Acetate is a major source of energy and substrate for milk fat synthesis in the dairy cow. We recently reported a linear increase in milk fat yield and greater than a 30% net apparent transfer of acetate to milk fat with ruminal infusion of neutralized acetate. Additionally, ruminal acetate infusion linearly increases plasma β-hydroxybutyrate. The objective of the current study was to investigate the ability of acetate and butyrate fed in a diet to increase milk fat synthesis. Twelve multiparous lactating Holstein cows were randomly assigned to treatments in a 3 × 3 Latin square design with 14-d periods that included a 7-d washout followed by 7 d of treatment. Cows were fed ad libitum a basal diet with a low risk for biohydrogenation-induced milk fat depression, and treatments were mixed into the basal diet. Treatments were 3.2% NaHCO 3 (control), 2.9% sodium acetate, and 2.5% calcium butyrate (carbon equivalent to acetate treatment) as a percent of diet dry matter. Feeding sodium acetate increased dry matter intake by 2.7 kg, had no effect on milk yield, and increased milk fat yield by 90 g/d and concentration by 0.2 percentage units, compared with control. Calcium butyrate decreased dry matter intake by 2.6 kg/d, milk yield by 1.65 kg/d, and milk fat yield by 60 g/d, compared with control. Sodium acetate increased concentration and yield of 16 carbon mixed source fatty acids (FA) and myristic acid, while decreasing the concentration of preformed FA, compared with control. Calcium butyrate had no effect on concentration of milk FA by source, but increased concentration of trans-10 C18:1 in milk by 18%, indicating a shift in rumen biohydrogenation pathways. Our data demonstrate that milk fat yield and concentration can be increased by feeding sodium acetate at 2.9% of diet dry matter, but not by feeding calcium butyrate at an equivalent carbon mass.
Milk fat trans-10 C18:1 can be used in diagnosing milk fat depression, but it must be determined using gasliquid chromatography that commonly requires long-distance shipping for analysis. The objective of this study was to determine the effect heat treatment before storage and different storage temperatures on milk fatty acid (FA) profile over time to recommend a suitable shipping method. Heating the sample before shipping, shipping temperature, and shipping time had very little effect on any FA analyzed. Based on this, we propose that freezing samples and shipping in a sealed bag by second-day shipment is appropriate for gas-liquid chromatography analysis of FA profile.
Highlights• Milk fatty acid profile was very stable at all storage temperatures. • Shipping on dry ice is not required for fatty acid analysis by gas-liquid chromatography. • Importantly, this conclusion is specific for gas-liquid chromatography analysis and not other infrared spectrometry-based methods.
Daily dry matter intake is a key observation in dairy nutrition, and observation of feeding behavior provides insight into the physiological control of hunger and satiety that regulate intake. The objective of the study was to develop and validate an alternative method to observe feeding behavior, including meal length and frequency, in a Calan Broadbent Feeding System (American Calan) using a 3-axis accelerometer (Hobo Pendant G, Onset Computer Corp.). Sensors were mounted between the door and the feed divider using commonly available materials without making permanent modifications to the feeding system. Forty-eight sensors were deployed with a recording frequency of 30 s for the last 7 d of each period in a crossover experiment with 24 multiparous and 24 primiparous animals housed in a freestall barn. The tilt angle on the Z-axis was used to determine when the door was open to indicate feeding activity. The sensor system was in very high agreement with 6 h of visual observation (Cohen's κ = 0.92 ± 0.014; estimate ± 95% confidence interval). The minimum intermeal interval is the time between 2 feeding bouts that is still considered one meal. This essential criterion to characterize meals was calculated by determining the intersection of a mixture of Gaussian distributions fitted to the log-transformed between-feeding intervals. The best fitting mixture of Gaussian distributions was determined with the distribution module of JMP Pro 14.3.0 (SAS Institute Inc.). The minimum intermeal interval was 31.3 min using the best fitting model, a mixture of 3 Gaussian distributions. Using the determined minimum intermeal interval, meal length averaged 37.3 min/meal and meal frequency averaged 7.3 meals/d. In conclusion, data-logging 3-axis accelerometers are adequate to monitor presence of cows in the feed gate in the Calan Broadbent Feeding System, and this approach allows for reasonable estimation of meal length and frequency.
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