Non infectious: Effect on calving interval Flashcards
to maintain a 365 day claving interval cows need to conceive within how many days
80days
Voluntary waiting Period
Time after calving during which no insemination are to be performed -even if the cow is detected in heat
most= 30-60days
What are the dangers of having a overly short VWP
< 30 days will provide high conception rates and reduce semen use and cost, reduces the conception rate and only provide a few extra pregancies
what are the dangers of a long VWP
> 60days will provide for high conception rates and reduce semen use but also reduce the 100day in calf rate and increase the 200day not in calf rate resulting in unnecessary delay to becoming pregnant and increasing delay to becoming pregnant and increasing the average days in the milk for the herd
what are the effects of significant loos of BCS following calving
increase intervals from calving to first ovulation
decrease conception rates
Increase embryonic loss rates
what are the general BCS targets for beef cows
min 3 at calving
min 2.5 start of mating (on a rising plane of nutrition)
heifers at a correct size at calving are more likely to
have higher lifetime milk production
have better reproductive performance
Calve more easily
stay in herd longer
Define critical mating weights
the weight at which 85% of heifers fall pregnant over 45days (2 cycles)
= weight at puberty as it reflects the weight at which most heifers for a breed will be cyclin and have a higher probability of conceiving and maintaining pregnancy
what is meant by Daughter fertility ABV
Rates sires by the fertility of their daughters ==> high abv will produce genetically more fertile daughters than a sire with a low ABV
Calculated by measuring the reproductive performance of each sires daughters
Average daughter fertility is 100
Explain how cross breeding can improve fertility
crossbred cows are recognised as having higher fertility because the fertilty trait has a good levels of hybrid vigour
less likely to be culled as empty
Crossbreeds are more fertile only with good management
Days of calving EBVs
are estimates of genetic differences in fertility, expressed as the no. of days from start of the joining period - expressed as the no. of days from start of joining period until subsequent calving.
Lower or more negative for days of calving are favourable and are associated with early heifer puberty , return to oestrous after calving and early conception
How many bulls should you have per 100 cows
2.5-4%
1 bull per 30heifers
what is your aim for duration of breeding in the southern hemisphere
65-70% calves born in first 3 weeks, followed by 20% in the second 3 weeks and 10% in the thirds 3 weeks
produces an even line of claves of roughly the same age, making them easier to manage and market
Min of 45days to max of 60daus for bulls to run with cows
what is the aim of the “green date” in the northern hemisphere
no. of days after the 1st of October to achieve 70% chance of receive 50mms of rain over a 3 day period
Aim is to try and match a cows nutritional needs to the amount of quality feed on offer
What is meant by seasonal or controlled mating
only allowing bulls to be with the breeding herds for selected weeks or months of the year to control when cows get pregnant and therefore when they calve
Objective is to time calving to coincide with peak pasture availability and quality to ensure
In the northern beef = avoid lactation during the nutritional challenging dry season
