Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: June 11, 2010
Publication Date: July 12, 2010
Citation: Coleman, S.W., Williams, M.J., Chase, C.C., Riley, D.G. 2010. Breed and winter nutrition effects on body weight, condition, and blood metabolite patterns of cows grazing bahiagrass pastures. Journal of Animal Science Supplement. 88(E Suppl-2):743. Technical Abstract: Economic analysis has revealed that in most parts of the country, the largest economic costs for cattle production are for winter feed. This study was initiated to evaluate the effect of two winter nutrition programs on three breeds of cows grazing bahiagrass pastures in central Florida. Approximately 300 purebred cows, aged 3 to 13 yrs of either Angus, Brahman or Romosinuano breeding, were assigned to one of two nutrition regimes. Treatments (WT) began after weaning and were replicated over the three farms located at STARS, each farm being a replicate (R) and continued for two years. The treatments were: WT1) peanut/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 (~May 15); 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 (~May 15). All cows rotationally grazed (moved twice weekly) bahiagrass pastures year-round. At monthly intervals, all cows were weighed (BW), scored for body condition (BCS), and blood samples collected by jugular puncture from 5 cows per breed/treatment/location group for plasma urea N (PUN), glucose (GLU) and non-esterified fatty acids (NEFA). Data were analyzed on cows that calved using Proc Mixed of SAS. The statistical model included fixed effects of cow breed (BR) , cowage, WT, month (M) and R, ,and year(Y) was random. Cow was a repeated observation over months. Three-way interactions (YxWTxM and YxWTxR) were significant (P < 0.001) for all responses, and the BRxWTxM interaction was significant for BW, BCS, and NEFA. Important differences included: 1) cow BW was always lower for WT2 then WT1 (avg. 505 vs. 487 kg, P< 0.002), especially during winter when supplement was fed, yet PUN was higher (P < 0.01) for WT2 in May, June and Sept-Dec for 2002, but no differences were noted in 2003 until Nov. Plasma levels of NEFA escalated to near 1000 at calving and then declined, but Brahman cows maintained higher levels from April until weaning than the other breeds, probably due to inadequate intake to support milk production.