Krogh U, Oksbjerg N, Storm A C, Feyera T, Theil P K
J Anim Sci. 2017 Jun;95(6):2517-2532. doi: 10.2527/jas.2016.1291.
Arginine is the precursor for the synthesis of nitric oxide and may increase mammary plasma flow (MPF), which may in turn increase mammary nutrient uptake. Quantifying mammary nutrient uptake improves our understanding of mammary nutrient metabolism and may potentially allow identification of limiting nutrients for colostrum and milk production. Thus, the objectives of the present study were 1) to study the impact of 25 g/d of crystalline Arg (ARG) on MPF and uptake of nutrients by the mammary glands compared with an isonitrogenous supply of Ala (51 g/d; control [CON]) fed to a total of 8 sows from d 30 of gestation until weaning on d 28 of lactation and 2) to quantify mammary nutrient uptake in late gestation and in early and at peak lactation. Sows were surgically fitted with indwelling catheters on d 76 ± 2 SEM of gestation. -amino hippuric acid (AH) was infused (3.0 mmol/h) in the infusion catheter inserted in the mammary vein, initiated 1 h before the first blood sample at -10, -3, 3, and 17 d in milk (DIM). Blood samples were simultaneously drawn from catheters inserted in the femoral artery and the mammary vein, and the samples were collected in hourly intervals from 0.5 h before to 6.5 h after feeding. Sow milk production was assessed at 3 and 17 DIM. Arterial plasma concentrations of Arg and Ala were increased in ARG and CON sows, respectively ( < 0.01), whereas we did not succeed in detecting a greater MPF in ARG sows ( = 0.30). Arterial-venous differences ( = 0.03) and net mammary flux ( = 0.01) of Ala were increased in CON sows, while the net flux of most other metabolites ( > 0.05) was unaffected by treatment. The mammary extraction of all essential AA was below 13% in late gestation. The average mammary extraction of essential AA at peak lactation was greatest for Leu (51%), while the preprandial extraction was greatest for Lys (57%). The mammary carbon balance (input-output) was negative (-39 ± 12 mol C/d) in early lactation but almost balanced at peak lactation (-13 ± 14 mol C/d), suggesting that mammary fat depots contributed to milk synthesis. In conclusion, we failed to observe an increased MPF and mammary uptake of AA and energy metabolites in ARG-supplemented sows. The mammary extraction rate of essential AA indicated that AA were not limiting for the mammary glands in late gestation, while Lys and Leu appeared to be the 2 most limiting essential AA for milk production at peak lactation.
精氨酸是一氧化氮合成的前体，可能会增加乳腺血浆流量（MPF），进而可能增加乳腺对营养物质的摄取。量化乳腺对营养物质的摄取有助于我们更好地理解乳腺营养代谢，并有可能识别初乳和乳汁生产中的限制性营养素。因此，本研究的目的是：1）研究与向8头母猪从妊娠第30天至泌乳第28天断奶饲喂等氮量丙氨酸（51 g/d；对照组[CON]）相比，每天25 g结晶精氨酸（ARG）对MPF和乳腺对营养物质摄取的影响；2）量化妊娠后期、泌乳早期和泌乳高峰期乳腺对营养物质的摄取。在妊娠第76±2 SEM天对母猪进行手术植入留置导管。在泌乳第-10、-3、3和17天（DIM）首次采集血样前1小时，将对氨基马尿酸（AH）以3.0 mmol/h的速度注入插入乳腺静脉的输液导管中。同时从插入股动脉和乳腺静脉的导管中采集血样，从喂食前0.5小时至喂食后6.5小时每隔1小时采集一次样本。在泌乳第3天和第17天评估母猪的乳汁产量。ARG组和CON组母猪的动脉血浆精氨酸和丙氨酸浓度分别升高（<0.01），而我们未能检测到ARG组母猪的MPF更高（=0.30）。CON组母猪的丙氨酸动静脉差异（=0.03）和乳腺净通量（=0.01）增加，而大多数其他代谢物的净通量（>0.05）不受处理影响。妊娠后期所有必需氨基酸的乳腺摄取率均低于13%。泌乳高峰期亮氨酸的必需氨基酸平均乳腺摄取率最高（51%），而餐前赖氨酸的摄取率最高（57%）。泌乳早期乳腺碳平衡（输入-输出）为负（-39±12 μmol C/d），但在泌乳高峰期几乎平衡（-13±14 μmol C/d），这表明乳腺脂肪库有助于乳汁合成。总之，我们未能观察到补充ARG的母猪MPF增加以及乳腺对氨基酸和能量代谢物的摄取增加。必需氨基酸的乳腺摄取率表明，妊娠后期氨基酸对乳腺不是限制性的，而赖氨酸和亮氨酸似乎是泌乳高峰期乳汁生产中最具限制性的两种必需氨基酸。
