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Supplementation of methionine and methionine analogs to diets with risk of biohydrogenation-induced milk fat depression.

K. Harvatine



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Supplementation of methionine and methionine analogs to diets with risk of biohydrogenation-induced milk fat depression.
M. Baldin1, S. Fredin2, K. Harvatine*1. 1Penn State University University Park, PA, 2Adisseo USA Inc Ithaca, NY.

We have previously observed that the rumen available methionine analog 2-hydroxy-4-(methylthio)butanoate (HMTBa) reduced BH-induced MFD when feeding high unsaturated FA and high starch diets. The effect of other sources of methionine have not been investigated, but may play a role through both ruminal and post-ruminal mechanisms. Ten primiparous (97 � 27 DIM; mean � SD) and 26 multiparous (97 � 33 DIM; mean parity = 3) cows were arranged in a 5 � 5 Latin square design. Treatments were (cow/d basis): unsupplemented control; 30 g/d of HMTBa (Alimet; Novus International, Inc., St. Charles, MO); 43 g/d of HMBi (MetaSmart, Adisseo, Alpharetta, GA); 12 g of HMTBa and 42.9 g of HMBi; and 26.5 g of rumen protected methionine (RPM; Smartamine M, Adisseo). Each period in the replicated design included low (d 1 to 20), moderate (d 21 to 27), and high (d 28 to 30) risk of BH-induced MFD phases. Risk for altered BH was increased by reducing diet NDF and increasing UFA and starch content. Data was analyzed using repeated measures in Proc Mixed. The model included the random effect of cow and period and the fixed effect of treatment and day. Subject was cow � period and the TOEP covariance structure was used. Overall milk fat concentration decreased from 3.83 to a 3.64% and trans-10 C18:1 increased from 0.45 to 1.23% of FA between the low- and the high-risk phases demonstrating moderate induction of BH-induced MFD. There was no interaction of treatment by dietary risk for milk fat concentration and yield, but there was an overall effect of treatment as both were increased by all treatments but HMBi from 0.11 to 0.16 percentage units and 85 to 132 g/d (P < 0.05). However, there was no effect of treatment on milk trans-10 C18:1. There was a treatment by day interaction for milk protein concentration and yield (P < 0.05) with RPM increasing milk protein concentration and yield most consistently. In conclusion, both rumen available HMTBa and rumen protected methionine decreased risk of MFD when increasing dietary unsaturated FA and starch.

Keywords: 2-hydroxy-4-(methylthio)butanoate (HMTBa), methionine, milk fat depression.