Effects of Supplemental 2-hydroxy-(4-methylthio) Butanoic Acid and Branched Chain Volatile Fatty Acids in Lactating Dairy Cows PDF Download

Author: Jacob E. Copelin
Publisher:
ISBN:
Category : Dairy cattle
Languages : en
Pages : 136

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Book Description
2-hydroxy-(4-methylthio) butanoic acid (HMTBa), a methionine analog, can alleviate dietary induced milk fat depression by increasing milk fat percent and changing the milk fatty acid profile. Branched chain volatile fatty acids (BCVFA) are important growth factors for rumen cellulolytic bacteria, which biohydrogenate polyunsaturated fatty acids into compounds that contribute to milk fat depression. Therefore, the objective of these experiments is to determine how HMTBa, BCVFA, or their combination affects rumen fermentation, milk production and profile, and nutrient digestibility in dairy cows. We hypothesized that HMTBa and BCVFA would improve rumen biohydrogenation of polyunsaturated fatty acids and reduce risk of milk fat depression and that the combination of the two would have a synergistic effect. To test the hypothesis, three experiments were conducted: two in vitro batch cultures and an in vivo experiment. Experiment 1 used the following treatments: a typical diet (50:50 of forage to concentrate on a DM basis, CON), CON with the addition of 3.0% linoleic acid (DM basis, LA), LA with 0.1% D/L methionine (MET), and 0.1% of HMTBa (Rhodiment, Adisseo Inc.) in an in vitro system. Experiment 2 had the following treatments: a typical diet (60:40 of forage to concentrate on a DM basis, CON), CON with the addition of 3.0% linoleic acid (DM basis, LA), LA with 0.1% HMTBa, LA with equal molar proportions (1 mmol/L) of isovalerate, isobutyrate, and 2-methylbutyrate (BCVFA), and a combination of HMTBa and BCVFA (COMBO) in an in vitro system. Experiment 3 was designed as a replicated 5 × 5 Latin square design using 5 ruminally cannulated and 5 non-cannulated lactating Holstein cows (194 ± 58 DIM) blocked by cannulated and non-cannulated cows. Treatment diets included a high forage diet (32.2% NDF of which 64.4% came from forage NDF, 24.0% starch, and 3.4% FA; HF), a low forage diet (28.9% NDF of which 60.1% came from forage NDF, 29.1% starch, and 3.5 FA; LF), LF with 0.1% HMTBa (LF-HMTBa), LF with equal molar proportions of isobutyrate, isovlalerate, 2-methylbutyrate, and valerate (LF-BCVFA), and LF with the combination of HMTBa and BCVFA (COMBO). All data were analyzed using mixed procedures of SAS. Experiment 1 and 2 were a completely randomized design with incubation as the random effect and treatment and hour as fixed effects. Means were compared within hour (each time point) by least significant difference. Experiment 3 was a 5 × 5 Latin square design with period and treatment were fixed effects and cow and cow within square as random effects. Day was used as repeated measures for production data, and hour replaced day for rumen fermentation analysis. In experiment 1 and 2, there were minimal changes in the biohydrogenation of linoleic acid. There was no difference in either 18:1 trans-10 or 18:2 cis-12, trans-10 CLA in any treatment for either experiment 1 or 2. Supplementation of HMTBa increased (P