The University of Western Australia

Cesar Rosales Nieto School of Animal Biology and The UWA Institute of Agriculture, Faculty of Science

Cesar completed a Bachelor degree Plant and Animal Science with first class Honours at the University of San Luis Potosi in his home country of Mexico. He then worked at Mexico’s National Institute of Forest, Agricultural and Livestock Research as a researcher. In 2004 he went to the United States and completed a Master degree in Animal Science, with an emphasis on the physiology of reproduction, at Texas A&M University. In 2009, a scholarship from the Mexican National Council for Science and Technology enabled Cesar to come to UWA to undertake his PhD, examining the effect s of muscle and fat accumulation on the reproductive performance of female sheep. Cesar plans to submit his thesis later this year and will return to Mexico to help advance agriculture in in his home country with the knowledge gained at UWA.

THE UWA INSTITUTE OF AGRICULTURE Postgraduate Showcase 2013: Frontiers in Agriculture

Advancing puberty in female sheep: its all about muscle and fat

Cesar Rosales Nieto Graeme Martin

Andrew Thompson

Team Supervisors

Acknowledgements:

Mate ewes as lambs

Economics (more lambs on the ground)

Increase lambs weaned

Increase in lifetime performance

Increased rate of genetic gain

Reproductive efficiency

The Australian sheep industry

Puberty

Internal factors External factors

Gonadotrophins LH – Luteinizing Hormone

FSH – Follicle-Stimulating Hormone

Ovulation Egg

Ovary

Physiological sexual maturity has

been reached

Liveweight (50 – 70%)

Age is a secondary factor

(-) (+)

Fat tissue (Body Condition / Live weight)

Leptin concentration

(-)

(+)

Leptin concentration

Puberty/Fertility

Reproduction Fat

(-) (+)

Rate of muscle accumulation

(-)

(+)

Fecundity Follistatin

Reproduction Muscle

Hypothesis

Puberty ‘switch’

Leptin Adipose tissue

Body Composition

Ovulatory signal

Ovulation

Higher values for growth and muscle and fat accumulation are also more able to successfully reproduce at younger ages

This reproductive success is positive related to circulating

concentration of follistatin and leptin

Follistatin Muscle tissue accumulation

The “Adipose theory”

2009 - 2011

Experiment

Medina (n = 136)

Pingelly (n = 190)

Katanning (n = 514) Sire: Wide range in genetic values (ASBV) for growth,

muscle and fat

Live weight was recorded (LWC) Fat and muscle scan at post-weaning

Depth of Eye Muscle (EMD)

Depth of Fat (FAT)

Genetic value for weight (PWT)

Genetic value for muscle (PEMD)

Genetic value for fat (PFAT)

Material and Methods Animals and treatments

Puberty Period (5 to 8 months old)

Vasectomized rams

Harness with a crayon

Fertility Period (8 to 10 months old)

Entire Rams

Pregnancy scan (60 days)

Fertility rate

Material and Methods Animals and treatments

• Mixed Model for age at first oestrus, puberty and fertility.

• Covariates: EMD, FAT, PEMD, PFAT, PWT

• Fixed Effects: BTRT (Birth type - Rear type) and Dam age

• Random effect: Ewe lamb sire

Material and Methods Data analyses

20

25

30

35

40

45

50

Live weight (Kg)

Results

Puberty Period Fertility Period

LWC

≥ 200; 75%

≤ 50; 35%

Experiment

Age at first oestrus (Days)

200

210

220

230

240

0 1 2 3 4 5 6 7 8 9 PWT (Kg)

40

60

80

100

0 1 2 3 4 5 6 7 8 9

Puberty (%)

PWT (Kg)

2 3 4 5 6 7

FAT 40

60

80

100

15 18 21 24 27 30 33

EMD

Muscle accumulation (EMD; mm)

Pube

rty

(%)

Fat accumulation (FAT; mm) Results Puberty and muscle and fat accumulation

0

20

40

60

80

100

30 35 40 45 50 55

Fertility (%)

Live weight at start of Mating (Kg)

0

20

40

60

80

100

15 18 21 24 27 30 33

EMD FAT

2 3 4 5 6 7 Fat accumulation (FAT; mm)

Muscle accumulation (EMD; mm)

Fert

ility

(%)

20

40

60

80

100

1 3 5 7 9

Follistatin

Follistatin (ng/mL)

Fert

ility

(%)

0.8 1.2 1.6 2 2.4 2.8 3.2

Leptin

Leptin (ng/mL) Results Fertility and hormonal control

1

1.4

1.8

2.2

Leptin

Leptin (ng/mL)

2

3

4

5

15 20 25 30 35 Follistatin

Total follistatin (ng/mL)

Muscle accumulation (mm)

Conclusion

Puberty ‘switch’

Leptin Adipose tissue

Body Composition

Ovulatory signal

Ovulation

Muscle tissue Follistatin X Intramuscular

fat

Live weight Growth