Transformation with TT8 and HB12 RNAi Constructs in Model Forage (Medicago sativa, Alfalfa) Affects Carbohydrate Structure and Metabolic Characteristics in Ruminant Livestock Systems.
Lignin, a phenylpropanoid polymer present in secondary cell walls, has a negative impact on feed digestibility. TT8 and HB12 genes were shown to have low expression levels in low-lignin tissues of alfalfa, but to date, there has been no study on the effect of down-regulation of these two genes in alfalfa on nutrient chemical profiles and availability in ruminant livestock systems. The objectives of this study were to investigate the effect of transformation of alfalfa with TT8 and HB12 RNAi constructs on carbohydrate (CHO) structure and CHO nutritive value in ruminant livestock systems. The results showed that transformation with TT8 and HB12 RNAi constructs reduced rumen, rapidly degraded CHO fractions (RDCA4, P = 0.06; RDCB1, P < 0.01) and totally degraded CHO fraction (TRDCHO, P = 0.08). Both HB12 and TT8 populations had significantly higher in vitro digestibility of neutral detergent fiber (NDF) at 30 h of incubation (ivNDF30) compared to the control (P < 0.01). The TT8 populations had highest ivDM30 and ivNDF240. Transformation of alfalfa with TT8 and HB12 RNAi constructs induced molecular structure changes. Different CHO functional groups had different sensitivities and different responses to the transformation. The CHO molecular structure changes induced by the transformation were associated with predicted CHO availability. Compared with HB12 RNAi, transformation with TT8 RNAi could improve forage quality by increasing the availability of both NDF and DM. Further study is needed on the relationship between the transformation-induced structure changes at a molecular level and nutrient utilization in ruminant livestock systems when lignification is much higher.
College of Agriculture and Bioresources, University of Saskatchewan , 51 Campus Drive, Saskatoon, Saskatchewan, Canada S7N 5A8.|College of Animal Science and Technology, Northeast Agricultural University , Harbin 150030, China.
Xinxin
X
Li
College of Animal Science and Technology, Northeast Agricultural University , Harbin 150030, China.
Yonggen
Y
Zhang
Agriculture and Agri-Food Canada, 1391 Sandford Street, London, Ontario, Canada N5V 4T3.
Abdelali
A
Hannoufa
College of Agriculture and Bioresources, University of Saskatchewan , 51 Campus Drive, Saskatoon, Saskatchewan, Canada S7N 5A8.|Tianjin Agricultural University , Tianjin 300384, China.
Peiqiang
P
Yu
D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D004043:Dietary Fiber / Q000032:analysis / Q000378:metabolism; D004063:Digestion; D030841:Food, Genetically Modified; D008031:Lignin / Q000737:chemistry* / Q000378:metabolism; D058751:Livestock / Q000378:metabolism*; D000455:Medicago sativa / Q000235:genetics* / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D012417:Rumen / Q000378:metabolism*; D012418:Ruminants / Q000378:metabolism; D014170:Transformation, Genetic
D004043:Dietary Fiber; D010940:Plant Proteins; D008031:Lignin
HB12; TT8; carbohydrate structure and nutrition; molecular spectroscopy; transformation of alfalfa