Effects of rumen-encapsulated methionine and lysine supplementation and low dietary protein on nitrogen efficiency and lactation performance of dairy cows.

Low crude protein (CP) diets might be fed to dairy cows without affecting productivity if the balance of absorbed AA were improved, which would decrease the environmental effect of dairy farms. The aim of this study was to investigate the effects of supplementing ruminally protected Lys (RPL) and Met (RPM) at 2 levels of dietary CP on nutrient intake, milk production, milk composition, milk N efficiency (MNE), and plasma concentrations of AA in lactating Holstein cows and to evaluate these effects against the predictions of the new NASEM (2021) model. Fifteen multiparous cows were used in a replicated 3 × 3 Latin square design with 21-d periods. The 3 treatments were (1) a high-protein (HP) basal diet containing 16.4% CP (metabolizable protein [MP] balance of -130 g/d; 95% of target values), (2) a medium-protein diet containing 15% CP plus RPL (60 g/cow per day) and RPM (25 g/cow per day; MPLM; MP balance of -314 g/d; 87% of target values), and (3) a low-protein diet containing 13.6% CP plus RPL (60 g/cow per day) and RPM (25 g/cow per day; LPLM; MP balance of -479 g/d; 80% of target values). Dry matter intake was less for cows fed MPLM and LPLM diets compared with those fed the HP diet. Compared with the HP diet, the intake of CP, neutral detergent fiber, acid detergent fiber, and organic matter, but not starch, was lower for cows fed MPLM and LPLM diets. Milk production and composition were not affected by MPLM or LPLM diets relative to the HP diet. Milk urea N concentrations were reduced for the MPLM and LPLM diets compared with the HP diet, indicating that providing a low-protein diet supplemented with rumen-protected AA led to greater N efficiency. There was no significant effect of treatment on plasma AA concentrations except for proline, which significantly increased for the MPLM treatment compared with the other 2 treatments. Overall, the results supported the concept that milk performance might be maintained when feeding lactating dairy cows with low CP diets if the absorbed AA balance is maintained through RPL and RPM feeding. Further investigations are needed to evaluate responses over a longer time period with consideration of all AA rather than on the more aggregated MP and the ratio between Lys and Met.

Regulatory role of phosphoproteins in the development of bovine small intestine during early life.

The small intestine is the primary site of nutrient digestion and absorption, which plays a key role in the survival of neonatal calves. A comprehensive assessment of the phosphoproteomic changes in the small intestine of neonatal calves is unavailable; therefore, we used phosphopeptide enrichment coupled with liquid chromatography-tandem mass spectrometry to investigate the changes in the phosphoproteome profile in the bovine small intestine during the first 36 h of life. Twelve neonatal male calves were assigned to one of the following groups: (1) calves not fed colostrum and slaughtered approximately 2 h postpartum (n = 3), (2) calves fed colostrum at 1 to 2 h and slaughtered 8 h postpartum (n = 3), (3) calves fed 2 colostrum meals (at 1-2 and 10-12 h) and slaughtered 24 h postpartum (n = 3), (4) calves fed 3 colostrum meals (at 1-2, 10-12, and 22-24 h) and slaughtered 36 h postpartum (n = 3). Mid-duodenal, jejunal, and ileal samples of the calves were collected after slaughter. We identified 1,678 phosphoproteins with approximately 3,080 phosphosites, which were mainly Ser (89.9%), Thr (9.8%), and Tyr (0.3%) residues; they belonged to the prodirected (52.9%), basic (20.4%), acidic (16.6%), and Tyr-directed (1.7%) motif categories. The regional differentially expressed phosphoproteins included zonula occludens 2, sorting nexin 12, and protein kinase C, which are mainly associated with developmental processes, intracellular transport, vesicle-mediated transport, and immune system process. They are enriched in the endocytosis, tight junction, insulin signaling, and focal adhesion pathways. The temporal differentially expressed phosphoproteins included occludin, epsin 1, and bridging integrator 1, which were mainly associated with macromolecule metabolic process, cell adhesion, and growth. They were enriched in the spliceosomes, adherens junctions, and tight junctions. The observed changes in the phosphoproteins in the tissues of small intestine suggest the protein phosphorylation plays an important role in nutrient transport and immune response of calves during early life, which needs to be confirmed in a larger study.

Supplementation with Yucca schidigera improves antioxidant capability and immune function and decreases fecal score of dairy calves before weaning.

Yucca schidigera (YS) is a species of plant rich in antimicrobials, antioxidants, and immunomodulators. It has been used as feed additive to improve animal performance and decrease methane emissions in cattle. However, few studies have evaluated YS in dairy calves. In this study, we evaluated the effects of YS on the growth performance, antioxidant capacity, and immune function in dairy calves before weaning. We randomly assigned 40 newborn female Holstein calves (4 d old; 40 ± 5 kg of body weight) to 1 of 4 treatments (n = 10 per treatment), which were fed 0, 3, 6, or 9 g/d of YS powder. The YS allowance was mixed into milk or milk replacer and fed twice daily. Dry matter intake (both liquid and starter feed) and fecal score were recorded daily, and body weight, withers height, body length, and heart girth were measured at 4, 14, 28, 42, and 60 d of age. Blood was sampled from the jugular vein at 14, 42, and 60 d of age after the afternoon feeding for analysis of serum antioxidant capacity and immune function. Feeding YS did not affect dry matter intake, but decreased the feed-to-gain ratio with a quadratic dose effect. Over the whole study period, the average daily gain tended to linearly increase with the increasing YS doses, and it was 6.8% higher in diets supplemented with 9 g/d of YS than in the basal control diet without YS. The YS supplementation linearly decreased fecal score in a dose-dependent manner, and the frequency of diarrhea was significantly decreased as the YS supplementation increased throughout the whole study period. The YS supplementation also linearly decreased maleic dialdehyde concentration in the serum compared with the control group. The activity of catalase tended to linearly and quadratically increase, and that of glutathione peroxidase increased linearly with the increased YS supplementation. Serum concentrations of IgA and IgG increased linearly with the increased YS supplementation, and that of IgG tended to increase quadratically. To the best of our knowledge, this is the first study that demonstrated that feeding YS to young calves could improve growth, feed efficiency, and immunity, and decrease fecal score and diarrhea. The results of this study indicated that feeding YS at 9 g/d may be recommended to benefit dairy calves before weaning.

Rubber seed oil and flaxseed oil supplementation alter digestion, ruminal fermentation and rumen fatty acid profile of dairy cows.

Rubber seed oil (RO) that is rich in polyunsaturated fatty acids (FA) can improve milk production and milk FA profiles of dairy cows; however, the responses of digestion and ruminal fermentation to RO supplementation in vivo are still unknown. This experiment was conducted to investigate the effect of RO and flaxseed oil (FO) supplementation on nutrients digestibility, rumen fermentation parameters and rumen FA profile of dairy cows. Forty-eight mid-lactation Holstein dairy cows were randomly assigned to one of four treatments for 8 weeks, including basal diet (CON) or the basal dietary supplemented with 4% RO, 4% FO or 2% RO plus 2% FO on a DM basis. Compared with CON, dietary oil supplementation improved the total tract apparent digestibility of DM, neutral detergent fibre and ether extracts ( P < 0.05). Oil treatment groups had no effects on ruminal digesta pH value, ammonia N and microbial crude protein ( P > 0.05), whereas oil groups significantly changed the volatile fatty acid (VFA) profile by increasing the proportion of propionate whilst decreasing total VFA concentration, the proportion of acetate and the ratio of acetate to propionate ( P < 0.05). However, there were no differences in VFA proportions between the three oil groups (P > 0.05). In addition, dietary oil supplementation increased the total unsaturated FA proportion in the rumen by enhancing the proportion of trans-11 C18:1 vaccenic acid (VA), cis-9, trans-11 conjugated linoleic acid (CLA) and α-linolenic acid (ALA) ( P < 0.05). These results indicate that dietary supplementation with RO and FO could improve nutrients digestibility, ruminal fermentation and ruminal FA profile by enhancing the VA, cis-9, trans-11 CLA and ALA composition of lactating dairy cows. These findings provide a theoretical basis for the application of RO in livestock production.

Effects of close-up dietary energy level and supplementing rumen-protected lysine on energy metabolites and milk production in transition cows.

The objective of this study was to investigate the effects of dietary energy levels and rumen-protected lysine supplementation on serum free fatty acid levels, ß-hydroxybutyrate levels, dry matter (DM) intake, and milk production and composition. Treatments were arranged in a 2 × 2 factorial design with 2 dietary energy levels [high net energy for lactation (NEL) = 1.53 Mcal/kg of DM vs. low NEL = 1.37 Mcal/kg of DM; HE vs. LE) fed either with rumen-protected lysine (bypass lysine; 40 g/cow per day) or without rumen-protected lysine (control). Sixty-eight third-lactation Holstein dairy cows entering their fourth lactation were randomly allocated to 4 treatments groups: HE with bypass lysine, HE without bypass lysine, LE with bypass lysine, and LE without bypass lysine. Groups were balanced based upon their expected calving date, previous milk yields, and body condition score. All cows were fed the same diet (NEL = 1.34 Mcal/kg of DM) during the dry period prior to the trial. Rumen-protected lysine was top-dressed on a total mixed ration to deliver 9.68 g/d of metabolizable lysine to pre- and postpartum cows. After calving, all cows received the same TMR (1.69 Mcal/kg of DM). Blood samples were collected at -21, -14, -7, 0, 3, 7, 14, and 21 d relative to calving, and free fatty acids and ß-hydroxybutyrate concentrations were measured. Amount of feed offered and orts were collected and measured for individual cows 4 d/wk. Milk samples were collected once per week following calving, and milk composition was analyzed. Feeding high NEL to close-up cows decreased the concentrations of free fatty acid and ß-hydroxybutyrate in prepartum cows but not in postpartum cows. Addition of rumen-protected lysine increased postpartum DM intake, and decreased serum free fatty acid and ß-hydroxybutyrate concentrations. Neither energy nor rumen-protected lysine supplementation nor their interaction affected milk yield or fat or lactose yields. However, cows in the group receiving HE with bypass lysine tended to produce more milk compared with other groups and had a lower blood ß-hydroxybutyrate concentration postpartum. These results indicate that feeding a high-energy diet together with rumen-protected lysine improved DM intake and lowered serum free fatty acid and ß-hydroxybutyrate concentrations in transition cows.

Effects of source on bioavailability of selenium, antioxidant status, and performance in lactating dairy cows during oxidative stress-inducing conditions.

In the current study, we used heat stress (HS) as an oxidative stress model to examine the effects of hydroxy-selenomethionine (HMSeBA), an organic selenium source, on selenium's bioavailability, antioxidant status, and performance when fed to dairy cows. Eight mid-lactation Holstein dairy cows (141 ± 27 d in milk, 35.3 ± 2.8 kg of milk/d, parity 2 or 3) were individually housed in environmental chambers and randomly assigned to 1 of 2 treatments: inorganic Se supplementation (sodium selenite; SS; 0.3 mg of Se/kg of dry matter; n = 4) or HMSeBA supplementation (0.3 mg of Se/kg of dry matter; n = 4). The trial was divided into 3 continuous periods: a covariate period (9 d), a thermal neutral (TN) period (28 d), and a HS period (9 d). During the covariate and TN periods, all cows were housed in TN conditions (20°C, 55% humidity). During HS, all cows were exposed to cyclical HS conditions (32-36°C, 40% humidity). All cows were fed SS during the covariate period, and dietary treatments were implemented during the TN and HS periods. During HS, cows fed HMSeBA had increased Se concentrations in serum and milk, and total Se milk-to-serum concentration ratio compared with SS controls. Superoxide dismutase activity did not differ between Se sources, but we noted a treatment by day interaction in glutathione peroxidase activity as HS progressively reduced it in SS controls, whereas it was maintained in HMSeBA cows. Supplementation with HMSeBA increased total antioxidant capacity and decreased malondialdehyde, hydrogen peroxide, and nitric oxide serum concentrations compared with SS-fed controls. We found no treatment effects on rectal temperature, respiratory rate, or dry matter intake. Supplementing HMSeBA tended to increase milk yield and decrease milk fat percentage. No other milk composition parameters differed between treatments. We observed no treatment effects detected on blood biochemistry, except for a lower alanine aminotransferase activity in HMSeBA-fed cows. These results demonstrate that HMSeBA supplementation decreases some parameters of HS-induced oxidative stress.

Hydroxy-selenomethionine: A novel organic selenium source that improves antioxidant status and selenium concentrations in milk and plasma of mid-lactation dairy cows.

This study aimed to evaluate the effect of hydroxy-selenomethionine (HMSeBA), a novel organic selenium (Se) source, on milk performance, antioxidative status, and Se concentrations in the milk and plasma of mid-lactation dairy cows compared with that of sodium selenite (SS). Fifty mid-lactation dairy cows with similar days in milk, milk yield, and parity received the same basal diet containing 0.06 mg of Se/kg of DM. They were assigned to 1 of 5 treatments according to a randomized complete block design: negative control (without Se supplementation), SS supplementation (0.3 mg of Se/kg of DM; SS-0.3) or HMSeBA supplementation (0.1, 0.3, or 0.5 mg of Se/kg of DM: SO-0.1, SO-0.3, and SO-0.5, respectively). The experiment lasted for 10 wk, including a pretrial period of 2 wk. The results indicated that neither Se supplementation nor Se source affected dry matter intake, milk yield, milk composition, or blood biochemical parameters, except for milk fat percentage. Simultaneously, milk fat percentage and milk fat yield increased linearly as the quantity of HMSeBA supplementation was increased. Production of 4% FCM and ECM was elevated linearly as dietary HMSeBA increased. The SO-0.3 group showed higher serum activity of glutathione peroxidase, total antioxidant capacity, and superoxide dismutase than the SS-0.3 group, but malondialdehyde content was not affected by Se source. Furthermore, HMSeBA supplementation linearly increased the activities of serum glutathione peroxidase and superoxide dismutase, but decreased malondialdehyde content. Compared with the SS-0.3 group, the SO-0.3 group showed augmented concentrations of total Se in milk and plasma, and total Se milk-to-plasma concentration ratio. In addition, increasing doses of HMSeBA linearly increased the concentrations of total Se in the milk and plasma. This study demonstrates that HMSeBA improves antioxidant status and increases milk and plasma Se concentrations more effectively than SS, indicating that HMSeBA could replace SS as an effective organic Se source for lactating dairy cows.

Effectiveness of rubber seed oil and flaxseed oil to enhance the α-linolenic acid content in milk from dairy cows.

This experiment was conducted to investigate effect of rubber seed oil compared with flaxseed oil when fed alone or in combination on milk yield, milk composition, and α-linolenic acid (ALA) concentration in milk of dairy cows. Forty-eight mid-lactation Holstein dairy cows were randomly assigned to 1 of 4 treatments according to a completely randomized design. Cows were fed a basal diet (control; CON) or a basal diet supplemented with 4% rubber seed oil (RO), 4% flaxseed oil (FO), or 2% rubber seed oil plus 2% flaxseed oil (RFO) on a dry matter basis for 9 wk. Feed intake, milk protein percentage, and milk fat levels did not differ between the treatments. Cows fed the RO, FO, or RFO treatments had a higher milk yield than the CON group (up to 10.5% more), whereas milk fat percentages decreased. Compared with the CON, milk concentration of ALA was substantially higher in cows receiving RO or RFO, and was doubled in cows receiving FO. The ALA yield (g/d) increased by 31.0, 70.3, and 33.4% in milk from cows fed RO, FO, or RFO, respectively, compared with the CON. Both C18:1 trans-11 (vaccenic acid) and C18:2 cis-9,trans-11 (conjugated linoleic acid; CLA) levels were higher in cows fed added flaxseed or rubber seed oil. The CLA yield (g/d) increased by 336, 492, and 484% in cows fed RO, FO, or RFO, respectively, compared with the CON. The increase in vaccenic acid, ALA, and CLA was greater in cows fed RFO than in cows fed RO alone. Compared with the CON, the milk fat from cows fed any of the dietary supplements had a higher concentration of unsaturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids; conversely, the saturated fatty acids levels in milk fat were 30.5% lower. Insulin and growth hormones were not affected by dietary treatments; however, we noted an increase in both cholesterol and nonesterified fatty acids levels in the RO, FO, or RFO treatments. These results indicate that rubber seed oil and flaxseed oil will increase milk production and the concentration of functional fatty acids (ALA, vaccenic acid, and CLA) in milk fat while decreasing the content of saturated fatty acids.

Effects of rumen-protected γ-aminobutyric acid on performance and nutrient digestibility in heat-stressed dairy cows.

This experiment was conducted to investigate the effects of rumen-protected γ-aminobutyric acid (GABA) on performance and nutrient digestibility in heat-stressed dairy cows. Sixty Holstein dairy cows (141±15 d in milk, 35.9±4.3kg of milk/d, and parity 2.0±1.1) were randomly assigned to 1 of 4 treatments according to a completely randomized block design. Treatments consisted of 0 (control), 40, 80, or 120mg of true GABA/kg of dry matter (DM). The trial lasted 10wk. The average temperature-humidity indices at 0700, 1400, and 2200h were 78.4, 80.2, and 78.7, respectively. Rectal temperatures decreased linearly at 0700, 1400, and 2200h with increasing GABA concentration. Supplementation of GABA had no effect on respiration rates at any time point. Dry matter intake, energy-corrected milk, 4% fat-corrected milk, and milk fat yield tended to increase linearly with increasing GABA concentration. Supplementation of GABA affected, in a quadratic manner, milk protein and lactose concentrations, and milk protein yield, and the peak values were reached at a dose of 40mg of GABA/kg. Milk urea nitrogen concentration responded quadratically. Total solids content increased linearly with increasing GABA concentration. Supplementation of GABA had no effect on milk yield, lactose production, total solids, milk fat concentration, somatic cell score, or feed efficiency. Apparent total-tract digestibilities of DM, organic matter, crude protein, neutral detergent fiber, and acid detergent fiber were similar among treatments. These results indicate that rumen-protected GABA supplementation to dairy cows can alleviate heat stress by reducing rectal temperature, increase DM intake and milk production, and improve milk composition. The appropriate supplemental GABA level for heat-stressed dairy cows is 40mg/kg of DM.

Supplementing different ratios of short- and medium-chain fatty acids to long-chain fatty acids in dairy cows: changes of milk fat production and milk fatty acids composition.

Milk fat synthesis might be promoted by the dietary addition of long-chain fatty acids (LCFA) or short- and medium-chain fatty acids (SMCFA). This study evaluated unprotected lipid supplementation with different ratios of SMCFA to LCFA, which had equivalent fatty acid (FA) proportions (by weight) to those in milk, on milk fat production and milk FA composition. Thirty-six Holstein cows (183±46 d in milk) were divided into 3 treatments according to a randomized block design. Cows in 3 treatments received supplements of 80 g/d of SMCFA mixture and 320 g/d of LCFA mixture (ratio of SMCFA to LCFA was 20:80); 400 g/d of butterfat (ratio of SMCFA to LCFA was 40:60); or 240 g/d of SMCFA mixture and 160 g/d of LCFA mixture (ratio of SMCFA to LCFA was 60:40). The FA compositions of the SMCFA mixture and the LCFA mixture were similar to the de novo synthesized FA (except C4:0) and preformed FA (except trans FA) found in the butterfat, respectively. Fatty acid supplements and butterfat were consumed by cows daily before the morning feeding during the 8-wk experimental period. Dry matter intake and milk yield were not different among the treatments. The milk fat percentage and total SMCFA concentration in milk fat tended to increase linearly and the proportion of milk total solids increased linearly with increasing ratios of SMCFA to LCFA in the supplements, whereas milk fat yield was not changed. We suggest that increasing ratios of SMCFA to LCFA in diets has the potential to improve milk fat synthesis.

Effect of incremental levels of fish oil supplementation on specific bacterial populations in bovine ruminal fluid.

The objective of this study was to determine the effects of incremental replacement of dietary linoleic acid by >20-carbon polyunsaturated fatty acids (PUFA) on changes in population of ruminal micro-organisms associated with fibre digestion and biohydrogenation using real-time PCR of bacterial 16S rRNA sequences. Four beef steers with ruminal cannulas were randomly assigned to control (CK, 65:35 forage to concentrate), CK with 3% sunflower oil plus 1% fish oil (S3F1), 2.5% sunflower oil plus 1.5% fish oil (S2.5F1.5) or 2% sunflower oil plus 2% fish oil (S2F2) in a 4 × 4 Latin square design with 21-day periods. Ruminal fluid was collected on day 15 of each period. Compared with CK, oil addition led to lower ruminal acetate and butyrate but greater propionate concentration. DNA copy number of Anaerovibrio lipolytica in ruminal fluid was greater with oil (average 5.38 vs. 3.62 × 10(5) DNA copy number), particularly with S2F2 relative to CK. Fibrobacter succinogenes and Butyrivibrio fibrisolvens DNA copy number decreased by 74% (1.06 vs. 4.01 × 10(5)) and 39% (5.16 vs. 8.42 × 10(7)) in response to S2F2 compared with CK. DNA copy numbers of Ruminococcus flavefaciens and Ruminococcus albus were not affected by incremental fish oil. Results suggest that greater availability of PUFA with >20 carbons (i.e. eicosapentaenoic acid and docosahexaenoic acid) promoted changes in bacterial populations that are relevant for fibre digestion and biohydrogenation.

Effect of saturated fatty acid supplementation on production and metabolism indices in heat-stressed mid-lactation dairy cows.

Experimental objectives were to determine the effects of supplemental saturated fatty acids on production, body temperature indices, and some aspects of metabolism in mid-lactation dairy cows experiencing heat stress. Forty-eight heat-stressed Holstein cows were allocated into 3 groups (n=16/group) according to a completely randomized block design. Three treatment diets consisted of supplemental saturated fatty acids (SFA) at 0 (SFA0), 1.5 (SFA1.5), or 3.0% (SFA3) of dry matter (DM) for 10 wk. Diets were isonitrogenous (crude protein=16.8%) and contained 1.42, 1.46, and 1.49 Mcal of net energy for lactation/kg of DM for the SFA0, SFA1.5 and SFA3 diets, respectively. The average temperature-humidity index at 0700, 1400 and 2200 h was 72.2, 84.3, and 76.6, respectively. Rectal temperatures at 1400 h were decreased with fat supplementation. Treatment did not affect dry matter intake (20.1+/-0.02 kg/d), body condition score (2.72+/-0.04), body weight (627+/-16.1 kg), or calculated energy balance (1.32+/-0.83 Mcal/d). Saturated fatty acid supplementation increased milk yield, milk fat content, and total milk solids. Increasing fat supplementation decreased plasma nonesterified fatty acids (8%) but had no effect on other energetic metabolites or hormones. In summary, supplemental SFA improved milk yield and milk fat content and yield and reduced peak rectal temperatures in mid-lactation heat-stressed dairy cows. This demonstrates the remarkable amount of metabolic heat that is "saved" by energetically replacing fermentable carbohydrates with supplemental SFA.

Effectiveness of oils rich in linoleic and linolenic acids to enhance conjugated linoleic acid in milk from dairy cows.

Forty Holstein dairy cows were used to determine the effectiveness of linoleic or linolenic-rich oils to enhance C18:2 cis-9, trans-11 conjugated linoleic acid (CLA) and C18:1 trans-11 (vaccenic acid; VA) in milk. The experimental design was a complete randomized design for 9 wk with measurements made during the last 6 wk. Cows were fed a basal diet containing 59% forage (control) or a basal diet supplemented with either 4% soybean oil (SO), 4% flaxseed oil (FO), or 2% soybean oil plus 2% flaxseed oil (SFO) on a dry matter basis. Total fatty acids in the diet were 3.27, 7.47, 7.61, and 7.50 g/100 g in control, SO, FO, and SFO diets, respectively. Feed intake, energy-corrected milk (ECM) yield, and ECM produced/kg of feed intake were similar among treatments. The proportions of VA were increased by 318, 105, and 206% in milk fat from cows in the SO, FO, and SFO groups compared with cows in the control group. Similar increases in C18:2 cis-9, trans-11 CLA were 273, 150, and 183% in SO, FO, and SFO treatments, respectively. Under similar feeding conditions, oils rich in linoleic acid (soybean oil) were more effective in enhancing VA and C18:2 cis-9, trans-11 CLA in milk fat than oils containing linolenic acid (flaxseed oil) in dairy cows fed high-forage diets (59% forage). The effects of mixing linoleic and linolenic acids (50:50) on enhancing VA and C18:2 cis-9, trans-11 CLA were additive, but not greater than when fed separately. Increasing the proportion of healthy fatty acids (VA and CLA) by feeding soybean or flaxseed oil would result in milk with higher nutritive and therapeutic value.