Reducing milk or milk replacer fed to calves leads to higher morbidity and mortality rates

Like adult cattle, young calves partition the nutrients they consume.

Maintenance always takes priority over other demands, so initially, nutrients are used for locomotion, heart, lung, brain and gut function, etcetera.

Included in this is the function of the immune system.

Calves receiving inadequate levels of milk or milk replacer will not have sufficient nutrients for the immune system to perform even the most basic of functions.

Only when the maintenance requirements have been met will excess nutrients be partitioned into growth.

The development of the immune system only happens at the same rate as body growth.

A calf that is losing weight or growing at only 100-200 grams a day will have no or a slow immune system development.

This will compromise the animal's ability to fight off disease.

It is common to see underfed dairy calves suffering from scours in the first few weeks of life and pneumonia in the second and third months of life; although obviously there is an overlap of the ages at which these diseases occur.

The key message here is that adequate feeding levels, coupled with a good colostrum history, are a major driver of the ability of calves to fight immune challenges.

Early life growth rates are influenced by health status; calves that are sick or stressed will not be growing as fast as they should; nor will their immune systems be developing.

The early life period is when feed conversion efficiency (FCE), milk production and reproductive capacity are set for life.

In dairy calves grown for meat production, this has slightly less impact, but for replacement heifers, getting this critical phase wrong is costly.

Weighing calves regularly is the most reliable indicator of an appropriate feeding schedule.

Calves should be growing at a steady rate from birth to first calving.

It is important calves do not lose weight in the few days immediately after birth.

If this weight loss does happen, the calves' immune system will be compromised and illness will result.

Newborn calves fed minimal amounts (2-4 litres/day) will lose weight and body condition in the first week of life.

If established targets for pre-weaning or 12 week weights are being used to evaluate the success of the feeding program, calf weights are only relevant if body condition scores are acceptable.

Calves fed low levels of milk to reduce costs or to wean early will consume large quantities of hay or straw, in addition to concentrates, in an effort to satisfy their hunger.

This results in a low body condition score and a big "hay belly".

The weight of the excessive volume of gut contents may bring these calves up over the target weight but they will have a low BCS and will not be thriving.

Therefore, it is important that body condition scoring (BCS) is taken into consideration when weighing calves.

To correctly condition score calves, it is important to visually assess condition but also to do a hands-on assessment of the calves' rib cage, back and spine region and hip/pins area.

Underfed calves will have a "poddy" tummy, their heads will often look big in proportion to their body, necks will look weak, and coats will be harsh and fluffy.

Calves, especially undernourished ones, can have fluffy coats, which can hide a low BCS; only a manual assessment will give an accurate assessment of condition.

The concept of limited feeding of young calves has been proven beyond doubt to be invalid, with limit-fed calves having poorer health and welfare outcomes than fully fed calves.

It has also been proven beyond doubt that calves fed high (biologically normal) volumes of milk:

. have less illness;

. have higher weight gains;

. have better lifetime feed conversion rates;

. have higher lifetime milk production; and

. exhibit more natural behaviours.

Heifers entering the herd after being underfed as baby calves are more likely to:

. have difficulty calving;

. compete poorly for feed;

. have lower feed intakes;

. produce less milk, partly because their intake is less and partly because they are partitioning energy into growth instead of milk;

. will be incapable of reaching their genetic potential for milk production when they enter the herd;

. have lower fertility and be less likely to get back in calf than well grown heifers; and

. have a higher early life cull rate than well grown heifers.

Before reducing milk feeding levels, particularly for replacement heifers, it is important to take into consideration the above facts.

The costs associated with a disease outbreak can easily outweigh the money saved by feeding less milk.

Feeding a bit extra milk or milk replacer may cost a little more in the short term but if it reduces the morbidity and mortality rates in pre-weaned calves and lowers the cull rate prior to the second lactation from, say, 30 per cent to 10pc, the small extra expense will be easily recouped.

It also delivers an animal welfare outcome in line with modern consumer expectations.

*Jeanette Fisher is principal of Heifermax, phone 0428 867 551, email jfisher@heifermax.com.au, website heifermax.com.au.

This story first appeared in The Australian Dairyfarmer magazine, May-June 2023 issue.

Want to read more stories like this?

Sign up below (select Dairy News) to receive our e-newsletter delivered fresh to your email in-box twice a week.