Applied Animal Nutrition-I

EXTRA-UTERINE GROWTH DURING PREGNANCY

• The live weight gains made by pregnant animals are often considerably greater than can be accounted for by the products of conception alone.
• For example, a litter of 10 piglets and its associated membranes may weigh 18 kg. at birth, but sows frequently gain over 50 kg during gestation.
• The difference represents the growth of the mother herself, and sows may in their own tissues deposit 3 – 4 times as much protein and 5 times as much calcium as is deposited in the products on conception.
• This pregnancy anabolism, as it is sometimes called, is obviously necessary in immature animals which are still growing, but it occurs also in older animals.
• Frequently much of the weight gained during pregnancy is lost in the ensuring lactation.
• Pregnancy anabolism is often encouraged in pigs on the grounds that it increases the birth weight of the young and that the reserves accumulated allow the sow to milk better and hence promote faster growth in the piglets.
• In dairy cows a high plane of nutrition in the dry period preceding parturition is claimed to promote the growth of mammary tissue and to increase body reserves, and thus to raise milk yield in the ensuring lactation.
• This is the theory behind the practice of ‘steaming up’ cows by giving them increasing quantities of concentrates before calving.
• However, if the cow is not unduly thin at the end of the previous lactation there seems to be little effect on milk production