Determination of energy and protein requirements for maintenance and lactation of Dorper × Hu crossbred sheep

• Published in: Small ruminant research Vol. 190; p. 106162
• Main Authors: Fan, YX, Wang, ZB, Nie, HT, Ma, TW, Wang, ZY, Wang, Feng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-09-2020
• Subjects: Lactation; Metabolizable energy; Metabolizable protein; Net energy; Net nitrogen; Nutrient requirement; Metabolizable protein; Nutrient requirement; Net nitrogen; Metabolizable energy; Lactation; Net energy
• ISSN: 0921-4488; 1879-0941
• DOI: 10.1016/j.smallrumres.2020.106162

•The Wood’s model showed adequate estimates of peak yield.•An overestimate in milk yield before and after the point of milk yield reached peak.•An underestimate time at peak yield compared with the observed milk curve.•Confirmed MP and ME requirement for lactation of Dorper and Hu crossbred sheep.
This study set out to define the energy and protein requirements for maintenance and lactation of Dorper☓Hu crossbred lactating ewes. Eighteen ewes of similar weight (53.37 ± 1.18 kg) were randomly divided into three groups after parturition: ad libitum (AL), IR70 % (intake restricted to 70 % of AL), and IR50 % groups (intake restricted to 50 % of AL). Energy, nitrogen, and carbon balance were calculated by determining the carbon or nitrogen content of orts, feces, urine, milk, CH4, and CO2 samples in digestibility and respiratory trials. Maintenance requirements of net energy [NEm; 257.04 ± 1.15, 252.35 ± 1.08, 244.34 ± 1.15 kJ/kg body weight (BW)0.75/day]; metabolizable energy (MEm; 353.29 ± 3.27, 352.16 ± 3.54, 354.97 ± 2.67 kJ/kg BW0.75/day); net nitrogen (NNm; 326 ± 110, 306 ± 81, 285 ± 77 mg/kg BW0.75/day); and net protein (NPm; 2.03 ± 0.17, 1.91 ± 0.28, 1.78 ± 0.28 g/kg BW0.75/day) were observed on 20th, 50th and 80th day of lactation. Compared with these results, the Wood’s model showed adequate estimates of peak yield (0.88 vs. 0.87 kg/day), but an overestimation of milk yield either side of the peak, and an underestimation of the timing of peak yield compared with the observed milk curve in the current study (4th vs. 3rd week of lactation, respectively). The corresponding NE requirements for lactation (NEL; MJ/kg milk) linearly increased with progressing lactation and were scaled from 3.76 to 4.19 (MJ/kg milk). Additionally, milk yield varied from 1–3 kg daily, and, from 20th to 80th day of lactation, the daily metabolizable protein (MP) requirement for lactation ranged from 141.14–283.43 g/day. The combined results suggest that the estimated MP and ME requirements for lactating Dorper and Hu crossbred sheep fell between the NRC recommendations for lactating ewes suckling a singleton and twin lambs.