|ARDALAN, M - Kansas State University|
|VARGAS-RODRIGUEZ, C.F. - Kansas State University|
|VAZQUEZ-ANON, M - Novus International, Inc|
|BRADFORD, B.J - Kansas State University|
|TIGEMEYER, E.C - Kansas State University|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/2020
Publication Date: N/A
Interpretive Summary: We evaluated lactational responses of dairy cows to methionine provided from two ruminally protected Met sources. Lactating cows were fed a diet designed to be deficient in methionine and methionine was supplemented from two ruminally protected sources (NTP-1401, Novus International; Smartamine, Adisseo). Feed intake, milk yield, milk fat yield, and efficiency of milk production were not affected by methionine supplementation. Milk protein percentage and yield increased with supplementation, without differences between methionine sources. Our data demonstrated that methionine supplementation from the two tested sources can improve milk protein percentage and yield while sources affected lactation performance and milk composition similarly.
Technical Abstract: Our objective was to evaluate lactational responses of dairy cows to methionine provided from two ruminally protected methionine sources. Twenty-one Holstein dairy cows (11 primiparous [634 kg body weight, 140 days in milk, body condition score 3.6] and 10 second parity [670 kg body weight, 142 days in milk, body condition score 3.2]) were assigned to a treatment sequence in four replicated 5 × 5 Latin squares with 14-d periods. Treatments included: 1) control, 2 and 3) 7.5 and 15 g/d of a ruminally protected source of 2-hydoxy-4-methylthio-butyric acid (NTP-1401; Novus International, Inc., St. Charles, MO), and 4 and 5) 7.5 and 15 g/d of a ruminally protected DL-methionine product (Smartamine; Adisseo, Alpharetta, GA). The diet was predicted to meet metabolizable protein and energy requirements when dry matter intake was 25.6 kg/d for lactating Holstein cows producing 45 kg/d milk with 3.5% fat and 3.0% true protein. Diets contained 16.1% crude protein and the control diet was predicted to be deficient in metabolizable methionine (1.85% of metabolizable protein) but sufficient in lysine (6.8% of metabolizable protein). Feed intake and milk production were measured on d 11 to 14. Blood was collected on d 14. Dry matter intake, milk yield, energy-corrected milk, milk fat yield and percentage, and efficiencies of milk and energy-corrected milk production were not affected by treatment. Milk protein percentage and milk protein yield increased linearly with supplementation, without differences between methionine sources or interactions between source and level. Linear regressions of milk protein percentage and milk protein yield against supplement amount within source led to slope ratios (NTP-1401:Smartamine) of 95% for protein percentage and 84% for protein yield, with no source differences for increasing milk protein. Plasma methionine concentrations were increased linearly by methionine supplementation, with the increase being greater for Smartamine than for NTP-1401. Plasma D-methionine was increased only by Smartamine. Plasma 2-hydoxy-4-methylthio-butyric acid was increased only by NTP-1401. Our data demonstrated that supplementation with these methionine sources can improve milk protein percentage and yield and the two methionine sources did not differ in their effect on lactation performance or milk composition.