LOWERING THE crude protein content of rations for an 11,500-litre Holstein herd has flattened lactation curves, reduced body condition losses after calving and improved fertility.
An added benefit of lower protein diets is the muck contains less protein nitrogen, making it more suitable under cross-compliance rules.
Stephen Temple”s 120 cows, at Copys Green Farm, Wighton, Norfolk, have spent their fifth winter eating a lower protein diet. And it is the third winter the farm”s independent nutritionist Rodney Allen has used Feed into Milk software to work out the mixed ration, which contains just 17% crude protein.
“Previously, it would have been 18.5-19.5%. This was considered normal under the old metabolisable protein system,” says Mr Allen.
Cows need protein for body main<00AD>tenance, to produce milk and muscle, and develop a growing calf. Until the late 1990s, nutritionists recommended Holsteins should be on 18.5-20% crude protein diets.
“This produced a massive and rapid peak yield – at least five litres a day more than now – because protein stimulates milk production. The problem is the cow”s energy requirements aren”t matched by voluntary intake, resulting in a big negative energy balance,” he says.
This is responsible for mobilising excess body condition and cows losing at least one score, about 70-80kg in weight, in the first six weeks of lactation. This leads to poor condition, cows not cycling and often cystic ovaries when a cow needs to get back in calf, says Mr Allen.
Long-term protein status is indicated by the gradual effects on milk protein content, he reveals. Simply adding more quality protein into the diet only makes things worse.
The Feed into Milk project – sponsored by DEFRA, DARD and SEERAD plus industry partners – reviewed Dutch, French and US practices, and how nutritionists look at high yielding Holsteins.
“The conclusion was that high protein wasn”t necessary provided the diet offered at least 30% as rumen bypass protein, paid attention to the limiting amino acids methionine and lysine, and matched the energy source correctly.”
The French fed 16.5-17.5% protein including protected protein products; the Dutch went as low as 14%. “We used to say a Holstein needed 66MJ of ME for maintenance each day, plus 5.3-5.5MJ for every litre produced depending on butterfat content,” says Mr Allen.
But Feed into Milk found that cows giving 40 litres a day actually need 6MJ/litre, while maintenance needs are 80-85MJ, plus extra for calf growth. Considering Mr Temple”s cows weigh 725kg liveweight and output stands at 11,521kg with 3.97% butterfat and 3.09% protein, this makes quite a difference.
“Lowering crude protein together with balancing energy inputs means cows peak lower, at 50 litres, but maintain yields longer. They are often still giving 30 litres at drying off. They are also more fertile.”
Despite improvements in body condition, the calving index has crept up to 450 days. The herd also generates income from pedigree sales and treats cows as individuals, says herdsman Mike Toms.
“Cows calve in good condition, but instead of losing 0.5 to 1 condition score, we see more cows at score 2.5 six weeks after calving,” he adds. “We have a policy of not serving high yielders so soon. On average, first service is at 80 days.”
After changes to the diet formulation, milk proteins have risen from 3% to 3.22% at the recent test. Butterfats are 4.24%. Although the farm supplies a liquid contract, constituents are important for the 5% of milk processed on-farm into Mrs Temple”s Farmhouse Cheese.
When the annual average butter<00AD>fat reaches 4.1%, Mr Temple thinks it will be worthwhile changing to a constituent contract.
Production costs a litre will always be higher than the average 6000-litre herd, but the aim is to trim them without compromising output. Mr Allen believes cows are responding to the money spent on higher quality protein and says other options include growing lupins.