Effect of dietary inclusion of winter brassica crops on milk production, feeding behavior, rumen fermentation, and plasma fatty acid profile in dairy cows.

This study determined feeding behavior, dry matter (DM) intake (DMI), rumen fermentation, and milk production responses of lactating dairy cows fed with kale (Brassica oleracea) or swede (Brassica napus ssp. napobrassica). Twelve multiparous lactating dairy cows (560 ± 22 kg of body weight, 30 ± 4 kg of milk/d, and 60 ± 11 d in milk at the beginning of the experiment; mean ± standard deviation) were randomly allocated to 3 dietary treatments in a replicated 3 × 3 Latin square design. The control diet comprised 10 kg of grass silage DM/d, 4 kg of ryegrass herbage DM/d, and 8.8 kg of concentrate DM/d. Then, 25% of herbage, silage, and concentrate (DM basis) was replaced with either kale or swede. Cows offered kale had decreased total DMI compared with cows fed the control and swede diets, whereas inclusion of swede increased eating time. Milk production, composition, and energy-corrected milk:DMI ratio were not affected. Cows fed with kale had a greater rumen acetate:propionate ratio, whereas swede inclusion increased the relative percentage of butyrate. Estimated microbial N was not affected by dietary treatments, but N excretion was reduced with inclusion of kale, improving N utilization. Cows fed kale tended to have increased nonesterified fatty acids and showed presence of Heinz-Ehrlich bodies, whereas hepatic enzymes such as aspartate aminotransferase, γ-glutamyl transferase, and glutamate dehydrogenase were not affected by dietary treatments. In plasma, compared with the control, swede and kale reduced total saturated fatty acids and increased total polyunsaturated fatty acids and total n-3 fatty acids. Overall, feeding cows with winter brassicas had no negative effect on production responses. However, mechanisms to maintain milk production were different. Inclusion of swede increased the time spent eating and maintained DMI with a greater relative rumen percentage of butyrate and propionate, whereas kale reduced DMI but increased triacylglycerides mobilization, which can negatively affect reproductive performance. Thus, the inclusion of swede may be more suitable for feeding early-lactating dairy cows during winter.

Use of the Comprehensive Climate Index to estimate heat stress response of grazing dairy cows in a temperate climate region.

The aim of the study was to assess the effect of the summer thermal environment on physiological responses, behaviour, milk production and its composition on grazing dairy cows in a temperate climate region, according to the stage of lactation. Twenty-nine Holstein Friesian multiparous cows were randomly selected and divided into two groups, according to the days in milk, as mid-lactation (99 to 170 d in milk, n = 15) and late lactation (225 to 311 d in milk, n = 14). The comprehensive climate index (CCI) was used to classify the hour of each day as thermoneutral or heat stress, considering a threshold value of CCI of 20°C. Data were collected for 16 d (summer 2017) and analysed as a completely randomized 2 × 2 factorial arrangement with repeated measurements over time. Vaginal temperature increased with CCI ≥ 20°C. Respiration rates were dependent on the thermal condition, regardless of days in milk. There was an interaction between the time of day and the CCI category for activity and rumination. Grazing activity decreased by 17.6% but lying down, standing, and shaded animals increased by 1.6, 9.8, and 6.3% respectively when CCI ≥ 20°C. Over 80% of cows presented a panting score ≥1. However, milk production and composition (fat, protein, and lactose concentrations as well as somatic cell count) were not affected by the thermal condition, although there was a numerical (non-significant) decrease in afternoon milk protein concentration on days with CCI ≥ 20°C, while urea in milk increased. In conclusion, thermal condition challenged grazing dairy cows' behaviour and physiology independent of the stage of lactation but had little or no effect on milk production.

Effect of forage brassicas in dairy cow diets on the fatty acid profile and sensory characteristics of Chanco and Ricotta cheeses.

In humid temperate regions, forage turnip (Brassica rapa ssp. rapa) and forage rape (Brassica napus ssp. biennis) are common fodder crops used for dairy cattle during the summer season. However, there is little scientific information regarding the use of brassicas and their effect on the fatty acid (FA) profile in blood, milk, and milk products. The aim of this study was to evaluate the effect of forage brassica supplementation in dairy cows on the FA profile of blood plasma, milk, and cheese, and on the sensory characteristics of Chanco and Ricotta cheeses. Twelve multiparous dairy cows (Holstein Friesian) were housed and submitted to a 3 × 3 replicated (n = 3) Latin square design with 3 treatments (control, turnip, or rape) in 3 periods of 21 d each (14 d of diet adaptation and 7 d of measurements). The control diet consisted of 16.20 kg of grass silage (Lolium perenne), 2.25 kg of soybean bran, and 2.25 kg of commercial concentrate, all on a dry matter (DM) basis. In the treatments with forage brassicas, 24.15% of the total DM was replaced by turnip or rape; thus, they consisted of 12.25 kg of silage, 2.25 kg of soybean bran, 1.2 kg of concentrate, and 5 kg of turnip or rape (DM basis). A principal components analysis was performed on the results of the cheese sensory evaluation. Supplementation with turnip or rape modified the profile of FA in blood plasma and milk, increasing the saturated fraction, mainly short- and medium-chain FA, and decreasing the mono- and polyunsaturated FA. In the sensory evaluation, diet did not affect any of the 18 attributes evaluated. However, in the principal components analysis, cheeses made with milk from animals fed turnip and rape were differentiated by increased odor, flavor, spiciness, bitterness, and acidity. Overall, brassicas can be used as an alternative forage source with no negative effects on sensory characteristics of cheeses.

Research Note: Characterization of peasant family poultry farming in Southern Chile.

The poultry industry produces most of the meat and eggs for human consumption worldwide. However, family poultry farming still plays an important role in developing countries providing high quality animal products including eggs and poultry meat for family and local consumption. A field survey was taken to 145 family poultry farmers off the commune of Maullin, Los Lagos Region of Southern Chile, to describe their husbandry and breeding practices, and provide information for future development and conservation priorities. Egg production in these poultry systems of the Maullín commune is a family tradition, run mostly by women, provides an extra income from the sale of extra eggs and chicken meat during autumn and winter months. Flocks of 15 to 30 native, creole or indigenous hens, reach point of lay at 5 or 6 months old. Egg production with a mean rate of 40%, peaks during September. Brown eggs are the most frequent, followed by blue-greenish eggs derived from Mapuche fowl ancestry. A ratio of 10 to 20 females per rooster results in ca. 60% hatching rate from natural incubation. While males are kept for two seasons only, females are kept longer, some until old. Diet is based on locally available or self-produced grains, complemented by pasture browsing, scavenging, and kitchen waste. Sanitary management is low or none and technical knowledge derives from ancestral tradition. Investment in accommodation and feeding is low. Results provide information on these systems in non-tropical areas of developing countries where it is scarce, and highlights how these systems can respond to the challenges of future poultry production, considering both climate change and consumers demand for more wholesome, human and sustainable products.

The Replacement of Ground Corn with Sugar Beet in the Diet of Pasture-Fed Lactating Dairy Cows and Its Effect on Productive Performance and Rumen Metabolism.

(1) Background: Sugars have a potential to provide great amounts of fermentable energy in the rumen. Feeding fresh sugar beet (SB) to dairy cattle to replace a portion of the grain in the ration has not received sufficient attention. This study determined dry matter intake (DMI), feeding behavior, rumen fermentation and milk production responses when replacing corn grain with increasing levels of SB in pasture-fed lactating dairy cow diets. (2) Methods: A total of 12 early-lactation cows were used in a replicated (n = 4) 3 × 3 Latin square design. The control diet consisted of 21 kg dry matter (DM) composed of 6.3 kg DM green chopped perennial ryegrass, 7 kg DM grass silage, 2 kg DM of concentrate, 1 kg DM soybean meal and 4.5 kg DM of ground corn. The other treatments replaced 50% or 100% of the ground corn with SB roots. (3) Results: The replacement of ground corn with sugar beet reduced DMI and milk yield (p < 0.05), but it increased milk fat concentration (p = 0.045), reduced feeding costs and increased margin over feed costs (p < 0.01). Urinary nitrogen was linearly reduced with SB supplementation (p = 0.026). (4) Conclusions: Using SB roots as energetic supplement can be a suitable alternative to ground corn in pasture-fed lactating dairy cows.

Effects of Sugar Beet Silage, High-Moisture Corn, and Corn Silage Feed Supplementation on the Performance of Dairy Cows with Restricted Daily Access to Pasture.

A study was undertaken to assess the effect of supplementation with sugar beet silage, corn silage, or high-moisture corn on dairy performance, rumen, and plasma metabolites in dairy cows under conditions of restricted grazing in spring. Eighteen multiparous Holstein Friesian cows, stratified for milk yield (39.4 kg/day ± 3.00), days of lactation (67.0 days ± 22.5), live weight (584 kg ± 38.0), and number of calves (5.0 ± 1.5), were allocated in a replicated 3 × 3 Latin square design. Treatments were as follows: SBS (10 kg DM of permanent pasture, 7 kg DM of sugar beet silage, 4 kg DM of concentrate, 0.3 kg DM of pasture silage, 0.21 kg of mineral supplement); corn silage (10 kg DM of permanent pasture, 7 kg DM of corn silage, 4 kg DM of concentrate, 0.3 kg DM of pasture silage, 0.21 kg of mineral supplement), and HMC (10 kg DM of permanent pasture, 5 kg DM of high-moisture corn, 4.5 kg DM of concentrate, 1.2 kg DM of pasture silage, 0.21 kg of mineral supplement). Pasture was offered rotationally from 9 a.m. to 4 p.m. Between afternoon and morning milking, the cows were housed receiving a partial mixed ration and water ad libitum. The effect of treatments on milk production, milk composition, body weight, rumen function, and blood parameters were analyzed using a linear−mixed model. Pasture dry matter intake (DMI) was lower in SBS than CS (p < 0.05) and similar to HMC, but total DMI was higher in HMC than SBS (p < 0.05) and similar to CS. Milk production for treatments (32.6, 31.7, and 33.4 kg/cow/day for SBS, CS, and HMC, respectively), live weight, and fat concentration were not modified by treatments, but milk protein concentration was lower for SBS compared with HMC (p < 0.05) and similar to CS. B-hydroxybutyrate, cholesterol, and albumin were not different among treatments (p > 0.05), while urea was higher in SBS, medium in CS silage, and lower in HMC (p < 0.001). Ruminal pH and the total VFA concentrations were not modified by treatments (p > 0.05), which averaged 6.45 and 102.03 mmol/L, respectively. However, an interaction was observed for total VFA concentration between treatment and sampling time (p < 0.05), showing that HMC produced more VFA at 10:00 p.m. compared with the other treatments. To conclude, the supplementation with sugar beet silage allowed a milk response and composition similar to corn silage and HMC, but with a lower concentration of milk protein than HMC. In addition, sugar beet silage can be used as an alternative supplement for high-producing dairy cows with restricted access to grazing during spring.

Associative Effects between Forages and Concentrates on In Vitro Fermentation of Working Equine Diets.

BACKGROUND: Horses are hindgut fermenters, and it is therefore important to determine the postgastric nutritive value of their feedstuffs and diets. Moreover, it has been demonstrated in other animal species that the fermentation of diets results in different values than those expected from pure ingredients. Therefore, the general objective of this work is to evaluate the gas production (GP) and volatile fatty acid (VFA) concentration, as well as the associative effects, of mixtures of different forages and concentrated foods, which are representative of the traditional diets of high-performance horses. METHODS: An in vitro gas production experiment was conducted to assess the fermentation of two forages and three concentrates that are typical in horse diets. The combination of 70% of forage and 30% concentrates was also assessed to determine potential associative effects. RESULTS: Concentrates and grains produced higher GP and VFA than forages when evaluated alone. When experimental diets were incubated, GP parameters and VFA concentrations of forage-concentrate mixtures had unexpected differences from the values expected from the fermentation of pure ingredients, suggesting the occurrence of associative effects. CONCLUSIONS: Our results indicate that there is a need to evaluate the fermentation of diets, rather than predicting from the values of pure ingredients.

Chemical Composition, Fatty Acid Profile and Sensory Characteristics of Chanco-Style Cheese from Early Lactation Dairy Cows Fed Winter Brassica Crops.

Brassica crops such as kale and swede can be supplied to cow diets during winter, however little is known about the effects of feeding those forage brassicas to lactating cows on cheese nutritional characteristics of milk and cheese. This study evaluated the effect of including kale or swede in pasture-fed lactating dairy cow diets on chemical composition, fatty acid (FA) profile, and sensory characteristics of Chanco-style cheese. Twelve early-lactation cows were used in a replicated (n = 4) 3 × 3 square Latin square design. The control diet consisted of (DM basis) 10.0 kg of grass silage, 4.0 kg of fresh grass pasture, 1.5 kg soybean meal, 1.0 kg of canola meal, and 4.0 kg of cereal-based concentrate. The other treatments replaced 25% of the diet with swede or kale. Milk yield, milkfat, and milk protein were similar between treatments as were cheese moisture, fat, and protein. Swede and kale increased total saturated cheese FA while thrombogenic index was greater in swede, but color homogeneity and salty flavor were greater while ripe cheese aroma less than for kale. Kale or swede can be used in the diet of pasture-fed lactating dairy cows without negative effects on milk production, milk composition, or cheese composition. However, kale and swede increased total cheese saturated FA.

Effect of Two Nutritional Strategies to Balance Energy and Protein Supply in Fattening Heifers on Performance, Ruminal Metabolism, and Carcass Characteristics.

Latin America is an important contributor to the worldwide beef business, but in general, there are limited studies considering strategies to reduce nitrogen contamination in their production systems. The study's goal was to assess the effect of two nutritional strategies to balance energy and protein supply in fattening heifers on performance, ruminal metabolism, and carcass characteristics. A total of 24 crossbred heifers (initial body weight 'BW 'of 372 ± 36 kg) were used to create two blocks (based on live weight) of two pens each, that were equipped with individual feeders. Within each block, half of the animals were assigned to a diet based on tabular Crude Protein (CP) requirements denominated Crude Protein Diet 'CPD' but without a ruminal degradable protein balance. The other half received a diet denominated Metabolizable Protein Diet 'MPD', formulated with the metabolizable protein system, balanced for the ruminal degradable protein. Both diets had the same ingredients and as well as similar synchrony indexes (0.80 and 0.83, respectively). For nitrogen concentration in feces and urine as well as microbial crude protein synthesis, a total of 12 heifers (three per pen) were randomly selected to collect samples. The dataset was analyzed as a randomized complete block design with a 5% significance. No diet × time interaction was observed for Average Daily Gain 'ADG' (p = 0.89), but there was an effect of the time on ADG (p ≤ 0.001). No differences were observed neither for final weight, dry matter intake 'DMI', and feed conversion rate (p > 0.05). Heifers fed with CPD showed greater cold carcass weight (p = 0.041), but without differences in ribeye area, backfat thickness, pH, dressing %, and marbling (p > 0.05). Differences between diets were observed for the in vitro parameters as well as for the Total Volatile Fatty Acids 'VFA' and NH3 (p < 0.05). Total N concentrations (urine + feces) of heifers fed with MDP was lower than in those fed with the CPD (p < 0.01), but no differences were observed in microbial protein, purine derivatives, and creatinine (p > 0.05). We conclude that the combination of synchrony and the metabolizable protein system achieve greater efficiency in the use of nitrogen, without negatively affecting animals' performance or the quality of the carcass.

In Vitro Fermentation Patterns and Methane Output of Perennial Ryegrass Differing in Water-Soluble Carbohydrate and Nitrogen Concentrations.

The objective of this study was to determine the effect of perennial ryegrass (PRG) forages differing in their concentration of water-soluble carbohydrates (WSC) and crude protein (CP), and collected in spring and autumn, on in vitro rumen fermentation variables, nitrogen (N) metabolism indicators and methane (CH4) output, using a batch culture system. Two contrasting PRG pastures, sampled both in autumn and spring, were used: high (HS) and low (LS) sugar pastures with WSC concentrations of 322 and 343 g/kg for HS (autumn and spring), and 224 and 293 g/kg for LS in autumn and spring, respectively. Duplicates were incubated for 24 h with rumen inocula in three different days (blocks). Headspace gas pressure was measured at 2, 3, 4, 5, 6, 8, 10, 12, 18, and 24 h, and CH4 concentration was determined. The supernatants were analysed for individual volatile fatty acids (VFA) concentrations, and NH3-N. The solid residue was analysed for total N and neutral detergent insoluble N. Another set of duplicates was incubated for 4 h for VFA and NH3-N determination. The HS produced more gas (218 vs. 204 mL/g OM), tended to increase total VFA production (52.0 mM vs. 49.5 mM at 24 h), reduced the acetate:propionate ratio (2.52 vs. 3.20 at 4 h and 2.85 vs. 3.19 at 24 h) and CH4 production relative to total gas production (15.6 vs. 16.8 mL/100 mL) and, improved N use efficiency (22.1 vs. 20.9). The contrasting chemical composition modified in vitro rumen fermentation tending to increase total VFA production, reduce the acetate:propionate ratio and CH4 concentration, and improve N use efficiency through lower rumen NH3-N.

Pre-Grazing Herbage Mass Affects Grazing Behavior, Herbage Disappearance, and the Residual Nutritive Value of a Pasture during the First Grazing Session.

During the first hours after the allocation of a grazing strip (first grazing session, GS), dairy cows eat most of the daily dry matter (DM) available. There are few studies that analyze how the grazing-down process changes the characteristics of the pasture during the first GS. The objective of this study was to evaluate the effect of two pre-grazing herbage masses (HM; medium herbage mass (MHM) and high herbage mass (HHM) on the DM disappearance, grazing behavior of dairy cows, and the residual nutritive value of a pasture during the first GS. Two groups of twelve dairy cows were used to evaluate the grazing-down process, during a period of 62 days. The pre-grazing HM modified the bite rate, bite mass, and dry matter intake during the first GS. The pre-grazing HM affected the process of herbage disappearance of the pasture, especially during the first 60 min of the GS. The nutrient selection differential for acid detergent fiber was greater for HHM compared with MHM (0.93 vs. 0.86). In conclusion, pre-grazing HM affects the structural characteristics and the residual nutritive value of the pasture. The grazing process in the first GS was modified by the HM, affecting the defoliation and the DM disappearance rate of the pasture.

Acceptability, Preferences, and Palatability of Diets Containing Summer and Winter Brassica Forage in Growing Pigs: A Pilot Study.

Brassica forage may be included in pigs' diet as a dietary fiber ingredient to reduce feeding costs, benefit gut health, immune system, reproductive traits, and welfare. However, they contain antinutritional factors which may affect feeding behavior. This study evaluated feeding behavior of growing pigs offered winter (kale and swede) and summer (turnip and forage rape) brassicas incorporated on their diets as dried ground meal. Two consecutive experiments with six growing castrated male pigs were conducted. Experiment 1 evaluated the inclusion of turnip bulbs and forage rape, while experiment 2 studied inclusion of kale and swede bulbs. Brassica meal was included at 15% of the diet by replacing wheat middlings (control diet). In each experiment, pigs were offered experimental diets over six consecutive days for 10 min to test their acceptability (day 1-3) and preferences (day 4-6). No differences were found between diets that included brassicas and control diet in pigs' acceptability or palatability (p > 0.05). However, during preference tests of winter brassicas, swede presented a higher consumption than control and kale (p < 0.05). This suggest that brassicas may be incorporated in growing pigs' diets without negative effects in animals' oral perception during short term feeding tests. Nevertheless, the long-term effects need to be explored.

Consumer preferences and sensory characteristics of eggs from family farms.

The objective of this study was to evaluate consumer habits as well as the sensory perception and characteristics of farm eggs produced in Los Ríos, Chile. Data were collected from an online survey of 197 respondents and a sensory evaluation carried out by 30 untrained panelists of 4 types of eggs (brown-shell and blue-shell eggs acquired from family farms, free-range eggs acquired from large, industrial systems, and white-shell cage eggs from industrial, cage systems.) To evaluate differences and preferences, data were analyzed in a GLM. In addition, sensory evaluation was analyzed using principal component analysis. In accordance with the survey, 99% of the participants eat eggs (P < 0.001), 58% eat 1 to 3 eggs/wk, and 84% declared to consume eggs at home (<0.0001). Surveyed participants reported that price and size are the determining factors (31%) when purchasing eggs. Among the physical characteristic for consumers, yolk color was the most important attribute rather than white color, egg appearance, texture, flavor, or odor. In the consumer acceptability test, farm eggs (either brown or blue shell) received the most favorable sensory evaluation by the panel and were preferred to both free-range and white-shell cage eggs. Yolk color was the most influential parameter in making this difference. Brown farm eggs were predominately selected for greatest general satisfaction by participants in both the sensory evaluation (P = 0.008) and in the survey (40%; P = 0.026). There were no differences between farm eggs (brown and blue shell, P > 0.05) in the evaluated parameters. There was a consequence in the information given from surveyed consumers and the sensory panel with the yolk color.

Rumen In Vitro Fermentation and In Situ Degradation Kinetics of Winter Forage Brassicas Crops.

The aim of the present study was to evaluate the nutritional value, the rumen in vitro fermentation, and the in situ degradation of Brassica oleracea (L.) ssp. acephala (kales) and Brassica napus (L.) ssp. napobrassica (swedes) for winter use. Five varieties of each brassica were used in three field replicates and were randomized in a complete block nested design. All forage varieties were harvested at 210 days post-sowing to analyze the chemical composition, in vitro gas production, volatile fatty acid (VFA) production and in situ dry matter (DM) and crude protein (CP) degradability. Kales presented higher DM and neutral detergent fiber (NDF) content (p < 0.01), whereas swedes showed higher CP, metabolizable energy (ME), glucose, fructose, total sugars, NFC, and nonstructural carbohydrate (NSC) content (p < 0.01). The kale and swede varieties differed in their CP and sugar concentrations, whereas the kale varieties differed in their DM and raffinose content. The rates of gas production were higher for swedes than for kales (p < 0.01). No differences between the brassica species (p > 0.05) were observed in the total VFA production, whereas kales had a higher proportion of acetate and swedes had higher proportions of butyrate (p < 0.05). Only the swede varieties showed differences in VFA production (p < 0.05). The soluble fraction "a", potential and effective in situ DM degradability were higher in swedes (p < 0.01), but kales presented greater DM and CP degradation rates. Differences were observed between brassica species in the chemical composition, degradation kinetics, and ruminal fermentation products, whereas differences among varieties within species were less frequent but need to be considered.

Characterization of Feeding, Sport Management, and Routine Care of the Chilean Corralero Horse during Rodeo Season.

The aim of this study was to characterize the routine care, training, feeding, and nutritional management of Chilean corralero horses that participated in the rodeos of the Chilean Rodeo Federation. Forty-nine horse farms between the Metropolitan (33°26'16″ south (S) 70°39'01″ west (W)) and Los Lagos Regions (41°28'18″ S 72°56'12″ W), were visited and a survey was conducted on the management and feeding of the Chilean horse. Of the horses which participated in at least one official rodeo in the 2014-2015 season, 275 horses were included in the study. The survey consisted of five questions about general data on the property and the respondent, four questions on the animal characteristics, five questions about where the horses were kept during the day, seven questions to characterize the amount of exercise done by the horse, and 18 questions about feeding practices; additionally, the amount of feed offered was weighed. All horses in this study were in training and kept in their stall for at least 12 h and remained tied or loose for the rest of the day. The intensity of daily exercise of the rodeo Chilean horse could be classified as moderate to heavy and consisted of being worked six days/week and participating in two rodeos/month. Ninety-eight percent of respondents had watering devices in the stables. The diet of the Chilean corralero horse during the training season is based on forages, mainly alfalfa hay, plus oats as an additional energy source. Protein supplements such as oil seed by-products are used less frequently. A wide variation was observed in the diets and quantities of feed offered, which suggests that the feeding management of these individuals is not formulated according to their requirements.

Evaluation of sources of variation on in vitro fermentation kinetics of feedstuffs in a gas production system.

The aim of this study was to evaluate the effect of different sources of variation in gas production technique on the in vitro gas production kinetics of feedstuffs. Triplicates of commercial concentrate, grass silage, grass hay and grass pasture were incubated in three experiments: experiment 1 assessed two agitation methods; experiment 2 evaluated different rumen inocula (pooled or different donor cows for each incubation run); and experiment 3 used Goering-Van Soest or Mould buffers for media preparation. Gas production data were fitted into the Michaelis-Menten model and then subjected to analysis of variance. Gas production (GP) at 48 h and asymptote gas production (A) were lower when bottles were continuously under horizontal movement. Time to produce half and 75% of A, and A were affected by rumen inocula, while buffer type affected time to produce half and 25% of A and GP. No interactions between substrates and sources of variation were observed, suggesting that the effects of substrates on GP parameters were not modified. It is concluded that comparison of numerical data from in vitro experiments that follow different protocols must be done carefully. However, the ranking of different substrates is more robust and less affected by the sources of variation.

¿Son los ácidos grasos de la carne y la leche bovina nocivos para la salud de las personas? / Are fatty acids from beef and milk from cattle harmful for human health?

Nutritional recommendations of the past 35-40 years have promoted the reduction of fat intake, calories and particularly saturated fatty acids (SFA), emphasizing lower consumption of red meat and high fat dairy products, because of its association with cardiovascular diseases (CVD), being in turn replaced by sugars and refined carbohydrates. There is consensus that the SFA concentration in blood plasma, particularly palmitic acid, are associated with an increased risk of CVD and heart attacks. However, there is no evidence of causality between CVD and consumption of SFA, raising reasonable doubts about the relation ship between consumption of SFA with those present in blood plasma, as well as with the CVD risk. This review presents scientific evidence that demonstrates that the inclusion of fats in the diet, specifically animal fats from ruminants, provide important health benefits for people, especially when accompanied by a reduction in the consumption of carbohydrates. It is also proposed that ruminant products and their fatty acids contribute with beneficial saturated fats for people's health, especially those from pastoral production systems such as vaccenic, rumenic and linolenic acids.

Las recomendaciones nutricionales de los últimos 40 años han promovido la reducción del consumo grasas, calorías y particularmente ácidos grasos saturados (AGS), enfatizando un menor consumo de carnes rojas y productos lácteos altos en materia grasa debido a su asociación con enfermedades cardiovasculares (ECV), siendo reemplazados por azúcares y carbohidratos refinados. Existe consenso en que la concentración de AGS en el plasma sanguíneo, particularmente ácido palmítico, se asocia con un mayor riesgo de ECV y ataques al corazón. Sin embargo, no hay evidencias de causalidad entre ECV y consumo de AGS, planteando dudas razonables sobre la existencia de una relación entre el consumo de AGS con los presentes en el plasma sanguíneo, y con el riesgo de ECV. La presente revisión plantea evidencia científica que demuestra que la incorporación de grasas en la dieta, específicamente grasas de origen animal, aporta importantes beneficios para la salud de las personas, en especial cuando se acompaña de una reducción en el consumo de carbohidratos. Asimismo, se plantea que los productos de rumiantes y sus grasas contribuyen con ácidos grasos beneficiosos para la salud de las personas, en especial aquellos provenientes de sistemas de producción pastoriles como los ácidos vaccénico, ruménico y linolénico.