Minimal feeding of pregnant ewes

P.V. Rattray, T.E. Trigg

Ruakura Animal Research Station, Hamilton

Proceedings of the New Zealand Society of Animal Production. 1979, 39: 242-250

Two comparative slaughter trials were conducted during the last third of pregnancy with Coopworth ewes that had been diagnosed pregnant by X-ray analysis on about day 90 of gestation. In the first trial from ditocous ewes an initial slaughter group of 9 was killed on day 95 of gestation, while the remaining were randomized into groups fed at an average of 1.0, 1.25, 1.5, 1.75 or 2.0 times non-pregnant maintenance, until slaughter at day 140. With increased level of feeding, ewe liveweight gains increased from 4.6 to 13.7 kg; empty body weight changed from - 3.9 to 2.0 kg; average foetal weights from 3.9 to 4.7 kg; mammary weights from 1.2 to 2.3 kg; and wool growth from 0.43 to 0.71 kg. Foetal weight was negatively related to ewe empty body weight change and positively related to the day 90 weight of the ewes, suggesting that ewe body reserves may influence foetal growth under such circumstances.

In the second trial, 110 ewes were randomized after mating into two groups, one restricted (L/-) and one fed liberally (H/-) so as to achieve a 16 kg difference in liveweight by day 90 of gestation (51.4 kg vs 67.2 kg). Ewes were diagnosed by X-ray into single and twin bearing, and initial slaughter groups taken on day 95. The remainder were randomized and fed at either 1.0 (-/L) or 1.75 (-/H) times non-pregnant maintenance until slaughter at day 135. From day 90, changes in various weights (kg) for LL, LH, HL, and HH twin-bearing ewes were respectively: empty body weight, -8.1, -2.1, -8.9 and -4.1; average foetal weights, 2.9, 3.4, 3.5 and 3.7; mammary weights, 0.6, 1.2, 0.9 and 1.5; wool growth, 0.13, 0.17, and 0.35 and 0.30. For the LL, LH, HL and HH single-bearing ewes: empty body weight, -5.9, -2.4, -7.3 and 0.7; average foetal weight, 3.6, 4.3, 4.0 and 4.5; mammary weights, 0.5, 1.3, 0.7 and 1.0; wool growth, 0.15, 0.23, 0.35 and 0.33. Level of feeding during mid pregnancy influenced foetal, mammary and wool weights, in spite of feeding levels in late pregnancy. Maternal reserves can compensate for considerable nutritional deprivation in late pregnancy when ewes are in good body condition.

Keywords: NZSAPAB;

Last Updated 12-09-1998