Search

An experiment was conducted to evaluate the effect of type of corn endosperm on nutrient digestibility in lactating dairy cows. Near-isogenic variants of an Oh43 × W64A normal dent endosperm hybrid carrying floury-2 or opaque-2 alleles were grown in spatial isolation in field plots and harvested as dry shelled corn. Six ruminally cannulated, multiparous Holstein cows (67 ± 9 d in milk at trial initiation) were randomly assigned to a replicated 3 × 3 Latin square design with 14-d periods; the first 11 d of each period were for diet adaptation followed by 3 d of sampling and data collection. Treatment diets that contained dry rolled vitreous-, floury-, or opaque-endosperm corn [33% of dry matter (DM)], alfalfa silage (55% of DM) and protein-mineral-vitamin supplement (12% of DM) were fed as a total mixed ration. The percentage vitreous endosperm was zero for floury and opaque endosperm corns and 64 ± 7% for the vitreous corn. Prolamin protein content of floury and opaque endosperm corns was 30% of the content found in vitreous corn. Degree of starch access and in vitro ruminal starch digestibility measurements were 32 and 42% greater on average, respectively, for floury and opaque endosperm corns than for vitreous corn. Dry matter and starch disappearances after 8-h ruminal in situ incubations were, on average, 24 and 32 percentage units greater, respectively, for floury and opaque endosperm corns than for vitreous corn. Ruminal pH and acetate molar percentage were lower, propionate molar percentage was greater, and acetate:propionate ratio was lower for cows fed diets containing floury and opaque endosperm corns than for cows fed vitreous corn. In agreement with laboratory and in situ measurements, total-tract starch digestibility was 6.3 percentage units greater, on average, for cows fed diets containing floury and opaque endosperm corns than vitreous corn. Conversely, apparent total-tract neutral detergent fiber (NDF) digestibility was lower for cows fed diets containing floury and opaque endosperm corns compared with vitreous corn. The type of endosperm in corn fed to dairy cows can have a marked effect on digestion of starch and NDF. Feeding less vitreous corn increased starch digestion but decreased NDF digestion. [ABSTRACT FROM AUTHOR]

In this experiment, we evaluated the influence of increasing chop length and mechanical processing of whole-plant brown-midrib corn silage on intake, digestion, and milk production by dairy cows. Corn silage treatments were harvested at three-quarter milk line stage of maturity at 13- and 19-mm theoretical chop length without processing, or at 19- and 32-mm theoretical chop length with processing at a 2-mm roll clearance. Twenty-four multiparous Holstein cows that averaged 102 +/- 17 d in milk at trial initiation were randomly assigned to treatments in a replicated 4 x 4 Latin square design with 28-d periods. Preplanned orthogonal contrasts were used to evaluate effects of processing (19 processed vs. 19 mm unprocessed) and chop length (13 vs. 19 mm unprocessed and 19 vs. 32 mm processed). Treatments were fed in total mixed rations containing 60% forage (67% corn silage and 33% alfalfa silage) and 40% shelled corn and soybean meal-based concentrate (dry matter basis). Milk yield was unaffected by treatment. Dry matter intake was unaffected by corn silage processing, but increasing corn silage chop length reduced dry matter intake in unprocessed (26.6 vs. 25.5 kg/d) and processed (25.9 vs. 25.1 kg/d) chop length contrasts. Processing reduced milk fat content (3.36 vs. 3.11%) and yield (1.43 vs. 1.35 kg/d), increased total-tract starch digestion (92.9 vs. 97.4%), and decreased total-tract neutral detergent fiber digestion (51.0 vs. 41.8%). Total chewing time (min/d) was unaffected by treatment. Masticate mean particle length was unaffected by chop length in unprocessed and processed corn silage treatments. In this study with brown-midrib corn silage fed to dairy cows producing 43 kg/d of milk, there were no benefits from crop processing or increasing chop length on lactation performance.

Three corn hybrids harvested as whole-plant silage were evaluated in three separate feeding trials with lactating dairy cows. In trial 1, 24 multiparous Holstein cows were used in a replicated 4 x 4 Latin square with 28-d periods. Treatments were conventional (Pioneer 3563) and leafy (Mycogen TMF 106) corn silage hybrids, each planted at low (59,000 plants/ha) and high (79,000 plants/ha) plant populations. There were no milk production differences between treatments. Total-tract digestibility of dietary starch was higher for leafy compared with conventional corn hybrids. In trial 2, 26 multiparous Holstein cows were assigned randomly to diets containing either conventional (48% forage diet) or brown-midrib (60% forage diet) corn silage in a crossover design with 8-wk periods. Milk yield was lower, but milk fat percentage and yield were higher, for the high-forage diet containing brown-midrib corn silage. In trial 3, 24 multiparous Holstein cows were used in a replicated 4 x 4 Latin square with 28-d periods. Treatments were corn silage at two concentrations of neutral detergent fiber (Garst 8751, 39.2% NDF; Cargill 3677, 32.8% NDF) each fed in normal- (53% of dry matter) and high- (61 to 67% of dry matter) forage diets. Milk production was not different between corn hybrids. Increased concentrate supplementation increased DMI and milk production. There were minimal benefits to the feeding of leafy or low-fiber corn silage hybrids. Feeding brown-midrib corn silage in a high-forage diet increased milk fat percentage and yield compared with conventional corn silage fed in a normal-forage diet.

Effects of corn silage crop processing and chop length on intake, digestion, and milk production were evaluated. Corn silage treatments were harvested at one-half milkline stage of maturity (65% whole-plant moisture content) and at 0.95-cm theoretical length of cut without processing (control) or 0.95-, 1.45-, or 1.90-cm theoretical length of cut with processing at a 1-mm roll clearance. Twenty-four multiparous Holstein cows averaging 71 d in milk at trial initiation were in a replicated 4 x 4 Latin square design with 28-d periods; one square was comprised of ruminally cannulated cows for rumen measurements. Corn silage treatments were fed in total mixed rations containing 50% forage (67% corn silage and 33% alfalfa silage) and 50% corn and soybean meal based concentrate (dry matter basis). Dry matter intake (25.9 vs. 25.3 kg/d) and milk (46.0 vs. 44.8 kg/ d) and fat (1.42 vs. 1.35 kg/d) yields were higher for the processed corn silage treatments compared with the control corn silage. Within the processed corn silage treatments, there were no chop length effects on intake, milk production, or milk composition. Chewing activity was not different among the four corn silage treatments averaging 12 h/d. Total tract digestion of dietary starch was lower for control corn silage (95.1%) compared with fine, medium, and coarse processed corn silage treatments, which averaged 99.3%. Total tract digestion of dietary NDF was reduced for fine-processed corn silage compared with control corn silage and coarse-processed corn silage (28.4% vs. 33.9 and 33.7%, respectively). Processing corn silage improved dry matter intake, starch digestion, and lactation performance. Under the conditions of this study and with theoretical lengths of cut ranging from 0.95 to 1.90 cm, length of chop effects were minimal in processed corn silage.

Whole-plant corn was harvested at early dent, quarter milkline, two-thirds milkline, and black layer stages to evaluate the effects of maturity on intake, digestion, and milk production when corn was fed as silage in the diet. Twenty multiparous Holstein cows were used in a replicated experiment with a 4 x 4 Latin square design with 28-d periods. Diets containing 50% forage (67% corn silage and 33% alfalfa silage) and 50% concentrate (dry matter basis) were fed as total mixed rations. Moisture contents were 69.9, 67.6, 64.9, and 58.0% for silages from corn harvested at early dent, quarter milkline, two-thirds milkline, and black layer stages, respectively. Intakes of dry matter were similar across the four treatments and ranged from 3.73 to 3.79% of body weight. Milk production was highest (33.4 kg/d) for cows fed silage from corn harvested at the two-thirds milkline stage and lowest (32.4 kg/d) for cows fed silage from corn harvested at the early dent stage. Milk protein production was highest for cows fed silage from corn harvested at the two-thirds milkline stage (1.17 vs. 1.12 to 1.13 kg/d). Apparent total tract digestion of dry matter, organic matter, crude protein, acid detergent fiber, and starch was lowest for cows fed silage from corn harvested at the black layer stage. Although starch intake was similar for cows fed silage from corn harvested at the two-thirds milkline stage and for cows fed silage from corn harvested at the black layer stage (9 kg/d), intake of digestible starch was 0.4 kg/d lower for cows fed silage from corn harvested at the black layer stage. The optimum stage for corn that was ensiled was two-thirds milkline with some flexibility between quarter and two-thirds milkline.