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Effects of different strategies for feeding alfalfa hay on productive performance, rumen fermentation and carcass characteristics of growing lambs
A study was conducted to evaluate the effects of different feeding managements of alfalfa hay (Medicago sativa; NDF= 43.30%) supplementation, to increase NDF intake, on performance, metabolic profile, rumen fermentation and carcass characteristics of growing lambs fed a pelleted commercial total mixed ration (TMR; Wafi®; NDF= 41.95%) diets. A total of twenty 5-mo-old Awassi male lambs (BW 28.5 ± 1.5 kg) were used in an 84-d trial. Lambs were individually housed in shaded pens and randomly allocated to 4 dietary treatments (n = 5 lambs/ group) which were: 1) the basal diet without supplementary alfalfa hay (TMR; control), 2) TMR diet supplemented daily with 100 g of alfalfa hay, 3) TMR diet supplemented with 200 g of alfalfa hay every 2 d or 4) TMR diet supplemented with 300 g of alfalfa hay every 3 d. Feed intake was measured daily and lambs were weighed weekly. Blood and rumen fluid samples were collected from all lambs before feeding on d 1, 28, 56 and 84 for measurement of biochemical and rumen variables. At d 84, lambs were slaughtered to evaluate carcass characteristics and meat quality. Data were analyzed using repeated measures and the PROC MIXED model of SAS. DMI and final BW were greater (P < 0.05) for lambs on alfalfa hay diets compared to control lambs. Different feeding strategies for alfalfa hay supplementation resulted in increases (P < 0.05) pH and total VFA concentration in ruminal fluid, an improvement (P < 0.01) in lightness value of rumen tissues compared with un-supplemented lambs. The addition of alfalfa hay, with any strategy, to TMR diet improved (P< 0.05) carcass characteristics and meat quality in term of increased HCW and dressing percentage, improved meat color and reduced fatback thickness compared to control lambs. These results indicate that feeding TMR with different strategies of alfalfa supplementation improved rumen fermentation and had a positive effect on growth performance and meat quality which has important implications for the sheep industry.
Keywords: Alfalfa hay, growing lamb, rumen fermentation