Table 1.
Nutrient content of dietary rations fed to dams during each trimester of gestation (T1=36 to 90 dpc, T2=90 to 180 dpc or T3=181 to term) by treatment (high or low)
| T1 | T2 | T3 | |||
|---|---|---|---|---|---|
| (36 to 90) | (90 to 180) | 181 to term | |||
| Feed sources | High | Low | High | Low | All cows |
| Hay (kg) | – | 3.74 | – | 4.00 | – |
| Pasture (kg) | 5.72 | – | 6.00 | – | 7.20 |
| Sorghum (kg) | – | 2.61 | – | 2.61 | – |
| Copra meal (kg) | 1.80 | – | 1.80 | – | – |
| Calcium (g/kg) | 1.10 | 2.60 | 1.10 | 2.60 | 1.10 |
| Phosphorus (g/kg) | 9.20 | 5.20 | 9.20 | 5.20 | 9.20 |
| DMI total 1 | 7.52 | 6.35 | 7.80 | 6.61 | 7.20 |
| Energy intake (MJ) | 70.50 | 57.50 | 72.20 | 64.00 | 63.40 |
| Energy (%NRC 2 ) | 100.00 | 90.00 | 103.00 | 92.00 | 101.00 |
| CP (kg) | 1.18 | 0.38 | 1.22 | 0.40 | 0.99 |
| CP (%) | 15.70 | 5.98 | 15.64 | 6.05 | 13.70 |
| CP (%NRC) | 174.00 | 66.00 | 179.00 | 70.00 | 125.00 |
Data are presented on an as-fed dry matter (DM) basis per heifer per day.
Estimates of DMI from pasture and hay were calculated based upon the National Research Council (NRC) energy requirements for replacement Bos taurus pregnant heifers with a mature weight of 500 kg and a calf birth weight of 32 kg. As the sorghum and copra meal energy content were known (12 and 11.2 MJ/kg DM, respectively) and the heifers on the low-protein diet averaged 340 kg with a rate of gain of 0.8 kg during the first trimester, the DMI of pasture and hay was calculated based upon the energy requirement sufficient to sustain this rate of gain. Similar DMI estimations were completed in the second and third trimesters based on the rate of gain in each treatment group.
NRC comparison to ration to NRC (1996) recommended nutrient requirements for pregnant yearling Bos taurus replacement heifers with calf weight of 32 kg.