Effects of feeding salt-tolerant forage cultivated in saline-alkaline land on rumen fermentation, feed digestibility and nitrogen balance in lamb.

Background: Mixing salt-tolerant plants with other plants may affect rumen fermentation, which could result in an increase of feed conversion rate. The objective of this study was to evaluate the effects of partially or entirely replacing the corn stover with a mixture of salt-tolerant forage (Dahurian wildrye grass, weeping alkaligrass and erect milkvetch) in the diet of lambs on ruminal fermentation, feed digestibility and nitrogen (N) balance. Ratios of corn stover to the mixture of salt-tolerant forages in the four experimental diets were 100:0, 67:33, 33:67 and 0:100, respectively, for control, low (LF), medium (MF) and high (HF).

Results: Ruminal pH was lower (P = 0.048) with LF and MF than with control and HF diets. Total VFA concentration was consistently higher (P = 0.039) for LF and MF than for control and HF with increasing amount of salt-tolerant forage. Ratio of acetate to propionate was linearly (P = 0.019) decreased due to the decrease in acetate production. Digestibilities of OM, NDF and CP in the whole tract linearly (P < 0.002) decreased with increasing amount of salt-tolerant forage. Similarly, retained N and ratio of retained N to digestible N also linearly (P < 0.005) decreased.

Conclusion: Feeding salt-tolerant forage cultivated in saline-alkaline land improved rumen fermentation with increased total VFA production, and changed the rumen fermentation pattern to increased butyrate production. However, the decreased feed digestibility in the whole digestive tract of lamb may reduce nutrient availability to animals and thus adversely affect animal productivity. Additionally, feeding salt-tolerant forages may require more protein supplement to meet animal requirements, because of the low protein content and low protein digestibility of the salt-tolerant forages.