Farmer's Weekly (South Africa)
Optimising in-calf cow nutrition before winter
A commercial beef producer’s primary income is derived from animals produced and sold. For this reason, it’s crucial to keep breeding female animals in optimal condition at all times. Mike Rennie, a KwaZulu-Natal beef cattle farmer, spoke to Lloyd Phillip
vigour for his commercial beef enterprise, and maintains the overall herd as Braford-type.
He markets about 500 head a year, most of them oxen that he fattens on-farm. In summer, about 80% of them graze on pasture and are given supplementary concentrate feed, and in winter the remainder are fed in a conventional feedlot.
“I sell animals year-round to ensure a fairly constant income,” he says. “The youngest oxen are finished when they’re between 10 and 12 months old, and the balance, both home-bred and bought-in oxen, are fattened until they’re three years old. These, and any cull female animals and bulls I might have, are sold at monthly auctions via Farmers Livestock Agents [based in Underberg], and to a local abattoir and butchery.”
He explains that Palmiet farm’s beef enterprise utilises about 1 350ha of grazing. The average quantity and quality of this predominantly sourveld is influenced by altitude (from 1 450m to 1 550m above sea level), annual rainfall (780mm), summer daytime temperature (often reaching between 28˚C and 30˚C), and winter night-time temperatures that regularly fall to just below freezing and cause frequent frost.
In years of normal rainfall, the average carrying capacity for sourveld in the Kokstad area is between 2ha/MLU and 2,5ha/MLU.
This can be reduced to below 2ha/MLU if a high-intensity grazing system is utilised.
grazing quality
Rennie says that he achieves a conception rate of at least 90%, largely by planning mating according to his veldbased feeding system. Depending on the time of arrival and the quantity of spring rain, he places the female animals on sourveld grazing from approximately October to July. In August, he moves them to a section of the farm’s
are the most important principles I follow. A farm’s carrying capacity is directly related to rainfall, so it’s important to proactively reduce stocking rate when the rainfall of the previous 12 months declines below the long-term average.”
maximising grazing
Describing himself as a “very cost-conscious” farmer, Rennie utilises Palmiet’s quality grazing to the full. To achieve this, he plans for calving to start at the beginning of September, which is 60 days before the farm’s green date.
This means that he has to put bulls to female animals from around 20 November, as a beef cow’s average gestation is 284 days.
With the start of the mating period almost three weeks after Palmiet farm’s green date, the sourveld is usually growing well at this stage, and the breeding female animals grazing on it are therefore on a rising plane of nutrition during mating, improving their ability to conceive.
The breeding period is
90 days for lactating cows and 60 days for heifers. On average, between 70% and 75% of the breeding females conceive within the first 30 days, and a further 20% conceive during the second 30 days.
In early to mid-spring, when daytime temperatures and sunlight intensity are still fairly mild on Palmiet, sourveld growth is slower than in summer. During this time, Rennie aims to rest each grazing camp for up to 60 days. Where this is not possible for a particular camp, he rests it for 45 days, but ensures that it receives a full 60-day rest the following year. This longer recovery period in
sourveld to generate nutrients via photosynthesis instead of having to tap into root reserves.”
At the peak of Palmiet’s summer rotational grazing programme, a breeding cow herd may spend as little as a single day in a 10ha camp before being moved to the next grazing camp in that cell.
measuring regeneration
Rennie uses a simple, but accurate, method to calculate whether a sourveld grazing camp’s dry matter production has regenerated sufficiently to allow for regrazing.
He begins by placing a homemade, 1m3 grid onto the grass in randomly selected spots within a camp. He then cuts all of the plants within this grid to just above the crown of each plant, gathers it into a sack, and spreads the material on his homestead lawn, allowing the sun to dry it until it is completely wilted. He weighs all of this wilted plant matter and multiplies the result by 10 000 to obtain the dry matter weight in kilograms per hectare for the camp.
good sourveld management means cows recover well after calving
“I do this at various times throughout the year. Over the years of using this system, I’ve learned to make fairly accurate visual estimates of the veld quality and quantity of each camp,” he says.
Rennie has found that his grazing management for breeding female animals has led to consistently good sourveld quality and quantity for each key period of the year. In midsummer, especially, the veld enables cows to produce good milk volumes for their calves. The herd’s average weaning weight at 210 days