|Roberts, Andrew - Andy|
Submitted to: Western Section of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/15/2011
Publication Date: 6/20/2011
Citation: Waterman, R.C., Roberts, A.J., Endecott, R.L., Petersen, M.K., Geary, T.W., Alexander, L.J., MacNeil, M.D. 2011. First parity evaluation of peak milk yield for range cows developed in the same ecophysiological system but receiving different concentrations of harvested feed inputs. Western Section of Animal Science Proceedings 62:249-252. Interpretive Summary: Previous research has demonstrated that BW, BCS, and productivity of heifers reared on reduced harvested feed input during postweaning development and pursuing winters may be dependent on amount of winter supplemental feed fed to the heifers’ dam, thus indicating the possibility of a uterine programming effect. Research indicates that cows with similar genetic potential for mature weight may have different production efficiencies depending on milk yield. Based on this information our objective for the present research was to evaluate effects of amount of supplement fed to cows during late gestation and level of feed provided to their daughters during postweaning development on first parity milk yield and constituents. This study indicates that a heifer’s dam (in utero) and development/lifetime winter plane of nutrition influenced first parity milk composition but not first parity milk yield. Cows managed on 2 levels of winter harvested feed inputs during late pregnancy may have lifetime influences on their female offspring. Furthermore, a reduction in harvested feed input during heifer development had no detrimental impact on milk yield, milk constituents, or calf BW. Continued research may indicate that reduction in harvested feed during late pregnancy and subsequent heifer development may result in improved economic and production efficiency.
Technical Abstract: Reduction of harvested feed inputs during heifer development could optimize range livestock production and improve economic feasibility. The objective for this two year study was to measure milk production (kg/d) and milk constituent concentrations (g/d) for 16 primiparous beef cows each year that were born from dams receiving adequate or marginal winter supplementation and then developed with ad-libitum or 20% less feed post weaning. Milk production was measured by using a portable milking machine at an average of 28, 42, 56, 70, 84, 98, 112, and 126 d in milk. Milk yield for the 126-d lactation period was determined by the area under the lactation curve using the trapezoidal summation method. Data were analyzed using a model containing dam winter nutrition, heifer development treatment, and their interaction. Total milk yield for the 126-d lactation period, day of peak lactation, and peak lactation yield did not differ between dam nutrition (P = 0.57) or heifer development treatment (P = 0.09). Milk urea N, butter fat, lactose, and solids non-fat did not differ due to dam winter nutrition (P = 0.09) and milk urea N, protein, lactose and solids non-fat did not differ between heifer development (P = 0.09). Milk butter fat was greater (P = 0.04) in heifers receiving ad-libitum feeding during heifer development (212 vs. 182 ± 9.7 g/d, respectively). Heifers born from dams receiving marginal winter nutrition had greater (P = 0.03) milk protein (211 vs. 184 ± 8.3 g/d, respectively). This study suggests that a heifer’s dam and a heifer’s plane of nutrition may influence first parity milk composition but not first parity milk yield.