Supplementing protein and starch combined to ewes in good body condition may not improve colostrum in ewes

Context: Lamb survival can be compromised by twin-bearing ewes being unable to produce enough colostrum and immunoglobulins following parturition. Without sufficient colostrum production, newborn lambs are at risk of death due to starvation, mismothering, exposure and infection. These deaths can be reduced by altering the ewe’s nutrition in the final weeks of pregnancy. Starch, a glucose precursor, has increased colostrum production; however, the digestibility of starch can be increased with protein supplement, which may increase colostrum production. Aims: Two separate experiments evaluated if protein supplementation, to a high-starch diet could improve colostrum production and immunoglobulin G (IgG) concentration in twin-bearing ewes. It was hypothesised that the addition of protein to a high-starch diet would have a cumulative effect on colostrum production and IgG. Methods: Ewes in both experiments were randomly allocated to one of two treatments –control and protein (120 g/day canola meal) – with both treatments receiving 600 g/head.day barley grain. Feeding began from Day 130 of gestation until 2–10 days post-lambing. Key results: Colostrum IgG concentration at 2–10 days old did not differ between treatments (P > 0.05) in both experiments. In Experiment 2, colostrum (3–7 h post-lambing) and milk production (2 days post-lambing) did not differ between treatments (P > 0.05), although metabolisable energy intake was affected by treatment (P = 0.018) with protein supplemented ewes consuming 12.91 ± 0.612 MJ ME/day and control ewes consuming 10.78 ± 0.854 MJ ME/day. Conclusions: Supplementation of ewes with protein when consuming high-starch diets did not increase colostrum production nor the IgG concentration of colostrum in ewes with pre-lambing body condition scores above industry recommendations. Implications: Supplementation of protein and starch combined has limited commercial viability and would not be recommended for late gestation ewes to increase colostrum production. However, supplementation of ewes on low-quality feed with canola meal can increase metabolisable energy intake, which may have other production benefits.