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Thesis - University Access Only
Master of Science (MS)
The objective of the first study was to measure physiological and production responses, and milk production efficiency of lactating dairy cows when fed diets containing high (HiLA) or low (LoLA) amounts of linoleic acid (LA) provided by dried distillers grains with solubles and high (Hpef) or low (Lpef) physically effective neutral detergent fiber (peNDF) provided by alfalfa hay or alfalfa pellets. All diets (in Period 2 only) were then fed with or without the addition of Monensin (MON). Sixty four lactating Holstein dairy cows (65 - 250 DIM) were used in a 12-week randomized complete block design consisting of a Covariate Period (weeks -3 to 0), Period 1 (weeks 1-4), and Period 2 (weeks 5-10). During the Covariate Period, all cows received a common diet. In Period 1, cows were blocked according to parity, milk production, days in milk and were randomly assigned to one of four diets: 1) low linoleic acid, high pef (LoLA-Hpef); 2) low linoleic acid, low pef (LoLA-Lpef); 3) high linoleic acid, high pef (HiLA-Hpef); and 4) high linoleic acid, low pef (HiLA-Lpef) in a 2 × 2 factorial arrangement of treatments. In Period 2, half of the cows on each diet in Period 1 were randomly assigned to be fed MON resulting in a 2 × 2 × 2 factorial arrangement of treatments. Diets in Period 2 containing MON were formulated to contain approximately 22 g/ton of Monensin (Rumensin®,Elanco Animal Health, Greenfield, IN). All diets were formulated for a 50:50 forage to concentrate ratio and a 25:75 hay to corn silage ratio. Cows fed the HiLA diets tended to increase milk yield and milk protein yield but had less milk fat percentage and yield than did cows fed LoLA diets. Cows fed diets with Lpef lowered milk fat percentage and yields, but did not affect other production measures. The addition of MON had no effect on intake, milk yield or milk composition with the exception of a lower lactose percentage. There was a tendency for an interaction of pef × LA × MON for milk protein percentage. There were no interactions for the dietary factors of pef, LA, and MON for any of the production measures evaluated during this experiment. Cows receiving HiLA diets had more C18:2 t-10 c-12, preformed, LCFA, MUFA, PUFA and less de novo, C16 carbon, SCFA, MCFA, and SFA when compared to cows receiving LoLA diets. Cows receiving Hpef diets had more SFA and less MUFA and PUFA when compared to cows receiving Lpef diets. There were no effects from pef or the interaction of pef×LA×MON on milk fatty acid profile. Cows receiving HiLA diets had more LPS (endotoxin) than cows receiving LoLA diets. Cows receiving Hpef diets had less LPS as opposed to cows receiving Lpef diets. There were no pef×LA×MON on LPS concentration. There were no effects from pef, LA, or MON on TNF-α or CRP. These results allow us to conclude that cows that received the HiLA diets had milk fat depression, an altered milk fatty acid profile, and endotoxin release,indicating an immune response. The objective of the second study was to measure the FRAP and LPC responses of lactating dairy cows when fed diets containing HiLA or LoLA amounts of LA provided by dried distillers grains with solubles and Hpef or Lpef peNDF provided by alfalfa hay or alfalfa pellets. There were no effects from pef, LA, or the interaction of pef, LA, or MON for FRAP or LPC. However, cows receiving MON diets had less LPC than the cows receiving No MON diets. This indicates that FRAP and LPC are unaffected by peNDF or LA levels, however, the inclusion of MON negatively affect the growth of gram-positive bacteria in LPC in milk. Thus, from these two experiments, we can conclude that when cows are fed HiLA containing diets, milk fat depression may occur, causing an alteration in milk fatty acid profile and an immune response, without effecting the FRAP qualities of the milk.
Library of Congress Subject Headings
Dairy cattle--Feeding and feeds
Antibiotics in animal nutrition
Corn as feed
Fiber in animal nutrition
Includes bibliographical references (pages 136-154)
Number of Pages
South Dakota State University
In Copyright - Educational Use Permitted
Smith, Megan Lillis, "Monensin in Dairy Cow Diets Containing High and Low Levels of Linoleic Acid from Corn Distillers Grains and High and Low Fractions of Physically Effective Neutral Detergent Fiber" (2013). Electronic Theses and Dissertations. 1640.