Protein and Methionine Hydroxy Analog for Lactating Cows

Open Access
Publisher Website
Google Scholar
Abstract
A 2 .times. 2 factorial experiment (protein 12.5 and 15.5; methionine hydroxy analog 0 and .125% dry matter) included 144 cows for 1 complete lactation, distributed over 7 locations. Rations were formulated to the desired protein, methionine analog, and constant amounts of fiber 17%, S .225%, Ca .6%, P .4%, and salt .5%. Treatment effects were not apparent for dry matter intake, daily milk and fat-corrected milk production, conversion of energy, and body weight changes. Conversion of dietary crude protein into milk protein was 34.5% for the low and 25.8% for the high protein ration. Methionine analog affected fat test (0% = 3.61%; .125% = 3.73%) and number of services/conception (0% = 2.54; .125% = 1.90). Effect of methionine analog was most apparent at low protein as 0 analog cows produced 247 kg fat, required 2.9 services/contraception, and had 156 days open while cows on other treatments (.125% analog and/or high protein) produced 264 kg fat, required 1.8-2.2 services/conception, and had 124-134 days open. Methionine analog response is discussed in relation to ruminal and postruminal effects as well as the interrelation with protein and energy.