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Pre-grazing herbage mass (kg DM/ha) and pasture allowance (kg DM/ewe/d) were measured
using a rising plate meter placed in 25 random locations throughout the paddock. The plate
meter (1,254 g and 0.16 m 2 ) was calibrated to each pasture by correlating the DM and rising
plate reading of 20 clipped samples, as described by Bransby et al. (1977). Pasture calibration
was repeated twice in early and mid-grazing season to account for changes in pasture
composition and maturity over time. Post-grazing pasture residue was estimated once per week
with the rising plate meter to verify sufficient pasture allowance.
Marker. Titanium dioxide (TiO2) was used as an external marker to estimate pasture intake
of ten ewes randomly selected from each supplementation treatment. A pre-treatment fecal
sample was taken from ewes in each treatment before administration of the marker. Gelatin
capsules of 2.5 g of TiO2 were administered to ewes twice daily for 11 days. After a seven day
adjustment period, fecal grab samples were collected once per day, at 1630 h, for the following
four days. A compiled fecal sample for each ewe was stored frozen and subsequently oven dried
(60º C forced-air for 48 h) and ground to pass through a 1-mm screen in a UDY cyclone mill.
Fecal samples were analyzed for the concentration of TiO2 using the colorimetric technique
described by Myers et al. (2004). Total fecal output (FO; g/d) was estimated by the equation:
FO = (g TiO2 administered per d) / (g TiO2 /g feces DM)
Forage fecal output (FFO) was equal to FO for unsupplemented ewes. For supplemented ewes,
FFO was estimated by subtracting the estimated fecal output of grain (0.82 kg grain * 97 % DM
* 90 % digestibility) from the total FO. Based on FFO, pasture DMI was estimated using the
equation:
Pasture DMI = FFO x (100/100-DMDpasture)
Fecal and forage samples were analyzed for acid detergent lignin (ADL), using the technique of
Robertson and Van Soest (1981), to determine apparent forage digestibility:
Dry matter digestibility (DMD) = 100 – ((% ADL forage / % ADL fecal) * 100)
For unsupplemented ewes, pasture DMI represents total DMI. For supplemented ewes, total
DMI was estimated by adding pasture DMI to grain DM (0.82 kg/d * 97 % DM) offered in the
parlor.
Statistical analyses. Weekly milk production, bi-weekly fat and protein percentage, BW
and BCS were analyzed using the mixed model procedure of SAS 8.2 (PROC MIXED) for a
factorial design (SAS, 1999) with repeated measures. The model for these repeated measures
included the fixed effects of stage of lactation, supplementation treatment, test date and their
two- and three-way interactions, and the random effects of ewe and the residual. The general
linear model procedure of SAS (PROC GLM) was used to analyze DMI and the total trial period
production of milk, fat, protein, FCM and FPCM, and percentage of fat and protein. The model
included the effects of stage of lactation, supplementation treatment, their interaction, and the
residual. All means presented are least squares means, and significance is declared at P < 0.05
unless otherwise noted. Forage CP was related to MUN using the correlation procedure of SAS
(PROC CORR).
Results and Discussion
Milk production and composition. Figure 1 presents average test day milk yields for each
of the four stages of lactation and supplementation treatment combinations. On the first test day,
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