Effects of corn grain endosperm type and conservation method on site of digestion, ruminal digestion kinetics, and flow of nitrogen fractions to the duodenum in lactating dairy cows

Effects of corn grain endosperm type and conservation method on feed intake, feeding behavior, and productive performance of lactating dairy cows

“…The lack of effect of endosperm type on ruminal pool size of starch is in contrast to the results reported by Taylor and Allen (2005b) in which floury treatments tended to decrease the pool size of starch in the rumen compared with vitreous treatments because floury, compared with vitreous endosperm, greatly increased the rate of degradation of starch, increasing its ruminal turnover rate despite a slower rate of passage of starch. In the present experiment, floury corn increased rate of starch degradation and decreased the rate of starch passage consistent with the experiment reported by Taylor and Allen (2005b), but the ruminal turnover rate of starch was not affected by endosperm type (Table 2 of Allen and Ying, 2021).…”

“…However, endosperm treatment did not affect ruminal pool size of starch (P = 0.35). Although endosperm treatment did not affect DMI, the increased ruminal pools of DM, OM, NDF, pdNDF, and uNDF 240 for floury compared with vitreous corn is consistent with their tendency to reduce ruminal turnover rate (P ≤ 0.07, Table 2 of Allen and Ying, 2021). The lack of effect of endosperm type on ruminal pool size of starch is in contrast to the results reported by Taylor and Allen (2005b) in which floury treatments tended to decrease the pool size of starch in the rumen compared with vitreous treatments because floury, compared with vitreous endosperm, greatly increased the rate of degradation of starch, increasing its ruminal turnover rate despite a slower rate of passage of starch.…”

“…Increased satiety by HMC compared with DGC and the tendency for decreased hunger by HMC compared with DGC for the floury endosperm treatment indicates that feeding behavior was likely affected by metabolic mechanisms. Apparent digestibility of starch in the rumen was increased by 35% for HMC compared with DGC (82.0 vs. 60.6%, P < 0.001) and by 23% for floury compared with vitreous (78.7 vs. 63.9%, P < 0.001), but apparent total-tract starch digestibility was much less variable, ranging from 95.0 to 98.1% among treatments (Allen and Ying, 2021). Absorbed fuels from the digestion of starch include propionate derived from ruminal fermentation and glucose from starch digestion in the small intestine, which is largely converted to lactate by intestinal tissues (Oba et al, 2004).…”

“…This is the first of 2 articles from 1 experiment that evaluated effects of corn grain endosperm type and conservation method. This article describes treatment effects on feed intake, feeding behavior, ruminal fermentation, and milk production, and the companion article focuses on site of digestion, ruminal kinetics, and flow of nitrogen (N) fractions to the duodenum (Allen and Ying, 2021). This study was conducted at the Michigan State University Dairy Cattle Research and Teaching Center (East Lansing, MI), with all experimental procedures approved by the Michigan State University Institutional Animal Care and Use Committee (AUF 09/01-146-00).…”

“…Control of DMI is increasingly limited by ruminal distention as milk yield increases (Conrad et al, 1964). In addition, the turnover rate of DM (~7.2%/h) and NDF (~3.7%/h) in the rumen (Allen and Ying, 2021) is much lower than in the experiments reported by Oba and Allen (2003b) for DM (~9.3%/h) and NDF (~4.5%/h) and by Taylor and Allen (2005b) for DM (~9.9%/h) and NDF (~4.6%/h).…”