Trimersters and Nutrition Around Lambing Time

Lambing – Ewe Trimesters and Nutrition

Adequate ewe nutrition during the last 6 weeks of pregnancy, when 75% of foetal growth occurs, is essential to ensure appropriate lamb birthweight.

Pregnancy is divided into 3 stages (trimesters)

1.       First Trimester ( day 1 – 45 ) – Implantation

2.       Second Trimester ( day 45 – 90 ) – Placental Development

3.       Third Trimester ( day 90 – 143 ) – Foetal Growth & Development

1) Implantation / First Trimester:  There is a reasonably low energy demand put on by pregnancy, as the very little energy is needed for the developing foetus. Dietary energy supply around the time of implantation is likely to be adequate because autumn grass is still available.

2) Placental Development / Second Trimester: During this period under nutrition has been show to affect birth weight and placental development; however the impact is usually fairly low, unless paired with adverse weather or grazing patterns for at least 14 days. Severe fluke infestation of the ewe can exert an adverse effect on placental development.
Reduced lamb birthweight can occur when placental development has been limited by competition within the uterine horn, for example when 3 embryos are implanted and undergo early foetal development but one foetus failed to develop further and was resorbed, leaving the other developing foetus in the same horn much smaller than normal and unable to compensate. This situation often results in twins being born of contrasting weights.

3) Foetal Growth & Development / Third Trimester: Studies have found significantly higher mortality rates in lambs from underfed ewes during this stage. The effects are greater for triplet lambs, lesser for twins and singletons are relatively unaffected.

Vaccination Programme

Ewes need to be vaccinated against the clostridial diseases 4 weeks before lambing. It is advisable to vaccinate the flock as two groups, with the later lambing ewes vaccinated one week to 10 days later than those ewes lambing during the first week. The injection is administered subcutaneously. The fleece must be dry when injection is given; if wet, abscess formation is quite probable.