Criteria for weaning
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Criteria for weaning. Dry feed consumption Size – ~ 150 lb General health Age – usually 6-8 wk. Heifer-raising industry. ~ __ million cows in US Average culling rate ___% Replacement heifers rank ___ in costs of milk production costs of the dairy enterprise. OPEN HEIFERS.

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Criteria for weaning l.jpg
Criteria for weaning

  • Dry feed consumption

  • Size – ~ 150 lb

  • General health

  • Age – usually 6-8 wk


Heifer raising industry l.jpg
Heifer-raising industry

  • ~ __ million cows in US

  • Average culling rate ___%

  • Replacement heifers rank ___ in costs of milk production costs of the dairy enterprise


Open heifers l.jpg
OPEN HEIFERS

Open Heifer - Young female that has not been bred

After weaning, calf should gain about

1.75 lb per day

Reach puberty about 12 mos

Heifers should be grouped by size and age

Holstein heifers should weigh 800 – 850 lb by 15 mos of age


Normal heart girth measurement and weight of calves and heifers during growing period l.jpg
Normal Heart-Girth Measurement and Weight of Calves and Heifers During Growing Period

Holstein

Ayrshire

Guernsey

Jersey

Age in

months

Inches

Pounds

Inches

Pounds

Inches

Pounds

Inches

Pounds

At Birth

31

29.5

72

66

24.5

56

96

29

1

33.5

118

32

90

72

98

31.5

29.5

3

40.25

213

38.75

179

164

35.25

138

38

47

335

45.5

291

44.25

265

41.5

5

228

52.5

455

51.25

408

49.75

362

47.25

325

7

57

559

55

485

9

53.75

448

51.75

409

11

60.5

658

58

563

56.75

521

55

481

13

63.25

740

60.75

630

59.25

587

57.25

540

15

65.25

805

63

703

61.75

640

59

585

17

67.25

874

65.25

63.5

696

758

60.5

635

19

69.25

66.5

65.5

946

813

752

62.5

687

21

816

64

740

71.5

1025

68.5

885

67.5


Open heifers5 l.jpg
OPEN HEIFERS Heifers During Growing Period

Housing

Normally require protection from wind,

wet weather, but adequate ventilation

Health

Vaccinations at 4 to 8 mos of age

Stomach magnet

Ionophores/Coccidiostats


Heifers l.jpg
HEIFERS Heifers During Growing Period

Breeding

Estrous cycle -- 18-22 (21) d in length

Estrus -- 16 h in length

Restless, more alert

Red and swollen vulva

Increased mobility, tries to mount other cows

Stands to be mounted by other cows

Ovulation occurs 12 - 18 h after

end of estrus

Pregnancy checked >35 d after breeding


Goals for heifer program l.jpg
Goals for heifer program Heifers During Growing Period

Body weight after calving: 1200-1250 lb

Age at first calving: 22-24 mo

Height at calving: 55-57 in

Body condition score at calving: ~ 3.5

Average gain for heifer: 1.8 - 2.0 lb/day


Slide8 l.jpg

Development of the mammary gland Heifers During Growing Period

10 mo.

3 mo.

  • The parenchymal tissue formed before puberty is the foundation for later growth.

  • Milk production is partly dictated by the number of parenchymal cells at puberty.


Mammary glands l.jpg
Mammary glands Heifers During Growing Period

  • Number and location

    • Inguinal region--cows, goats, sheep, horses

    • Abdominal – sows

    • + correlation between # of glands, offspring


Lifetime of the mammary gland l.jpg
Lifetime of the mammary gland Heifers During Growing Period

  • Periods of growth and regression related to reproductive cycle

  • Mammogenesis

  • Lactogenesis

  • Lactation

  • Involution


Mg structure external l.jpg
MG Structure - external Heifers During Growing Period

  • Number of glands, teats

    • Cow – four glands, with four teats

    • Sheep, goats – two glands, with two teats

    • Horse – four glands, with two teats

  • Udder weight (cow) 30 – 80 lbs

  • Skin (protection, little support)

  • Teats –

    • exit for secretion

    • 25 – 50% cows have supernumerary teats


Mg structure internal l.jpg
MG structure - internal Heifers During Growing Period

  • Suspensory ligaments

  • Blood flow

  • Mammary tissue insensitive to heat or touch


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Structures of the Mammary Gland Heifers During Growing Period


Lactation l.jpg
Lactation Heifers During Growing Period

  • Success determined by

    • Maintenance of cell #’s

    • Secretory activity

    • Milk removal

  • ~ 305 d or longer in dairy cows


Milk production l.jpg
Milk production Heifers During Growing Period

  • Increases to peak ~ 8 weeks after calving

  • ~60% of milk produced by 2 rear quarters of dairy cow

  • Increased by administration of growth hormone, or bST


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