Using 19% of alfalfa hay in beef feedlot finishing diets did not modify meat quality but increased feed intake and ADG

To evaluate the effects of including extra alfalfa hay in high concentrate diets fed to beef heifers on intake, average daily gain (ADG), gain to feed ratio (G:F), and carcass and meat quality, we used 24 Simmental heifers (initial BW 235.6 ± 4.19 kg). Heifers were blocked in 4 BW blocks and allotted in groups of 3 in a randomized block design with 2 treatments and 12 heifers per treatment. Treatment diets offered as total mixed ration (TMR) were: a) TMR with 10% barley straw (BS), considered the control diet, and b) TMR with 19% alfalfa hay (AH). The experiment was performed over 4 28-d experimental periods, and we took measurements in the last week of each period. After this period of performance control, heifers were fed the corresponding diet until each BW block reached the target weight of 400 kg on average. Feed intake and ADG were greater for AH than BS (9.5 vs 8.4 kg/d, and 1.45 vs 1.29 kg/d, respectively; P 0.10). Diet did not affect hot carcass weight, dressing percentage, backfat color, pH and meat color, or carcass grade. The sixth rib was dissected to determine the proportion of fat, lean and bone, which were unaffected by diet. Diet did not affect the Longissimus muscle composition in water, protein, collagen, intramuscular fat, and cholesterol. The intramuscular fat proportion of C18:1 n-7 was greater in BS than in AH (P = 0.016), whereas the proportion of C18:3 n-3 tended to be greater in AH than in BS (P = 0.09). When fatty acid concentration was expressed as g per 100 g of Longissimus muscle, these differences disappeared, and only the content of C15:0 tended to be greater (P = 0.08) in BS than in AH. Meat characteristics evaluated by trained panelists did not differ in toughness, chewiness, juiciness, odor, taste and overall acceptability, and there were no differences between diets in Warner-Bratzler shear force values after 3 or 10 d of ageing (P > 0.10). In summary, heifers fed TMR with alfalfa hay at 19% of inclusion showed a greater feed intake and ADG than those fed barley straw at 10% of inclusion, but without affecting G:F ratio. However, this extra alfalfa hay was not sufficient to cause any relevant change in the carcass and meat quality of the heifers fed this diet.