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Sheep are polyestrous - Leaving Cert Agricultural Science - Question 5 - 2015
Question 5
Sheep are polyestrous. What does the term polyestrous mean? What is the length of the oestrous cycle in sheep? Explain the connection between day length and the bree... show full transcript
Worked Solution & Example Answer:Sheep are polyestrous - Leaving Cert Agricultural Science - Question 5 - 2015
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Explain the connection between day length and the breeding season in sheep.
Answer
The breeding season in sheep is influenced by day length; shorter days are a signal for breeding. Sheep are considered short-day breeders, meaning that as the days become shorter, related hormonal changes occur, stimulating the onset of estrus or heat cycles due to increased melatonin secretion from the pineal gland.
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Describe the key steps involved in 'breeding out of season' to produce lambs for the early spring market.
Answer
The key steps include: 1. Inserting progesterone-soaked sponges into the ewes' vaginas for a period of 12 to 16 days. 2. Removing the sponges and injecting ewes with PMSG (Pregnant Mare Serum Gonadotropin) to stimulate estrus. 3. Introducing a ram to the ewes 1-2 days later, ensuring a ewe-to-ram ratio of approximately 1:10.
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Outline four reasons for culling ewes.
Answer
- Ewes that are barren or fail to conceive after breeding attempts. 2. Ewes with health issues such as broken mouths or teeth that impair their ability to feed. 3. Ewes with poor body condition scores or lambing problems indicating ongoing reproductive issues. 4. Older ewes that have reduced productivity or poor lambing rates due to age-related factors.