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ANSC*3040- Reproduction > Applied Reproductive Physiology in ruminants > Flashcards

Applied Reproductive Physiology in ruminants Flashcards

1
Q

Costs of Rearing replacement heifers

A

second largest expense in a dairy operation 20%
future of the diary operation
paradox: investment in feed, labour and capital for 22 to 24 months without receiving any realized benefits

on average costs 3.70 a day to feed

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2
Q

Goals of a Reproductive Program for Heifers

A
  • decrease age at first calving with adequate body size and without compromising mammary development and future lactation performance
  • has to be economically sound
  • timed AI programs for heifers are economically attractive when estrous detection rate is ~70%
  • achieve puberty and sexual maturity early
  • achieve adequate BW, height, and frame size at calving
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3
Q

How to measure heifers growth

A

measure a representative subgroup of heifers in different age groups on the same day
plot weight or height by age- calculate parameters for the line
slope =ADG and AHG

longitudinal- measure each heifer or cohorts of heifers and follow at specific time points. analyst grouped data

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4
Q

Disadvantages of underfeeding heifers

A

heifers will reach puberty and calve later in life

  • increase rearing costs
  • increased farm inventory of heifers
  • delayed milk income
  • lifetime milk production is lower

lighter heifers produce less milk during first lactation

smaller frame heifers have increase risk for dystocia and limited capacity to compete for food and to ingest nutrients

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5
Q

reasons for slower growth rates

A

poor management
feeding forage of poor quality and quantity
- seasonal variation in forage
- stored forage

underfeeding grain supplements
inadequate bunk space

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6
Q

Prepubertal anestrus

A

not a major problem, unless the feeding program is poor or heifers are being inseminated before

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7
Q

Reproductive Programs for Heifers

A

importance of reproductive efficiency in heifers

  • reduced rearing costs
  • reduces variability in age at first calving

programs:
- natural breedings- not rec
- detection of spontaneous estrus
- detection of spontaneous and induced esters
- timed AI programs

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8
Q

Persistance of milk

A

more horizontal curve= more persistent milk

more vertical curve= less persistent milk

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9
Q

The Importance of Reproductive Efficiency to the Economy of the Dairy Farm

A

replacement heifers: reduces rearing costs, reduces variability in age at first calving

lactating cows:
- improves milk production - decreases the average days in milk of the herd - faster transition to a more productive stage in the following lactation

increases the number of replacement heifers

  • allows greater genetic selection intensity
  • allows selling heifers and cows for milk production

facilitates adequate culling policies

  • culling of problem cows
  • younger herd: better fertility, healthy, and genetic merit
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10
Q

To have good reproductive efficiency in a dairy herd, cows need… to be inseminated in a optimal time postpartum…

A

how to evaluate

  • voluntary waiting period
  • insemination rate
  • DIM at 1st AI

risk factors

  • an ovulation
  • low detection of estrus
  • management inconsistencies

solutions

  • reduction of risk factors
  • heat detection aids
  • timed AI
  • systematic breeding program
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11
Q

To have good reproductive efficiency in a dairy herd, cows need… to become pregnant in a optimal time post partum and maintain pregnancy

A

how to evaluate

  • P/AI
  • pregnancy losses

risk factors

  • diseases
  • low BCS
  • anovulation
  • nutritional deficiencies
  • genetics
  • heat stress

solutions

  • reduction of risk factors
  • genetic selection
  • fertility treatments
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12
Q

Optimal insemination window

A

10 to 12 hours from estrus onset

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13
Q

Risk factors for low insemination rate- poor estrus detection

A
  • high milk yield –> more blood flow to digestive tract so faster hormone metabolism
  • bad flooring
  • lameness
  • low BCS
  • heat stress
  • inadequate training of employees
  • inconsistent mangament
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14
Q

risk factors for low insemination rate- an ovulation

A

time to resume estrous cyclicality postpartum varies among cows

no estrous activity

directly related to energy balance postpartum
~20% of the cows reach the end of the VWP as anovular cows at 60DIM in Ontario dairy herds

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15
Q

Synchronization of the Estrous Cycle

A

prostaglandin injection to induce luteolysis
GnRH injection to induce ovulation
progesterone implant to prevent ovulation

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16
Q

Timed Artificial Insemination

A

objectives

  • inseminate all cows in a prescheduled time with no need for estrous detection
  • maximize insemination rate (100%) and consequently pregnancy rate
17
Q

Ovsynch

A

GnRH– 7 days –> Pgf2alpha– 56 hours–> GnRH –16 hours–> AI
best results when the protocol is initiated in early diestrus (days 5 to 9 at GnRH 1)

18
Q

Presynchronization

A

objective

- target cows to be in early diestrus at initiation of ovsynch

19
Q

weekly based programs

A 
day 1: PGF2alpha
day 14: PGF2 alpha
day 26: GnRH
day 33: PGF2alpha
day 35 pm: GnRH
day 36 am: timed AI
20
Q

Pregnancy diagnosis

A

28 to 34 days after AI
result = pregnant –> no action needed, recheck in 30 days

result non-pregnant–>
Actions: re=synchronization and timed AI
reinsemination at estrus
cull/dont breed

21
Q

Considerations for Implementing timed AI programs

A

estrous detection rate in farm
- low EDR makes time AI more attractive

high EDR (>60%): impact of time AI become less evident - allows flexibility, but it won’t necessarily improve performance

timed AI might facilitate labour, but it also creates additional work and requires compliance
best response to timed AI
- management of first postpartum AI (all cows are eligible)

22
Q

Fundamentals in Reproductive Management of Dairy Cows

A

work with groups of cows: pro-active management
focus is to increase the rate at which cows become pregnant past the voluntary waiting period

uses systemic breeding programs to minimize the missed”opportunities”

objective

  • increase pregnancy rate
  • reduce the interval and minimize the variability between the end of the voluntary waiting period and pregnancy in a consistent manner
23
Q

21 day pregnancy rate

A

has been stuck around 15-17% for many years… lots of room for improvement

24
Q

21-day insemination rate

A

this is what improves 21-day pregnancy rate currently 50%

25
Q

pregnancy per AI

A

hasn’t changed in a long time… currently 35-38%

research is being done as to why it isn’t improving

26
Q

embryo survival depends on

A 
genetics of the cow
genetics of the embryo 
low concentration of circulating steroids and IGF1
anovulation at initiation of synchronization 
heat stress and hyperthermia
extensive loss of BCS
low BCS at AI
clinical diseases before and after AI

heat stress reduces pregnancy per AI
heat stress impairs oocyte quality and early embryonic development

27
Q

incidence of clinical disease before first breeding (postpartum)

A

21% undiagnosed with uterine disease
25% diagnosed with non-uterine disease
40% diagnosed with at least one clinical disease

28
Q

Clinical diseases postpartum

A

prevalent in dairy herds
long-lasting effects on production and reproduction traits

important pre-disposition factor for early and late pregnancy losses

29
Q

clinical diseases postpartum Negative Effects on:

A
  • oocyte quality
  • fertilization of oocytes
  • development to morula
  • elongation of the conceptus
  • survival of the developing fetus
30
Q

Low BCS effect on pregnancy

A

cows with excessive loss of BCS (1 unit or more) during the early postpartum period have reduced pregnancy per AI
cows with low BCS at embryo transfer have reduced pregnancy per embryo transfer

31
Q

Major Goal in Cow-calf operations

A

maximize quantity and quality of calves born each year
reproductive efficiency is key
ideally 1 calf per cow per year

32
Q

Factors affecting reproductive efficiency in beef cows

A 
postpartum anestrus
suckling stimulus/presence of the calf
age
genetics
nutrition
plane of nutrition/body composition
reproductive management 
animal handling and semen quality 
number and quality of bulls
33
Q

factors affecting reproductive efficiency in beef heifers

A 
prepubertal anestrous
body weight 
age
genetics
nutrition 
plane of nutirtion/body composition 
reproductive management 
animal handling and semen quality 
number and quality of bulls
34
Q

Breeding Season

A

pre-established period of the year in which cows and heifers should become pregnant

  • calving occur within a short window of time
  • facilitates management
  • optimizes production efficiency

it should consider local environment and market conditions

  • weather
  • facilities and labour
  • availability and price of feed
  • demand for and market price of the final product

it should be short (ideally less than 3 months)

ANSC*3040- Reproduction (24 decks)

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