非澱粉多醣含量及酵素添加對豬隻飼糧消化率及臭味排放影響之評估

Abstract

集約化豬肉生產業經常面臨廢棄物的議題，飼糧中過多的蛋白質是造成過多含氮廢棄物的問題，對於現場工作人員以及周遭居民會造成健康的危害。在豬隻飼糧中提高可發酵之非澱粉多醣(non-starch polysaccharide, NSP)可以改變大腸的發酵並促進揮發性脂肪酸(volatile fatty acids, VFA)的生成，並減少微生物發酵產生蛋白質分解所產生的代謝物，然而NSP具有抗營養特性，可經由添加非澱粉多醣酶(NSPase)來減緩其負面效益。

本論文實驗一中，先以體外試驗探討NSP添加量及來源對於發酵之影響，實驗二則以體外試驗探討NSP及酵素添加之影響，最後經動物實驗進行驗證。

實驗一中，飼糧中的NSP設定為中量(M，16.5%)及高量(H，22.0%)，分別使用大豆殼(H)或是甜菜粕(P)來作為NSP來源，調配出五種飼糧: (1) CON = 對照組； MH = 中量NSP－大豆殼組； MP = 中量NSP－甜菜粕組； HH = 高量NSP－大豆殼組； HP = 高量NSP－甜菜粕組。試驗結果顯示，高量之NSP添加會減少模擬胃與小腸消化之體外乾物質消化率(in vitro dry matter digestibility, IVDMD)及接續發酵後之體外全消化道乾物質消化率(in vitro total tract dry matter digestibility, IVTTDMD)。提高NSP會提升最大產氣量與達到1/2最大產氣量之時間，但是整體分解速率下降，發酵結束時每公克殘餘物的揮發性脂肪酸的產生也較低。對發酵產物的影響上，大豆殼添加可降低尿素酶活性，而甜菜粕添加可降低氨態氮(NH3-N)與對甲酚的濃度，但是大豆殼添加對於對體外發酵之對甲酚、吲哚或糞臭素之濃度並沒有影響。

實驗二探討了NSP及酵素添加的影響，測試飼糧包括: CON = 對照組； SBH = 大豆殼組(NSP = 16.5 %)； NSPase = SBH組添加 0.005% NSPase； NSPase+Pro = NSPase添加 0.005% NSPase 和 0.05% 蛋白酶。體外消化結果顯示，大豆殼添加提升NSP所造成的IVDMD降低，在添加酵素後並沒有改善。IVTTDMD在CON組中最高，發酵結果顯示最大產氣量隨著大豆殼的添加而提升，但是降解速率則降低，在NSPase+Pro組中丙酸比例最高，但丁酸的比例在CON組中最高。與CON組相比，SBH組中尿素酶活性及NH3-N濃度並沒有差異，額外添加酵素時使NH3-N及對甲酚都顯著升高，但糞臭素會顯著降低。 動物試驗結果顯示，豬隻生長性能與糞便中總脂肪酸濃度在四組間並無差異，但CON組糞便中個別揮發性脂肪酸比例在第各週間有差異。未添加酵素之SBH組糞便中蛋白酶活性在第四週時最低，且NH3-N、對甲酚、吲哚及糞臭素在第二及四週均低於其他組。與SBH組相比，酵素添加組糞便中有較高的NH3-N、對甲酚及糞臭素。

整合上述體內外試驗結果看，使用體外消化及發酵法可以有效評估改變飼糧特性對於臭味排放之影響，利用體外法可以大大減少動物試驗所需的時間及飼養成本。而添加酵素於高NSP飼糧的效果受到較多因素影響，對於降低排放之臭味並無明顯助益。

The intensification of pork production has always faced critics regarding its waste production and odor emissions. Nitrogenous and odorous emissions from excessive dietary crude protein are the primary cause of odor, causing irritations and health problems to workers and residents living in the vicinity. Available fermentable non-starch polysaccharide (NSP) modifies the fermentative patterns in the large intestine of pigs, promotes VFA (volatile fatty acids) production, and reduces proteolytic metabolites from microbial fermentation. However, NSPs are well known for their anti-nutritive effects. Exogenous enzymes are often supplemented to ameliorate the negative impacts of NSPs.

This thesis aims to investigate the digestibility and fermentation characteristics of different levels and sources of NSPs. A further evaluation of exogenous enzymes on high NSP diets is also performed. Lastly, an animal feeding trial is conducted to validate the results.

The first experiment investigated the effects of levels and sources of NSP. Diet NSP levels were adjusted to medium (M; 16.5 %) and high (H; 22.0 %) relative to control, and soybean hull (H) and sugar beet pulp (P) were chosen as NSP sources. A total of five diets were formulated: (1) CON = control diet; MH = medium NSP soybean hull diet; MP = medium NSP sugar beet pulp diet; HH = high NSP soybean hull diet; HP = high NSP sugar beet pulp diet. High levels of NSP decreased the in vitro (simulation gastric-intestinal phase) dry matter digestibility (IVDMD) and total tract (including fermentation) dry matter digestibility (IVTTDMD). Both max gas production and half-time of asymptote were influenced by level and source, and the degradation rate decreased with the inclusion level of NSP. The result showed a decrease in VFA production per gram of residue with the increasing level of NSP. Urease activity was lowest in both soybean hull diets. Sugar beet pulp inclusion lowered p-cresol and NH3-N concentration and increased indole concentration. Soybean hull supplementation had no effect in altering p-cresol, indole, or skatole during fermentation.

The second experiment investigated the effects of NSP and exogenous enzymes. A total of 4 diets were formulated: CON = control diet; SBH = soybean hull supplemented diet (16.5 % NSP); NSPase = SBH diet supplemented with 0.005 % NSPase; NSPase+Pro = SBH diet supplemented with 0.005 % NSPase and 0.05 % protease. IVDMD and crude protein digestibility decreased in the SBH diet, while supplementing enzymes did not improve digestibility. IVTTDMD was observed highest in the CON diet. Max gas production increased with the inclusion of soybean hull, and the degradation rate was lowered. The molar ratio of propionic acid was highest in the NSPase+Pro diet, while butyric acid was highest in the CON diet. Urease activity and concentrations of NH3-N and indole of SBH diet were not significantly different from CON diet. Exogenous enzyme supplementation significantly increased NH3-N and indole concentrations but decreased the skatole concentration.

The growth performance of pigs did not vary among different diets. The total fecal VFA did not vary among different diets. The molar ratio of VFAs is observed to differ between weeks 2 and 4 in the CON diet. Feces from the SBH diet had a lower protease activity in the fourth week and NH3-N, p-cresol, indole, and skatole concentration in the second and fourth weeks. NSPase and NSPase+Pro diets had increased NH3-N, p-cresol, and skatole compared to the SBH diet on the fourth week.

In conclusion, in vitro digestion and fermentation are accurate and convenient tools for evaluating feed modification and its impact on odor production. Careful feed selection with in vitro methods can significantly reduce the required time and cost otherwise spent on animal trials. The effect of exogenous enzyme supplementation on a high-NSP diet is influenced by many factors and had no significant effect on reducing odor emissions.