The importance of supplying the correct nutrients in winter

As forage matures, its quality, and especially protein content starts to decline. To sustain healthy animal production one needs to supplement the veld with the nutrients the veld can no longer provide.

The importance of lick supplementation in the winter cannot be stressed enough.  The supplements provided during this winter will be reflected in conception- calving- and weaning percentages in the following season.  The main purpose of winter supplementation should be to optimise the utilisation of available grazing by providing the correct nutrients in times when the natural veld no longer can.  By doing this weight loss of breeding cows will be kept to a minimum.  It is important that cows calve in a relatively good condition in order to maximise the likelihood of conception in the next breeding season.

For animal production purposes, winter can be divided into two periods, namely early and late winter.  During early winter when grass starts to mature, protein is the first limiting nutrient, although enough forage is available.  Late winter is normally characterised by poor quality forage, which may also be in short supply and needs to be taken into consideration when supplementation is done.

Early winter

The predominant energy source available to grazing animals during the winter months is low quality veld grass.  Grass quality is considered low when the crude protein content drops below about 6% (The protein content of normal winter veld grass is around 3 %).

As grass matures, the fibre content increases, while the protein content decreases. At the same time forage intake and subsequently total energy intake declines, since the fibrous fractions are less palatable and digestible.

As most of the breeding cows will be pregnant in early winter, the natural veld can no longer provide in their nutritional needs and supplementing the veld with a protein lick becomes a necessity.

Protein supplementation to grazing animals is one of the most expensive components of a lick supplement and farmers often minimise the inclusion level to save costs.  Rumen microbes have a basic requirement for protein (nitrogen) which will allow them to effectively digest ingested forage.  The supplementation of the correct amount of protein is therefore essential in order to obtain maximum forage intake, digestion and subsequently meeting the energy requirements of animals.  Due to the ruminant’s ability to convert urea (a non-protein-nitrogen source) into high quality microbial protein, most of the natural protein in winter protein licks can be supplemented with urea. The high nitrogen content (in principle protein) of urea results in a highly economical protein source for ruminants. Urea will provide the animal with the necessary protein without the high cost of the conventional proteins such as oilcake meals (See Table 1 for early winter licks).  The supplementation of sulphur together with urea is important for the formation of sulphur containing amino acids in the rumen.  As a rule of thumb, add 2.5 kg of sulphur for every 50 kg of Urea.  An easily fermentable energy source such as Kalori 3000, molasses or molasses meal is necessary for optimal urea utilisation.

Late winter

As winter progresses, available forage on the veld declines.  Not only is the quality of the forage at its lowest, enough forage to supply the animal with energy is usually in short supply.  At this stage, protein supplementation alone may not give the desired improvement in animal performance.  During late winter, early spring, cows are often late pregnant or lactating and young animals are growing.  The energy requirements of these animals may exceed the energy that can be provided by the grass, even though enough protein is provided through licks.  Moving animals to better quality pastures or providing a production lick to supplement energy, protein and minerals is needed for sustainable animal production (See Table 1 for late winter licks).

Balance

As with everything in nature, the nutrients supplied to an animal must always be in balance for optimal production.  During summer, pastures can supply enough protein and energy to the animal, but South African pastures lack phosphorus.  To balance the nutrient supply, phosphorus needs to be supplemented.  The same applies for early winter when pastures have the potential to supply energy, but lack protein and minerals.  To balance the nutrients, protein and minerals (phosphorus) need to be supplemented.  During late winter, when the grass cannot supply enough of either of the nutrients, all three nutrients must be supplemented.

The following licks can be mixed to provide the animal with the correct nutrients during the different winter periods, providing that enough roughage is available.

Table 1             Early and late winter supplementation for cattle and sheep

*    Lick 1 can be used during early winter for cattle.

**   Lick 2 can be used during early winter for cattle and sheep.

**   Lick 3 can be used during late winter to provide the animal with protein, energy and phosphorus

Lick 1-3   Maize can be replaced with Hominy Chop or Molasses meal (1:1).  Remember that Molasses Meal is palatable and intakes must be regulated.

Phosphorus supplementation during winter

The importance of phosphorus (P) in the nutrition of cattle can not be over emphasised.  Phosphorus is present in all cells of the body and is essential for most of the metabolic processes in the animal.  These processes include the conversion of feed to energy and the build-up of body tissues.

Although phosphorus is primarily a wet-season supplement, it still needs to be supplemented during winter.  Scientific and field trials done, showed that animals receiving licks containing P during winter, had a higher milk yield in the following wet season (where both groups received P supplementation), compared to a control group that received a lick containing no P during the winter.  The reason for this is either the cows stored P in body reserves (mainly bones) and drew on it when feed quality improved, or there was less drain of P from the bones during the dry season because of the supplement.  Supplementing P in winter, therefore, help cows in the transition period to the wet season when there may be problems in servicing supplements and obtaining acceptable intakes of a wet-season supplement.

Summary

The supplementation of winter veld must never be neglected.  Lick supplementation is costly and it is therefore important to now which nutrient is deficient during the different winter periods, in order to supplement the correct nutrient at the appropriate time.  The financial inputs made through supplementation during the dry season will be well rewarded in terms of higher milk production, calving percentage and conception rates in the following green season.