Effect of restricted postweaning growth resulting from reduced floor and feeder-trough space on pig growth performance to slaughter weight in a wean-to-finish production system

The effect of reduced pig growth rate postweaning as a result of restricted floor space and feeder trough space on subsequent growth to slaughter was investigated in a wean-to-finish system. Crossbred pigs (n = 1,728) were used in a randomized block design with a 2 x 2 x 2 factorial arrangement of treatments: 1) floor space (high [0.630 m2/pig] vs. low floor space [0.315 m2/pig]), 2) feeder trough space (unrestricted [4 cm/pig] vs. restricted feeder trough space [2 cm/pig]), and 3) period of imposing floor- and feeder-trough-space treatments (12 vs. 14 wk postweaning). Growth performance was measured from weaning (5.5 +/- 0.01 kg of BW; 17 d of age) to slaughter (the end of wk 25 postweaning). From the end of the treatment period to the end of wk 25, pigs on all treatments had the same floor and feeder trough space. Pigs with low floor space had lower (P < 0.01) ADG, ADFI, and gain:feed ratio than those with high floor space, and were therefore lighter (P < 0.05) at the end of the postweaning treatment period. Pigs given the restricted feeder trough space had lower (P < 0.05) ADFI, similar (P > 0.05) ADG, and higher (P < 0.01) gain:feed ratio than those with unrestricted feeder trough space during the treatment period. Pigs in the 14-wk treatment period had higher (P < 0.01) ADG and ADFI, but lower gain:feed than those in the 12-wk treatment during that period. In the subsequent period, from the end of treatment to wk 25, there was an interaction (P < 0.05) between floor space and treatment period; the difference in ADG and gain:feed for pigs on low vs. high floor space was greater for the 14-wk than the 12-wk treatment period. However, low-floor-space pigs tended (P = 0.06) to be lighter than high-floor-space pigs at the end of wk 25 postweaning. Neither feeder trough space nor treatment period affected pig growth performance during the period from the end of treatment to wk 25. Carcass backfat and longissimus depths at the end of wk 25 were not influenced (P > 0.05) by treatment. In summary, pigs with restricted growth due to low floor space until either 12 or 14 wk postweaning had increased growth and feed efficiency in the subsequent period to wk 25 postweaning, with only a slight effect on BW and no effect on carcass measures.     

Effect of group size on pig performance in a wean-to-finish production system

Crossbred pigs (n = 1,400) were used to evaluate the effect of group size (25 vs 50 vs 100 pigs/pen) in a wean-to-finish production system on growth performance and carcass measures. Pigs were weaned at 17 d (range = 15 to 19) of age with a mean initial BW of 5.9 +/- 0.02 kg and taken to a final mean pen weight of 116 +/- 0.9 kg. A 10-phase dietary regimen was used, and pigs had free access to feed and water. Feeder-trough space (4.3 cm/pig) and floor-area allowance (0.68 m2/pig) were the same for all group sizes. Compared to groups of 25, pigs in groups of 50 and 100 animals were lighter (P < 0.001) at the end of wk 8 after weaning and had lower (3%, P < 0.01) ADG and gain:feed (G/F) but similar (P > 0.05) ADFI during the first 8 wk of the study. At the end of the study, pig weight and the coefficient of variation in pig weight within a pen were similar (P > 0.05) across group sizes. During the period from 8 wk after weaning to the end of the study, pigs in groups of 100 compared to 50 animals had greater (3%, P < 0.01) ADG, and pigs in groups of 25 were intermediate for ADG. Average daily feed intake during this period was similar (P > 0.05) for all group sizes; however, G/F was greater (3%, P < 0.01) for groups of 100 compared to 25 or 50 animals. For the overall study period, ADG, ADFI, and G/F from weaning to slaughter weight were similar across group sizes (P > 0.05; 655, 648, and 658 g; 1,759, 1,755, and 1,759 g; and 0.37, 0.37, and 0.37; for ADG, ADFI, and G/F, respectively, for groups of 25, 50, and 100 pigs, respectively). Mortality was similar (P > 0.05) across group sizes; however, morbidity (pigs removed due to poor health or injury) was higher in groups of 25 pigs compared to the other two group sizes (7.0, 3.5, and 3.9% for groups of 25, 50, and 100, respectively; P < 0.05). Group-size treatment did not affect (P > 0.05) carcass dressing percentage, backfat thickness, or loin-eye depth. In summary, growth performance from weaning to market weight was not affected by group size.     

Impact of early postweaning growth rate as affected by diet complexity and space allocation on subsequent growth performance of pigs in a wean-to-finish production system

The objective was to evaluate the effect of restricted early postweaning growth rate due to diet complexity, pen space, or both on subsequent growth to market in a wean-to-finish system. Pigs (n = 1,728) were used in a randomized block design with a 2 x 2 factorial arrangement of treatments: 1) diet complexity (Complex vs Simple) and 2) space allocation (Unrestricted vs Restricted). Treatments were imposed for the first 8 wk after weaning (period 1) and growth was measured from weaning (5.0 +/- 0.01 kg body weight; 15 d of age) to the end of wk 23 postweaning. The Simple diet was based on corn-soybean meal with minimal inclusion of milk products, processed cereals, and animal protein-based ingredients compared to the Complex diet. Floor and feeder-trough spaces were 0.63 m2 and 4 cm and 0.21 m2 and 2 cm per pig for Unrestricted and Restricted space treatments, respectively. From the end of wk 8 to end of wk 23 (period 2), pigs on all treatments had the same floor and feeder spaces and were fed common diets. There was no interaction (P > 0.05) between diet and space treatments. In period 1, Simple diets resulted in similar average daily feed intake (ADFI; 639 vs 650 +/- 5.4 g; P > 0.05), but lower average daily gain (ADG; 408 vs 424 +/- 3.8 g; P < 0.01) and gain:feed ratio (0.64 vs 0.65 +/- 0.002; P < 0.001), and lighter body weight (2.8%; P < 0.01) compared to the Complex diets. In period 2, growth was not affected (P > 0.05) by previous diet complexity, and pig body weight was similar (114.4 vs 114.4 +/- 0.37 kg, P > 0.05) at the end of wk 23. In period 1, pigs with Restricted space had lower ADG (398 vs 434 +/- 3.8 g; P < 0.001), ADFI (621 vs 668 +/- 5.4 g; P < 0.001), and gain:feed ratio (0.64 vs 0.65 +/- 0.002; P < 0.01), and were lighter at the end of wk 8 (6.5%; P < 0.001) than those with Unrestricted space. However, in period 2, pigs with Restricted space had higher (P < 0.01) ADG (3%), ADFI (2%), and gain:feed ratio (3%) than those with Unrestricted space, and body weight was similar (114.5 vs 114.3 +/- 0.37 kg; P > 0.05) at end of wk 23. Carcass backfat and loin-eye depth at market body weight were influenced by neither diet nor space treatment. Using a simple diet program and restricted space allowance immediately postweaning resulted in a lower early growth rate, but had no impact on pig body weight or carcass measures at market.     

Effects of double stocking and weighing frequency on pig performance in wean-to-finish production systems

Two studies were carried out in different wean-to-finish barns to determine the effects of double stocking on pig growth performance. In Study 1, pigs (n = 1,560) were used in a randomized complete block design with a 2 x 2 factorial arrangement of treatments: initial stocking treatment (Single [52 pigs/pen] vs Double [104 pigs/pen] stocked for 10 wk after weaning) and weighing frequency (High [12 times during the study] vs Low [3 times]) on pig performance from weaning (5.9+/-0.01 kg BW; 17 d of age) to harvest (114+/-0.67 kg BW). Floor and feeder space per pig were 0.650 m2 and 4 cm and 0.325 m2 and 2 cm for the single- and double-stocked treatments, respectively. In Study 2, pigs (n = 1,458) were used in a randomized complete block design to evaluate two initial stocking treatments (Single [27 pigs] vs Double [54 pigs] stocked for 10 wk after weaning) on pig performance from weaning (4.8+/-0.01 kg BW; 15 d of age) to harvest (24 wk after weaning). Floor and feeder space per pig were 0.640 m2 and 3.4 cm and 0.320 m2 and 1.7 cm for single- and double-stocked pens, respectively. In both studies, double-stocked pigs were split at the end of wk 10 into two equal-sized groups of similar mean BW and CV of BW, and one group was moved to a different pen in the same building. In Study 1, performance was not affected (P > 0.10) by frequency of weighing. For the first 10 wk after weaning, the Double compared to the Single treatment had lower ADG (7.7 and 7.9%, for Studies 1 and 2, respectively; P < 0.001) and lighter pigs at wk 10 (6.8 and 7.3%, respectively; P < 0.001). During the first 10 wk in Study 1, Double compared to the Single pigs had lower ADFI (7%; P < 0.001) but similar gain:feed (P > 0.10). From wk 11 to harvest, pigs on Double and Single treatments had similar (P > 0.10) ADG in both studies and, in Study 1, ADFI was unaffected by initial stocking treatment, but double-stocked pigs had greater gain:feed (4%, P < 0.01). Double-stocked pigs required an additional 2 d to reach a fixed harvest BW (P < 0.05) in Study 1 and were lighter (4%; P < 0.05) at 24 wk after weaning in Study 2. Carcass measures were similar (P > 0.10) for double- and single-stocked pigs. Double-stocked pigs that were moved at the end of 10 wk had growth performance similar (P > 0.10) to those that remained in the original pen. In summary, double stocking reduced growth rate to 10 wk after weaning but subsequently had no effect on growth rate and improved feed efficiency.     

Individually measured feed intake characteristics and growth performance of group-housed weanling pigs: effects of sex, initial body weight, and body weight distribution within groups

Feed intake characteristics of 192, 27-d-old weanling pigs housed in groups and given ad libitum access to feed and water were measured individually with the use of computerized feeding stations. The groups were either homogeneous or heterogeneous as to BW distribution; pigs of three defined initial BW classes were used (mean BW of 6.7, 7.9, or 9.3 kg). The effects of BW distribution, BW class, and sex were studied with regard to average performance traits, latency time (interval between weaning and first feed intake), initial feed intake (intake during the first 24 h following first feed intake), and daily increase in feed intake during the interval between first feed intake and the day on which energy intake met or exceeded 1.5 times the maintenance requirement. Homogeneous and heterogeneous groups had similar latency times, initial feed intakes, and daily increases in feed intake. For the period 0 to 34 d after weaning, ADFI and ADG were also similar for homogeneous and heterogeneous groups, but gain:feed ratio was greater (P < 0.05) in the homogeneous groups. Gilts had higher (P < 0.05) initial feed intakes than barrows and also had greater (P < 0.05) ADFI and ADG during the period 0 to 13 d after weaning. Pigs with average BW of 6.7 kg had higher (P < 0.05) initial feed intakes than their counterparts with average BW of 7.9 kg and 9.3 kg, but the daily increase in feed intake was similar for the three groups. The lighter pigs had more daily visits and a lower feed intake per visit and tended to have a shorter postweaning latency to the onset of feeding than the heavier pigs. This study indicates that the high variability in early feeding behavior among group-housed weanling pigs may be related to BW and sex.     

Effects of proportion of pigs removed from a group and subsequent floor space on growth performance of finishing pigs

The effects of the proportion of pigs removed from an established group and subsequent floor space on growth performance during the final 19 d of the finishing period were evaluated using 28 pens of mixed-sex crossbred pigs (mean initial BW = 113.4 +/- 0.57 kg; n = 1,456; approximately 52 pigs per pen). A randomized block design was used with four pig-removal treatments: 1) 0% of pigs removed [Control], 2) approximately 25% of pigs removed, 3) approximately 50% of pigs removed, and 4) approximately 50% of pigs removed and floor and feeder spaces/pig decreased to equal those of Control. A block consisted of four pens with the same number of pigs and sex ratio per pen and with similar initial BW. Pens within blocks were randomly allocated to treatment, and the heaviest animals were removed from Treatments 2, 3, and 4 at the start of the study. Group size and floor space/pig for Treatments 1, 2, 3, and 4 were 52 and 0.65 m(2), 39 and 0.87 m(2), 26 and 1.30 m(2), and 26 and 0.65 m(2), respectively. Each pen contained a six-place feeder that provided 212 cm of total trough space; however, only three-places were accessible to pigs on Treatment 4. Compared with Controls, removing 25 or 50% of pigs resulted in increased (P < 0.001) ADG by 20.6 and 21.0%, ADFI by 10.8 and 7.9%, and G:F by 7.7 and 14.3%, respectively. Average daily gain by pigs on Treatment 4 (50% removal rate and decreased floor and feeder spaces) was greater (P < 0.05) than that of the Controls, but lower (P < 0.05) than that of Treatment 3 pigs (50% removal rate, no adjustment in floor or feeder spaces). No differences were observed among treatments for either morbidity or mortality. These results indicate that removing 25 or 50% of the heaviest pigs from groups of finishing pigs increased growth rate of the remaining pigs, and that the improved performance was only partly due to increased floor and feeder spaces.     

Effects of energy intake and body weight on physical and chemical body composition in growing entire male pigs

Two experiments were conducted to determine independent effects of BW and DE intake on body composition and the partitioning of retained body energy between lipid and protein in pigs with high lean tissue growth potentials and when energy intake limited whole-body protein deposition. In a preliminary N-balance experiment involving 20 entire male pigs at either 30 or 100 kg BW, it was established that whole-body protein deposition increased linearly (P < 0.05) with DE intake at both BW. These results indicate that DE intake controlled whole-body protein deposition and that these pigs did not achieve their maximum whole-body protein deposition when fed semi-ad libitum. In the main serial slaughter experiment, 56 pigs, with a BW of 15 kg, were assigned to one of four DE intake schemes and slaughtered at 40, 65, 90, or 115 kg BW. Within DE intake schemes, DE intake was increased linearly (P < 0.05) with BW, allowing for an assessment of effects of DE intake and slaughter BW on chemical and physical body composition (carcass, viscera, blood). Between 15 and 90 kg BW, average DE intake of 16.1, 20.9, 25.2, and 28.8 MJ/d supported average BW gains of 502, 731, 899, and 951 g/d, respectively. The proportion of whole-body protein present in the carcass increased with BW and decreased with DE intake (P < 0.05), whereas the distribution of whole-body lipid between carcass and viscera was not influenced by BW and DE intake. A mathematical relationship was developed to determine the relationship between DE intake at slaughter (MJ/d) and chemical body composition in these pigs: whole-body lipid-to-protein ratio = 1.236 - 0.056 x (DE intake) + 0.0013 x (DE intake)2, r2 = 0.71. The data suggests that absolute DE intake alone was an adequate predictor of chemical body composition in this population of entire male pigs over the BW and DE intake ranges that were evaluated, simplifying the characterization of this aspect of nutrition partitioning for growth in different pig populations.     

Effects of body weight and feed intake level on basal ileal endogenous losses in growing pigs

An experiment was carried out to determine the effects of feeding level, body weight, and time after surgery on basal ileal endogenous amino acid (AA) and N losses in growing pigs. Three pairs of littermate pigs were surgically prepared with ileo-rectal anastomoses. One pig in each pair was anastomosed at 38 kg BW, and the remaining pigs were anastomosed at 67 kg BW. Each pig received at different periods 50, 70, or 90 g of dry matter per kilogram of BW.75 of a protein-free diet according to a Latin square design involving three pigs starting at 45 kg BW and involving six pigs starting at 77 kg BW. For most AA, the time after surgery x feeding level interaction was significant. The basal endogenous losses (in g/d) increased linearly with feeding level at both BW. At the higher BW, the basal endogenous losses (in g/kg DMI) were constant regardless of feeding level, whereas at the lower BW they responded quadratically. At the low feeding level, the endogenous losses were higher than at the medium or high feeding level. We concluded that the basal endogenous losses are proportional to DMI when the feeding level is higher than 70 g/kg BW.75. The AA profile was not influenced by these three variables, but there was a large animal effect. These results suggest that, in digestibility trials, an assessment of the basal ileal endogenous AA losses must be performed on each pig to correct the apparent ileal AA digestibility data.     

日粮中添加乳清粉和膨化豆粕对断奶仔猪生产性能影响

选择30日龄断奶三元杂交仔猪(杜×长×大)64头。随机分成对照组、Ⅰ、Ⅱ、Ⅲ组,对照组饲以基础日粮,试验Ⅰ组日粮以膨化豆粕替代普通豆粕,试验Ⅱ组由3%的乳清粉替代3%的豆粕。试验Ⅲ组中膨化豆粕替代普通豆粕同时由3%的乳清粉替代3%的膨化豆粕。试验结果:对照组培育仔猪需46d,试验Ⅰ组(膨化豆粕组)培育仔猪需40d,试验Ⅱ组(乳清粉组)培育仔猪需43d,试验Ⅲ组(膨化豆粕+乳清粉组)培育仔猪需39d;平均日增重试验Ⅱ组显著高于对照组(P<0.05),试验Ⅰ、Ⅲ组极显著高于对照组(P<0.01),试验Ⅲ组极显著高于Ⅱ组(P<0.01)、显著高于试验Ⅰ组(P<0.05);饲料利用率试验Ⅲ组最高,对照组饲料利用率最差;腹泻率试验Ⅰ组下降了38.13%,试验Ⅱ组下降了34.63%,试验Ⅲ组下降了47.08%。结果表明利用膨化大豆或乳清粉等优质蛋白。调整日粮结构,可显著降低TI等抗营养因子和抗原物质的含量,减少腹泻率,提高生长性能。     

吡啶甲酸铬对生长猪生产性能和组织中铬残留的影响

选用96头体重(24.67±0.36)kg,公母各半达兰猪,随机分为4组,每组4个重复,每个重复6头。对照组饲喂基础日粮,3个试验组分别添加200、400μg/kg和800μg/kg吡啶甲酸铬(以铬计)。另外,选用8头体重(24.98±0.56)kg达兰猪,随机分为2组,添加1600μg/kg和3200μg/kg吡啶甲酸铬(以铬计),试验期28d。结果表明,添加200～800μg/kg吡啶甲酸铬对猪平均日增重和饲料转化效率无显著影响(P>0.05),但可提高饲料采食量,800μg/kg处理组的采食量显著高于其他3个处理组(P=0.01)。添加200～3200μg/kg吡啶甲酸铬猪组织中铬残留量为0.08～0.35mg/kg。     

不同绿色预混料对商品肉猪生产性能的影响

选择体重 15kg左右的杜×长×本三元杂交仔猪 12 0头 ,分为 3组 ,每组设 5个重复 ,每重复 8头猪进行试验 ,以观察不同绿色预混料对商品肉猪生产性能的影响。各组基础日粮完全相同 ,对照组饲喂含有药物添加剂的商品性预混料 ,2个试验组分别饲喂不含药物添加剂的自配预混料。试验结果表明 ,2个试验组的平均日增重明显高于对照组 (P <0 .0 5 ) ,而料重比和腹泻率明显低于对照组 (P <0 .0 5 ) ,肌肉pH值及肌内脂肪含量无明显差异 (P >0 .0 5 ) ,试验 2组与对照组相比 ,肌肉总色素含量明显提高 (P <0 .0 5 ) ,滴水损失明显下降 (P <0 .0 5 )。     

圈舍卫生状况及日粮色氨酸对断奶仔猪生产性能的影响

卫生状况的改变会影响动物色氨酸的代谢．可能会导致色氨酸供应不足。本试验旨在研究轻度炎症与色氨酸对动物生长性能、色氨酸代谢、血浆氨基酸浓度、血浆球蛋白、谷胱甘肽浓度等方面的影响。试验显示脏乱圈舍环境不仅可造成断奶仔猪轻度炎症反应．还会引起仔猪对色氨酸代谢的改变,表明充足的色氨酸有益于断奶仔猪生长．     

发酵蛋白饲料对生长育肥猪生产性能和猪肉品质的影响

本试验探讨了在日粮中使用发酵蛋白原料替代普通蛋白原料对生长育肥猪生产性能和猪肉品质的影响。结果表明,以发酵豆粕、发酵棉粕为主要蛋白原料的育肥猪无抗饲料配方产品与常规饲料相比,能显著提高育肥猪末重及平均日增重;能使每头猪养殖增收78.72元,提高毛利33.98%;能显著降低猪肉剪切力和滴水损失,提高猪肉氨基酸水平,改善了肉品质,提高了猪肉营养。     

Effects of controlling body weight on the semen production of large white turkey males

1. The consequences of limiting body weight gain during rearing on subsequent semen production and quality of Large White turkey males were assessed in a factorial experiment comparing ad libitum or restricted feeding in two periods (6 to 18 and 19 to 54 weeks of age). 2. The proportion of males giving semen, semen yields and concentrations of spermatozoa, and the incidence of unstable hock joints, were lower in males severely restricted from 6 to 18 weeks of age. 3. The best performance was from males that were reared on ad libitum feeding and fed 0.85 of ad libitum food consumption from 19 to 54 weeks of age.     

Effect of body weight on phosphorus digestibility and efficacy of a microbial phytase in young pigs.

The effect of body weight on P digestibility and on efficacy of supplemental Aspergillus niger phytase was studied in two experiments with young growing pigs. Excreta were collected quantitatively. All diets contained 2.0 g digestible P per kg dry matter at a maximum and renal P excretion never exceeded 15 mg/d. When dietary P mainly originated from monocalcium-phosphate, both P digestibility and Ca net absorption linearly increased by 3.6 and 5.6 percentage units, respectively, when BW increased from 15 to 35 kg. With a similar range in BW, P digestibility and Ca net absorption were unaffected by BW when P mainly originated from maize, barley and soybean meal. In both types of diet, crude protein digestibility increased with increasing body weight, whereas organic matter digestibility was effected by BW only in the diet containing maize, barley and soybean meal. Phytase (400 U/kg) almost doubled P digestibility when supplemented to a diet with P mainly originating from maize, soybean meal and barley. This effect of phytase supplementation was equal in pigs at 15.7 kg BW (33 vs. 55%) and at 39.1 kg BW (32 vs. 56%). Digestibility of any organic fraction was unaffected by supplemental phytase. With regard to on-farm conditions, it appears eligible from this results to apply digestibility coefficients for P determined in growing-finishing pigs for piglets as well.     

日粮添加甘露聚糖对商品化生产系统中母猪和仔猪生产性能的影响

本试验的目的旨在评价日粮中添加甘露聚糖(Mannan oligosaccharides,MOS)对商品化生产系统中母猪和仔猪生产性能的影响.试验所用的甘露聚糖-奥奇素(Bio-Mos)由美国奥特奇生物技术公司提供.母猪(处理组509头,对照组517头)为PIC猪种,平均胎次3.26胎,试验初体重264kg,产仔前3周开始在妊娠母猪饲料中添加甘露聚糖(奥奇素,添加量0.2%),哺乳期21天中,哺乳母猪饲料中添加奥奇素0.1%.分析饲料中的霉菌毒素,饲料中的黄曲霉毒素、T-2毒素、伏马菌素、DON(去氧瓜萎镰菌醇)和赭曲霉毒素含量很低,饲料间的霉菌毒素含量相近.母猪在妊娠第112天进入产房时和断奶时进行称重,仔猪在产后大约30 h时和断奶时进行称重.日粮中添加奥奇素不会降低母猪的体重,不会影响产活仔数,不会造成死胎(p＜0.05).添加奥奇素有利于提高产仔窝重,提高断奶重.添加奥奇素的处理组,猪增重为4.11kg,而对照组为3.79 kg.采食添加奥奇素日粮的母猪,所产仔猪断奶前的死亡率降低(处理组母猪与对照组母猪相比,9.09%对11.27%,p＜0.01).添加奥奇素后,母猪哺乳前初乳样品(处理组48个样品,对照组42个样品)中免疫球蛋白IgA,IgG和IgM的浓度提高.IgG对添加奥奇素的反应最大(p=0.007,5853对4842 mg/dL),IgM次之(p=0.03,273对241 mg/dL),IgA再次之(p=0.06,1178对1097 mg/dL).另外,母猪采食了添加奥奇素的日粮后,从产仔至发情的天数减短(5.20对7.27天,p＜0.01).母猪初乳中成分的变化有助于解释为什么仔猪生长性能得到提高.试验结果归纳如下,仔猪断奶前死亡率降低伴随着生长性能的改善表明,日粮中添加甘露聚糖有利于提高商品化生产系统中母猪和仔猪的生产性能.     

Effects of heat and social stressors and within-pen weight variation on young pig performance and agonistic behavior

A total of 486 crossbred weanling pigs was used in a series of experiments to determine first the effects of heat and social stress and their interaction on pig performance and, second, to determine a possible cause for the observed effects. Pigs were held six/nursery pen and fed and watered ad libitum. In Exp. 1, pigs were held at either thermal neutral 26.6 C for the 21 d and 23.8 C for the final 7 d, or at the heat-stress temperature (32.2 C) for the entire 28-d period. Within each temperature treatment, one-half of the pigs were left as single-litter controls and one-half were randomly regrouped (social stress). Pig feed intake and weight gain were reduced (P less than .05) among heat-stress pigs during the 7- to 28-d and 0- to 28-d periods. The interaction between social and thermal stress was significant for gain:feed ratio for the 7- to 28- and 0- to 28-d periods. Regrouping depressed gain:feed ratio only among heat-stressed pigs. In Exp. 2, a two-pig behavioral bioassay was used to determine if agonistic behaviors were influenced by heat stress. Pigs that were regrouped into 32.2 C rooms exhibited reduced mean level (P less than .05) and variation (P less than .001) of submissive behavior. Duration of aggressive behavior and latency to attack were unaffected by thermal treatments. Increased social stress at the time of regrouping could not account for poor performance of heat-stressed, regrouped pigs.(ABSTRACT TRUNCATED AT 250 WORDS)     

复合微生态制剂对猪生产性能的影响

随着经济和社会的发展,食品中的抗生素残留和菌株的耐药性问题已经越来越受大家关注.在这种情况下,开发低成本规模化生产的微微生态饲料添加剂已经成为一种科学养殖趋势.使用微生态制剂替代抗生素,一方面可以大大降低药源性(主要来自于饲料)疾病,改善猪群整体亚健康状况,另一方面也可以生产出无抗生素残留的优质猪肉产品,满足人们对绿色健康食品的迫切需求[1-2].本试验旨在应用复合微生态制剂,对生长育肥猪进行饲养试验,分别进行了复合微生态制剂替代药物添加剂试验、对肠道菌群的影响、对机体免疫水平的影响、对断奶仔猪发病率的影响及对生长育肥猪增重的影响等试验.     

甘露聚糖酶对大猪生产性能的影响

为探讨甘露聚糖酶在常规饲养水平下 ,对大猪生产性能及其经济效益的影响 ,试验选用中猪阶段结束后杜×长×大三元杂大猪 72头 ,依据体重、性别比例相近的原则 ,进行分组处理 ;各组基础日粮相同 ,营养水平一致 ,A组饲喂基础日粮 +0 .1 %复合酶A(不含甘露聚糖酶 ) ,B组饲喂基础日粮 +0 .1 %复合酶B(含 1 0 0 0U/g甘露聚糖酶 )、C组饲喂基础日粮 +0 .1 %复合酶C(含2 0 0 0U/g甘露聚糖酶 )。试验期从 2 0 0 2年 9月 30日至 2 0 0 2年 1 0月 30日 ,共 30d。试验结果表明 :试验期日增重A组为 739g、B组为 785g、C组为 835g ,B、C组日增重比对照组分别提高 6 .2 2、1 2 .99;料肉比A、B、C组分别为 3.5 4、3.2 9、3.0 2 ,B、C组比对照组分别降低 7.1、1 4 .7% ;综合经济效益每千克增重饲料成本B组、C组分别为 5 .4 9、5 .0 4元 ,对照组为 5 .91元 ,B、C组经济效益分别提高 7.1、1 4 .7%。