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Milk fat content and fatty acid (FA) composition have great economic value to the dairy industry as they are directly associated with taste and chemical-physical characteristics of milk and dairy products. In addition, consumers' choices are not only based on the nutritional aspects of food, but also on products known to promote better health. Milk FA composition is also related to the metabolic status and physiological stages of cows and thus can also be used as indicator for other novel traits of interest (e.g., metabolic diseases and methane yield). Genetic selection is a promising alternative to manipulate milk FA composition. In this study, we aimed to (1) estimate time-dependent genetic parameters for 5 milk FA groups (i.e., short-chain, medium-chain, long-chain, saturated, and unsaturated) predicted based on milk mid-infrared spectroscopy, for Canadian Ayrshire and Jersey breeds, and (2) conduct a time-dependent, single-step genome-wide association study to identify genomic regions, candidate genes, and metabolic pathways associated with milk FA. We analyzed 31,709 test-day records of 9,648 Ayrshire cows from 268 herds, and 34,341 records of 11,479 Jersey cows from 883 herds. The genomic database contained a total of 2,330 Ayrshire and 1,019 Jersey animals. The average daily heritability ranged from 0.18 (long-chain FA) to 0.34 (medium-chain FA) in Ayrshire, and from 0.25 (long-chain and unsaturated FA) to 0.52 (medium-chain and saturated FA) in Jersey. Important genomic regions were identified in Bos taurus autosomes BTA3, BTA5, BTA12, BTA13, BTA14, BTA16, BTA18, BTA20, and BTA21. The proportion of the variance explained by 20 adjacent SNP ranged from 0.71% (saturated FA) to 1.11% (long-chain FA) in Ayrshire, and from 0.70% (unsaturated FA) to 3.09% (medium-chain FA) in Jersey cattle. Important candidate genes and pathways were also identified, such as the PTK2 and TRAPPC9 genes, associated with milk fat percentage, and HMGCS , FGF10 , and C6 genes, associated with fertility traits and immune response. Our findings on the genetic parameters and candidate genes contribute to a better understanding of the genetic architecture of milk FA composition in Ayrshire and Jersey dairy cattle. [ABSTRACT FROM AUTHOR]

Estimating single nucleotide polymorphism (SNP) effects over time is essential to identify and validate candidate genes (or quantitative trait loci) associated with time-dependent variation of economically important traits and to better understand the underlying mechanisms of lactation biology. Therefore, in this study, we aimed to estimate time-dependent effects of SNP and identifying candidate genes associated with milk (MY), fat (FY), and protein (PY) yields, and somatic cell score (SCS) in the first 3 lactations of Canadian Ayrshire, Holstein, and Jersey breeds, as well as suggest their potential pattern of phenotypic effect over time. Random regression coefficients for the additive direct genetic effect were estimated for each animal using single-step genomic BLUP, based on 2 random regression models: one considering MY, FY, and PY in the first 3 lactations and the other considering SCS in the first 3 lactations. Thereafter, SNP solutions were obtained for random regression coefficients, which were used to estimate the SNP effects over time (from 5 to 305 d in lactation). The top 1% of SNP that showed a high magnitude of SNP effect in at least 1 d in lactation were selected as relevant SNP for further analyses of candidate genes, and clustered according to the trajectory of their SNP effects over time. The majority of SNP selected for MY, FY, and PY increased the magnitude of their effects over time, for all breeds. In contrast, for SCS, most selected SNP decreased the magnitude of their effects over time, especially for the Holstein and Jersey breeds. In general, we identified a different set of candidate genes for each breed, and similar genes were found across different lactations for the same trait in the same breed. For some of the candidate genes, the suggested pattern of phenotypic effect changed among lactations. Among the lactations, candidate genes (and their suggested phenotypic effect over time) identified for the second and third lactations were more similar to each other than for the first lactation. Well-known candidate genes with major effects on milk production traits presented different suggested patterns of phenotypic effect across breeds, traits, and lactations in which they were identified. The candidate genes identified in this study can be used as target genes in studies of gene expression. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to evaluate the effects of the inclusion of oregano in the diet of dairy cows on the physicochemical quality of raw milk and the sensory attributes of pasteurized milk. Twelve crossbred Holstein×Zebu cows were divided into three 4×4 Latin squares, and increasing amounts of oregano were added to their diet. Physicochemical analysis of density, cryoscopic index, protein, fat, lactose, total solids extract (TSE), and dry nonfat extracts (DNE) was performed for the raw milk samples. The microbiological quality of pasteurized milk samples was evaluated by performing total and fecal coliform tests. Adding oregano to the diet showed no influence (P>0.05) on the fat, TSE, protein, and cryoscopic index, with mean values of 3.78g/100g, 12.60g/100g, 3.24g/100g, and g −0535 °H, respectively. However, the levels of lactose, DNE, and density were influenced by the amount of oregano (OV) and ranged from 4.82g/100g to 4.64g/100g, 9.22g/100g to 8.88g/100g, and 1.033g/mL to 1.032g/mL, respectively. Based on microbiological analysis, all samples were considered suitable for consumption (<3.0×105 CFU/mL). The sensory attributes of aroma and flavor did not alter the preference (P>0.05). Only a small difference between treatments was observed in the flavor profile for the warmed-over flavor attribute. For the attributes of a sweet aroma, characteristic milk aroma, characteristic milk flavor, and sweet flavor, the intensity ranges were similar. The results showed no changes (P>0.05) in the main components of milk and, therefore, no effect on its sensory attributes. Thus, it is possible to incorporate dry oregano into cattle feed for the purpose of studying its influence on other parameters of milk composition. [Copyright &y& Elsevier]

• Supplementation with monensin and saponins was evaluated in diets for cows. • The combination of saponins with essential oils increased the energy efficiency. • Nutrients digestibility and nitrogen utilization were not affected by the diets. • Monensin decreased ruminal pH and increased rumen ammonia nitrogen concentration. • The long-chain fatty acids profile in cows' milk was not influenced by the diets. This study aimed to evaluate the effects of diet supplementation with monensin and saponins alone or combined with essential oils (EOs) on the nutrient intake and apparent digestibility, rumen fermentation parameters, microbial population, nitrogen balance, ruminal microbial protein synthesis, blood metabolites, and milk composition, yield and fatty acid profile of mid- to late-lactating Jersey cows. Eight ruminally cannulated lactating Jersey cows (average 17.6 ± 5.5 kg/day of milk yield and 100.5 ± 26.6 days of milk (mean ± SD)) were distributed in a replicated 4 × 4 Latin square design with 21-day periods (last seven days for sampling). Treatment sequences were randomly designated to cows and consisted of: (1) CON - Control, no feed additive; (2) SAP - 16 g/cow/day of a supplement based on whole-seed fenugreek powder (variety Fenucold) standardized to diosgenin, one of the major steroidal sapogenins of fenugreek (2000 mg/kg); (3) SAPEO - SAP supplement combined with a blend of natural EOs with major components of carvacrol (2500 mg/kg), cinnamaldehyde (5600 mg/kg) and limonene (3000 mg/kg); and (4) MON - Monensin, inclusion of monensin sodium in the diet at 24 mg/kg DM. Cows fed CON showed higher dry matter, organic matter, crude protein and ether extract intakes than animals fed MON, whereas higher neutral detergent fibre intake was observed in animals fed SAPEO than those fed MON (P < 0.05). Diet and time effects were observed for ruminal pH and concentration of ruminal ammonia nitrogen (P < 0.05). Cows fed SAP showed a higher relative proportion of Fibrobacter succinogenes (P = 0.04) than animals fed MON. Cows fed CON had higher net and digestible energy intakes than animals fed MON (P < 0.05). Cows fed SAPEO showed higher albumin concentrations (P = 0.04) than those fed CON, SAP, and MON. Besides, cows fed CON showed higher urea concentrations (P = 0.04) than those fed SAP and SAPEO. Higher protein and fat levels in the milk were observed in cows fed SAPEO than animals fed MON (P < 0.05). Monensin decreased the concentrations of C4:0, C6:0, C8:0, and C18:1 cis-11 milk fatty acids (P < 0.05). Monensin decreased nutrient intake to a more energetically efficient pathway but did not alter milk production, digestibility, or rumen fermentation. Saponin supplementation associated with essential oils increases milk fat and protein contents in lactating Jersey cows compared to animals fed a monensin-supplemented diet. [ABSTRACT FROM AUTHOR]