Milk protein responses in dairy cows to changes in postruminal supplies of arginine, isoleucine, and valine

Abstract

An ideal profile of essential AA (EAA) can improve the efficiency of metabolizable protein (or PDIE, the equivalent in the INRA feeding system) utilization in dairy cows. Compared with other EAA, existing recommendations for the requirements of Arg, Ile, and Val are few and inconsistent. Four multiparous Holstein dairy cows at 22±6 wk of lactation received 4 treatments (duodenal infusions of 445±22.4 g/d of an EAA mixture complementing a low-protein diet in a 4×4 Latin square design with a period length of 1 wk). The control treatment provided a balanced supply (in % of PDIE) of 5.1% Arg, 5.2% Ile, and 5.9% Val, whereas in the 3 subsequent treatments of -Arg, -Ile, and -Val, the concentrations of these 3 EAA were reduced to 3.5, 4.1, and 4.5%, respectively. All treatments were made isonitrogenous and were balanced to provide 7 other EAA (Lys, Met, His, Leu, Phe, Thr, and Trp), according to the recommendations described in the literature. Combined, the diet and the infusions provided 14.3±0.1% crude protein on a dry matter basis, and 66.0±1.2 g of PDIE/Mcal of net energy for lactation. Neither dry matter intake (19.2 kg/d) nor milk yield (30.4±0.4 kg/d) was affected by treatments. The -Arg and -Ile treatments did not modify milk protein synthesis or the efficiency of N utilization. However, the -Val treatment decreased milk protein content by 4.9% and milk crude protein content by 4.3%, and tended to decrease the efficiency of N use for milk protein yield by 3.7% (compared with the control). These effects of Val were related to a decrease in the plasma concentration of Val as well as a trend toward decreasing plasma concentrations of Met, His, and the sum of all EAA and nonessential AA in the -Val treatment, which indicates a different utilization of all AA in response to the Val deficit. The deletion of Ile, compared with the deletion of Val, tended to decrease the milk protein-to-fat ratio by 3.8%. In conclusion, the supply of Arg at 3.5% of PDIE was not limiting for milk protein synthesis. The slight effect on the milk protein-to-fat ratio caused by decreasing the supply of Ile suggests a need to reevaluate the Ile requirement more precisely. A low Val supply could be limiting for milk protein synthesis, provided that the requirements of Lys, Met, and His are met.

Rumen microbial protein flow and plasma amino acid concentrations in early lactation multiparity Holstein cows fed commercial rations, and some relationships with dietary nutrients

“…Correlations amongst many plasma AA concentrations (Figure 7) resembles the network of interactions which have been documented among nutritionally important minerals (e.g., Jurgens molecules that should be considered in total, rather than individually, while also considering antagonisms and interactions amongst them (Haque et al, 2013). Such factors may explain the inconsistency of data obtained from studies that have supplemented ruminally protected AA and/or attempt to change the AA profile of intestinally delivered protein (Robinson, 2010).…”

“…Methods used to predict limiting AA, and therefore AA requirements, of lactating dairy cows are numerous, including culturing bovine mammary cells in AA mediums to determine effects on milk protein synthesis (Clark et al, 1978;Arriola Apelo et al, 2014b), evaluating changes in plasma AA concentrations and its impacts on milk and milk protein production during intravenous (Fisher, 1972) or post-ruminal supplementation of single or combinations of AA (Clark, 1975;Clark et al, 1978;Schwab et al, 1992a;1992b;Weekes et al, 2006;Haque et al, 2012;2013), doseresponse relationships between animal performance and N inputs (NRC 2001), calculating the extraction efficiency of the mammary gland by determining arteriovenous differences of AA across the mammary gland (Mulrooney et al, 2009;Christen et al, 2010), as well as uptake of AA from the small intestine (and the mammary gland) relative to their output in milk (Piepenbrink et al, 1998). However, results are variable and inconsistent, with some methods using metabolic models to predict AA supplied from experimental rations, and data is interpreted differently amongst researchers with overall levels highly dependent on base rations, which varied amongst experiments.…”

Response of lactating dairy cows to dietary protein from canola meal or distillers’ grains on dry matter intake, milk production, milk composition, and amino acid status

“…Arg was not likely limiting as Arg per se for synthesis of milk proteins, but rather it was needed by the mammary gland for other metabolic functions including the synthesis of Glu and Pro. Haque et al (2013) showed no protein synthesis response to duodenal infusions of Arg for cows fed a proteindeficient diet. Phe frequently ranks high as a limiting EAA for diets such as fed in this experiment because such diets are relatively low in both Phe and Tyr and the lactating bovine mammary gland can synthesize Tyr from Phe (Jorgensen and Larson 1968).…”

Effects of ruminally protected methionine and/or phenylalanine on performance of high producing Holstein cows fed rations with very high levels of canola meal

“…However this seems unlikely since the manufacturing technology of this RP-Phe was the same as the RP-Lys product evaluated in Sakkers et al (2013) which was measured in vivo to have a rumen escape of 52% of consumed Lys. Haque et al (2013) (Kaufman 1971), the first step in catabolizing Trp to synthesize serotonin and, since Trp levels in the plasma of both Phe supplemented treatments decreased vs.…”