It's a joy to have such good ground conditions in these autumn weeks as winter fast approaches. The colder evenings herald the oncoming darker months ahead and so we must prepare to move stock indoors. In the case of our pregnant animals, that does not simply mean putting down a fresh bed. Nutrition and diet management is one of the biggest factors in herd health. If diet is not correctly managed this will affect all other aspects of the herd's routine.
This is especially so in relation to the pregnant animal, from the in-lamb ewe to the beef cow, right up to the dairy herd. The dairy cow is most vulnerable of all, as she is arguably the hardest working member of our farmed animals over the winter months. Winter calving cows for liquid milk production are most at risk if nutrition is not tip-top. Other enterprises may be less affected, but an eye to the winter-calving cows' difficulties will help understand how critical it is to control winter diet in all animals.
Low magnesium levels exist in the autumn grass at present. Lactating cows are most at risk and so are their peri-parturent sisters. These are the cows just before, during and immediately after calving. We see all too many calving difficulties due to low blood magnesium levels coupled with the drop in blood calcium at calving time. These cases present as a cow-down-urgent-calving.
Get there post-haste. All aspects of difficult calving are present with these cases. The common culprit is sub-acute tetany or milk fever. Both of these bandits strike hardest at this time of year. Increase the magnesium intake via the nuts, water, bolus or mineral top dressing to avoid many of these urgent cases. Avoiding them is the only way to go as they nearly always lead to some disaster or other.
That kick from pre-calving to instant massive milk production post-calving is the single switch-on surge that many cows don't quite make. We know already that the cow will need to burn off her stored fat in those few weeks after calving just to keep pace with her production output at the mammary gland.
No matter how much goes in at the front end she will never get enough energy to counter-balance the losses out through the milk. And so she burns her fat. But any deficiency in energy in her diet will further deplete her fat stores. She will quickly run out and may eventually begin to burn off essential body tissues. She literally milks off her back. Deficiency in dietary energy and minerals again leads to low blood calcium in particular. Calcium is used in all tissues and especially in muscle function.
Sub acute hypocalcaemia means the muscles in the rumen wall don't function. The cow is weak on her legs. She gets a drop in appetite, which will exacerbate the problem. The muscles at the teat ends won't close. Proper milk let-down does not occur.
She lies down in the yard soon after milking. And now the somatic cells go haywire. Ketosis kicks in in a big way. Very quickly, we have a serious problem on our hands. It's as if someone put sand in the diesel tank.
To avoid the above scenario, we go through a checklist:
If cows are under-performing post-calving with a greater than 2-3pc incidence LDA, then an immediate suspicion of low energy intake or supply is made. Your veterinary practitioner will take blood samples of specific cows based on clinical examination and on milk records. Levels of fatty acids (energy in the blood) are assessed and various results will indicate what action is required. Mineral levels, including magnesium and calcium in the blood, are also assessed.
The results of inadequate energy intake will present as inappetance, raised somatic cells and milk drop, among others. Once confirmed and rectified, a remarkable turnaround in the herd's performance can be expected. Best of all is to prepare now to supply more than adequate mineral and energy intake while paying attention to the above list.