Studies on the TDN Requirements of Pregnant and Lactating Ewes

Two experiments were conducted to determine the TDN requirements of ewes during the last 6 weeks of gestation and the first 90 days of lactation and to determine any interaction between levels of energy fed before and after lambing. In the first experiment 110 ewes were allotted to treatments in a 2 × 2 × 3 factorial arrangement. Treatments included two levels of TDN (100% and 125% of 1957 N.R.C.) during gestation and lactation and three creep rations: hay only; hay+corn, SBOM; hay+calf starter. In the second experiment, 130 ewes were allotted to a 3 × 3 × 2 factorial arrangement of treatments, which included three levels of TDN (75%, 100% and 125% of N.R.C.) during late gestation and lactation and a separation of single and twin lambs. One hundred and forty-three lambs were born the first year and 188 the second.The results are summarized as follows: Varying TDN levels for ewes during the last 6 weeks of gestation did not affect single lamb birth weights but feeding higher levels significantly increased twin birth weights.Feeding higher TDN levels during gestation significantly increased the average 90-day weight of twin lambs in both experiments.Feeding higher lactation levels to ewes increased the 90-day weights of both single and twin lambs.Several interactions among treatments were observed and are discussed.Ewes with single lambs approximately maintained their body weight from 6 weeks pre-partum to 1 day post-partum and to 90 days post-partum when fed the present N.R.C. standard whereas ewes with twins required approximately the 125% level.Significant differences in 90-day weights among creep treatments were observed with the “complex” concentrate being superior to the “simple”, which in turn was superior to the hay alone.A cost analysis table for the lactation treatments is included.These data indicate that the present N.R.C.-TDN standard is apparently satisfactory for ewes pregnant with single lambs but increased levels for ewes pregnant with twin lambs seems advisable, together with an increase in the TDN standard during lactation for ewes with single and twin lambs.