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United States Department of Agriculture

Agricultural Research Service

Research Project: Adaptive Rangeland Management of Livestock Grazing, Disturbance, and Climatic Variation

Location: Livestock and Range Research Laboratory (LARRL)

Title: Individual mineral supplement intake by ewes swath grazing or confinement fed pea-barley forage

Authors
item Ragen, D -
item Nix, E -
item Endecott, R -
item Hatfield, P -
item Petersen, Mark
item Bowman, Jg -

Submitted to: Western Section of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: July 1, 2012
Publication Date: July 15, 2012
Citation: Ragen, D.L., Nix, E.E., Endecott, R.L., Hatfield, P.G., Petersen, M.K., Bowman, J.P. 2012. Individual mineral supplement intake by ewes swath grazing or confinement fed pea-barley forage. Western Section of Animal Science Proceedings 63:103-107.

Interpretive Summary: Sixty mature ewes (non-pregnant, non-lactating) were used in a completely randomized design to determine if feeding method of pea-barley forage (swath grazing or hay in confinement) had an effect on individual ewe mineral consumption. Thirty ewes were randomly allocated to 3 confinement pens and 30 ewes were randomly allocated to 3 grazing plots. The study was conducted during Sept. 25 to Oct. 15, 2010 and repeated Sept. 6 to 19, 2011. Targhee ewes (65.4 ± 5.84 kg BW) were used in 2010. Rambouillet ewes (61.9 ± 6.28 kg BW) were used in 2011. Ewes had ad libitum access to food, water, and a mineral supplement containing 12% salt with 2% titanium dioxide (TiO2) added as an external marker to estimate individual mineral intake. On d 1 of the study, mineral was weighed and placed in covered feeders in pens and plots. Mineral was weighed and added as needed and at the end of the collection period, remaining mineral was weighed to provide an estimate of total mineral intake via disappearance. Forage DMI was calculated using estimates of fecal output, obtained by dosing gelatin capsules containing 2 g chromic oxide (Cr2O3) every day for 14 d, and in vitro 48 h forage DM digestibility. Fecal grab samples were collected from each individual ewe for 7 d and composited by ewe. Forage and mineral intakes were analyzed using individual ewe as the experimental unit, while plot or pen was used as the experimental unit for intake CV. A year x treatment interaction (P < 0.01) existed for forage and mineral DMI. Ewes in confinement pens consumed more forage than grazing ewes in 2010 (2.60 vs. 1.86 kg•ewe-1•d-1, respectively), but less than grazing ewes in 2011 (1.99 vs. 2.49 kg•ewe-1•d-1, respectively). Mean mineral intake was highest (P < 0.01) by grazing ewes in 2011 and 2010 (average 69 g•ewe-1•d-1), intermediate by ewes in pens in 2010 (57 g•ewe-1•d-1), and lowest by ewes in pens in 2011 (31 g•ewe-1•d-1). A year x treatment interaction (P = 0.05) existed for mineral DMI CV which was greater (P = 0.04) for the pen treatment in 2011 (67 vs. 34%) but not different (P > 0.05) between treatments in 2010. In this study, both swath grazing ewes and ewes in confinement consumed more mineral than recommended by the mineral manufacturer and the NRC indicating that more research is needed to develop a better understanding of the factors that regulate and impact mineral intake.

Technical Abstract: Sixty mature ewes (non-pregnant, non-lactating) were used in a completely randomized design to determine if feeding method of pea-barley forage (swath grazing or hay in confinement) had an effect on individual ewe mineral consumption. Thirty ewes were randomly allocated to 3 confinement pens and 30 ewes were randomly allocated to 3 grazing plots. The study was conducted during Sept. 25 to Oct. 15, 2010 and repeated Sept. 6 to 19, 2011. Targhee ewes (65.4 ± 5.84 kg BW) were used in 2010. Rambouillet ewes (61.9 ± 6.28 kg BW) were used in 2011. Ewes had ad libitum access to food, water, and a mineral supplement containing 12% salt with 2% titanium dioxide (TiO2) added as an external marker to estimate individual mineral intake. On d 1 of the study, mineral was weighed and placed in covered feeders in pens and plots. Mineral was weighed and added as needed and at the end of the collection period, remaining mineral was weighed to provide an estimate of total mineral intake via disappearance. Forage DMI was calculated using estimates of fecal output, obtained by dosing gelatin capsules containing 2 g chromic oxide (Cr2O3) every day for 14 d, and in vitro 48 h forage DM digestibility. Fecal grab samples were collected from each individual ewe for 7 d and composited by ewe. Forage and mineral intakes were analyzed using individual ewe as the experimental unit, while plot or pen was used as the experimental unit for intake CV. A year x treatment interaction (P < 0.01) existed for forage and mineral DMI. Ewes in confinement pens consumed more forage than grazing ewes in 2010 (2.60 vs. 1.86 kg•ewe-1•d-1, respectively), but less than grazing ewes in 2011 (1.99 vs. 2.49 kg•ewe-1•d-1, respectively). Mean mineral intake was highest (P < 0.01) by grazing ewes in 2011 and 2010 (average 69 g•ewe-1•d-1), intermediate by ewes in pens in 2010 (57 g•ewe-1•d-1), and lowest by ewes in pens in 2011 (31 g•ewe-1•d-1). A year x treatment interaction (P = 0.05) existed for mineral DMI CV which was greater (P = 0.04) for the pen treatment in 2011 (67 vs. 34%) but not different (P > 0.05) between treatments in 2010. In this study, both swath grazing ewes and ewes in confinement consumed more mineral than recommended by the mineral manufacturer and the NRC indicating that more research is needed to develop a better understanding of the factors that regulate and impact mineral intake.

Last Modified: 4/16/2014
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