Lactation response to soybean meal and rumen-protected methionine supplementation of corn silage-based diets

Abstract

Corn silage, an important forage fed to dairy cows in the United States, is energy rich but protein poor. The objectives of this experiment were to investigate the effects on production of milk and milk components of feeding corn silage-based diets with 4 levels of dietary crude protein (CP) plus rumen-protected methionine (RPM). Thirty-six cows were blocked by days in milk into 9 squares and randomly assigned to 9 balanced 4 × 4 Latin squares with four 4-wk periods. All diets were formulated to contain, as a percent of dry matter (DM), 50% corn silage, 10% alfalfa silage, 4% soyhulls, 2.4% mineral-vitamin supplement, and 30% neutral detergent fiber. Supplemental RPM (Mepron, Evonik Corp., Kennesaw, GA) was added to all diets to maintain a Lys:Met ratio of 3.1 in digested AA. Ground high-moisture corn was reduced and soybean meal (SBM) plus RPM increased to give diets containing, on average, 11% CP (28% corn, 31% starch, 6% SBM, 4 g of RPM/d), 13% CP (23% corn, 29% starch, 10% SBM, 8 g of RPM/d), 15% CP (19% corn, 26% starch, 15% SBM, 10 g of RPM/d), and 17% CP (14% corn, 24% starch, 19% SBM, 12 g of RPM/d). Data from the last 14 d of each period were analyzed using the mixed procedures in SAS (SAS Institute Inc., Cary, NC). With the exception of milk fat and milk lactose content, we found no significant effects of diet on all production traits. We did note linear responses to dietary CP concentration for intake, production of milk and milk components, and MUN. Cows fed the 11% CP diet had reduced DM intake, lost weight, and yielded less milk and milk components. Mean separation indicated that only true protein yield was lower on 13% CP than on 17% dietary CP, but not different between 15 and 17% CP. This indicated no improvement in production of milk and milk components above 15% CP. Quadratic trends for yield of milk, energy-corrected milk, and true protein suggested that a dietary CP concentration greater than 15% may be necessary to maximize production or, alternately, that a plateau was reached and no further CP was required. Although diet influenced apparent digestibility of DM, organic matter, and neutral detergent fiber, digestibility did not increase linearly with dietary CP. However, we observed linear and quadratic effects of dietary CP on acid detergent fiber digestibility. As expected, we found a linear effect of dietary CP on apparent N digestibility and on fecal and urinary N excretion, but no effect of diet on estimated true N digestibility. Ruminal concentrations of ammonia, total AA, peptides, and branched-chain volatile fatty acids also increased linearly with dietary CP. Quadratic responses indicated that 14.0 to 14.8% CP was necessary to optimize digestion and energy utilization. Overall results indicated that, when RPM was added to increase Lys:Met to 3.1, 15% CP was adequate for lactating dairy cows fed corn silage diets supplemented with SBM and secreting about 40 kg of milk/d; N excretion was lower than at 17% CP but with no reduction in yield of milk and milk components.

Effects of supplementing limiting amino acids on milk production in dairy cows consuming a corn grain and soybean meal-based diet

“…The levels of essential AA and crude protein in the diets significantly affect dry matter intake. These are also affected when there is a large difference between the AA level in feed and the amount of AA required by the animal [ 12 , 23 – 26 ]. It is notable that a significant proportion of corn grain was used as a source of feed ingredient in this study.…”

“…Methionine [ 3 , 7 ] and lysine [ 8 , 9 ] are widely known as first-limiting AAs, which affect the milk production and milk protein of dairy cows under many dietary regimes. In addition, lysine and methionine have long been regarded as potentially rate-limiting factors for milk production, either alone or in combination [ 6 , 10 – 12 ]. The production responses to dairy cows can be greater when methionine, used in combination with lysine, is directed into the small intestine and bloodstream [ 13 , 14 ].…”

Effects of Supplementing Rumen-Protected Methionine on Production Performance, Apparent Digestibility, Blood Parameters, Ruminal Metabolites and Economic Effectiveness in Lactating Holstein Dairy Cows

“…There was a trend for lower SNF with decreased CP feeding and RPM supplementation (P = 0.09). [19], from 13-17% [9]. Moreover, several trials have demonstrated that with RPM supplementation, milk yield [10,20] and milk protein yield [21] increased.…”

“…Recently years, there have been some research that explored the effects of rumenprotected methionine (RPM) supplementation on dairy cows. Several studies indicated that RPM supplementation and decreasing dietary CP could increase milk production, milk protein, fat as well as lactose contents [7][8][9][10]. Recently research has shown that an increase in overall dry matter intake (DMI) could be found after parturition when cows fed lower dietary CP and RPM [11].…”

Symposium review: Decomposing efficiency of milk production and maximizing profit

“…Efficiency of protein utilization (the proportion of CP consumed that is recovered in milk protein) in dairy cattle ranges between 18 to 19 (Penner et al, 2009;Rhoads et al, 2009) and 42 to 44% (Nursoy et al, 2018;Nichols et al, 2019). Differences in efficiency of protein utilization also seem to be affected by the level of production.…”