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- The goal of winter nutrition for bulls and cows should be to prepare breeding animals for the upcoming breeding season.
- Natural grazing loses much of its nutritional value during winter.
- A range of commercially available energy licks can help balance animals’ nutritional requirements.
- As the mating season approaches, cows should ideally have a condition score of between 3 and 3,5.
- Young bulls require adequate protein and energy to support development, maintain condition, and produce sufficient body heat during colder periods.
The goal of winter nutrition for bulls and cows should be to prepare breeding animals for the upcoming breeding season. This is the critical time when the foundation is laid for optimal reproduction and production – factors that will ultimately determine the success of the next calving season.
Natural grazing loses much of its nutritional value during winter. Where animals run on crop residues, available forage becomes increasingly scarce. Without complementary feed, animals lose body condition, which can potentially cost producers up to half of the calf crop expected in the next season.
According to Johan Mouton, manager of research and product development at Molatek, heavy frost will coincide with a sharp decline in the nutritional value of grasses. “Just like humans, plants need nutrients to survive,” he explains. “From February onwards, grass plants begin storing some of their nutrients in their root systems in preparation for winter survival after the leaves have withered due to frost.”
Grass plants transfer easily digestible nutrients to their root systems to support survival and regrowth in the following season. The leaves are mostly fibrous. As the stored root nutrients are inaccessible to grazing animals, they must be given complementary feed.
Nutritional requirements
Livestock feed primarily consists of two essential components: protein and energy. Protein is essential for muscle development and maintenance of the animal’s organs, with fish meal being a typical protein source. Energy, on the other hand, helps animals gain weight in preparation for slaughter; maize is widely recognised as an excellent energy source.
While grass does contain enough energy to sustain the animals, it doesn’t offer enough protein. Fortunately, a range of commercially available energy licks can help balance animals’ nutritional requirements.
In South Africa, the most common breeding season runs from early December to the end of February. However, depending on climate and rainfall patterns, producers in some regions may shift the season forward or backward by a month.
The condition of bulls and cows significantly influences the number of calves born in the following calving season. For example, if a cow conceives on 1 January, she will likely calve around 12 October, approximately 284 days later. By the time the calf is weaned at six to seven months of age, the cow will already be six to seven months pregnant again. At that point, her body is supporting both a growing foetus and a nursing calf, which places a considerable demand on her energy reserves.
The killer months
To survive the winter and maintain body condition, cows must build up reserves during the previous summer. The so-called killer months, spanning August to October, are especially critical. This is the period when breeding animals require focussed care to improve their chances of successful reconception.
Natural grazing deteriorates during winter, becoming dry, unpalatable, and low in nutritional value, causing animals to ingest less of it. Although the first green growth may appear around three weeks after the first good rainfall, producers often say: it doesn’t rain grass.
The initial regrowth contains high moisture but low dry matter. As a result, animals often lose weight while searching high and low for suitable forage. Although the mating season may still be months away, proper nutritional management is now essential to overcome these seasonal challenges. In this regard, the guidance of a qualified animal nutritionist can be extremely valuable.
Fit and fertile
As the mating season approaches, cows should ideally have a condition score of between 3 and 3,5. Cows with a condition score of 2 or lower may experience conception rates as low as 50%. However, it is not only the cows that require special attention – bulls also demand careful management, particularly through the winter months. It is essential that cattle producers, especially stud breeders, ensure that their bulls maintain good condition and are fit and fertile once the breeding season kicks off.
The nutritional needs of bulls vary depending on their physiological stage. Young bulls that are still in their growth phase, require adequate protein and energy to support development, maintain condition, and produce sufficient body heat during colder periods. Producers must assess and provide the appropriate amount of feed to support these demands.
Mature bulls, on the other hand, should be closely monitored to prevent loss of condition leading up to breeding. They need adequate fat reserves, but should not become obese, as excess body fat can negatively impact their fertility.
Key nutritional factors to consider:
- Energy from fat and carbohydrates in the form of oilcake (fat and protein) as well as grains such as maize (carbohydrates) can be utilised. Be sure to increase the ration’s energy.
- Protein sources and complimentary feed such as soya or canola oilcake. Adequate protein is essential in winter to support rumen microbial activity.
- Supplement essential minerals such as copper, manganese and zinc, as they play a critical role in fertility and reproductive performance.
- Winter pastures are often vitamin A deficient, which can lead to health and reproductive issues. Inadequate vitamin A intake in bulls may impair spermatogenesis and reduce fertility, so supplementation is crucial.
- Provide bulls with constant access to fresh, clean water at a drinkable temperature. Insufficient water intake can lead to reduced feed consumption.
- Bulls should receive enough roughage – approximately 2,7% of bodyweight (for bulls weighing up to 230kg) and 2,5% of bodyweight for mature bulls.
- The ration should contain around 15% protein on a dry matter (DM) basis.
- Do not exceed 10,2 MJ of metabolisable energy or 68% total digestible nutrients on a DM basis.
- Maintain a calcium to phosphorus ratio of 1:1,5 to 1:2 (0,8% calcium and 0,4% phosphorus).
Condition score
Producers should aim to maintain or improve the condition score of their bulls during the winter months. Condition score – ranging from 1 (emaciated) to 5 (fat) – is a useful tool. An ideal target for bulls is between 3 and 3,5. Overfeeding bulls can negatively impact fertility, reducing semen quality and production. Decreased libido in overfat bulls means they are less effective breeders, which can reduce conception rates.
To meet differing nutritional requirements, it is advisable to separate bulls by age and condition during winter. Older and younger bulls have different feed needs and should be given tailored rations. Additionally, separating bulls based on condition score allows producers to immediately spot an improvement in the condition of lean bulls.
According to Mouton, an animal’s nutritional needs vary depending on its stage in the production cycle. In cows, these needs begin to rise about two months before calving. Energy requirements at this stage increase by roughly 25%, while protein needs almost double. It is especially critical to meet these increased demands, as a cow’s condition at calving directly affects her ability to reconceive during the next breeding season.
The nutritional demands of a high-producing cow are approximately twice that of a dry cow. To ensure reconception and an economically viable intercalving period, a cow should have a condition score of 3 to 3,5 at calving.
Fodder flow planning
“Nutritional management decisions must be made timeously and implemented as early as the summer months,” Mouton emphasises. “The key to success lies in effective fodder flow planning to ensure sufficient roughage availability during the late winter period.”
He believes that aligning fodder flow planning with natural resources can enhance animal performance and reduce supplement costs. While supplements play a key role, they are ineffective without adequate roughage and should never be seen as a replacement for it. – Andries Gouws, Plaas Media
For more information, send an email to Johan Mouton at Johan.Mouton@rclfoods.com or call 083 278 7746.
