Ruminant Nutrition: General

摘要

The objective of this study was to determine the effect of irrigation on insitu starch digestibility (ISSD) of corn for silage. The study was performedin Kimberly (ID) during the 2018 growing season. Five commercial cornhybrids were planted in a split-plot within a randomized complete blockdesign with 4 blocks. Experimental treatments consisted of a controltreatment with furrow irrigation at planting and 3 more times during cropgrowth (watered, W) and a non-irrigated treatment with furrow irrigationonly at planting (drought, D). When the corn was between 1/4 and 3/4milk-line stage of maturity, ears from 3 plants were harvested from eachplot and shelled by hand. After drying (55°C) to constant weight, kernelswere ground to pass through a 4-mm screen of a cutter mill and placedin porous Dacron bags (3.6 g DM/bag). At 9:30 a.m. of the test day, bagswere immersed within the rumen of 3 cannulated cows fed a totally mixedration (40% corn silage, 7% alfalfa hay, and 53% concentrate mix; DMbasis) and incubated for 0, 4, 8, 12, 24, and 48 h. Once dried, all bags wereweighed and opened, and the residues were re-ground to pass through a1-mm screen of a cyclone mill before starch analysis. In situ starch disappearanceparameters were determined using NLIN procedure of SASaccording to the model ISSD = A + B × [1-e(-k × T)], where A is the digestedstarch at time (T) zero, B is the potentially digested starch, and k is the fractionalstarch digestion rate. Undigestible starch (C) was also determined.Kinetic parameters were contrasted using a mixed model that includedblock (random; 3 df), treatment (fixed; 1 df), block × treatment (random;3 df), hybrid (fixed; 4 df), treatment × hybrid (fixed; 4 df), and the randomresidual error. Whole-plant dry matter concentration was greater for Dcorn than for W corn (36.9 vs. 30.3%; P < 0.01). Water status did not affectfractions A (20.3%; P = 0.16), B (75.9%; P = 0.36), or C (3.8%; P = 0.19),the fractional starch digestion rate (6.7%/h; P = 0.96), or the half-life ofstarch (7.4 h; P = 0.21). In conclusion, under the conditions of this study,water stress had no effects on in situ starch digestibility of corn for silage.