A comparison of the live-weight changes, nitrogen retention and carcass composition of pregnant and non-pregnant gilts

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Abstract
1. Twelve gilts, six pregnant and six non-pregnant, were each given a daily ration of 2.2 kg. for a 110-day period.2. Live-weight gain during this period was 53 kg. for the pregnant animals compared with 23 kg. for the non-pregnant animals.3. Apparent digestibility of nitrogen and dry matter and the energy of digested feed did not differ significantly between the pregnant and non-pregnant animals.4. Daily nitrogen retention was on average 9·2% higher for the pregnant animals, the difference between the two groups becoming progressively greater during the trial.5. Highly significant differences were found in pre-slaughter live-weight, weight of reproductive tract and weight of mammary region. The difference in the weight of free draining blood was also significant. No difference was found in the weight of alimentary tract, visceral organs, head or decapitated carcass.6. The carcasses of the pregnant animals contained less subcutaneous fat plus skin and more intermuscular fat plus muscle than those of the non-pregnant animals. The weights of bone did not differ.