Date of Award:

5-2017

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Animal, Dairy, and Veterinary Sciences

Committee Chair(s)

Jong-Su Eun

Committee

Jong-Su Eun

Committee

Allen J. Young

Committee

Jennifer W. MacAdam

Abstract

Legumes that contain condensed tannins (CT) may have lower protein degradability than alfalfa. The present study investigated the effects of feeding birdsfoot trefoil (Lotus corniculatus L.) hay on lactation performance and N utilization. Eight multiparous Holstein cows in mid lactation (150 ± 22.3 d-in-milk) were randomly assigned to 1 of 2 rations [alfalfa hay-based TMR (AHT) or birdsfoot trefoil hay-based TMR (BFTT)] in a crossover design with 2 experimental periods. Each experimental period lasted 16 d (14 d of adaptation and 2 d of total collection), and the 2 experimental periods were separated by a 7-d washout period. In the experimental diets, alfalfa hay or birdsfoot trefoil hay was included at 50% DM to AHT or BFTT, respectively. There were no treatment effects on DMI (21.4 vs. 20.7 kg/d; P = 0.46), milk yield (29.4 vs. 28.1 kg/d; P = 0.47), milk fat concentration (3.20 vs. 3.21%; P = 0.67), and milk protein concentration (3.20 vs. 3.16%; P = 0.35) for AHT and BFTT, respectively. In addition, dietary treatments did not affect milk yield/DMI (P = 0.59) and energy-corrected milk yield/DMI (P = 0.49). In contrast, CP digestibility decreased in BFTT compared with AHT (69.1 vs. 60.7%; P < 0.01). Concentration of milk urea-N decreased by feeding BFTT compared with feeding AHT (11.9 vs. 13.3 mg/100 mL; P < 0.01), whereas total N excretion was similar (P = 0.82) between the diets. However, cows fed BFTT excreted more N in feces (194 vs. 168 g/d; P < 0.01), in contrast urinary N excretion decreased in BFTT cows compared to AH treatment (P < 0.01), leading to a decrease in urinary-N:fecal-N ratio (P = 0.03) in cows fed BFTT relative to those fed AHT. Overall results in the current study suggest that feeding BFT hay in dairy diet with a relatively great concentration (50% DM) did not affect overall lactational performance, whereas it shifted routes of N excretion evidenced by the decreased urinary-N:fecal-N ratio compared with feeding alfalfa hay. The positive impact on environment may be attributed to a functional effect of CT as well as a unique cell wall structure of birdsfoot trefoil.

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