Feeding Acacia saligna to Sheep and Goats with or without the Addition of Urea or Polyethylene Glycol

Effects of urea supplementation on ruminal fermentation characteristics, nutrient intake, digestibility, and performance in sheep: A meta-analysis

Background and Aim:

As a non-protein nitrogen source, urea is a popular, low cost, and easily obtained protein supplement. The objective of the present study was to perform a meta-analysis of the effects of urea supplementation on rumen fermentation and sheep performance.

Materials and Methods:

A total of 32 experiments from 21 articles were compiled into a dataset. The levels of dietary urea varied from 0 to 31 g/kg of dry matter (DM). Parameters observed were rumen fermentation product, nutrient intake, nutrient digestibility, and sheep performance. This dataset was analyzed using a mixed model methodology, with urea supplementation levels as fixed effects and the different experiments as random effects.

Results:

Increasing levels of urea were associated with increases (p=0.008) in rumen pH, butyrate (C₄) production, and ammonia (NH₃–N) concentration. Urea supplementation had minor effects on total volatile fatty acids (p=0.242), total protozoa (p=0.429), and the microbial N supply (p=0.619), but tended to increase methane production (CH₄; p<0.001). Supplementation of urea increased the intake of dry matter (DM; p=0.004) and crude protein (CP; p=0.001). Digestibility parameters, such as DM digestibility (DMD) and CP digestibility (CPD), also increased (p<0.01) as a result of urea supplementation. Retained N (p=0.042) and N intake (p<0.001) were higher with increasing levels of urea supplementation. In terms of animal performance, supplementation of urea increased average daily gain (ADG; p=0.024), but decreased the hot carcass weight percentage (p=0.017).

Conclusion:

This meta-analysis reports the positive effects of urea supplementation on rumen fermentation products (i.e., pH, C₄, and NH₃–N), intake (DM, CP, and N), digestibility (DMD and CPD), and ADG in sheep.

Effect of supplementing Rhodes grass hay (Chloris gayana) with Berchemia discolor or Zizyphus mucronata on the performance of growing goats in Kenya

Twenty growing Small East African goats were used to determine the effects of feeding sun-dried leaves of the browse forages Berchemia discolor and Zizyphus mucronata as supplements to low-quality basal diet, Rhodes grass (Chloris gayana) hay, on voluntary feed intake (VFI), digestibility and growth performance. The grass hay and maize bran were used as a control. The dried leaves were then included at the rates of 15% and 30% of the dry matter intake (DMI). Berchemia discolor had the highest crude protein (CP) content of 195.5 g/kg DM, while Z. mucronata had CP content of 169.5 g/kg DM. The grass hay had the lowest CP content of 50.9 g/kg DM. The browse forages had low fibre content [Neutral detergent fibre (NDF); 257.9-369.5 g/kg DM], while the grass hay had high fibre content (NDF; 713.1 g/kg DM). Goats in the groups supplemented with either of the browse forages had higher total DMI, nitrogen (N) intake and retention and live-weight gains than those in the control diet group. The digestibility of DM and organic matter (OM) was not affected by supplementation, but the CP digestibility increased with supplementation. The use of the browse forages as supplements for goats fed on poor-quality basal diets would enhance the performance of the animals.