Alternative forages for pregnant and lactating ewes

Dry matter intake of forages varied throughout the trial but intake of RC was significantly higher (P<0.001) than all other forages until week +2 when intakes of all other silages increased. Intake of GS was consistently lower than all other silages from week -5 to week -2.  RC fed ewes tended to maintain body condition better than ewes on the other forages and were in significantly better condition at lambing (P<0.01) than GS or UTWC/GS fed ewes.

Plasma urea was significantly higher for LS fed ewes suggesting a surplus of ERDP in the diet.  Lamb birth weights tended to be higher for GS fed lambs (NS) and lowest for RC lambs but thereafter lambs from RC fed ewes tended to grow faster (NS) than lambs from ewes on the other three forages.

Lamb performance compared well to other published work on similar silages. High protein forages can be fed without additional protein supplementation to save on purchased feed costs but the particularly high dry matter intake of RC silage in this trial suggested a greater requirement for forage that needs to be taken in to account when costing out rations for pregnant and lactating ewes.

The Problem:

More and more producers are feeding ewes on high quality forages during late pregnancy and early lactation.  However, there are not many studies that compare ewe and lamb performance on different forages that are gaining in popularity.  It is becoming clear from on-farm studies that feed intakes on high quality silages are higher than predictions, so this work will provide good data on individual intakes.

Aims and Objectives:

The overall aims of the project are to:

• Demonstrate the use of alternative forages (red clover, lucerne and whole crop wheat) for ewes in late pregnancy and early lactation Compare costs of pre-lambing and early lactation feeding on different forages
• Assess lamb performance to weaning from ewes fed alternative forages in late pregnancy and early lactation

Approach:

48 twin bearing Suffolk cross Mule ewes will be housed at 8 weeks before lambing and blocked by age, weight and BCS to one of four treatments.  On housing in January they will be kept in groups of 12 for 2 weeks to acclimatise to the basal forage (offered with straw) and to allow for estimation of forage dry matter intake.  Subsequent diets will be formulated based on chemical analysis of the forages, actual dry matter intake and ewe live-weight and condition.

Diets will be balanced for energy and protein intake. Appropriate supplementation will be provided once daily (depending on amount required) based on supplying AFRC (1993) allowances for metabolisable energy (ME) and metabolisable protein (MP) and achieving target body condition scores.

Ewes will be penned individually from 6 weeks pre-lambing up to 4 weeks post lambing and ewe weight and body condition score will be assessed weekly.

Forage and concentrate intake of all ewes will be recorded daily whilst housed. Lambs will be weighed at birth and weekly until 4 weeks of age and then at 8 weeks and 12 weeks.  Ewes will be weighed and condition scored at 4, 8 and 12 weeks post lambing.

Feed costs, including costs of growing and harvesting the forages and cost of supplements will be calculated accurately to provide guidance to farmers on the economic viability of the alternative forages as feeds for pregnant and lactating ewes.