Farming

Extended colostrum feeding reduces health issues in young calves

Alvaro Garcia

Most colostrum is readily absorbed during the first hours of life, when the intestinal epithelium is still open to the passage of larger molecules (e.g., IgG, IgA, and IgM). Aside from its well-known effects on providing passive immunity through immunoglobulins, colostrum is an excellent source of nutrients with a much higher concentration compared with that of milk.

In addition, colostrum adds to what has been termed ‘metabolic programming’, which begins in-utero and continues after birth. Milk-borne bioactive factors transferred from the mother in early life, play a critical role in programming later life events through cellular signaling mechanisms, immunity, and growth and differentiation of the digestive tract.

This content is locked

Login To Unlock The Content!
Two cute Jersey calves

Which is the upper critical temperature-humidity index for dairy calves?

Alvaro Garcia

Thermostasis is the process by which warm-blooded animals keep their body temperature constant despite changes in environmental temperatures. Heat stress occurs when calves are incapable of dissipating enough heat to maintain their core body temperature below 38.5ºC. This increase in body temperature results from the combination of heat from the environment and that produced internally during nutrient metabolism.

In the northern hemisphere it is quite common for calves to be housed in polypropylene hutches with a small restricted outside area. During warm summer days calves seek the shade supplied by the hutch, however the heat inside of it will be concentrated. The calf then resorts to physiological mechanisms to lower its body temperature.

Under these conditions it is easy to verify an accelerated respiratory rate also accompanied by increases in rectal temperature, ear temperature, heart rate, and salivary cortisol (SC).

Ambient temperature and humidity determine the heat stress threshold

Not only is the absolute ambient temperature important but its combination with humidity in what is known as the temperature-humidity index (THI).

In adult cattle the upper critical value for this index is between 72 and 74, with some authors even considering up to 78 before respiratory rate and rectal temperature increase. In young calves however the optimum THI has not been determined, it is suspected however it should differ from a mature lactating cow since the heat increment resulting from forage fermentation in the rumen is very low, and the metabolic heat associated with milk production is non-existent.

This content is locked

Login To Unlock The Content!

Heat stress affects performance of pre-weaned dairy calves

Alvaro Garcia

It has been well documented that pre-weaned calves raised during summer have reduced gains. The reasons are multifactorial and include pre- and postnatal heat stress, flies, and wet bedding result of rainfall.  Heat stress seems to be the main culprit however, with mechanisms to increase cooling (i.e. respiratory and cutaneous evaporative cooling) triggered when ambient temperatures exceed 20 °C. These mechanisms use energy and result in more energy for maintenance and less energy available for growth.

This content is locked

Login To Unlock The Content!

Effect of colostrum treatment on immunoglobulin absorption

Fernando Diaz

Newborn calves are immunodeficient. Colostrum provides them immunity, but it also can be a potential source of pathogen microorganism such as Mycobacterium avium ssp. paratuberculosis (Johne’s disease), Mycoplasma spp., Escherichia coli, and Salmonella spp. For this reason, heat treating colostrum to reduce or eliminate pathogens is a common practice in the dairy industry. However, heat treatment may affect colostrum immunoglobulin G concentration.

This content is locked

Login To Unlock The Content!
Effects of feeding non-saleable milk containing antibiotics on calf growth

Effects of feeding non-saleable milk containing antibiotics on calf growth

Fernando Díaz

It has become a common practice to feed non-saleable milk to dairy calves. Non-saleable milk accounts for 1–4% of the total milk produced in the farm and this includes milk from antibiotic-treated cows along with colostrum from fresh cows and milk containing high somatic-cell-counts.

Using pasteurized non-saleable milk for calf raising it is economically advantageous. However, it is controversial, especially due to its contamination with antibiotic residues that may increase the risk of antimicrobial resistance on ruminal and intestinal microflora.

This content is locked

Login To Unlock The Content!