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Feeding behavior of lactating dairy cows fed switchgrass (Panicum virgatum) as a replacement for wheat straw in a total mixed ration.

R. L. Nagle




Feeding behavior of lactating dairy cows fed switchgrass (Panicum virgatum) as a replacement for wheat straw in a total mixed ration.
R. L. Nagle*1, B. R. Lemay1, M. Thimmanagari2, T. J. DeVries1, A. J. Carpenter3. 1Department of Animal Biosciences, University of Guelph Guelph, ON, Canada, 2Ontario Ministry of Agriculture, Food and Rural Affairs Guelph, ON, Canada, 3CSA Animal Nutrition Dayton, OH.

The objective of this study was to evaluate the feeding behavior of lactating dairy cows fed switchgrass (Panicum virgatum; SG) as a replacement for wheat straw (WS) in TMR. Two experiments (Exp) were performed where SG replaced WS in TMR for lactating Holstein cattle (n = 24; parity = 2 � 1.2; DIM = 162 � 19.3 and 215 � 21.3, for Exp 1 and 2, respectively). Each Exp consisted of 2 periods in a crossover design, with 11d of adaptation and 10d of sample collection. In Exp 1, either WS or SG were fed in the TMR at 1.8% of diet DM (starch = 22.1 � 1.74% or 20.6 � 2.02% of diet DM, respectively). Cows were fed higher starch rations in Exp 2, with either WS or SG in the TMR at 3.6% of diet DM (starch = 29.6 � 1.54% or 27.6 � 2.45% of diet DM, respectively). Intake was monitored with automated feeders to determine DMI (kg/d), time spent feeding (min/d), total meal time (min/d), meal length (min/meal), meal size (kg/meal), feeding rate (kg/min), meal frequency (meals/d), and the interval between meals (IMI; min/d). Data were analyzed using a mixed-effect linear regression model, with day as a repeated measure. Two cows were excluded from analysis in Exp 1 for health and stealing feed, and 2 cows were excluded from Exp 2 for stealing. In Exp 1, DMI was greater for cows fed SG (25.1 � 0.69 vs. 24.22 � 0.69 kg/d; P ≤ 0.01) as was meal frequency (8.8 � 0.36 vs. 8.1 � 0.36; P ≤ 0.01), but there was no effect on meal size (P = 0.11). Cows on the SG diet had a shorter meal length (37.3 � 2.06 vs. 39.6 � 2.05 min/meal; P = 0.02) and IMI (145.5 � 6.80 vs. 163.1 � 6.69 min/d; P ≤ 0.01). Feeding rate, time spent feeding, and total meal time were not affected (P ≥ 0.14). In Exp 2, DMI (25.0 � 0.65 vs. 25.6 � 0.65 kg/d; P = 0.02) and feeding rate (0.135 � 0.0086 vs. 0.143 � 0.0086 kg/min; P ≤ 0.01) were lesser for cows fed SG. Time spent feeding for cows fed SG was greater (208.3 � 9.11 vs. 201.7 � 9.13 min/d; P = 0.01), but meal frequency, size, length, total meal time, and IMI were not affected (P ≥ 0.56). In conclusion, feeding behavior was affected by inclusion of SG in TMR, however, the response varied depending on dietary starch level and inclusion of SG.

Keywords: switchgrass, feeding behavior, starch.

Biography: I graduated with a Bachelor of Science in Agriculture, Animal Sciences at the University of Guelph. I am a current master student studying dairy nutrition in the department of Animal Biosciences at the University of Guelph. My true passion for the dairy industry started when I was in high school working on a dairy operation. My research has focused on feeding switchgrass as a replacement for wheat straw in high-starch total mixed rations to lactating dairy cows. In the future I hope to use my knowledge to advance the dairy industry.