Choosing a liquid feeding programme: whole milk or commercial milk replacer?

Factors to consider when selecting a liquid feeding programme:

• number of calves fed
• economics and cash flow
• nutritional characteristics
• calf performance targets
• resource availability e.g. consistent supply of non-saleable milk
• infectious disease control concerns
• personal preferences

The choice to feed milk replacer, instead of saleable whole milk, is often an economic decision, because the cost associated with feeding a commercial milk replacer is usually lower than that of feeding saleable whole milk. In addition to these economic considerations, today’s high quality commercial milk replacer products offer several benefits, including day-to-day consistency, ease and flexibility of storage, mixing and feeding, disease control and good calf performance.

However, there may be performance benefits for feeding whole milk.

Comparison daily weight gain of calf fed milk replacer and whole milk
45kg calf	Megacalories of ME consumed/ day	Weight gain grams/ day
1 pound DM/day of conventional 20:20 milk replacer	2.47	289
1 gallon whole milk/ day	2.97	446

In addition to supporting improved rates of gain, this improved energy intake may also be particularly valuable to the calf during periods of cold stress, when the ambient temperature is less than 50°F, and may also support improved immune function and health of the calf.

Feeding raw non-saleable milk (discard/ waste milk) represents one way to gain important economic and nutritional efficiencies but can introduce the risk of infectious diseases to dairy calves. It may contain bacterial pathogens such as Mycobacterium avium subsp. paratuberculosis (the agent causing Johne’s disease), Salmonella spp., Mycoplasma spp., Listeria monocytogenes, Campylobacter spp., Mycobacterium bovis, and Escherichia coli.

In addition to possible pathogen transmission, another concern with feeding non-saleable milk is the possible harmful effects from endotoxins that may be found in mastitic milk. It is generally safe to feed mastitic milk or colostrum to calves except for newborn calves, due to concerns about greater permeability of the newborn’s intestine to bacteria or toxins.

One additional concern relates to exposure of calves to antibiotic residues that may be found in low concentrations in non-saleable milk, leading to meat residues and, possibly, shedding of antimicrobial-resistant bacteria. Producers feeding calves non-saleable milk that may contain antimicrobial residues will need to assign an appropriate meat-withhold time after weaning, prior to marketing of calves for slaughter.

Pasteurising non-saleable milk to reduce risk of pathogen transmission

The recent introduction of commercial on-farm pasteurisation systems offers producers a method for reducing the risk of pathogen transmission and can be a viable economic strategy for feeding dairy calves.

Pasteurisation is simply a process of heating milk at a target temperature for a given duration of time, resulting in a reduction in the concentration of viable bacterial. However, pasteurisation should not be confused with sterilisation. Some heat-tolerant -- usually non-pathogenic -- bacteria will survive the process.

Commercial batch pasteurisers are typically the simplest and least expensive. They are comprised of a container, an agitator and, depending on the design, a heated water jacket surrounding the container or a heating element and stirring device submerged in the liquid. Commercial units offer thermostatically controlled automation, which simplifies operation. Milk is heated to the target temperature of 145°F, held there for 30 minutes, and then automatically and rapidly cooled to 100 to 110°F prior to feeding. These systems must be constantly agitated to allow for even heating of the milk. Cleaning of batch systems is usually manual. Batch systems can range in capacity from 1 to over 150 gallons of milk and can also be used for heat-treatment of colostrum. One concern with batch pasteurisation is that it may take several hours to heat very large volumes of milk up to the target temperature, for example, more than 75 gallons per batch. In such circumstances, as may be the case with large farms feeding a large number of calves, it may be more efficient to use a larger capacity, continuous flow pasteuriser. While non-automated batch systems can be purchased or built for as little as a few hundred dollars, most automated systems currently cost $5,000 or more, depending on capacity.

Commercial continuous flow pasteurisers have captured a large portion of the market on very large dairies due mainly to speed and automation of processing and cleaning. This equipment is comprised of a plate or tube heat exchanger in which hot water is used to heat milk on the opposite side of a metal plate or tube. Circulating milk is rapidly heated to the target temperature of 161°F and held there for 15 seconds, then rapidly cooled to 110°F prior to discharge and feeding. It is recommended that equipment possess a valve which will divert milk back through the pasteuriser if it has not reached an adequate temperature. These systems are also often called flash pasteurisers or high temperature, short-time (HTST) pasteurisers. Newer HTST systems will have the option of an automated clean-in-place (CIP) wash system. Automated commercial HTST systems can currently be purchased from $9,500 to more than $50,000, depending on capacity.

Studies have reported that both batch and HTST pasteurisation is effective in destroying viable bacteria for most of the pathogenic species threatening calves. The ability of pasteurisation in destroying Mycobacterium avium subsp. Paratuberculosis (Map), the organism causing Johne’s disease, remains controversial. A few researchers using in-lab simulations of HTST pasteurisation have reported that small numbers of the organism may survive if the milk is inoculated with high concentrations of the organism. If the milk was accidentally contaminated with infective feces during improper harvest or storage procedures, then it could be possible for high concentrations of Map to be found in it. As such, producers should take steps to avoid fecal contamination of non-saleable milk during the harvest, storage, pasteurisation or feeding processes.

Calf performance and economics when feeding pasteurised non-saleable milk

To date, only two controlled field studies have been published describing health, performance and economics when feeding pasteurised waste milk to dairy calves. In one study, calves fed the pasteurised feeding non-saleable milk experienced fewer sick days, lower mortality rates, lower costs for health expenditures, higher weaning weights and a higher gross margin ($8.13) per calf at weaning, as compared to calves fed raw, non-saleable milk.

A more recent study compared pre-weaning health, growth and economics of feeding a conventional 20:20 milk replacer program versus batch pasteurised non-saleable milk. Average daily gain was significantly greater in calves on the pasteurised non-saleable milk program, (0.47 kg/ day) versus calves fed the conventional milk replacer program (0.35 kg/ day). Also, significantly fewer calves were treated or died on the pasteurised milk program (treatment rate = 12.1 per cent; mortality rate = 2.3 per cent) as compared to calves fed the milk replacer program (treatment rate = 32.1 per cent; mortality rate = 21.0 per cent). Researchers believed that improved nutrient intake is one probable explanation for the improved rates of gain and improved health observed in the group of calves fed the pasteurised milk program.

Considerations for successful use of on-farm pasteurisation systems

In order for the feeding of pasteurised non-saleable milk to be successful, producers must be committed to properly managing and monitoring a pasteurised, non-saleable milk feeding programme.

Installation requirements

1. Cost. Purchase and installation costs, plus estimated variable costs.
   
   
2. Installation support from manufacturer or distributor.
   
   
3. Hot water. Is a water heater self-contained within the unit, or is a separate hot water heater required? If the latter, is there enough hot water with the existing tank to run the pasteuriser, wash the milking system and meet other demands, or is a separate designated hot water heater required?
   
   
4. Location to house equipment. Note: the PMO will not allow non-saleable milk in the milk house. As such, pasteurisation equipment must be housed in a separate location.
   
   
5. Water supply, drainage and electrical requirements.

Considerations for day-day use

1. Maintenance and Service. Is the equipment reliable? How quickly can service be provided? Is a regular maintenance program provided?
   
   
2. Pasteurisation procedures. The manufacturer or distributor should provide effective protocols for pasteurising milk. Farm staff using the equipment need to be trained to use these protocols and should adhere to them.
   
   
3. Strategy for inconsistent supply of non-saleable milk. Depending on the number of fresh and treated cows, the amount of non-salable milk can fluctuate from day-to-day or week-to-week. As such, all farms should have a plan or strategy in the event that an adequate volume of non-salable milk is not available. One option may be to feed pasteurised non-saleable milk to the younger calves, who presumably would benefit most from improved nutrient intake, and then feed older calves a commercial milk replacer feeding program until they are weaned.
   
   
4. Handling and storage of raw milk. Producers need to be aware that pasteurisation does not equal sterilisation. Raw milk must be handled in such a way, prior to pasteurisation, as to minimise bacterial contamination, proliferation and spoilage during the harvest, transport or storage processes.
   
   
5. Handling of pasteurised milk. Any bacteria surviving the pasteurisation process will begin to replicate again in the warm medium if the cooling process is delayed. This can occur if the milk is allowed to cool slowly for several hours at ambient temperature, or if milk is left to sit at warm ambient temperatures for more than a couple hours before being fed. Producers should try to feed the product soon after pasteurisation is complete.
   
   
6. Monitoring pasteuriser function. Reasons for the failure of pasteurisation equipment to reach the target time and temperature can include improper equipment settings or calibration, equipment malfunction, lack of enough hot water, or human error, for example,turning off the equipment early in order to finish chores. Equipment must be equipped with a temperature sensor and display by which producers can periodically check and monitor times and temperatures on a daily basis. Times and temperatures should be monitored daily.
   
   
7. Cleaning the Pasteurisation System. With poor cleaning procedures, it is likely that fat, protein and inorganic films can build up in pasteurisation systems, interfering with transfer of heat to the milk and serving as a source to further inoculate milk with bacteria. Producers should clean this equipment as diligently as they would their own milking system, using procedures similar to common milking system sanitisation procedures. This includes sanitation not only of the pasteurisation equipment itself, but also of all collection, storage, transfer or feeding equipment that the milk comes into contact with, both before and after pasteurisation.

Heat-treating colostrum

First-milking colostrum is an important source of nutrients and of passively absorbed maternal antibodies, critical to protect the newborn calf against infectious disease in the first weeks and months of life. However, colostrum can also represent one of the earliest potential exposures of dairy calves to infectious agents. Bacterial contamination of colostrum is a concern because pathogenic bacteria can act directly to cause diseases such as scours or septicemia. Bacteria in colostrum may also interfere with passive absorption of colostral antibodies into the circulation, reducing passive transfer of immunity in the calf.

There has recently been increasing interest in feeding pasteurised colostrum to reduce transmission of infectious pathogens to calves; however, early research on pasteurising colostrum,using the conventional methods and temperatures to pasteurise milk, yielded less than acceptable results. Pasteurisation resulted in mild to severe thickening or congealing of the colostrum, a reduction of up to 32 per cent of immunoglobulin G (IgG) concentration in the colostrum, and lower serum IgG concentrations in calves that were fed pasteurised colostrum.

The preliminary results from this study suggest that commercial farms can feed calves colostrum that has been heat-treated using a low-temperature, long-time approach of 140°F for 60 minutes to reduce pathogen exposure while maintaining, or even improving, passive transfer of colostral antibodies. Producers should understand that a great deal more research needs to be completed before this practice can be widely recommended to the industry.

Conclusion

Feeding non-saleable milk represents one way to gain important economic and nutritional efficiencies for calf growers but can be a major risk factor for introducing infectious diseases to calves. The recent introduction of on-farm commercial pasteurisers is one method for reducing this risk. This technology has been adopted and used successfully on many farms. Early studies have shown significant health, performance and economic advantages to feeding pasteurised, non-saleable milk as compared to raw, non-saleable milk or a conventional milk replacer feeding program. However, in order to be successful, producers must pay careful attention to the pasteurised milk feeding program. This includes careful handling of pre- and post-pasteurised milk to prevent bacterial contamination or proliferation, monitoring of pasteuriser function, and routine cleaning and sanitation of pasteurisation equipment, as well as milk collection, storage, transfer, and feeding equipment.

September 2009