| Abstrakt: |
Voluntary intake, digestibility, N balance, and chewing behavior of six 6-mo-old (young) and six 30-mo-old (mature) Texel wethers (32.6 and 83.1 kg average BW) given ad libitum access to grass silage and 100 g of top-dressed soybean meal with or without 5 g of methionine hydroxy analog (MHA) in the acid form were examined according to a two-period crossover design. Supplementation level of MHA in the acid form corresponded to .32 and .16 g of MHA/kg BW•75, respectively, in young and mature wethers. There was no effect (P> .10) of MHA on mean voluntary DMI. Methionine hydroxy analog supplementation increased (P< .02) digestibility of DM, OM, and CP by young wethers but not (P> .18) by mature wethers. The MHA decreased eating time (P< .03) in both young and mature wethers and intake level (P =.01) in young wethers during the first 1.5 h of access to grass silage. With MHA, both age groups increased (P< .05) the daily number of meals and decreased (P< .02) the mean duration of each meal. There was no effect (P> .06) of MHA on daily and unitary eating, ruminating, and masticating times; however, mean duration of consecutive rumination bolus cycles was longer (7.2%; P= .01) in young wethers. Young vs mature sheep ate more (53.4 vs 39.3 g of DM/[dkg BW•75]; P< .001) and had shorter unitary mastication times (P =.001). Results suggest that, depending on its relative level of supplementation, MHA in the acid form could act through both palatability and effects on ruminai metabolism. |
