Amino Acid Utilization by Lactating Mammary Gland

Mepham, T. B.

doi:10.3168/jds.s0022-0302(82)82191-7

Cited by 219 publications

(162 citation statements)

References 52 publications

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“…Mepham (1982) divided AA into three groups based on the efficiency by which AA are taken up by the mammary gland and excreted in milk. This division was slightly modified by Raggio et al (2006; Table 3).…”

Section: Factors Affecting the Efficiency Of N Utilization In The Mammentioning

confidence: 99%

Strategies for optimizing nitrogen use by ruminants

Calsamiglia

Ferret

Reynolds

et al. 2010

Animal

249

165

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The efficiency of N utilization in ruminants is typically low (around 25%) and highly variable (10% to 40%) compared with the higher efficiency of other production animals. The low efficiency has implications for the production performance and environment. Many efforts have been devoted to improving the efficiency of N utilization in ruminants, and while major improvements in our understanding of N requirements and metabolism have been achieved, the overall efficiency remains low. In general, maximal efficiency of N utilization will only occur at the expense of some losses in production performance. However, optimal production and N utilization may be achieved through the understanding of the key mechanisms involved in the control of N metabolism. Key factors in the rumen include the efficiency of N capture in the rumen (grams of bacterial N per grams of rumen available N) and the modification of protein degradation. Traditionally, protein degradation has been modulated by modifying the feed (physical and chemical treatments). Modifying the rumen microflora involved in peptide degradation and amino acid deamination offers an alternative approach that needs to be addressed. Current evidence indicates that in typical feeding conditions there is limited net recycling of N into the rumen (blood urea-N uptake minus ammonia-N absorption), but understanding the factors controlling urea transport across the rumen wall may reverse the balance to take advantage of the recycling capabilities of ruminants. Finally, there is considerable metabolism of amino acids (AA) in the portal-drained viscera (PDV) and liver. However, most of this process occurs through the uptake of AA from the arterial blood and not during the 'absorptive' process. Therefore, AA are available to the peripheral circulation and to the mammary gland before being used by PDV and the liver. In these conditions, the mammary gland plays a key role in determining the efficiency of N utilization because the PDV and liver will use AA in excess of those required by the mammary gland. Protein synthesis in the mammary gland appears to be tightly regulated by local and systemic signals. The understanding of factors regulating AA supply and absorption in the mammary gland, and the synthesis of milk protein should allow the formulation of diets that increase total AA uptake by the mammary gland and thus reduce AA utilization by PDV and the liver. A better understanding of these key processes should allow the development of strategies to improve the efficiency of N utilization in ruminants. Keywords: ruminant, nitrogen efficiency ImplicationsRuminants have a low efficiency of N utilization compared with non-ruminants. This low efficiency has implications not only for production performance and economic efficiency but also for the emission of contaminants to the environment. The efficiency of N utilization can be improved through the understanding and modification of factors regulating the efficiency of N utilization in key processes, including N capture in the rumen, ...

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Section: Factors Affecting the Efficiency Of N Utilization In The Mammentioning

confidence: 99%

Strategies for optimizing nitrogen use by ruminants

Calsamiglia

Ferret

Reynolds

et al. 2010

Animal

249

165

View full text Add to dashboard Cite

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“…En (Mepham, 1982 (Rulquin, 1981(Rulquin, , 1982(Rulquin, , 1983 (Christensen, 1977). Pour la méthionine, la thréonine et la valine, acides aminés ayant plusieurs systèmes de transport, ces relations ( fig.…”

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Utilisation des produits terminaux de la digestion par la mamelle chez la vache laitière

Rulquin¹,

Fléchet²,

Lefaivre³

et al. 1986

Reprod. Nutr. Dévelop.

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Summary. Use of the end-products of digestion by the udder of the dairy cow.Relations between mammary arterio-venous (AV) differences and arterial level were studied for glucose, acetate and beta-hydroxybutyrate on 172 samples and for blood essential amino acids on 20 samples, pooled by day and by cow. The data were obtained from 32 experiments on 5 cows eating various diets (Rulquin, 1981(Rulquin, , 1983. AV differences in acetate and beta-hydroxybutyrate were highly related to the arterial levels (R = 0.97 and 0.86) and averaged 74 and 41 % of these levels ( fig. 11. On the other hand, the AV difference in glucose was poorly (R = 0.5) related to the arterial levels.Among the essential amino acids, only AV differences in phenylalanine, leucine, arginine, isoleucine and histidine were linearly related to the arterial levels (R = 0. 78, 0.73, 0.68, 0.63, 0.60) (fig. 2). AV differences in lysine, methionine, valine and threonine were more related to the AV differences of other amino acids than to the arterial levels ( fig. 3).These results have been discussed in connection with different mammary metabolic transport systems and with the ability to modify mammary nutrient input by dietary manipulation.Introduction.

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“…This regulation was demonstrated by the increased hepatic removal of histidine, methionine, phenylalanine representing 50 to 87% of their increased portal absorption during the mesenteric infusion of a mixture of amino acids in late gestation dry dairy cows [48]. For these amino acids, their postsplanchnic supply matches closely their milk output in lactating cows [30] and their ratio of milk output to mammary uptake is close to unity [36]. Consequently, by-passing the liver when infusing amino acids could enhance mammary gland metabolism and milk protein synthesis.…”

Section: Introductionmentioning

confidence: 99%

The effect of jugular or abomasal infusion of amino acids on milk yield in lactating cows fed a protein deficient diet

et al. 2002

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-The influence of first-pass splanchnic metabolism was investigated by comparing the response of 5 lactating cows to an infusion of an amino acid mixture into the abomasum or a jugular vein over 5 d according to a complete block design. The basal diet and the amino acid infusion provided 71% and 14% of crude protein requirements, respectively. The jugular infusion increased (P = 0.01) milk yield by 0.80 kg in comparison to the abomasal infusion, but milk protein yield was not altered. The jugular infusion tended to increase (P = 0.06) the arterial concentration of total essential amino acids by 11% relatively to the abomasal infusion. Mammary plasma flow and net fluxes of amino acids and glucose were not affected by the infusion sites. Variations in essential amino acid concentrations suggest that splanchnic metabolism alters peripheral delivery of amino acids but the recirculation of amino acids within the animal decreased the impact of the first-pass splanchnic metabolism on lactational performances. amino acid / cow / infusion / milk yield / proteinRésumé -Effet d'une perfusion jugulaire ou abomasale d'acides aminés sur la production laitière de vaches en lactation alimentées avec une ration déficiente en protéine. L'influence du premier passage des acides aminés dans le tissu splanchnique a été étudiée en comparant la réponse de 5 vaches laitières à des perfusions abomasale ou jugulaire administrées durant 5 j selon un dispositif en blocs complets. La ration de base et la perfusion d'acides aminés fournissaient 71 % et 14 % des besoins en protéine brute, respectivement. La perfusion jugulaire a augmenté (P = 0,01) la Reprod. Nutr. Dev. 42 (2002)

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Amino Acid Utilization by Lactating Mammary Gland

Cited by 219 publications

References 52 publications

Strategies for optimizing nitrogen use by ruminants

Strategies for optimizing nitrogen use by ruminants

Utilisation des produits terminaux de la digestion par la mamelle chez la vache laitière

The effect of jugular or abomasal infusion of amino acids on milk yield in lactating cows fed a protein deficient diet

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