The incorporation of feed-use (FU) amino acids (AAs) in diets results in a reduced use of protein-rich ingredients such as soybean meal, recognized to have elevated contributions to environmental impacts. This study investigated whether the incorporation of L-lysine.HCl, L-threonine and FU-methionine reduces the environmental impacts of pig and broiler feeds using Life Cycle Assessment. The following impact categories were considered: climate change, eutrophication, acidification, terrestrial ecotoxicity, cumulative energy demand and land occupation. Several feeds were formulated either to minimize the cost of the formulation (with or without AA utilization), to maximize AA incorporation (i.e. the cost of AA was considered to be similar to that of soybean meal), or to minimize greenhouse gas emissions. For both pig and broiler feeds, calculations were made first using only cereals and soybean meal as main ingredients and then using cereals and several protein-rich ingredients (soybean meal, rapeseed meal and peas). In addition, these calculations were performed using two types of soybean meal (from Brazil, associated with recent deforestation or not). For broiler feeds, two types of maize (from France, irrigated, with mineral fertilization v. not irrigated, with animal manure fertilization) were also tested. Regarding the feeds formulated to minimize cost, incorporation of AA decreased the values for eutrophication, terrestrial ecotoxicity and cumulative energy demand of both pig and broiler feeds, regardless of the base ingredients. Reduction in climate change and acidification due to the incorporation of AA depended on the nature of the feed ingredients, with the effect of AA incorporation being greater when combined with ingredients with high impacts such as soybean meal associated with deforestation. Feeds formulated to maximize AA incorporation generally had a similar composition to those formulated to minimize cost, suggesting that the costs of AA were not the limiting factor in their incorporation. Feeds formulated to minimize greenhouse gas emissions had the lowest values for climate change and cumulative energy demand, but not for other impacts. Further research is needed to elucidate whether the incorporation of additional AA (tryptophan and valine) along with L-lysine, L-threonine and FU-methionine could decrease on the environmental impacts of pig and broiler feeds further.

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The aim of this experiment was to investigate whether insulin resistance is related to the dietary concentration of Trp and the ADFI of primiparous sows having similar body conditions. Twenty-four primiparous sows were catheterized on d 97 of pregnancy. Blood samples were collected during 3 tests: after the ingestion of 1.5 kg of feed (meal test), after the intravenous infusion of 0.5 g of glucose/kg of BW (glucose tolerance test), and during an euglycemic hyperinsulinemic clamp with an infusion rate of 100 ng of insulin x kg of BW(-1) x min(-1). Both tests were performed at 4 stages at approximately d 103 and 110 of pregnancy and at d 3 and 10 of lactation. Sows were fed a diet containing 0.16 or 0.26% of total Trp (suboptimal vs. slight excessive Trp supply according to recommendations for lactating sows) from d 104 of pregnancy after the first clamp until weaning. The dietary treatment did not result in differences in ADFI, BW, and backfat changes, and growth of piglets during lactation. Plasma Trp concentration was greater for the sows allocated to the slight excessive Trp diet than for the sows allocated to the suboptimal Trp diet (P < 0.05). Plasma glucose, NEFA, and urea profiles during the meal tests were not affected by the dietary treatment. At d 3 of lactation, the insulin concentration at 105 (P = 0.03) and 120 min (P = 0.04) after meal intake was less for the sows allocated to the slight excessive Trp diet than for the sows allocated to the suboptimal Trp diet. On d 10 of lactation, the glucose half life (P = 0.03) and the time needed to reach 25% of the area under the insulin curve (P = 0.04) during the tolerance test were less for the sows allocated to the slight excessive Trp diet than for the sows allocated to the suboptimal Trp diet. The glucose infusion rate during euglycemic hyperinsulinemic clamps was similar in the 2 Trp groups of sows. Irrespective of the dietary treatment, the ADFI of the sows was negatively related to the glucose half life during the glucose tolerance test and positively related to the glucose infusion rate during the clamp (P < 0.05). This relationship observed with the tests performed during early lactation was already found with the tests performed during late pregnancy (P < 0.02). Present findings indicate that a dietary Trp supply of 0.26% does not increase feed intake in lactating primiparous sows. This result indicates that the interest in a Trp supplementation during the peripartum period can be questioned. Irrespective of the dietary treatment, the reasons why sows with similar rearing conditions develop different rates of insulin resistance during pregnancy remain to be elucidated.

Voluntary feed intake in sows after parturition may be related to the capacity of the sow to cope with the numerous changes occurring around farrowing. This experiment was undertaken to investigate whether the feed intake during lactation was related to the reactivity of the sow during gestation and plasma Trp and cortisol concentrations. On d 58 of pregnancy, 37 sows were individually placed in a novel environment, and their behavior was observed during a 5-min open-field test. This test allowed the selection of 12 reactive (R) and 8 nonreactive (NR) sows for the study. Sows were fed 3 kg of a standard gestation diet/d before farrowing and a standard lactation diet ad libitum thereafter. The behavioral reactivity of sows when a human touched their neck in the farrowing crate was evaluated on d 72 of gestation, and their behavior during farrowing was analyzed. Sows were catheterized on d 70 of gestation, and blood samples were taken after an overnight fast on d 37 before farrowing, daily during the week before and the week after parturition, and on d 14 and 21 of lactation for plasma Trp and cortisol determination. The NR sows were less reactive to human contact (P=0.02), had a shorter farrowing duration (P=0.02), and tended to have a shorter birth interval between piglets (P=0.09) than the R sows. Feed intake was greater for the NR sows than for the R sows during wk 1 of lactation (P=0.02), as well as during the whole lactation (P=0.03). Plasma cortisol concentration was maximal on the day after farrowing (P=0.01) and returned to basal concentration within 4 d postpartum. No relationship was observed between sow behavior and plasma concentration of cortisol. For both groups of sows, plasma concentrations of Trp between d 2 and 4 postpartum were less than during gestation (P<0.05). The NR sows had decreased plasma Trp concentrations compared with the R sows during wk 1 of lactation (P=0.02). A low reactivity during gestation was associated with behavior of the sow that was favorable to piglet survival during farrowing, increased feed intake, and decreased plasma Trp concentration during wk 1 of lactation. Further research is needed to elucidate whether Trp or Trp metabolites are related to reactivity and ADFI of the reproducing sow.

Although dietary content of tryptophan has been related to variations of feed intake in lactating sows, the mechanisms remain to be elucidated. Twenty multiparous crossbred Landrace × Large White sows were used to assess variations of tryptophan metabolism around farrowing. Sows were fed 3 kg/d of a standard gestation diet from insemination until farrowing. They were then fed ad libitum a standard lactation diet until weaning. Sows were catheterised on day 70 of gestation and blood samples were drawn on day 37 before parturition, daily during the week before and the week after farrowing, and on days 14 and 21 of lactation. Plasma concentrations of amino acids, kynurenine, niacin, haptoglobin, urea, and vitamin B6 concentration in red blood cells were determined. During the week following parturition, plasma tryptophan and niacin decreased while plasma kynurenine increased (p < 0.05). On the 2nd and 3rd weeks of lactation, plasma tryptophan and kynurenine returned to pre-farrowing concentrations, while niacin increased throughout lactation (p < 0.05). Vitamin B6 increased progressively during the week after farrowing (p < 0.05) and remained constant at a high concentration thereafter. The average feed intake of the sow during lactation was positively correlated with the mean concentrations of niacin (r(2) = 0.25; p < 0.001) and kynurenine (r(2) = 0.31; p < 0.001) in plasma and with vitamin B6 in red blood cells (r(2) = 0.68; p < 0.001). This study suggests that tryptophan catabolism presumably through the kynurenine pathway is high during the 1st week after farrowing, and that dietary supply of niacin and vitamin B6 could be transiently suboptimal in early lactation.