Supplementation of Rumen-protected Forms of Methionine, Betaine, and Choline to Early Lactation Holstein Cows
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2006-12-11
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Abstract
Methionine (Met) is frequently the first limiting amino acid or co-limiting with lysine in dairy rations, and Met metabolism is closely linked to that of betaine and choline. Methionine, betaine, and choline are all degraded by microbes in the rumen, so rumen-protected (RP) forms were used to perform two experiments. The objective of these experiments was to investigate the impact of supplementing RP forms of methionine, betaine, and choline to a Met-limited total mixed ration (TMR) on performance, metabolism and ruminal fermentation in early lactation Holstein cows.
Experiment 1 utilized 80 lactating Holstein cows from 21 to 91 days in milk (DIM) that were fed a corn silage-based TMR formulated to meet National Research Council (2001) recommendations, except the Met content was limited (42 g⁄d). One of four supplements was blended into the TMR to produce four dietary treatments: 1.) control, 2.) 20 g⁄d RP-Met, 3.) 45 g⁄d RP-betaine, and 4.) 40 g⁄d RP-choline. Calcium salts of fatty acids were used to protect the RP-betaine and RP-choline supplements and were added to the control and RP-Met supplements so that equal amounts of fat were supplied to all treatments. Consequently, dry matter (DM) intake, body weight, and body condition score were not significantly different among treatments (P > 0.2). The treatment by parity interaction tended to be different (P = 0.06) for milk yield with 44.3 kg⁄d produced in multiparous (MP) cows fed RP-choline compared to MP cows fed all other treatments (37.8, 40.0, and 38.7, respectively) while there were no differences among treatments in primiparous cows. Cows fed RP-met or RP-choline had higher milk crude protein yield than cows fed control or RP-betaine (P = 0.02). However, there were no differences in milk fat yield or milk urea nitrogen (P > 0.2).
Experiment 2 utilized 4 dual-flow continuous culture fermentors (700 ml) to determine the effects of supplementation of rumen-protected forms of methionine, betaine, and choline to a Met-limited corn silage-based TMR on microbial metabolism by mixed ruminal cultures. Fermentors were inoculated with rumen fluid and allowed to stabilize for 2 days. Treatments were added for 5 days of adaptation followed by 3 days of sample collection. One of 4 supplements was blended into the TMR to produce 4 dietary treatments with a composition that was similar to those used in Experiment 1. Here, treatments are described as a percent of dietary DM: 1.) control, 2.) RP-Met (0.09% of DM as Met), 3). RP-betaine (0.20% of DM as betaine), or 4.) RP-choline (0.18% of DM as choline). Fat was added to all treatments as in Experiment 1. Four replicates were performed with each fermentor receiving each of the 4 treatments for one replicate. As a result, total volatile fatty acids (VFA) and individual VFA concentrations were not affected by dietary treatment, except for propionate and isobutyrate concentration. Propionate production was significantly lower in RP-choline than in control fermentors (P = 0.05). Isobutyrate production was significantly higher in control fermentors than in the ones supplemented with either RP-Met or RP-betaine, but was not significantly different from RP-choline fermentors (P = 0.05). Methane production and pH were similar across treatments (P > 0.2). Ruminal ammonia concentration was lower for fermentors receiving RP-choline than those receiving control (P = 0.04). There were no significant differences in microbial N %, flow, or efficiency between treatments (P > 0.2).
Overall, cows fed RP-choline produced more milk and milk protein than those fed the Met-limited control, and there were no beneficial effects of RP-betaine supplementation to a Met-limited TMR. Also, RP-Met, RP-betaine, and RP-choline affected ruminal fermentation minimally which suggests that they were protected from degradation.
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methionine, choline, betaine, dairy
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Degree
PhD
Discipline
Nutrition
