Jugular-infused methionine, lysine and branched-chain amino acids does not improve milk production in Holstein cows experiencing heat stress

Abstract

Poor utilization of amino acids contributes to losses of milk protein yield in dairy cows exposed to heat stress (HS). Our objective was to test the effect of essential amino acids on milk production in lactating dairy cows exposed to short-term HS conditions. To achieve this objective, 12 multiparous, lactating Holstein cows were assigned to two environments (thermoneutral (THN) or HS) from days 1 to 14 in a split-plot type cross-over design. All cows received 0 g/day of essential amino acids from days 1 to 7 (negative control (NC)) followed by an intravenous infusion of l-methionine (12 g/day), l-lysine (21 g/day), l-leucine (35 g/day), l-isoleucine (15 g/day) and l-valine (15 g/day, methionine, lysine and branched-chain amino acids (ML+BCAA)) from days 8 to 14. The basal diet was composed of ryegrass silage and hay, and a concentrate mix. This diet supplied 44 g of methionine, 125 g of lysine, 167 g of leucine, 98 g of isoleucine and 109 g of valine per day to the small intestine of THN cows. Temperature-humidity index was maintained below 66 for the THN environment, whereas the index was maintained above 68, peaking at 76, for 14 continuous h/day for the HS environment. Heat stress conditioning increased the udder temperature from 37.0°C to 39.6°C. Cows that received the ML+BCAA treatment had greater p.m. rectal and vaginal temperatures (0.50°C and 0.40°C, respectively), and respiration rate (8 breaths/min) compared with those on the NC treatment and exposed to a HS environment. However, neither NC nor ML+BCAA affected rectal or vaginal temperatures and respiration rates in the THN environment. Compared with THN, the HS environment reduced dry matter intake (1.48 kg/day), milk yield (2.82 kg/day) and milk protein yield (0.11 kg/day). However, compared with NC, the ML+BCAA treatment increased milk protein percent by 0.07 points. For the THN environment, the ML+BCAA treatment increased concentrations of milk urea nitrogen. For the HS environment, the ML+BCAA treatment decreased plasma concentrations of arginine, ornithine and citrulline; however, differences were not observed for the THN environment. In summary, HS elicited expected changes in production; however, infusions of ML+BCAA failed to increase milk protein yield. Lower dry matter intake and greater heat load in response to ML+BCAA contributed to the lack of response in milk production in HS cows. The ML+BCAA treatment may have reduced the breakdown of muscle protein in heat-stressed cows.

Lowering rumen-degradable protein maintained energy-corrected milk yield and improved nitrogen-use efficiency in multiparous lactating dairy cows exposed to heat stress

“…Under the conditions of this study, the 8D:6U treatment provided a balanced supply of AA in MP, which sustained high yields of ECM. Additionally, the balanced supply of AA reduces AA oxidation and plasma urea concentrations (Bach et al, 2000;Kassube et al, 2017). The latter contention is supported by lower MUN values observed from cows in the present study.…”

“…Even with new technologies and advances in heat abatement techniques, warm climates continue to present problems for lactating dairy cows (Ravagnolo et al, 2000). Reduction of RDP and RUP can potentially reduce some of the negative effects of heat stress on dairy cows (Kassube et al, 2017). Herein, the effects of RDP and RUP proportions are evaluated on intake, milk production, and N-use efficiency for primiparous and multiparous dairy cows exposed to heat stress.…”

Effect of rumen-protected branched-chain amino acid supplementation on production- and energy-related metabolites during the first 35 days in milk in Holstein dairy cows

“…Sadri et al (2017) reported an increase in plasma concentration of Leu after a single duodenal bolus infusion of Leu at a dose of 0.15 g/kg of BW. On the other hand, Kassube et al (2017) did not find an increase in concentrations of free plasma BCAA after intravenous infusion of Met (12 g/d), Lys (21 g/d), and BCAA (35 g/d of Leu, 15 g/d of Ile, and 15 g/d of Val). Changes in the concentration of plasma free BCAA could be due to reduced DMI, BCAA absorption in the intestine or enhanced tissue uptake for catabolism or protein synthesis.…”

“…A subset of samples was selected to measure the concentration of plasma AA based on critical time points during the study (e.g., enrollment, time of biopsies, and beginning, middle, and end of the treatments). Plasma free AA concentrations were determined using EZ: faast (Phenomenex, Torrance, CA) by the chromatography and diagnostic services laboratory of the Veterinary Faculty, University of Montréal, as previously described (Kassube et al, 2017). Briefly, solid-phase extraction was followed by derivatization and a liquid/liquid extraction.…”

Lowering rumen-degradable and rumen-undegradable protein improved amino acid metabolism and energy utilization in lactating dairy cows exposed to heat stress

“…Concentrations of plasma free AA (EDTA samples on d −1 and 21 of the study) were measured using liquid chromatography coupled with mass spectrometry and a commercially available kit (Phenomenex EZ: faast, Torrance, CA) as previously described (Meesters et al, 2009;Ubhi et al, 2013;Kassube et al, 2017). Briefly, AA were removed from plasma using solid-phase extraction, derivatization, and liquid-phase extraction.…”