Nutrient utilization and ingestive behavior by lambs fed a partial mixed ration consisting of different carbohydrate sources combined with fresh alfalfa

Abstract

The objective of the current study was to evaluate the nutrient utilization by lambs fed partial mixed ration (PMR) containing either cereal grain or fibrous by-products as an energy source complemented with fresh alfalfa. Eighteen male Corriedale × Ile-de France lambs (32.2 ± 1.82 kg body weight and 4 months old) fitted with permanent rumen catheters were individually housed in metabolism cages and randomly assigned to the treatments (diets): FF, fresh alfalfa ad libitum; PMR-C, PMR containing cereal grains plus fresh alfalfa or PMR-F, PMR containing fibrous by-products plus fresh alfalfa. The amount of PMR offered corresponded to 75% of the potential total dry matter intake of lambs, in two equal meals daily (i.e. morning and afternoon) whereas fresh alfalfa was offered ad libitum from 10:00 to 18:00 h The inclusion of PMR, independently of the energy source, increased the nutrient intake and digestibility of lambs and reduced daily eating time. The ruminal fluid of lambs fed either PMR showed lower pH, higher propionate and butyrate concentration, and lower NH3 concentration compared to lambs fed only alfalfa (P < 0.01). Lambs fed PMR-F showed lower digestibility of N compounds and ruminal ammonia concentration compared to lambs fed PMR-C (P < 0.01). We concluded that offering PMR combined with fresh alfalfa to lambs had positive effects on nutrient intake, regardless of whether the energy source in PMR was starch or fibers.