Abomasal PH And Milk Feeding
Abomasal PH And Milk Feeding
Summary
Cows milk/colostrum has a pH of 6.5 -5.7
CMR pH 6
Two-week-old Calf’s base abomasal pH 1 -2
An abomasal pH below 4 acts as an acid barrier that decreases the risk of Salmonella, E.coli and M. bovis establishing. Conversely these pathogens begin to multiply at a pH above 5.5 and can pass through the abomasum intact.
Abomasal pH rises to 6 within 15 minutes of drinking milk/CMR taking 6-7 hours to return to pre-feeding levels greatly increasing the risk of disease.
Acidified milk/CMR at a pH of 4.2 will kill E. coli, Salmonella and M. bovis pathogens.
Milk can be acidified down to 4.2 by adding citric acid.
Ask for a CMR that has an acidifier added.
Introduction:
Digestion of liquid feeds is a critical component of nutrition and health of young calves. “Mother Nature” designed calves to digest cow’s milk. The calf has the requisite digestive apparatus and enzyme systems to digest and absorb cow’s milk efficiently and utilize nutrients for growth.
When the calf drinks milk or milk replacer, it flows directly into its abomasum. The oesophageal groove closes off the opening from the oesophagus to the rumen. With the groove closed, milk bypasses the rumen. This prevents it from being fermented and potentially causing digestive problems for the calf.
Fresh cow’s milk/colostrum has a pH of between 6.5 – 6.7 which changes over time as it goes sour becoming more acidic as the pH gets lower. This occurs as lactic acid bacteria in milk convert lactose sugar into lactic acid. It also commonly contains E. coli and salmonella and more recently M. bovis pathogens.
But what about milk replacers? Calf milk replacers produced in NZ are generally based on milk ingredients which replicate whole milk and is almost identical to raw milk. Alternative overseas produced CMR’s use whey, whey protein concentrates and skim milk. The pH of most CMR on the NZ market once made up is around 6.
The calf digestive tract and pH.
The calf’s abomasum, the only functional stomach at birth, is not acidic until the calf is 1–2 days old and this has advantages and disadvantages. The major advantage is that the immune proteins in colostrum cannot be digested in the abomasum, so are absorbed into the bloodstream in the same form as when produced by the cow. This ensures their role as antibodies to protect against infection.
An acidic environment would kill off the immune proteins before they can be absorbed.
The low acidity of the abomasal contents from ingestion of colostrum in the newborn calf constitutes a potential risk from the bacteria (and probably viruses) taken through the mouth. These will not be killed as the acidity of the abomasum is insufficient and they can pass into the intestines where they can do the most harm.
All calves pick up bacteria in the first few days of life and this is essential for normal rumen development. However, some of the first bacteria to colonise the gut can also cause diarrhoea. Provided the calf has drunk colostrum, the maternal antibodies can control the spread of these more harmful bacteria.
The milk-fed calf must then produce an acid digestion in the abomasum and an alkaline digestion in the duodenum. This is achieved by the production of electrolytes in the gut wall.
For the enzymes, rennin and pepsin, produced by the calf to coagulate the milk proteins, there must be an acidic environment and this is provided by hydrochloric acid secretion into the abomasum. However, until the acid digestion is operating efficiently, which can take up to 7 days from birth, the only form of protein that can be digested is casein.
There is no substitute for casein in the very young calf. Milk replacers containing other forms of protein cannot be digested until the calves are older.
A two-week-old calf usually has a base pH in the abomasum between 1 and 2. It is eating little or no starter feed so the rumen will have little effect on abomasal pH. When the calf drinks milk/milk replacer, abomasal pH rises to the pH of the milk/milk replacer within 15 minutes of feeding. This naturally occurs when calves are fed once or twice daily, since they tend to consume all of their feed in large meals. Abomasal pH remains at this level for a couple of hours then decreases to the pre-feeding level over the next 6 to7 hours (figure 2A).
The pH of calves fed cow’s milk tends to decline faster than that of calves fed milk replacer based on whey products.
During this time, milk/milk replacer leaves the abomasum and enters the small intestine and while the abomasal pH is high, pathogens such as Salmonella, M. boivs or E. coli can pass through the abomasum intact. Importantly, normally low stomach (abomasal) pH is a key defensive mechanism against these pathogens for the calf.
The rate of abomasal emptying is controlled mainly by the volume ingested, its energy content, and to a lesser degree by the types of protein & fat, osmolarity and duodenal pH. After a meal, the pH in the duodenum reflects that of the abomasal contents, and ranges from 6.0 down to 1 or 2.
Compare this to a weaned calf at 8 weeks of age (Figure 2B). Abomasal pH is similar to adult levels and remains fairly constant, averaging about 2.1 to 2.2. This consistent pH is due to the more stable pH of the rumen and a consistent flow of nutrients from the rumen to the abomasum.
Why is this important?
A low abomasal pH is referred to as an acid barrier that decreases the risk of colonization of organisms such as Salmonella, E.coli and M. bovis. Conversely these pathogens begin to multiply at a pH above 5.5 allowing pathogens to pass through the abomasum intact.
Effect of Acidified Milk/Milk Replacer:
Now consider what happens when you feed milk/milk replacer that's been acidified to a pH of 4.2. Maximum pH in the calf's abomasum is now 4.2 instead of 6.0 (indicated by the red line in the adjacent graph).
Assuming maximum abomasal pH is maintained for a couple of hours and then starts to decrease as in Figure 2A, the calf should reach pre-feeding pH sooner and spend a longer time there between meals. As a result, average abomasal pH would be lower than with a non-acidified milk/milk replacer.
The maximum and average pH in the small intestine (duodenum) should also be lower. Feeding an acidified milk/milk replacer would reduce pH variability and move the average pH closer to the acid barrier. This could theoretically result in an environment that is less favourable to certain pathogens.
Confirming this a recent Canadian study found that standardized plate-loop-count bacterial cultures for acidified milk at a pH of 4.2 had no bacterial growth after several hours. Meanwhile, control samples (untreated) had bacterial colonies too numerous to count over the same timeframe.
Since the advent of M. bovis in NZ, feeding milk that is potentially infected with M. bovis is a classed as a high-risk activity in the spread of M. bovis. To limit the risk MPI recommend that fresh milk or colostrum transferred from farm to farm should be acidified to pH 4.5 or pasteurised. Pasteurization is common practice in calf rearing operations in USA and Europe to eliminate harmful pathogens.
Lowering milk pH:
Lowering the pH of fresh milk to 4.5 – 4.2 can be achieved by adding citric acid or commercially available products such as PKA from BEC Feed solutions. Lowering the pH below 4.2 results in calves less inclined to drink. (See https://www.dairynz.co.nz/publications/animal/acidifying-milk-with-citric-acid)
Acidified milk powder has been around a long time overseas and is specifically formulated to avoid problems with feeding acidified milk powder. Ask your supplier for an acidified CMR.
The level of acidification determines how effective a milk replacer is in reducing bacterial growth. The normal pH of milk replacer is about 6.0. The pH of acidified products ranges from about 5.8 all the way down to 4.2. Between 4.2 to 4.5 is the most effective pH range for reducing bacteria.
Abomasal ulcers:
Nature's way of feeding calves means that the calf typically consumes six to 10 meals per day and may consume 16 to 24 percent of their body weight as milk by the second week of life. In contrast conventional rearing systems often result in abomasal pH remaining at low levels for long periods which can lead to abomasal ulcers
Factors that increase the risk of abomasal ulcers,
once a day feeding,
rapid feeding or gorging,
limited access to milk,
restricted milk intake per meal,
inconsistencies in feeding times,
volumes of milk per feeding,
variation in milk temperature and percent solids,
high osmolality of the milk replacer,
feeding extremely high volumes of milk,
poor quality milk replacer that does not stay in solution or has poor digestibility,
feeding unpasteurized hospital milk that is high in bacterial numbers,
poor hygiene of feeding equipment used to feed calves or tanks and hoses used to distribute milk.
Symptoms range from mild abdominal pain and irregular appetite to septic shock, rapid heart rate, weak pulse, groaning, severe abdominal pain, dehydration and cool extremities with low chances of survival for severely affected animals and is commonly found in calves aged between four to twelve weeks old.
Free access feeding
of acidified milk:
Calf rearers in Finland Canada and USA have been feeding free access acidified milk successfully for years.
What is free access feeding
of acidified milk?
Free-access feeding mimics nature's way of feeding calves, allowing them to eat several small meals per day and exhibit suckling behaviour.
Acidification preserves the milk so it can be available at ambient temperatures for the calves throughout the day. Desired milk pH is 4.0 to 4.5 in this system, which inhibits bacterial growth.
If using CMR chose a product that has an acid already added.
The free-access feeding system consists of a reservoir to hold the acidified milk, plastic tubing (along with a one-way valve) and nipples to deliver the milk to the calves whenever they want it.
The system operates on the same principle of keeping feed available to lactating cows at all times. "Free-access feeding provides freedom from hunger — the best medicine for milk-fed calves”.
Advantages:
A lower incidence of scours and reduced scours treatment.
Calves are well-supported nutritionally with less disease incidence. "You still need to check calves daily, but you have to re-set your eyes to detect sick calves”.
Significantly better gains and improved body condition, as compared to conventional, non-accelerated feeding programs.
Less cross-suckling of group-housed calves.
Challenges:
Diarrhea can be a problem for some farms when the acidified milk is fed significantly warmer than 200C.
There is a need to ensure proper mixing and a way to mix the milk during the day to keep it from separating.
This system is not for everyone. These systems cannot overcome poor management or bad facility design.
In general, these calves drink much more milk than those conventionally fed — often nearly twice as much. Calf starter and water intake is less but resumes quickly to desired levels after weaning.
Increased milk consumption quickly adds up to additional calf-raising cost. Put pencil to paper before switching your feeding system. You will need to change your weaning schedule a few weeks earlier to get the most financial benefit from increased gains.
References:
Calf Sessions / October 3, 2017 / Effect of Acidified Milk Replacer on the Calf’s Digestive Tract / Rob Costello. https://www.biosecurity.govt.nz/protection-and-response/mycoplasma- bovis/advice-on-mycoplasma-bovis/advice-for-calf-rearing https://www.dairyherd.com/article/abomasal-ulcers-calves. http://www.becfeed.co.nz/. Calf Notes.com. Calf Note #115 – Abomasal pH and milk feeding. https://www.dairyherd.com/article/acid-milk-healthy-calves. https://www.publish.csiro.au/ebook/chapter/9780643107427_Chapter3
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