MANAGEMENT ROUTINE KEY FOR ENHANCED FERTILITY
Cow and heifer fertility has a big impact on margins and profi tability on farm impacting on milk yield, culls, sales and vet costs on all farms, consequently it’s crucial we attempt to optimise, says Advanced Nutrition’s vet nutritionist, Debby Brown.
Heifers
Replacement heifers are often assumed to have good fertility and should have a service/conception rate of less than 1.5, however, more and more farms are failing to achieve this. Average age at calving according to recent fi gures continues to be 28 months with two services per conception. However, with the increasing use of sexed semen, it is really crucial to ensure these heifers are grown well and are in ideal condition to optimise fertility and be in a position to successfully served at 15 months, calve at two years of age, milk well and get back in calf again.
Targets
0.8 to 1.0kg/day growth rate from two weeks age to pregnancy 10 to 13 months showing fi rst oestrus 14 to 15 months fi rst service 375kg* and 52” high minimum at fi rst service 1.3 to 1.5 maximum inseminations per pregnancy
*Holstein heifers should be a minimum 55% of mature cow bodyweight - measure third lactation cows at 100 days post calving, reaching 65% by time of conception.
To achieve these targets, measure heifer growth rate on a fortnightly basis up to weaning and thereafter every four to eight weeks until bulling.
Pre-bulling nutrition
Rearer concentrate, based on the heifer’s requirements and forage fed. For example, minimum 24% CP and 13MJ ME at 3kg for heifers on straw diet.
Silage from six months of age. Silage’s high level of acidity does not help rumen development and or make for optimum digestion. Reduce the rearer to between 16% and 18% CP depending on silage protein analysis. Energy levels MUST be controlled to stop heifers becoming too fat.
Allow 18” feed space a heifer Rumen protein (ERDP) 10g/%DM : Rumen energy (FME) ratio 10.5 - 11
Optimise minerals to match requirements and on farm availability, in particular watch out for zinc to reduce risk of digital dermatitis
120 THE JOURNAL DECEMBER 2014
Overfeeding high quality forages or excessive concentrates can accelerate heifer growth to the extent that they become fat. This is undesirable as it leads to a fall in lifetime milk production and longevity. Studies have shown that excessive intakes of energy - 140% of recommended levels - before breeding result in fatty infi ltration of the mammary gland and subsequent reduction of the number of alveolar cells available for milk synthesis.
Cows
The key infl uence on fertility is getting each animal back in to positive energy balance after calving and this means driving intakes post calving. The more condition lost post calving the longer she will take to resume cycling and, therefore, conceive. However, the dry period is one area to concentrate on simply because intakes
Targets
Less than 70 days calving to fi rst service More than 60% conception rate at fi rst service
Less than 90 days calving to conception Less than 1.5 services per conception
Less than 3% abortions at 45 to 265 days
Less than 5% culling due to infertility
in far off dry cows will infl uence intakes post-calving.
Aim for a minimum of 13kg DM in far
off dry cows, but keep the energy low, no more than 110MJ ME to ensure they do not lay down any fat in this period. In
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