Case Study: Improving Calf Survival Through Pre-Calving BCS and Mineral Nutrition
Historically, tight margins for suckler producers leave little room for losses that could otherwise be avoided. When every live calf represents income, unexplained losses can quickly become both expensive and disheartening. When Willie Gray of Balquharrage Farm near Glasgow was facing unexplained still born calves and neonatal deaths he sought some expert advice, funded through the Farm Advisory Service to help get to the bottom of the problem.
Background
Willie Gray runs a commercial suckler herd of around 90 cows of mixed breeds along-side an arable unit. Cows calve in three tight batches in summer, winter and spring to make the most of available shed space and limited labour. All progeny are finished on farm and sold direct to slaughter with a proportion of the heifers being retained to calf down at 2.5 years old. Historically Willie favoured highly muscled continental breeds using British Blue and Limousin bulls. He had accepted that with these breeds there would be a higher level of intervention at calving. In 2022, however, Willie was faced with a number of problems at calving including an unusually high level of stillborn calves and others dying shortly after birth. This was also coupled with a greater number of navel infections and joint ill cases.
Initial Investigations
Willie had contacted his farm vet regarding this problem when it first became apparent. The first post-mortem showed, amongst other things Neospora antibodies. As a farm which has many fields located near towns with possible dog access, he was quick to assume that this was the sole cause of his issues. Conversations with his local agricultural consultant prompted him to query this further and additional samples and post-mortems were carried out. As the problems progressed it was noted that cows were slow to calve, required assistance at calving, and calves were dopey/slow. Three stillborn calves and another four that died shortly after birth were sent to SRUC Veterinary Services for postmortem. Bloods were also taken from the cows to assess their mineral status. In addition the forages being fed to the cows, which included silage and hay, were also analysed for feed value and minerals.
Results
Viewed alone the calf post-mortems showed no singular cause of death. Further examination and comparison of all calves together found that all the calves submitted for post-mortem had obvious signs of trauma and associated foetal distress, consistent with difficulty calving, despite Willie deeming the submitted calves to have been born unassisted.
Pre-calving blood samples revealed low magnesium levels and elevated Non-Esterified Fatty Acid (NEFA) levels in the cows. Elevated NEFAs are an indication of excessive fat mobilisation in the lead up to calving, suggesting the animal received insufficient energy from her diet and had to call on body reserves. Magnesium is an important mineral for strong uterine contractions during calving. Thus, low magnesium can weaken uterine contractions leading to prolonged (slow) calvings. Affected cows can show little sign of active labour but the calf can endure stress. These findings were in line with the on-farm observations of unassisted calvings and post-mortem evidence of calf distress.
Forage analysis indicated that the silage being fed to the cows was of high quality, with good energy and protein levels as shown in the table below. Mineral analysis showed high potassium (above 20 g/kg DM or 2% DM) in all silages, which was causing a lock up effect on magnesium and reducing its availability. Therefore, the target for magnesium supply in the whole ration was increased to 30 g of magnesium for dry cows and 40 g for lactating cows to counteract this effect. The trace element requirements including copper, selenium, zinc, manganese, and cobalt would not be met from silage alone, therefore supplementation of these minerals was also advised.
| Parameter | Balquaharrage 1st cut | Balquaharrage 2nd cut | Lenzie 2nd cut | Comments |
|---|---|---|---|---|
| Dry Matter (%) | 17.3 | 24.8 | 45.6 | 1st cut is the wettest so cows will need to eat more of it but is the highest quality. |
| ME (MJ/kg DM) | 11.8 | 10.6 | 10.8 | 1st cut is best suited for close up/post calving period due to high energy. |
| Crude Protein (% DM) | 16.5 | 13.2 | 9.3 | Varying protein levels needs to be balanced differently. |
| NDF (% DM) | 44.5 | 45.6 | 47.6 | Higher fibre content in Lenzie silage linked to lower energy (ME). |
| pH | 4.2 | 4.4 | 4.4 | |
| Calcium (g/kg DM) | 5.81 | 8.45 | 5.90 | Supplementation advised. |
| Phosphorus (g/kg DM) | 3.98 | 4.62 | 2.66 | Supplementation advised. |
| Magnesium (g/kg DM) | 1.94 | 2.15 | 1.62 | Due to high levels of potassium this increases the target requirement to 30 g for dry cows. Silage will not meet requirements. |
| Potassium (g/kg DM) | 37.5 | 31.3 | 20.9 | All silages are above 20 g/kg DM therefore increasing level of antagonism which needs to be corrected. |
| Copper (mg/kg DM) | 7.45 | 9.10 | 4.62 | Supplementation advised. |
| Selenium (mg/kg DM) | 0.365 | 0.244 | 0.028 | Supplementation advised. |
| Cobalt (mg/kg DM) | 0.134 | 0.188 | 0.111 | Supplementation advised. |
| Manganese (mg/kg DM) | 153 | 181 | 147 | Supplementation advised. |
| Zinc (mg/kg DM) | 26.8 | 29.6 | 24.0 | Supplementation advised. |
Next Steps
With post-mortem results indicating that there may be a nutritional rather than disease-based cause behind the neonatal deaths, it was decided that a multi-faceted approach would be required to find the solutions. In November 2022 Willie applied for a Specialist advice plan through the Farm Advisory Service to get to the bottom of the issues. His team comprised of local SAC consultant Jennifer Struthers, SRUC vet Helen Carty (who carried out the post-mortems), SAC ruminant nutritionist Mary Young and the local vet.
Farm Meeting
Gathering a team around the kitchen table allowed all the pieces of the puzzle to be viewed together with first hand evidence from Willie about the overall situation. At this time the summer batch of cows (which had calved very badly) were not the issue, but the concern was to ensure that the situation was not going to be repeated in the cows to calve in the January and April batches.
An assessment of the cows that were 8 weeks pre-calving revealed them to be body condition score (BCS) 3.5, with some BCS4+, well above the BCS 2.5 target. A real misconception of not wanting cows to look “too thin” was identified and it became apparent that the Balquaharrage cows had always been in good condition. Through a hands-on demonstration Willie was able to see the difference between condition scoring by eye and by physically handling the animal.
Cows were fed ad-lib using bales or pit silage top dressed with a general-purpose powdered mineral due to many sheds not allowing all cows to access the feed at the same time. The unrestricted access to good quality silage was a contributing factor to the body condition score of the cows while also making it impossible to ensure all cows were accessing the mineral. In addition, the silages analysed high in potassium (above 20g/kg DM) and the general-purpose mineral was found to only contain 9% magnesium, slightly below the 10% target for pre-calving cows.
Moving Forward
As a result of the very good body condition, silage intakes by the cows were reduced meaning that they were starting to mobilise body fat, hence the high NEFA results. It was agreed that it was too late to alter the cows’ body condition without causing stress to the animals and any further metabolic issues. Getting sufficient magnesium into the cows was also a high priority. Flying in the face of instincts it was decided to feed the January calvers some barley alongside their silage. Whist it seemed controversial to feed already fit cows more, it was decided that the most important step was to ensure that the energy and protein requirements of the animals were being met. This also allowed the barley to act as a carrier for a mineral with a higher magnesium inclusion rate, fed at 15 – 20%.
The later calving batches were formulated to allow for a moderate level of condition loss (-0.2kg/day) until a month before they were due to calve.
Did It Work?
Following these actions the feedback from Willie was very positive with 85% of cows calving in the first 3 weeks with no assistance – a trend that has continued in subsequent years. Going forward the aim has been to continue to get cows in target condition and avoid over conditioning them at grass. Forage analysis, correct mineral supplementation and ration formulation have also continued to ensure cows are being fed to requirements.
Conclusion
Willie’s experience highlights the value of stepping back and taking a fresh look when problems arise or when performance starts to slip. By seeking further advice and bringing together veterinary, nutrition and advisory expertise, the underlying contributing factors were identified, and practical changes were put in place before further calving batches were affected.
One of the key lessons from this case study is the importance of body condition scoring. While well-fleshed cows may appear healthy and productive, over-conditioned cows can be at greater risk of metabolic and calving related problems. Regular hands-on body condition scoring is an essential management tool that ensures cows are maintained within the target range.
The second key lesson is in assessing your forage to ensure any supplementary feeding is meeting the nutritional and mineral requirement for the animal, and that all animals have sufficient access to the feed or mineral source for their intake requirements.
Take Home Messages
- Target body condition score at calving should be around 2.5 to 3.0
- Over-fat cows can have reduced feed intakes pre-calving, increasing the risk of excessive body fat mobilisation and metabolic stress.
- Adequate magnesium intake is critical for effective uterine contractions and successful calving.
- Forage analysis, ration formulation and appropriate mineral supplementation should form part of routine pre-calving management.
Mary Young, SAC Consulting
Jennifer Struthers, SAC Consulting
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