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Gordon E. Dickerson

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A THESIS Presented to the Faculty of The Graduate College in the University of Nebraska In partial Fulfillment of Requirements For the Degree of Master of Science, Major: Animal Science, Under Supervision of Professor Gordon E. Dickerson. Lincoln, Nebraska: July, 1986



Data from an embryo transfer project were used to study the effect of twinning on both dams and calves in terms of meat and milk production and post-partum fertility. and to evaluate the changes in energy requirements during gestation. lactation and postweaning periods.

Pregnancy rate at first palpation was 70% (45% twin pregnacy and 25% single pregnancy) and calving rate was 65% (39% twins and 26% singles). Losses from abortion were 2.7%. Calf mortality was 2% higher for twin-calving dams. Dystocia was affected (P<.05) more by parity than by twinning (30% in heifers and 10% in cows) but retained placenta was the opposite (8.5% in single-calving and 32% in twincalving dams).

Twin-calving dams gained 22% slower during gestation but 5% faster during lactation and the 9% of advantage in weight at the beginning of gestation compared with single-calving dams was reduced to about 3.2% at calving and 2.8% at weaning.

Twin-calving dams produced 28% more total lactation milk and 23% more daily milk at peak lactation. They also reached peak lactation later. but were 2% higher in persistency.

Twin-calving dams were 23% later in days to first ovulation. 13% later in days open and 4% later in calving interval although twinning effect on calving interval was not significant.

Twin-pregnancy was at least 3 days shorter (P<.01) and produced 13% lighter calves at birth. Twins gained 19% slower (P<.01). were 17% lighter at weaning (P<.01) and had 4% lower relative preweaning relative growth rate than singles. Twins were similar in postweaning daily gain and 14% higher in relative growth rate (P<.01) but were still 10% lighter than singles (P<.01) at slaughter.

Daily fetal ME requirements during last third of gestation for twin-pregancy was 67% higher than for single-pregnancy but daily gain in empty body weight was 22% less (P<.01). Daily ME for maintenance and intake were not affected by parity and twinning.

Dams nursing twins required 44% more of ME daily for milk yield and ingested 11% more of daily ME than dams nursing singles during 180-d lactation. Daily ME for maintenance was similar for all types of dams.

During postweaning growth to market age. twins consumed 6% less feed daily. required 4% less feed/gain. 12% less net nergy/gain. 11% less net energy/kg metabolic size and 3% less metabolizable energy for gain or maintenance.

A commercial beef industry using twinning could expect an an increase in output relative to the total input in the range of 20 to 25% at slaughter time.