Changes in rumen fermentation and rumen wall absorption processes in the transition cow
by A.C Berge, Dairy Solutions Newsletter, 2010, no 6
The transition period for the dairy cow refers to the three weeks before calving to the three weeks after calving. During this time, the cow experiences many hormonal, metabolic, and dietary changes in preparation for calving and the upcoming lactation. This is the most critical period for dairy cow productivity and health (Grummer 1995, Goff and Horst 1997). In order that cows can achieve their genetic potential for milk production and remain healthy, a healthy rumen is essential. When the rumen becomes dysfunctional, feed digestion is impaired and cows become susceptible to a range of metabolic diseases and there is an immediate drop in milk production. The rumen adaption involves the rumen microbiota (microbial population) as well as rumen wall and supporting tissues and functions.
The dry cow rumen
Dry cows are usually fed a high forage diet. The rumen microbial population in high forage diets consists of a low number of lactate producers (starch digesters) and lactate users (convert lactate to acetate and propionate), and a large number of cellulolytic bacteria. The rumen papillae that are required for the absorption of volatile fatty acids (VFA) are reduced in length.
Preparing for the lactating period.
For a cow producing about 35 kg milk per day the energy demands can more than double (from 60 MJ NEL/day in late gestation to 150 MJ NEL/day in peak lactation). The cow’s restricted diet pre-partum is replaced with an energy dense diet ad libitum to meet the cow’s energy and nutrient requirements during lactation. This increased dry matter intake of an energy dense diet causes dramatic changes in rumen fermentation (Martens 2010). However, this transition period is commonly associated with a depression in feed intake, at the time when the energy and nutrient demands more than double. Gradual reductions in the cow’s voluntary dry matter intake (DMI) begin at 3 weeks pre-partum and accelerate during the final 7 days before calving. The resulting negative energy balance, lack of glucose and proteins need to be quickly overcome in order to optimize health and productivity.
A sub-optimal rumen function immediately affects the energy delivery and balance and is within a day reflected in the cow’s milk yield.
The transition cow rumen’s challenge
The rumen must efficiently adapt to meet the cow’s energy and nutrient requirements. If the fresh cow is abruptly switched from a high forage diet to a high concentrate diet, she may develop ruminal acidosis because the lactate producers multiply much more rapidly compared to the lactate users. As a result, lactate accumulates and the pH in the rumen drops dramatically. When the rumen papillae are not fully developed, the VFA are poorly absorbed and the rumen pH is further reduced, killing or inactivating many of the rumen protozoa and bacteria. Sub-acute ruminal acidosis (SARA) is the name referred to the metabolic disease condition associated with a drop in ruminal pH and decreased volatile fatty acid (VFA) absorption. SARA is also associated with endotoxin production that can lead to depressed feed intake and further enhancing the negative energy balance of the transition cow.
Components influencing rumen function
There are several components influencing rumen function; the intrinsic feed structure and components and the feed’s degradation characteristics, the microbial processes, the intraruminal conditions, the rumen wall and the host regulations such as saliva production, and absorption of volatile fatty acid (VFA) and nutrients. Furthermore the feeding times and frequency will strongly influence the microbiota.
The rumen microbial population
Most of the cow’s absorbed nutrients are the result of microbial fermentation or modification, and not what the cow actually eats. The rumen microbial population (microbiota) exists in a highly dynamic state and dramatic changes can occur with dietary changes. The major change in the rumen microbiota and fermentation processes in early lactation is caused by the quantity, the type and quality of carbohydrates fed. A more amylolytic microbial population emerges in the rumen and the fermentation becomes increasingly proprionate oriented. There is a furthermore a shorter ruminal retention time of feed and ruminal bacteria. More fermentation means more VFA production and a lower pH. While the rumen is very well buffered around pH 6.8, the buffering capacity below pH 6.0 is poor. A major consequence when ruminal pH falls below 6 is that fiber digestion declines dramatically. The ability and time needed for the rumen bacteria to adapt to these changes is therefore critical for the cow.
Rumen epithelium adaptive capacity
The epithelium is the major buffering mechanism of the rumen in early lactation. Rumen adaptation to the lactation diet involves changes in enzyme activities, an increase in the number and size of papillae and enhanced transportation rates of ions (Etschmann et al, 2009). The rumen papillae growth and development in the transition period is highly linked to a good VFA absorption. The rumen papillae shape will maximize the surface area to be able to absorb VFA. Studies indicate that the cow has a high capacity to adapt the rumen wall to the intra-ruminal fermentation conditions (Bannink, 2008). However, early functional adaptation without rumen epithelium growth appears to be the first step in coping with altered fermentation rates following diet change. Functional adaptation to a new diet occurred within a week to a new diet, whereas the structural adaptations (rumen papillae) took 6 weeks to reach peak level. The increased energy and protein intakes of the cow rapidly results in higher rates of transport of Na, Mg and Ca, increased VFA absorption and bicarbonate secretion (Etschmann et al, 2009). Studies further indicate that several factors such as VFA concentrations (particularly butyrate) and hormones (IGF-1 and insulin) are involved. A transition adaptation period of less than 10 days will create high VFA concentrations in the rumen due to that the epithelium has insufficient buffering capacity.
Recommended nutritional strategies in transition period
To allow the rumen function involving the microbiota and the rumen wall to adapt to the upcoming lactation period, at least two weeks prior to parturition the cow should be fed a diet that is easier and more rapidly fermented than diets in the early dry period. Furthermore, all efforts should be made to improve the voluntary feed intake to prevent SARA associated conditions that leads to milk production depression.
References
Bannink et al, 2008, Modelling the implications of feeding strategy on rumen fermentation and functioning of the rumen wall. Animal Feed Science & Technology143:3-26
Etschmann et al, 2009, Change of ruminal sodium transport in sheep during dietary adaptation. Archives of Animal Nutrition 63:26-38
Goff, J.P. and Horst, R.L. 1997, Physiological changes at parturition and their relationship to metabolic disorders. Journal of Dairy Science 80:1260-1268.
Grummer R.R. 1995, Impact of changes in organic nutrient metabolism on feeding the transition dairy cow. Journal of Animal Science 73:2820-2833
Martens H., et al, 2010, Changes in ruminal absorption processes during transition. Dairy Solutions Symposium, Rumen Health: A 360º Analysis , Utrecht, NL.
The dry cow rumen
Dry cows are usually fed a high forage diet. The rumen microbial population in high forage diets consists of a low number of lactate producers (starch digesters) and lactate users (convert lactate to acetate and propionate), and a large number of cellulolytic bacteria. The rumen papillae that are required for the absorption of volatile fatty acids (VFA) are reduced in length.
Preparing for the lactating period.
For a cow producing about 35 kg milk per day the energy demands can more than double (from 60 MJ NEL/day in late gestation to 150 MJ NEL/day in peak lactation). The cow’s restricted diet pre-partum is replaced with an energy dense diet ad libitum to meet the cow’s energy and nutrient requirements during lactation. This increased dry matter intake of an energy dense diet causes dramatic changes in rumen fermentation (Martens 2010). However, this transition period is commonly associated with a depression in feed intake, at the time when the energy and nutrient demands more than double. Gradual reductions in the cow’s voluntary dry matter intake (DMI) begin at 3 weeks pre-partum and accelerate during the final 7 days before calving. The resulting negative energy balance, lack of glucose and proteins need to be quickly overcome in order to optimize health and productivity.
A sub-optimal rumen function immediately affects the energy delivery and balance and is within a day reflected in the cow’s milk yield.
The transition cow rumen’s challenge
The rumen must efficiently adapt to meet the cow’s energy and nutrient requirements. If the fresh cow is abruptly switched from a high forage diet to a high concentrate diet, she may develop ruminal acidosis because the lactate producers multiply much more rapidly compared to the lactate users. As a result, lactate accumulates and the pH in the rumen drops dramatically. When the rumen papillae are not fully developed, the VFA are poorly absorbed and the rumen pH is further reduced, killing or inactivating many of the rumen protozoa and bacteria. Sub-acute ruminal acidosis (SARA) is the name referred to the metabolic disease condition associated with a drop in ruminal pH and decreased volatile fatty acid (VFA) absorption. SARA is also associated with endotoxin production that can lead to depressed feed intake and further enhancing the negative energy balance of the transition cow.
Components influencing rumen function
There are several components influencing rumen function; the intrinsic feed structure and components and the feed’s degradation characteristics, the microbial processes, the intraruminal conditions, the rumen wall and the host regulations such as saliva production, and absorption of volatile fatty acid (VFA) and nutrients. Furthermore the feeding times and frequency will strongly influence the microbiota.
The rumen microbial population
Most of the cow’s absorbed nutrients are the result of microbial fermentation or modification, and not what the cow actually eats. The rumen microbial population (microbiota) exists in a highly dynamic state and dramatic changes can occur with dietary changes. The major change in the rumen microbiota and fermentation processes in early lactation is caused by the quantity, the type and quality of carbohydrates fed. A more amylolytic microbial population emerges in the rumen and the fermentation becomes increasingly proprionate oriented. There is a furthermore a shorter ruminal retention time of feed and ruminal bacteria. More fermentation means more VFA production and a lower pH. While the rumen is very well buffered around pH 6.8, the buffering capacity below pH 6.0 is poor. A major consequence when ruminal pH falls below 6 is that fiber digestion declines dramatically. The ability and time needed for the rumen bacteria to adapt to these changes is therefore critical for the cow.
Rumen epithelium adaptive capacity
The epithelium is the major buffering mechanism of the rumen in early lactation. Rumen adaptation to the lactation diet involves changes in enzyme activities, an increase in the number and size of papillae and enhanced transportation rates of ions (Etschmann et al, 2009). The rumen papillae growth and development in the transition period is highly linked to a good VFA absorption. The rumen papillae shape will maximize the surface area to be able to absorb VFA. Studies indicate that the cow has a high capacity to adapt the rumen wall to the intra-ruminal fermentation conditions (Bannink, 2008). However, early functional adaptation without rumen epithelium growth appears to be the first step in coping with altered fermentation rates following diet change. Functional adaptation to a new diet occurred within a week to a new diet, whereas the structural adaptations (rumen papillae) took 6 weeks to reach peak level. The increased energy and protein intakes of the cow rapidly results in higher rates of transport of Na, Mg and Ca, increased VFA absorption and bicarbonate secretion (Etschmann et al, 2009). Studies further indicate that several factors such as VFA concentrations (particularly butyrate) and hormones (IGF-1 and insulin) are involved. A transition adaptation period of less than 10 days will create high VFA concentrations in the rumen due to that the epithelium has insufficient buffering capacity.
Recommended nutritional strategies in transition period
To allow the rumen function involving the microbiota and the rumen wall to adapt to the upcoming lactation period, at least two weeks prior to parturition the cow should be fed a diet that is easier and more rapidly fermented than diets in the early dry period. Furthermore, all efforts should be made to improve the voluntary feed intake to prevent SARA associated conditions that leads to milk production depression.
References
Bannink et al, 2008, Modelling the implications of feeding strategy on rumen fermentation and functioning of the rumen wall. Animal Feed Science & Technology143:3-26
Etschmann et al, 2009, Change of ruminal sodium transport in sheep during dietary adaptation. Archives of Animal Nutrition 63:26-38
Goff, J.P. and Horst, R.L. 1997, Physiological changes at parturition and their relationship to metabolic disorders. Journal of Dairy Science 80:1260-1268.
Grummer R.R. 1995, Impact of changes in organic nutrient metabolism on feeding the transition dairy cow. Journal of Animal Science 73:2820-2833
Martens H., et al, 2010, Changes in ruminal absorption processes during transition. Dairy Solutions Symposium, Rumen Health: A 360º Analysis , Utrecht, NL.