Submitted to: Southern Association of Agricultural Scientists Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 1/15/2012
Publication Date: 3/30/2012
Citation: Coleman, S.W., Williams, M.J., Chase, C.C., Riley, D.G., Bowers, E.J. 2012. Breed and winter nutrition effects on diet digestibility and intake of cows grazing bahiagrass pastures [abstract]. Southern Association of Agricultural Scientists Proceedings. 90(1):27. Interpretive Summary: Abstract only.
Technical Abstract: Winter feed comprises one of the largest costs for cattle production. This study was initiated to evaluate two winter nutrition programs for cows grazing bahiagrass (Paspalum nutatum) pastures in central Florida. Purebred Angus, Brahman, or Romosinuano cows (30/breed), aged 3 to 13 yrs, were assigned to one of two nutrition regimes. Treatments (WT) began after weaning, continued for two years, and were replicated (R)over the three farms located at STARS. Treatments were: WT1) perennial peanut (Arachis glabrata)/bahiagrass hay fed ad libitum from first frost and supplemented with heavy blackstrap molasses at 2.2 kg/hd/day from weaning until end of breeding; and WT2) bahiagrass hay supplemented with urea-fortified molasses (16% protein equivalent) at 2.2 kg/hd/d from weaning until Jan 15 and then 4.5kg/hd/d of 50% heavy blackstrap molasses and soybean hulls until end of breeding (approximately on June 15). At monthly intervals fecal samples were collected from each cow, dried, ground and scanned for NIR reflectance using a NIRsystems 6500 spectrophotometer. Diet digestibility and DMI were predicted using calibrations developed from feces of other cows grazing the same pastures at various seasons over six subsequent years. Digestibility and DMI data were analyzed with Proc Mixed of SAS. The statistical model included fixed effects of year (Y), cow breed (BR), cowage, WT, month (M) and R. Cow was a repeated observation over months(year). Two- (WTxR; and WTxM) and three-way (YxMxBR and BRxMxR) interactions were significant (P < 0.05) for digestibility and WT x R, YxWTxM, and BRxMxR were significant (P < 0.001)for DMI. Differences in diet digestibility were quite subtle with no consistent patterns. Intake was very high for the WT2 group during the supplementation period, possibly biased by the high level of supplement. Diet digestibility peaked in April and declined through the summer as expected. The data suggest that diet nutritive value and intake predicted from NIR spectra of feces can be used to detect seasonal herbage patterns and diet differences, and may also be sensitive enough to detect breed differences.