Dr Paul Long Cheng and Dr Jeffery McCormick from the university’s Faculty of Agriculture and Life Sciences found dairy replacement heifers grazed on dual purpose cereal and brassica crops such as wheat and canola achieved higher weight gains and caused less environmental pollution through reduced urinary nitrogen excretion than heifers grazed on conventional pasture.
“Every year farmers needed to rear dairy heifers as replacements for their milking herds as part of their farm management routines,” Cheng said.
“Providing adequate high quality feed for these heifers is crucial, so they can reach their target liveweights at critical stages of their growth and development. Their ability to reach these target liveweights has significant implications for their successful mating and milk production in the subsequent lactation. We also know that rearing dairy heifers contributes to the environmental impact of dairy production, particularly nitrogen leaching, through the excretion of urinary nitrogen.”
To find the solutions to these challenges Cheng, McCormick and their team undertook a trial to examine if feeding the heifers different types of forages such as dual-purpose crops, like cereals and brassicas, would increase their live weight gains and reduce urinary nitrogen excretion.
Cheng’s trial used three groups of dairy heifers that were equally matched for live weight and their genetic ability as breeding cows (breeding worth based on the records of their relatives). Each group was randomly allocated and fed a different type of forage – a pasture (perennial ryegrass-white clover), a cereal (wheat) and a brassica (canola).
“At the end of the trial, and once we had done the analyses, we were delighted to discover that heifers grazing on either wheat or canola showed increased liveweight gains and lower urinary nitrogen excretion to the environment in comparison to the pasture-feed animals,” Cheng said.
During the four-week trial regular measurements were taken from the three forages for quality analysis and the uptake of the forages by the heifers themselves, shown by increased liveweights and reduced urinary nitrogen excretion.
“This type of regime had been used in Australia for over 20 years on mixed cropping farms, but this is the first time it has been used for dairy replacement stock in NZ. Australian farmers have found that the timing and intensity of grazing is important because if the animals graze for too long the plants’ reproductive growing tips can be damaged resulting in a loss of grain production,” McCormick said.
“That these dual purpose crops haves been shown to have an additional environmental benefit is an exciting discovery and will benefit dairy farmers throughout NZ. Local farmers are already interested in trialling these crops with their heifers.”
The scientific team included Dr Paul Cheng, Dr Jeffery McCormick, Professor Grant Edwards and Chris Logan, from Lincoln’s Faculty of Agriculture and Life Sciences. In addition, scholars from France and Thailand were involved in crop management and sample collection.
The research was presented at the 2014 Australasian Dairy Science Symposium and was well received.
