Sheep Nutrition for ReproductionPart I: Nutrition as a Major Environmental Factor Affecting

the Reproductive Axis

J. Wamatu

EIAR-DBARC-ICARDA-ILRI (LIVES)-FAO Training on Reproduction in Sheep and Goat, Debre Berhan, Ethiopia, 13-15 October 2014

Jane Wamatu

Outline

Factors that influence feeding of an ewe Feeding regimes/stagesTypical nutritional disorders

Ewe Nutritional Needs are not Static

The objective of feeding the ewe is to produce lambs, whether these are for breeding, for fattening or for slaughter

Feeding an ewe depends on many factorso Ageo Weighto Body conditiono Stage and level of productiono Environmental factors and level of exercise

Ewe Nutritional Needs are not Static

The standard of nutrition for ewes can be classified into 3 main stages:

o Pre-breeding to breedingo Early gestation to mid gestationo Late gestation and early lactation

Pre-Breeding → BreedingThe level of nutrition in the weeks before mating and during the mating period is important in determining the number of lambs conceived

Aim Replenish body reserves lost after last pregnancy Minimize number of ewes which fail to show oestrus To ensure that a sufficient number of eggs are shed at ovulation and subsequently fertilized To maximize number of fertilized eggs which are implanted and develop into viable embryos and foetuses

Pre-Breeding → BreedingHow to achieve the aim Ewes are in appropriate body condition

at the beginning of the mating period The good body condition is maintained

for the first weeks of pregnancy when risk of embryonic mortality is greatest

Body condition scoring: Score 0 (emaciated) to Score 5 (very fat)

Pre-Breeding → BreedingHow to achieve the aim The better the body condition at mating, the higher is the ovulation

rate and the higher is the lambing percentage The number of eggs shed by ewes with a particular condition score

at mating depends largely on the breed Ewe lambs should be atleast 60 % of their expected mature

liveweight Ewes that are already in good body condition (3.5) do not generally

respond to flushing (current nutrition).

NB: In some breeds, ovulation does not respond to body condition

Pre-Breeding → Breeding The length of time required to prepare ewes for mating depends on

their initial condition and the quality of feed available (4 - >6 weeks) Attention should be paid to energy and protein intake Suggested quantities of energy are generally related to maintenance

of liveweight and specific rates of liveweight gain, rather than to changes in condition score

Approx. 1kg change in weight is equal to approx. 0.1 units in body condition

Pre-Breeding → BreedingSummary Ewes should be in proper body condition

by mating time – BCS 3.5 Lean ewes should be managed

separately for at least 6 weeks to ensure uniformity of flock condition at mating

Loss of weight or condition should be avoided during the mating period

Early → mid-gestationNutrition during pregnancy determines the number of lambs subsequently born alive with a birth weight which will ensure that they survive and are capable of growing well Placental development occurs first 30 to 90

days of pregnancy Placental size or weight affects nutrient

transfer between the ewe and her fetuses

Early → mid-gestationUnderdeveloped placentas result in low birth weights,

regardless of late gestation nutrition.21 days of severe underfeeding or 80 days of moderate

underfeeding can affect placental development.Do not overfeed or underfeed; aim for a body condition

score of 3 to 3.5

Nutrient requirements are only slightly above maintenance

Early → mid-gestation15-30% of eggs shed at ovulation fail to result in the birth of

the lambThe main reason is failure of embryos to implant in the first

month after matingSevere undernourishment or high levels of post-mating

nutrition may result in impaired embryo survivalEwes should maintain a constant weight during the month

following matingAvoid abrupt change in the level of nutrition

Early → mid-gestation It is important to maintain their weights over this period.

Prevent losses exceeding the equivalent of 0.75 units in condition score.

Protein requirements for growth are low, but should not fall below 10g CP per MJ of ME to ensure

Only small losses inbody condition should be allowed during this period

Even short periods of severe undernutrition must be avoided

Late gestation → early lactationNutrition after lambing has a major effect on milk production and hence on lamb growth rate

Proper feeding and management during late gestation are crucial to a successful lambing

During the last 4 to 6 weeks of gestation, 70 percent of fetal growth is occurring

Late gestation → early lactation The mammary system is developing. High output of protein in milk and colostrum production Additional undegraded dietary protein is required Protein sources relatively resistant to degradation in the rumen

are recommended The recommended rate of inclusion is influenced by their

degradability, potential production (milk) of the ewe and her ME intake

Late gestation → early lactation High output of protein in milk (colostrum production The ewe’s rumen capacity is decreasing. Nutrient requirement increase rapidly towards the end of

pregnancy and nutrient supply must be increased Lean ewes should be given preferential feeding For economy of feed use, ewes should be grouped according to

nutrient requirement e.g lambing date and age

Nutritional disordersHypomagnesaemia This refers to magnesium deficiency Occurs in the first 4-6 weeks of lactation at the peak of milk

production when there is a large demand of the very limited reserves of magnesium in the body

First sign of an outbreak is a dead ewe which appeared normal only a few hours earlier

An adequate intake of magnesium is ensured by including 6g of magnesium oxide evenly distributed in the daily ration of concentrate offered in early lactation

Nutritional disordersHypocalcaemia Also referred to as lambing sickness Occurs just before, during or just after lambing Ewes show uncoordinated movements, muscular tremors and

rapid breathing Ewes fall with the head and hind legs extended, rapidly develop

paralysis and go into a coma Treatment with calcium borogluconate solution generally results

in a rapid recovery

Nutritional disordersMuscular dystrophy Also known as white muscle disease Arises from deficiency in Vitamin E/selenium in the diet Symptoms are stiffness in young, rapidly growing lambs around

3-4 weeks Symptoms can also occur immediately after weaning at 4-6

weeks of age Main factors influencing amounts of vitamin E/selenium occurring

naturally in feeds are the type of soil on which the crop is grown, weather conditions during growing season and storage (high moisture storage leads to deterioration in their vitamin E status)

Nutritional disorders

HypomagnesaemiaFirst 4-6 weeks of lactation at the

peak of milk productionHypocalcaemiaLambing sicknessUncoordinated movementsMuscular dystrophyWhite muscle diseaseDeficiency in Vitamin E/seleniunStiffness in young, rapidly growing

lambs around 3-4 weeks.