Using n-alkanes to estimate herbage intake and diet composition of cattle fed with natural forages in Madagascar

Accurate estimates of feed intake are important in order to develop accurate ration formulations, for selecting livestock according production efficiency, and reducing environmental impact livestock. The present study assessed the accuracy n-alkanes estimate individual herbage diet botanical composition cattle fed natural forages, typical Madagascar. effect two different forage allowances seasons on was also tested. Eight Norwegian red pie sires (232 ± 20 kg BW) were orally dosed twice daily with paper pellets containing 456.61 21.64 mg C32 alkane as external marker. Animals housed pens mixtures five forages species typically used by farmers rainy season (Aristida multicaulis, Hyparrhenia rufa, Imperata cylindrical, Urochloa brizantha Stylosanthes guyanensis) dry (Chrysopogon serrulatus, Cynodon dactylon, cylindrica, Lolium multiflorum Leersia hexandra Sw). randomly assigned allowances: (i) ad libitum a refusal 5 % (ii) 1.1 DM body weight (BW). n-alkane pairs C31:C32 C32:C33 ratio C32/Acid Insoluble Ash (AIA) plants faeces intake. estimated using profile from C27 C35 plant faeces, least squares optimization. underestimated (P < 0.0001) 25 season, both 26 animals receiving diet, regardless season. In contrast, based did not differ measured low allowance during C32/AIA actual intake, 50 %, animal consuming 0.0001). faecal recovery (AFR) corrections factors set affected 0.01) proportions each species, that comprised seasons. application appropriate AFR permitted have better estimates. It is concluded wax advantageous estimating cattle. However, improving prediction, it measure before calculation.