國產燕麥作為反芻動物芻料來源之適用性評估

Abstract

台灣冬季存在牧草短缺的困境，且由於酪農普遍生產成本偏高，而種植國產牧草則是其中一個可以解決這種困境的方法之一。優良的國產牧草以高營養價值作為重要的考量因素。其中，燕麥是牧草作物中營養價值較高的一種牧草，它具有較高粗蛋白質與非纖維碳水化合物，其需水量較少的特性，也可符合台灣中南部冬季較乾旱的環境，因此本論文以燕麥作為國產芻料的研究對象。 本論文共有三階段試驗。第一階段為利用近似分析評估不同品種國產燕麥為國內芻料來源之適用性，試驗選用八個燕麥品系(NTU sel No.1、Swan、26、30、33、39、43及44)，於台灣北中南三個地區(台北、彰化及屏東)進行種植試驗，於進入糊熟期時收集各地區各品種之全株樣品進行營養成分分析，並配合體外消化試驗評估各地區適合栽種利用之燕麥品系。先透過產量資料與成分近似分析結果，再依據較低中洗纖維(neutral detergent fiber, NDF)及較高粗蛋白質(crude protein, CP)含量以選出各地區合適使用的兩個品種。結果顯示，北部之燕麥樣品具有較高之NDF含量但是CP較低。北中南地區之NDF%範圍分別為60-66%、57-62%及50-56%。在CP％部分，北中南地區分別為8-10%、9-11%及8-12%。依照設定需求，在北部地區選擇品系NTU sel No.1 (NDF = 60.74 %, CP = 10.99%)及43 (NDF = 64.17%, CP = 10.98%)、中部地區選擇品系43 (NDF = 59.18%, CP = 10.15 %)及44 (NDF = 59.87%, CP = 11.13%)、南部地區選擇品系33 (NDF = 52.01 %, CP = 12.20%)及43 (NDF = 50.51%, CP = 10.22%)。第二階段以所選擇的燕麥品系進行48小時體外消化率與產氣發酵試驗，消化率結果顯示，在北部地區，NTU sel No.1的消化率顯著高於43 (72.85% vs. 69.09 %)。但是中部地區的品系43與44 (65.18 % vs. 64.42 %)及南部地區的33與43 (69.93 % vs. 69.83 %)則在消化率上無顯著差異。由本試驗資料可了解，NTU sel No.1在北部地區可能較適合進行後續栽培利用，而中部地區則是品系43或44均適合，屏東地區則可考慮栽植33及43兩個品系供後續利用。 了解燕麥的營養組成分與體外消化試驗結果後，最後，透過第三部分替代性試驗，評估國產燕麥是否具有取代進口燕麥的價值。處理組分別為北部地區品系NTU sel No.1與43，中部地區43與44，南部地區33與43，該6個品系皆取代商用完全混合日糧(total mixed ration, TMR)中之進口甜燕麥的0、30、65與100%，其中。結果顯示，北部、中部與南部地區的國產燕麥，任一取代比例均不會對消化率、揮發性脂肪酸等造成負面影響，甚至消化率顯著高於控制組。 國產燕麥是個具有高營養價值的芻料來源，而經過體外消化試驗與取代率試驗，可以得知TMR中使用國產燕麥對消化率並無負面影響。相較於進口燕麥價格，國產燕麥較低廉，因此可使酪農生產成本下降。綜合上述試驗結果，以燕麥作為國產芻料對象是個具有潛力的發展方向。

There was a shortage of forage source in winter of Taiwan. In order to compensate for the high price imported hay, many domestic forage crops with high feeding value had been investigated. Among them, oats had the highest levels of crude protein (CP) and water-soluble carbohydrate (WSC). The less water demand of oat was an advantageous to be cultivated in fallow land in Central and South Taiwan during winter. Therefore, we adopted domestic oats as the target forage in this study. The first stage experiment attempted to find out suitable cultivars for cultivating in three areas of Taiwan by examing the nutrient composition and the in vitro digestion performance. Eight cultivars of oats (NTU sel No.1, Swan, 26, 30, 33, 39, 43 and 44) were cultivated in north (Taipei), center (Changhua) and south (Pingtung) areas. According to yield and nutrient composition results, two suitable cultivars were selected from each area for further study. In Taipei, NTU sel No.1 had the highest CP (>11%) and non-fiber carbohydrate (NFC, 16.1%) among all strains. Similarly, 43 had high CP (10.9%) and the lowest acid detergent fiber (ADF, 36.6%). In Changhua, both 43 and 44 cultivars showed lower ash (9.9% and 8.6%, respectively) and higher NFC (18.3% and 18.1%, respectively) than other strains. In Pingtung, all strains had high levels of NFC than other area samples. When NFC exceeds 20%, the crop would be regarded as an excellent species in the midst of forages. The result in Pintung indicated that strain 33 and 43 had the lowest ADF (26.7% and 26.2%, respectively). The strain 33 also had the highest CP content (12.2%). According to the proximate analysis results, the cultivars km and 43, 43 and 44, 33 and 43 were chosen for cultivation in Taipei, Changhua and Pingtung, respectively. The in vitro digestion test was used to investigate the fermentation ability of selected oats. The test result indicated that oats from center area showed poor fermentation performance, including lower in vitro dry matter digestibility (IVDMD), gas production rate and volatile fatty acid (VFA) concentration. However, the oats harvested from south area showed the best fermentable performance than others. In the second experiment, the imported oats in total mixed ration (TMR) was replaced by domestic oats under different replacing ratio (0%, 30%, 65% and 100%) for in vitro fermentation test. The result indicated that no negative effect on IVDMD or VFA production was shown after domestic oats replacing treatment. It represented that domestic oats had high potential to replace imported oats. In conclusion, according to the feeding value evaluation result and domestic cost advantage, domestic oats could be an excellent alternative crop for ruminant winter feeding in Taiwan.