Mimicking Nature's Way for Milk-Fed Dairy Calves: Free-Access Feeding with Acidified Milk

Table of Contents

1. Nature's way and conventional feeding
2. Choices and benefits
3. Hunger - quantity, frequency and quality
4. Myths contribute to hunger
5. Free-access milk feeding
6. How to acidify milk
7. Purpose of acid
8. Why acidify to pH 4.0 - 4.5?
9. About pH and contact time
10. Shelf life of acidified milk
11. Does acidification alter milk?
12. Stirring is essential. It can be automated.
13. Cool milk is best. Protect from sunlight.
14. Keeping milk cool (20°C) in cold barns
15. Frequent suckling benefits calves
16. Suckling activity with free-access milk
17. Nipple to calf ratio
18. Milk intake and weight gain
19. Rearing costs
20. Benefit from early weight gain
21. Cross-suckling in groups
22. Free-access water and grain
23. Abrupt or gradual weaning
24. Health challenges with group rearing
25. Group size - 8 or fewer calves
26. Acidified milk and scours
27. Free-access milk for goat kids
28. Feeding protocols - birth to weaning
29. Summary
30. Reading list
31. Acknowledgements

Printable PDF version (1004 kb)

Take-Home Messages

1. Hunger is a major stressor and a fundamental health issue for neonatal calves.
2. It is the caregiver’s duty to prevent hunger in our animals.
   
3. Hunger can be prevented by simple changes to conventional and automatic feeding practices.
4. Free-access feeding with acidified milk is a unique way to prevent hunger in calves.

Introduction

Something old is new again - free-access feeding. It's old because it's nature's way. What's new is the way we can fulfill our ancient contract of assuring freedom from hunger for calves in exchange for milk surplus to the calves' needs. Hunger is a major stress in the early days of life of a newborn calf. It may be the main predisposing cause for sickness in the first 7-21 days. Conventional feeding strategies often leave calves hungry because our methods do not meet the standards of an average cow mother. Since June 2005, in Ontario, several hundred calves have enjoyed freedom from hunger and good health because of free-access feeding with acidified colostrum, milk or milk replacer. Moreover, the free-access feeding scheme has given joy to those caring for calves.

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Figure 1. A 'calf-maid' feeder in use on a dairy farm in Finland.

Grober Animal Nutrition imported a similar feeder in the spring of 2006. An Ontario producer has been using it for several months.

Nature's Way and Conventional Feeding Systems

Nature's way of feeding calves includes free access, nursing until satiated, frequent meals per day and suckling. Conventional rearing systems usually limit access, restrict milk intake per meal, encourage rapid feeding or gorging, restrict meals per day or provide milk in pails (non-suckling).

Restricted-access systems include housing intermittently with an accommodating nurse cow, an automatic computerized feeding system programmed in a conventional manner or bottle, pail or mob feeders with feeding 2 or 3 times per day. The origins of limit feeding in frequency and quantity of milk may have been from research showing this practice stimulates greater intake of grain at a younger age and a desire by producers to limit costs (milk vs. grain) in calf rearing.

Free-access milk-feeding systems include continuous housing with an accommodating nurse cow or unrestricted access to a container of milk. An automatic feeding system programmed for unrestricted access may still restrict access because of the calf-to-nipple ratio. The origins of free-access feeding may have been from producers or their advisors noticing improved health, greater feed conversion, rate of gain and growth in calves fed in ways that mimic nature. No doubt they also are looking for methods to decrease labour.

Choices and Benefits

Choices in feeding systems, housing and management affect health, growth and behaviour of calves and profit of a farm. Ontario producers commonly rear milk-fed dairy calves in individual pens and restrict milk feeding to 2 or 3 meals per day. In Finland, 30% of larger dairy farms and 90% of veal operations choose group housing and free-access feeding.

Finnish farmers have practical experience with free-access feeding since 1996. They use formic acid to acidify milk to preserve it for 1 to 3 days. They claim less labour, inexpensive equipment and efficient use of surplus colostrum, transition cow milk or milk from cows under treatment. They also report calves stay healthy, have few bouts of diarrhea and rarely suck on navels or ears. For Finnish farmers, free-choice feeding is an easier feeding method for substitute workers. It allows calves to eat to appetite and satisfies the calves' biological need to suckle. Of course, calves have very good growth with weight gains near 1 kg/day. Closer to home, a New York State study showed a reduction in labour per calf per day, from 10 minutes for calves in individual pens to 1 minute for calves reared and fed in group housing. The basic components of a Finnish free-access feeding system include a reservoir to contain the milk or milk replacer, a nipple, a plastic tube and a check valve (Figure 3). Acidification with formic acid preserves milk for storage at room temperature and allows them to mix batches at 1- to 3-day intervals to save labour. In addition, the milk is fed cool to avoid gorge feeding.

Figure 3 - The basic components of a Finnish free-access feeding system include a reservoir to contain the milk or milk replacer, a nipple, a plastic tube and a check valve.

In June 2005, an Ontario dairy goat producer was the first to use the free-access acidified-milk system for rearing kids. A dairy producer with cattle soon followed. Several producers set up pilot projects. They discovered practical methods of implementation and useful information about what does and does not work. A few producers tried and quit the feeding system. About 100 producers in Ontario, Saskatchewan, Alberta, Nova Scotia, New Brunswick and New York State adopted the system in the past 16 months.

Hunger - Quantity, Frequency, Quality

Hunger is a state of discomfort, queasiness or weakness caused by a lack of food. Hungry calves are in need of food. Calves display hunger by vocalizations or suckling behaviour while searching for a teat. Intersuckling on other calves may be a sign of hunger but it is often perceived as unwanted behaviour.

Modern calf raisers often use socialistic feeding strategies. They feed all calves the same volume, regardless of the calf's body weight. Consequently, the heaviest calves often suffer from hunger. In comparison, calves suckling their dams consume milk to their needs.

Figure 4 is a graph that shows the average daily gain or loss at 7 days of age for 179 Holstein bull calves fed 4 liters of milk per day. The calves are sorted by birth weight from left to right (33 to 62 kg). Fully 44% of calves greater than the median weight of 46 kg did not gain or lost weight in their first week of life on the restricted-milk feeding scheme.

Figure 4. Average daily gain or loss at 7 days of age for 179 Holstein bull calves fed 4 liters of milk per day.

Conventional feeding strategies often provide less milk than calves would consume with free access to a nurse cow. Despite their greater total daily consumption of milk, suckling calves appear to have fewer problems with scours.

Table 1. A comparison of conventional calf feeding to suckling or free-access systems shows that we fail to meet the standards of an average cow mother. Our conventional feeding practices usually fall short in quantity and frequency of feeding and missed potential for weight gain. The comparison supports the argument that hunger is a prime issue for calves 1-21 days of age.

In addition to quantity and frequency, we may fail to deliver milk of sufficient quality to our calves. With milk replacer, the most common error is in mixing an inadequate weight of powder per liter of water. With whole milk, some choose to dilute it with water. However, bacterial quality may be just as important an issue.

Figure 5. Waste milk, colostrum and prepared milk replacer can be found stored in pails at room temperature on some farms. This milk incubates bacteria and becomes a cesspool for calf feeding. The same can be true for large volumes of milk stored in refrigerators. Without stirring, only milk at the periphery of the pails is adequately chilled while milk towards the center remains warm and incubates bacteria.

Myths Contribute to Hunger

Myths are collective opinions or beliefs that are often based on false premises. Several myths about calf feeding, when put into practice, contribute to hunger of calves. The first is 'too much milk causes scours or too much milk is bad for calves.' It's the reason milk is restricted or diluted with water. Gorge feeding large volumes of milk may be the real issue. Experience has shown that calves thrive on more milk than offered with conventional feeding. However, a greater volume per day must be consumed in several small meals to avoid hazards of gorge feeding.

'Too much milk powder causes scours' is on the same theme. This may have been true years ago when soy was a major component of milk replacers. Soy ingredients cause an allergic reaction in the intestinal tract and diarrhea in young calves. However, most modern milk replacers are made with all-milk components. They are the best choice for your young calves. The too-much-powder myth led to producers using insufficient amounts of milk replacer powder per liter. With most quality milk replacers, about 125 - 150 grams of powder per liter will yield a solids content close to that of whole milk.

The last myth has to do with willingly withholding milk from calves - the '10% of body weight per day' myth. Someone devised this feeding strategy to stimulate calves to eat grain. For sure, they will eat grain when starved of milk. However, grain intake for calves fed milk at 10% of body weight is no greater in the first 14 days of their life than calves that have free access to milk. Further, the young calf needs and uses milk as a food source and not grain in its early days. Experience with free-access feeding shows the dogma to be unfounded and detrimental to calves.

Free-Access Milk Feeding

Free-access feeding systems allow calves easy and unconstrained freedom to consume milk. The system allows calves to suckle milk when and as often as they choose. In an individual pen, a calf could suckle without interference from other calves. In group pens, it is essential to have several nipples available to limit the number and frequency of displacements of calves from nipples. Unlike most computer or automatic feeding systems, several calves in a group can suckle at the same time. Access to nipples and milk is not controlled, restricted or hampered by external influences.

The system requires unrestricted access to quality milk and at temperatures suitable for calves to drink. Reservoirs of colostrum, milk or milk replacer require preservation. Acidification is one easy way. Another is souring with specific bacteria. In Finland, at least one field trial used REDI-SET™ dairy culture to acidify milk.

The least expensive equipment includes an electric drill and paint mixer attachment to mix the milk and preservative, a container to hold a reservoir of milk and teats on the container or attached to a feeder bar on a wall. The system may be gravity fed with teats at the bottom of the container or line-fed with teats attached to a plastic line with a one-way valve.

Figure 6. A line-fed system may have teats attached to the reservoir or remotely from the container. The size of container depends upon the number of calves given free access to the milk and the frequency of filling. It could be a 20-liter pail for a single calf or 100-200 liters or more for several calves.

Free-access feeding systems can be automated with mixers on timers or recirculation pumps to deliver milk from one reservoir to several groups of calves and back to the reservoir. Free-access feeding is also possible with some computerized feeding systems that have a milk reservoir. Free-access systems are suitable for individual or group-housed calves. In general, acidified milk may be prepared at 1-3-day intervals and the equipment cleaned twice per week. The use of a preservative (acidification to pH 4.0 - 4.5) and feeding at a cool (20°C in winter) temperature (to limit intake per meal) are essential to the success of free-access feeding systems.

How to Acidify Colostrum, Milk or Milk Replacer

1. Prepare dilute acid

• Mix 1 part concentrated
  Formic Acid 85% into 9 parts water.
• For example, put 9 L water into a container; then add 1 L of Formic Acid 85%. (Figure 7) Mix.
• Label clearly - Dilute Formic Acid. Caution - Irritating to skin, eyes and lungs. Keep out of reach of children. Mixing Directions: While stirring vigorously, add 30 mL to 1 liter of whole milk or milk replacer. Mix 40 - 45 mL to 1-liter colostrum. Check pH 4.0 - 4.5.

2. Cool the colostrum, milk or milk replacer before adding dilute acid

• to avoid clot formation.
• Warm milk may be acidified. It separates quicker and requires vigorous and frequent stirring. Use an electric drill and paint stirring attachment for vigorous stirring.

  

3. Mix dilute acid into colostrum, milk, or milk replacer

Mix 30 mL dilute acid into 1 liter (1000 mL) milk or milk replacer. Add 40 to 45 mL dilute acid to 1 liter colostrum. Check pH 4.0 to 4.5.

Mix 150 mL dilute acid into 5 liters milk.

Mix 300 mL into 10 liters

Mix 450 mL into 15 liters

Mix 600 mL into 20 liters

4. Stir vigorously while adding acid. Stir again within an hour and, then, 3 times through the day.
   (Figure 8) Use a paint mixer and brisk speed on a cordless drill.

5. Check to assure within the range of pH 4.0 to 4.5 when mixing is complete. (Figure 9)

6. Feed at ambient temperature in the summer.Feed at 20°C in winter. Do not warm the milk.

7. Store in closed containers for 1 to 3 days. Prevent entry of flies/cats into milk.

8. Clean nipples, valves, lines, and container with warm water and dish washing detergent.

9. Provide free-choice water and calf starter.

10. Mount nipples 24 to 28 inches above floor level
    for calves.

Purpose of Acid

Acidification to pH 4.0 - 4.5 is to preserve the milk/milk replacer. Once preserved from growth of bacteria and molds, the milk can be stored at room temperature for several days. Proper preservation permits free-access feeding of milk to calves without the need for refrigeration of the milk. Acidification decreases a calf's exposure to bacteria because it decreases the bacterial load in milk or milk replacer. It may be useful for storing surplus colostrum or waste milk when refrigeration is not available. There may be merit in acidifying surplus colostrum prior to storage in freezers.

Acidification does not inactivate or kill all bacteria found in milk. However, acidification at a target pH of 4.0 - 4.5 and contact time of 8-12 hours will produce milk that meets or exceeds quality targets for feeding calves.

Why Acidify to pH 4.0-4.5?

Standard textbooks of laboratory procedures show that many bacteria and molds will not grow at pH less than 4.5, but they survive and reproduce readily at pH levels greater than 4.5. To test the theory that acidification (pH 4.0 - 4.5) preserves milk, we conducted standardized Plate Loop Count bacterial cultures on control and acidified bulk-tank-milk samples stored at room temperature. Bacteria multiplied quickly in the control sample and colonies became too numerous to count, whereas the acidified sample showed no bacterial growth after several hours of contact with formic acid and pH of 4.2. However, upon repetition of the experiment, we found some bacteria survive acidification.

The effects of acidification on Mycobacterium avium parTB (Johne's) are unknown. We are hopeful that a University of Guelph researcher will soon answer the question.

Table 2. The table lists several bacteria of interest on dairy farms, the optimum and range of pH for their growth, and the pH at which they are inactivated or lose their activity under laboratory conditions. The recommendation to acidify milk to pH 4.0 - 4.5 is logical when one considers the information in the table.

	Optimum	Range	Inactivated/last activity
Bacillus cereus		4.3 - 9.3	< 4.3 and 9.3
Clostridum perfringens	6.0 - 7.0	5.5 - 9.0	< 5 and > 8.3
Clostridium botulinum		4.6 - 9.0	<4.6 and >9
E coli (STEC)	6.0 - 7.0	4.4 - 9.0	<4.4
E coli 0157:H7	6.0 - 7.0	4.4 - 9.0	<4.4
Lactobacillus acidophilus	5.8 - 6.6	4.0 - 4.6 - 6.8	<4.4*
Listeria monocytogenes	7.0	4.4 - 9.4	<4.4
Mycobacterium avium para TB (Johne's)	6.0 - 7.0	5.0 - 7.0	< 5 no growth
Pseudomonas aeruginosa	6.6 - 7.0	5.6 - 8.0	<5.6
Salmonella	7.0 - 7.5	3.8 - 9.5	<4.4*
Staph aureus	7.0 - 7.5	4.2 - 9.3	<4.2
Strep pneumoniae	7.8	6.5 - 8.3	<4.5
Vibrio cholerae	7.6	5.0 - 9.6	<4.5

About pH and Contact Time

Acidification creates unfavourable conditions for growth or survival of many bacteria. The effect does not happen immediately. It takes time. The contact time varies with the bacterium and the pH.

In the summer of 2006, we conducted experiments using whole milk from a few cows. We found no growth of coliforms after a contact time of 1 hour at pH 4.1 in whole milk acidified with formic acid. We found no growth of Staphylococcus aureus after a contact time of 4-6 hours at pH 4.1 in whole milk acidified with formic acid.

Next, in 2006, we collected acidified milk from containers on 24 farms (Figures 10 and 11). We found 81% of 46 milk samples were in the target pH range of 4.0 - 4.5. On bacterial culture, the majority of samples had no growth or less than 1000 colony-forming units per millilitre (cfu/mL) of milk. Thirty-one of 48 samples had no coliform growth. We found environmental Staphylococcus and Streptococcus in less than half the samples and at levels of 1-5,000 cfu/mL.

Figure 10. In our study of acidified milk from 24 farms, laboratory staff reported results as no growth and in ranges of less than 500 colony-forming units per mL (cfu/mL) of milk, 600-1000, 1100-5000 and greater than 5000. The graph shows the number of samples that fall within those ranges for three bacterial species - Staphylococcus, Streptococcus and coliforms. The majority of samples had no growth or less than 1000 cfu/mL of milk. Thirty-one of 48 samples had no coliform growth.

Equivalent of Graphic

There is scant information to predict the precise contact time needed to inactivate specific bacteria common in milk, waste milk, colostrum or milk replacer. However, with limited experience, 6-12 hours seems appropriate. In practical application, acidify milk in the afternoon and feed it the next morning.

Figure 11. In our on-farm study, the hours of contact time with acid at the time of milk sample collection ranged from 1 to 48 hours for the bacterial cultures shown in Figure 10. The contact times reflect the frequency of mixing acidified milk. Although pH is important for inactivating bacteria, adequate contact time also is essential.

Equivalent of Graphic

Shelf Life of Acidified Milk

Shelf life will vary with pH and ambient temperature. Finnish farmers and advisors recommend preparation of batches every 1-3 days. A survey of 24 Ontario producers found they commonly mixed batches at 1-2-day intervals. One producer mixed at 3-4 day intervals. Nonetheless, no one has determined the storage life of acidified milk under farm conditions.

Does Acidification Alter Milk?

The most obvious change to colostrum, milk or milk replacer (milk) is separation that happens within 10-30 minutes after acidification to pH 4.0 - 4.5. It is like gelation seen in making yogurt.

Figure 12. The photographs show the separation (gelation) that occurs with milk acidified to pH 4.2. Similar separation occurs with colostrum, milk or waste milk. The separation is more rapid with warm or hot (?30°C) milk. We used an all-milk replacer, 22% protein and 17% fat and mixed at 150 g/L. All samples looked like the control sample after a vigorous stir. It is essential to stir acidified milk 2-4 times per day to keep the constituents in solution.

Those feeding acidified milk must stir the mixture about 30 minutes after preparation. Subsequently, the milk will separate again after several hours. Therefore, it is necessary to stir vigorously 2-3 times per day thereafter. Published research reports show no harmful effects of acidification to colostrum or fat, protein or lactose in milk. At a recent on-farm demonstration, a volunteer stated that the acidified milk tasted different and that the control sample would be his first choice. Nonetheless, calves drink the acidified milk readily. Any slight change in taste may be beneficial to limit intake in free-access feeding systems.

In the 6-8 hours immediately following acidification, milk will separate again and require stirring. However, when stirred vigorously 8 hours after acidification, I found milk stayed in a uniform mix for 12 to 18 hours. A practical approach would be the use of an automatic mixer set on a timer. An alternative for hand stirring the milk would be to prepare the acidified milk in the morning and serve it in the evening following a good stir.

Figure 13. The photograph shows the control sample and the Formic Acid and Agri Acid samples at 7:30 a.m., 15.5 hours after a vigorous stir at 4:00 p.m. the previous day. Although not shown, the AcidPak samples looked similar.

Stirring is Essential and it can be Automated

Timely stirring of acidified milk assures calves receive a consistent mix when they suckle. Since acidified milk gels and separates, timely stirring is essential. Vigorous stirring at high rpm for a short duration will achieve excellent mixing.

Figure 14. An electric drill and a paint stirrer attachment do a very good job of mixing. Several producers made mixers to insert into their electric drills. It is essential to select a mixer for the size of the container and volume of milk. For example, the smallest commercially available paint mixer is not adequate for mixing milk in 20-L pails or 100-L barrels.

One producer uses a 12-volt diaphragm pump that circulates milk through a line feeding nipples at individual calf pens. The pump is on the return side of the line because this location prevents milk leakage at the nipples. Milk exits from the bottom of the barrel and enters the top.

During the summer months, a producer fed free-access milk to his calves in hutches. The acidified milk is in a pail hanging on a hook suspended from the top of the hutch. The calf feeder simply gives the pails a vigorous shake a few times a day. The calves also shake the pails while nursing.

A pond pump stirs milk replacer at one farm I visited. The pumps are available at garden centres, come in various sizes, and have a pre-filter to prevent clogging of the pumping mechanism.

Figure 15. At a Milverton-area farm, a dose of old-fashioned ingenuity from a young farmer assures an even mix throughout the day. His storage and mixing system consists of a barrel, a 1/3-HP motor to drive a mixer and two timers to control frequency and duration of mixing. The motor mounts to a lid. A cart makes easy work of moving the barrel for washing and filling. Cables attach to the lid in three locations and they support the mixer above the barrel when moving the barrel away.

Cool Milk is Best and Protect From Sunlight

Cool (20°C) milk limits intake. In effect, it prevents gorge feeding. Researchers compared health, feed conversion and rate of gain in calves fed cool and warm milk. The calves fed cool milk had the best performance in all three categories. Calves fed cool milk have fewer days with scours than calves fed warm milk. Calves housed in barns with moderate temperatures have similar performance when fed either cool or warm liquid diets.

Calves will drink cold (<10°C) milk but they shiver after feeding. Calves shiver to regenerate body heat lost when they drink cold milk. Cold milk is a poor choice for calves housed in cold barns. Research showed calves housed at temperatures <5°C and fed milk at 10-15°C had less weight gain (12%) and less feed efficiency (13%) than calves fed milk at 35-38°C.

Closer to home, a producer on a pilot project fed his calves and goat kids milk warmed with hot water circulating through a coil at the bottom of the barrel. The young animals developed scours within 24 hours. However, diarrhea stopped within a day after removing the heater from the milk. At an outdoor farm show, we exposed our milk container to direct sunlight. While looking for reasons for sudden onset diarrhea in our calves, we found the milk was hot to touch. We made a cool batch of milk, shaded it from the sun and scours stopped. These practical experiences indicate that hot, acidified milk leads to diarrhea. The reason is unknown. Therefore, I recommend feeding at temperatures close to 20°C in winter. During the summer, feed at ambient temperatures and protect the containers from direct sunlight.

Keeping Milk Cool (20°C) in Cold Barns

During the winter of 2005-6, some producers let milk chill to ambient temperatures that often hovered between 3-10°C. Their calves drank the cold milk (slowly) and shivered from the chill, yet they thrived in the system. Others experimented with various heat sources to keep milk from freezing yet cool in their cold calf barns. Those who built and heated an insulated enclosure for the milk container seemed most pleased with their system. They kept milk cool by placing containers inside insulated boxes and adding supplemental heat to warm the miniature room. One producer used discarded chest-type food freezers. They have insulation and a good fitting lid. He located the freezers adjacent to calf pens to keep lines short. In a pen for 1-3-day old calves, he mounted nipples directly on the outer wall of a small apartment-sized freezer. Heat lamps or small thermostatically controlled electric heaters keep the air and milk within the chest at an appropriate temperature.

Figure 16. Free-access feeding is possible in cold calf housing. The challenges are to protect milk and milk lines from freezing, and maintain milk at 20°C. The photograph shows a chest freezer with short lines to nipples. The insulated freezer retained heat generated by a thermostatically controlled heater. The chest contains milk in short barrels.

To date and to my knowledge, no one in Ontario has found a satisfactory submersible heater for use in milk. Stock tank heaters prevent freezing but do not heat to 20°C. Pail heaters are too hot and cook milk on the element.

A producer in Northern Ontario built a large milk container and placed it within a warm water bath. Producers have tried circulating hot water from hot water tanks through coiled copper tubing in the milk. Early attempts with this device failed because the water was too hot.

Another producer has a heated milk preparation and storage room with four pens, 2 on either side. His milk containers are inside the warm room. Milk lines exit through the insulated wall to nipples mounted on the other (calf pen) side.

Our attempts at temperature control with industrial band heaters for steel barrels were not successful. We melted plastic containers. A waterbed heater has been working for an Eastern Ontario producer.

Figure 17. The photograph shows an aquarium heater used to warm water within a 3-inch plastic pipe submersed in milk. This heater maintains the temperature of freshly prepared milk replacer. Aquarium heaters are available in numerous sizes. A "pond pump" (not shown) used in garden applications, keeps the milk mixed in this barrel.

A few producers are considering the use of old bulk milk tanks. They plan to maintain milk temperature by circulating warm water through the copper lines normally used for cooling.

Figure 18. The photograph shows a 'calf-maid' feeder manufactured in Finland by FinnLacto OY. It has an automatic mixer and temperature control. The robust tires make an easy task of moving 200-300 L of milk.

Frequent Suckling Benefits Calves

Prevention of abomasal ulcers or abomasitis in suckling calves presents challenges to veterinarians and their clients. The commonly proposed etiologies for abomasal ulcers include mechanical abrasion from coarse ingesta, infection with Clostridium perfringens Type A, trace mineral deficiencies and stress. Because of sudden deaths or unrewarding treatments, it is important to control or prevent ulcers. Feeding frequency could be a preventive measure.

Researchers at the University of Illinois set out to find practical treatments. They speculated that long periods of low pH in the abomasum could increase the chance of injury to the abomasal mucosa. Further, they wondered if feeding frequency had an effect on abomasal luminal pH and the risk of ulceration. The researchers discovered changes in abomasal pH with different schedules for feeding milk replacer. From their findings, they advise increasing feeding frequency to prevent abomasal ulcers in suckling calves.

Figure 19. The graph shows the least squares mean abomasal luminal pH in dairy calves (n=6) that suckled milk replacer at 3-h intervals (8x; O_O) and 12-h intervals (2x;__). Open symbols at the top of the graph represent values that were significantly (P <0.05) different at the same time. Bar represents the overall standard error (SE) for least squares means. (Ahmed AF, 2002)

The graph shows that frequent suckling succeeded in reducing the number of hours per day that the abomasal lining was exposed to low pH. However, it also shows abomasal pH was less than 5.5 for the entire day. A quick look back to Table 2 shows that Clostridium perfringens prefers a pH of 5.5 - 9.0 for optimum growth. Frequent suckling seemed to assure that the optimum pH for that growth was not achieved. Further to the argument, free-access feeding of acidified milk could be of benefit because the milk entering the abomasum is at a pH less than 4.5.

Suckling Activity with Free-Access to Milk

In the summer of 2005, we recorded on video tape the feeding activity for 8 calves on free-access feeding. The calves were in groups of 4 with 3 nipples per 4 calves.On average, our study calves ate 7 meals with a range of 4-14. None chose less than 4 meals per day. The calves suckled for an average of 48 minutes per day with a range of 35-70. None chose 5-10 minutes. An average suckling bout was 7 minutes with 75% of suckling bouts greater than 5 minutes. The calves clustered most meals between 4:00-7:00 hours and 17:00-22:00 hours with a smaller cluster between noon and 15:00 hours.

Figure 20. For 8 calves on free-access feeding, the average interval between meals was 4 hours with 65% of meals at less than 5-hour intervals. Fully 43% of meals were at less than 3-hour intervals and 16% at greater than 7 hours. None chose to suckle at 10-16 hour intervals.

Nipple to Calf Ratio

Since calves have the herd instinct to eat and rest as groups, it is advisable to provide ample nipples for feeding. Finlanders recommend at least 1 nipple for 3 calves. An abundance of nipples assures that older or stronger calves will not displace smaller or timid calves from nursing opportunities. Older calves teach young calves by example. The youngest calves explore what the older calves are doing and quickly learn from them. Free-access feeding implies a nipple and milk are available when wanted and, in general, there should be no waiting for milk. Research from British Columbia showed reduced time on teats, reduced daily milk intake and increased competitive displacements from teats with reduced access to teats (4 teats : 3 calves vs. 1 teat : 3 calves).

Milk Intake and Weight Gain

From textbook references, calves can drink 20-25% of their body weight daily. On free-access feeding, in the first week of life, Holstein calves will drink 6-8 liters of milk each day. Prior to weaning at 5-6 weeks, calves may drink 12-15 liters of milk per day. Researchers in British Columbia (BC) documented an average intake of 11 liters per day during a 27-day feeding period from 5-32 days of age. On average, their calves gained 1.1 kg per day. In another BC experiment, researchers found teat-fed (free-access) calves drank 8.8 liters per day in the first two weeks of life. In general, when given the opportunity, calves will consume about 20% of their body weight in milk. This is double the common recommendation or practice on most farms.

Rearing Costs

Since calves consume more milk, there will be greater costs associated with milk or milk replacer. However, reports show the investment in milk or milk replacer is offset by better health and fewer treatment costs, thus giving the advantage to the free-choice fed calves compared to calves on restricted feeding. There may be less time treating sick calves and more or equal time in feeding-related activities.

Benefit from Early Weight Gain

Since there is no research on the subject with free-access feeding of acidified milk, we could learn from research about accelerated milk replacer programs. Recently, researchers suggest a benefit to the immune system from enhanced feeding of young calves. Weight gain during the first 4-6 weeks of age has no harmful effect on future milk production. Calves will be taller at weaning than those on restricted feeding. In addition, calves will show estrus about 2 weeks earlier and subsequently breed earlier. Calves raised on 'accelerated' milk replacer programs have been shown to produce more milk during their first lactation.

Cross-Suckling in Groups

With Holstein calves, inter-suckling has not been an issue. It is a very rare event in groups with free-access feeding. The reason may be an abundance of teats, so several calves can feed at the same time, and the ability to feed (suckle) until satiated. The exception has been Jersey calves at weaning as shown at one farm on a pilot project. They started cross-suckling behaviour (especially for urine) after abrupt weaning. At least one research report suggests hunger is the reason for the behaviour. Calves should have free-access to salt, grain or starter pellets, hay and water during the milk-feeding stage.

Figure 21. Jersey calves shown in this photograph did not cross-suckle while on the free-access feeder. However, some did when weaned abruptly or gradually. Producers report cross-suckling is not an issue with Holstein calves before or after weaning.

Free-Access Water and Grain

Calves must have free-access to clean water and a starter ration of grain or pellets at all times while on the acidified milk feeding program. This advice is the same as for other feeding systems. Although seldom practiced, it may be beneficial to provide these young calves with access to a salt lick. The intake of pellets will increase noticeably during the fourth week of age. Calves on free-access feeding do not consume as much starter as calves on restricted feeding. However, post weaning, the free-access calves quickly consume quantities of starter similar to calves on restricted feeding. Recent research indicates that offering hay is not harmful to rumen development contrary to commonly held beliefs from earlier research studies.

Abrupt or Gradual Weaning

Abrupt and gradual weaning are possible. Gradual weaning over a 7-day period is the preferred method. Producers report some separation anxiety from the teat. However, calves appear to suffer no greater setback at weaning than calves weaned from conventional feeding systems. To wean gradually, make the milk replacer with more water and less powder or dilute whole milk with water. Water alone could be the only liquid available by teat at the time of weaning.

Health Challenges with Group Rearing

Respiratory disease and diarrhea are the greatest health issues for neonatal calves. Some say pneumonia is more common with group rearing. Housing in individual pens or hutches became popular as a way to separate calves and diminish the risk of diseases. Recent research from Sweden looked at the effect of group size on health and growth rate of Swedish dairy calves housed in pens with automatic milk-feeders (Svensson and Liberg, Prev. Vet. Med. 73, 2006). The authors stated that "calves in pens for 12-18 calves had a higher incidence of respiratory illness (Odds Ratio: 1.4) and grew 0.022 cm/day less than calves housed in groups of 6-9 animals (equivalent to approximately 40 g/day). We detected no differences between calves kept in the small-sized versus the large-sized groups in terms of risk of diarrhea."

At least three Ontario producers tried unsuccessfully to rear calves in large groups housed in barns with ventilation challenges. Their calves began to cough, so they wisely switched back to hutch rearing. Ventilation can be a challenge in controlled-environment calf barns. At one farm, tearing from eyes and coughs stopped when the owners dropped relative humidity from 65% to 50% and set the temperature at 10-11°C. Testimonial evidence from 24 Ontario producers indicates diarrhea is less frequent with free-access feeding of acidified milk than with their previous feeding systems.

Group Size - Limit to 8 or Fewer Calves

Our recommendation is 8 or fewer calves per pen. It is based on the Swedish research and experience at pilot project farms in Ontario.

Figure 22. A sample of 24 Ontario farms using free-access feeding showed they had an average of 4 calves per pen. The number of calves per pen ranged from 1 to 10. Fully 31 pens/hutches were for individual calf housing. Five pens had 10 calves in a group, 8 pens had 5 calves in each group. The number of pens for individual calves skewed the average. In general, it was most common for group size to be 5-8 calves. Pen area per calf varied from 12-75 square feet, with an average of 29 and median of 25.

Acidified Milk and Scours

In Finland, advisors recommend feeding acidified milk for farms experiencing diarrhea problems in their calves. They claim acidified milk prevents diarrhea. Calves can eat as much as 9 to 12 liters a day with free-choice feeding. At these feeding levels, the consistency of feces is loose but the situation is different from a serious diarrhea caused by bacteria. Diarrhea has not been reported as a problem on the pilot-project farms. Indeed, the owners report scours as a rare event with free-access feeding. However, diarrhea was a problem on 3 pilot-project farms where producers fed hot acidified milk. The calves responded without treatment after the producers fed cool milk. Since acidification decreases the bacterial population in milk, acidified milk should provide a reduced hazard to calves.

In a previous section about frequent suckling, I argue that milk acidified to pH 4.0 - 4.5 should have a benefit for calves, especially when one considers Clostridium perfringens Type A. This bacterial agent is being diagnosed with increasing frequency in calves with abomasitis and sudden death. Since its optimum range for growth is pH 5.5 - 9.0, milk entering the abomasum at pH 4.5 should produce an inhospitable environment for Clostridial growth and sporulation in the abomasum. For sure, research would be helpful to prove or disprove this theory. At best, frequent feedings or feeding acidified milk should be considered as a prevention strategy because other means of prevention have been unrewarding.

Viruses are notoriously resistant to acids. I have not found information related to acidification of milk and survival of Enzootic Bovine Leucosis virus or Bovine Virus Diarrhea virus.

Free-Access for Goat Kids

Free-access feeding of acidified goat's milk, cow's milk and milk replacer to goat kids has been very successful on several Ontario farms.

My first experience with the feeding system was with goat kids at a large dairy. Death loss in the kids was 32% and most deaths were related to scours that started at 7-10 days of age. Challenges with colostrum quality (late harvest), undernourishment (thin body condition), engorgement stress (pot bellies after feeding) and diarrhea were identified and addressed with a feeding protocol designed to mimic normal feeding behaviour. An ad libitum feeding system allowed kids to suckle small quantities at each feeding episode. The intention also was to improve consumption of colostrum and transition milk in the first few days of life and to overcome the stress of hunger. The scheme included harvesting colostrum immediately after freshening of the doe, feeding the newborns warm fresh colostrum at birth, chilling the remaining colostrum and then acidifying it, and feeding acidified colostrum for the next few days after birth of the kids. In addition, subsequent feedings included acidified milk and/or milk replacer for the first 3 weeks of life.

Figure 23. Newborn goat kids suckling acidified milk with free access. From implementation of the new feeding scheme, at one farm, to the end of kidding season, death loss dropped from 32% to 3% in 2005. In the 2006-kidding season, owners fed acidified colostrum, milk and milk replacer for the first 3 weeks of age. Their records for 2006 showed death losses of less than 6% for all causes in the neonatal kids.

Feeding Protocols from Birth to Weaning

Many advisors recommend feeding 4 L of colostrum to calves either by suckle bottle or by stomach tube. Producers often remark that the calves fed 4 L will not drink for several hours or a day following this large meal. Free-access feeding provides an opportunity to feed newborn calves several smaller meals during the first few hours when the gut is open to antibody absorption. The following protocol has been working successfully on pilot-project farms. The protocol takes full advantage of the benefits of colostrum and fresh cow milk. It may not be applicable to those on Johne's control programs.

Feeding newborn calves - birth to 2 to 4 days

• Within 1 hour of calving,
• harvest colostrum from the fresh cow.
• feed the newborn calf at least 2 liters of fresh colostrum.
• use a nipple bottle.
• cool (<10°C) the remaining colostrum.
• acidify the remaining colostrum with dilute formic acid.
• store the acidified colostrum in containers with lids
• 2 to 4 hours after the calf's birth - feed acidified colostrum by nipple.
• Move the calf to its individual or group housing pen;
  • provide free-choice access to acidified colostrum.
  • be sure the calf is suckling the acidified colostrum.
  • feed acidified colostrum and fresh-cow milk for 2 to 4 days.
  • provide free-choice water and grain.

   

Feeding post-colostrum to weaning - whole milk or milk replacer

• House calves in groups;
  • put 2- to 4-day-old calves (off colostrum) into group pens.
  • prepare the 'milk' with dilute formic acid as per instructions.
  • mix enough 'milk' for 1 to 3 days.
  • calculate 8 to 12 liters per calf per day for pens of calves of mixed ages (1 to 6 weeks).
  • stir the 'milk' for 10 to 15 seconds at least 3 times per day.
  • be sure each calf is nursing the nipple.
  • use containers with lids to keep flies and cats out.
  • clean the equipment with warm water and dish washing detergent.
  • provide clean, fresh water free choice.
  • provide fresh calf starter - grain - free choice.
  • remove weaned calves from the group at 5 to 7 weeks of age.
  • Provide 1 teat per 3 calves, minimum recommendation.
  • Restrict group size to 8 calves maximum.
  • Soft feces should be considered normal for calves fed free-choice liquid diets.
  • Abrupt weaning may be necessary.
  • Gradual weaning is the preferred method.

Figure 24. Calves exhibit group feeding behaviour similar to cows at a feed bunk. There should be enough teats available to enable several calves in a pen to suckle at the same time. In groups of 6 - 8 calves, 4 nipples should be adequate.

Summary

Conventional milk-feeding systems have worked well on Ontario farms. However, cow numbers and calf numbers are increasing as our dairy farms increase in size. There is considerable labour devoted to feeding of individual calves and the labour issue has producers looking at alternative feeding systems. Hutch rearing has proven itself for calf health but is falling into disfavor by those feeding calves during miserable weather. Mob feeders, free-access feeding and automatic (computerized) feeders are choices to consider for feeding calves as groups. The main challenge becomes the prevention and control of respiratory disease in group housing systems. Confinement housing, with controlled heat and ventilation, includes additional expense in rearing and challenges with respiratory disease. Group rearing in green-house type shelters with wind screens could be adapted to group feeding systems. Calves thrive in cool temperatures but the equipment for feeding must be protected from freezing. That is where we need some innovations to make free-access or automated feeding an alternative on larger farms.

For more information, please refer to the INFOSheet, Free-Access Feeding of Dairy Calves and Kids Using Colostrum, Whole Milk or Milk Replacer Acidified with Formic Acid

Reading List

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Acknowledgements

• Dr. Laura Kulkas and her colleagues at Valio Dairy, Jouni Pitkäranta and several Finnish dairy-farm families showed me calf rearing in Finland, February 2005. Heikki Kemppi at Valio continues to provide answers to questions based on 10 years experience with feeding acidified milk to calves.
• Jenny Montgomery and Tyler O'Neill, OMAFRA 2005 summer-experience students, collected data about calf behaviour when suckling free-access acidified milk.
• Several owners and managers of dairy cattle and goat farms implemented pilot projects to further our understanding of free-access feeding. They have been excellent on-farm researchers and teachers.
• Jennifer Garner, OMAFRA 2006 summer-experience student, collected milk samples and survey data at 24 farms. Dr. Anna Bashiri, Mastitis Research Laboratory, Department of Population Medicine, Ontario Veterinary College, University of Guelph, provided laboratory services. Twenty-four Ontario dairy producers welcomed us to their farms to study their free-access feeding systems.
• Mr. Grant Gould, Grober Animal Nutrition and Mr. Steve Wilson, Halchemix Canada, contributed valuable information from their free-access feeding projects across Canada.