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How well dairy cows are managed throughout the dry period will impact milk yield during the following lactation and subsequent herd fertility, a leading dairy cow nutritionist has pointed out.
During a recent Agriculture and Horticulture Development Board (AHDB) webinar on transition management in autumn-calving herds, Hefin Richards from Rumenation Nutrition Consultancy focused on the key areas as cows are dried off.
He acknowledged that most discussions around nutrition center on the desire of the farmer to maximise milk yield and get cows back in calf.
“However, both of these are often linked to what happened in the period from dry-off to calving. If we put more attention on this area, we will see benefits in terms of health, production and fertility,” he said.
The goal of the transition period should be to have a healthy cow and calf on the ground, and no issues with milk fever, metritis, ketosis and retained cleanings.
According to Richards, the transition period should be viewed as a triangle split into four components; the cow, the diet, environment and general management.
Body condition
“The cow should be in the correct body condition for calving down at the point of drying off. You do not want to be making any significant changes in the dry period,” he said.
Over-conditioned cows at calving are more likely to be prone to issues such as milk fever, ketosis, etc.
However, there is also a link between cow condition and fertility. Fertile cows go back in-calf early, and therefore tend to avoid extended lactations, which ultimately can deplete body condition and impact negatively on the next lactation.
Challenges
Within herds, there are numerous practical challenges to deal with.
Older cows are more prone to issues with milk fever and retained cleanings, so must be managed carefully, while lameness coming into the dry period is “a complete disaster”, and should be addressed before cows are dried off, said Richards.
When adding cows to the dry group, he said it is preferable to do this weekly rather than adding cows every two or three days, as each time more cows enter the group, the dynamics change, increasing the risk of stress.
On the issue of managing heifers, ideally they should be kept as a separate group from mature cows, as mixing young and mature animals increases the likelihood of bullying, leading to depressed intakes in first lactation animals.
“If first calved heifers are going to mix with mature cows post-calving, they should be phased into the group and fully integrated by at least one month before calving,” advised Richards.
Diet
Regarding the diet for dry cows, he emphasised the importance of meeting, but not exceeding, energy requirements.
“We don’t want to be putting condition on these cows when they are dry. Silage with an ME of 11.5 – 12 will lead to excessive weight gain and run into a lot of problems,” said Richards.
“The challenges are always linked to high potassium (K) green forages. For dry cows, K is our biggest enemy,” he added.
Silage fed to dry cows should be made from mature grass that received no slurry and fertiliser with no K included. Some of his farmer clients are now utilising wholecrop rye.
The diet must also meet protein requirements, both to ensure good-quality colostrum and the needs of a rapidly growing foetus.
Environment
In dry cow housing, Richards said that lying space is often inadequate for heavily-pregnant dry cows.
“Water access is also important, with a minimum of 10cm per cow and more than one trough per group to reduce bullying. The dominant bully cows are very clever at realising where they can assert their dominance. A single water trough gives them a very powerful position,” he pointed out.
He also suggested that feed space is often under-estimated by farmers. It needs to be around one metre per cow to allow smaller, shy cows to access the forage without restriction. “Keep feed bunks clean and the food fresh and palatable,” he urged.
Rumen fill
When it comes to assessing dry cows, Richards said that rumen fill is a good indicator of feed intakes during the dry period.
It is judged by looking at the left flank of the cow, and the triangular area from the last rib running to the hook bones.
There is a strong link between animals with poor rumen fill during the transition phase and metabolic problems in early lactation and subsequent fertility.
Using farm data from Premier Nutrition, Richards highlighted that in cows with below optimum rumen fill scores (RFS) at 1 and 2 pre-calving, milk yield at four weeks into lactation was 28.6l/day and 32l/day respectively. Increasing to a RFS of 3, milk yield at four weeks into lactation was 39l/day.
“Getting from 1’s and 2’s to 3’s and 4’s was worth 10l per cow per day post-calving. Rumen fill is very important. If we identify on a group level that rumen fill is below target, we need to look at the feed, feed space etc. If we are looking at individuals below target, then those animals need further investigation,” he said.
Ration
To ensure good rumen fill, Richards advised that the dry cow ration should have moderate energy density.
Minerals should also be balanced, particularly when dry cows are eating grass silage, which oversupplies potassium. In this situation, it is necessary to counteract with anionic salts.
“One size most definitely doesn’t fit all - it is about finding the strategy that works on your farm,” said Richards.
Heat
He also highlighted that autumn calving means cows are going dry at a time when heat stress can be an issue.
“It is very much about managing the environment – ventilation, fresh air, shade, water access, water cleanliness, feed hygiene. When they are under heat stress, they are less likely to eat, so the food must be fresh and palatable,” he said.
“Be very aware about issues around overcrowding. Fans work well in dry cow and calving areas, and that would be the first place I would put fans,” he concluded.
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