Impacts of adding ruminally protected phenylalanine to rations containing high levels of canola meal on performance of high producing Holstein cows

Abstract

Highlights• Supplementation of Phe to early lactation cows receiving 170 g/kg of diet DM as CM.• Phe changed energy utilization, decreasing milk lactose while increasing BCS gain.• Phe resulted in an increase in whole tract aNDFom and ADF digestibility.• Phe support milk production after restoring mobilized peptides to muscle protein.• Phe regained animal performance lost when CM inclusion was increased. AbstractEven though studies supplementing Phe to dairy cattle are rare, it has been identified as limiting in corn silage based rations, after Lys and Met, as well as being important to the mammary gland for overall milk production. Since canola meal (CM) is low in Phe, plasma Phe concentrations decrease as more CM is included in dairy rations. A previous study fed 7.5 g/cow/day of intestinally absorbable Phe, but results suggested that it was insufficient to support increased milk production since it was primarily used to support increased body condition score (BCS;Swanepoel et al., 2015). Our objective was to determine if supplementing 15 g/cow/day of intestinally absorbable Phe in a ruminally protected (RP) form (HCMP) to a ration containing 170 g/kg CM (HCM) would support increased milk production after fulfilling its apparent 1 st priority of restoring previously mobilized peptides to muscle protein synthesis, thereby regaining animal performance possibly lost with higher dietary CM inclusion levels (i.e., 130 g/kg (LCM) to 165 g/kg (HCM)) based upon Swanepoel et al. (2015). Ruminally protected Met (2.0 g/cow/day intestinally absorbable) was added as part of the treatment ration to HCM treatments to avoid a possible Met limitation. The experimental design was a 3 x 3 Latin square using 3 pens of ~315 early lactation cows/pen with three 21 day periods. Dry matter (DM) intake was not affected (avg: 27.5 ± 0.5 kg/day) by feeding RP Phe and there was no impact of treatment on milk and component yields, except a reduced lactose content (P=0.02) with Phe addition. Even though plasma Phe levels only differed numerically between treatments, its supplementation resulted in energy being diverted towards BCS gain as in Swanepoel et al. (2015), but not at the expense of milk components, suggesting that higher Phe supplementation supplied enough Phe to replace mobilized muscle protein while maintaining milk production. The lack in change of plasma Phe concentrations could be due to extensive catabolization by the liver or hepatic conversion of Phe to Tyr, which is supported by the change in plasma Tyr concentrations.Interestingly, addition of Phe to the HCM ration increased whole tract neutral-and acid detergent fiber digestibility. Perhaps Phe released into the rumen when Phe was fed stimulated fibrolytic bacteria through a direct impact on microbes of free Phe, which has previously been shown to enhance growth and/or capabilities of cellulolytic bacteria. Total net energy output decreased with HCM feeding, but was restored to the level of the LCM ration for the HCMP treatment suggesting that further investigation to d...

Production responses of high producing Holstein cows to ruminally protected phenylalanine and tyrosine supplemented to diets containing high levels of canola meal

“…The chemical composition of the ingredients used in the TMR (Table 1) were generally consistent with NRC (2001) values. However, alfalfa hay, Pima cottonseed, wheat and corn silage all had slightly higher CP levels than in previous studies (Swanepoel et al, 2014(Swanepoel et al, , 2015(Swanepoel et al, , 2016a.…”

“…At a supplementation level of ~15 g/d of intestinally available Phe (Swanepoel et al, 2015), this NE repartitioning was not at the expense of milk protein and fat synthesis, as was the case with a lower Phe supplementation level of ~7.5 g/d in Swanepoel et al (2016a). The resultant hypothesis;…”

“…The low CM (LCM) and high CM (HCM) diets were formulated using NRC (2001) tabular guidelines to be similar relative to ingredient profiles, including canola meal, to the diet used in Swanepoel et al (2016a) with the LCM treatment containing CM at ~120 g CM/kg DM and the HCM treatment with CM included at ~170 g CM/kg DM ( Table 2). The increase in CM with the HCM (versus LCM) diet was compensated by reductions in levels of cottonseed, corn gluten feed and DDGS such that similar proximate nutrient profiles were maintained between the LCM and HCM diets.…”

“…Since canola meal (CM) is relatively low in Phe compared to other protein meals, we previously completed two studies to determine if Phe supplementation, at two levels, to early lactation dairy cow diets containing high levels of CM would be beneficial to performance (Swanepoel et al, 2015(Swanepoel et al, , 2016a. In both studies, supplementation of Phe resulted in a change of energy partitioning with redirection of net energy (NE) towards body condition score (BCS) gain.…”

Phenylalanine and valine differentially stimulate milk protein synthetic and energy-mediated pathway in immortalized bovine mammary epithelial cells

“…Thus, further analyses were performed to investigate the effects of PHE or VAL on protein synthesis-related responses and energy-mediated cellular signaling in MAC-T cells. When high milk-producing Holstein cows fed a rumen protected form of PHE, little or no change in body conditions score were observed and there is either a tendency towards a decrease or no change in true milk protein yield compared to control group [14][15][16]. However, our study showed a significant increase in concentrations of protein in both the cultured medium and within cells after PHE treatment ( Fig.…”