Impact of forage levels and physical forms on feed sorting behavior, rumen morphometry, and selected blood parameters in fattening male goats

Abstract

This study assessed the impact of physical form of diet and Rhodes grass (RG) level on feed sorting behaviour, rumen morphometric measurements, and blood parameters in goats. Forty male goats were equally assigned to four dietary treatments: mash total mixed ration (TMR) containing 15 % RG and 85 % concentrate (RG15M), 25 % RG and 75 % concentrate (RG25M), pelleted TMR (containing similar levels of RG hay as for mash diets) as RG15P, and RG25P. Goats selected particle sizes larger than 6.70 mm, with no difference (P > 0.05) between RG15M and RG25M. The consumption of particles larger than 4.75 mm and 3.35 mm size was similar in RG15M and RG25M. However, the consumption of particle size larger than 2.36 mm and 1.18 mm was higher in RG15M compared to RG25M. Rumen papillae density and surface area were greater (P < 0.05) in RG25P than in RG15M, RG25M, and RG15P. Blood urea nitrogen, plasma protein, alanine transaminase, aspartate transaminase, and bilirubin concentrations were higher (P < 0.05) in RG15P compared to other treatments, whereas cholesterol concentration was lower in RG15P than RG15M, RG25m, and RG25P. The goats preferentially consumed fibrous particles (>1.18 mm) and rejected finer particles (< 1.18 mm). Goats fed the pelleted diet with 25 % RG showed improvement in rumen surface area without adversely affecting blood constituents, highlighting the benefits of pelleting to avoid feed selection and using TMR containing 25 % RG and 75 % concentrate.