45 pregnant heifers were introduced to a property in the northwest slopes from the New England tablelands in mid July 2011. The heifers were kept in small paddock for ease of calving supervision. The owner reported that the heifers had lost condition over the previous month.
Pasture consisted of dry native grass. There was approximately 500kg DM/ha 3 weeks after the heifers had been put into the paddock. Supplemented with 0.5 kg WCS( white cotton seed) /head /day and 350 kg bale pasture hay/day = 7kg/head/day.
No calcium had been added to the WCS.
Low dry matter availability and quality, insufficient energy intake by heifers.
Calving commenced early August 2011. 11 heifers calved in next 3 weeks.
7 dead calves: 4 were assisted births, 3 unassisted births with calves found dead the next morning.
4 live calves.
Owner reported prolonged calving times, 7 to 8 hours from first noticing heifer calving to calf being produced. As the heifers were not obviously contracting, the owner found it difficult to identify the heifers during early parturition.
Had lived for 2 days. > 24 hrs dead at PM.
Severe diffuse fibrinous pleuritis and pericarditis.
Fibrinous adhesion between liver and peritoneum, on caudo-dorsal border of the liver.
Approximately 1 L red fluid in thoracic cavity.
Found dead that morning.
Oedema of face, head, neck, pharynx and larynx.
Petechial haemorrhages in proximal trachea.
Petechial haemorrhages epicardium and base of heart.
Hooves soft, unmarked - not walked
Lungs were variably inflated.
Post-mortem changes consistent with a prolonged difficult birth.
5 Heifers yarded for examination.
Body condition Score 1.5 -2 / 5.
Three (samples 1, 3 and 4) were very alert, hyperexcitable or stirry, shaky and staggery with muscle tremors.
All were pyrexic: rectal temperatures 39.9 - 40.2 c.
|BHB 0.00 - 0.80 mmol/L||0.12||0.15||0.06||0.06||0.14|
|CA 2.00 - 2.75 mmol/L||2.45||2.24||2.10||2.36||1.97 L|
|MG 0.74 - 1.44 mmol/L||0.85||0.88||0.72 L||0.75||0.66 L|
Heifer 1 dam of calf PM2, calved unassisted - calf found dead same morning.
Heifer 5 dam of calf PM 1. Prolonged calving, 3 days previously.
Calving has continued over 3 months with 3 heifers yet to calve. Heifers had changed paddocks 2 more times. They moved onto an oat crop, then in October the uncalved heifers were back on another native grass paddock with WCS supplement. The heifers have improved in condition, with average body condition score in early November being 2.5 - 3/5. Some of the calving problems seem to be due to foeto-pelvic disproportion. Difficult tractions, legs back, and malpresentations.
12 assisted calvings
6 dead heifers - 1 died, others euthanased.
24 live calves
18 dead calves
Chlamydia CFT: 32, 64, 64, 64, 128, 128 - higher than August group.
The heifers were moved into a larger adjacent paddock with greater dry matter availability( estimate 2000kg DM/ha) , standing dry grass with new green shoots after a storm. We advised to increase the amount of WCS to 2 kg/head/day and add 2% lime to the WCS, and to provide a lime/salt/causmag free choice loose lick. The producer found that the loose lick was not well taken up, so he added the causemag to the WCS instead. This proved to be a more successful method of providing the magnesium supplement.
Initially the heifers were not consuming the WCS, so the producer tried oats mixed with WCS which seemed to encourage their consumption. It is likely that the heifers preferred the green pick that was available when first put in the paddock. This paddock was on the side of a small hill, so provided more opportunity for exercise. Over the next 3 months rain periods through late September and October have ensured increased pasture growth, and improved pasture quality. The heifers had 2 paddock moves in the 3 months, a period on oat crop followed by return to native grass and WCS supplement.
There was a period of 2 to 3 weeks where they experienced few problems, then the dystocias started again.
The breeder from the New England Tablelands was reportedly also experiencing calving problems in the group of heifers he kept this year. These heifers were sibling mated, a practice the breeder had used with no problems in the past.
This is every cattle producer's nightmare after which they vow that they'll never buy calving heifers again. It is most probably a multifactorial problem.
Factors possibly contributing to the heifer calving difficulties are:
1. Weight of heifers at joining. What was the weight of the heifers at joining? As the calving period has spread out over 3 to 4 months, it would appear that the lighter weight heifers may not have been cycling earlier during the joining period, so became pregnant later as they reached critical mating weights. Further retrospective investigation into joining on the breeder's property would be desirable.
2. Bull factor. Do the bulls genetics contribute to larger calves. Again investigation at the breeder enterprise is needed.
3. Growth of heifers. Heifers need to continue growing through pregnancy, so that their skeletal growth continues and pelvis develops to accommodate parturition. The aim is to keep heifers growing at 0.6-0.7 kg/day. In this case the heifers suffered a set back in nutrition and growth rate, losing condition after arrival. Investigation into growth from mating to calving would be desirable for the full picture.
4. Metabolic knife edge. Interestingly the metabolic profile of these heifers showed more consistently low and marginal magnesium levels rather than hypocalcaemia, which we would associate with uterine inertia. One heifer was both hypocalcaemic and hypomagnesaemic. Is intake or availability of magnesium alone inadequate, or is the absorption of magnesium also being impaired?
The nervous signs observed in these heifers were consistent with early hypomagnesaemia, but did not progress to the violent convulsing tetanic condition and death.
5. Increase in nutrition, and body condition. How much has this contributed to calf growth and size in the last 2 months?
6. Infection Young introduced cattle into the region can become exposed to SBE and develop infection, with signs of weight loss, stiff gait or soreness, or neurological signs.
These heifers appear to have been exposed: did a subclinical infection affect their feed intake and metabolic condition?