Author : Peter Samuel Yoder
Publisher : Unknown
Release : 2012
ISBN : 0987650XXX
Language : En, Es, Fr & De
DOWNLOAD
Book Description :
Abstract: Day to day variation in forage quality, e.g. neutral detergent fiber (NDF) concentration, is substantial on dairy farms, potentially costly, and presents challenges for sampling the forage accurately. We hypothesized that variation in forage NDF concentration (FNDF) and diet variation caused by sampling error will result in decreased milk production over time, affect partitioning of nutrients, and decrease feed efficiency. Twenty-four Holstein cows averaging 73 days in milk were used in 8 concurrent replicated 3x3 Latin squares with 21 d periods. The treatments were 1) Control, 2) Variable, and 3) Overreacting. All 3 treatments were fed similar diets on average, being 24.8% FNDF, 48.2% total forage, and the forage containing 67% alfalfa silage (45% NDF) and 33% grass silage (64% NDF). Control was consistent in total forage, FNDF, and proportion of alfalfa and grass silages fed from day to day. Variable changed daily (random pattern) in proportion of alfalfa and grass silages fed which resulted in a FNDF standard deviation of 2.4 and range of 6.4 over the 21 d period. Overreacting varied in a 5 day cyclic pattern in total forage concentration resulting in a FNDF standard deviation of 2.6 and range of 7.1 over the 21 d period. Overreacting (25.1 kg/d) had higher dry matter intakes (DMI) compared to the Control (24.5 kg/d) and Variable (24.3 kg/d). Milk production (42.8 kg/d) and gross feed efficiency were not affected by treatment. Milk production, diet sorting, DMI, milk urea nitrogen, and milk fatty acid concentrations were affected by treatment by day interactions. Milk fat (3.49%) and protein (2.80%) concentrations were not affected by treatment or treatment by day interactions. Lipolytic and lipogenic enzymes mRNA abundance in subcutaneous adipose tissue were unaffected by treatment, but were generally higher for Variable and Overreacting. Milk fatty acid markers for cellulolytic bacteria (iso-14:0, iso-15:0, iso-16:0), ruminal propionate (15:0) and lipolysis (18:0, long chain fatty acids) were affected by treatment by day interactions and generally followed the expected response to individual day rations and/or DMI changes. Variable had lower DMI and milk production than Control on 4 and 1 d during the 21 d period. In contrast, Variable had higher daily DMI on 1 d and milk production on 3 d compared to Control. Daily DMI for Overreacting was never lower than Control but milk yield was lower on 1 d of the 21 d period. Daily DMI and milk yields were higher on 5 d and 6 d for Overreacting compared to Control. Daily decreases for milk yields by Variable and Overreacting followed sustained 4 and 5 d of feeding a higher FNDF diet compared to Control. In contrast, increased daily milk yields versus Control for Variable and Overreacting were more frequent (3 and 6 d) and responsive to sustained diet changes (3 and 2 d). Cows in peak lactation showed no cumulative negative effects of variable FNDF for DMI, milk production, and gross feed efficiency. Changes of lipolysis indicators suggested the ability was present to buffer short term diet aberrations and/or changing DMI.
