Associative effects of supplementing barley straw diets with alfalfa hay on rumen environment and nutrient intake and digestibility for ewes

Abstract

The objectives of these experiments were to study the positive associative effects of supplementing barley straw-based diets with different levels of alfalfa hay on nutrient intake, rumen environment, and nutrient digestibility and to evaluate the minimal amount of alfalfa hay needed to produce such an effect in ewes. In experiment one, 15 Awassi ewes (five ruminally fistulated; body weight=54 kg±1.5 ) were fed five barley straw-based diets in a 5×5 Latin square design with 3-week periods. Dietary treatments were as follows: diet 1, barley straw (no supplement), diet 2, barley straw supplemented with 1% urea (dry matter basis), diets 3, 4, and 5 barley straw supplemented with 150, 300, and 450 g of alfalfa hay, respectively. In experiment 2, the same experimental diets were fed to 50 ewes (10 ewes/diet) for 50 days in a complete randomized design. In experiment 1, dry matter intake (DMI) was increased ( P<0.05) by the addition of alfalfa hay compared with diets that had no alfalfa. Metabolizable energy intake (MEI) increased linearly ( P<0.05) with the increasing amounts of alfalfa hay, being highest ( P<0.05) for diet 5. Diets that contained alfalfa hay had greater ( P<0.05) dry matter (DM), organic matter (OM), neutral detergent fiber (NDF), and crude protein (CP) digestibilities. The extent of barley straw NDF digestibility was also increased ( P<0.05) with the alfalfa addition (67 versus 60.5%). Rumen ammonia and VFA concentrations were higher ( P<0.05) in diets that contained alfalfa, however, rumen pH was not affected by the diet (avg. 6.64). In experiment 2, the effect of alfalfa hay addition to barley straw-based diets had similar effects on DMI as observed in experiment 1. Straw intake increased ( P<0.05) with the 150 g addition of alfalfa hay compared with unsupplemented diet (725 versus 650 g −d per day) with no further improvement with the higher amounts of alfalfa. It seems that the minimal amount of alfalfa hay needed to produce the positive associative effect on barley straw is 150 g per day for maintenance diets of ewes.