by Christine Brøkner PhD, Technical Manager, Hamlet Protein, Denmark

 

The immaturity of the gastrointestinal system is the reason why a calf's transition to ruminant can be troublesome.

From birth, calves have an esophageal groove, a muscular structure that shunts milk directly into the abomasum, by-passing the rumen. This means that new-born calves are functional mono-gastrics in terms of their ability to break down feed and absorb nutrients.

Like other young animals the secretion of various digestive enzymes is also limited, emphasising the need for highly digestible ingredients at this early stage. The luminal surface area of the rumen has a smooth appearance with no papillae development and therefore, also no absorption capacity.

This is not a problem in the first few weeks after birth as nutrients are absorbed in the small intestine and the nutritional requirements are met entirely by colostrum and milk products.

Pre-starter feed should be introduced in due time. The purpose of this is two-fold: to initiate the development of the rumen and to motivate calves to increase their solid feed intake in preparation for weaning.

During weaning where milk feeding is reduced, rumen and ruminal functions are developing while pre-starter feed intake increases and becomes the primary supply of energy and nutrients. This naturally emphasises the importance of the availability of nutrients in the pre-starter feed around weaning. The purpose is to secure same high absorption of energy and nutrients as were calves only fed milk.

If nutrients are not available or cannot be absorbed, the full growth potential of calves cannot be reached and a dip in growth post weaning is a reality. This is the dilemma of weaning - sufficient supply of energy and nutrients while weaning the calves off milk and developing ruminal functions. So, what can be done to overcome this digestive challenge at weaning? The answer lies in the choice of the protein source.

Protein ingredient selection

Raw unprocessed soy naturally contains factors that primarily act as biopesticides, protecting the beans against molds, bacteria and from being overeaten by wild animals.

All factors, that interfere with the utilisation of dietary nutrients when used as feed and therefore should be avoided for maximum utilization in calves.

These factors are collectively defined as anti-nutritional factors (ANF's) and are harmful to gut physiology and morphology (see Figure 1) and subsequently depress animal growth and increase the incidence of scouring. In pre-weaned calves the damage to intestinal surface area impairs nutrient utilization.

 

ANFs can be grouped in many ways according to their effect on nutritive values of feed ingredients and biological responses in animals. In broad terms the most harmful ANFs are those that depress protein digestion and absorption (trypsin and chymotrypsin inhibitors, lectins, polyphenolic compounds and saponins), digestion and utilisation of minerals (that is, phytic acid), flatulence factors and osmotic diarrhea triggers (that is, stachyose, raffinose and verbascose) and antigenic proteins (that is, beta-conglycinin and glycinin) that activate the immune system unnecessarily, causing oxidative stress responses which result in damage to intestinal tissue locally in the gut.

Processing of soy can reduce the adverse effects caused by ANFs and heat treatment is an often-used method and includes toasting, extrusion and steaming.

In fact, heating in excess affectively inactivates ANFs by denaturing protein structures.

However, excess heating, besides inactivating ANFs, simultaneously results in loss of nutritional value, including amino acid digestibility by the formation of irreversible complex bindings between reduced sugars and amino acids, also known as the Maillard reaction.

Heating at 110°C for up to 30 minutes does not impact amino acid digestibility, however 150°C for three minutes and more significantly reduces digestibility.

An efficient methodology to be used in combination with heat is state-of-the art enzymatic treatment developed by Hamlet Protein to fully inactivate soy ANFs. Use of specific enzymes avoid the need for high and extended use of heat.

Replacement of whey

Dairy protein is the natural first choice of proteins when feeding calves due to the nearly 100 percent digestibility of amino acids.

However, dairy protein is also the most expensive protein source. The need for a cost competitive alternative to dairy proteins is needed especially for veal production but producers of rearing calves and heifer calves also benefit from a cost competitive alternative.

Soy protein products are the preferred vegetable protein choice in calf feeding as an alternative to whey protein due to the favorable amino acid profile and high protein concentration.

However, high standards for example, nutritional values and product functionality, are expected of the soy protein source before it can be considered as an alternative to whey protein. The enzyme treated soy product HP100 has proven an excellent alternative in replacing 50 percent of whey in calf milk replacers (CMR). The calves were feed CMR containing HP100 continuously for four weeks post calving without compromising growth while significantly improving fecal consistency. Fecal is firmer in milk-fed calves when HP100 is included in the milk replacer.

The physical functionality of soy protein should be critically evaluated prior to mixing into a CMR product. Products replacing whey protein need to stay in suspension and avoid sedimentation while calves are drinking. 

Protein of choice

By extension, these qualitative descriptions of a clean protein ingredient achieved by an enzymatic treatment are reflected in higher growth performance, more uniform calf herd and less scouring. At 10 weeks of age, when calves are only fed soy protein, the hindquarters were more clean and fecal condition was firmer when HP300 was included in the pre-starter feed.

Calf hindquarter and fecal score were cleaner and firmer when fed enzyme treated soy protein.

A commercial Dutch rosé calf producer compared the use of enzyme treated soy (HP300) to soybean meal (SBM) in pre-starter to more than 100 calves.

The calves were split in two treatment groups. Within each of the two treatments were sub-groups, calves above or below 54kg. By the end of the trial, calves fed HP300 grew better and the small calves caught up with the bigger calves at 10 weeks of age.

This trend was also reflected in live weight at slaughter and carcass weight. SBM fed calves were two kg lighter than HP300 fed calves (carcass weight).

In conclusion, the growth data from feeding HP300 in the Dutch rosé calf trial and the replacement of whey protein by the more cost-efficient HP100 alternative brings together the essence of feeding calves. Clean and highly bioavailable amino acids from enzyme treated soy proteins are needed to avoid scouring and to get the best growth performance and most uniform calf herd.

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