Results greater acetate propionate Ac Pr ratio. No differ-
196 M
.J. Ranilla et al. Livestock Production Science 62 2000 193 –204
A lag time value of 0 was assumed for the heights were similar for Churra 3.8, 3.6 and 3.5 cm
calculation of DM effective degradability DMED. in June, July and October, respectively and Merino
In situ data were analysed by variance analysis as sheep 3.6, 3.4 and 3.5 cm in June, July and October,
a split-plot design with breed as the main-plot respectively. Animals remained healthy through the
treatment and sampling period as the subplot treat- experimental period and no variations in their BW
ment Steel and Torrie, 1980. Effects for breed, were observed. Marked changes in daily tempera-
sampling period, breed3sampling period, and sheep tures
were registered
during the
experimental within breed were included in the model. Breed
periods, with minimum and maximum temperatures effects were tested using sheep within treatment as
ranging from 6 to 248C, from 13 to 338C and from 5 the error term. The interaction breed3sampling
to 188C for June, July and October, respectively period and the main effect of sampling period were
Table 1. No rain was recorded during any of the tested using residual error. When a significant P ,
sampling periods. 0.05 breed3sampling period interaction was de-
Changes in chemical composition of grazed her- tected, data were analysed within sampling period.
bage through the experimental periods were similar Rumen pH, ammonia-N and VFA data average
for both breeds Table 2. CP content increased from values of two sampling days were analysed as a
June through October for both breeds of sheep, split–split-plot design Steel and Torrie, 1980 with
whereas NDF, ADF and lignin contents declined. sampling time and the interactions breed3sampling
Merino animals tended P ,0.10 to present a period3sampling time and breed3sampling time
lower potential degradability of both DM and NDF added to the model. When significant P ,0.05
of grass hay than Churras Table 3, but no signifi- breed3sampling period3sampling time, breed3
cant differences P .0.05 were detected for ED of sampling period and breed3sampling time interac-
DM and NDF NDFED. tions were detected, which precluded pooling pH,
As significant breed3grazing period3sampling VFA and ammonia-N data across sampling time and
time interactions P ,0.05 were detected for pH, sampling period, these variables were analysed for
ammonia-N and VFA concentrations, mean values each individual sampling period and sampling time.
for these parameters for each breed, grazing period The method of least significant difference was used
and sampling time are presented in Figs. 1–3, to separate treatment means when a significant P ,
respectively. In addition, molar proportions of the 0.05 F-test for treatment was detected. The GLM
main VFA mean values for the day are presented in procedure of SAS 1997 was used for all statistical
Table 4. analyses.
During June, Churras presented higher P ,0.05 pH values at 11.00 and 17.00 h sampling than
Merino sheep, and tended P ,0.10 to present a