The intestine of a calf is still developing throughout the first few weeks of life, and production of digestive enzymes are increasing with age. The calf doesn’t obtain all the nutrients available in liquid feeds for a period after birth.
Calf & Youngstock
Whether it is beef or dairy it is important to grow calves efficiently to meet slaughter weights sooner. Standard target weights of pre weaning weights are greater than >0.7kg/day and post weaning DLWG of >0.8kg/day - >1.0kg/day for dairy or beef respectively.
There is no such thing as a silver bullet balancing for Amino Acids in calf milk replacer.
Amino acids are certainly the buzz word in ruminant nutrition, and rightly so. Nevertheless, will AA supplementation change the world of calf milk replacers too?
There are two overarching themes in research and ongoing farm trials:
- We are scratching the surface.
- A silver bullet does not exist.
The British dairy industry prides itself on being a pioneer in dairy cattle welfare; it is a top priority for the sector.
However, the fate of dairy bull calves is not a secret; it is a key focus area for the industry. While the rearing of bull calves for the beef market is high, and several industry initiatives continue to champion improvements in calf health, welfare and survival, there is still room for improvement. The industry has committed to making further progress in this area with the development of the GB Calf Strategy. The core objective of the strategy is to find practical solutions to reduce the number of calves that are routinely euthanised on farms. You can read more about the GB Calf Strategy on the AHDB website.
Energy demand for any dairy animal depends on their specific requirement for; maintenance, reproduction, milk production and body reserves. Whilst our mature cows are pregnant their energy demand is focussed on maintenance and foetal growth.
As a heifer progresses through the pregnancy we must consider she is still undergoing her own continued development including her own maintenance, growth, mammary tissue growth/development, and then in the last trimester of pregnancy, the foetus goes through a huge growth phase and, therefore, energy demand increases significantly and quickly (from day 191). Some farms look to balance the diet for a heifer at 141 days (to take an average of her requirement throughout) but this is not sufficient for the third trimester as the demand for energy and protein is far greater.
The expected calf birth weight and day of gestation can be used to calculate a heifer’s requirement for metabolisable energy and protein. The risk of undersupplying energy is that the dam will prioritise the energy she has got available to the development of her calf resulting in her growth slowing or stopping altogether. This may result in difficult calving as she has not grown to the expected size.
It is important to know intakes at stages through pregnancy; pre-calving we can assume consumption to be 1.75% of body weight but this depends on the palatability of the ration put in front of them. Because heifers begin to eat lesser quantities they need the diet to be more energy-dense.
Heifers should be entering the milking parlour at 82% - 90% mature bodyweight post-calving to optimise first lactation yield (Van Amburgh et al., 1998). We can work on a relatively accurate estimation that heifers will produce the same percentage of milk of a mature cow as to what she is as a percentage of her mature weight i.e if she only enters the milking herd at 70% of mature weight, we can only expect 70% of mature cow’s milk yield from her as she is still needing a proportion of energy intake for own growth.
As with all animals, clean, fresh and plentiful water access should be available at all times and this will encourage dry matter intakes.
Feeding Seperate Diets
On some farm set-ups, it can be difficult to run two separate groups and feed two separate diets. Often it is seen as a balancing act and diets are formulated to be in the middle of mature cow and heifer requirements. The problem with this is that the diet can be of higher energy than what dry cows need and lower energy than what heifers require and, due to physical capacity, the dry cows are able to consume more. So, heifers are fed restricted protein and energy.
If we don’t account for this higher energy demand for the heifers and their need for a higher energy-dense diet, then we risk them mobilising fat from their own reserves and have high levels of NEFA’s prior to calving. Reduced dry matter intake pre-calving can lead to the same post-calving and predispose the animal to ketosis and fatty liver syndrome.
Feeding highly digestible fibre forages to help meet demand.
It is important to consider heifers are producing colostrum in the last six weeks of pregnancy and, if they are deficient in energy and protein, we cannot expect them to produce high-quality colostrum.
The management of calves is one of the industry’s main sources of criticism; both the treatment of dairy bull calves and the separation of cows and calves have been attacked by dairy sceptics. My 2021 Nuffield project “Can the UK improve the ethics of its dairy calf management whilst retaining profitability?” will try to find workable solutions to these issues
With warm weather approaching, the risk of heat stress in calves increases. Everyone is well aware that heat stress in adult cattle reduces performance, increases stress and results in increased incidence of disease, and calves are no different. Calves have an upper critical limit of 25°C, however they will start to feel the effects of heat stress at 21°C.
Pretty much all farmers have heard of calf jackets, they have gained popularity in recent years as a way to control cold stress but do we know how to use them correctly?
Let’s take humans for example, when the temperature drops, we put more layers on, right? And vice versa when the temperature rises; should we consider this for our calves too? First, let’s understand why we use the calf jackets.
Over a decade ago, research at the Royal Veterinary College, London found that calving heifers at 23 to 25 months of age was optimum in terms of their subsequent fertility, milk yield and survivability through to the third calving (1). The recommendation to calve heifers close to 24 months of age is not new. But the message is just as valuable today – in fact, new data from recent studies have further reaffirmed this important practical advice.
We expect our calves to be able to cope and adapt to shifts in their nutrition throughout the pre-weaning phase, the first being from colostrum to whole milk/milk replacer and the last being from liquid to solid feed. Weaning is without doubt one of the biggest transformations the Gastrointestinal tract (GIT) will undergo and therefore understanding when and how we can best manage this juncture to avoid growth checks and impaired GIT health is important to the productivity of our calves.