低聚果糖对杜洛克仔猪生产性能的影响研究

本试验选用３２ 头３６ ±２ 日龄杜洛克仔猪按性别、体重分为对照组和试验组,对照组添加１０×１０ － ５ 阿散酸和１５ ×１０ － ６ 硫酸抗敌素,试验组添加０－２ ％ 低聚果糖。３６ｄ 的饲养试验表明：１）０－２ ％低聚果糖提高断奶仔猪日增重１９－８８％ （Ｐ＜ ０－０１） ,提高采食量１８－０４ ％ （Ｐ＞ ０－０５） ,降低料重比２－２０ ％ （Ｐ＞ ０－０５） 。２）０－２ ％ 低聚果糖降低断奶仔猪腹泻发病率４６－７％ （ 绝对值） ,降低腹泻频率７７－８８ ％ （ 接近于Ｐ＜ ０－０５） 。３）０－２ ％ 低聚果糖能够显著提高经济效益,降低生产风险。     

日粮中添加蜂花粉对蛋鸡提高产蛋率的效果试验

日粮中添加蜂花粉的试验组，与未添加的对照组，两组产蛋率分别为８７－７％ 和８０－２％ ，两组差异显著（Ｐ＜ ０－０５） ；平均蛋重分别为６２－５５±１－２２ｇ 和６２－５４ ±１－３１ｇ ，两组差异不显著（Ｐ＞ ０－０５） ；料蛋比分别为２－３５：１ 和２－５１：１，两组差异显著（Ｐ＜ ０－０５） ；试验组比对照组提高经济效益１５－７％ 。     

亚硒酸钠VE对母猪产仔性能的影响

选用品种和胎次相同２８头妊娠母猪，随机分为对照组和试验组，各为１４头，试验组在预产前４０天和２０天各注射一次亚硒酸钠ＶＥ５ｍｌ／头，试验结果表明，试验组活仔窝重和仔猪初生个体重分别比对照组提高１８．６％（Ｐ〈０．０１）和１９．０％（Ｐ〈０．０１），且试验组没有出现僵胎，而对照组僵胎率为４．４％，但窝产仔猪数差异不显著（Ｐ〉０．０５）。     

蜂花粉对蛋种鸡生产性能及蛋品质影响的研究

选择海兰蛋种鸡２４０羽，随机分为四组，对照组饲喂基础日粮，试Ⅰ、Ⅱ、Ⅲ组分别饲喂在基础日粮中添加 ０． ５％、 １． ０％、 １． ５％蜂花粉的日粮。试验期２８天。试验结果表明：种鸡产蛋率分别提高了 ３. １６％、 ４．９６％（ｐ ＜０. ０５）、３． ９９％，（ｐ ＜０． ０５），料蛋比分别下降了 ２.７２％、 ６．３６％（ｐ＜０．０５）和３．１８％，死淘率各下降了１．６７％，种蛋合格率分别提高了 １． ３７％， ３． ０３％（ｐ＜０． ０５）和 １． ６４％，种蛋受精率试验组均高于对照组，但差异不显著，孵化率分别提高了２.２４％，３.７１％和６．４１％（p＜０．０５）。蛋品质测定结果表明，试验Ⅱ组较对照组的蛋形指数与蛋黄指数分别提高了３.９７％（ｐ＜０．０５）和７．１０％（ｐ＜ ０．０５），蛋比重、蛋黄相对重、蛋壳相对重、蛋壳厚度和哈夫单位，试验组与对照组无显著差异。     

利用合成氨基酸配制仔猪低蛋白日粮研究

选择４２ 日龄平均体重１１．００ｋｇ 的三元杂交断奶仔猪３０ 头, 随机分为对照组和试验组。分别饲喂２０％ 蛋白日粮（ 含异亮氨酸０－６４ ％ ） 和低蛋白（１６ ％ ） 低异亮氨酸（０－４１％ ） 日粮＋ 合成异亮氨酸（０－２３） 。试验结果： 试验组日增重和日采食量分别比对照组提高６ ．２ ％ 和１８ ％ （Ｐ＞０ ．０５） ,饲料增重比降低３ ．７％ （Ｐ＞ ０ ．０５） 。血清尿素氮、总游离氨基酸、葡萄糖、胰岛素和皮质醇含量组间无显著差异。血清氨含量试验组显著低于对照组（Ｐ＜ ０ ．０５） 。结论：通过合理补充合成氨基酸, 能够节约仔猪日粮蛋白质４ ％ ; 通过补充合成异亮氨酸, 血球粉在断奶仔猪日粮中的用量可提高至６％ 而不会降低仔猪生长性能。     

大蒜素替代土霉素对断奶仔猪生产性能的影响

选用 ７２头 ２４日龄断奶健康仔猪，随机分为 ３个处理，每个处理 ３个重复，每个重复 ８头。各处理组基础日粮一致。处理Ⅰ为对照组，处理Ⅱ组和处理 Ⅲ组分别添加大蒜素２００ｍｇ／ｋｇ、土霉素２００ｍｇ／ｋｇ于日粮中。结果表明：与对照组比较， Ⅱ组日增重提高 ８．３５％（Ｐ＜０．０５），料重比降低 ８．２４％，Ⅲ组日增重提高５．２４％（Ｐ＜０．０５），料重比降低７．１４％。采食量均无显著差异，Ⅱ组与Ⅲ组相比较，前者日增重比后者提高２．８６％（Ｐ＞０．０５），料重比下降１．２０％，两者均对仔猪有促长作用，相同添加量，大蒜素可以替代土霉素。     

猪用自动干湿饲喂器应用效果的研究

先后选用１１４头和１０５７头７０～７７日龄同期转群的杜大长三元杂交仔猪进行了两次试验,研究了采用自动干湿饲喂器（试验组）和常规方式饲喂（对照组）对生长肥育猪生产表现的影响。试验１经３０天试验,结果表明：试验组的平均日增重比对照组提高１１．８７％（Ｐ＜０．０５）;饲料利用率提高２３．２９％（Ｐ＜０．０５）;头均毛利增加２９．２４元,经济效益提高４４．９６％。试验２各组试猪饲养至平均体重约达９３ｋｇ,结果表明：试验组的平均日增重、饲料利用率、头均毛利分别比对照组提高１４．３１％（Ｐ＜０．０５）、１３．５０％（Ｐ＜０．０５）和４９．８６元,经济效益提高３２．４９％;饲养周期缩短１９天,栏舍利用率提高１４．８０％。     

磁化对猪精液品质影响

将稀释后的精液分成两份，一份为对照组，另一份放进Ｈ型强磁场磁化杯中磁化１０分钟做为试验组。然后测定精液品质并给发情母猪输精。结果表明：试验组精子活率比对照组提高１５％，差异极显著（ｐ＜０．０１）；精子存活时间比对照组延长，存活指数增大（ｐ＜０．０５），精子畸形率和顶体异常率比对照组略低，差异不显著（ｐ＞０．０５）。用磁化精液给发情母猪输精，第一情期受胎率比对照组提高１４．１３％，差异显著（ｐ＜０．０５）；平均窝产仔数比对照组多２．１２头，差异极显著（ｐ＜０．０１）。     

大蒜素替代土霉素对断奶仔猪的影响

选用７２头２４日龄断奶健康仔猪，按血缘相同、体重接近（Ｐ〉０．０５）公母一致的原则随机分为３个处理，每个处理３个重复。各处理组基础日粮一致。处理Ⅰ组为对照组，处理Ⅱ组和处理Ⅲ组分别添加大蒜素２００ｇ／ｔ、土霉素２００ｇ／ｔ于日粮中。结果表明，与对照组比较，处理Ⅱ组日增重提高８．３５％（Ｐ〈０．０５），料重比降低８．２４％，处理Ⅲ组日增重提高５．３４％，（Ｐ〈０．０５），粒重比降低７．１４％。采食量均无显著差异，处理Ⅱ组与处理Ⅲ组相比较，前者日增重比后者提高２．８６％（Ｐ〈０．０５），料重比下降１．２０％，两匀对仔猪有促长作用，相同添加量，大蒜素可以替代土霉素。     

甜菜碱饲喂生长肥育猪效果试验

选择体重相近的２０头生长肥育猪随机分为两组，对照组饲喂基础日粮，试验组在基础日粮中添加０．２％的甜菜碱，结果表明，试验组的背膘厚度为２４．０１毫米，对照组为２７．０２毫米，两组间差异显著（Ｐ＜０．０５）；日增重和料重比，试验组与对照组无明显差异（Ｐ＞０．０５）。     

Manipulation of growth in pigs through treatment of the neonate with clenbuterol and somatotropin

Neonatal pigs were treated with lipolytic agents to determine whether this would cause a long-term decrease in their ability to deposit fat, with a consequent increase in muscle growth and feed efficiency. Groups of 25 female piglets were given clenbuterol (100 microg/kg BW), porcine somatotropin (pST; 100 microg/kg BW), pST plus clenbuterol, or saline injections from 3 d to 40 d of age. Five piglets from each group were then slaughtered to determine body composition. Clenbuterol and pST both increased ADG up to weaning when given separately (24%, P < 0.05; 20%, P < 0.1 respectively) but did not reduce fat deposition. In contrast, pigs given clenbuterol plus pST showed no increase in ADG and a 41% reduction in carcass fat (P < 0.05). Clenbuterol caused a marked decrease in beta2-adrenoceptor density in porcine adipose tissue (P < 0.001) and skeletal muscle (P < 0.01). This effect was attenuated by concurrent pST treatment, which helps to explain the synergistic effect of these drugs on fat deposition. Once the drugs were withdrawn at 40 d, the anabolic effect of pST gradually disappeared, so that the live weight of pST-treated and control pigs was identical at 168 d. Clenbuterol withdrawal caused the rapid loss of extra weight gained, plus an additional 4 to 5 kg live weight that was never recovered. During the 4-wk finishing period there was an increase in feed intake in pigs that had previously undergone treatment with pST (23%, P < 0.1), with no increase in ADG, and so feed efficiency was impaired (P < 0.05). Pigs that were treated with pST plus clenbuterol showed no marked increase in feed intake during this period. Carcasses from clenbuterol-treated pigs tended to be leaner at 168 d, but there was no long-term effect of pST or the combined treatment on carcass composition. Overall, the treatment of neonatal pigs with repartitioning agents was counter-productive, due to the withdrawal effects of the beta-adrenefgic agonist and the delayed long-term effect of pST on feed intake.     

Administration of porcine somatotropin by sustained-release implant: growth and endocrine responses in genetically lean and obese barrows and gilts.

Previous studies have documented the effectiveness of porcine somatotropin (pST) administered by daily injection in promoting lean tissue growth in lean and obese pigs and the influence of sex and genotype. The present study examined the accretive responses in pigs of different lines and sexes to a slow release formulation of pST (pST-SR). Implants that deliver 2.0 mg of pST/d were implanted in genetically lean and obese barrows and gilts at 65 +/- .7 kg BW (mean +/- SE). Pigs received no, one, or two implants (i.e., doses of 0, 2.0, and 4.0 mg of pST/d). Pigs (four per line x sex x dose) were housed individually and continuously supplied with fresh water and a 19% CP diet containing 1.08% lysine. Pigs were slaughtered on d 0 (four per line x sex) and at the end of the trial (approximately 42 d after implantation) for estimation of initial composition and calculation of accretion rates. Blood samples were collected at d 0, 7, 14, 28, and 42 to measure endocrine and metabolite responses to pST-SR. Sustained-release pST elevated (P < .05) circulating pST throughout the trial with peak concentrations at d 7. On d 7, serum pST concentrations in the pigs given 2.0 mg of pST-SR per day were 16-fold greater than those in control pigs, and in pigs given 4.0 mg of pST-SR per day pST concentrations were 33-fold greater than in controls. Elevated serum pST resulted in increased (P < .05) serum concentrations of insulin-like growth factor (IGF)-I, IGF-II, insulin, and glucose and in reduced (P < .05) concentrations of urea nitrogen and IGF binding protein (IGFBP)-2. Gain was not influenced by pST-SR dose; however, feed consumption was reduced (P < .05) and efficiency of gain was increased (P < .05). Accretion of all body components except cold carcass weight, cecum, and untrimmed Boston butt and ham were changed (P < .05) with pST-SR administration. Heart and stomach were the only components of the carcass and offal whose accretion was not affected by line or sex. Increases in accretion of carcass components (< 75%) induced by sustained-release pST were considerably less than those measured in the organs (liver, 157%; lungs, 748%). The pST-SR treatment resulted in elevated serum concentrations of pST and its mediators and improved efficiency and composition of gain.(ABSTRACT TRUNCATED AT 400 WORDS)     

Interrelationships between dietary lysine, sex, and porcine somatotropin administration on growth performance and protein deposition in pigs between 80 and 120 kg live weight

Sixty male and 60 female crossbred pigs were allocated to an experiment to investigate the effects of porcine somatotropin (pST) administration (0 or 6 mg/d) and dietary lysine content on growth performance, tissue deposition, and carcass characteristics over the live weight range of 80 to 120 kg. Pigs receiving pST were given diets containing 6.9, 7.8, 8.8, 9.7, 10.6, or 11.5 g lysine/kg, whereas control pigs received diets containing 4.8, 5.8, 6.9, 7.8, 8.8 or 9.7 g lysine/kg. These dietary levels ranged from 0.40 to 0.70 g available lysine/MJ of DE for pST-treated pigs and from 0.28 to 0.58 g available lysine/MJ of DE for control pigs. Pigs were individually housed in pens, and there were five replicates of each treatment. All diets contained 14.5 MJ of DE/kg and were offered for ad libitum consumption to pigs between 80 and 120 kg live weight. Growth rate increased exponentially and food conversion ratio (FCR) decreased exponentially with increasing levels of lysine. In addition, there was a significant sex x pST interaction such that pST reduced the sex difference in FCR. Growth rate was faster in boars than in gilts and was increased by pST at the higher levels of dietary lysine. Similarly, FCR was lower for boars than for gilts and was decreased by pST at the higher dietary lysine levels. The optimum growth rate and FCR were defined as the lysine level at which growth rate and FCR were 95% and 105%, respectively, of the lysine plateau. The optimum growth rate and FCR were achieved at similar dietary lysine contents and were approximately 0.35 and 0.52 g available lysine/MJ of DE for control and pST-treated pigs, respectively. Protein deposition in the carcass increased exponentially with increasing dietary lysine level, was higher in boars than in gilts, and was increased by pST at the higher dietary lysine contents. Sex had no effect on dietary lysine required to maximize protein deposition. The dietary lysine contents required to ensure 95% of plateau protein deposition of 104 and 153 g/d were 0.39 and 0.55 g available lysine/MJ of DE for control and pST-treated pigs, respectively. The increase in lysine requirement with pST seems to be commensurate with the increase in protein deposition.     

Physiological and immunological responses to weaning and transport in the young pig: modulation by administration of porcine somatotropin

To examine the effects of exogenous porcine (p) ST on measures of stress and immune function in weaned pigs with or without transport, pigs (20 +/- 1 d of age) received daily injections of pST (0.5 mg/kg; n = 16) or saline (n = 16) for 5 d. On d 5, a blood sample was collected immediately before injection. At 4 h postinjection, pigs were weighed, sampled for blood, injected with di-nitrophenyl-conjugated keyhole limpet hemocyanin, and weaned. One half of the pigs in each group were transported for 3 h before placement in the nursery. Pigs were weighed, and blood was collected on 1, 7, and 14 d postweaning. Statistical significance was set at P < 0.05. Serum IGF-I concentrations were increased by pST and decreased by weaning, but not affected by transport. The free cortisol index was elevated in all pigs 1 d postweaning, although less in transported versus nontransported pigs. By 7 d postweaning, the free cortisol index returned to prewean values. Serum concentrations of immunoglobulin (Ig) G increased in all pigs by 14 d postweaning, but were not affected by pST or transport. Serum IgM concentrations were elevated at 7 and 14 d postweaning. Before weaning and again 1 d postweaning, pigs treated with pST had greater concentrations of IgM than did control animals. Circulating neutrophils increased in pST-treated pigs 4 h after the final pST injection. Improved immune function in weaned pigs by pST may lead to greater health and growth in a commercial setting.     

Effect of recombinant porcine somatotropin on lactational performance and metabolite patterns in sows and growth of nursing pigs

Sixteen crossbred sows (Yorkshire x Duroc) were used to determine the effect of recombinantly derived porcine somatotropin (pST) on lactational performance and the pattern of plasma metabolites and growth rate of nursing pigs. Daily s.c. injections of either pST (8.22 mg.sow-1.d-1) or excipient were administered at 1000 on d 12 through d 29 of lactation. Jugular cannulas were inserted in three sows/treatment and hourly blood samples were collected on d 11 to 13 and d 28 to 29 of lactation to determine the effect of treatment on plasma concentrations of somatotropin, glucose and nonesterified fatty acids in plasma. Milk production and weight of nursing pigs were determined pretreatment (d 9 and 10) and on d 16, 22 and 28. Milk production of sows receiving pST progressively increased above that of control sows and was 22% greater on d 28. Milk composition was not affected by treatment with pST (P greater than .10), so that the increase in yields of milk fat, lactose and solids paralleled the increases in milk yield. Total milk protein yield tended to be higher in sows receiving pST, but protein yield was greater (P less than .10) only on d 28. Pigs suckling sows treated with pST weighed .34 kg more at the end of the lactation period (P less than .05). Sows receiving pST consumed less feed (P less than .05) during the treatment period, and, as a result, lost more weight (P less than .10) and backfat (P less than .05) than control sows. Average concentrations of plasma somatotropin were elevated approximately 2.5-fold above baseline levels by exogenous pST. No acute alterations in plasma glucose or nonesterified fatty acids were observed in response to pST treatment, however, sows receiving pST had a chronic elevation of plasma glucose on d 29 of lactation.     

A gonadotropin-releasing factor vaccine (Improvac) and porcine somatotropin have synergistic and additive effects on growth performance in group-housed boars and gilts

Two hundred and twenty-four pigs (112 boars, 112 gilts) housed in pens of seven pigs per pen were used in a 2 x 2 x 2 factorial design, with the factors of vaccination with a gonadotropin-releasing factor (GnRF) vaccine (Improvac; 0 or 2 mL at 13 and 17 wk of age), porcine somatotropin (pST; 0 or 5 mg/d from 17 wk of age), and gender. Pigs were weighed and feed intake was measured from 17 wk of age until slaughter at 21 wk of age. Body composition was estimated by dual-energy X-ray absorptiometry in two focus pigs per pen at 17 and 21 wk of age. Testes and ovary weights at slaughter were decreased by Improvac treatment (P < 0.001), but were not altered by pST treatment (P > 0.44). Daily gain was lower for gilts than boars (1,128 vs. 1,299 g/d, P < 0.001) and was increased by pST (1,172 vs. 1,255 g/d, P = 0.003) and Improvac (1,150 vs. 1,276 g/d, P < 0.001) treatments. Feed intake (as-fed basis) was lower in gilts than in boars (2,774 vs. 3,033 g/d, P = 0.002), was decreased by pST (3,037 vs. 2,770 g/ d, P = 0.002), and was increased by Improvac treatment (2,702 vs. 3,105 g/d, P < 0.001). As a result of the differences in feed intake and daily gain, feed conversion efficiency (gain:feed) was lower for gilts than for boars (0.403 vs. 0.427 P = 0.025), was improved by pST (0.385 vs. 0.452, P < 0.001), but was unchanged by Improvac treatment (0.423 vs. 0.410, P = 0.22). Carcass weight was lower in gilts than in boars (75.3 vs. 77.0 kg, P = 0.012), was unchanged by pST treatment (75.9 vs. 76.4 kg, P = 0.40), and was increased by Improvac treatment (75.1 vs. 77.2 kg, P = 0.003). Lean tissue deposition rate was lower in gilts than in boars (579 vs. 725 g/d, P < 0.001), was increased by pST (609 vs. 696 g/d, P < 0.001) and by Improvac treatment (623 vs. 682 g/d, P = 0.014). Fat deposition rate tended to be lower in gilts than in boars (214 vs. 247 g/d, P = 0.063), decreased by pST treatment (263 vs. 198 g/d, P < 0.001), and increased by Improvac treatment (197 vs. 264 g/d, P < 0.001). For pigs treated with both pST and Improvac, daily gain and lean tissue deposition rate was greater than for pigs that received either treatment alone, whereas fat deposition rate and feed intake did not differ from untreated control pigs. In conclusion, Improvac increased growth rate through increased lean and fat deposition, but concomitant use of Improvac and pST increased lean gain above either alone, while negating the increase in fat deposition in pigs treated with Improvac.     

Somatotropin and adipose tissue metabolism: substrate and temporal effects

The purpose of these studies was to determine the time course for changes in feed intake, blood metabolites, and lipogenic activity in adipose tissue in response to the initiation of porcine somatotropin (pST) treatment and following withdrawal from treatment in barrows. An initial study was conducted to determine the impact of chronic pST treatment (4 wk of daily injection; 0 vs 4 mg/d) on adipose tissue lipid metabolism in barrows (initial weight 67 kg). Feed efficiency was improved 27%, backfat thickness was decreased 43%, and glucose and lactate oxidation and incorporation into lipid in adipose tissue was reduced 70 to 86% in pST-treated pigs. Palmitate esterification was decreased 44%, whereas palmitate oxidation was unaffected. In vitro metabolism of lactate, glucose, and palmitate in liver slices was not affected by pST treatment. The time-course for changes in intake and adipose tissue metabolism in response to 7 d of pST (0 vs 4 mg/d) treatment and 7 d of withdrawal was examined in subsequent studies in barrows (initial weight 75 kg). Feed intake during pST treatment was significantly (P < .05) less than in control pigs within 24 h of the initiation of treatment and remained low through 3 d after withdrawal. Adipose tissue biopsies were obtained on d 0, 1, 2, 4, and 7 of the treatment phase and on d 2, 4, and 7 after withdrawal from 7 d of treatment. Maximal inhibition of lipogenesis by pST treatment in adipose tissue in vitro was observed on d 4 (-68%) and d 7 (-69%). Similarly, fatty acid synthase activity declined during the treatment period, with the greatest change noted on d 7 (-26%). After withdrawal from treatment, lipogenesis gradually increased, returning to control values 7 d after withdrawal. Levels of IGF-I began to increase from d 1 to d 7 of treatment, continually decreased during withdrawal, and were normalized by the end of the withdrawal period. Plasma urea nitrogen concentrations decreased during treatment, increased during the withdrawal phase, and were normalized 4 d after the last pST treatment. Overall results indicate that most of the metabolic changes in response to pST occur within 1 wk of treatment and return to pretreatment values after 7 d of withdrawal from treatment.     

Relationship of mode of porcine somatotropin administration and dietary fat to the growth performance and carcass characteristics of finishing pigs.

Ninety-six pigs were used to investigate the relationship of diet (control vs fat-supplemented with equal energy:protein ratios), porcine somatotropin (pST) administration (non-treated; 2 mg/d, daily injection; and 2 mg/d, 6-wk implant), and sex (barrows and gilts) to performance and carcass characteristics. Diet and pST treatments were initiated at 87 kg of BW and continued for 38 d. Both the fat-supplemented diet (P less than .001) and pST treatment (P less than .0001) improved feed efficiency. The effects of diet were accounted for by differences in energy density of the diets. Across diets, pST improved gain:feed ratio by 29 and 16% in pigs treated by daily injection and the implant, respectively; the two modes of delivery resulted in different responses (P less than .01). Circulating insulin-like growth factor I (IGF-I) levels, determined from blood samples drawn on d 35, were increased 2.5-fold above those of controls in pigs treated by either daily injection or the implant. However, the elevation of glucose and decrease in blood urea nitrogen concentrations in response to pST were of a greater magnitude in pigs treated by daily injection. Similarly, reductions in backfat thickness and the rate of backfat accretion determined by ultrasound were greater in response to the daily injection of pST than in response to the implant. Lean meat ratio, calculated from measurements with a Fat-O-Meater probe, was increased by 6 and 13% by the implant and daily injection, respectively. It is concluded that although the use of an implant that delivers pST on a continuous basis was as effective as the same dose administered as a bolus injection for increasing IGF-I levels, it was less effective in improving feed efficiency and carcass quality.     

Effects of exogenous somatotropin during early gestation on maternal performance, fetal growth, and compositional traits in pigs

The objective of this study was to determine the effects of maternal treatment with porcine somatotropin (pST) during early gestation on embryonic survival, fetal development, and internal environment for fetal growth. Sixty-two crossbred gilts received daily injections of either 3 mL of a placebo (control, n = 31) or 6 mg of pST (n = 31) from d 10 to 27 of gestation. Representative gilts were slaughtered on d 28, 37, and 62 of gestation. The remaining gilts were allowed to farrow. It was found that embryonic survival was not influenced by pST treatment (P > 0.10). However, pST affected the growth and composition of the maternal (endometrium) and fetal (chorion) parts of the placenta. Thus, endometrial RNA concentration tended to be increased by pST at d 37 (P = 0.15), and it was increased at d 62 (P < 0.05) of gestation, which is indicative of increased capacity for protein synthesis. At birth, placental chorion weight (P < 0.10) and contents of DM and protein (P < 0.05) were increased due to pST treatment, but no effects were detectable up to d 62 of gestation. Maternal pST treatment was effective at increasing nutrient supply to the embryo as suggested from elevated glucose concentrations in amniotic and allantoic fluids (P < 0.05) at d 28 of gestation. With regard to prenatal growth, embryonic DNA concentration was slightly elevated at d 28 (P < 0.10), but pST did not induce any changes in average embryonic, fetal, or neonatal weights. However, within litters, the birth weights of piglets in the 25% lowest weight group (LW) were increased by pST treatment vs control LW pigs (1,241+/-55 vs 1,099+/-59 g, P < 0.10). Thirty-eight neonates from 15 litters divided among the three weight groups were examined for body composition. The weight of the intestinal tract was increased above average after maternal pST treatment (P < 0.01). Additionally, the amounts of tissues such as bone (P = 0.12) and s.c. fat (P = 0.06), and of protein, fat (P = 0.10), and ash (P < 0.05) were increased, whereas the relative body composition remained unchanged by pST (P > 0.10). On average, muscle protein concentration was elevated due to pST (P < 0.01), and, in LW piglets, plasma IGF-I concentration was increased (P < 0.10). The results suggest that maternal somatotropin is a critical factor in early pregnancy capable of influencing placental nutrient transfer and placental growth. It thereby selectively improves the growth conditions for the smaller littermates.