Rumen boluses can give an insight into how well cows are being fed and how producers can tweak rations further. Farmers Weekly reports.

A Welsh dairy farmer is making significant savings on feed costs after rumen pH boluses confirmed the amount of concentrates being fed to cows was too high.

Edward Morgan runs a 190-cow pedigree Holstein herd and has been focusing on cow nutrition to prevent acidosis.

Through his Farming Connect Demonstration Farm work, boluses were placed in six of his cows to monitor the pH and temperature in the reticulum.

Information gathered by the bolus has resulted in changes to the cow diet. The concentrate ration in the parlour has been reduced by 0.5kg and straw intakes increased from 0.5kg to 1kg. Sodium bicarbonate has been added to the ration to act as a buffer in the rumen.

Mr Morgan, of Carreg y Llech Farm, Mold, had been working with his vet, Gwyn Jones, to fine-tune the cow ration. The bolus, says Mr Jones, confirmed their decision to reduce the parlour cake ration by 0.5kg was the right one. “We will probably go further and reduce it again,” says Mr Jones, of Wern Veterinary Surgery, Ruthin.

“When a cow is fed in the parlour, she gets a high volume of concentrates in one slug and this causes a lot of acid to be produced in the rumen. When concentrates are fed in the TMR it dilutes this effect and reduces the risk of acidosis.”

Mr Jones says adding more long fibre in the form of straw encourages a cow to produce her own bicarbonate in the saliva, thereby neutralising acid.

“The most important thing with a dairy cow is that she is healthy. If she is not healthy she is not going to be at the peak of her performance. You get the rumen right and she is going to work with you.”

The eCow boluses incorporate a pH sensor and a thermometer. Computer technology records rumen activity and beams it to a reader outside the cow, giving a record of the pH and temperature inside the cow’s rumen every 15 minutes for five months.

A reading is taken every two weeks and the bolus has the capacity to store a month’s worth of data.

“The most important thing with a dairy cow is that she is healthy. If she is not healthy she is not going to be at the peak of her performance. You get the rumen right and she is going to work with you.”
Vet Gwyn Jones

There is an optimum pH for the function of the bacteria and protozoa which ferment the food a cow eats. When a cow eats any feed, but especially highly fermentable feeds, the pH drops until the ration buffering caused by salivation increases it.

The first few readings at Carreg y Llech showed a variation in pH in cows that were at the start of their lactation. As they moved further into lactation the pH became more balanced.

The ideal pH is 5.8 but the boluses showed two cows at Carreg y Llech dipped below the threshold with one animal, a heifer, recording 5.2.

Once the parlour ration was reduced the heifer’s pH immediately increased.

The reason for the initial low reading could be the result of lead feeding, where cows are fed in anticipation of the milk volume they are going to produce.

“We might have been overloading her with cake. We wouldn’t have known this had we not seen the effect in black and white in the graphs produced from the information on the bolus reader,” says Mr Morgan.

He says he is considering feeding heifers less in the parlour and possibly tailoring the ration to their body weight.

“If the rumen is working too hard and going into acidosis it will affect the performance of the cow and her longevity and how much milk she is producing. Hovering above that threshold is vital for good health,” says Mr Morgan.

The herd is autumn block calving with an average annual milk yield of 8,500 litres.

Placing a bolus in one in every 30 cows gives a representation of how cow rumens are performing.

Because the herd at Carreg y Llech has a seasonal calving pattern, boluses were placed in two dry cows and the other four in heifers, fresh calvers and cows that had calved 30 days previously. “That gives us a good picture of what is going on overall,” says Mr Morgan, who farms with his parents, Terrig and Gwyneth.

Dry cow pH 

“The biggest thing we saw was that the dry cows’ pH dropped dramatically. Because they were on the point of calving, their intakes dropped or it could have been because they were moving from the dry cow ration to the milking cow ration.”

The herd is fed maintenance plus 30 litres in the TMR and 0.4kg/litre in the parlour up to a maximum of 6kg.

The TMR ration incorporates 20kg grass silage, 0.5kg straw, 6.5kg 25% protein blend, 8.5kg wholecrop, 200g of a rumen-protected fat, 100g omega-3 and 2kg crimped wheat.

As the herd approaches the service period it is critical the diet is right to maximise conception rates. Ruminal acidosis can cause inflammation in the rumen, which can extend to the liver and lungs.

“Inflammation in the body can influence oestrus and embryo survival,” says Mr Jones. Acidosis can also cause secondary health issues.

Mr Morgan says that at £450 each, the boluses aren’t cheap, but believes the savings made on feed and improved cow health justify the cost. “From a nutritional point of view you don’t know what’s going on in the rumen. You can look at the muck but it doesn’t give the whole picture. The bolus does that.”

A bolus can help give a better idea of what’s happening in a cow’s rumen, meaning feed can be tailored as a result.