Making the Most from Mating

With the loss of induction as a management tool for condensing calving spreads it has become more important than ever to get cows in calf early.  Recommended mating lengths of 10 weeks are considered optimal to ensure all cows are calved by the 10th of October (if the PSM was the 23rd of October) to retain a healthy calving spread.  In this scenario a 10 week mating period would have bull removal occurring on the 1st of January.

The number of lactation days is one of the key economic drivers of your farms profitability.  Therefore success of mating should be measured in how quickly they get in calf (3 and 6 week in-calf rate) as well as the empty rate.  The reality of a 10 week mating period is that cows have just over 3 cycles to get back in calf.  The average cow has a ~50% chance of getting in calf at each cycle.  If given every opportunity she would have a 12.5% chance of being empty after 3 cycles.  However if she was to miss the first round of AI she will have a 25% chance of being empty.  Likewise if a heat is missed in the second round she has a 50% chance of being empty!

If your 3 week submission rate is tracking below the >90% target, review your heat detection practices immediately and look to get non-cyclers examined and treated.  Ideally all eligible non-cyclers (calved >40 days) should be mated inside 3 weeks.  This involves hormonal treatment by day 11 of mating at the latest.  Failure to take proactive action will result in not only a protracted calving spread but also a higher empty rate.

All eligible cows not mated after day 24 of mating should also be examined and treated accordingly. 

Backing Winners - Which Cows Should Be Treated With A CIDR?

Last season the reproductive outcomes were examined from 8,500 non-cycling cows treated from 64 farms in our practice.

This is the biggest single study conducted in NZ on CIDR outcomes at a commercial level.  From this study we were able to identify the optimal number of days-in-milk when treated, best time to treat relative to PSM and the optimal age of treatment.  Overall the average first service CR was 47% which is extremely good for cows being mated on the first oestrus for the season.  Cows under five years had the best response.  Optimal first service conception rate occurred from cows >45 Days In Milk (DIM) and optimal MT rates in cows >40 DIM.

Scours in Calves

A scour outbreak in your replacement heifers can have a devastating effect, not only on the calves but also the farm team.  As always, prevention is better than cure.

1. Keep the environment as "clean as possible".  Don't overcrowd pens, allowing 1.5 sqm/calf and no more than 20 calves/pen.
2. Ensure all calves get a minimum of 2 litres of fresh, good quality first-milking colostrum within 12 hours of being born and another 2 litres in the next 12 hours.
3. Ensure good routine in the calf shed, with milk at a similar temperature and consistency at each feed.

If you start to see calves beginning to scour:

1. Spread calves out as much as possible, either across pens or out into clean paddocks, weather permitting.
2. Consider getting 10 blood samples taken from 2-8 day old calves to check if they are getting enough colostrum.
3. Increase disinfection on the calf pens, calf trailer and feeding equipment.  Don't forget your boots and clothing too!
4. Get professional advice!
5. Ensure all scouring calves are getting adequate fluids each day.  This is 6-8 litres of fluid/day.
6. Critically sick calves that can't get up may need IV fluids and/or bicarbonate to get them up again.  I recently treated a calf which was very close to death with bicarbonate into the vein and had it up and drinking within 3 hours.

Salmonella brandenburg - Abortions in Cattle

Salmonella brandenburg abortions were first seen in sheep in mid-Canterbury back in 1996.  Since then a cyclical pattern has been seen, with outbreaks mainly in Otago and Southland.  Cases in cattle have been sporadically seen, but recently we have seen a concerning trend of increasing numbers, culminating in around five of our farms this year having confirmed Brandenburg abortions in their cattle.  The aborting cows typically present as off-colour for 1-3 days before calving a rotten calf (often with assistance).  These have been up to 50 days early, and many of the cows aren't coming into milk .  Scouring and death can also occur, and scours can also occur in calves.  Salmonella is highly zoonotic (contagious to humans) so good hygiene should be maintained in any cases with suspicious signs.  Individually affected cows should be treated with oxytetracyclines, anti-inflammatories, and fluids.  Aborting animals will shed high numbers of bacteria, so are an important source of transfer and environmental contamination.

Transfer of Salmonella brandenburg onto new farms is likely to occur in one of three ways:

• Firstly infected cows can become non-clinical latent shedders.  Purchase of these latent shedders can bring the disease onto your farm.
• Secondly environmental contamination of pasture/yards/waterways/trucks can lead to transfer.  Salmonella is likely to last just 1 week in bright, exposed, sunny conditions, but can last between 4 months to 2 years in covered areas (including cattleyard dust).
• Finally it is thought that scavenger birds (such as seagulls) can transfer the bacteria between properties.

One of the main control measures currently being used is vaccination with Salvexin+B, along with picking up dead calves, reducing stress, and avoiding areas of high contamination (including cleaning trailers etc).  Because Brandenburg is an emerging disease there is no research into vaccination in the face of an outbreak, however anecdotally it has been reported to decrease the incidence of abortions and death.  The majority of interventions have had no ill effect on the cows, however there has been one incidence of downer cows post-vaccination so any decision to vaccinate should be discussed fully with your veterinarian to weigh up the pros and cons.  As with any disease, vaccination prior to exposure is better than in the face of an outbreak, so future vaccination programmes will need to be implemented on at-risk farms.

If you are seeing any similar cases contact your prime vet to make a plan for diagnosis and control.

Preventing Metabolic Problems

Getting magnesium supplementation right over spring is likely to have the greatest effect on reducing the incidence of metabolic problems.

The cow is totally dependent on what magnesium is supplied in their daily diet.  The magnesium  content of spring grass is relatively low and only a small percentage of this is absorbed by the cow.  One of the main factors affecting availability of magnesium is herbage potassium levels.  High pasture potassium level causes significant decline in absorbable magnesium, particularly in spring when herbage magnesium is at its lowest.

Start supplementing with magnesium daily for 3-4 weeks pre-calving.

The best way to achieve the required dietary magnesium concentration pre-calving is to add 60 grams Mag C or Mag S/cow/day into the water supply and dust pasture/silage with 50-70 grams Mag Oxide/cow/day as well.

If the herd is experiencing more than a 3% incidence of milk fever despite sufficient magnesium supplementation then colostrum cows can receive calcium supplementation via lime flour at 200g/cow/day dusted on the break.  Lime flour can continue to the milkers at 100g/cow/day for the first 6 weeks after calving if required.

To avoid metabolic problems:

1. Maintain adequate dry matter intakes over the spring period
2. Supplement with sufficient magnesium
3. Avoid grazing potassium rich effluent paddocks with springers and colostrum cows
4. Avoid excess applications of potassium rich fertiliser during the months of June - October.
5. Blood test mature cows on day 3-4 of the colostrum period for metabolic profile.