A trial has demonstrated the calf health and performance benefits that Irish block calving dairy farms could gain by feeding a skim milk-based replacer, offsetting the higher cost of this high-quality product.

The trial in New Zealand studied how calves under two weeks’ old and exposed to infection reacted when they were fed different calf milk replacers, including skim, whey and whey and plant protein formulations.

Antibiotic use and mortality in the group fed skim milk was 75% lower than in the groups offered the other replacers.

The researchers concluded that the New Zealand herd size and block calving create greater challenges to cow health and this is why skim-based milk replacers are preferred in New Zealand.

‘Money well spent’

Tom Warren, of Bonanza Calf Nutrition, says this has resonance for Irish dairy farms.

“With the average herd size in Ireland now at almost 80 cows and with nearly 20% above 100 cows, there can be 40-50 calves on farms in the months of February and/or March,’’ Warren pointed out.

In contrast in Europe, all year-round calving means there are on average only four to five heifer calves on many farms at any one time, he added.

Warren explained: “A young calf is naturally hardwired to hide in long grass to avoid predators and emerges infrequently to suck from its mother.

“Cow’s milk contains casein protein which curdles in the stomach when it reacts with the enzyme renin. This curd traps most of the milk fat and vitamins A, D, E and K and is slowly released into the small intestine throughout the day.

“This strategy of providing baby animals with a slow release high energy feed is part of many animals life-cycles, from red deer to hares.

Using a skim-based milk for young calves will cost €2-3 a calf extra, but with reduced disease and work associated with treating sick calves it is money well spent.

Feeding skim milk twice a day (TAD) or once a day (OAD) to young calves is a safer option and choosing a product with a fixed formula from year to year will give more piece of mind.

For OAD feeding, a skim-based calf milk replacer is key as it will provide a slow release of nutrients throughout the day – in contrast, whey leaves the stomach within an hour.

By feeding at the same strength as colostrum, calves can consume 6L of milk solids in a single feed of 3-3.5L of liquid, reducing the requirement for energy to excrete 3L of liquid.

Far from being unnatural, calves on TAD feeding are more stressed, especially from noon onwards as they feel underfed in the morning, said Warren.

Calves fed a skim-based milk OAD consume more dry feed and this aids rumen development.

‘Putting the cart before the horse’

In 2013, trial work by INRA (the French National Institute for Agricultural Research) demonstrated that rumen development almost doubled when calves were fed OAD.

This was not because calves received less milk, as both groups were fed equally, but because calves ate more ration throughout the day; in comparison, the group fed TAD were too stressed anticipating their milk feed to eat the ration.

If feeding cow’s milk OAD, feeding a skim-based replacer won’t dilute the milk curd.

“By adding 50-100g of a skim-based milk replacer to a litre of cow’s milk, 3-4L of cow’s milk can supply nearly 6L of milk in one feed, once again reducing the liquid in the diet and also reducing the fat content of the diet,’’ said Warren.

This will encourage dry feed intake and reduce weaning age by about 10 days, if weaning is based on concentrate intake and body weight.

“This last point is often overlooked in calf rearing,’’ Warren suggested. “A lot of milk feeding programmes claim extra performance in later life, but that is putting the cart before the horse.

Ruminants can only produce milk or meat from their intake of feed. The rumen’s development is central to a calf’s performance while at grass, and to a heifer or cow’s milk production.

“If she is going to produce extra milk she needs to consume the extra feed required to produce this milk or her health and fertility will suffer.

“This is why feeding a skim-based milk replacer to keep calves healthy and encouraging dry feed intake and rumen development is the only way to guarantee performance and longevity.’’

Maximising dry feed intake in calves relies on the provision of fresh clean water, regardless of milk intake, as the water fraction in milk cannot enter the rumen and the rumen bugs need water to ferment the dry feed materials.

“Failing to provide water will reduce feed intake and performance before and after weaning by 40%,’’ said Warren.

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