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
Continuous mating system
Breeding females are exposed to bulls throughout the year
Spread of calving throughout the year and frequently occurs where properties cover large areas, with loss stocking rates, minimal infrastructure and where bulls and water supplies are not controlled
define “phantom cows”
cows, that after insemination, fail to return to oestrous within 24hours days of Ai but are diagnosed as non-pregnant
The pregnant cause of symptoms is due to embryonic loss
what are some of prevention strategies for declining fertility
Genetics
Nutrition
Heat Detection
Health and welfare
what are the effects of Heat stress
Thermoneutral zone for cattle b/w 23 to 27degrees
Internal core temperature will rise and have an adverse effect on physiological processes, rumen function and a detrimental effect on oocyte quality and embryo viability
Heat load = internal metabolic heat + environment heat - heat loss
head loss occurs by;
conduction, convection, radiation and evaporation
Once air temperature exceeds the cows body temperature heat loss can only occur by
Evaporation
what are the consequences of heat stress
Reduced fertility particularly when heat stress occurs -1 to 6 days post service and in weeks leading up to service (weeks -1 to -5)
Reduction in the duration and intensity of oestrus
Reduction in semen quality in bulls
Reduction feed intake and ability to digest nutrients
Reduced milk production and milk quality
How to decrease consequences of heat stress
Cooling cows
optimise nutrition
increase effort into heat detection
Use AI to reduce infertility associated with heat stressed bulls
Breed more heifers during hot months (less prone to heat stress) to help compensate for lower pregnancy rates in mature cows as pregnancy rates will be greater in heifers
Genetic improvement
What is the effect of nutrition
Undernutrition delays the onset of puberty in heifers
Early onset of puberty can increase % of heifers cycling at the start of mating and increase conception rate at 1st oestrous of mating
Reproductive consequences of severe negative energy balance
Increase days to first ovulation (= duration of postpartum anoestrous)
Decrease secretion of LH
Decrease concentration Of IGF-1
Delayed uterine involution
Decreased conception rates
Increased embryonic loss
Potential for later calving and shorter calving to breeding intervals in following year
How does dietary protein affect fertility
Rapid change to high rumen degradable nitrogen diet = higher plasma concentration of blood urea nitrogen = changes to uterine pH and increases in intrauterine urea concentration = negatively affects fertility
what are the potential affects of vitamins and minerals
Decreased activity of rumen microorgansims and decreased digestibility
Altered enzymatic action, which laters energy or protein metabolism or hormone synthesis
Reduced integrity of reproductive cells anti-oxidant effects
