Table 4.
Nitrogen utilization between days 13 and 17 of lactation (peak lactation) for primiparous sows fed control or low-protein diets
| Item | Diet | NRC (2012) 1 | SEM2 | P value | |
|---|---|---|---|---|---|
| CON3 | LCP | ||||
| Number of sows4 | 13 | 11 | — | — | |
| Sow body weight change, kg/d | −0.62 | −0.87 | 0.29 | 0.498 | |
| N intake, g/d | 153.2 | 122.7 | 1.7 | <0.0001 | |
| Apparent fecal N digestibility, % | 88.9 | 85.8 | 0.7 | 0.0002 | |
| Total N excretion, g/d | 55.9 | 33.1 | 3.0 | <0.0001 | |
| Fecal N, g/d | 17.0 | 17.3 | 0.8 | 0.720 | |
| Urinary N, g/d | 38.6 | 15.9 | 2.5 | <0.0001 | |
| N absorbed, g/d5 | 136.2 | 105.5 | 2.2 | <0.0001 | |
| N retention, g/d6 | 97.2 | 89.7 | 3.9 | 0.067 | |
| True milk protein N, g/d7 | 73.8 | 80.2 | 3.0 | 0.142 | |
| Maternal N retention, g/d8 | 24.6 | 13.5 | 3.7 | 0.045 | |
| N retained, % of intake | 63.5 | 72.9 | 2.4 | 0.001 | |
| N retained, % of absorbed | 71.6 | 84.7 | 2.2 | 0.0001 | |
| True milk protein N output, % of retained N9 | 75.4 | 86.0 | 3.5 | 0.040 | |
| AA utilization efficiency, %10 | |||||
| Arg | 37.2 | 61.4 | 81.6 | 2.4 | <0.0001 |
| His | 64.7 | 69.8 | 72.2 | 2.7 | 0.100 |
| Ile | 54.6 | 64.1 | 69.8 | 2.5 | 0.002 |
| Leu | 53.8 | 65.9 | 72.3 | 2.5 | 0.0002 |
| Lys | 76.6 | 77.1 | 67.0 | 3.0 | 0.877 |
| Met | 63.8 | 53.0 | 67.5 | 2.2 | 0.0003 |
| Met + Cys | 64.9 | 66.9 | 66.2 | 2.6 | 0.494 |
| Phe | 45.6 | 45.0 | 73.3 | 1.7 | 0.750 |
| Phe + Tyr11 | 57.0 | 65.7 | 70.5 | 2.5 | 0.004 |
| Thr | 65.2 | 65.2 | 76.4 | 2.6 | 0.996 |
| Trp11 | 64.0 | 58.7 | 67.4 | 2.4 | 0.050 |
| Val | 53.8 | 53.1 | 58.3 | 2.1 | 0.747 |
| N | 67.5 | 85.1 | 75.9 | 3.0 | <0.0001 |
1Biological maximum AA utilization efficiency for milk protein production for groups of sows according to the NRC (2012).
2Maximum value of the SEM.
3CON = control, 16.2% CP (as-fed; analyzed contents); LCP = low crude protein, 12.7% CP.
4Variables dependent on milk yield (i.e., true milk protein N, maternal N retention, and efficiency of retaining N in true milk protein) are based on 9 and 8 sows for CON and LCP diets, respectively.
5N intake − N excreted in feces.
6N intake − N excreted in feces − N excreted in urine.
7Calculated based on true protein content of milk (day 16) and milk yield estimated via weigh-suckle-weigh on day 17 of lactation.
8N retention − true milk protein N output.
9Retained N includes N retained in maternal and milk protein pools.
10AA utilization efficiency for milk production across the 17-d lactation period calculated according to the NRC (2012) using analyzed dietary AA concentration and estimated digestibility (NRC, 2012).
11Calculated values for dietary Tyr and Trp, respectively, were used for the AA utilization efficiency calculation.