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Repro 13-14
Male effect and seasonality
| Question | Answer |
|---|---|
| The male effect | where the presence of a male induces reproductive behaviours and physiological changes in females |
| Male effect importance | eliminates intensive need for hormones in reproductive management |
| The male effect (mechanisms) | Physiological mechanisms (pheromones) Behavioural mechanisms (visual and auditory cues) |
| Pheremones in the male effect | chemical signals released by males that can trigger oestrus in females primer pheromones or signalling pheromones |
| Behavioural mechanisms in the male effect | visual and auditory cues sight and sound of males can influence female reproductive cycles male-female interactions |
| Applications of the male effect | synchronise breeding in sheep/goats stimulate puberty in gilts and ewe lambs enhance fertility in pigs (boar effect) |
| Ram effect or Buck effect | presence of a novel male induces rapid increase in the frequency of GnRH/LH pulses and ovulation improved breeding efficiency and lambing/kidding rates |
| Boar effect | decreases age at puberty and induces behaviour oestrus |
| Challenges of the Male effect | seasonality animal welfare variation in male stimulus value environmental constraints |
| Seasonal breeding (challenges) | sheep/goats: effectiveness of male effect highly seasonal need to ensure male is introduced during breeding cycle time |
| Timing of introduction (challenges) | timing is important to maximise male effect |
| Environmental factors (challenges) | Adequate housing and space are necessary extreme weather conditions can impact behaviour |
| Stress and aggression | introduction of males can sometimes lead to increased stress or aggressive behaviours |
| Individual differences | not all males or females may respond to the male effect eg sexual activity, age and experience of males |
| Genetic factors | Genetic differences can influence the effectiveness of the male effect -requiring selective breeding to optimise results |
| How to maximise the boar effect | expose gilts at maximum stimulation to puberty stimulation ensure boar is of high stimulus value put boar and gilts together so stimulus transfer maximised |
| Female-female effect | number of females on heat at the same time can increase cycling of other cows |
| Environmental influences on reproduction | photoperiod nutrition temperature social cues (pheromones, interactions) |
| Short day breeders | sheep, goats respond to increasing night length melatonin increase stimulates GnRH and reproductive activity begins |
| Long day breeders | horses respond to increasing daylight short nights reduce melatonin and inhibitory influence on hypothalamus is removed |
| Sheep seasonal patterns | strong seasonality breed in autumn and lamb in spring when pasture is optimal |
| Goat seasonal pattern | similar to sheep |
| Horse seasonal pattern | breed in spring/summer foal the following spring |
| Cattle seasonal pattern | not strongly seasonal but puberty and postpartum periods show season-related differences |
| Pig seasonal patterns | piglets produced all year round - reduced fertility in summer and autumn |
| seasonal infertility in pigs | reduction in the proportion of gilts reaching puberty delay in time they reach puberty poor oestrus expression extended weaning high anoestrus rates |
| Manipulating seasonality | hormonal (melatonin/progesterone) photoperiod manipulation male effect teaser rams shed management |
| Oestrus detection procedures | ensure full physical contact between gilt/sow and boar increase frequency of boar contact one boar per 8-10 gilts/sows |
| Insemination practices | inseminate sows when they are first detected in heat store semen around 17*C in dark place |
| Hormonal methods to manipulate seasonality | kisspeptin GnRH Melatonin |
| Kisspeptin (seasonality manipulation) | induces ovulation in sheep |
| GnRH (seasonality manipulation) | female needs to be close to a spontaneous cycle |
| Melatonin (seasonality manipulation) | can only be used in short day breeders |
| Teaser rams | most effective when animals are not cycling normally 14 day tease recommended sheep become more resistant to teasing as they become more seasonal |
| Why breed in the non-breeding season? | better prices for lambs born in march/April mixed enterprises |
Created by:
sakelleher29
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