 g/d (59 g dLYS/d) for the low- and high-lysine group, respectively. Lysine intake did not affect sow or litter performance (P > 0.10). Sows gained an average of 4.8 kg in lactation. Using regression analysis, BW gain was maximized at 0.54% tTHR for all parity groups (quadratic; P < 0.05). Litter weaning weight (67.1, 67.9, and 66.2 kg for Parities 1, 2, and 3+, respectively) and litter weight gain (2.49, 2.53, and 2.44 kg/d for Parities 1, 2, and 3+, respectively) were maximized at 0.53% tTHR using regression analysis, for all parity groups (quadratic; P < 0.05). Based on regression analysis, plasma urea nitrogen on d 10 and 18 was minimized at 0.54% tTHR (P < 0.05). Lysine levels in excess of 58 g of tLYS/d did not benefit sow or litter performance. The requirement for threonine to minimize sow tissue mobilization was 37, 40, and 38 g tTHR/d (28, 30, and 30 g of apparent ileal digestible threonine [dTHR] per day) for Parities 1, 2, and 3+ sows, respectively. The threonine required to maximize litter performance was 36, 39, and 38 g of tTHR/d (28, 30, and 29 g of dTHR/d) for Parities 1, 2, and 3+ sows, respectively. Alternatively, the requirement can be expressed as 14.3 g tTHR (11.8 g dTHR) per kilogram of litter gain.     

The tryptophan requirement of growing and finishing barrows

Five experiments were conducted to determine the true ileal digestible Trp (tidTrp) requirement of growing and finishing pigs fed diets (as-fed basis) containing 0.87% (Exp. 3), 0.70% (Exp. 4), 0.61% (Exp. 5), and 0.52% (Exp. 1 and 2) tidLys during the early-grower, late-grower, early-finisher, and late-finisher periods, respectively. Treatments were replicated with three or four replications, with three or four pigs per replicate pen. Treatment differences were considered significant at P = 0.10. Experiment 1 was conducted with 27 pigs (initial and final BW of 78.3 +/- 0.5 and 109.8 +/- 1.9 kg) to validate whether a corn-feather meal (FM) tidTrp-deficient (0.07%) diet, when supplemented with 0.07% crystalline l-Trp, would result in growth performance and carcass traits similar to a conventional corn-soybean meal (C-SBM) diet. Pigs fed the corn-FM diet without Trp supplementation had decreased growth performance and carcass traits, and increased plasma urea N (PUN) concentration. Supplementing the corn-FM diet with Trp resulted in greater ADG and G:F than pigs fed the positive control C-SBM diet. Pigs fed the corn-FM diet had similar carcass traits as pigs fed the C-SBM diet, but loin muscle area was decreased and fat thickness was increased. In Exp. 2, 60 pigs (initial and final BW of 74.6 +/- 0.50 and 104.5 +/- 1.64 kg) were used to estimate the tidTrp requirement of finishing pigs. The levels of tidTrp used in Exp. 2 were 0.06, 0.08, 0.10, 0.12, or 0.14% (as-fed basis). Response variables were growth performance, PUN concentrations, and carcass traits and quality. For Exp. 2, the average of the estimates calculated by broken-line regression was 0.104% tidTrp. In Exp. 3, 4, and 5, barrows (n = 60, 60, or 80, respectively) were allotted to five dietary treatments supplemented with crystalline l-Trp at increments of 0.02%. The basal diets contained 0.13, 0.09, and 0.07% tidTrp (as-fed basis) in Exp. 3, 4, and 5, and initial BW of the pigs in these experiments were 30.9 +/- 0.7, 51.3 +/- 1.1, and 69.4 +/- 3.0 kg, respectively. The response variable was PUN, and the basal diet used in Exp. 3 and 4 contained corn, SBM, and Canadian field peas. The tidTrp requirements were estimated to be 0.167% for pigs weighing 30.9 kg, 0.134% for pigs weighing 51.3 kg, and 0.096% for pigs weighing 69.4 kg. Based on our data and a summary of the cited literature, we suggest the following total Trp and tidTrp requirement estimates (as-fed basis): 30-kg pigs, 0.21 and 0.18%; 50-kg pigs, 0.17 and 0.14%; 70-kg pigs, 0.13 and 0.11%; and in 90-kg pigs, 0.13 and 0.11%.     

Effects of dietary arginine supplementation during gestation and lactation on the performance of lactating primiparous sows and nursing piglets

A 2 x 2 factorial arrangement of treatments in a randomized block design was used to determine the effects of dietary Arg supplementation during gestation and lactation on the lactation performance of 38 first-parity sows. At 30 d of gestation, pregnant gilts were allotted based on BW to 1 of 2 diets supplemented with 1% L-Arg.HCl or 1.7% L-Ala (isonitrogenous control). After farrowing, sows were further allotted based on BW within previous gestation treatment groups to 1 of 2 lactation diets supplemented with 1% L-Arg.HCl or 1.7% L-Ala (isonitrogenous control). All gestation diets contained 3.1 Mcal/kg and 12.2% CP (as is) and were fed 2 kg/d in 2 equally sized meals, whereas all lactation diets contained 3.2 Mcal/kg and 18.6% CP (as is) and were fed ad libitum. Litter size was standardized to 10 piglets by cross-fostering within 24 h postfarrowing. On a weekly basis, BW and backfat (BF) thickness of sows, as well as piglet BW were measured, and blood and milk samples were obtained from the sows. Number of days from weaning to estrus and ADFI were also recorded. There were no differences in BW, BF thickness, ADFI, or days until return to estrus among treatment groups. There was no effect of the gestation diet or a gestation x lactation diet interaction on any parameter measured. On d 7 of lactation, plasma concentrations of Arg and insulin in sows, as well as concentrations of most AA in milk, were greater (P < 0.05) in response to Arg supplementation during lactation compared with the control. Weight gain of piglets from sows fed the Arg-supplemented diet during lactation was greater between d 0 and 7 (P < 0.01) and between d 0 and 21 (P < 0.05) of lactation compared with piglets from sows fed the control diet. Collectively, results from this study indicate the potential beneficial effects of dietary Arg supplementation in improving the lactation performance of first-parity sows.     

Estimation of endogenous protein and amino acid ileal losses in weaned piglets by regression analysis using diets with graded levels of casein

Background

Many studies have investigated endogenous loss of proteins and amino acids (AAs) at the ileal level in growing pigs. However, only a few studies have researched this subject in piglets. Knowledge regarding AA ileal digestibility in piglets would be helpful during the formulation of diets for weaning piglets, rather than just using coefficients obtained in growing pigs. Therefore, in this study, we sought to estimate endogenous protein and AA ileal losses in piglets. Furthermore, apparent and true ileal digestibility (AID and TID) of protein and AAs from casein were measured.

Results

The average flow of protein was 20.8 g/kg of dry matter intake (DMI). Basal protein loss, as estimated by regression, was 16.9 g/kg DMI. Glutamic acid, arginine, and aspartic acid (2.2, 1.4, and 1.2 g/kg DMI, respectively) were the AAs for which greater losses were seen. The AID of protein and AAs increased as the protein level in the diet increased. A higher increment in AID was observed between diets with 80 and160 g CP/kg of feed; this finding was mainly attributable to increases in glycine and arginine (46.1% and 18%, respectively). The TID of protein was 97.8, and the TID of AAs varied from 93.9 for histidine to 100.2 for phenylalanine.

Conclusions

The basal endogenous protein loss in piglets was 16.9 g/kg DMI. Endogenous protein was rich in glutamic acid, aspartic acid, and arginine, which represented 32.7% of endogenous protein loss in weaning piglets. The TID of casein was high and varied from 93.0 for histidine to 100.2 for phenylalanine.     

Apparent and standardized ileal digestibilities of amino acids for pigs fed corn- and soybean meal-based diets at varying crude protein levels

The objective of this study was to determine the effect of CP level in corn- and soybean meal-based diets on apparent (AID) and standardized ileal digestibility (SID) of AA. Six pigs (initial BW, 47.1 ± 1.0 kg) fitted with T-cannula at the distal ileum were fed 6 diets for 6 periods in a 6 × 6 Latin square design. The 6 diets consisted of a nitrogen-free diet and 5 corn- and soybean meal-based diets that contained CP of 68, 105, 141, 177, and 214 g/kg. Each period consisted of a 5-d adjustment period and 2 d of ileal digesta collection for 10 h on each of d 6 and 7. The ratio of corn:soybean meal was fixed at 3 to 2 by weight and cornstarch was added to dilute the CP concentration. Chromic oxide was added at 5 g/kg as an indigestible marker. The results showed basal endogenous loss ranged from 65 mg/kg of DMI for Met to 3,104 mg/kg of DMI for Pro. Proline and Gly (1,053 mg/kg of DMI) were the 2 most abundant AA in endogenous flow and together accounted for approximately 43% of the total endogenous AA flow. Of the basal ileal endogenous CP, total AA accounted for 82%. The AID were 80.9 to 84.7%, 85.1 to 87.4%, 72.9 to 79.5%, and 86.5 to 87.9% for Lys, Met, Thr, and Trp, respectively, with corresponding SID being 86.6 to 89.0%, 87.5 to 90.5%, 82.7 to 88.2%, and 90.2 to 94.6%, respectively, as dietary CP increased from 68 to 214 g/kg. There were linear increases in AID of N, Arg, Gly, Ile, Lys, Ser, Thr, Tyr, and Val (P ≤ 0.05) as CP increased and linear decreases in SID of N and all AA measured in this study except Lys, Met, and Pro (P ≤ 0.05). Both linear and quadratic effects were observed in AID for Pro (P < 0.05). In conclusion, the protein content of corn-soybean meal diets evaluated in the current study affected SID of most indispensable and dispensable AA, excluding Lys, Met, and Pro.     

The tryptophan requirement of nursery pigs

Five experiments were conducted to determine the true digestible Trp (dTrp) requirement of nursery pigs. Treatments were replicated with four or five pens of five or six pigs each. Pigs were weaned at 21 (Exp. 1, 2, and 5) or 19 d (Exp. 3 and 4), and fed common diets for various times and then experimental diets for 8 (Exp. 1), 13 (Exp. 2 and 3), or 14 d (Exp. 4 and 5). Experiment 1 (160 pigs, initial and final BW of 8.4 and 11.4 kg) evaluated six protein sources low in Trp relative to a positive control diet to identify the protein source to be used in subsequent experiments. The results indicated that a diet with Canadian field peas (CFP) supplemented with Trp resulted in ADG, ADFI, and gain:feed (GF) equal to (P > 0.10) the positive control diet. In Exp. 2, 75 pigs (initial and final BW of 13.2 and 19.2 kg) were fed 1) Trp-deficient diet (0.13% dTrp) with CFP, 2) Diet 1 with added Trp (0.23% dTrp), or 3) positive control diet (0.22% dTrp). Daily gain, ADFI, and GF were decreased (P < 0.01) in pigs fed Diet 1 compared with pigs fed Diets 2 and 3, but ADG, ADFI, and GF were equal (P > 0.10) in pigs fed Diets 2 and 3. Experiments 3 (180 pigs, initial and final BW of 5.2 and 7.3 kg), 4 (120 pigs, initial and final BW of 6.3 and 10.2 kg), and 5 (144 pigs, initial and final BW of 10.3 and 15.7 kg) were conducted to estimate the dTrp requirement of nursery pigs with diets using CFP as a primary protein source. The diets used in Exp. 3, 4, and 5 contained 1.35, 1.19, or 1.01% dLys, respectively, and other amino acids were provided at 105% the ratio relative to Lys. Response variables were ADG, ADFI, GF, and plasma urea N concentrations, and data were analyzed using the broken-line model. The levels of dTrp in the diets for Exp. 3 (Phase I, 5.2 to 7.3 kg) were 0.14, 0.17, 0.20, 0.23, 0.26, and 0.29%. The average dTrp requirement was estimated to be 0.21% (0.24% total Trp). The levels of dTrp in the diets for Exp. 4 (Phase II, 6.3 to 10.2 kg) were 0.13, 0.16, 0.19, 0.22, 0.25, and 0.28%. The average dTrp requirement was estimated to be 0.20% (0.23% total Trp). The levels of dTrp in the diets for Exp. 5 (Phase III, 10.3 to 15.7 kg) were 0.130, 0.155, 0.180, 0.205, 0.230, and 0.255%. The average dTrp requirement was estimated to be 0.18% (0.22% total Trp). These results indicate that the true dTrp requirement is 0.21, 0.20, and 0.18% for Phase I (5.2 to 7.3 kg), II (6.3 to 10.2 kg), and III (10.3 to 15.7 kg) nursery pigs, respectively.     

Effects of tryptophan supplementation on aggression among group-housed gestating sows

The objective of this study was to determine the effects of dietary Trp supplementation on mixing-induced aggression and the associated stress, and on reproductive performance in gestating sows. After weaning, sows were mixed in pens with electronic sow feeders on concrete-slatted floors. Each pen housed 21 ± 2.8 sows, with approximately 2.7 ± 0.43 m(2)/sow of floor space allowance. Multiparous sows (n = 168) from 8 breeding groups were used, with 4 groups assigned to a control diet and 4 groups assigned to a high-Trp diet. Control sows received corn- and soybean meal-based diets throughout gestation (0.15% Trp) and lactation (0.21% Trp). Three days before and after mixing, sows assigned to the high-Trp treatment received approximately 2.3 times the dietary Trp (0.35% in the gestation diet and 0.48% in the lactation diet) fed to control sows. Six focal sows (2 sows from each of parity 1, 2, and 3 or greater) in each pen were designated and videotaped for 72 h after mixing to determine the type and number of aggressive interactions among sows. Before and 48 h after mixing, saliva samples were collected from focal sows, and scratches were assessed on all sows. Data were analyzed using the FREQ and GLIMMIX procedures (SAS Inst. Inc., Cary, NC). Aggression among sows was intense during the initial 6 h and decreased between 6 and 72 h after mixing. The initial aggression caused scratches and increased cortisol concentrations (P < 0.05). Mature sows tended to fight for longer periods (112 vs. 52 s/h per sow, SE = 23.8; P < 0.10) but had fewer scratches caused by aggression (injury score = 4.3 vs. 6.5, SE = 1.13; P < 0.01) than parity-1 sows. Supplementation of dietary Trp reduced the total duration of head-to-head knocking (P < 0.05) but did not affect other aggressive behaviors. There was no difference between dietary treatments in injury scores or saliva cortisol concentrations. Sows in the high-Trp treatment had more total piglets born (12.5 vs. 10.5 pigs/litter, SE = 0.55; P < 0.05) and more stillborn piglets (1.5 vs. 0.8 pigs/litter, SE = 0.20; P < 0.05), but had no significant change (P = 0.12) in piglets born alive (10.8 vs. 9.7 pigs/litter, SE = 0.42) compared with control sows. The results indicate that the initial aggression after mixing caused more injuries in young sows than in mature sows. Supplementation of dietary Trp at 2.3 times the control amount for a short period did not effectively reduce aggression and the associated stress in sows at mixing.