Farmer's Weekly (South Africa)
Dairy farming: achieve higher milk solids with soya bean hulls in feed
Partially substituting maize with soya bean hulls may lower dairy cattle feeding costs while increasing income generated from milk solids. Anesmé van der Vyver, a master’s student at Stellenbosch University, spoke to Glenneis Kriel about her research findings.
As a typical concentrate for grazing dairy cows consists of up to 80% maize grain, the partial substitution of maize with highly digestible by-products is one way of buffering the impact of maize price fluctuations and spikes.
Previous research at the Outeniqua Research Farm indicated that the partial replacement of maize grain with bran, hominy chop and Tongaat Hulett’s Gluten 20 did not have a negative impact on milk yields and actually increased milk fat percentages. Researcher Anesmé van der Vyver therefore decided to evaluate the impact of using soya bean hulls, a by-product of the bean extraction process, as a partial replacement.
SOYA BEAN HULLS RESULTED IN MILK WITH A HIGHER SOLIDs CONTENT
Her research was conducted in partial fulfilment of her master’s degree in Animal Sciences at Stellenbosch University, under supervision of professors Robin Meeske of the Western Cape Department of Agriculture and Chrisjan Cruywagen of Stellenbosch University.
METHOD
Fifty-one Jersey cows at the Outeniqua Research Farm of the agriculture department were used to determine the impact of replacing maize with soya bean hulls. The cows were divided into three groups of equal size.
In the first group, no soya bean hulls were included in the animals’ concentrate treatment. In the second and third,
15% and 30% respectively of the maize was replaced with soya bean hulls.
Van der Vyver did not attempt to substitute more than 30% due to the nutritional differences between maize and soya bean hulls.
“Maize has a high starch but low neutral detergent fibre content, whereas soya bean hulls have a low starch and a high neutral detergent fibre content,” she explained.
Each cow received 6kg/day of concentrate during milking. After visiting the milking parlour, the cows strip-grazed kikuyu pasture oversown with an annual Italian ryegrass, allocated at 10kg dry matter/cow/day.
The crude protein content of the concentrates was 11% and that of the pasture 19,4%. As the soya bean hull content of concentrates increased, so the neutral detergent fibre content increased.
RESULTS
The soya bean hull treatments did not compromise milk yield ( see table 1), but there was a tendency for the milk fat percentage to be higher with the 15% soya bean hull inclusion. The milk protein and lactose content were also significantly higher when soya bean hulls were included in the concentrate.
Cows were not negatively affected by the partial substitution of maize with soya bean hulls. While there was no significant difference in weight gain, the body condition of the cows receiving the
15% soya bean hull inclusion was significantly better than that of the cows in the other two treatments at the end of the 50-day experiment.
Van der Vyver used the results to analyse the financial impact of the partial substitution on farm income.
“It would be difficult to quantify savings in terms of feeding costs, since the prices of maize and soya bean fluctuate a lot depending on supply and demand. I therefore only looked at the impact that higher milk solids would have on farm income,” she said.
The milk price increased by 20c/ℓ for the cows receiving a concentrate containing 15% soya bean hulls, due to the higher solid content of the milk. Van der Vyver calculated that this would translate into a R52 812/month saving for a 400-cow operation, providing the price of maize and soya bean hulls were equal.
“Based on the results, it makes sense for dairy farmers who are rewarded for high solids to substitute 15% of the maize in their concentrate with soya bean hulls,” she said.
• Email Anesmé van der Vyver at anesmevdv@elsenburg.com.