Monday, November 19, 2012

What if you overfeed adolescent ewes...

Researchers at Colorado State University conducted two experiments to determine the effect of overfeeding on naturally-mated, adolescent ewes. Single-bearing ewes were fed diets meeting their gestational NRC requirements (MN; n=10 in Exp. 1, and n=7 in Exp. 2) or the same diets ad libitum (15% refusal rate) throughout gestation (HN; n=7 in Exp. 1, n=6 in Exp. 2).

Ewe body weight was greater for HN than MN ewes beginning on d-75 and d-52 of gestation for Experiment 1 and 2, respectively.  Final body condition score was greater for the HN than MN ewes in both experiments, 3.5 vs. 3.0, respectively for Experiment 1, and 4.8 vs. 2.9, respectively for Experiment 2.

Pregnant adolescent ewes
Gestation length did not differ by treatment in Experiment 1, but in Experiment 2, HN ewes had shorter gestation lengths (144 vs. 149 days) and increased dystocia scores. There were no differences in lamb birth weight and fetal measurements. In Experiment 2, there were no differences in hot carcass weight, dressing percentage, loin muscle, fat thickness, or KPH between treatments.

The researchers concluded that excess nutrition during gestation in adolescent ewes did not affect birth weight or post-natal performance of lambs.

Source:  Journal of Animal Science, November 2012.

Editor's comment:  I have two concerns about the ewes fed ad libitum:  the increased dystocia scores in Experiment 2; and the final body condition score of the HN ewes in Experiment 2 (4.8/5.0!). There is also a direct financial cost to overfeeding:  more feed + more feed wastage.

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