Milk production responses to altering the dietary ratio of palmitic and oleic acids varies with production level in dairy cows.

We evaluated the effects of altering the dietary ratio of palmitic (C16:0; PA) and oleic (cis-9 C18:1; OA) acids on production responses of cows with a wide range of milk production (32 to 65 kg/d) in a crossover design experiment with a preliminary period. Thirty-two multiparous Holstein cows (144 ± 54 d in milk) were assigned randomly to a treatment sequence. Treatments were diets supplemented with fatty acid (FA) blends (1.5% of diet dry matter) that provided 80% C16:0 + 10% cis-9 C18:1 (PA) and 60% C16:0 + 30% cis-9 C18:1 (PA+OA). The corn silage and alfalfa-based diets contained 20.0% forage neutral detergent fiber (NDF), 28.5% starch, and 17.1% crude protein. Treatment periods were 21 d with the final 5 d used for data and sample collection. Treatment did not affect dry matter intake (DMI), milk yield, energy-corrected milk (ECM), body weight, or body weight change. The PA+OA diet increased total, 16-carbon, and 18-carbon FA digestibility compared with the PA diet. Compared with PA+OA, PA increased fat yield (1.97 vs. 1.91 kg/d) and protein yield (1.61 vs. 1.55 kg/d). The PA diet also increased the yield of de novo (448 vs. 428 g/d) and mixed (749 vs. 669 g/d) milk FA and decreased the yield of preformed FA (605 vs. 627 g/d) compared with PA+OA. Interactions were detected between treatment and preliminary milk yield for DMI, total FA intake, 16-carbon FA intake, ECM, 3.5% fat-corrected milk (linear interaction), and a tendency for milk yield (linear interaction); lower-producing cows (<45 kg/d) had increased DMI and ECM on the PA diet, whereas higher-producing cows (>55 kg/d) had increased DMI and ECM on the PA+OA diet. A linear interaction was detected between treatment and preliminary milk yield for mixed milk FA yield (linear interaction) and a tendency for de novo milk FA yield (linear interaction). Our results demonstrate that feeding a fat supplement containing more cis-9 C18:1 replacing C16:0 increased production responses (DMI, milk yield, and ECM) in higher-producing cows, but decreased production responses in lower-producing 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.