AnSci' 226Dairy Cattle Breeding

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AnSci. 226/Dairy Cattle Breeding Selection

• Reproduction
• The Estrous Cycle and Estrus

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The Estrous Cycle

• The period of time from the beginning of one
  estrus period (heat) to the beginning of the next
  estrus period (heat). The estrus cycle length
  varies from 18-24 days, with the average about 21
  days for cows and about 19 days for heifers.

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Phases of the Estrus Cycle

• Estrus
• Metestrus
• Diestrus
• Proestrus

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Estrus (Heat)

• Average length of Estrus is 12 to 18 hours.
• Ovulation normally occurs 10 to 12 hours after
  the end of estrus.

• Estrus is the period of time the female will
  stand to be ridden by another cow or is receptive
  to be mated by the bull.

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Ovulation occures 10 12 hours after the end of
estrus
Metestrus
Estrus
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Metestrus

• Metestrus is the period immediately following
  estrus and ovulation.
• Characterized by the formation of the Corpus
  Luteum.

• Ovulated eggs are picked up by the oviducts and
  transported to the uterine horns.
• 2-4 days after Estrus lasting for 3 days.

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Diestrus

• Diestrus is the most lengthy period of the
  estrous cycle which is the period of corpus
  luteum function.
• Days 5 to 16-17
• The corpus luteum produces large amount of
  Progesterone that will affect mammary development
  and uterine growth.

• The corpus luteum continues throughout pregnancy.
• If pregnancy does not occur the corpus luteum
  will degenerate after approximately 15 days.

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Proestrus

• Days 17 to 21
• Cows may show increased excitability but not to
  the stage of actual mating.

• Proestrus is the period just prior to estrus
  (heat).Regression of CL.
• Estrogens secreted by the ovaries (Rapid Follicle
  Growth) which stimulate blood supply to the
  genital tract causing swelling and reddening of
  the vulva.

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What are the 4 Stagesof the Estrous Cycle?
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Detection of Estrus (Heat) in Dairy Cattle

• Primary Sign of Estrus
• Stands immobile when mounted.

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Hormonal Activity of estrous
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Secondary Signs of Estrus

• Behavioral
• Bellowing
• Increased Activity
• Walking the fence line
• Charging
• Butting
• Licking

• Sniffing
• Flehmen posture (inverted nostrils)
• Circling
• Chin-resting
• Mounting

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Secondary Signs of Estrus

• Physical Signs of Estrus
• Manure on flanks
• Roughened tailhead
• Loss of hair on tailhead
• Abrasions on tailhead

• Red vulva
• Swollen vulva
• Clear mucus discharge from vulva

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Secondary Signs of Estrus

• Miscellaneous Signs of Estrus
• Depressed appetite
• Depressed milk production

• Frequent Urination
• Metestrus bleeding 35-45 hours after estrus too
  late to breed

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What are the signs?

• Primary sign of heat?
• Secondary signs behavioral?
• Secondary signs physical?
• Miscellaneous signs?

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Factors Influencing the Detection of Estrus
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Identification

• Accurate and complete record keeping is
  essential.
• Proper identification is necessary.
• Legible ear tags
• Freeze brands
• Sufficient outdoor lighting.

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Time of Visual Observation

• Should observe cows 2 to 3 times per day for
  approximately 30 minutes.
• Try to perform observations during the quiet
  times of the day cows laying down, draining
• Warm time of day during the winter
• Cool time of day during the summer

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Time of Visual Observation

• Detection Aids
• Radio Transmitters
• Leg chips, ear, hock
• Activity levels, held up
• Chalk mark on tailhead
• Color usage
• Gomer bulls wearing chin-ball markers
• Tailhead patches

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Time of Visual Observation

• Housing Conditions
• Provide shaded areas in the summer.
• Provide protection from winds in the winter.
• Provide good footing surfaces.

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Time of Visual Observation

• Miscellaneous Factors
• Meet all nutrient requirements for proper
  nutrition. Extra energy in winter.
• Veterinary herd health checks.
• Records kept

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Reproductive Management of Dairy Cattle
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Important Records for Reproductive Management

• Average Days Open Average number of days from
  the most recent calving to conception.
• Calving Interval Are determined for each cow
  using the last calving date and projecting from
  that date the due date.

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Important Records for Reproductive Management

• Days to First Breeding Is the average number of
  days from the most recent calving to first
  service for all cows in the breeding herd.
• Number of Breedings Per Conception is simply
  the number of breedings required to achieve
  conception.

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Option Interval or Voluntary Waiting Period

• Option Interval or Voluntary Waiting Period is
  the number of days from the last calving to the
  time in which the herd manager decides to begin
  rebreeding.

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Option Interval or Voluntary Waiting Period

• This may vary depending upon individual cows
  production.
• High producing cows Bred at first estrus 60 day
  postpartum 13 month calving interval may be
  optimal.
• Medium/Low producing cows Breed at first estrus
  40 days postpartum 12 month calving interval
  may be optimal.

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Option Interval or Voluntary Waiting Period

• Two factors seem to play a role in the cows
  calving interval.
• High producers tend to have silent heat more
  often than low producers.
• Dairy farmers may give high producers a longer
  wait period before being bred back.

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What is an waiting period?

• Voluntary?

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The Economic Importance Reproductive Management

• It is estimated that the dairy producer loses
  4.00 to 10.00 per day in net income when
  calving interval exceed 12.5 months. 20 CWT
• To maintain a 12.5 month calving interval, cows
  must be pregnant by 100 days after calving.

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The Economic Importance Reproductive Management

• Breeding should start at 40 50 days after
  parturition. If necessary this will allow for
  three breeding opportunities and still maintain
  the 12.5 month calving interval.

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Photoperiod

• Seasonal drop in daylight to darkness drops
  Fall breeders Sheep
• Can use artificial light to cause a play on
  pineal gland to produce melatonin
• Goats late June to early April
• Breed and/or select for more fertility
• Natural selection and environment improvement can
  bring more cycles

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