Effect of dietary energy source and level on nutrient digestibility, rumen microbial protein synthesis, and milk performance in lactating dairy cows

Abstract

This study was conducted to examine the effects of dietary energy source and level on intake, digestion, rumen microbial protein synthesis, and milk production in lactating dairy cows, using corn stover as a forage source. Eight multiparous Holstein cows, 4 of which were fitted with rumen cannulas, were evaluated in a replicated 4 × 4 Latin square design, with each period lasting 21 d. The cows were randomly assigned into 4 treatment groups: low-energy (LE) ground corn (GC), LE steam-flaked corn (SFC), high-energy (HE) GC, and HE SFC. Changes to ruminal energy degradation rates were induced by feeding the cows diets of either finely ground corn or SFC as components of diets with the same total energy level. Milk yield, milk protein content and yield, and milk lactose yield all increased in response to higher levels of dietary energy, whereas contents of milk fat and lactose were unaffected. Cows fed HE diets had a higher crude microbial protein yield and total-tract apparent digestibility than those receiving LE diets. Milk yield, milk protein yield, and microbial protein yield were also higher when SFC replaced GC as the main energy source for lactating cows fed LE diets. These results suggest that an increased dietary energy level and ruminal degradation rate are beneficial to milk protein production, which we suggest is due to increased yields of microbial proteins, when cows are fed corn stover as a dietary forage source.

Effects of ruminally degradable starch levels on performance, nitrogen balance, and nutrient digestibility in dairy cows fed low corn-based starch diets

“…In this study, cow fed high RDS TMR had higher fecal nitrogen excretion as a proportion of N intake than cows fed low RDS TMR, which could partly explain the lower total tract apparent digestibility of crude protein of cows fed high RDS TMR than low RDS TMR. The observation that total tract digestibility of DM was not affected by the dietary treatments is consistent with previously reported results [32,33]. Although several studies observed that the digestibility of DM increased when cows were fed more ruminally degradable starch [3,20].…”

Synchrony Degree of Dietary Energy and Nitrogen Release Influences Microbial Community, Fermentation, and Protein Synthesis in a Rumen Simulation System

“…Milk protein has different types of biological activities, e.g., essential amino acids, growth factors, hormones, enzymes, antibodies, and immune stimulants [1]. An increasing supply of metabolizable protein can increase milk protein yield, and microbial crude protein (MCP) contributes about 40%-60% of metabolizable protein [2,3]. In addition, compared with feed protein, MCP is an excellent source for milk protein production in terms of amino acid contents [4].…”

Effects of acetate and long-chain fatty acids infusion into external pudic artery on lactation performance and milk fatty acid composition in lactating dairy cows

“…The same concentrate was used in both diets (ingredients and chemical composition of the two diets are shown in Table 1) which were fed as a total mixed ration (TMR). Corn stover has a lower nutritional level (Zhu et al 2013), a lower effective degradability in the rumen (Zhou et al 2015), and a lower crude protein content (Saenger et al 1982) than does MFs. Corn stover in…”

“…Changes to the diets of cows can affect the nutrient supply and then affect lactation performance (Boerman et al 2015). The roughage quality in a diet is important to milk synthesis due to its effect on rumen metabolism, thereby influencing the secretion of milk components (Zhou et al 2015). In addition, milk fat, an important component in milk, is sensitive to dietary variations.…”