Effect of Corn Silage Hybrid and Metabolizable Protein Supply on Nitrogen Metabolism of Lactating Dairy Cows

Abstract

This experiment was conducted to determine the effects of corn silage hybrid and supply of metabolizable protein (MP) on manure excretion and N metabolism by lactating dairy cows. Eight Holstein cows in midlactation (replicated 4 x 4 Latin square with 21-d periods) were fed 1 of 4 treatments, arranged factorially. Diets contained 55% corn silage made from a dual-purpose hybrid or a brown midrib (BMR) hybrid, and 45% concentrate that contained either a low or high concentration of rumen undegradable protein (altered by the addition of fish meal and treated soybean meal). Crude protein averaged 14.0 and 17.5% and supply of MP averaged 2,360 and 2,990 g/d for the low and high MP treatments (not affected by hybrid). Increasing supply of MP greatly increased urine output and tended to increase total manure output, whereas diets with BMR silage tended to reduce manure output. Increased MP supply increased daily excretion of manure N by 25% (465 vs. 374 g/d), fecal N by 27 g, and urinary N by 64 g. When the effect of N intake was removed, cows fed BMR silage excreted about 15 g/d less N via manure than cows fed the other silage. Rumen ammonia, volatile fatty acid concentrations, and pH were not affected by treatment. Dry matter intake (overall mean = 24.9 kg/d) tended to be increased with increased MP but was not affected by hybrid. Milk production for cows fed BMR was higher than for cows fed the dual-purpose hybrid (36.9 vs. 35.3 kg/d), but because of changes in fat concentration, yield of energy-corrected milk was not affected by treatment. The only interaction observed was increased yield of milk protein when BMR silage was combined with increased supply of MP.

Evaluation of Nitrogen Utilization and the Effects of Monensin in Dairy Cows Fed Brown Midrib Corn Silage

“…The CP content of the DP and bm3 corn silages was similar (9.2% DM) but DP had greater NDF (42.3 ± 5.1 %) and lignin (3.5 ± 0.2 %) content compared with bm3 (NDF = 40.2 ± 3.0 %; lignin = 2.4 ± 0.30%). The lower lignin content of bm3 was expected and was similar to that reproted previously (Oba and Allen, 2000a;Weiss and Wyatt, 2006). As expected, in vitro estimates of NDF digestibility following a 30-h incubation (Table 2) were greater for bm3 corn silage compared with DP corn silage (61.0 vs. 49.1 ± 0.62%), with this difference being similar to that of others (Ebling and Kung, 2004).…”

“…As a consequence of improved fiber digestibility, the amount of available energy may be greater for cows consuming bm3 corn silage compared with those consuming conventional hybrids. However, the extent of energy utilization may be limited because cows fed bm3 silage usually consume more feed (Oba and Allen, 1999;Tine et al, 2001), thus reducing total diet digestibility (Weiss and Wyatt, 2006). Several studies have reported that cows consumed more feed when fed bm3 corn silage compared with an isogenic control (Oba and Allen, 1999;Greenfield et al, 2001;Tine et al, 2001).…”

“…Several studies have reported that cows consumed more feed when fed bm3 corn silage compared with an isogenic control (Oba and Allen, 1999;Greenfield et al, 2001;Tine et al, 2001). Recently, Weiss and Wyatt (2006) demonstrated that cows consuming bm3 corn silage excreted less manure N compared with a dualpurpose control hybrid. These authors suggested that improved fermentability of bm3 corn silage may have increased rumen microbial protein synthesis and N utilization.…”

“…An experiment doing so may provide new knowledge concerning the effects of feeding bm3 corn silage and monensin. Because feeding bm3 corn silage may reduce N excretion (Weiss and Wyatt, 2006) and monensin may reduce fecal N output (Ruiz et al, 2001), an experiment evaluating both of these factors may demonstrate if these effects would be additive in total reducing N excretion. The objectives of this study were to use a factorial arrangement of treatments and to simultaneously evaluate the effects of feeding bm3 corn silage and monensin on N utilization and milk production and composition.…”

Feeding a brown midrib corn silage-based diet to growing beef steers improves growth performance and economic returns

“…Some studies reported a decrease in ruminal pH when BMR was fed Taylor and Allen 2005;Gehman et al 2008). This may have been caused by the increased supply of fermentable substrate in the rumen due to enhanced NDF digestibility of BMR (Weiss and Wyatt 2006).…”