Effect of the amount of concentrate offered in an automated milking system on dry matter intake, milk yield, milk composition, ruminal digestion, and behavior of primiparous Holstein cows fed isocaloric diets

摘要

The objective of this study was to determine if thequantity of concentrate provided in an automated milkingsystem (AMS) affects dry matter intake (DMI), attendanceto the AMS, milk and milk component yield,feeding behavior, cow activity, and ruminal fermentationof lactating dairy cows fed isocaloric diets. Eightruminally cannulated primiparous Holstein cows wereused in a replicated 4 × 4 Latin square design with 28-dperiods. Cows were housed in a freestall facility with aguided-traffic (feed-first) flow barn design. Treatmentsincluded 0.5, 2.0, 3.5, or 5.0 kg/d of dry matter of pelletin the AMS with an equivalent reduction of thesame pellet in the partial mixed ration (PMR). Days21 to 24 of each treatment period were used for DMI,milking performance (visits, yield, and composition),behavior, and ruminal pH determination, and d 25 to28 were used for ruminal short-chain fatty acid and ammoniaconcentrations as well as total-tract digestibility.As imposed, consumption of AMS pellet linearly increased,equating to 0.50, 2.00, 3.49, and 4.93 kg of drymatter/d for the 0.5, 2.0, 3.5, and 5.0 kg/d treatments,respectively. Correspondingly, the standard deviationin AMS pellet intake among days linearly increasedfrom 0.06 to 0.85 kg of dry matter/d as the quantity ofconcentrate in the AMS increased from 0.5 to 5.0 kg.The PMR DMI decreased linearly with increasing AMSconcentrate allocation, but total DMI (PMR + AMS)was not affected (25.3 kg/d). As the AMS concentrateallocation increased, the selection against particles retainedon an 18-mm sieve linearly increased and selectionagainst particles retained on the pan decreased.Milking frequency (3.22 milkings/d), milk yield (37.5kg/d), milk fat yield (1.43 kg/d), and milk proteinyield (1.22 kg/d) were not affected; however, milk ureanitrogen concentration decreased linearly with increasingAMS concentrate. Ruminal pH averaged 6.18 andwas not affected by AMS concentrate. Total ruminalshort-chain fatty acid concentration was greatest when3.5 kg of concentrate was allocated in the AMS andruminal ammonia decreased linearly with increasingAMS concentrate. Time spent lying, the number of lyingbouts, and average bout duration were not affectedby treatment. These data indicate that increasing thequantity of concentrate in the AMS increases dailyvariability in AMS concentrate intake while decreasingPMR intake without affecting voluntary visits to theAMS and milk or milk component yield. As such, underisocaloric dietary settings, increasing the supply of pelletin the AMS is not likely to affect voluntary visits tothe AMS, milk and milk component yields, or ruminalfermentation.