Nutrition of organic sows

Summary

Organic sows are exposed to a wide range of changes in the environmental conditions (photoperiod, thermoregulation, locomotive activity, and grass/roughage intake), and their lactation period is twice as long compared to indoor sows. Nutrient recommendations for organic sows are, however, based on knowledge obtained for indoor sows.Two experiments were included in this Ph.D project to determine the energy- and protein intake from grazing and to quantify the energy needed for maintenance, maternal retention, mobilisation, milk production, thermoregulation, and locomotive activity in organic sows. The first experiment included sixteen sows fitted with urinary catheterized and kept in metabolic cages to study the effect of increasing intake of fresh grass-clover on plasma - and urine metabolites, estimate the grass-clover digestibility in sows, and to identify possible biomarkers for grass-clover intake in organic sows. The second experiment included forty-seven free-range gestating and lactating sows, who were randomly assigned into either a control group with “normal” protein concentration in the compound feed or a low protein group, where the protein content was reduced by 12% in both gestation and lactation diets. Two parities were studied, which were confounded with winter and summer seasons, and therefore published in separate papers. The two dietary strategies were adjusted to be iso-energetic and were of 100% organic origin. To meet the extra demand for thermoregulation and physical activity, the energy allowance from both treatments was increased by adding 15% to the recommended energy level for indoor sows in winter and + 10% in summer. Fresh grass-clover intake of sows was highly correlated with plasma pipecolic acid and plasma bisnorbiotin concentrations. Apparent total tract digestibility of dry matter, organic matter, nitrogen, and energy of grass-clover was 64%-72% using the regression method, and the excretion of nitrogen in urine was highly correlated with grass-clover intake. The main challenge during lactation was a limited feed intake capacity. The actual feed intake was only 2/3 of the fed amount in the first three weeks of lactation, and sows mobilised more than 1 kg of body fat per day in the period from day 5 to day 20 in lactation in both seasons. Body fat loss was particularly critical during winter as sows need fat for insulation. and their energy intake was not sufficient for gilts under Danish winter conditions, even though it was a mild winter. In pregnancy, sows walked 1.9-2.5 kilometers per day and spent 3.9-4.8 MJ ME on physical activity. The covered distance in early lactation was 704 meters/d, at peak lactation 1482 m/d, and in late lactation 1644 m/d. Energy consumption for thermoregulation during winter was much higher than for physical activity, and the energy requirement for locomotive activity in organic sows was relatively low compared to that of indoor animals. For pregnant sows, the intake of grass-clover dry matter was 409 g and 428 g per sow on d60 and d100 as determined by the profile of plasma pipecolic acid. The SID lysine contribution from grass-clover was 3 g/d corresponding to 23% and 17% of the daily SID lysine requirement on d60 and d100 of gestation. In lactation, sows had a daily energy expenditure of 1.4-3.0 MJ ME for locomotive activity, and the mean intake of grass-clover dry matter varied between 225 g/d on day 5 and 574 g/d at peak lactation. The SID lysine intake from grass-clover increased from 1.7g/d to 4.5 g/d with progress of lactation. The total energy requirement at peak lactation was 130 MJ ME/d, and the average energy requirement for thermoregulation was 13.5 MJ ME/d in a mild Danish winter and 5.2 MJ ME/d in a typical summer, which corresponds to 1.0 and 0.4 kg extra feed, respectively. Counterbalancing the contribution of energy and protein from fresh grass-clover enables a deduction of approximately 12% of crude protein in gestation compound feed during summer, without impairing sow productivity, provided that sows have access to a rich grassclover sward. The crude protein content in lactation compound feed should not be reduced to more than 148 g/kg, unless daily feed intake is above 10 kg/d in lactation, as the intake capacity of lactating sows limited the intake of energy and SID lysine in lactation and in turn milk yield and piglet daily gain. In conclusion, it was possible to reduce the dietary protein concentration to pregnant organic sows when the animals had ad libitum access to fresh clover grass in summer and grass silage in winter. Still, dietary protein should not be decreased during lactation.