Effects of methionine hydroxy analog on voluntary intake, digestibility, nitrogen balance, and chewing behavior in sheep fed grass silage
1991
Deswysen, A.G. | Bruyer, D.C. | Naveau, C. | Mol, J. de | Ellis, W.C.
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 NM 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/[d.kg BW.75]; p < .001) and had shorter unitary mastication times (P = .001). Results suggest that, depending on its relative level of supplementation, NM in the acid form could act through both palatability and effects on ruminal metabolism.
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