保持断奶时大窝的仔猪的生长性能(3)

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5.3. Diet Acidification

Early weaned pigs produce insufficient levels of gastric acid which can result in a high stomach pH. As a result, the digestion of nutrients, especially protein is reduced. Moreover, high pH is favourable for the proliferation of diarrhoea-causing micro-organisms in the weaned pig. The use of organic acids has been suggested as a means of lowering gastric acidity in weaned pigs and has been reported to improve growth performance. The benefits that arise from feeding organic acids include an inhibitory effect on pathogenic bacteria, increased amino acid and energy digestibility and an increase in nitrogen retention. The response to organic acids was previously found to be greatest in diets with low levels of dairy products. Dairy products contain lactose which can be fermented to lactic acid thus reducing gut pH. In addition, milk proteins are much more easily digested than vegetable proteins in the immature gut. The response to diet acidification might be expected to be reduced when provided in post-weaning diets to pigs that were provided with creep feed prior to weaning as creep feeding of suckling pigs is thought to benefit post-weaning pig performance by stimulating gastric acid production and enzyme secretion.

5.3  饲料酸化

早期断奶仔猪产生胃酸使胃pH值高，由于水平不足，营养物质的消化不足，尤其是蛋白质消化不良。 然而，高pH值有利于断奶仔猪肠道内微生物繁殖，导致腹泻。建议使用有机酸以降低断奶仔猪胃的酸度，据报道这样可以改善生长性能。从喂养有机酸产生的效益包括对病原菌的抑制作用，增加氨基酸和能量的消化率和氮潴留增加。 以前就已经发现在日粮中含低水平乳制品时有机酸的反应最大。乳制品中含有的乳糖可发酵产生乳酸，降低肠道pH值。此外，乳制品中的蛋白质在未成熟肠道中比植物蛋白更容易消化。当给断奶前的仔猪采用渐变方式饲喂渐变饲料后，仔猪断奶后添加日粮酸化剂的效果可能会降低。断奶前采用渐变饲喂方式可刺激胃酸和消化酶的分泌，促进断奶后仔猪的生长。

Unexpectedly, Lawlor et al. (2005a) found that the response to a dietary acid was not influenced by the level of dairy product in the diet or whether pigs had or had not been creep fed while suckling the sow. Feed intake in one experiment was increased by ~32% in week 1 and by 11% over the first 3 weeks after weaning due to the dietary addition of fumaric acid. This increase in feed intake translated into a ~20% increase in growth rate in the first 3 weeks post-weaning. However, the response to diet acidification was not always consistent between experiments with a response to fumaric acid seen in 2 of the 3 experiments reported and the magnitude of the response varied greatly between the two experiments where a positive response was found. Similar results were found in later work (Lawlor et al., 2006). It was thought that microbial challenge during the post-weaning period has a major influence on the response to fumaric acid supplementation.

没想到，劳勒等人（2005）发现，对日粮酸的反应并不受哺乳期饲料是否有乳制品及其水平的影响。在一个实验中，由于在饲料中添加富马酸，在断奶后第一周采食量量增加32%，前三周采食量增加11%。前三周采食量的增加转化为前3周的生长速度提高20%。然而，在三个添加富马酸的试验中有2个报道不一致，所以断奶仔猪日粮中添加富马酸的反应并不总是一致的。后来的研究也发现了类似的结果（劳勒等，2006）。所以认为，断奶后微生物挑战对添加富马酸的效果有主要影响。

Table 9. Effect of pre-weaning creep feeding on response of weaned pigs to dietary fumaric acid (Lawlor et al 2005a)

       表9断奶前料过渡对断奶仔猪日粮富马酸反应的影响（劳勒等人，2005）

                                                        标准误差       F检验

蠕变                      否      否       是       是              添加富马酸

富马酸（富马酸；克/千克） 0       20       0        20

猪体重（千克）

断奶                     6.1    6.1      6.2      6.0       0.31         

结果                    12.1    12.9     11.9     13.6      0.67       **

采食量（克/天）

第一周                  194    233      180      260        19.0       ***

第二周                  528    550      533      623        46.0      

第三周                  658    696      667      711        43.7

总量                    466    500      466      535        30.3       *

日增重（克/天）

总量                    289    320      273      358         23.6      **

断奶后微生物挑战对添加富马酸的效果有主要影响。

An alternative approach to diet acidification, which can yield similar benefits, is to formulate post-weaning diets to have a low acid binding capacity. Acid binding capacity can be defined as the amount of acid in milliequivalents (meq) of Hydrochloric acid required to lower the pH of 1kg of feed sample to (a) pH 4.0 (ABC-4) and (b) pH 3.0 (ABC-3) (Lawlor et al 2005b). The lower the acid-binding capacity of the feed, the lower the amount of gastric acid that is required to lower its pH and create an acidic environment in the stomach, which is beneficial to pig health and digestion. Lawlor et al. (2005b) published a data set of acid-binding capacity values for a wide range of feed ingredients. There is great variation between ingredients with regard to acid-binding capacity values. For this reason, complete post-weaning diets can be formulated to have a low acid-binding capacity by selection of ingredients from this dataset with low acid-binding capacity and by using the acid-binding capacity value for each ingredient in the diet formulation matrix. Such diets can be used when a high gastric pH is likely to be a problem (e.g., at weaning) and as an effective alternative to diet acidification. When such diets were formulated by reducing calcium and phosphorus content in the diet formulation, feed intake in the first week after weaning was increased by 17% (Lawlor et al., 2006). This is the time where we need to increase feed intake as it has such an influence on subsequent growth performance.

日粮酸化的另一种方法可以产生类似的效益，这个方法就是制定断奶后的日粮配方时使之具有较低的酸结合力。酸结合能力可以定义为，为降低一千克饲料样品的PH到（a）pH 4（abc-4）和（b）pH 3（abc-3）所需的盐酸的毫克当量（劳勒等人，2005）。饲料的酸结合能力越低，为降低胃中饲料的PH一创建胃中的酸环境所需要的胃酸就越少，这有利于猪的健康和消化。劳勒等人（2005b）公布了一组范围广泛的饲料原料的酸结合力值。就酸结合力值而言，不同饲料原料之间的变异很大。因为这个原因，在设计断奶后仔猪日粮时，根据这祖酸结合力数据选择原料，使用每一种饲料原料的酸结合力设计饲料配方，可以配合出酸结合力低的断奶后配合饲料。如果存在高胃PH问题（例如断奶时），就可以用这种日粮，这是日粮酸化的一种有效替代方法。通过减少饲料配方中钙和磷的含量设计出这种日粮时，断奶后第一周的采食量增加了17%（劳勒等人，2006）。这个时候需要增加采食量，因为这时的采食量影响后续生长性能。

5.4. Probiotics

Probiotics are ‘live microorganisms which when administered in adequate amounts confer a health benefit on the host’ (FAO/WHO, 2001). They offer potential as an alternative to antibiotics for pigs, both as a means of controlling enteric pathogens and improving growth performance. Their possible modes of action include modulation of the immune system, competitive exclusion of pathogens in the gut and antimicrobial production. Prieto et al. (2014) evaluated the safety and efficacy of a marine-derived Bacillus pumilus strain for use as an infeed probiotic in newly weaned pigs. The B. pumilus used was pre-screened and selected for its ability to inhibit porcine pathogenic E. coli (Prieto et al., 2013). The Bacillus strain was administered to weaned pigs fed a non-medicated diet and compared to a negative control treatment without antibiotic or pharmacological levels of zinc oxide (non-medicated treatment) and a positive control treatment containing apramycin and pharmacological levels of zinc oxide (medicated treatment). The study herd was at the time experiencing oedema disease during the post-weaning period. The B. pumilus strain decreased ileal E. coli counts in a manner similar to the medicated treatment but without the reduction in growth performance (Table 10) and possible liver toxicity found with the medicated treatment (Prieto et al., 2014).

益生菌是“活的微生物，当给予足够量的时候，就能对机体产生益处（FAO/WHO，2001）”。他们用于猪，具有替代抗生素的潜力，无论是作为控制肠道致病菌的手段还是提高猪的生长性能。其可能的作用方式包括免疫系统的调制，在肠道内与病原菌的竞争排斥。普列托等人。（2014）评估了一个来自海洋的短小芽孢杆菌菌株作为益生菌在断奶仔猪料的安全性和使用效能。使用的B. pumilus是预筛选的，并且选择培育了其抑制猪致病性大肠杆菌的能力（普列托等人，2013）。把该菌株用于饲喂断奶仔猪，这些仔猪使用无药日粮，一个负的对照祖使用无抗生素或药物治疗剂量的氧化锌（非药物处理组），一个正的对照处理含安普霉素和氧化锌药理水平（药物处理组）。研究群在断奶后出现水肿病。B. pumilus菌株降低了回肠大肠杆菌计数，在某种方式看类似于药物处理，但没有生长性能下降（表10），并且药物处理组发现了可能有肝毒性（普列托等人.，2014）。

Table 10. Effect of feeding non-medicated, medicated or B. pumilus treatments for 22 days on post-weaning pig growth performance1,2 (Prieto et al., 2014)

表10.非药物处理、药物处理22天或短小芽孢杆菌处理对断奶猪生长性能的影响1,2（普列托等，2014）

            

                      非药物处理  药物处理 短小芽孢杆菌处理   标准误差    P值

_______________________________________________________________________           

第0天体重3（千克）   8.7       8.6         8.8          0.26      0.38

第22天体重（千克）  18.1      17.6        18.7          0.35      0.07

平均日采食量4（克/天）471      458         475           12.6      0.53

平均日增重5（克/天） 427      405         455           15.7      0.07

饲料转化率6        1.11ab       1.14a        1.05b          0.023      0.04

1 平均值及其标准误差。2同一行数字中，上标字母不同的数字表示有显著差异（P＜0.05）3BW=体重 4ADFI=平均日采食量，断奶至22天后。5ADG=平均日增重，断奶至22天后。6FCR=饲料转化率（平均日采食量/ 平均日增重）断奶至22天后。

Casey et al. (2007) investigated the effects of oral treatment of pigs with a mixture of five lactic acid bacteria probiotic strains, on both clinical and microbiological signs of Salmonella Typhimurium infection. Following probiotic administration for 6 days, animals were challenged orally with S. Typhimurium and monitored for 23 days post-infection. Animals treated with probiotic showed reduced incidence, severity, and duration of diarrhea, gained weight at a faster rate than control pigs, and had reduced fecal shedding of Salmonella

凯西等（2007）研究了用五株乳酸菌益生菌合剂口服处理的影响，考察临床和沙门氏菌感染微生物的迹象。益生菌处理6天后，动物口服鼠伤寒沙门菌，感染后23天检测。用益生菌处理的动物表现出腹泻发病率极度降低且发生拉稀的程度也很弱，体重增加的速度比对照猪快，并减少了粪便中的沙门氏菌

5.6. Prebiotics

Prebiotics, like probiotics, are used as a strategy to influence the composition of the gastrointestinal microflora towards a more favorable balance, by reducing the amount of harmful/pathogenic species and promoting the growth of species thought to have beneficial effects on host health (O’Sullivan et al., 2010). A prebiotic is “a selectively fermented ingredient that allows specific changes, both in the composition and/or activity of the gastrointestinal microflora that confers benefits upon the host wellbeing and health”. Prebiotics are resistant to digestion in the upper gut (i.e. resistant to acid and enzymes), a selective substrate for the growth of beneficial bacteria and able to induce luminal or systemic effects that are beneficial to host health. To date only inulin, oligofructose, galactooligosaccharides and lactulose are considered true prebiotics; however, other potential sources of prebiotics such as seaweed-derived compounds are currently being explored (O’Sullivan et al., 2010).

5.6 益生元

益生元，与益生菌相似，可以作为影响胃肠道微生物区系组成的策略，使之向着更加有益的方向平衡，作用途径是减少有害病原菌种类数量，促进对宿主健康有益的微生物物种生长(奥沙利文等，2010)。益生元是“选择性发酵成分，其允许发生特定变化，包括胃肠道微生物的组成和活性两种变化，这些变化有益于宿主生存和健康”。益生元在上部肠道抗消化（即耐酸和酶），是有益于有益菌生长的物质，这些有益菌有利于宿主健康。到目前为止只有菊粉，低聚果糖，低聚半乳糖和乳果糖被认为是真正的益生元；然而，其他潜在的益生元如海藻衍生的化合物目前正在探索（奥沙利文等人.，2010）.