Voluntary intake and digestibility by sheep of alfalfa ensiled at different moisture concentrations following fertilization with dairy slurry

Authors: CLARK, J. - UNIVERSITY OF ARKANSAS; COFFEY, K. - UNIVERSITY OF ARKANSAS; COBLENTZ, WAYNE; SHANKS, B. - LINCOLN UNIVERSITY OF MISSOURI; CALDWELL, J. - LAND O' LAKES PURINA FEED, LLC; MUCK, RICHARD; PHILIPP, D. - UNIVERSITY OF ARKANSAS; BORCHARDT, MARK; RHEIN, R. - UNIVERSITY OF ARKANSAS; JOKELA, WILLIAM; BACKES, E. - LAND O' LAKES PURINA FEED, LLC; BERTRAM, M. - UNIVERSITY OF WISCONSIN; SMITH, W. - TEXAS A&M UNIVERSITY

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/14/2017
Publication Date: 4/4/2018
Citation: Clark, J.K., Coffey, K.P., Coblentz, W.K., Shanks, B.C., Caldwell, J.D., Muck, R.E., Philipp, D., Borchardt, M.A., Rhein, R.T., Jokela, W.E., Backes, E.A., Bertram, M.G., Smith, W.B. 2018. Voluntary intake and digestibility by sheep of alfalfa ensiled at different moisture concentrations following fertilization with dairy slurry. Journal of Animal Science. 96:964-974.

Interpretive Summary: Dairy cow manure slurry is used commonly as an animal-sourced fertilizer in agronomic production. However, residual effects of slurry application on intake and digestibility of alfalfa silage from subsequent harvests are not well known. The objective of this study was to determine if the moisture concentration of forage at baling and the timing of dairy slurry application relative to subsequent harvests affected intake and digestibility of baled alfalfa silages by sheep. Treatments consisted of recommended or low moisture of the crop at baling after 1) no slurry application, 2) slurry application to stubble immediately after removal of the previous cutting, or 3) slurry application 14 days after removal of the previous cutting. The results indicate that ensiling alfalfa silage at lower moisture concentrations may tend to improve digestibility without affecting feed intake. Likewise, dairy slurry application as late as 14 days following a previous harvest may not affect intake or digestibility of the following harvest of alfalfa silage. There were numerical reductions in voluntary intake associated with delays in slurry application, but these were not statistically significant. Although some differences were observed in blood measurements, no visible health abnormalities were observed in sheep offered silages baled at different moisture concentrations following varied dairy manure application strategies. Therefore, when alfalfa is baled within the moisture ranges reported within this study, producers may feed fermented alfalfa silages fertilized with dairy slurry without observing any adverse effects on intake, digestibility, or animal health.

Technical Abstract: Dairy slurry is used commonly as an animal-sourced fertilizer in agronomic production. However, residual effects of slurry application on intake and digestibility of alfalfa (Medicago sativa L.) silage from subsequent harvests are not well known. The objective of this study was to determine if moisture concentration of alfalfa silage and timing of dairy slurry application relative to subsequent harvest affected intake and digestibility by sheep. Pregnant crossbred ewes (n = 18; 48 ± 5.3 kg) were stratified by BW and allocated randomly in each of 2 periods to 1 of 6 treatments arranged in a 2 × 3 factorial arrangement. Treatments consisted of recommended (RM; 46.8%) or low (LM; 39.7%) moisture at baling after either no slurry application (NS), slurry application to stubble immediately after removal of the previous cutting (S0), or slurry application 14 d after removal of the previous cutting (S14). Silages were chopped through a commercial straw chopper, packed into plastic trash cans, and then offered to ewes within 4 d of chopping. Period 1 of the intake and digestion study consisted of a 14-d adaptation followed by a 7-d fecal collection period. Period 2 followed period 1 after a 4-d rest and consisted of an 11-d adaptation followed by 7 d of fecal collection. Ewes were housed individually in 1.4 × 4.3-m pens equipped with rubber mat flooring. Feces were swept from the floor twice daily, weighed, and dried at 50°C. Ewes had ad libitum access to water and were offered chopped silage for a minimum of 10% refusal (DM). Dry matter and OM intake and NDF digestibility did not differ (P = 0.13) across moisture or slurry application treatments. However, DM and OM digestibility tended (P < 0.10) to be greater from LM vs. RM. Lymphocytes (% of total white blood cells) were greater (P < 0.05) from LM vs. RM and from NS vs. S0 and S14. Red blood cell concentrations were greater (P < 0.05) from S14 vs. S0 and from S0 and S14 vs. NS. Serum urea N concentrations did not differ (P > 0.17) across treatments. Therefore, moisture concentration of alfalfa silage within the range used in this study and time of dairy slurry application may not affect voluntary intake or NDF digestibility, but moisture concentration may have an effect on DM and OM digestibility. Also, moisture concentration of alfalfa silage and time of dairy slurry application may affect specific blood hemograms.