Body minerals content of reproductive sows
Résumé
Minerals are essential for the development and maintenance of the skeletal system as well as for many essential
physiological functions. The factorial determination of minerals requirement is generally based on potential total
body minerals retention as driving force. However, only very limited information is available in reproductive sows,
data from fattening pigs being often used, which makes the predictions unprecise. Complete dissection (lean, fat,
bones, skin, organs) was performed on 189 sows, among which 23 were also chemically analysed. Body minerals and protein contents were determined in all sows using the double-regression technique. Sows were from different parities and different physiological status: 42 and 66 primiparous sows at farrowing and at weaning, and 25 and 56 multiparous sows at mating and at farrowing, respectively. Body minerals weight (BM) was greater (P<0.001) in multiparous (6.99 kg) than in primiparous sows (4.87 kg) and differed according to physiological status in primiparous (lower at weaning than at farrowing, 4.68 vs 5.07 kg), but not in multiparous sows. When expressed per kg empty body weight (EBW), body minerals content was higher (P<0.01) in multiparous sows at mating (33.8 g/kg EBW) than in the others groups which did not differed among each other (29.2 g/kg EBW on average). When expressed per kg body protein, differences among groups almost disappeared (193 to 198 g/kg BP for extreme values). The prediction equation of BM content (kg) was more precise with body protein (BP, kg) as predictor [BM = 0.258 (±0.065) + 0.187 (±0.002) BP; R2=0.97] than with EBW (kg) as predictor [BM = 0.330 (±0.194) + 0.028 (±0.001) EBW; R2=0.81]. This was partly related to body fat tissues content which varied according to the physiological status of sows (from 17 to 23% of carcass weight). Indeed, when backfat thickness (P2, mm) was included in the equation, the precision of the prediction equation based on EBW increased: [BM = 0.978 (±0.165) + 0.0318 (±0.0007) EBW – 0.105 (±0.008) P2; R2=0.90]. It is concluded that body protein mass is a better predictor of body minerals mass than EBW. However, although less precise, the use of EBW and P2 as predictors could be an interesting alternative and easier to apply in practice.