Abstract
BackgroundDetermination of nutrient requirements in the late gestating and lactating sows is essential to optimize sow productivity. The objectives of the present study were to quantify amino acid (AA) fluxes and heat production across portal-drained viscera (PDV) and liver in multiparous sows during transition and lactation.MethodsEight second parity sows were fitted with indwelling catheters in the femoral artery and in the mesenteric, portal and hepatic veins. Eight hourly sets of blood samples were taken starting 0.5 h before feeding at − 10, − 3, + 3, and + 17 d in milk (DIM). Blood gases, plasma metabolites and apparent total tract digestibility (ATTD) of nutrients were measured.ResultsFeed intake, the ATTD of DM, energy, nitrogen, fat and crude fiber changed with DIM (P < 0.001). Except for Glu, O2, and urea, all net portal fluxes were positive, and all were affected by DIM (P < 0.05) and by sampling time (P < 0.01). Compared with pre partum levels, net portal uptake of AA was 3-63% lower at + 3 DIM but 40-100% higher at + 17 DIM. Net portal fluxes of AA peaked at 1.5 to 2.5 h after feeding except for Glu, and they were positively correlated with changes in sow feed intake across DIM. The net portal recovery was low for Met (49%), Thr (54%), and His (54%) and high for the remaining essential AA (63-69%) and none of them differed across DIM. Net hepatic uptake (i.e. hepatic oxidation) of Lys, Thr, Ile, Leu and Phe peaked at 0.5 to 2.5 h after feeding, whereas uptake of Trp, Val, and His was constant, while that of Met was close to zero.ConclusionThe net portal recovery was substantially lower for Met, Thr, and His than the remaining essential AA. Hepatic AA oxidation peaks 0.5 to 2.5 h after feeding. The heat production in PDV and liver was approximately two-fold higher at peak lactation compared to other stages. The study suggests that lysine was the limiting AA in peak lactation but not in early lactation.
Highlights
In recent years, extensive research has been conducted to improve the efficiency of protein utilization and mitigate nitrogen losses to the environment [1,2,3]
During the transition and lactation period, many physiological processes related to reproductive output are markedly changed [7], but knowledge on whether hepatic oxidation and net splanchnic release of amino acid (AA) change with the reproductive stage is lacking for the sow
Hepatic uptake of AA peaked around 1.5 h after feeding and concomitantly the hepatic release of urea tended to peak, indicating that except for Met, Val, and Glu, a substantial loss of both essential and non-essential AA occur during the first few hours after feeding. These findings suggest that the liver is able to judge whether excessive amounts of AA are present in the circulating blood, possibly by evaluating critical concentrations of each specific AA in portal blood and based on that decide whether the AA should be oxidized
Summary
Extensive research has been conducted to improve the efficiency of protein utilization and mitigate nitrogen losses to the environment [1,2,3] These works have led to the development of diets with near optimal protein content and amino acid (AA) ratios in order to maximize reproductive performances of sows [4, 5]. It is challenging to estimate AA efficiencies from the diet because sows concomitantly mobilize AA from the body It is not known whether the net portal uptake of AA changes across different physiological stages in response to substantial changes in feed intake, which would in turn affect the passage rate and net absorption profile [6]. The objectives of the present study were to quantify amino acid (AA) fluxes and heat production across portal-drained viscera (PDV) and liver in multiparous sows during transition and lactation
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