The Effects of Synchronization of Carbohydrate and Protein Degradation Rate in the Rumen on Rumen Fermentation and Physiology of Holstein Steers

Abstract

Three experiments were conducted to study (1) the effects of enzyme and formaldehyde treatment on synchronicity of carbohydrate and protein degradation and rumen fermentation characteristics, (2) the effect of synchronized supplements on milk production in dairy cows, and (3) the effects of synchronization of carbohydrate and protein supply on ruminal fermentation, nitrogen metabolism and microbial protein synthesis in Holstein steers. Detailed results from each experiment are described below.

1. Experiment 1: The effects of enzyme and formaldehyde treatment on synchronicity of carbohydrate and protein degradation and rumen fermentation characteristics in in vitro study

The objective of this study was to examine, 1) the effects of enzyme and formaldehyde treatment on degradation characteristics of carbohydrate and protein source and synchronicity, and 2) the effects of synchronizing carbohydrate and protein supply on rumen fermentation and MPS excluding feeds characteristics effects in in vitro experiment. Corn (C) and soy bean meal (S) were treated with enzyme (EC, ES) and formaldehyde (FS) to manipulate degradation rate in the rumen. Totally, 6 kinds of experimental feeds (CS, CES, CFS, ECS, ECES and ECFS) which had different synchrony index were prepared. Highly synchronous diet had greatest DM digestibility within corn based groups. However the degree of synchronicity did not influence on digestibility within enzyme treated corn groups. At 12hr and 24hr incubation, EC containing diets showed lower ammonia-N concentration than those of C containing diets group regardless the degree of synchronicity. However, similar effect was not observed when EC was offered. There were significant C and S treatments and their interaction effects on VFA concentrations. Similar to purine concentrations, total VFA production and all kinds of VFA concentrations of the groups used EC as an energy source were higher than those of other groups (CS, CES and CFS). Present results suggest that the availability of energy rather than the degree of synchronicity is most limiting factor on rumen fermentation and MPS.

2. Experiment 2: The effects of synchronization of carbohydrate and protein supply on ruminal fermentation, nitrogen metabolism and microbial protein synthesis in Holstein steers

Three rumen-cannulated Holstein steers were fed three different diets, each with a different synchrony index (SI) (LS: 0.77, MS: 0.81, and HS: 0.83) in order to examine the effect of diet on rumen fermentation, nitrogen balance, and microbial protein synthesis. Synchrony index was calculated based on the carbohydrate and crude protein fractions of each ingredient and their degradation rates. Feeding the steers diets with different SIs did not influence dry matter, crude protein, NDF, or ADF digestibility. The concentrations of total and individual VFA in the rumens of steers that were fed the two higher-SI diets were higher than in those fed the lower-SI diet (p<0.05), but there was no significant difference between the two higher-SI diets. One hour after feeding, steers on the LS diet had lower ruminal pHs than did those fed the MS or HS diets (p<0.05), and animals on the LS diet generally showed higher ruminal NH3-N levels than did animals on another diet, with the 4-h post-feeding difference being significant (p<0.05). Steers receiving the LS diet excreted more nitrogen (N) into their urine than did those on the two higher-SI diets (p<0.05), and the total N excretion of those on LS diet was also higher (p<0.05). Microbial N levels calculated from the concentrations of urinary purine derivatives were generally higher when the SI was higher, with the highest microbial protein synthesis being produced by steers on the HS diet (p<0.05). In conclusion, in the current study, ingestion of a synchronous diet by Holstein steers improved microbial protein synthesis and VFA production and decreased total N output.

3. Experiment 3: The effects of synchronized supplements on milk production in dairy cows

The objective of this experiment was to investigate the effects of supplementation of concentrate feeds having different synchronicity on milk production and components in forage fed dairy cows. 21 Korean Holstein cows milked by Automatic Milking System (AMS) were individually paired, matched in lactation number (1.71±1.06), days in milking (DIM) (150±54 days), milk yield (33.96±5.28kg/d), body weight (BW) (542.29±53.23kg) then, allocated to 3 groups of 7. Treatments were low synchronous group (LS), middle synchronous (MS) and high synchronous group (HS). The experimental feed DMI, CPI, NDFI and ADFI were higher significantly (p<0.05) as SI values increased throughout the test period. Treatments had significant effect on yield of milk, 3.5% FCM and ECM. The milk yield on LS supplementation group was lower than those of other treatments and 3.5% FCM or ECM increased as the experimental diets were more balanced at the ratio of CHO and N release in the rumen. However, all efficiencies of milk yield were significantly higher at the LS groups than those of MS although, there was no different on milk yield efficiency between LS and HS treatments. Treatments had no effect on fat, protein, lactose and SNF percentage but, the animals fed highly synchronous diets showed higher protein, lactose and SNF production than those fed LS diets. The number of rumination of animals fed LS diets was lowest and MS groups showed highest rumination counts but the ratio of rumination : DMI was higher at the LS treatments suggesting that DMI was crucial factor on the number of rumination. In a summary, synchronized feed can provide energy and protein simultaneously to improve microbial growth, efficiency of microbial protein synthesis so that rumen fermentation and digestion can be improved. These positive effects might stimulate the increment of animal production such as milk yield, thus the animals fed high synchronous diets might show higher DM intake than those fed asynchronous diets.