Reproduction and fertility

Fertility is a huge issue for the Irish suckler cow and the period between calving and conception (post-partum interval) is the root of this. Though the trial in Table 1 was carried out in an indoor scenario, the principles remain the same: breaking the cow-calf bond will kickstart a cow’s reproductive system.

Pre-calving nutrition is just as important, if not more important than post-calving nutrition when it comes to cow fertility. In the study in Table 2, cows calved in either optimal or sub-optimal body condition score (BCS). Again, this is an international study – calves were weaned at day 35, but the biology holds. A cow’s reproductive cycle will be sluggish if she’s undernourished.

The numbers behind the BCS scale are outlined in Table 3.

More body condition score facts:

  • One unit of BCS in a typical Irish suckler cow equates to 70kg of live weight, versus 50kg in a dairy cow.
  • Target a slightly higher calving BCS with heifers (2.75-3).
  • At BCS 2.5: ribs just about visible, short ribs at loin (bones jutting out from spine) can be felt with slight pressure, some fat cover on tail head.
  • 660kg beef-bred suckler cow needs an equal amount of energy in late-pregnancy as a 600kg dairy-cross suckler.

    • Dietary consistency around breeding is vital. Figure 1 shows how conception rate plummeted in a trial where heifers went from high- to low-energy diets immediately following breeding. In an Irish setting, this means not pushing spring calvers too hard to clean out paddocks during the breeding season and potentially supplementing autumn-calving cows with meals before and during indoor breeding, depending on silage quality.

    Oestrus cycle and oestrus activity (heat) facts

  • Oestrus cycle length can vary from 18 to 24 days. It is typically one day shorter in heifers.
  • On concrete floors, there is an average of 50% less mounting activity and heats will be 25% shorter than on a soft surface (eg, pasture)
  • Pregnant cows or those between days 5-16 of their cycles are less likely to mount cows in heat.
  • Bad heat detection: 10% animal problems, 90% management problems.

    • Lessons from the research:

  • BCS at calving is hugely important for subsequent fertility – aim for 2.5.
  • First expression of oestrus will be brought on quicker where calves are completely removed from cows.
  • One unit of BCS in a typical Irish suckler cow equates to 70kg.
  • Keep feed consistent during breeding. If cattle are grazing, avoid chasing tight residuals during the period.
  • Heats are shorter and less pronounced on concrete floors.

    • In part two of the series, we will focus on picking suckler cow breeds and suckler beef greenhouse gas emissions.

    References

    Diskin, MG, and DA Kenny. "Optimising reproductive performance of beef cows and replacement heifers." (2014).