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Nutrient synchrony: is it a suitable strategy to improve nitrogen utilization and animal performance?


An excessive supply of feed nutrients results in an increase in waste excreted to the environment. The possible environmental pollutants produced by livestock are nitrogen, phosphorus and other organic compounds (e.g., methane and nitrous oxide). Excretion of these components to the environment may be increased by inefficient digestion and metabolism of the ruminant animal, and much of the inefficiency may occur in the rumen due to complicated and competitive metabolic pathways of rumen microbiota (Russell, 2002). In ruminants, actual digestion by the enzymes secreted by the host animal occurs after rumen microbes have modified feed nutrients into different forms (e.g. volatile fatty acids, ammonia and microbial protein). Digestion and metabolism of ruminants, thus, depend much on rumen microbial metabolism (Khezri et al., 2009). Therefore, better understanding and subsequent manipulation of rumen function is a prerequisite for efficient animal production (milk or meat) and for lower nutrient losses during digestion and metabolism.

An adequate but not excessive nitrogen (N) supply to support the animal's requirement has been one of the biggest concerns in our industry because protein sources are the most expensive ingredients in animal diets. Non-excessive N supply to the animal becomes more important since the amounts of N excreted in animal manure have increased markedly during recent decades, causing unacceptable air and water pollution (Hristov et al., 2005). In dairy cows, inefficient N utilization caused the loss of N in urine while the amount of N excretion in faeces was relatively constant (Castillo et al., 2001). Therefore, any measures to increase N utilization of ruminants would reduce urinary N excretion. Improved efficiency of microbial protein synthesis (MPS) is considered as the most important target to maximize MPS, while synchronization of carbohydrate and protein supply in the rumen has been suggested as one possible solution to achieve this (Kaswari et al., 2007).

The term "synchrony" derived from Greek roots for "together" and "time," means simultaneous occurrences in general (Hall et al., 2008). In ruminant nutrition, "synchrony" means providing both rumen degradable protein (RDP; non protein N and rumen degradable true protein) and energy (ruminally fermentable carbohydrates) to the rumen, so that ruminal microorganisms use both simultaneously. The synchronization of the ruminal degradation rate of carbohydrates and protein has been proposed as a method to increase ruminal MPS, improve efficiency of N usage and animal performance, and decrease urinary N excretion (Cole et al., 2008). Synchronous supply of energy and N to the rumen enhanced the efficiency of microbes in capturing N and use of ATP for microbial growth (Johnson, 1976; Herrera-Saldana et al., 1990; Sinclair et al., 1991; 1993; Richardson et al., 2003), which implied synchronized feeds increased microbial protein production in the rumen and enhanced rumen fermentation efficiency, and thereby improved feed utilization and animal performance (Chumpawadee et al., 2006).

A number of studies have been conducted to evaluate the effects of synchronization of energy and N supplied in the rumen using various systems. There is supportive evidence indicating that the synchronous supply of energy and nitrogen in the rumen is beneficial in terms of efficient utilization of nutrients by ruminants; however, conflicting results have also been reported. In this paper, we reviewed the possible ways of achieving synchronization of energy and N supply in the rumen and the effects of synchrony on rumen function, MPS and performance of ruminant animals.


Several ways to supply energy and N to the rumen synchronously have been reported in the literature. Some examples are: i) Exchange of feed ingredients; ii) Supplementation of energy or protein sources; iii) Using index values and iv) Change in feeding frequency or pattern. Changing feed ingredients or composition could achieve synchronization of energy and N supply to the rumen. For example, changing the concentrate:forage ratio is a traditional way of manipulating synchronicity of a feed. However, some other factors (i.e. level of forage intake and its fermentation rate, and composition of concentrate and its associative effect on forage digestibility) make it difficult to distinguish a synchrony effect from effects caused by other factors (Cabrita et al., 2006). A change in feed ingredients alters the amount of organic matter and nitrogen and their fermentation rate in the rumen, which may influence extent of synchronicity in the rumen. Rotger et al. (2006) synchronized energy and N supply to the rumen by changing feed composition and formulated the diets with three different synchronicity combinations (fast fermentable synchronicity, slow fermentable synchronicity and asynchronicity).

Synchrony achieved by energy or N supplementation also resulted in a positive effect on MPS (Lardy et al., 2004; Elseed, 2005). Particularly in forage-fed ruminants, supplementation of energy or N sources can improve rumen fermentation since carbohydrate and N degradation rates in forages are normally unbalanced (Van Soest, 1994). Nutrient supplementation may enhance rumen microbial population and VFA production (Mould et al., 1983). Hersom (2008) suggested several strategies to elicit optimal synchrony. The most frequently applied supplementation strategies are controlling the timing of feed offering, the form of nutrients supplied and supplement types and the balance of energy to protein ratio (Hersom, 2008). In a number of experiments using mature cows, forage quality was an important factor for successful nutrient synchrony effects. Low quality forage with frequent supplementation tended to increase the positive effect of nutrient synchrony (Hersom, 2008) more than with high quality forages.

Another possible way is to develop a synchrony index (SI). A number of experiments have used SI to scale synchronization of energy and N release in the rumen. Sinclair et al. (1993) used CP and OM degradabilities of dietary ingredients and determined SI by using in situ data and 25 g of N/kg truly rumen digested OM was assumed to be the optimum synchrony between N and OM (Czerwaski, 1986). When carbohydrate rather than OM was used, 32 g N/kg carbohydrate degraded in the rumen was used instead (Sinclair et al., 1991). The value of 1.0 SI represents perfect synchrony between energy and N supply throughout the day, while values <1.0 indicate the degree of asynchrony (Sinclair et al., 1993). The SI proposed by Sinclair et al. (1993) may be useful to estimate nutrient synchrony of feeds (Cole et al., 2008). However, since the in situ method used to calculate SI is influenced by many factors, such as animal, nylon bags and feedstuff characteristics (Madsen and Hvelplund, 1994; Huhtanen, 2005), the SI of a feed may not well represent the effect of the feed on animal production or MPS. A new diet evaluation system using protein balance in the rumen has been developed in the Netherlands (Ichinohe et al., 2008). The OEB (degradable protein balance in the Dutch system) value shows the balance between microbial protein synthesis potentially possible from ruminal degradable crude protein and from the energy extracted during anaerobic fermentation in the rumen (Tamminga et al., 1994). When the OEB value is >0, potential loss of N from the rumen occurs, whilst a value lower than 0 means more ruminal degradable CP is required for microbial activity (Valkeners et al., 2004).

Although changing feed ingredients or nutrient supplementation could regulate the synchronicity between energy and N release, these methods have some intrinsic problems. Most experiments which have been conducted using them cannot distinguish the effect of synchronization from that caused by different characteristics of individual feedstuffs. Changing feeding frequency or pattern was thus employed in some synchronization experiments to minimize effects of feedstuffs. Because these methods use the same ingredients and alter feeding pattern only, any change in metabolite patterns in the rumen will be mainly due to nutrient synchronization. Richardson et al. (2003) reported that the use of different ingredients may alter microbial or tissue metabolism due to some aspects other than a pattern of dietary nutrient supply. The effects of dietary synchrony were assessed by altering the sequence of feeding individual ingredients by Kaswari et al. (2007), who studied synchrony effects by using different feeding frequency and pattern. For instance, the diets offered had three different sequences to modulate SI (FS-A: energy and protein source together, FS-B: energy source first followed by protein source, FS-C: protein source first followed by energy source).


Microbial protein synthesis and N retention

Ruminal microorganisms ferment dietary carbohydrates and protein to obtain energy and N for maintenance and growth. Through this process, the two major nutrients (i.e. VFA and microbial protein) for the host animal are produced. MPS is important in ruminants because microbial protein synthesized in the rumen provides from 50% to nearly all amino acids required by ruminants, depending on the rumen undegraded protein (RUP) concentration of the diet (NRC, 2000). MPS is influenced by many dietary and animal factors, which include nitrogen concentrations, nitrogen sources, rates of nitrogen and carbohydrate degradation, carbohydrate in the diets, dry matter intake, and synchronization of nitrogen and energy (Karsli and Russell, 2002). Satter et al. (1977) and Hume et al. (1970) suggested 11-13% CP in diets was adequate to obtain optimal microbial protein synthesis, and Ludden et al. (1995) reported that the amount and degradation rate of RDP were critical for microbial growth in the rumen because this fraction provides the N necessary for microbial growth, even though a low level of CP is provided in the diet.

Dietary protein is composed of RDP and RUP (NRC, 2001). RDP is degraded to peptides and amino acids and further deaminated into ammonia. When dietary RDP is in excess of the amount required by ruminal microorganisms, the excessive RDP is degraded to ammonia N, absorbed, metabolized to urea in the liver, and lost in the urine (Leng and Nolan, 1984). Leng and Nolan (1984) suggested that N metabolism in the rumen can be divided into two distinct events: protein degradation, which provides N sources for rumen microbes, and MPS.

Rumen microorganisms use carbohydrates as the main energy sources although protein also can be used. When adequate energy sources are supplied in the rumen, ammonia N can be converted to microbial protein. If the rate of protein degradation exceeds that of carbohydrate fermentation, large quantities of N are converted into ammonia, and likewise, when the rate of carbohydrate fermentation exceeds that of protein degradation, inefficient microbial protein synthesis may occur (Bach et al., 2005). Therefore, nutrient synchrony between the supply of energy and N to the rumen microorganisms should improve the efficiency of rumen microbes in capturing N and use of energy for microbial growth.

Although it is theoretically plausible that the synchrony of N and energy supply to the rumen microbes increases MPS, experimental evidence is somewhat controversial (Table 1). Some experiments showed positive effects of synchronization. Rotger et al. (2006) used combinations of two nonstructural carbohydrate sources (barley and corn) and two protein sources (soy bean meal and sunflower meal) in their experiment. The fast synchronous diet (barley and sunflower meal) and slow synchronous diet (corn and soybean meal) tended to result in greater microbial N production in vitro. Witt et al. (1999b) reported that synchronous treatments having rapidly degradable OM sources produced higher purine derivatives and thus efficiencies of MPS were higher. However, another study conducted by the same group (Witt et al., 1999a) did not show MPS improvement. Using the changing feed ingredient strategy, Herrera-Saldana et al. (1990) reported that a rapid synchronization (both high degradable energy and protein sources) diet showed higher microbial N flow and efficiency of microbial protein synthesis than an asynchronous diet. Rotger et al. (2006) also conducted a similar experiment and indicated that synchronization tended to result in greater microbial N production in vitro. Kim et al. (1999a) infused maltodextrin directly to the rumen through a ruminal cannula and showed that synchronous treatments had a positive effect on MPS.

In our previous study, synchrony of energy and nitrogen supply using SI increased MPS in steers (unpublished data). Although there was no difference in DM digestibility, steers on the diet having the highest SI (0.83) excreted more purine derivatives in urine than those on the lowest SI (0.77), which implied that a synchronized diet improved MPS in the rumen. Steers receiving the lowest SI diet had significantly (p<0.05) lower total VFA concentration in the rumen, which also indicated a decrease in efficiency of rumen fermentation with diets having lower SI.

There are also some studies that indicated no effect of nutrient synchrony on efficiency of microbial growth. Ichinohe and Fujihara (2008) reported that microbial N supply was greater for an asynchronous diet than a synchronous diet. Kaswari et al. (2007) and Richardson et al. (2003) also showed that there were no differences in efficiencies of MPS and N deposition among treatments in which diets were formulated to have different SI. In Kaswari's experiment, feeding energy sources first improved microbial activity although the synchrony index was low. When the OEB system was used to regulate synchronicity in feeds, duration of imbalance between energy and N supplies for the ruminal microbes had no significant effect on microbial N flows at the duodenum (Valkeners et al., 2004).

Animal performance and rumen fermentation

Since nutrient synchrony may improve rumen fermentation, increase VFA production and provide more amino acids to the host animal, its effect on animal performance and rumen fermentation were also investigated in many studies (Table 2). Richardson et al. (2003) shifted specific ingredients between morning and evening feeding to provide either a synchronous, intermediate, or asynchronous supply of OM and N to the rumen. The daily live weight gain was not influenced by treatments, but lambs fed an asynchronous diet tended to have a lower fat content in the carcass, which suggested that dietary synchrony improved energy utilization. Witt et al. (1999b) reported that animals given synchronous diets had a significantly higher live weight gain. In the following study using lactating ewes, synchronous treatment tended to increase milk protein yield (g/d), but milk or milk fat yield (g/d) was not improved by the same treatment (Witt et al., 2000). Nutrient supplementation to promote synchronization also showed a positive effect. Elseed (2005) showed that digestibility and VFA production of ammoniated straw were improved by supplying protein, which was explained by the fact that carbohydrate degradation rate of straw could be better matched by supplementation of proteins.

On the contrary, there were some studies which showed no effect of synchronization of energy and N supply in the rumen on animal performance. Rotger et al. (2006) showed that a synchronous feed which had increased OM digestibility and VFA production in vitro had no effect on dry matter intake, apparent total digestibility and total VFA production in vivo. Shabi et al. (1998) also suggested that synchronization had no effects on ruminal ammonia N and VFA concentration. Cole et al. (2008) conducted metaanalysis of the synchronization effects on DMI, ADG and MPS, calculating synchrony index of the diets used in many studies based on NRC (2000) tabular values for ingredient composition, degradabilities of carbohydrate and CP fraction. They concluded that synchronization of the fermentation of dietary carbohydrates and CP was not as effective as had been expected and other physiological mechanisms worked in concert to compensate for nutrient asynchrony in a diet (Cole et al., 2008).

Theoretically, synchronization of energy and N supply in the rumen should allow more efficient use of nutrients by rumen microbes, increase microbial protein and fermentation end products, increase available nutrients in the small intestine, and thus potentially improve animal performance and reduce N excretion to the environment. However, due to additional challenges to nutrient synchrony that should be considered, a number of studies showed contradictory results in MPS, N retention and animal production performance.

Feed characteristics are important factors for determining the effect of synchronization. In forage- fed cows, chemical composition of forage could be a challenge to nutrient synchrony. High quality forages may not successfully support nutrient synchrony as indicated by Hersom (2008) since they contain an excessive amount of N compared to energy. Kaswari et al. (2007) reported that accurate evaluation of nutrient synchrony in feedstuffs may be influenced by variation in the in situ technique. This includes preparation of samples, characteristics of bags, procedure and locality of incubation, washing, drying, animals, feeding of animals, and degree of correction for small particles lost through the bag pores without being degraded (Madsen and Hvelplund, 1994).

N recycling in the rumen can reduce N deficiency in the rumen. Holder et al. (1995) reported that N recycling was greater with asynchronous diets. N recycling in the rumen plays a major role in regulating the amount of ruminally available N and allows for continuous synchronization of N and energy yielding substrates for the microorganisms in the rumen (Valkeners et al., 2004).

Finally, most rumen bacteria can use ammonia N as a source for microbial growth; however, other nutrients (i.e., preformed amino acids, sulfur, phosphorus, and other minerals and vitamins) are also required for MPS (Sniffen et al., 1987). Therefore, to maximize microbial growth, synchronous supply of not only N and energy but also other nutrients should be considered.


Nutrient synchrony may have positive roles in maximizing MPS, improving animal performance and reducing N excretion. However, a number of studies showed inconsistent results. It suggests that the nutrient synchrony concept needs further investigation before applying to the field situation. Furthermore, better understanding of the complex ruminal ecosystem of mixed microorganisms and physiological effects such as N recycling is also required.


This study was carried out with the support of Cooperative Research Program for Agricultural Science & Technology Development (Project No. 20090101-030-166-001-03-00), RDA, Republic of Korea.


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* This paper was presented at 2009 Beijing International Symposium on Improvement of Feed Efficiency through Biotechnology during November 15-17, 2009.

Ji Young Yanga, J. Seo (a), H. J. Kim, S. Seo (1) and Jong K. Ha **

Department of Agricultural Biotechnology, Research Institute for Agriculture and Life Sciences, College of Agriculture and Life Science, Seoul National University, Seoul 151-742, Korea

** Corresponding Author: Jong K. Ha. Tel: +82-2-880-4809, Fax: +82-2-875-8710 , E-mail:

(1) Divison of Animal Science and Resource, Chungnam National University, Dajeon 305-764, Korea.

(2) Both authors equally contributed to this work as the first author.
Table 1. Effects of synchronization on MPS and N retention in the
rumen using different methods of nutrient synchrony

                         Methods for
Author                   synchronization         Findings

Positive response

  Herra-saldana et al.   Changing feed           Rapid synchronization
    (1990)               ingredients             (high degradable
                                                 energy and protein
                                                 sources in the rumen)
                                                 showed highest
                                                 microbial nitrogen
                                                 (MN) flows and
                                                 efficiency of
                                                 microbial protein
                                                 synthesis (EMPS) than
                                                 asynchronous or slow
                                                 synchronous diets.

  Henning et al.         Changing feeding        Synchronization
    (1991)               pattern and infusion    treatment lowered
                         of glucose              rumen ammonia
                                                 concentrations and
                                                 fluctuation, but no
                                                 improvement in EMPS
                                                 or microbial DM
                                                 production. Glucose
                                                 pulse dosing improved
                                                 both microbial DM
                                                 production and EMPS.

  Aldrich et al.         Changing feed           Synchronization of
    (1993)               ingredients             rumen available
                                                 carbohydrate and
                                                 protein for rapid
                                                 degradation gave the
                                                 highest microbial
                                                 protein flows.

  Henning et al.         Infusion or pulse       Synchronous treatment
    (1993)               dosing of sugar and     had lower N
                         urea/casein             concentrations but
                                                 did not show
                                                 improvement in MN
                                                 flow or EMPS.
                                                 Continuous sugar
                                                 infusion resulted in
                                                 an improvement of MN

  Sinclair et al.        Using synchrony index   Synchronous diet
   (1993)                                        increased microbial N
                                                 contents and EMPS.

  Lee et al. (1997)      Changing feed           Synchronization of
                         ingredients             energy and nitrogen
                                                 release in the rumen
                                                 increased MPS.

  Kolver et al.          Changing feeding        Synchronization
    (1998)               frequency ([+ or -]     between energy and N
                         timed concentrate       release decreased
                         feeding)                ammonia concentration
                                                 in the rumen.

  Witt et al.            Using synchrony index   Fast degradation rate
    (1999b)              and adjusting           of OM and synchronous
                         synchronicity   rate    treatment had the
                         with  feed intake       highest production of
                         restriction             microbial N, but
                                                 there was no effect
                                                 on N retention.

  Elseed (2005)          Supplementation of      Supplementation of
                         protein source and      protein sources
                         adjusting feeding       improved microbial N
                         frequency               yield of ammoniated
                                                 straw and N

  Rotger et al.          Changing feed           Synchronization
    (2006)               ingredients             tended to result in
                                                 greater microbial N
                                                 flow in vitro.

  No difference or negative response

  Newbold and Rust       Changing feeding        Asynchronous
    (1992)               pattern                 treatment of energy
                                                 and N release had
                                                 little effect on
                                                 microbial growth.

  Henderson et al.       Changing feed           Asynchronous diets
    (1998)               ingredients             had more microbial
                                                 protein flow and EMPS
                                                 than synchronous

  Kim et al. (1999a)     Infusion or pulse       Continuous
                         dosing of               maltodextrin infusion
                         maltodextrin at         showed MPS
                         different times         improvement.

  Kim et al. (1999b)     Infusion or pulse       Both synchronization
                         dosing of sucrose at    and asynchronization
                         different times         condition showed no
                                                 effect on MPS.

  Richardson et al.      Using synchrony index   There was no
    (2003)               and changing feeding    significant effect of
                         pattern                 synchrony treatment
                                                 on N deposition.

  Valkeners et al.       Using OEB (Dutch        Microbial N flow at
    (2004)               protein evaluation      the duodenum and N
                         system) index           retention were not
                                                 affected by
                                                 imbalanced supply of
                                                 energy and N.

  Kaswari et al.         Changing feeding        EMPS and non ammonia
    (2007)               frequency and feeding   N flow at the
                         pattern                 duodenum was the
                                                 highest in FS-B where
                                                 energy sources were
                                                 fed at the first
                                                 feeding time.

  Ichinohe and           Changing feed           Microbial N supply
    Fujihara (2008)      ingredients and         was greater for
                         varied to experiment    asynchronous diet
                         period                  than for synchronous
                                                 diet. N retention was
                                                 not influenced.

Table 2. Effects of synchronization on animal performance and rumen

                      Methods of
Author                synchronization          Findings

Positive response

  Sinclair et al.     Using synchrony index    Rumen VFA proportions
    (1993)                                     were more stable for
                                               synchronous diet than
                                               the asynchronous diet,
                                               and it was suggested
                                               that the synchronized
                                               diet caused a more
                                               stable microbial
                                               population in the
                                               rumen, because
                                               variation in VFA
                                               resulted from change
                                               in rumen microbial

  Witt et al.         Using synchrony index    Fast degradation rate
    (1999a)           and adjusting            of OM and synchronous
                      synchronicity rate.      treatment improved
                      Feeds were given ad      growth efficiency.
                      libitum.                 Total VFA
                                               concentrations were
                                               not influenced by

  Witt et al.         Using synchrony index    Synchronous treatments
    (1999b)           and adjusting            with fast or slow
                      synchronicity rate.      degradation rate of OM
                      Feed intake was          produced higher live
                      restricted.              weight gain and feed
                                               conversion efficiency
                                               than asynchronous

  Elseed (2005)       Supplementation of       Supplementation of
                      protein source and       protein sources
                      adjusting feeding        improved ruminal
                      frequency                digestibility of low
                                               quality rice straw and
                                               rumen fermentation end
                                               products in sheep.

  Rotger et al.       Changing feed            Synchronization tended
    (2006)            ingredients              to result in greater
                                               true OM digestibility
                                               and VFA concentration
                                               in vitro.

  No difference or negative response

  Shabi et al.        Changing   feed          Synchronization had no
    (1998)            ingredients and          effects on ruminal
                      adjusting feeding        ammonia N and VFA
                      frequency                concentration.

  Witt et al.         Using synchrony index    Synchronous diet did
    (2000)                                     not significantly
                                               alter milk or milk fat
                                               yield while protein
                                               yield tended to be
                                               increased. There was
                                               no significant
                                               difference in average
                                               rumen VFA
                                               concentration and

  Richardson et al.   Using synchrony index    Live weight gain or
  (2003)              and changing feeding     feed conversion
                      pattern                  efficiency were not
                                               different, but
                                               asynchronous diet
                                               resulted in a lower
                                               efficiency of dietary
                                               energy use.

  Kaswari et al.      Changing   feeding       Ruminal pH, ammonia N
    (2007)            frequency and feeding    and total VFA were not
                      pattern                  influenced by SI.

  Ichinohe et al.     Changing feed            There were no
    (2008)            ingredients and varied   differences among
                      to experiment period     treatments in DMI and
                                               BW change
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Author:Yang, Ji Young; Seo, J.; Kim, H.J.; Seo, S.; Ha, Jong K.
Publication:Asian - Australasian Journal of Animal Sciences
Article Type:Report
Geographic Code:9SOUT
Date:Jul 1, 2010
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