Model components for the determination of energy and protein requirements for breeding sows: a review

Abstract

Factorial and empirical data from recent work at various research centres provide a quantitative information resource from which nutrient response models may be constructed. Given an initial protein mass (Pt) of some 16.6 kg, breeding sows require subsequently to accumulate protein at rates of around 11.1, 7.8, 4.5 and 2.4 kg per parity. A lipid mass of some 1.5 times the protein mass is consistent with satisfactory reproductive performance, while reproductive efficacy is threatened if the mass of lipid in the breeding sow falls below the mass of protein. Energy requirements for maternal protein and lipid gains appear to be 50 MJ ME kg −1, while amino acid requirements may be modelled from knowledge of ileal digestibility and the efficiency of utilisation post-absorption. Maintenance requirements for energy are probably in the region of 2.51 Pt 0.65 MJ ME daily, while maintenance protein requirements may be estimated as 0.004 Pt. The energy and protein needs have to be added for the gravid uterus, the developing mammary tissues and, especially, lactation; the latter being a function of both potential supply and realised litter demand. The interval between weaning and oestrus is closely related to fatness, particularly in primiparous sows; weaning to oestrus interval (days)=29.3-2.03 P2+0.0433 P2 2, where P2 is the (mm) fat depth 65 mm from the mid-line at the position of the last rib. Changes in P2 fat depth during pregnancy may be estimated as 0.036 total pregnancy food intake-9.3, while change in P2 fat depth during lactation may be estimated as 0.037 total (28 day) lactation feed intake-0.497 number of piglets sucking-0.265 P2 fat depth at parturition-0.283. Litter size and individual piglet birth weight is weakly, but positively, related to maternal live weight. Overall, optimum levels of dietary nutrient supply can be estimated, and the consequences of failure to provide for requirement predicted with regard to both the breeding sow herself and to her productivity.