Silage for dry cows is often seen as a lower priority fodder on dairy farms when compared with winter feed for the milking herd. It is less likely to have been tested for a silage analysis and so less thought usually goes into the dry cow diet.
But the dry period is an important phase in a dairy cow’s production cycle. If you get it wrong when the cow is dry, she will start the lactation on the back foot and might never catch up.
Samples of dry cow silage from phase two Dairylink Ireland farms have been tested for a standard silage analysis and a more detailed forage mineral analysis.
The aim is to ensure that dry cows have adequate energy intakes during the dry period, while reducing the risk of metabolic disorders pre- and post-calving.
There is a wide range of values across the measures, which are outlined in Table 1, and Dairylink adviser Aidan Cushnahan has set targets as a guide for what the optimum dry cow silage looks like.
Milk fever
The risk of milk fever associated with a dry cow silage can be seen from the dietary cation anion balance (DCAB) measure in a forage mineral analysis. A low DCAB creates slightly acidic conditions in the blood, which encourages the uptake of calcium and reduces the risk of the cow taking milk fever at calving.
“The recommended DCAB for dry cow diets is between -100 and -200 meq/kg DM, but it is very difficult to achieve a negative DCAB value in practice because grass is usually high in potassium (K),” Aidan said.
For example, on Richard Marshall’s farm, dry cow silage has a K content of 1.6% and DCAB is 233 meq/kg DM. This is still better suited for dry cows than other fodder on the farm, such as one pit which analysed at 4.3% K and 421 meq/kg DM.
Dairylink farmers take various steps to lower the K content, and the subsequent DCAB value, in silage which will be targeted at dry cows. The main one is to cut dry cow silage from land which has not received slurry or compound fertiliser with potash.
John Oliver includes ammonium chloride and magnesium chloride in his dry cow ration, which leaves the feed with a DCAB concentration of -70 meq/kg DM
Another step is to include straw in the dry cow rations at around 0.5kg to 3kg/cow/day. This is because straw has a low K content of 1% to 1.5%, which helps reduce DCAB levels.
Anionic salt supplements can also reduce DCAB levels. For example, John Oliver includes ammonium chloride and magnesium chloride in his dry cow ration, which leaves the feed with a DCAB concentration of -70 meq/kg DM.
Energy intakes
Cutting dates for dry cow silage are later than the main silage crop on Dairylink farms and this is reflected in metabolisable energy (ME) and digestibility (D) value, which averaged 10.2 MJ/kg DM and 64 respectively across programme farms.
It compares with ME and D-value averaging 11.4 MJ/kg DM and 71 for the silage crops which are currently being fed to lactating cows in the Dairylink group. Likewise, predicted intake values for dry cow and milking cow silages differ sharply, averaging 89 and 109 respectively.
“Dry cows have significantly lower energy requirements, so lower silage intakes should not be an issue, provided they are consuming 9kg to 10kg DM/cow/day,” Aidan said.
“It is important to ensure that dry cows have good access to feed to minimise any drops in intake when approaching calving and reduce the risk of transition cow disorders post-calving,” he added.
The target condition score for high-output dairy cows at drying off is 2.75 to 3.00 and dry cow diets are generally formulated to supply between 100 and 120 MJ/cow/day of energy to maintain this through the dry period.
On James Martin’s farm, the lower ME content of his silage means the recommended rate of supplementation is closer to 2.75kg/cow/day
“In most cases, this can be achieved for cows in the close-up group (four weeks before calving) by consuming 9kg to 10kg DM of silage plus 1.5kg to 2kg of pre-calver concentrate. On James Martin’s farm, the lower ME content of his silage means the recommended rate of supplementation is closer to 2.75kg/cow/day,” Aidan said.
Dry cows that are at the target body condition score and have access to good-quality fodder (D value over 70) should be able to meet energy requirements without additional concentrates, although mineral supplementation will still be required for three or four weeks before calving.
Monitoring cows
closely after calving
Dairylink Ireland farmers with autumn-calving cows have experienced few problems with transition cows so far this year.
Cows are being monitored for ketosis using a milk ketone testing kit. The metabolic disorder occurs in early lactation cows as a result of a severe negative energy balance and it can lead to issues with metritis, impaired fertility and reduced milk yields.
Similar to other health issues, such as milk fever, ketosis can occur subclinically, meaning the symptoms are not readily seen, but underlying issues can have an impact on cow performance.
Test strip
Milk samples are taken from cows that have calved over the previous two weeks and are added to a test strip. The colour change on the strip gives an indication of milk ketone bodies, known BHB concentration. Values over 200 suggest that the cow is suffering from subclinical or clinical ketosis.
“Samples taken at three autumn-calving Dairylink farms to date have all tested between 50 and 100. This suggests that feed intakes in the herds approaching calving and after calving are on target,” Aidan said.
Dry cow rations with low potassium and DCAB levels reduce the risk of milk fever.Most Dairylink farmers offer dry cow concentrates for four weeks before calving.Ketosis can occur on dairy farms subclinically, where there are no visible symptoms, but it is still affecting cow performance.
Silage for dry cows is often seen as a lower priority fodder on dairy farms when compared with winter feed for the milking herd. It is less likely to have been tested for a silage analysis and so less thought usually goes into the dry cow diet.
But the dry period is an important phase in a dairy cow’s production cycle. If you get it wrong when the cow is dry, she will start the lactation on the back foot and might never catch up.
Samples of dry cow silage from phase two Dairylink Ireland farms have been tested for a standard silage analysis and a more detailed forage mineral analysis.
The aim is to ensure that dry cows have adequate energy intakes during the dry period, while reducing the risk of metabolic disorders pre- and post-calving.
There is a wide range of values across the measures, which are outlined in Table 1, and Dairylink adviser Aidan Cushnahan has set targets as a guide for what the optimum dry cow silage looks like.
Milk fever
The risk of milk fever associated with a dry cow silage can be seen from the dietary cation anion balance (DCAB) measure in a forage mineral analysis. A low DCAB creates slightly acidic conditions in the blood, which encourages the uptake of calcium and reduces the risk of the cow taking milk fever at calving.
“The recommended DCAB for dry cow diets is between -100 and -200 meq/kg DM, but it is very difficult to achieve a negative DCAB value in practice because grass is usually high in potassium (K),” Aidan said.
For example, on Richard Marshall’s farm, dry cow silage has a K content of 1.6% and DCAB is 233 meq/kg DM. This is still better suited for dry cows than other fodder on the farm, such as one pit which analysed at 4.3% K and 421 meq/kg DM.
Dairylink farmers take various steps to lower the K content, and the subsequent DCAB value, in silage which will be targeted at dry cows. The main one is to cut dry cow silage from land which has not received slurry or compound fertiliser with potash.
John Oliver includes ammonium chloride and magnesium chloride in his dry cow ration, which leaves the feed with a DCAB concentration of -70 meq/kg DM
Another step is to include straw in the dry cow rations at around 0.5kg to 3kg/cow/day. This is because straw has a low K content of 1% to 1.5%, which helps reduce DCAB levels.
Anionic salt supplements can also reduce DCAB levels. For example, John Oliver includes ammonium chloride and magnesium chloride in his dry cow ration, which leaves the feed with a DCAB concentration of -70 meq/kg DM.
Energy intakes
Cutting dates for dry cow silage are later than the main silage crop on Dairylink farms and this is reflected in metabolisable energy (ME) and digestibility (D) value, which averaged 10.2 MJ/kg DM and 64 respectively across programme farms.
It compares with ME and D-value averaging 11.4 MJ/kg DM and 71 for the silage crops which are currently being fed to lactating cows in the Dairylink group. Likewise, predicted intake values for dry cow and milking cow silages differ sharply, averaging 89 and 109 respectively.
“Dry cows have significantly lower energy requirements, so lower silage intakes should not be an issue, provided they are consuming 9kg to 10kg DM/cow/day,” Aidan said.
“It is important to ensure that dry cows have good access to feed to minimise any drops in intake when approaching calving and reduce the risk of transition cow disorders post-calving,” he added.
The target condition score for high-output dairy cows at drying off is 2.75 to 3.00 and dry cow diets are generally formulated to supply between 100 and 120 MJ/cow/day of energy to maintain this through the dry period.
On James Martin’s farm, the lower ME content of his silage means the recommended rate of supplementation is closer to 2.75kg/cow/day
“In most cases, this can be achieved for cows in the close-up group (four weeks before calving) by consuming 9kg to 10kg DM of silage plus 1.5kg to 2kg of pre-calver concentrate. On James Martin’s farm, the lower ME content of his silage means the recommended rate of supplementation is closer to 2.75kg/cow/day,” Aidan said.
Dry cows that are at the target body condition score and have access to good-quality fodder (D value over 70) should be able to meet energy requirements without additional concentrates, although mineral supplementation will still be required for three or four weeks before calving.
Monitoring cows
closely after calving
Dairylink Ireland farmers with autumn-calving cows have experienced few problems with transition cows so far this year.
Cows are being monitored for ketosis using a milk ketone testing kit. The metabolic disorder occurs in early lactation cows as a result of a severe negative energy balance and it can lead to issues with metritis, impaired fertility and reduced milk yields.
Similar to other health issues, such as milk fever, ketosis can occur subclinically, meaning the symptoms are not readily seen, but underlying issues can have an impact on cow performance.
Test strip
Milk samples are taken from cows that have calved over the previous two weeks and are added to a test strip. The colour change on the strip gives an indication of milk ketone bodies, known BHB concentration. Values over 200 suggest that the cow is suffering from subclinical or clinical ketosis.
“Samples taken at three autumn-calving Dairylink farms to date have all tested between 50 and 100. This suggests that feed intakes in the herds approaching calving and after calving are on target,” Aidan said.
Dry cow rations with low potassium and DCAB levels reduce the risk of milk fever.Most Dairylink farmers offer dry cow concentrates for four weeks before calving.Ketosis can occur on dairy farms subclinically, where there are no visible symptoms, but it is still affecting cow performance. 
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