Modeling fatty acids for dairy cattle: Models to predict total fatty acid concentration and fatty acid digestion of feedstuffs

Abstract

Development of predictive models of fatty acid (FA) use by dairy cattle still faces challenges due to high variation in FA composition among feedstuffs and fat supplements. Two meta-analytical studies were carried out to develop empirical models for estimating (1) the total FA concentration of feedstuffs, and (2) the apparent total-tract digestibility of total FA (DCFA TTa ) in dairy cows fed different fat types. In study 1, individual feedstuff data for total crude fat (EE) and FA were taken from commercial laboratories (total of 203 feeds, 1,170,937 samples analyzed for total FA, 1,510,750 samples analyzed for total EE), and data for FA composition were collected from the Cornell Net Carbohydrate and Protein System feed library. All feedstuffs were grouped into 7 classes based on their nutritional components. To predict total FA concentration (% of dry matter) for groups of feeds, the total EE (% of dry matter) was used as an independent variable in the model, and all models were linear. For forages, data were weighted using the inverse of the standard error (SE). Regression coefficients for predicting total FA from EE (% of dry matter) were 0.73 (SE, 0.04), 0.98 (0.02), 0.80 (0.02), 0.61 (0.04), 0.92 (0.03), and 0.93 (0.03), for animal protein, plant protein, energy sources, grain crop forage, by-product feeds, and oilseeds, respectively. The intercepts for plant protein and byproduct groups were different from zero and included in the models. As expected, forages had the lowest total FA concentration (slope = 0.57, SE = 0.02). In study 2, data from 30 studies (130 treatment means) that reported DCFA TTa in dairy cows were used. Data for animal description, diet composition, intakes of total FA, and DCFA TTa , were collected. Dietary sources of fat were grouped into 11 categories based on their fat characteristic and FA profile. A mixed model including the random effect of study was used to regress digested FA on FA intake with studies weighted according to the inverse of their variance (SE). Dietary intake of extensively saturated triglycerides resulted in markedly lower total FA digestion (DCFA TTa = 44%) compared with animals consuming unsaturated FA, such as Casalts of palm (DCFA TTa = 76%) and oilseeds (DCFA TTa = 73%). Cows fed saturated fats had lower total FA digestion among groups, but it was dependent on the FA profile of each fat source. The derived models provide additional insight into FA digestion in ruminants. Predictions of total FA supply and its digestion can be used to adjust fat supplementation programs for dairy cows.

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

“…First, studies feeding highly pure PA and SA with minimal to no unsaturated fat report large decreases in digestibility. The recent analysis by Daley et al (2020) reported that supplements containing >90% PA or SA negatively influenced FA digestibility compared with more moderately enriched supplements or blends of PA and SA. For example, Piantoni et al (2013) reported that a 99% C16:0 PA supplement decreased total and C16 FA digestibility by 10.1 and 17.4 percentage units, and Piantoni et al (2015) showed that a 98% C18:0 supplement decreased total FA digestibility by 19.5 units and C18 digestibly by 23.8 units with no effect on C16 digestibility.…”

“…Supplements predominantly containing SA have been reported to have little effect on DMI, but this has been investigated to a lesser extent and primarily in prills with very low levels of unsaturated FA (Piantoni et al, 2015;Boerman et al, 2017). Rico et al (2014b) directly compared PA and SA supplements, but utilized very high-purity supplements, which tend to have low digestibility (Daley et al, 2020). Blends of PA and SA have been most extensively investigated, and gener-ally PA combined with SA does not affect DMI (Allen, 2000) but does increase milk, milk fat, and milk protein yields (Hu et al, 2017).…”

“…The digestibility of PA and SA is complicated by few direct comparisons of PA and SA within the same study. The digestibility of a fat supplement is influenced by factors such as feeding rate, level of basal fat in the ration, and FA profile (Boerman et al, 2015;Daley et al, 2020) and may also be affected by level of intake, laboratory methodology, and other study-specific factors, making comparing digestibility across studies difficult.…”

Nutrient production in pastures of Triticale BRS Saturno submitted to different levels of nitrogen in topdressing

“…In the total production of ether extract (Table 5) and linoleic (C18: 2) and linolenic (C18: 3) fatty acids, there was a significant increase (P <0.05) due to the addition of topdressing nitrogen fertilization, but it did not influence (P >0.05) the production of oleic fatty acid (C18: 1). Recently, Tran et al (2020) and Daley, Armentano, Kononoff and Hanigan (2020) presented the results of scientific studies carried out in the United States of America, aiming to detail the fatty acid composition of the foods offered to dairy cows since the partitioning of fibrous and non-fibrous carbohydrates and nitrogen constituents are already well determined through the Cornell Net Carbohydrate and Protein System (CNCPS), and their effects on animals and the products generated (meat and milk) are understood. However, it is still essential to better understand the effects of lipids.…”

Models to predict milk fat concentration and yield of lactating dairy cows: A meta-analysis

“…Previously derived coefficients for total-tract, apparent digestibility of total FA for each dietary fat source (Daley et al, 2020) were used to calculate digested intakes of total FA. For AA, the diet composition and DMI were used to calculate the intakes of each AA (Arg, His, Ile, Leu, Lys, Met, Phe, Thr, Val).…”