Variability in mixing efficiency and laboratory analyses of a common diet mixed at 25 experiment stations.

An experiment involving 25 experiment stations in the North Central and Southern regions (NCR-42 and S-288, respectively) was conducted to assess the degree of uniformity of diet mixing among stations and to assess the variability among station laboratories in chemical analysis of mixed diets. A fortified corn-soybean meal diet was mixed at each station using a common diet formula (except for vitamin and trace-mineral additions). The diet was calculated to contain 14% crude protein (CP), 0.65% Ca, 0.50% P, and 125 ppm Zn (based on 100 ppm added Zn). After mixing, samples were collected from the initial 5% of feed discharged from the mixer, after 25, 50, and 75% was discharged, and from the final 5% of discharged feed. The five samples were sent to the University of Kentucky, finely ground, and divided into subsamples. Each set of five subsamples from each station was distributed to three randomly selected stations for analysis of CP, Ca, P, and Zn (i.e., each station analyzed five diet sub-samples from three other stations). In addition, two commercial and two station laboratories analyzed composites of the five subsamples from each of the 25 mixed diets. Based on the laboratories that analyzed all diets, means were 13.5, 0.65, and 0.52%, and 115 ppm for CP, Ca, P, and Zn, respectively. Ranges of 11.8 to 14.6% CP, 0.52 to 0.85% Ca, 0.47 to 0.58% P, and 71 to 182 ppm of Zn were found among the 25 diet mixes. The coefficients of variation among the 25 diet samples for CP, Ca, P, and Zn were 4.3, 9.3, 4.1, and 17.4%, and among the 25 laboratories were 3.6, 12.5, 10.7, and 11.1%, respectively. Overall analyses of the five sub samples were, respectively, CP: 13.4, 13.6, 13.4, 13.5, and 13.4% (P < 0.06); Ca: 0.66, 0.67, 0.67, 0.66, and 0.67%; P: 0.50,0.51,0.51,0.50, and 0.50%; and Zn: 115, 116, 112, 113, and 120 ppm (P < 0.001). Diets were not uniformly mixed at all stations (station x sample No. was P < 0.08 for Ca and P < 0.01 for CP, P, and Zn). Among stations, the range of the five samples, expressed as a percentage of the mean and averaged for CP, Ca, P, and Zn, varied from +/- 1.1% (i.e., 98.9 to 101.0%) to +/- 12.9% (84.6 to 110.4%), with an overall average of +/- 5.2%. Neither type nor volume of mixers was related to mixing uniformity. The results suggest that uniformity of diet mixes varies among experiment stations, that some stations miss their targeted levels of nutrients (especially Zn), and that the variability among experiment station laboratories in analysis of dietary Ca, P, and Zn in mixed diets is quite large.

Effect of nipple drinker water flow rate and season on performance of lactating swine.

A cooperative study involving six experiment stations and 236 crossbred litters was conducted to determine the effect of nominal nipple drinker water flows of 700 mL/min and 70 mL/min (actual = 701 and 76 mL/min, respectively) during winter (November through February; 124 litters) and summer (June through August; 112 litters) seasons on performance of lactating sows and their litters. Within a season, sows were paired according to expected farrowing date and assigned at random to crates. Water flow rate treatments were assigned at random to sows within pairs. Sows were housed in farrowing crates from d 109 of gestation until either d 21 (two stations) or d 28 of lactation (four stations). Within 24 h after farrowing, litters were adjusted to contain 8 to 12 piglets. Sow feed intake (SFI) and litter weight (LW) were recorded weekly. Sow weights were recorded at d 109 of gestation, d 0, and d 21 of lactation. Sows lactating beyond 21 d were also weighed on d 28. Analysis of covariance was applied to sow weight change, average daily SFI, and LW data where litter size after crossfostering was the covariate. Average ambient temperature 30 cm above the floor at 0830 and 1600 was 24.6 +/- 0.15 degrees C and 29.4 +/- 0.14 degrees C, respectively, during summer and 20.7 +/-0.13 degrees C and 21.8 +/- 0.11 degrees C during winter trials. Restricted drinker water flow rate decreased SFI (P < 0.01; 4.59 vs. 3.94 kg/d, respectively, for 700 and 70 mL/min) and increased BW loss (P < 0.01; 0.56 vs 0.89 kg/d, respectively for 700 and 70 mL/min) but did not affect litter size (P > 0.87) or LW (P > 0.89) during the first 21 d of lactation. During d 22 to 28, the 70 mL/min flow decreased SFI (P < 0.01; 5.02 vs. 4.47 kg/d respectively, for 700 and 70 mL/min). Over the 21-d lactation period, the 70 mL/min treatment depressed (P < 0.01) SFI more during the winter (5.12 vs. 4.24 kg/d for 700 and 70 mL/ min, respectively) than during the summer (4.05 vs 3.65 kg/d for 700 and 70 mL/min, respectively). Season affected SFI (P < 0.01; 4.68 vs. 3.85 kg/d, respectively, for winter and summer), sow weight loss (P < 0.001; 0.46 vs 0.83 kg/d, respectively, for winter and summer), and LW at 21 d (P < 0.05; 52.8 vs. 49.6 kg, respectively, for winter and summer) but not (P > 0.96) the number of pigs per litter. Results of this study suggest that ample access to drinking water and controlling ambient temperature during summer months are essential for sow and litter performance.

Growth promotion effects and plasma changes from feeding high dietary concentrations of zinc and copper to weanling pigs (regional study).

An experiment was conducted to determine the effect of high dietary intakes of Zn and Cu and their combination on growth performance of weanling pigs with diverse health status and management strategies. Twelve experiment stations cooperated and used a total of 1,356 pigs that averaged 6.55 kg BW and 22.2 d age at weaning. The four dietary treatments, all of which met or exceeded NRC requirements, were 1) control, 2) 3,000 ppm Zn (from Zn oxide), 3) 250 Cu ppm (from Cu sulfate), or 4) 3,000 ppm Zn and 250 ppm Cu. The diets were fed as a complex Phase I diet (1.4% lysine) for 7 d followed by a Phase II diet (1.2% lysine) for 21 d. Chlortetracycline (220 ppm) was added to all diets. Fecal color (1 = yellow to 5 = black) and consistency (1 = very firm to 5 = very watery) were scored daily for 3 wk. At the end of the 28-d study, 412 pigs were bled at five stations, and plasma Cu, Zn, and Fe concentrations were determined at one station with atomic absorption spectrophotometry. Average daily gain (375, 422, 409, 415 g/d), feed intake (637, 690, 671, 681 g/d), and gain/feed (586, 611, 611, 612 g/kg) were improved (P < .01) by the addition of Zn and(or) Cu. Significant Cu x Zn interactions imply that the responses to Zn and Cu were independent and not additive. There were significant (P < .01) Zn and Cu effects and a Zn x Cu interaction on fecal color (3.17, 3.24, 4.32, 3.57) and consistency (2.39, 2.14, 2.14, 2.13). Dietary additions of Cu and Zn resulted in elevated plasma concentrations of Cu and Zn, respectively. These data indicate that pharmacological additions of 3,000 ppm Zn (oxide) or 250 ppm Cu (sulfate) stimulate growth beyond that derived from intakes of Zn and Cu that meet nutrient requirements. However, the combination of Zn and Cu did not result in an additive growth response.

Effect of room temperature and dietary amino acid concentration on performance of lactating sows. NCR-89 Committee on Swine Management.

Mixed-parity sows (n = 267) from five research stations were used to investigate whether a reduction of excess dietary amino acids would improve feed intake and performance of lactating sows experiencing heat stress. Experimental treatments included effects of room temperature (warm or hot) and diet (adequate protein [AP] or low protein [LP]). The corn-soybean meal AP diet was formulated to contain 16.5% CP, .8% lysine, and .67% digestible lysine. The LP diet was formulated to contain 13.7% CP, .76% lysine, and .66% digestible lysine using corn, soybean meal, and synthetic lysine. Feed intake during gestation was standardized at 1.8 kg x sow(-1) x d(-1). At parturition, litter size was adjusted to no fewer than nine pigs. Mean high temperature in the warm and hot rooms was 20.4 and 29.2 degrees C and mean low temperature was 17.7 and 27.1 degrees C, respectively. The hot environment reduced (P < .01) feed intake of sows (4.19 vs 6.38 kg/d) during lactation, weaning weight of sows (176.2 vs 193.6 kg), percentage of sows displaying estrus (79.2 vs 93.4%) by d 15 postweaning, and litter growth rate (1.74 vs 2.11 kg/d) and increased (P < .01) respiration rate of sows on d 10 postpartum (71.9 vs 36.5 breaths/min) compared with the warm environment. Litter size and backfat loss of sows were not affected by treatments. No significant diet x room temperature interactions were observed for voluntary feed intake, body weight loss, backfat loss, or respiration rate of sows. Litter growth rate was depressed by feeding the LP diet in the warm room but was improved by feeding the LP diet in the hot room (warm-AP, 2.17; warm-LP, 2.05; hot-AP, 1.71; hot-LP, 1.77 kg/d; P < .05). Reduction of dietary crude protein combined with supplementation of crystalline lysine to reduce concentrations of excess dietary amino acids did not significantly reduce heat stress of sows, but it did support slight improvements in weight gain of litters nursing heat-stressed sows.

Characterization of muscles from boars, barrows, and gilts slaughtered at 100 or 110 kilograms: differences in fat, moisture, color, water-holding capacity, and collagen.

For characterization of ether-extractable fat content (EE), L*, a*, and b* color, and water-holding capacity (WHC), 12 muscles or muscle groups were dissected from 48 pork carcasses of boars, barrows, or gilts that were fed diets either at minimum (LO) or 1% above (HI) their protein requirements and slaughtered in two separate trials at 100 or 110 kg. In both trials across muscles, gilts and boars had lower (P < .05) EE than barrows. In the 110-kg trial, boars had lower (P < .001) EE than gilts. In the 100-kg trial, boars on LO diets had lower (P < .001) WHC than all other groups, and both boar groups had lower (P < .05) WHC than gilts. No differences (P > .05) in WHC were seen in the 110-kg trial. In the 100-kg trial, gilts had lower L* (P < .05) than boars and barrows, but in the 110-kg trial boars had lower L* (P < .05) than barrows and gilts. The lowest (P < .05) a* values were for boars in the 100-kg trial and for boars on LO diets in the 110-kg trial. In both trials, the serratus ventralis had more (P < .001) EE than all other muscles. In both trials, the semitendinosus had higher (P < .001) L* and the longissimus had lower (P < .01) a* and b* than all other muscles. The numerous differences observed among muscles may help identify optimal uses for the entire pork carcass.

Sensory characteristics and carcass traits of boars, barrows, and gilts fed high- or adequate-protein diets and slaughtered at 100 or 110 kilograms.

The objective of this study was to determine consumer reaction to boar (BO), barrow (BA), and gilt (G) meat from pigs grown and finished on high- (HI) and low- (LO) protein diets and slaughtered at 100 and 110 kg BW. Within each of two trials, 54 BO, BA, and G were allotted within sexes to HI or LO protein sequences for growing and finishing: 19 and 17% (BOHI), 18 and 16% (BOLO), 17 and 15% (GHI), 16 and 14% (GLO), 15 and 13% (BAHI), and 14 and 12% (BALO). Backfat skatole and salivary gland 16-androstene concentrations were measured from samples taken at slaughter. Longissimus (LM) and semitendinosus (ST) chops from 24 pigs (with equal representation across diet and sex groups) were evaluated by trained panelists for tenderness, juiciness, and off-flavor. Consumer panelists evaluated acceptability of LM chops. In the 100-kg trial, HI diets improved (P < .05) carcass leanness in BO and BA but not in G. In both trials, BO were leaner (P < .05) than G, and both were leaner (P < .05) than BA. Skatole and 16-androstene concentrations were similar (P > .05) among sexes in both trials. In the 100-kg trial, trained panelists found BOLO chops had more (P < .05) off-flavor. In the 110-kg trial, all BO had more off-flavor (P < .05) than BAHI, BALO, and GHI but were similar (P > .05) to GLO. In both trials, BA chops were more tender (P < .05) than G and BO chops and LM chops had less off-flavor (P < .05) than ST chops. In the 110-kg trial, skatole was correlated (r = .28, P < .001) to off-flavor. A relationship may exist among diet, skatole deposition, and off-flavor. Untrained consumers reported all chops were equally acceptable (P > .05).

Tryptophan needs of lactating sows fed diets supplemented with crystalline lysine.

Large White x Landrace primiparous and multiparous sows (n = 115) were used to evaluate the tryptophan needs of lactating sows fed diets supplemented with crystalline lysine to contain .75% lysine. Sows were fed 1.8 kg of their allotted diets from d 110 of gestation until parturition and then were allowed ad libitum access to diets analyzed to contain either .12 (n = 58) or .17% (n = 57) tryptophan during a 21-d lactation. Diets were created by crystalline tryptophan and lysine additions to a corn-soybean meal basal diet that contained .12% tryptophan. Tryptophan level in the lactation diet did not affect number or weight of pigs at 21 d (P > .10). Sows fed .17% tryptophan were heavier at d 21 of lactation than those fed .12% tryptophan (P = .09) due to less weight loss during the 21-d lactation (P = .09). Feed intake was greater (P < .05) for sows fed .17% tryptophan than for sows fed .12% tryptophan. A reference diet analyzed to contain .11% tryptophan and .63% lysine was fed to an additional 11 sows only as a baseline for measuring plasma urea nitrogen and amino acids. Plasma tryptophan concentrations were higher (P < .05) for sows fed .17% tryptophan than for sows not fed added L-tryptophan. Among sows fed the low-tryptophan diets, sows fed the reference diet (.60% lysine) had higher (P < .05) plasma phenylalanine and valine concentrations than sows fed .75% lysine. Diet did not affect plasma concentrations of any other essential amino acid (P > .10). Plasma urea N levels were lower (P = .11) for sows fed the diet supplemented with tryptophan. Lactating sows allowed ad libitum access to diets containing .75% lysine benefited from higher feed intake and lower weight loss when dietary tryptophan levels were increased from .12 to .17%.

Effects of ground flaxseed in swine diets on pig performance and on physical and sensory characteristics and omega-3 fatty acid content of pork: I. Dietary level of flaxseed.

Forty-eight barrows and gilts were fed diets containing 0 (CO), 5, 10, or 15% ground flaxseed (FS) for the final 25 d before slaughter. Flaxseed treatments did not affect any production or carcass traits (P > .10). No pork processing problems due to lack of firmness were encountered. Amounts (milligrams/gram of tissue) of alpha-linolenic acid (ALA [18:3n-3]) and eicosapentaenoic acid (EPA [20:5n-3]) increased (P < .01) in both backfat layers and ALA increased (P < .01) in kidney (leaf) fat after FS. Alpha-linolenic acid and EPA increased (P < .001) in the raw belly in response to FS; the effect was maintained throughout processing (P < .01) to microwaved bacon. Alpha-linolenic acid and EPA increased (P < .01, P < .05, respectively) with amount of FS in longissimus thoracis and liver. In the brain, DHA decreased (P < .05) with amount of FS. Trained panelists in triangle tests were able to identify bacon from pigs fed 10 and 15% flaxseed. Panelists could not identify various treatments in the loin tests.

Effects of ground flaxseed in swine diets on pig performance and on physical and sensory characteristics and omega-3 fatty acid content of pork: II. Duration of 15% dietary flaxseed.

Four barrows and four gilts were assigned to each of five dietary treatments: a control (CO) diet or a 15% flaxseed (FS) diet fed for 7, 14, 21, or 28 d prior to slaughter. Flaxseed treatments did not affect any production or carcass traits (P > .10). No pork processing problems due to lack of firmness were encountered. Amounts (milligrams/gram of tissue) and percentages of alpha-linolenic acid (ALA [18: 3n-3]), arachidonic acid (AA [20:4n-6]), and eicosapentaenoic acid (EPA [20:5n-3]) increased (P < .001) in both backfat layers and in kidney (leaf) fat and docosahexaenoic acid (DHA [22:6n-3]) increased (P < .006) in the middle/inner backfat layer after FS. The effects of dietary FS on fatty acid profiles were maintained in lard and pastry. Alpha-linolenic acid, AA, and EPA increased (P < .001) and DHA increased (P < .021) in the raw belly in response to FS; the effect was maintained throughout processing to microwaved bacon. Percentage of oleic acid (OA [18:1n-9]) decreased (P < .016) in raw bellies after FS. Alpha-linolenic acid and EPA increased (P < .001) with duration of FS in longissimus thoracis and liver neutral lipids, polar lipids, and combined lipid fractions, but DHA increased (P < .004) only in longissimus thoracis polar and combined lipid fractions. Arachidonic acid decreased in the longissimus thoracis polar lipid fractions (P < .037) and in liver neutral (P < .01) and combined lipid fractions (P < .006) with FS. All ALA:AA and EPA:AA ratios increased (P < .001 to P < .048) with increased duration of FS (except ALA:AA in pastry [P = .56]). Processing of bellies into bacon and storing at -18 degrees C for 6 wk did not cause thiobarbituric acid (TBA) values to exceed a value of 1.0 after either the CO or FS diets. After microwaving bacon when TBA values approached 2.0, there was no FS dietary effect on TBA values. Trained panelists rated FS bacon more flavor-intense than CO bacon and recorded more flavor defects for FS bacon. A 105-member consumer group showed a higher frequency of "dislikes" for FS bacon than for CO bacon.

Influence of gestation energy level on the production of Large White x Landrace sows.

Sixty-four Large White x Landrace primiparous sows were utilized to evaluate the influence of feeding 6 vs 9 Mcal ME/d during gestation on reproductive performance. The sows remained on their respective gestation diets for four parities if they successfully farrowed, rebred and conceived. Sows fed 9 Mcal ME/d gained more weight (P less than .05) through the gestation period during parities 1 and 2 and were heavier (P less than .01) on d 110 of gestation for combined parities. Lactation weight loss was greater (P less than .05) for the sows fed 9 Mcal ME/d, resulting in similar weights at weaning. Ultrasonic backfat measurements were greater (P less than .01) on d 110 of gestation for sows fed 9 Mcal ME/d during parity 1 and remained higher (P less than .01) through the fourth-parity gestation. Although sow weaning weights were similar, sows receiving 6 Mcal ME/d scanned less backfat thickness. Gestation treatment significantly affected consumption of a common lactation diet provided ad libitum. Sows fed 6 Mcal ME/d during gestation consumed an average of 22 kg more feed (P less than .01) during lactation than those sows receiving 9 Mcal ME/d. Litter performance as measured by number and weights of pigs born alive and weaned was not altered (P greater than .10) by gestation energy intake. Days to return to estrus and the number of sows remaining in the study for four parities were similar (P greater than .10) between the two treatment groups. The number of farrowings for the four parities totaled 164, with 83 and 81 farrowings for the sows fed 6 and 9 Mcal ME/d, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Tryptophan and threonine requirements of young pigs and their effects on serum calcium, phosphorus and zinc concentrations.

Four 28-d trials were conducted using a total of 432 pigs, with average initial weight across trials ranging from 6.3 to 9.7 kg, to estimate the tryptophan (trials 1 and 2) and threonine (trials 3 and 4) requirements of pigs fed low protein, corn-sunflower meal diets. The effect of tryptophan, threonine and protein level on serum calcium, phosphorus and zinc also was studied. The diets contained either 12 or 13% protein and were calculated to be adequate in all nutrients except crude protein and the amino acid being investigated. A lysine supplemented, 18% protein, corn-sunflower meal diet was included in all trials as a positive control. In trial 1, weight gains of pigs increased linearly (P less than .005) while feed conversion improved cubically (P less than .05) as dietary tryptophan increased from .14 to .22%. Pigs fed the 18% protein diet gained faster (P less than .05) and required less feed/gain than pigs fed low protein diets. In trial 2, weight gains improved quadratically (P less than .005) and feed conversion improved linearly (P less than .05) as dietary tryptophan increased from .104 to .204%. Serum phosphorus and zinc concentrations were lower (P less than .05) in pigs fed the 18% protein diet. In both trials, serum urea N responded quadratically (P less than .05) to increasing dietary tryptophan, and was lower (P less than .05) in pigs that were fed diets supplemented with L-tryptophan than in those fed the low protein basal or 18% protein diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Toxic effects of selenium on growing swine fed corn-soybean meal diets.

A total of 96 crossbred pigs received various levels of sodium selenite to determine the effect of dietary selenium (Se) on growing swine fed corn-soybean meal diets. Levels of supplemental Se were 0, 4, 8, 12, 16 and 20 micrograms/g. There were linear decreases (P less than .01) in both gain and feed intake with increasing levels of dietary Se. Feed/gain increased numerically as dietary Se increased. Hair Se increased quadratically (P less than .01) and blood Se increased linearly (P less than .01) with increasing level of dietary Se. Cell volume and hemoglobin were not affected by dietary treatment. Increasing dietary Se significantly increased glutathione peroxidase (GSH-Px), glutamic-oxalacetic transaminase (GOT). and glutamic-pyruvic transaminase (GPT). External signs of selenosis were noted in some pigs fed 12 or 20 micrograms/g of Se. The toxic level of Se in a corn-soybean meal diet for crossbred pigs appears to be between 4 and 8 micrograms/g. Of variables studied, growth rate was the most sensitive indicator of chronic selenosis in swine.

Effects of seleniferous grains and inorganic selenium on tissue and blood composition and growth performance of rats and swine.

Two experiments were conducted to determine the effect of varying dietary selenium (Se) levels and Se source on growing swine. In Exp. 1, seleniferous wheat and oats were used to formulate diets containing .47, 2.58, 5.60 or 8.40 micrograms/g organic Se. Dietary Se level had no effect on pig performance during the 6-wk experiment as measured by daily gain, daily feed intake or feed/gain. Blood composition and enzyme activity were not affected by dietary treatment. Selenium concentrations of blood, hair, liver, kidney, heart, spleen and diaphragm muscle were increased linearly (P less than .01) as dietary Se increased. In addition, liver weight as a percentage of body weight was increased linearly (P less than .01) as dietary Se level increased. No signs of chronic Se poisoning were observed. Dietary treatments in Exp. 2 were similar to Exp. 1 with the exception that sodium selenite was utilized as the Se source and the diets were fed for 17 wk. Inorganic Se levels of .54, 2.63, 5.69 or 8.33 micrograms/g had no effect on pig performance as measured by daily gain, daily feed intake or feed/gain. Selenium concentrations of blood, hair, liver, kidney, spleen and diaphragm muscle were significantly increased as dietary Se level increased. Liver weight as a percentage of body weight was increased at the two highest dietary Se levels. Blood glutathione peroxidase activity was significantly increased by dietary treatment, while other blood variables were not affected. No signs of chronic Se poisoning were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of excess arginine on swine growth and plasma amino acid levels.

One hundred seventy-six crossbred weaned pigs (4 to 5 wk old) were used in two growth trials to determine the effect of excess arginine on pig growth and plasma amino acid levels. In the first 28-d growth trial, two lysine levels (1.03 and 1.26%) and three arginine levels (.94, 1.29 and 1.63%) were used in a nested treatment arrangement. Lysine supplementation improved daily gains (P less than .05), tended to improve feed efficiency (P less than .12) and caused a general reduction in plasma essential amino acid levels. Arginine had no effect on daily gain or feed intake, but pigs fed 1.03% lysine and 1.63% arginine had reduced gain/feed (P less than .05). Arginine did not affect gain/feed of pigs fed 1.26% lysine. Plasma lysine levels were reduced (P less than .06) by excess arginine in pigs fed 1.26% lysine, but not in pigs fed 1.03% lysine. The four treatments for the second 26-d growth trial consisted of three diets containing .92% lysine and either .72, 1.10 or 1.61% arginine and a positive lysine control (1.10% lysine, .72% arginine). Lysine was the limiting amino acid in the basal diet, but arginine had no effect on daily gain, daily feed intake, gain/feed or plasma lysine levels. Plasma threonine and methionine levels were reduced by excess arginine in both experiments, while the other plasma essential amino acid levels were not affected by dietary arginine. Conclusions are that large excesses of added arginine may affect lysine utilization, but pig performance was affected only when excess arginine was combined with a lysine deficiency. The arginine levels similar to those found in grain-soybean meal swine diets had no effect on pig performance in these experiments.

Compensatory responses of swine following protein insufficiency in grower diets.

Four trials involving 426 crossbred pigs were conducted to determine the effect of protein restriction during early growth on subsequent performance and carcass characteristics at 100 kg. The experimental animals averaged 25 to 27 kg initial weight in trials 1, 2 and 3, and 18.2, 22.7 and 27.3 kg in three weight groups in trial 4. Pigs were fed corn-soybean meal supplemented diets of 12, 14 or 16% protein. Protein restriction (12 or 14% protein diets), to 52 kg in trial 1 and during the initial 4-wk period in trials 2, 3 and 4, reduced rate and efficiency of growth; performance was reduced more on 12% protein diets. In the subsequent growth period, early protein restriction improved gain and feed to gain ratio. Performance for the total period was similar for pigs fed a 14% protein diet continuously to that of pigs fed a 16 to 14% protein sequence when pigs had an initial weight of 25 kg or more. However, lighter weight pigs did not completely compensate for decreased performance during the early 4-wk period. Carcass characteristics were similar for all protein sequences.