Effect of Varying Levels of Fatty Acids from Palm Oil on Feed Intake and Milk Production in Holstein Cows

Effects of altering the ratio of C16:0 and cis-9 C18:1 in rumen bypass fat on growth performance, lipid metabolism, intestinal barrier, cecal microbiota, and inflammation in fattening bulls

BACKGROUND

C16:0 and cis-9 C18:1 may have different effects on animal growth and health due to unique metabolism in vivo. This study was investigated to explore the different effects of altering the ratio of C16:0 and cis-9 C18:1 in fat supplements on growth performance, lipid metabolism, intestinal barrier, cecal microbiota, and inflammation in fattening bulls. Thirty finishing Angus bulls (626 ± 69 kg, 21 ± 0.5 months) were divided into 3 treatments according to the randomized block design: (1) control diet without additional fat (CON), (2) CON + 2.5% palmitic acid calcium salt (PA, 90% C16:0), and (3) CON + 2.5% mixed fatty acid calcium salt (MA, 60% C16:0 + 30% cis-9 C18:1). The experiment lasted for 104 d, after which all the bulls were slaughtered and sampled for analysis.

RESULTS

MA tended to reduce 0-52 d dry matter intake compared to PA (DMI, P = 0.052). Compared with CON and MA, PA significantly increased 0-52 d average daily gain (ADG, P = 0.027). PA tended to improve the 0-52 d feed conversion rate compared with CON (FCR, P = 0.088). Both PA and MA had no significant effect on 52-104 days of DMI, ADG and FCR (P > 0.05). PA tended to improve plasma triglycerides compared with MA (P = 0.077), significantly increased plasma cholesterol (P = 0.002) and tended to improve subcutaneous adipose weight (P = 0.066) when compared with CON and MA. Both PA and MA increased visceral adipose weight compared with CON (P = 0.021). Only PA increased the colonization of Rikenellaceae, Ruminococcus and Proteobacteria in the cecum, and MA increased Akkermansia abundance (P < 0.05). Compared with CON, both PA and MA down-regulated the mRNA expression of Claudin-1 in the jejunum (P < 0.001), increased plasma diamine oxidase (DAO, P < 0.001) and lipopolysaccharide (LPS, P = 0.045). Compared with CON and MA, PA down-regulated the ZO-1 in the jejunum (P < 0.001) and increased plasma LPS-binding protein (LBP, P < 0.001). Compared with CON, only PA down-regulated the Occludin in the jejunum (P = 0.013). Compared with CON, PA and MA significantly up-regulated the expression of TLR-4 and NF-κB in the visceral adipose (P < 0.001) and increased plasma IL-6 (P < 0.001). Compared with CON, only PA up-regulated the TNF-α in the visceral adipose (P = 0.01). Compared with CON and MA, PA up-regulated IL-6 in the visceral adipose (P < 0.001), increased plasma TNF-α (P < 0.001), and reduced the IgG content in plasma (P = 0.035). Compared with CON, PA and MA increased C16:0 in subcutaneous fat and longissimus dorsi muscle (P < 0.05), while more C16:0 was also deposited by extension and desaturation into C18:0 and cis-9 C18:1. However, neither PA nor MA affected the content of cis-9 C18:1 in longissimus dorsi muscle compared with CON (P > 0.05).

CONCLUSIONS

MA containing 30% cis-9 C18:1 reduced the risk of high C16:0 dietary fat induced subcutaneous fat obesity, adipose tissue and systemic low-grade inflammation by accelerating fatty acid oxidative utilization, improving colonization of Akkermansia, reducing intestinal barrier damage, and down-regulating NF-κB activation.

Farm-level nutritional factors associated with milk production and milking behavior on Canadian farms with automated milking systems

The objective of this study was to describe the nutritional strategies used on Canadian dairy farms with automated milking systems (AMS), both at the feed bunk and the concentrate offered at the AMS, as well as to determine what dietary components and nutrients, as formulated, were associated with milk production and milking behaviors on those farms. Formulated diets (including ingredients and nutrient content) and AMS data were collected from April 1, 2019, until September 30, 2020, on 160 AMS farms (eastern Canada [East] = 8, Ontario [ON] = 76, Quebec [QC] = 22, and western Canada [West] = 54). Both partial mixed ration (PMR) and AMS concentrate samples were collected from May 1 to September 30, 2019, on 169 farms (East = 12, ON = 63, QC = 42, West = 52). We collected AMS milking data for 154 herds. For each farm (n = 161), milk recording data were collected and summarized by farm to calculate average milk yield and components. Multivariable regression models were used to associate herd-level formulated nutrient composition and feeding management practices with milk production and milking behavior. Milk yield (mean ± SD = 37.0 ± 0.3 kg/d) was positively associated with the PMR ether extract (EE) concentration (+0.97 kg/d per percentage point [p.p.] increase) and with farms that fed barley silage as their major forage source (n = 16; +2.18 kg/d) as compared with haylage (n = 42), whereas farms that fed corn silage (n = 96; +1.23 kg/d) tended to produce more milk than farms that fed haylage. Greater milk fat content (4.09 ± 0.28%) was associated with a greater PMR-to-AMS concentrate ratio (+0.02 p.p. per unit increase) and total diet net energy for lactation (+0.046 p.p. per 0.1 Mcal/kg increase), but a lesser percentage of NFC of the PMR (-0.016 p.p. per p.p. increase of NFC percentage). Milk protein content (3.38 ± 0.14%) was positively associated with the forage percentage of the PMR (+0.003 p.p. per p.p. increase of forage percentage) and the total diet starch percentage (+0.009 p.p. per p.p. increase of starch percentage), but was negatively associated with farms feeding corn silage (-0.1 p.p. compared with haylage) as their major forage. Greater milking frequency (2.77 ± 0.40 milkings/d) was observed on farms with free-flow cow traffic systems (+0.62 milkings/d) and was positively associated with feed push-up frequency (+0.013 milkings/d per additional feed push-up), but negatively associated with PMR NFC content and forage percentage of the total ration (-0.017 milkings/d per p.p. increase of forage percentage). Lastly, greater milking refusal frequency (1.49 ± 0.82 refusals/d) was observed on farms with free-flow cow traffic systems (+0.84 refusals/d) and farms feeding barley silage (+0.58 refusals/d) than with guided flow and farms feeding either corn silage or haylage, respectively. These data give insight into the ingredients, nutrient formulations and type of diets fed on AMS dairy farms across Canada and the association of those factors with milk production and milking behaviors.

Enhancing Pectin Particles with Polymer Additives: Mitigating Rumen Degradation and Minimizing Yellowish Milk Color in Grazed Cows

The pigments consumed in grazing give the milk from dual-purpose cows raised in tropical conditions a yellowish color, affecting the quality and price of the milk. This study aimed to develop an economical method with supplementary pectin to antagonize the availability of carotenes by designing microparticles with shellac and palm oil as a viable alternative to protect pectin degradation against rumen microbes. Three preparations of microparticles based on citrus pectin were synthesized: unprotected (PnP), protected with palm oil (PwP), and protected with palm oil and shellac (PwPL) microparticles. Samples were roughly characterized by spectroscopy and electron microscopy techniques. The effect of PnP, PwP, and PwPL on blood metabolites and physicochemical characteristics of the milk of grazing lactating cows was evaluated through in vivo assays. The release of citrus pectin from microparticles was determined as uronic acids using solutions with distinct pH, whereas its degradation was studied using in situ tests. Results revealed that PnP, PwP, and PwPL are amorphous structures with sizes that range from 60 to 265 nm or 750 to 3570 µm and have surface charges that range from -11.5 to -50.2 mV. Samples exhibited characteristic peaks during FTIR analyses that corresponded to O-H, C=O, and COOCH3 groups and bands within the UV-vis region that indicated the absorption of pectin. The EDS analysis revealed the presence of carbon, oxygen, or calcium in samples. The release of uronic acids was higher at pH 2-3 with PwPL. The in situ degradability of PnP, PwP, and PwPL was 99, 28.4, and 17.7%, respectively. Moreover, PwPL decreased the blood concentration of glucose, cholesterol, and lactate. In contrast, 100 g of pectin per animal daily during the feed process reduced yellow coloring. In conclusion, designing particles protected with lipids and polymers as shellac is an economical method that resists degradation at pH levels greater than five.

Effect of diets enriched in n-6 or n-3 fatty acid on dry matter intake, energy balance, oxidative stress, and milk fat profile of transition cows

The objective of this study was to determine the effect of dietary supplementation of n-3 polyunsaturated fatty acids (PUFA) and n-6 PUFA on dry matter intake (DMI), energy balance, oxidative stress, and performance of transition cows. Forty-five multiparous Holstein dairy cows with similar parity, body weight (BW), body condition score (BCS), and milk yield were used in a completely randomized design during a 56-d experimental period including 28 d prepartum and 28 d postpartum. At 240 d of pregnancy, cows were randomly assigned to one of the 3 isoenergetic and isoprotein dietary treatments, including a control ration containing 1% hydrogenated fatty acid (CON), a ration with 8% extruded soybean (HN6, high n-6 PUFA source), and a ration with 3.5% extruded flaxseed (HN3; high n-3 PUFA source). The HN6 and HN3 diets had an n-6/n-3 ratio of 3.05:1 and 0.64:1 in prepartum cows and 8.16:1 and 1.59:1 in postpartum cows, respectively. During the prepartum period (3, 2, and 1 wk before calving), DMI, DMI per unit of BW, total net energy intake, and net energy balance were higher in the HN3 than in the CON and NH6 groups. During the postpartum period (2, 3, and 4 wk after calving), cows fed HN3 and HN6 diets both showed increasing DMI, DMI as a percentage of BW, and total net energy intake compared with those fed the CON diet. The BW of calves in the HN3 group was 12.91% higher than those in the CON group. Yield and nutrient composition of colostrum (first milking after calving) were not affected by HN6 or HN3 but milk yield from 1 to 4 wk of milking was significantly improved compared with CON. During the transition period, BW, BCS, and BCS changes were not affected. Cows fed the HN6 diet had a higher plasma NEFA concentration compared with the CON cows during the prepartum period. Feeding HN3 reduced the proportion of de novo fatty acids and increased the proportion of preformed long-chain fatty acids in regular milk. In addition, the n-3 PUFA-enriched diet reduced the n-6/n-3 PUFA ratio in milk. In conclusion, increasing the n-3 fatty acids concentration in the diet increased both DMI during the transition period and milk production after calving, and supplementing n-3 fatty acids was more effective in mitigating the net energy balance after calving.

Milk and plasma proteomes from cows facing diet-induced milk fat depression are related to immunity, lipid metabolism and inflammation

Milk proteins are a source of bioactive molecules for calves and humans that may also reflect the physiology and metabolism of dairy cows. Dietary lipid supplements are classically used to modulate the lipid content and composition of bovine milk, with potential impacts on the nutrient's homeostasis and the systemic inflammation of cows that remains to be more explored. This study aimed at identifying discriminant proteins and their associated pathways in twelve Holstein cows (87 ± 7 days in milk), multiparous and non-pregnant, fed for 28 d a diet either, supplemented with 5% DM intake of corn oil and with 50% additional starch from wheat in the concentrate (COS, n = 6) chosen to induce a milk fat depression, or with 3% DM intake of hydrogenated palm oil (HPO, n = 6) known to increase milk fat content. Intake, milk yield and milk composition were measured. On d 27 of the experimental periods, milk and blood samples were collected and label-free quantitative proteomics was performed on proteins extracted from plasma, milk fat globule membrane (MFGM) and skimmed milk (SM). The proteomes from COS and HPO samples were composed of 98, 158 and 70 unique proteins, respectively, in plasma, MFGM and SM. Of these, the combination of a univariate and a multivariate partial least square discriminant analyses reveals that 15 proteins in plasma, 24 in MFGM and 14 in SM signed the differences between COS and HPO diets. The 15 plasma proteins were related to the immune system, acute-phase response, regulation of lipid transport and insulin sensitivity. The 24 MFGM proteins were related to the lipid biosynthetic process and secretion. The 14 SM proteins were linked mainly to immune response, inflammation and lipid transport. This study proposes discriminant milk and plasma proteomes, depending on diet-induced divergence in milk fat secretion, that are related to nutrient homeostasis, inflammation, immunity and lipid metabolism. The present results also suggest a higher state of inflammation with the COS diet.

Effects of adding rumen-protected palm oil in diet on milk fatty acid profile and lipid health indices in Kivircik ewes

This study aimed to determine the effect of the addition of rumen-protected palm oil making up 3% of the ration on lipid health indices and milk fatty acid composition of Kivircik ewes'. Kivircik ewes at two years of age, the same parity, lactation stage, and the same bodyweight (52.57 ± 5.80 kg) were chosen for this purpose. Two groups were formed, in which the control group was fed a basal diet without feed supplementation, whereas the treatment group received rumen-protected palm oil which corresponded to 3% of the ration. In order to protect palm oil, it was coated with calcium salts. Treatment increased the palmitic acid (C16:0) content of milk compared to the control group (P < 0.05) and tended to increase saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) (P = 0.14). An increase in SFA and MUFA was attributed to an increase in palmitic acid and oleic acid (C18:1), respectively (P < 0.05). Results indicated that the omega-6/omega-3 ratio (n-6/n-3) ranged between 0.61 and 2.63. The inclusion of palm oil in the diet tended to increase desirable fatty acids (DFAs) regardless of the week of milk sampled (P = 0.42). Treatment did not improve the atherogenicity index (AI), thrombogenicity index (TI), health-promoting index (HPI), and hypocholesterolemic/hypercholesterolemic (h/H) ratio. Results showed that adding rumen-protected palm oil is a plausible method to meet the energy intake of ewes required during lactation without negatively affecting lipid health indices.

Effect of prepartum dietary energy sources on productive and reproductive performance in Nili Ravi buffaloes

Feeding of dietary energy sources has been extensively studied in dairy cows but not well described in dairy buffaloes. The objective of this study was to evaluate the effect of prepartum dietary energy sources on productive and reproductive performance in Nili Ravi buffaloes (n = 21). The buffaloes were offered isocaloric (1.55 Mcal/kg DM NE_L (net energy for lactation)) glucogenic (GD), lipogenic (LD), and mixed diet (MD) during 63 days prepartum and maintained (1.27 Mcal/kg DM NE_L) at lactation diet (LCD) during 14 weeks postpartum. Effects of dietary energy sources and week on animals were analyzed with the mixed model. The DMI, BCS, and body weights remained similar during the pre- and postpartum periods. The prepartum diets did not affect birth weight, blood metabolites, milk yield, and composition. The GD tended to early uterine involution, more follicle numbers, and early follicle formation. The prepartum feeding of dietary energy source had a similar effect on first estrus expression, days open, conception rate, pregnancy rate, and calving interval. So, it could be concluded that prepartum feeding of an isocaloric dietary energy source had a similar effect on the performance of buffaloes.

Milk yield and composition in dairy goats fed extruded flaxseed or a high-palmitic acid fat supplement

We compared the potential of dietary lipid supplements of different fatty acid compositions to affect milk performance when early lactation dairy goats were fed a high-concentrate diet. Thirty Alpine goats at 23 ± 5 d in milk were allocated to 1 of 10 blocks according to parity and milk fat concentration. Within each block, goats were randomly assigned to receive, during a period of 41 d, either CONT) a basal diet with a forage to concentrate ratio of 45:55, used as control, or PALM) the basal diet + 2% of a palmitic acid-enriched fat supplement, or FLAX) the basal diet + 7% of extruded flaxseed. Body weight, dry matter intake and milk yield were not different between treatments. As compared with CONT, goats fed PALM and FLAX had a greater milk fat concentration. Moreover, milk fat yield was numerically (but non-significantly) greater with PALM than with CONT. Milk fat from goats receiving PALM had a greater concentration of 16:0 as compared with CONT and FLAX, whereas a greater concentration of cis-9, cis-12, cis-15 18:3 was observed when goats were fed FLAX as compared with CONT and PALM. Under the conditions of the current experiment, dietary fat supplementation had only minor impacts on the yield of major milk constituents, with the exception of a modest increase in fat yield when goats were fed PALM. The impact of a greater concentration of 16:0 in milk fat of goats receiving this feed ingredient on the nutritive value of dairy products remains to be determined.

Effects of feeding rumen-protected linseed fat to postpartum dairy cows on plasma n-3 polyunsaturated fatty acid concentrations and metabolic and reproductive parameters

High-yielding dairy cows experience a negative energy balance and inflammatory status during the transition period. Fat supplementation increases diet energy density, and plasma n-3 polyunsaturated fatty acids (PUFA) have been proposed to improve immune function. This study tested the hypothesis that dietary supplementation with a rumen-protected and n-3 PUFA-enriched fat could ameliorate both the energetic deficit and immune status of postpartum high-yielding dairy cows, improving overall health and reproductive efficiency. At 11 d in milk (DIM), cows were randomly allocated to groups (1) n-3 PUFA (n = 29), supplemented with encapsulated linseed oil supplying additional up to 64 g/d (mean 25 ± 4 g/d) of α-linolenic acid (ALA), or (2) control (n = 31), supplemented with hydrogenated palm oil without ALA content. Fat supplements of the n-3 PUFA and control groups were available through an automated, off-parlor feeding system, and intake depended on the cow's feeding behavior. Plasma ALA concentrations were higher in n-3 PUFA than control cows, following a linear relation with supplement ingestion, resulting in a lower n-6/n-3 ratio in plasma. Metabolic parameters (body condition score and glucose and β-hydroxybutyric acid blood concentrations) were unaffected, but milk yield improved with increased intake of fat supplements. Plasma total adiponectin concentrations were negatively correlated with ingestion of n-3 PUFA-enriched fat supplement, following a linear relation with intake. Conception rate to first AI increased with higher intake of both fats, but a decrease of calving-to-conception interval occurred only in n-3 PUFA cows. Postpartum ovarian activity and endometrial inflammatory status at 45 DIM were unaffected. In conclusion, this study evinced a positive linear relation between rumen-protected linseed fat intake and plasma n-3 PUFA concentrations, which modulated adiponectin expression and improved reproductive parameters.

Nutrient digetibility and production responses of lactating dairy cows when saturated free fatty acid supplements are included in diets: A meta-analysis

Our objective was to perform a series of meta-analyses to evaluate the effects of diets supplemented with saturated free fatty acid (FA) supplements (SFAA) compared with nonfat supplemented control diets (CON) on nutrient digestibility and production responses of lactating dairy cows and to determine whether experimental design affects responses to SFFA. We divided SFFA into C16:0-enriched supplements (PALM, FA supplements with ≥80% C16:0) and C16:0+C18:0-enriched supplements (MIX, FA supplements with ≥80% C16:0+C18:0). The database was formed from 32 peer-reviewed publications with SFFA supplemented at ≤3% diet dry matter (DM). We completed 3 different meta-analyses to meet our objectives. We analyzed the interaction between experimental design (continuous vs. change-over) and treatments (CON vs. SFFA; Meta.1). Regardless of experimental design, we evaluated the effect of treatment (CON vs. PALM vs. MIX; Meta.2) and the effect of 1-percentage-unit increase of MIX and PALM in diet DM (Meta.3). In Meta.1, there was no interaction between treatments and experimental design for any variable. In Meta.2, compared with CON, MIX had no effect on NDF digestibility, milk protein yield and energy corrected milk (ECM), increased the yields of milk (1.20 kg/d) and milk fat (0.04 kg/d), and decreased FA digestibility (5.20 percentage units). Compared with CON, PALM increased NDF digestibility (4.50 percentage units), the yields of milk (1.60 kg/d), milk fat (0.10 kg/d), milk protein (0.04 kg/d), and ECM (2.00 kg/d), and had no effect on FA digestibility. Compared with MIX, PALM tended to increase FA digestibility (3.20 percentage units), increased NDF digestibility (3.50 percentage units), milk fat yield (0.06 kg/d), and ECM (1.20 kg/d). In Meta.3, for each 1-percentage-unit increase of supplemental FA in diet DM, MIX had no effect on NDF digestibility, decreased FA digestibility, increased the yields of milk and milk fat, had no effect on milk protein yield, ECM and milk fat content, and decreased milk protein content. For each 1-percentage-unit increase of supplemental FA in diet DM, PALM increased NDF digestibility, had no effect on FA digestibility, increased the yields of milk, milk fat, ECM and milk fat content, tended to increase milk protein yield, and had no effect on milk protein content. Our results indicate no reason for the restrictive use of change-over designs in saturated FA supplementation studies and meta-analyses. Lactating dairy cows responded better to a FA supplement enriched in C16:0 compared with one containing C16:0 and C18:0.

Dietary fatty acid and starch content and supplemental lysine supply affect energy and nitrogen utilization in lactating Jersey cows

The effects of dietary fatty acid (FA) and starch content as well as supplemental digestible Lys (sdLys) on production, energy utilization, and N utilization were evaluated. Each factor was fed at 5 different amounts, and factor limits were as follows: 3.0 to 6.2% of dry matter (DM) for FA; 20.2 to 31.3% of DM for starch, and 0 to 17.8 g/d of sdLys. Dietary FA and starch were increased by replacing soyhulls with supplemental fat and corn grain, respectively, and sdLys increased with rumen-protected Lys. Fifteen unique treatments were fed to 25 Jersey cows (mean ± SD; 80 ± 14 d in milk) across 3 blocks in a partially balanced incomplete block design. Each block consisted of 4 periods of 28 d, where the final 4 d were used to determine milk production and composition, feed intake, energy utilization (via total collection and headbox-style indirect calorimetry), and N utilization (via total collection). Response surface models were used to evaluate treatment responses. Increasing dietary FA decreased DM intake and milk protein yield. When dietary starch was less than 24%, milk protein concentration increased with increasing sdLys, but when dietary starch was greater than 26% milk protein concentration decreased with increasing sdLys. Digestibility of FA increased when dietary FA increased from 3.0 to 4.2% and decreased as FA increased beyond 4.2%. Although neutral detergent fiber digestibility decreased as dietary starch increased, energy digestibility increased. As dietary FA increased, metabolizable energy (ME) content quadratically increased. Supply of ME increased as dietary FA increased from 3.0 to 4.2% and decreased as FA increased beyond 4.2%. Increasing dietary FA and starch decreased CH₄ production and urinary energy. Increasing dietary starch increased the efficiency of utilizing dietary N for milk N. Increasing sdLys quadratically decreased N balance as sdLys increased from 0 to 8 g/d and increased N balance as sdLys increased from 8 to 18 g/d. Increasing dietary FA can increase ME content, however, at high dietary FA, decreased DM intake and FA digestibility resulted in a plateau in ME content and a decrease in ME supply. Our results demonstrate that sdLys supply is important for milk protein when dietary starch is low, and some Lys may be preferentially used for muscle protein synthesis at the expense of milk protein when sdLys is high.

Effect of concentrate enriched with palmitic acid versus rapeseed oil on dairy performance, milk fatty acid composition, and mammary lipogenic gene expression in mid-lactation Holstein cows

This study was performed to characterize the effect of a concentrate supplemented with free palmitic acid (4% on a DM basis; PA) or rapeseed oil (4% on a DM basis; RO) compared with a no-added-lipid control concentrate (CT) on the performance of dairy cows fed a corn silage-based diet over a 9-wk period. After a 3-wk pre-experimental period, 54 Holstein cows were randomly allocated to 3 experimental treatments to receive forage ad libitum with a fixed amount of CT, RO, or PA (8 kg/d for 2-yr-old primiparous; 10 kg/d for older cows). During the experiment, dry matter intake, milk yield and composition, fatty acid (FA) yields and FA profile, and feed efficiency were determined. At wk 9 of the experimental period, the mRNA levels of 10 genes involved in lipid metabolism in mammary tissue biopsy samples were measured. Compared with CT, RO and PA increased forage intake. Compared with CT, RO increased concentrate intake, the value being intermediate for PA. Compared with CT, RO increased milk yield (+2.0 kg/d) and decreased milk fat and protein content (-3.8 and -1.2 g/kg, respectively), whereas PA increased milk fat content (+4.1 g/kg). Compared with CT and RO treatments, PA increased milk fat yield (+179 g/d) and 3.5% fat-corrected milk and energy-corrected milk output (+2.8 and +2.3 kg/d, respectively), and thus improved feed efficiency (+7.3%). Compared with CT treatment, RO increased milk contents of the sum of >C16 FA, monounsaturated FA, polyunsaturated FA, trans FA, and n-3 FA, whereas PA decreased these FA contents (except n-3 FA) and also decreased n-6 FA. The variations in milk fat yield and content and FA secretion at wk 9 were not associated with modifications in mammary expression of 10 genes involved in major lipid pathways, except for the transcription factor PPARG1, which tended to be higher in PA versus RO treatment. This study demonstrated that PA improved milk fat yield and feed efficiency compared with RO and suggests that factors other than gene expression, such as substrate availability for mammary metabolism or other levels of regulation (transcriptional, posttranscriptional, translational or posttranslational), could play a key role in milk fat and FA responses to changes in diet composition in cows.

Compositional and functional properties of milk and dairy products derived from cows fed pasture or concentrate-based diets

Worldwide milk production is predominantly founded on indoor, high-concentrate feeding systems, whereas pasture-based feeding systems are most common in New Zealand and Ireland but have received greater attention recently in countries utilizing conventional systems. Consumer interest in 'pasture-fed' dairy products has also increased, arising from environmental, ethical, and nutritional concerns. A substantial body of research exists describing the effect of different feeding strategies on the composition of milk, with several recent studies focusing on the comparison of pasture- and concentrate-based feeding regimes. Significant variation is typically observed in the gross composition of milk produced from different supplemental feeds, but various changes in the discrete composition of macromolecular components in milk have also been associated with dietary influence, particularly in relation to the fatty acid profile. Changes in milk composition have also been shown to have implications for milk and dairy product processability, functionality and sensory properties. Methods to determine the traceability of dairy products or verify marketing claims such as 'pasture-fed' have also been established, based on compositional variation due to diet. This review explores the effects of feed types on milk composition and quality, along with the ultimate effect of diet-induced changes on milk and dairy product functionality, with particular emphasis placed on pasture- and concentrate-based feeding systems.

Effects of fat supplements containing different levels of palmitic and stearic acid on milk production and fatty acid digestibility in lactating dairy cows

Fat supplements based on palmitic acid (PA) or stearic acid (SA) are expected to have different effects on milk production and nutrient metabolism in lactating dairy cows. In this study, the effects of prilled fat supplements containing different levels of PA and SA were tested in 12 high-producing multiparous cows (pretrial milk yield = 53.4 ± 8.7 kg/d; mean ± SD) arranged in a 4 × 4 Latin square design with 21-d periods. Treatments were control (CON; no supplemental fat), an enriched PA supplement (HP; 91% C16:0), an enriched SA supplement (HS; 92.5% C18:0), and a blend of PA and SA (INT) fed at 1.95% of diet dry matter. All supplements contained oleic acid at approximately 5% of fatty acids. The HP treatment decreased dry matter intake (DMI) by 1.9 kg/d and 1.1 kg/d compared with SA and CON, respectively. Milk yield was not changed by treatment, but INT increased energy-corrected milk by 2.7 kg/d compared with HS. The HP and INT treatments increased milk fat yield by 0.11 and 0.14 kg/d compared with CON, respectively. Additionally, HP decreased yield of <16 carbon fatty acids (FA; de novo synthesized) by 44 g/d and 43 g/d compared with INT and CON, respectively. The HP treatment increased 16-carbon FA (mixed source) by 155 g/d compared with CON and 64 g/d relative to INT. No effect of treatment on apparent total-tract digestibility of dry matter, organic matter, or neutral detergent fiber was detectable. The INT and HS treatments decreased total-tract digestibility of 16-carbon FA by 10.3 and 10.5 percentage units compared with HP, respectively. Total-tract digestibility of 18-carbon FA was lowest in the HS diet and highest with HP. In conclusion, supplementing PA increased milk fat yield compared with control and SA, but supplementing a mixture of PA and SA increased energy-corrected milk without decreasing intake. The FA profile of fat supplements influences their digestibility and effects on DMI and milk and milk fat synthesis.

Effect of supplementing palmitic acid and altering the dietary ratio of n-6:n-3 fatty acids in low-fibre diets on production responses of dairy cows

Supplementing palmitic acid (C16 : 0) in combination with modifying the dietary n-6:n-3 fatty acid (FA) ratio may benefit energy metabolism and milk responses of dairy cows. Twelve Holstein cows (70 (sd 11) days in milk) were used in a replicated 4 × 4 Latin square and allocated to four low-fibre diets (18·5 % forage neutral-detergent fibre) supplemented with no FA (CON), or 2·4 % C16 : 0-enriched supplement (PAL), 2·4 % mixture (2:1) of C16 : 0 and n-6 FA (PW6), and mixture (2:1) of C16 : 0 and n-3 FA (PW3). The dietary ratio of n-6:n-3 was increased with PW6 (10:1) and decreased with PW3 (2·8:1), whereas PAL alone made no change in the ratio (about 7:1). Compared with CON, all FA-supplemented treatments increased milk yield. However, feed and energy intakes were higher in PAL than PW3 or PW6, resulting in greater feed efficiency for PW3 and PW6 than PAL. Dietary FA supplements decreased milk protein concentration but tended to increase protein yield. Compared with CON and FA mixtures, PAL increased milk fat content and tended to increase milk SFA and atherosclerotic index. The concentration of milk n-3 FA was similar between CON and PW3. Feeding PAL increased milk energy output and decreased energy partitioning towards body reserves (-4·2 %), while this measure was positive for other treatments. Blood TAG and NEFA concentrations, but not β-hydroxybutyrate, were increased by FA-supplemented treatments. Feeding C16 : 0 combined with either n-6 or n-3 FA enhanced feed efficiency, alleviated the negative impacts on body energy reserves, but lowering the dietary n-6:n-3 ratio improved the FA profile of milk.

Scale-up of two-step acid-catalysed glycerol pretreatment for production of oleaginous yeast biomass from sugarcane bagasse by Rhodosporidium toruloides

Two-step dilute acid and acid-catalysed glycerol pretreatment was developed to maximise sugar yield from sugarcane bagasse. At the laboratory scale, dilute acid pretreatment at 130 °C followed by acid-catalysed glycerol pretreatment at 170 °C led to a total sugar (C5 + C6) yield of 82%, 31% higher than that from one-step acid-catalysed glycerol pretreatment. At the pilot scale, the two-step dilute acid and acid-catalysed glycerol pretreatment led to a maximum sugar yield of 74%, 13% higher than that from one-step pretreatment with 52% reduction in glycerol usage. The enzymatic hydrolysate containing glucose and residual glycerol were used to produce microbial oils by a Rhodosporidium toruloides strain. A fed-batch cultivation strategy led to the production of 44.8 g/L cell mass, including 26.6 g/L oil, 8.6 g/L protein and 12.7 mg/L carotenoid. The cell mass and oil yields were 19% higher than those from batch cultivation as feedstock inhibition and catabolite repression were alleviated.

Effect of feeding a palmitic acid-enriched supplement on production responses and nitrogen metabolism of mid-lactating Holstein and Jersey cows

This study evaluated the effect of feeding a palmitic acid-enriched supplement on production responses and nitrogen metabolism of mid-lactating Holstein and Jersey cows. Eighty mid-lactating dairy cows, 40 Holstein and 40 Jersey, were used in a randomized complete block design with a split-plot arrangement; the main plot was breed and the subplot was fatty acid treatment. Cows within each breed were assigned to 1 of 2 treatments: (1) control diet with no fat supplement or (2) control diet plus a palmitic acid-enriched supplement dosed at 1.5% of diet dry matter (PA treatment). The treatment period was 6 wk with the final 3 wk used for data and sample collection. There were no treatment × breed interactions for the variables analyzed. Compared with control, PA treatment increased milk fat yield (1.36 vs. 1.26 kg/d) and tended to increase 3.5% fat-corrected milk (35.6 vs. 34.0 kg/d) and energy-corrected milk (35.7 vs. 34.1 kg/d). There was no effect of PA treatment on dry matter intake, milk yield, milk protein yield, milk lactose yield, body condition score, body weight (BW) change, nitrogen intake, and variables related to nitrogen metabolism and excretion. Compared with Holstein cows, Jersey cows had greater dry matter intake as a percent of BW (4.90 vs. 3.37% of BW) and lower milk production (29.6 vs. 32.7 kg/d) and milk lactose yield (1.58 vs. 1.42 kg/d), but tended to have greater milk fat yield (1.36 vs. 1.26 kg/d). There was a breed effect on BW change; Holstein cows gained 0.385 kg/d during the experiment, and Jersey cows gained 0.145 kg/d. Jersey cows had lower nitrogen intake (636 vs. 694 g/d), blood urea nitrogen (12.6 vs. 13.8 mg/dL), urine total nitrogen (125 vs. 145 g/d), and urine total nitrogen as a percent of nitrogen intake (19.5 vs. 21.1%). Overall, feeding a palmitic acid-enriched supplement increased milk fat yield as well as dry matter and fiber digestibility in both Holstein and Jersey cows. The PA treatment did not have any major effects on nitrogen metabolism in both Holstein and Jersey cows. In addition, our results indicated that Jersey cows had lower urinary nitrogen excretion (g/d) than Holstein cows.

Short communication: Diets supplemented with starch and corn oil, marine algae, or hydrogenated palm oil differently affect selected metabolite concentrations in cow and goat milk

The objective was to investigate the effects of species (cow vs. goat) and of various dietary lipid supplements, known to modulate milk fat content, on selected metabolites and enzymes in milk and to explore their correlations with performance traits. Twelve Holstein cows and 12 Alpine goats, all multiparous and nonpregnant, and at 86 ± 24.9 and 61 ± 1.8 DIM, respectively, were fed a basal diet (45% forage + 55% concentrate) not supplemented (CTL) or supplemented with corn oil plus wheat starch [COS, 5% of diet dry matter (DM)], marine algae powder (MAP, 1.5% of diet DM), or hydrogenated palm oil (HPO, 3% of diet DM) in a replicated 4 × 4 Latin square design with 28-d experimental periods. Intake, milk production and composition, milk fatty acid profile, and plasma metabolite concentrations were previously reported. Concentrations of 9 milk metabolites [β-hydroxybutyrate (BHB), glucose, glucose-6-phosphate, isocitrate, choline, glutamate, urea, cholesterol, and free amino groups] and 2 milk enzyme activities (alkaline phosphatase and lactate dehydrogenase) were measured on d 24 of each experimental period. Dairy performance data showed marked species and diet effects on milk fat content. Irrespective of diet, cow milk was richer in alkaline phosphatase and glucose compared with goat milk (16 and 3 times more, respectively), whereas goat milk had greater urea and glucose-6-phosphate concentrations compared with cow milk (1.9 and 5.3 times more, respectively). In cows, COS decreased milk BHB and choline (-25 and -43%, respectively) compared with CTL, whereas no effects were observed in goats. The COS and MAP diets increased milk isocitrate compared with CTL in cows, but COS decreased isocitrate concentrations in goat milk. Milk choline was correlated with milk fat content in cows (Spearman r, r_S = +0.73) and goats (r_s = +0.58), and lactate dehydrogenase activity was correlated with milk somatic cell count (r_s = +0.66) in cows but not in goats. We provide evidence of different milk metabolite responses according to species and diets. Metabolites and enzymes secreted in milk may be indicators of specificities of lipid metabolism among ruminant species and may contribute to a better understanding of mechanisms regulating milk fat secretion. Changes in the concentrations of some metabolites considered minor components of milk may be valuable diagnostic tools of mammary gland and animal metabolism as well as of milk processing characteristics.

Effects of supplement amount, with or without calcium salts of fatty acids, on growth performance and intake behavior of grazing Bos indicus bulls

This study evaluated the effects of 2 supplement dry matter (DM) amounts, with or without calcium salts of fatty acids (CSFA), on growth performance, supplement and water intake behavior of grazing beef bulls. On day 0, 32 Nellore bulls were ranked by initial body weight (BW; 318 ± 11.2 kg), and then, randomly assigned to treatments (n = 8 bulls/treatment), in a 2 × 2 factorial design, which consisted of energy-based supplement DM amount of 0.3 (SP03) or 1.0 (SP1) % of BW with (+) or without (-) CSFA fortification (90 to 100 g/bull daily). During the experiment (98 d), all bulls were managed as single group and rotated between 2 Brachiaria pastures every 9 to 11 d. Each pasture contained an individual electronic data capture system with 2 feed bunks/treatment and 1 water through to determine individual supplement DM and water intake, as well number of visits, time spent at the feeder/waterer, and intake per visit (IPV). A supplement effect was detected (P = 0.02) for final BW. Bulls supplemented at 1.0% of BW, regardless of CSFA inclusion amount, were heavier at the end of the experiment vs. SP03 bulls. Overall average daily gain (ADG) was greater (P = 0.05) for SP03+ vs. SP03- bulls, and did not differ (P = 0.87) between SP1+ vs. SP1- bulls. No supplement amount, CSFA, or supplement amount × CSFA effects were observed (P ≥ 0.13) for supplement and water intake behavior, number of visits to the feeder or IPV. However, SP1 bulls spent (P = 0.05) more time at the feeder than SP1+ bulls, whereas bulls supplemented with CSFA tended (P = 0.10) to consume less water (as % of BW) than cohorts supplemented without CSFA. In summary, CSFA fortification into 0.3% of BW supplements increased ADG when compared with cohorts not offered CSFA. On the other hand, no benefits were observed when CSFA was included into 1.0% of BW supplements, primarily due to the lower than projected supplement, and consequently, CSFA intake. Moreover, CSFA fortification tended to reduced water intake, demonstrating a potential of this technology to increase performance of beef herds, while maintaining the utilization of natural resources.

Palmitic acid-enriched fat supplementation alleviates negative production responses during early lactation of Holstein dairy cows

Effects of rumen-protected fat (RPF) on suppressing the negative performance responses in early lactation period of Holstein dairy cows were investigated. Three hundred multiparous Holstein cows (647 ± 16 kg bodyweight and 90 days in milk (DIM)) were randomly housed into three free-stall barns (100 cows per barn) and assigned to the treatments for 90 days, as follows: (1) control (CTL) diet without RPF; (2) calcium salt of palm fatty acids (CaFA) 30 g/kg DM, and (3) fractionated fatty acids of palm oil (FFA) 25 g/kg DM. Cows were fed total mixed ration containing 580 g of concentrate and 420 g of roughage per kilogram DM. Cows fed FFA exhibited a higher (P &lt; 0.05) DM intake and body condition score than did those fed CaFA or CTL diets respectively. Moreover, cows fed the FFA diet showed decreased (P &lt; 0.05) changes to bodyweight at 30 DIM and to body condition score at 60 DIM and increased digestibility of ether extract and neutral detergent fibre. Blood concentrations of triglycerides, cholesterol and glucose were higher (P &lt; 0.05) for cows fed FFA diet than for those fed the other diets, between 4 and 30 DIM, whereas concentrations of non-esterified fatty acids, β-hydroxybutyric acid and urine ketones were lower for cows fed RPF sources (P &lt; 0.05). Relative to CTL diet, CaFA and FFA diets increased (P &lt; 0.05) milk yield and milk fat content at 4–30 DIM. Feeding FFA improved feed efficiency by 8.9% (P = 0.006), between 31 and 60 DIM, compared with CaFA. Inclusion of a palmitic acid-enriched fat supplement in Holstein cow diet increased milk yield and fat content and mitigated the deleterious effects of metabolic disorders during the early lactation period.

Influence of rumen bypass fat supplementation during early lactation in tropical crossbred dairy cattle

The present study investigated the influence of rumen bypass fat-supplemented total mixed ration (TMR) on milk production of tropical crossbred, dairy cows. Twelve stall-fed, tropical crossbred, dairy cows were studied from calving to 15 weeks of lactation. The cows were 397.6 kg in body weight and produced 9.14 L/cow/day milk at the first week of lactation. The experiment was on a complete randomized design with two treatments (i.e., basal diet alone and basal diet with bypass fat supplement) each consisting six (n = 6) replicate cows. During the experimental period, while cows of both treatments were individually fed with respective basal diet (TMR), only the cows allocated for experimental dietary treatment were supplemented with rumen bypass fat (200 g/cow/day) containing calcium salts of long-chain fatty acids. Feed intake, body weight (BW), and milk yield of cows were recorded. Proximate composition of feed, milk composition, and blood metabolic profile of cows were assessed. Dry matter intake and BW of cows were not affected (P > 0.05) by supplementation of rumen bypass fat. The cows supplemented with bypass fat had recorded significantly higher (P < 0.05) milk production compared with cows that did not receive bypass fat supplements until eleventh week of the lactation. As such, bypass fat supplementation resulted 132.38 L/cow higher (P < 0.05) cumulative milk production at 15 weeks compared with their counterparts (1142 vs. 1010 L/cow). But, milk fat, solid non-fat (SNF), protein, and milk urea nitrogen (MUN) contents were not influenced (P < 0.05) by bypass fat supplementation. Bypass fat-supplemented cows had comparatively greater (P < 0.05) serum non-esterified fatty acids (NEFA) level around 6-8 weeks of lactation. However, the serum metabolites' (i.e., NEFA, betahydroxy butyric acid (BHBA), albumin, calcium, and phosphorous) contents of both treatments varied within their respective reference range throughout the experiment. Neither the fat-supplemented cows nor their counterparts experienced negative energy balance (NEB). Benefit cost ratio of bypass fat supplementation confirmed that there is a direct financial benefit of bypass fat supplementation until 12.7th week of lactation. In conclusion, bypass fat supplementation with TMR feeding during early lactation is recommended to increase the milk production of tropical crossbred dairy cows with medium production.

Saturated fat supplemented in the form of triglycerides decreased digestibility and reduced performance of dairy cows as compared to calcium salt of fatty acids

The two most popular rumen-protected fatty acid supplements in dairy cow rations are calcium salts of palm oil fatty acid calcium salts of palm oil fatty acid (CSFA) and prilled saturated fatty acids (SFAs). The objectives of this study were to determine the effects of supplementing SFA in the form of triglycerides (TSFA), as compared to CSFA, on yields, efficiency and diet digestibility in high-yielding dairy cows. Twenty-eight (14 cows in each group) multiparous cows were fed a basal diet supplemented (on DM basis) with either 12 g/kg TSFA (~350 g/cow per day - contained 980 g/kg fat; 882.3 g/kg SFAs) or 14 g/kg CSFA (~440 g/cow per day - contained 800 g/kg fat; 566.4 g/kg SFAs). The supplement amounts in the diet were balanced according to fat content. Rumen samples were taken for measurements of ammonia and volatile fatty acids concentrations, and fecal samples were taken for digestibility measurements. The CSFA cows produced 3% higher milk yields (47.6 v. 46.2 kg/day; P < 0.0001) and 4.7% higher 4% fat-corrected milk (FCM; 44.7 v. 42.7 kg/day; P = 0.02) than the TSFA cows. No difference in milk-fat content was observed, but milk-protein content was higher in the TSFA than CSFA cows. Yields of fat and protein were similar, but lactose yields were higher in TSFA cows. There were no differences in dry matter intake or efficiency calculations between groups. The ruminal ammonia concentrations were similar between groups, whereas acetate concentrations and acetate : propionate ratio were greater for CSFA than TSFA cows. The apparent total-tract digestibility of dry (P < 0.0007) and organic matters (P < 0.0003), fat (P < 0.0001), NDF and ADF (P = 0.02) were lower in the TSFA v. CSFA cows. In conclusion, the CSFA-supplemented cows produced 3% higher milk and 4.7% higher 4% FCM than the TSFA cows. However, TSFA supplementation did not depress milk-protein content. The apparent total-tract digestibility was lower for all dietary components in the TSFA cows, which was probably due to the effects of both degree of saturation and triglyceride form of the TSFA supplement. Considering that diets were balanced according to the fat content of the supplements, the lower yields of milk and FCM observed in the TSFA than CSFA cows were likely due to the lower digestibility of the fat and other nutrients in the TSFA cows, which might have negatively influenced the dietary energy content.

Milk production and nutrient digestibility responses to triglyceride or fatty acid supplements enriched in palmitic acid

The objective of our study was to evaluate the effects of feeding triglyceride and fatty acid (FA) supplements enriched in palmitic acid (PA; C16:0) on production and nutrient digestibility responses of mid-lactation dairy cows. Fifteen Holstein cows (137 ± 49 d in milk) were randomly assigned to a treatment sequence in a 3 × 3 Latin square design. Treatments consisted of a control diet (CON; no added PA) or 1.5% FA added as either a FA supplement (PA-FA) or a triglyceride supplement (PA-TG). The PA supplements replaced soyhulls, and diets were balanced for glycerol content. Periods were 21 d in length with sample and data collection occurring during the final 5 d. Compared with CON, PA treatments increased dry matter (66.5 vs. 63.9%) and neutral detergent fiber (NDF) apparent digestibility (42.0 vs. 38.2%). Although PA treatments tended to increase 18-carbon FA apparent digestibility (79.1 vs. 77.9%), PA treatments decreased 16-carbon (63.1 vs. 75.8%) and total FA (72.0 vs. 76.5%) apparent digestibilities compared with CON. The PA treatments increased milk fat content (3.60 vs. 3.41%), milk fat yield (1.70 vs. 1.60 kg/d), yield of 16-carbon milk FA (570 vs. 471 g/d), 3.5% fat-corrected milk (47.6 vs. 46.5 kg/d), and energy-corrected milk (47.4 vs. 46.6 kg/d) compared with CON. The PA treatments did not affect dry matter intake (28.5 vs. 29.2 kg/d), milk yield (47.0 vs. 47.4 kg/d), milk protein yield (1.42 vs. 1.45 kg/d), milk lactose yield (2.29 vs. 2.31 kg/d), yield of <16-carbon milk FA (360 vs. 370 g/d), yield of >16-carbon milk FA (642 vs. 630 g/d), body weight (720 vs. 723 kg), or body condition score (3.14 vs. 3.23). We did not observe differences in digestibilities of dry matter, NDF, and 18-carbon FA between PA-TG and PA-FA. In contrast, PA-FA increased 16-carbon (68.6 vs. 57.6%) and total FA apparent digestibility (73.8 vs. 70.1%) compared with PA-TG. This resulted in PA-FA supplementation increasing the apparent digestibility of the PA supplement by ∼10 percentage points compared with PA-TG. Compared with PA-TG, PA-FA increased 16-carbon FA intake by 60 g/d, absorbed 16-carbon FA by 86 g/d, and absorbed total FA by 85 g/d. Compared with PA-TG, PA-FA increased dry matter intake (29.1 vs. 27.8 kg/d), yield of 16-carbon milk FA (596 vs. 545 g/d), and tended to increase milk yield (47.6 vs. 46.4 kg/d), milk fat yield (1.70 vs. 1.66 kg/d), and 3.5% fat-corrected milk (48.1 vs. 47.2 kg/d). In conclusion, the production response of dairy cows to PA tended to be greater for a FA supplement compared with a triglyceride supplement. Overall, PA increased NDF digestibility, milk fat yield, energy-corrected milk, and feed efficiency in mid-lactation dairy cows.

Comparison of oil and fat supplementation on lactation performance of Nili Ravi buffaloes

The effects of feeding rumen-inert fat sources on production responses of lactating dairy cows have been well reported but less thoroughly described in lactating dairy buffalo. The objective of this study was to investigate the effect of oil and 2 different rumen-inert fat sources on dry matter intake, milk yield, milk composition, and milk fatty acid (FA) profile in Nili Ravi buffalo. Twelve multiparous mid-lactating Nili Ravi buffaloes received 4 treatments in a 4 × 4 Latin square design with a period length of 21 d. The treatments were (1) the basal diet without supplementation of oil or fats (CTRL), (2) the basal diet supplemented with canola oil (CO), (3) the basal diet supplemented with calcium salts of palm FA (Ca-FA), and (4) the basal diet supplemented with high palmitic acid (PA). Dry matter intake was decreased by 4.4% in the CO compared with Ca-FA and PA. Milk yield and milk fat yield were increased by 7.8 and 14.3%, respectively, in CO, Ca-FA, and PA compared with the CTRL. Milk fat content increased by 7.5%, whereas milk fat yield tended to increase with the supplementation of Ca-FA and PA compared with CO. No effect on milk yield and milk composition was observed in Ca-FA versus PA treatments. The yield of medium-chain FA was increased by Ca-FA and PA versus CO. The CO treatment increased the yield of long-chain FA compared with Ca-FA and PA treatments. Plasma glucose level was higher in CO, Ca-FA, and PA compared with the CTRL. In conclusion, feeding rumen-inert fats in the lactating buffalo diet proved to be a useful strategy to increase the 3.5% fat-corrected milk yield due to the higher milk fat content in this study.

Dietary supplementation with glucogenic precusors and fatty acids improves performance and health of periparturient dairy cows

This experiment aimed to make a comparison between the effect of a mix of two energy preparations (a glucogenic preparation (G) and a free fatty acid preparation (F)), administered in the diet during the transition period over different periods of time (5 or 8 weeks), on the animal condition, feed intake, yield and composition of milk, and blood and urine parameters. The experimental additive was a mixture (1:1) of two energy preparations, namely, a loose mixture of propylene glycol and sodium propionate and a free fatty acid preparation in the form of rumen-undegradable pellets. The study included 50 Polish Black-and-White Holstein–Friesian dairy cows, allocated into five treatment groups, including one control (C) and four experimental ones (G1F1, G2F2, G2F1 and G1F2). The preparations were mixed at a 1:1 weight ratio (500 g per head, comprising 250G and 250F) and they were administered to all experimental groups of cows daily as a component of the experimental concentrate for 5 weeks (from the 2nd week before the expected calving and until the 3rd week of lactation). From the 4th until the 6th week of lactation, the supplementation in the experimental groups changed and animals received either no additive (G1F1), or were continuously supplemented with the G–F mix (G2F2), or received only G (G2F1) or only F (G1F2). The preparations used in the study had a long-term influence on the increase in the milk yield of cows, on the improvement of their health condition, and on the reduction of weight loss. The study results confirmed that prolongation of the supplementation until the 6th week of lactation may cause favourable changes in animal performance and milk quality. Due to different modes of action, the simultaneous supplementation of G and F reduced the negative energy balance in the cow and improved milk production and composition. The best results were obtained after administration of the mixture (1:1) of the G and F at the dose of 500 g/cow.day over the 8-week periparturient period.

Effects of starch-rich or lipid-supplemented diets that induce milk fat depression on rumen biohydrogenation of fatty acids and methanogenesis in lactating dairy cows

Optimizing milk production efficiency implies diets allowing low methane (CH4) emissions and high dairy performance. We hypothesize that nature of energy (starch v. lipids) and lipid supplement types (monounsaturated fatty acid (MUFA) v. polyunsaturated fatty acid (PUFA) mitigate CH4 emissions and can induce low milk fat content via different pathways. The main objective of this experiment was to study the effects of starch-rich or lipid-supplemented diets that induce milk fat depression (MFD) on rumen biohydrogenation (RBH) of unsaturated fatty acids (FA) and enteric CH4 emissions in dairy cows. Four multiparous lactating Holstein cows (days in milk=61±11 days) were used in a 4×4 Latin square design with four periods of 28 days. Four dietary treatments, three of which are likely to induce MFD, were based (dry matter basis) on 56% maize silage, 4% hay and 40% concentrates rich in: (1) saturated fatty acid (SFA) from Ca salts of palm oil (PALM); (2) starch from maize grain and wheat (MFD-Starch); (3) MUFA (cis-9 C18:1) from extruded rapeseeds (MFD-RS); and (4) PUFA (C18:2n-6) from extruded sunflower seeds (MFD-SF). Intake and milk production were measured daily. Milk composition and FA profile, CH4 emissions and total-tract digestibility were measured simultaneously when animals were in open-circuit respiration chambers. Fermentation parameters were analysed from rumen fluid samples taken before feeding. Dry matter intake, milk production, fat and protein contents, and CH4 emissions were similar among the four diets. We observed a higher milk SFA concentration with PALM and MFD-Starch, and lower milk MUFA and trans-10 C18:1 concentrations in comparison to MFD-RS and MFD-SF diets, while trans-11 C18:1 remained unchanged among diets. Milk total trans FA concentration was greater for MFD-SF than for PALM and MFD-Starch, with the value for MFD-RS being intermediate. Milk C18:3n-3 content was higher for MFD-RS than MFD-SF. The MFD seems more severe with MFD-SF and MFD-RS than PALM and MFD-Starch diets, because of a decrease in milk SFA concentration and a stronger shift from trans-11 C18:1 to trans-10 C18:1 in milk. The MFD-SF diet increased milk trans FA (+60%), trans-10 C18:1 (+31%), trans-10,cis-12 CLA (+27%) and PUFA (+36%) concentrations more than MFD-RS, which explains the numerically lowest milk fat yield and indicates that RBH pathways of PUFA differ between these two diets. Maize silage-based diets rich in starch or different unsaturated FA induced MFD with changes in milk FA profiles, but did not modify CH4 emissions.

Embryonic development, luteal size and blood flow area, and concentrations of PGF2α metabolite in dairy cows fed a diet enriched in polysaturated or polyunsaturated fatty acid

The objective of this study was to examine effects of sunflower (SO) and palm oil (PO) supplements in the diet on embryonic development, luteal size and blood flow area, PGF2α metabolite (PGFM), and progesterone (P4) concentrations. Prepartum cows (n = 42) were randomly assigned to one of three dietary treatments (control, 4% PO, and 4% SO supplements). Animals were fed diets individually from day 28 prepartum to day 111 postpartum. Luteal size and blood flow area were determined throughout the estrous cycle by Doppler ultrasonography. Oocytes were collected in three ovum pick-up sessions at 2 week intervals for the in vitro embryo production. Oocyte characteristics and embryonic development were not affected by dietary treatments. Cows fed 4% SO had a greater (P < 0.05) concentration of PGFM from day 15 to day 35 postpartum than those cows fed 4% PO and the control group. On day 11 of the estrous cycle (mid-luteal phase), serum P4 concentrations (6.0 ± 0.7, 5.7 ± 0.5, and 4.7 ± 0.6 ng/ml), luteal size (7.0 ± 0.2, 6.5 ± 0.2, and 5.3 ± 0.1 cm2) and luteal blood flow area (1.3 ± 0.2, 1.2 ± 0.1, and 0.9 ± 0.1 cm2) were greater (P < 0.05) in cows fed 4% SO and 4% PO than the control group, respectively. Thus, plant oil supplements in diets affected luteal size and serum P4 and PGFM concentrations, but not early embryonic development. Such changes in secretion of PGF2α and P4 indicate that plant oil supplements during pre- and postpartum may alter uterine and luteal functions.

A 100-Year Review: Fat feeding of dairy cows

Over 100 years, the Journal of Dairy Science has recorded incredible changes in the utilization of fat for dairy cattle. Fat has progressed from nothing more than a contaminant in some protein supplements to a valuable high-energy substitute for cereal grains, a valuable energy source in its own right, and a modifier of cellular metabolism that is under active investigation in the 21st century. Milestones in the use of fats for dairy cattle from 1917 to 2017 result from the combined efforts of noted scientists and industry personnel worldwide, with much of the research published in Journal of Dairy Science. We are humbled to have been asked to contribute to this historical collection of significant developments in fat research over the past 100 years. Our goal is not to detail all the work published as each development moved forward; rather, it is to point out when publication marked a significant change in thinking regarding use of fat supplements. This approach forced omission of critically important names and publications in many journals as ideas moved forward. However, we hope that a description of the major changes in fat feeding during the past 100 years will stimulate reflection on progress in fat research and encourage further perusal of details of significant events.

Diets supplemented with starch and corn oil, marine algae, or hydrogenated palm oil differentially modulate milk fat secretion and composition in cows and goats: A comparative study

A direct comparative study of dairy cows and goats was performed to characterize the animal performance and milk fatty acid (FA) responses to 2 types of diets that induce milk fat depression in cows as well as a diet that increases milk fat content in cows but for which the effects in goats are either absent or unknown. Twelve Holstein cows and 12 Alpine goats, all multiparous, nonpregnant, and at 86 ± 24.9 and 61 ± 1.8 DIM, respectively, were allocated to 1 of 4 groups and fed diets containing no additional lipid (CTL) or diets supplemented with corn oil [5% dry matter intake (DMI)] and wheat starch (COS), marine algae powder (MAP; 1.5% DMI), or hydrogenated palm oil (HPO; 3% DMI), according to a 4 × 4 Latin square design with 28-d experimental periods. Dietary treatments had no significant effects on milk yield and DMI in both species, except for COS in cows, which decreased DMI by 17%. In cows, milk fat content was lowered by COS (-45%) and MAP (-22%) and increased by HPO (13%) compared with CTL, and in goats only MAP had an effect compared with CTL by decreasing milk fat content by 15%. In both species, COS and MAP lowered the yields (mmol/d per kg of BW) of <C16 and C16 FA. With COS, this decrease was compensated by an increase of >C16 FA in goats, but not in cows, and the >C16 FA yield decreased with MAP in both species. HPO supplementation increased the milk yield of C16 FA in cows. Compared with CTL, COS induced an increase of trans-10,cis-12 conjugated linoleic acid by 18 fold in cows and 7 fold in goats and of trans-10 18:1 by 13 fold in cows and 3 fold in goats. Moreover, other conjugated linoleic acid isomers, such as trans-10,trans-12 and trans-7,cis-9, were increased to a greater extent in cows (8 and 4 fold, respectively) compared with goats (4 and 2 fold, respectively) on the COS treatment. In both species, the responses to MAP were characterized by a decrease in the milk concentration of 18:0 (3 fold, on average) and cis-9 18:1 (2 fold, on average) combined with a 3-fold increase in the total trans 18:1, with an increase in trans-10 18:1 only observed in cows. Compared with CTL, the response to HPO was distinguished by an increase in 16:0 (10%) in cows. This comparative study clearly demonstrated that each ruminant species responds differently to COS and HPO treatments, whereas MAP caused similar effects, and that goats are less sensitive than cows to diets that induce a shift from the trans-11 toward the trans-10 ruminal pathways.

Effects of fat supplementation to diets high in nonforage fiber on production responses of midlactation dairy cows

The effects of dietary nonforage fiber sources on production responses of lactating dairy cattle have been well described, but interactions with other components of the diet have been less thoroughly explored. We investigated the effects of adding 2 commonly fed fat sources to a ration featuring high levels of nonforage fiber supplied by a corn milling by-product. Midlactation Holstein cows were blocked by parity, stratified by days in milk, and randomly assigned to 1 of 6 pens (12 cows/pen). Pens were randomly assigned to treatment sequences in a 3 × 3 Latin square design, where the treatments consisted of prilled saturated fat (SAT; Energy Booster 100, Milk Specialties Co., Dundee, IL), calcium salts of long-chain fatty acids (UNS; Megalac, Church and Dwight Co. Inc., Princeton, NJ), or no added dietary fat (control), with fat sources included to provide 1.2% added fat (dry matter basis). Treatment periods were 21 d; milk and feed samples were collected and milk yield and feed intake were recorded for the last 4 d of each period. Results were analyzed with mixed models with pen as the experimental unit, and orthogonal contrasts were employed to evaluate the overall effect of added fat and the effect of fat source. Dry matter intake and milk yield tended to increase with added fat. Protein content decreased with fat supplementation, to a greater degree for UNS than for SAT, but protein yield was not affected. Fat content, fat yield, and energy-corrected milk yield were not affected by treatment. Conversion of feed to milk tended to increase for UNS compared with SAT. Fat supplementation to diets high in nonforage fiber had effects that were similar to those reported for more traditional lactation diets, except for the dry matter intake response.

Effect of palmitic acid on the mitigation of milk fat depression syndrome caused by trans-10, cis-12-conjugated linoleic acid in grazing dairy cows

The objective of the study was to evaluate the effect of adding protected palmitic acid (PA) to the ration of grazing dairy cows supplemented with protected conjugated linoleic acid (CLA) on milk production, chemical composition and fat profile. Six cows were used, 3/4 American Swiss × Zebu, under a rotational grazing system in a mixed sward with Cynodon plectostachyus, Brachiaria decumbens and Brachiaria brizantha. Furthermore, each cow received daily 4 kg concentrates and 8 kg sorghum silage, which made up the basal diet. The cows were distributed into three two-cow groups. Three treatments were randomly assigned to the groups, using a cross design: (1) control (basal diet), (2) basal diet + CLA (50 g/d) and (3) basal diet + CLA (50 g/d) + PA (412 g/d). The following variables were evaluated: forage intake, milk production, protein, fat and lactose concentration in milk, and milk fatty acid (FA) profile. There were no differences in forage intake between treatments; however, there were differences in milk production, protein, fat and lactose yield and fat concentration, which increased significantly in group CLA + PA when compared with group CLA. The concentration of FA synthesised de novo was lower when PA was included in the diet. Adding PA to the diet of grazing cows mitigates the milk fat decline caused by including trans-10, cis-12 CLA in the diet.

Production responses of Holstein dairy cows when fed supplemental fat containing saturated free fatty acids: a meta-analysis

OBJECTIVE

A meta-analysis was conducted to evaluate the effects of supplemental fat containing saturated free fatty acids (FA) on milk performance of Holstein dairy cows.

METHODS

A database was developed from 21 studies published between 1991 and 2016 that included 502 dairy cows and a total of 29 to 30 comparisons between dietary treatment and control without fat supplementation. Only saturated free FA (>80% of total FA) was considered as the supplemental fat. Concentration of the supplemental fat was not higher than 3.5% of diet dry matter (DM). Dairy cows were offered total mixed ration, and fed individually. Statistical analysis was conducted using random- or mixed-effects models with Metafor package in R.

RESULTS

Sub-group analysis showed that there were no differences in studies between randomized block design and Latin square/crossover design for dry matter intake (DMI) and milk production responses to the supplemental fat (all response variables, p≥0.344). The supplemental fat across all studies improved milk yield, milk fat concentration and yield, and milk protein yield by 1.684 kg/d (p<0.001), 0.095 percent unit (p = 0.003), 0.072 kg/d (p<0.001), and 0.036 kg/d (p<0.001), respectively, but tended to decrease milk protein concentration (mean difference = -0.022 percent unit; p = 0.063) while DMI (mean difference = 0.061 kg/d; p = 0.768) remained unchanged. The assessment of heterogeneity suggested that no substantial heterogeneity occurred among all studies for DMI and milk production responses to the supplemental fat (all response variables, I2≤24.1%; p≥0.166).

CONCLUSION

The effects of saturated free FA were quantitatively evaluated. Higher milk production and yields of milk fat and protein, with DMI remaining unchanged, indicated that saturated free FA, supplemented at ≤3.5% dietary DM from commercially available fat sources, likely improved the efficiency of milk production. Nevertheless, more studies are needed to assess the variation of production responses to different saturated free FA, either C16:0 or C18:0 alone, or in combination with potentially optimal ratio, when supplemented in dairy cow diets.

Nutrient digestibility and milk production responses to increasing levels of palmitic acid supplementation vary in cows receiving diets with or without whole cottonseed

Our study evaluated the dose-dependent effects of a palmitic acid-enriched supplement in basal diets with or without the inclusion of whole cottonseed on nutrient digestibility and production responses of dairy cows. Sixteen Holstein cows (149 ± 56 days in milk) were used in a split plot Latin square design experiment. Cows were blocked by 3.5% fat-corrected milk (FCM) and allocated to a main plot receiving either a basal diet with soyhulls (SH, = 8) or a basal diet with whole cottonseed (CS, = 8) that was fed throughout the experiment. A palmitic acid-enriched supplement (PA 88.5% C16:0) was fed at 0, 0.75, 1.50, or 2.25% of ration DM in a replicated 4 × 4 Latin Square design within each basal diet group. Periods were 14 d with the final 4 d used for data collection. PA dose increased milk fat content linearly, and cubically affected yields of milk fat and 3.5% FCM. The PA dose did not affect milk protein and lactose contents, BW, and BCS, but tended to increase yields of milk, milk protein, and milk lactose. Also, PA dose reduced DMI and 16-carbon fatty acid digestibility quadratically, and increased 18-carbon fatty acid digestibility quadratically. There were no effects of basal diet on the yield of milk or milk components, but DMI tended to decrease in CS compared with SH, increasing feed efficiency (3.5% FCM/DMI). Compared with SH, CS diets increased yield of preformed milk fatty acids and 16-carbon fatty acid digestibility, and tended to decrease 18-carbon fatty acid digestibility. We observed basal diet × PA dose interactions for yields of milk and milk protein and for 16-carbon and total fatty acid digestibility, as well as tendency for yields of milk fat and 3.5% FCM. Also, there was a tendency for an interaction between basal diet and PA dose for NDF digestibility, which increased more for CS with increasing PA than for SH. PA dose linearly decreased digestibility of total fatty acids in SH diets but did not affect it in CS diets Results demonstrate that responses to PA dose are affected by the dietary basal diet. Additionally, the decrease in fatty acid digestibility only in the SH diets suggests that digestibility is impacted mainly by the profile of 16- and 18-carbon fatty acids reaching the duodenum. Under the dietary conditions evaluated, the yield of 3.5% FCM and milk fat were optimal when PA was fed at 1.5% of ration DM.

Effects of common dietary fatty acids on milk yield and concentrations of fat and fatty acids in dairy cattle

The objective of the present article was to summarise the effects of five common dietary fatty acids (C16:0, C18:0, C18:1, C18:2 and C18:3) on the major milk fat groups (<C16, C16 and C18). Forty published papers were reviewed to evaluate the effect of adding free fat or oil supplements rich in C16 and C18 fatty acids on the response of milk fat secretion and composition. From those 40 studies, 21 were used to investigate the effect of total dietary concentration of C16:0, C18:0, C18:1, C18:2 and C18:3 on milk secretion or concentrations of milk <C16, C16 and C18 fatty acid groups. The results indicated that C16 supplementation increased total milk fatty acids, mainly by increasing milk C16 yield, without affecting milk <C16 and C18 yield. Supplements rich in unsaturated fatty acid decreased total milk fatty acid by inhibiting secretion of milk fatty acids shorter than C18, with linoleic acid being the most inhibitory. Mixtures of feed fatty acid (C16:0 + C18:0 and C16:0 + C18:1) did not significantly affect total milk fatty acid yield. According to regression of milk C16 yield on dietary fatty acid, endogenous C16 contributes ~80% of total milk C16, but this proportion varies with the level and type of dietary fatty acid fed. Milk mid-infrared analysis can be used to routinely measure the presence of milk <C16 fatty acid, the concentration of which provides a good indicator of inhibition of milk fatty acid secretion. In contrast, measurement of total milk fat content is less effective as a diagnostic tool due to the masking effect of the exogenous supply of C16 and C18 dietary fatty acids.

Effects of α-linolenic acid-enriched diets on gene expression of key inflammatory mediators in immune and milk cells obtained from Holstein dairy cows

Immune system and inflammatory responses are affected by α-linolenic acid (αLA: 18:3 ω-3). The objective of this study was to determine the effects of αLA-enriched rations on gene expression of systemic (blood) and local (mammary gland) inflammatory markers in Holstein dairy cattle. Further, the effect of dietary treatments was evaluated on the concentration of αLA in serum phospholipids. Camelina (Camelina sativa) meal (containing 24.2% αLA) was fed at 0, 3, 6, and 9% (dry matter basis) replacing canola meal (rich in 18:1 ω-9) to provide rations with incremental concentrations of αLA. Lactating primiparous Holstein cows (n = 18) were randomly assigned to a treatment sequence in a 4 × 4 Latin square design. Each period lasted 16 d and milk and blood samples were collected during the final 2 d of each period. Peripheral blood mononuclear cells (PBMC) and milk cells (MC) were harvested, and RNA extracted and converted to complementary DNA for quantitative real time PCR analysis. The effect of dietary treatments (αLA) on the relative abundance of pro- and anti-inflammatory genes in the PBMC and MC was tested by the MIXED procedure of SAS. Expression of pro-inflammatory tumour necrosis factor (TNF)-α in MC was linearly reduced (up to 40%) as dietary αLA increased. Expression of pro-inflammatory markers interleukin (IL)-1β, IL-8, and TNF-α was reduced (29, 20, and 27%, respectively) in PBMC isolated from cows fed 6% camelina meal ration as compared with cows fed 0% (control). Expression of IL-6 was, however, increased with inclusion of camelina meal. Greater dietary αLA linearly increased serum phospholipids αLA contents, and when fed up to 6% DM down-regulated expression of some of the local (milk) and systemic (blood) pro-inflammatory markers in vivo.

Palmitic acid feeding increases ceramide supply in association with increased milk yield, circulating nonesterified fatty acids, and adipose tissue responsiveness to a glucose challenge

Reduced insulin action is a key adaptation that facilitates glucose partitioning to the mammary gland for milk synthesis and enhances adipose tissue lipolysis during early lactation. The progressive recovery of insulin sensitivity as cows advance toward late lactation is accompanied by reductions in circulating nonesterified fatty acids (NEFA) and milk yield. Because palmitic acid can promote insulin resistance in monogastrics through sphingolipid ceramide-dependent mechanisms, palmitic acid (C16:0) feeding may enhance milk production by restoring homeorhetic responses. We hypothesized that feeding C16:0 to mid-lactation cows would enhance ceramide supply and ceramide would be positively associated with milk yield. Twenty multiparous mid-lactation Holstein cows were enrolled in a study consisting of a 5-d covariate, 49-d treatment, and 14-d posttreatment period. All cows were randomly assigned to a sorghum silage-based diet containing no supplemental fat (control; n=10; 138±45 d in milk) or C16:0 at 4% of ration dry matter (PALM; 98% C16:0; n=10; 136±44 d in milk). Blood and milk were collected at routine intervals. Liver and skeletal muscle tissue were biopsied at d 47 of treatment. Intravenous glucose tolerance tests (300mg/kg of body weight) were performed at d -1, 24, and 49 relative to start of treatment. The plasma and tissue concentrations of ceramide and glycosylated ceramide were determined using liquid chromatography coupled with tandem mass spectrometry. Data were analyzed as repeated measures using a mixed model with fixed effects of treatment and time, and milk yield served as a covariate. The PALM treatment increased milk yield, energy-corrected milk, and milk fat yield. The most abundant plasma and tissue sphingolipids detected were C24:0-ceramide, C24:0-monohexosylceramide (GlcCer), and C16:0-lactosylceramide. Plasma concentrations of total ceramide and GlcCer decreased as lactation advanced, and ceramide and GlcCer were elevated in cows fed PALM. Palmitic acid feeding increased hepatic ceramide levels, a response not observed in skeletal muscle tissue. Plasma ceramides (e.g., C24:0-ceramide) were positively correlated with plasma NEFA and milk yield, and positively correlated with NEFA levels following a glucose challenge. Our data demonstrate a remodeled plasma and hepatic sphingolipidome in mid-lactation dairy cows fed PALM. The potential involvement in ceramide in homeorhetic nutrient partitioning to support lactation requires further consideration.

Increasing palmitic acid intake enhances milk production and prevents glucose-stimulated fatty acid disappearance without modifying systemic glucose tolerance in mid-lactation dairy cows

Feeding saturated fatty acids may enhance milk yield in part by decreasing insulin sensitivity and shifting glucose utilization toward the mammary gland. Our objective was to evaluate the effects of palmitic acid (C16:0) on milk production and insulin sensitivity in cows. Twenty multiparous mid-lactation Holstein cows were enrolled in a study consisting of a 5-d covariate, 49-d treatment, and 14-d posttreatment period. All cows received a common sorghum silage-based diet and were randomly assigned to a diet containing no supplemental fat (control; n=10; 138±45d in milk) or C16:0 at 4% of ration DM (PALM; 98% C16:0; n=10; 136±44d in milk). Blood and milk were collected at routine intervals. Intravenous glucose tolerance tests (300mg/kg of body weight) were performed at d -1, 24, and 49 relative to start of treatment. Data were analyzed as repeated measures using a mixed model with fixed effects of treatment and time, and milk yield served as a covariate. The PALM treatment increased milk yield by wk 7. Furthermore, PALM increased milk fat yield and energy-corrected milk at wk 3 and 7. Changes in milk production occurred in parallel with enhanced energy intake. Increased milk fat yield during PALM treatment was due to increased C16:0 and C16:1 incorporation; PALM had no effect on concentration of milk components, BW, or body condition score. Two weeks posttreatment, energy-corrected milk and milk fat yield remained elevated in PALM-fed cows whereas yields of milk were similar between treatments. Increased milk fat yield after PALM treatment was due to increased de novo lipogenesis and uptake of preformed fatty acids. The basal concentration of nonesterified fatty acids (NEFA) in plasma increased by d 4, 6, and 8 of PALM treatment, a response not observed thereafter. Although PALM supplementation did not modify insulin, glucose, or triacylglycerol levels in plasma, total cholesterol in plasma was elevated by wk 3. Estimated insulin sensitivity was lower during the first week of PALM treatment; however, glucose disposal following glucose tolerance tests was not modified. In contrast, C16:0 feeding reduced glucose-stimulated NEFA disappearance by wk 7. Results demonstrate that increasing dietary energy from C16:0 for 7wk improves milk yield and milk composition without modifying systemic glucose tolerance. Reduced glucose-stimulated NEFA disappearance with C16:0 feeding and elevated circulating NEFA may reflect changes in adipose tissue insulin sensitivity.

Short communication: Lactational responses to palmitic acid supplementation when replacing soyhulls or dry ground corn

The objective of this study was to evaluate the response of mid-lactation dairy cows to a palmitic acid (C16:0)-enriched fatty acid supplement when replacing soyhulls or dry ground corn in the diet. Twenty-four multiparous Holstein cows (182 ± 60 d in milk; mean ± SD) were blocked by preliminary 3.5% fat-corrected milk and randomly assigned to treatment sequence in a replicated 3 × 3 Latin square design with 21-d periods. Treatments consisted of a control diet containing no supplemental fat (CON), and 2 C16:0-enriched fatty acid-supplemented treatments (PA; BergaFat F100, Berg & Schmidt, Hanover, Germany) as a replacement for either soyhulls (PA-SH) or dry ground corn (PA-CG). The C16:0-enriched supplement was fed at 1.5% of diet dry matter. The PA treatments did not affect dry matter intake, but PA-SH increased dry matter intake by 1.4 kg/d compared with PA-CG. The PA treatments did not affect milk yield; however, PA-SH increased milk yield by 2.4 kg/d compared with PA-CG. The PA treatments tended to decrease milk protein content (3.12 vs. 3.15%). In contrast, PA-SH increased milk protein content (3.14 vs. 3.10%) and milk protein yield (1.27 vs. 1.19 kg/d) compared with PA-CG. The PA treatments increased milk fat concentration (3.68 vs. 3.55%) and milk fat yield (1.46 vs. 1.38 kg/d). The increase in milk fat yield with PA treatments was due to the increase in the yield of 16-carbon fatty acid in milk fat. Furthermore, PA-SH tended to increase yield of de novo fatty acids and yield of 16-carbon fatty acids compared with PA-CG. The PA treatments tended to increase feed efficiency (3.5% fat-corrected milk/dry matter intake) compared with CON (1.51 vs. 1.46). The PA-SH treatment tended to increase insulin concentration compared with PA-CG (1.58 vs. 1.49 μg/L) and PA treatments increased nonesterified fatty acids compared with CON (110 vs. 99 μEq/L). Overall, PA treatments improved feed efficiency and increased milk fat yield and the response to the C16:0-enriched fatty acid supplement was greater when it replaced soyhulls compared with when it replaced dry ground corn in the diet.