|Jung, Hans Joachim|
|Phillips, Ronald -|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 27, 2011
Publication Date: October 1, 2011
Repository URL: http://hdl.handle.net/10113/50345
Citation: Jung, H.G., Mertens, D.R., Phillips, R.L. 2011. Effect of reduced ferulate-mediated lignin/arabinoxylan cross-linking in corn silage on feed intake, digestibility, and milk production. Journal of Dairy Science. 94(10):5124-5137. Interpretive Summary: Corn silage is the most important forage for dairy cows, but the stover in silage has high fiber content and is of limited digestibility. The poor digestibility of corn silage fiber reduces the biological and economic efficiency of milk production. Previous research has demonstrated that cross linking of the carbohydrates in plant fiber to lignin, an inhibitor of digestion, is critical to lignin's inhibitory effect on fiber digestibility when measured in a laboratory assay. A mutation was discovered in corn that reduces fiber cross linking and improves laboratory digestibility. The current study examined the impact of this corn mutation on dairy cow performance. Holstein cows fed the mutant corn silage as part of a typical mixed diet of silage and grains consumed more feed, produced more milk, and had greater fiber digestibility than cows fed control corn silage. Cows were also less selective against fiber in the feed they consumed, thereby reducing feed wastage. Research is underway to identify the gene responsible for the low cross linking mutation. Commercial corn hybrids incorporating this low cross linking mutation should increase the efficiency of milk production.
Technical Abstract: Cross linking of lignin to arabinoxylan by ferulates limits in vitro rumen digestibility of grass cell walls. Impact of ferulate cross linking on DMI, milk production, and in vivo digestibility was investigated in ad libitum and restricted intake digestion trials with lambs, and in a dairy cow performance trial using the low-ferulate sfe corn mutant. Silages of five inbred corn lines were fed: W23, two W23sfe lines (M04-4 and -21), B73, and B73bm3. As expected, W23sfe silages contained fewer ferulate ether cross links and B73bm3 silage had a lower lignin concentration than their respective genetic controls. Silages were fed as the sole ingredient to four lambs per silage treatment. Lambs were confined to metabolism crates and fed ad libitum for a 12-d adaptation period followed by a 5-d collection period of feed refusals and feces. Immediately following the ad libitum feeding trial, silage offered was limited to 2% of body weight. After a 2-d adaptation to restricted feeding, feed refusals and feces were collected for 5 d. Seventy Holstein cows were blocked by lactation, DIM, BW, and milk production and assigned to TMR diets based on the five corn silages. Diets were fed for 28 d and data were collected on weekly DMI, milk production, and milk composition. Fecal grab samples were collected during the last week of the lactation trial for estimation of feed digestibility using acid-insoluble ash as a marker. Silage, TMR, feed refusal, and fecal samples were analyzed for CP, starch, NDF, cell wall polysaccharides, and lignin. W23sfe silages resulted in lower DMI in the ad libitum trial than W23 fed lambs, but DMI did not differ in the restricted trial. No differences were observed for NDF or cell wall polysaccharide digestibility by lambs with restricted feeding, but amount of NDF digested daily increased for lambs fed the M04-21 W23sfe silage ad libitum. Lambs were less selective against NDF and lignin when offered W23sfe silages. B73bm3 silage did not affect DMI or digestibility of cell walls at the restricted feeding level, but total daily NDF digested was greater at ad libitum intake. Intake, milk production, and cell wall digestibility were greater for cows fed diets containing W23sfe silages than W23. Although milk production was greater for B73bm3 diets, DMI and cell wall digestibility were not altered. Cows were less selective against cell wall material when fed both W23sfe and B73bm3 silages. Reduced ferulate cross linking in sfe corn silage is a new genetic mechanism for improving milk production.