Effects of replacement of alfalfa by inflorescences of Yucca carnerosana in the diet on performance of growing goats

The chemical composition, in vitro organic matter digestibility (OMD), and energy content of inflorescences of Yucca carnerosana, an endemic species to the Chihuahuan desert of Northern Mexico were evaluated. The effects of addition of air-dried inflorescences of Y. carnerosana, replacing alfalfa in the diet of growing goats were also studied. Forty growing female crossbred goats (native × dairy goats; 12.4 ± 2.1 kg; 3 months of age) were assigned to five equal groups in a completely randomized design. Zero (T0), 25 (T25), 50 (T50), 75 (T75) and 100% (T100) inflorescences of Y. carnerosana were added for alfalfa replacement (300 g kg− 1 of the diet) in a completely mixed diet based on corn grain and soybean meal. Values of nutritional parameters for inflorescences of Y. carnerosana were: in vitro OMD, 701 g kg− 1; crude protein, 130 g kg− 1; metabolizable energy, 9.56 MJ kg− 1 DM. Average daily gain (ADG) (range 90 ± 6 to 125 ± 21 g) and dry matter intake (DMI; 471 ± 72 to 554 ± 44 g day− 1) were similar among dietary groups. Feed conversion ratio (FCR, DMI/ADG) differed (P < 0.05) between T0 (4.0 ± 0.4 g g− 1) and T75 (5.7 ± 1.3 g g− 1) and T100 (6.2 ± 0.4 g g− 1). Rumen total volatile fatty acid (VFA) concentrations did not differ between treatment groups (range 60.7 to 68.7 mM, averaged over 3 sampling times), but proportions of acetate was lower (P < 0.05) in T75 and T100 compared with other dietary treatments. Overall molar proportion of propionate was higher (P < 0.05) in T100 than other dietary treatments. Goats fed T0 had higher (P < 0.05) levels of blood glucose, urea and cholesterol than animals on the other dietary treatments. It was concluded that 50% DM of alfalfa hay in the diet of goats can be safely replaced with inflorescences of Y. carnerosana without adverse effects on their growth performance.