Nutrients can be categorized in 5 areas:
1.Water (not an actual nutrient)
2.Dry matter (containing the nutrients, expressed as DM)
3.Energy (Nett Energy, expressed as FUM)
4.Protein (we will use digestible crude protein, expressed as DCP)
5.Minerals and vitamins
Water:
Although water is not considered as a real nutrient, it plays a vital role in the functioning of the body, milk production, and the total intake of food (DMI). The daily requirement of water is influenced by a number of factors, such as:
-type of food offered (DM content)
-physiological state of animal (lactating, pregnant)
-mineral content of ration
-environment: temperature, humidity, and ventilation/shade
-temperature of drinking water
-DMI
A shortage, or uneven supply of drinking water, has a direct consequence on the DMI. In order to maximize DMI, ad lib supply of fresh water (cool in warm seasons/climates) should be available to the animal for 24 hours per day. For maintenance, a dairy cow requires between 30-100 litres per day. For milk production, a cow requires 1-2 litres of water extra for every one litre milk production. The water requirement is estimated as 3½-4 kg per kg DMI (in temperate climates till 21 C) plus 1-2 litres water for every kg milk produced.
More water may be required in warmer climates/seasons, also depending on the cattle keeping system (grazing, 0-grazing, housing, shade, humidity, ventilation). Peak demand (40% of total) usually occurs between 15.00 and 21.00 hours. This aspect has to be considered for the size of the trough (holding capacity, drinking space), pipe-size etc. as to supply sufficient water during the peak-demand period.
Water Allowances for Cattle
Kg water per kg DMI Environmental temperature (C) Class of animal
< 16 16-20 > 20
Calves up to 6 weeks 7 8 9
Cattle (growing/adult, 5.4 6.1 7
pregnant/non-pregnant)
Daily water intake (kg/head)
Lactating cows; 600 kg; milk yield (kg/day)
10 81 92 105
20 92 104 119
30 103 116 133
40 113 128 147
Dry Matter Intake (DMI)
DMI is most important in animal production, as the DM contains the nutrients. A high
production will lead to an increased appetite and vice versa. The DM of a feedstuff has a slight influence on total DMI. Moderate dry (30-50% DM) and tasty feedstuffs allow highest roughage intake. Dairy ration formulation requires an estimation of DMI. The following 3 formulas are used to predict DMI of lactating cows fed on mixed diets with roughages and concentrates.
Formula 1 is considered for cows in mid and late lactation. The first 6-10 weeks lactation, DMI values are to be reduced by 2-3 kg DMI/day (energy-gap).
Formula 1: DMI = 0.025 W + 0.1 Y * 1 kg DM
DMI = dry matter intake (kg/day)