Around 90% of herd fertility is management related and less than 10% heritability in breeding fertility from one generation of cow to the next, according to Andre van Barnaveld, Dairy Consultant, Livestock Improvement Corporation (LIC) Ireland.
He says that any short-term fertility opportunity is without a doubt within the management of the farm and herd feeding and systems.
Cow Body Condition Score (BCS) at calving, he said, is one of the major influencing factors in achieving high six-week in calf rate, 0.5 of a BCS resulting in seven to 10 days shorter interval to first oestrus, higher submission and conception rates.
Mature dairy cows should be BCS 3.25, 1st and 2nd calvers BCS 3.5 at calving, he said. “Cows with BCS below 2.5 should be well dry by now to allow time to recover but care must be taken to maximise the feeding through the dry period.
“Energy is the most important nutrient in the cow’s diet. Whether she is eating grazed grass or ration, this statement always holds true. If cows are not milking as well as they should, the problem is usually a lack of energy. If milk protein is not right, it is energy. Similarly, if cows lose too much BCS, it’s energy. Energy drives everything and it is the most important nutrient in dairy production systems.”
He said that taking this into consideration, getting BCS back onto cows in the dry period is generally governed by just a few things:
1. UFL or MJME of the combined feeds offered;
2. DMD of the total intake;
3. Quantity of intake;
4. Health status of the animal (parasites and disease); and,
5. Days prior to calving.
He advises that maintenance demand of the in calf cow changes dramatically as she nears calving. “A 550kg LW cow’s maintenance demand is around 7kg DM/day 12 weeks prior to calving, lifting to 10.5-11DM/day at 3-4 weeks prior to calving, so the window of opportunity for BCS gain basically closes as she nears calving, any additional energy intake going to the growth of the unborn calf.”
The quantity of feed the cows are able to consume during the dry period is restricted mostly by DMD, he says. “As cows are offered a large proportion of their diet in silage, this takes much longer for the rumen to digest than fresh pasture which means intake is limited by fill capacity. Lowering the proportion of the intake as silage and lifting higher digestibility feeds (e.g. fodder beet, lower fibre/high energy rations) will raise the quantity of DM the animal is able to consume.”
To achieve 0.1 BCS every 10 days, a 550kg LW cow needs to consume around 4 UFL (4kg DM high quality feed) above maintenance. At 12 weeks prior to calving this would mean intake of around 11kg DM/day. At four weeks prior to calving this would mean 14-15kg DM/day which is pretty much unachievable on a predominantly silage diet and therefore from three weeks prior to calving the focus must be on a healthy calving, not BCS gain.
His advice is to:
• Ensure you allow enough time to achieve optimum BCS;
• Run below 3 BCS cows in a separate mob and maximise their intakes using the above criteria to maximise the BCS gain;
• Review on a weekly basis and draft out cows that have achieved the target BCS into a maintenance diet group; and,
• The right energy intakes in the last two weeks will prevent calving difficulties and placenta retention.