Effects of two 100% organic diets differing in proportion of home-grown components and protein concentration on performance of lactating sows
Diets for lactating sows in organic farming are frequently not sufficient in their content of indispensable amino acids, as most organic farms cannot produce the required high-quality protein-rich feedstuffs, but have to purchase them instead. This study was conducted to examine the effects of 2 lactation diets (High; Low) on the reproductive performance of 36 sows (18 sows each receiving diet High and Low) over up to 4 consecutive lactation periods. Diets differed both in proportion of purchased components (as opposed to home-grown) and protein content. We have hypothesized, that reproductive performance of sows would be better when feeding the diet with more purchased components and greater protein content (High), than when feeding the low-protein diet (Low). Feeding diet Low had no negative effect on sows´ performance; average feed intake was high (7.4 and 6.9 kg/d for diets High and Low, respectively; P=0.071), and total live weight loss was within an acceptable range. The average litter consisted of 7.7 (High) and 8.4 (Low) piglets at weaning (P=0.152), weighing 12.0 and 11.3 kg, respectively (P=0.112). In litters with 10 or more weaned piglets, feed intake of the sows was lower (P=0.069) and weight loss was greater during 1–2 wk postpartum (P=0.027) when diet Low was fed as compared with diet High. Blood metabolites did not indicate increased protein mobilization, but greater concentrations of non-esterified fatty acids and blood urea in sows fed diet High were interpreted as signs of increased amino acid breakdown, especially in litters of 10 or more piglets (P=0.015 and 0.003, respectively). We conclude that feeding mainly home-grown components to lactating sows with rather small litters is feasible without substantially impairing performance. Sows with larger litters, however, reacted more sensitively to the low-protein diet, and feeding it over several reproductive cycles might eventually impair their performance.