Changes in fatty acid composition of milk from lactating dairy cows during transition to and from pasture

Five Holstein cows producing an average of 25.4 ± 6.4 kg/d and 347 ± 111 days in milk were used to study the changes in fatty acid composition in milk from lactating dairy cows during transition to and from pasture. The 45-d experiment was divided into 3 periods. During the first 2 d of the experiment (Period I), cows were fed a TMR diet containing 50% conserved forage and 50% grain. On day 3, cows were turned out to pasture and remained on all-pasture diet for 29 d (Period II). On day 32, cows were withdrawn from pasture and offered a TMR diet until day 45 (Period III). Milk yield was recorded daily, and milk fat content and fatty acid (FA) composition were determined daily for composite samples collected from a.m. and p.m. milkings. Data were analyzed using spline regression (H₀ = zero slope) to determine whether there was any change in the concentration of a particular fatty acid after a specific time or whether it had stabilized. Cows produced an average of 25.2 ± 5.5, 13.7 ± 5.6, and 12.1 ± 4.8 kg/d of milk with 3.6, 4.2, and 3.6% fat during pre-pasture, pasture, and post-pasture diets, respectively. The conjugated linoleic acid (CLA) content was 0.45% of total fat during pre-pasture, reached to a maximum of 2.53% on day 23 into pasture and plateaued thereafter for the period. Milk fat C_18:1 t-11 content was 2.89% of total fat during pre-pasture, reached a maximum of 7.95% after day 22 in pasture, and plateaued afterwards. The C_18:2 content declined gradually from pre-pasture to pasture diet with no further decrease observed after day 22, while C_18:3 content increased until day 7 on pasture. The post-pasture CLA content in milk fat reached a value similar to pre-pasture within 4 days after the cows were withdrawn from pasture. No change in other fatty acids was observed after day 7 once the cows were switched to post-pasture diet. In the present study, it took 23 days to establish the highest level of CLA in milk fat after turning cows out to pasture, whereas only 4 days were needed to bring it back to the original level once the cows were withdrawn from pasture. Other milk fatty acids were stabilized around day 23 after turning cows out to pasture and by day 7 after being withdrawn from pasture and put back on a TMR diet inside the barn.     

Effects of induced subacute ruminal acidosis on milk fat content and milk fatty acid profile

Two lactating dairy cows fitted with a rumen cannula received successively diets containing 0%, 20%, 34% and again 0% of wheat on a dry matter basis. After 5, 10 and 11 days, ruminal pH was measured between 8:00 and 16:00 hours, and milk was analysed for fat content and fatty acid profile. Diets with 20% and 34% wheat induced a marginal and a severe subacute ruminal acidosis respectively. After 11 days, diets with wheat strongly reduced the milk yield and milk fat content, increased the proportions of C8:0 to C13:0 even- or odd-chain fatty acids, C18:2 n-6 and C18:3 n-3 fatty acids but decreased the proportions of C18:0 and cis-9 C18:1 fatty acids. Wheat also increased the proportions of trans-5 to trans-10 C18:1, the latter exhibiting a 10-fold increase with 34% of wheat compared with value during the initial 0% wheat period. There was also an increase of trans-10, cis-12 C18:2 fatty acid and a decrease of trans-11 to trans-16 C18:1 fatty acids. The evolution during adaptation or after return to a 0% wheat diet was rapid for pH but much slower for the fatty acid profile. The mean ruminal pH was closely related to milk fat content, the proportion of odd-chain fatty acids (linear relationship) and the ratio of trans-10 C18:1/trans-11 C18:1 (nonlinear relationship). Such changes in fatty acid profile suggested a possible use for non-invasive diagnosis of subacute ruminal acidosis.     

Concentrations of retinol and tocopherols in the milk of cows supplemented with conjugated linoleic acid

This study was performed to investigate the hypothesis that supplementation of conjugated linoleic acid (CLA) changes the concentrations of retinol and tocopherols in the milk of cows. To investigate this hypothesis, Holstein cows received daily from 3 weeks ante‐partum to 14 weeks post‐partum either 172 g of a CLA‐free rumen‐protected control fat (control group, n = 20) or the same amount of a rumen‐protected CLA fat, supplying 4.3 g of cis‐9, trans‐11 CLA and 3.8 g of trans‐10, cis‐12 CLA per d (CLA group, n = 20). Milk samples (collected at weeks 1, 3, 5, 8 and 11 of lactation) were analysed for retinol, α‐ and γ‐tocopherol concentrations. Milk of cows supplemented with CLA had higher concentrations of retinol (+34%), α‐tocopherol (+44%) and γ‐tocopherol (+21%) than milk of control cows (p < 0.05). The daily output of these vitamins via milk was also greater in cows of the CLA group than in cows of the control group (+36, 50 and 24% for retinol, α‐tocopherol and γ‐tocopherol, respectively, p < 0.05). In agreement with higher concentrations of tocopherols, concentrations of thiobarbituric acid‐reactive substances, determined in milk of week 5, were lower in cows of the CLA group than in control cows, indicative of a lower susceptibility of milk lipids to peroxidation. Plasma concentrations of retinol and α‐tocopherol, determined at 1 and 5 weeks post‐partum, were not different between the two groups of cows. In conclusion, this study shows that supplementing dairy cows with a moderate amount of CLA causes an increase of the concentrations of vitamins A and E in the milk and results in an increased output of those vitamins via milk. These effects might be beneficial with respect to the nutritional value of dairy products and the susceptibility of milk fat to oxidative deterioration.     

Influence of pasture on fatty acid profile of goat milk

The effect of pasture on the fatty acid profile of milk was evaluated using 30 pluriparous goats, which were divided into two homogeneous groups (H and P) of 15 goats each after kidding. Group H (control) goats were housed in a stall and received alfalfa hay, while group P was led to pasture. The goats of both the groups received the same concentrate. Average milk yield did not differ statistically between the groups. The goats of the P group had significantly higher fat content in milk than those of group H (53.7 vs. 61.5 g/day, p < 0.01), while lactose content was significantly higher for group H (66.2 and 61.4 g/day, for groups H and P, respectively, p < 0.05). Among milk fatty acids, pasture significantly affected the percentages of C18:1 cis9, C18:1 trans11, octadecadienoic acid, mono-unsaturated fatty acid and polyunsaturated fatty acid. Pasture highly influenced the c9 t11 conjugated linoleic acid (CLA) (0.778 and 0.513 g/100 g of fat, for group P and H, respectively, p < 0.01), t10 c12 CLA (0.046 vs. 0.029 g/100 g of fat: p < 0.01, for group P and H, respectively, p < 0.01) and SigmaCLA (0.84 vs. 0.56 g/100 g of fat for group P and H, respectively, p < 0.01) concentrations of milk.     

不同胎次和产奶量的奶牛鲜奶脂肪酸含量比较

用气相色谱测定了不同胎次及不同产奶量奶牛鲜奶的脂肪酸含量。一胎４２个、二胎４８个、三胎２０个鲜奶样品。２０００～３０００千克１５个、３００１～４０００千克４１个、４００１～５０００千克３５个、５００１～６０００千克７个鲜奶样品。结果发现，１８：１脂肪酸含量为３３．４８％～３４．８６％；１８：２为８．５１％～１０．０８％；１４：０为７．９４％～１０．１４％；１６：０为２４．０４％～２６．２４％；１８     

亚急性瘤胃酸中毒耐受性不同的奶牛血浆和乳中脂肪酸及代谢物组成分析

The present study aimed to explore the differences in plasma and milk metabolism of dairy cows with different subacute rumen acidosis (SARA) tolerance. Twelve fistulated Holstein dairy cows in mid lactation[days in milk=(114±22) d] were selected and fed the same diet consisting of 60% forage and 40% concentrate mixture. On days 20 and 21 of the trial period, the rumen pH was monitored at 0, 2, 4, 6, 8, and 12 h after morning feeding. Milk samples were collected before feeding in the morning and evening. Blood samples were collected from the jugular vein 6 h after morning feeding. All the milk and blood samples were stored in liquid nitrogen for subsequent fatty acid composition and metabolome analysis. Cows with the lowest and highest ruminal pH were assigned into the susceptible (SUS, n=4) and tolerant (TOL, n=4) groups, respectively. The fatty acid composition results showed that the proportions of ≤C16 fatty acids in the blood and milk were significantly increased in the SUS group (P< 0.05), while the proportions of > C16 fatty acids were significantly decreased (P< 0.05). The levels of the saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) in the milk were significantly decreased in the SUS group (P< 0.05). The LC-MS metabolomics results revealed that the L-phenylpyruvate was significantly reduced, while the levels of remaining MG (18: 0/0: 0/0: 0), 9-HODE, niacinamide, isovalerylcarnitine, phosphocreatine, L-glutamic acid, and 12(13) Ep-9-KODE were substantially increased in the SUS group. The results of milk metabolome analysis indicated that the levels of 1-stearoylphosphoglycerolserine and sphingosine were significantly increased, while the levels of 14 different metabolites were significantly decreased in the SUS group (P< 0.05), including glyceryl-phosphoryl-ethanolamine, glycerol 3-phosphate, and orotic acid. These differential metabolites were mainly involved in glycerophospholipid metabolism (P< 0.05), glycerolipid metabolism, and pantothenate and CoA biosynthesis. In conclusion, the fatty acids and metabolic profiles in the plasma and milk of cows with different tolerance to SARA were different. For the SUS group, the amino acid metabolism and the de novo synthesis ability of milk fat was enhanced in the plasma, while the ability to absorb long chain fatty acids from blood was weakened. At the same time, the levels of phospholipid, orotic acid and other nutrients were decreased in the milk, which indicated that the quality of milk was reduced for the SUS cows. © 2021, Editorial Office of Acta Prataculturae Sinica. All rights reserved.     

Effect of dietary fish oil on milk yield, fatty acids content and serum metabolic profile in dairy cows

The aim of the study was to evaluate the effects of dietary unprotected fish oil on milk yield, fatty acids content and serum metabolic profile in dairy cows. Forty lactating Polish Holstein-Friesian cows were assigned to two groups. The cows were fed a control basal diet (C group), or a basal diet containing 2% addition of fish oil on mineral carrier (FOM group) during a 8-week period. Supplementing FOM diet of dairy cows had no significant effect on milk fat, milk protein, milk lactose concentration and somatic cells count, but increased the milk yield (36.5 kg/d), (p < 0.05) compared with the control cows (34.28 kg/d). We observed an increase (p < 0.05) in body condition scoring between C and FOM groups. Additionally, higher levels of non-esterified fatty acids and β-hydroxybutyrate acid were noticed in FOM group after 8 weeks of the experiment; however, these serum parameters still were in the reference range. Concentration of insulin was higher (30.40 μU/ml; p < 0.01) in the FOM group compared with the control group (14.03 μU/ml). In the FOM group, significant increase (p < 0.01) in long-chain fatty acids, mainly cis-9, trans-11 CLA and n-3 fatty acids (eicosapentaenoic and docosahexaenoic acids) was observed. The obtained results demonstrated that addition of fish oil to cows' diet could profitably modify the fatty acids in cow's milk.     

Effects of different forage combinations in total mixed rations on in vitro gas production kinetics,ruminal and milk fatty acid profiles of lactating cows

This study aimed to determine the effects of different forage combinations on in vitro gas production (GP) kinetics, ruminal and milk fatty acid profiles. Forty‐five lactating cows were randomly arranged into three groups and fed three total mixed rations (TMRs) with different forage combinations: TMR1, 23% alfalfa hay, 7% Chinese wild ryegrass hay and 15% whole corn silage; TMR2, 30% corn stover plus 15% whole corn silage; TMR3, 30% rice straw plus 15% whole corn silage. In vitro dry matter disappearance ranked: TMR1 > TMR2 > TMR3, and highest cumulative GP and asymptotic GP occurred in TMR1 while no difference occurred between TMR2 and TMR3. The average GP rate ranked: TMR1 > TMR2 > TMR3. TMR1 in comparison with TMR2 and TMR3 presented lower rumen contents of acetate and butyrate and greater rumen contents of propionate, valerate, C13:0, C14:0, C15:0, C18:1cis‐9, C18:2n‐6, C18:3n‐3, C20:0 and C22:0 as well as milk C18:2n‐6 and C18:3n‐3 proportions. Transfer efficiencies of C18:2n‐6 and C18:3n‐3 from diet to milk ranked: TMR1 > TMR2 > TMR3. The findings suggest TMRs containing alfalfa hay and Chinese wild ryegrass hay in comparison with corn stover or rice straw improve rumen fermentation and transfer efficiency of C18:2n‐6 and C18:3n‐3.     

Mineral and fatty acid composition of milk from native Jutland and Danish Red 1970 cattle breeds

ABSTRACT

Mineral and fatty acid composition in milk from two minor native dairy breeds in Denmark; Danish Red 1970 (RDM-1970) and Jutland cows were analyzed. Results showed that for most compositional traits breed only played a minor role, whereas management and feeding played a significant role. Biodynamic management and very low milk yield resulted in a very characteristic fatty acid composition and a strongly elevated n-3/n-6 ratio (ratio 0.9 compared to 0.3). For milk minerals, RDM-1970 had significantly higher contents of P, Mg, Mn, whereas milk from Jutland cows had significantly higher K content.     

Decrease in stearic acid proportions in adipose tissues and liver lipids in fatty liver of dairy cows

Samples of liver and perirenal, mesenteric and subcutaneous fat were collected from 16 sick necropsied dairy cows to evaluate the fatty acid profiles in the hepatic and adipose tissues associated with advanced fatty liver or hepatic lipidosis. Hepatic triglyceride and eight fatty acids were measured in the hepatic and adipose tissues. Six cows had more than 3% triglyceride on fresh weight in their livers and were classified as having fatty liver. Stearic and linoleic acid proportions in the liver decreased markedly with increased hepatic triglyceride levels, while the proportion of palmitic and oleic acids increased. The most striking fluctuations in hepatic lipidosis were manifested as decreased stearic acid in the adipose tissues including subcutaneous fat with the trend of decreasing stearic acid. Palmitic acid was elevated in hepatic and perirenal fat in fatty liver cows. In instances of advanced hepatic lipidosis, palmitoleic acid increased in only subcutaneous fat and not in perirenal or mesenteric fat. In addition to the proportions of hepatic fatty acids in fatty liver, this study also clarified the fluctuations observed in the profiles of fatty acids of the adipose tissues in cows with advanced hepatic lipidosis, particularly the decline in the proportions of stearic acid.     

Effects of pistachio by‐products on digestibility,milk production,milk fatty acid profile and blood metabolites in Saanen dairy goats

The objective of this study was to investigate the effects of pistachio by‐products (PBP) on nutrient digestibility, blood metabolites and milk fatty acid (FA) profile in Saanen dairy goats. Nine multiparous lactating Saanen goats (on day 90 post‐partum, 45 ± 2/kg BW) were randomly assigned to a 3 × 3 Latin square design with three treatment diets: 1) control diet (alfalfa hay based), 2) 32% PBP and 3) 32% PBP + polyethylene glycol (PEG‐4000; 1 g/kg dry matter). Each period lasted 21 days, including 14 day for treatment adaptation and 7 day for data collection. Pistachio by‐products significantly decreased (p < 0.01) crude protein (CP) digestibility compared with the control diet (64.4% vs. 58.7%), but PEG addition did not differ for CP digestibility of goats fed 32% PBP + PEG and those fed the two other diets. The digestibility of NDF tended (p = 0.06) to decrease for goats fed PBP compared with those fed the control diet. Yields of milk and 4% fat‐corrected milk were not affected by dietary treatments. Compared with the control diet, PBP supplementation appreciably changed the proportions of almost all the milk FA measured; the main effects were decreases (p < 0.01) in FA from 8:0 to 16:0 and increases (p < 0.01) proportions of cis‐9, trans‐11 18:2 and trans‐11 18:1, monounsaturated FA, polyunsaturated FA and long‐chain FA. The saturated FA, short‐chain FA and medium‐chain FA proportions were lower (p < 0.01) in goats fed the two PBP supplemented diet than in those fed the control diet and PEG addition led to intermediate proportions of saturated FA, unsaturated and monounsaturated FA. Inclusion of PBP in the diet decreased (p < 0.01) plasma concentrations of glucose and urea nitrogen compared with the control diet. It was concluded that PBP can be used as forage in the diet of dairy goats without interfering with milk yield. Inclusion of 32% PBP in the diet of dairy goats had beneficial effects on milk FA profile but PEG addition to PBP did not contribute to enhance further milk FA profile.     

Growth performance,carcass characteristics,fatty acid composition and CLA concentrations of lambs fed diets supplemented with different oil sources

Quality food for human consumption will always be the aim for animal producers. Quantity and composition of fat deposits (fatty acid profile) strongly influences meat quality in ruminants, especially via increasing conjugated linoleic acid (CLA) concentration, which is known to have beneficial anticarcinogenic, antiatherogenic, antidiabetic and cholesterol reduction properties for human health. Awassi lambs are one of the main and most consumed meat sources in the Middle East area; however, studies addressing the fat content of CLA and methods to enhance its concentrations in this breed are still rare. For this reason, the aim of this study was to evaluate the effect of adding two different oil sources (soybean oil (SBO) and sunflower oil (SFO) at two levels (1.8 and 3%)) on growth performance, carcass characteristics and fatty acid profile of fat in Awassi lambs. Oil supplementation had no effect on growth performance or carcass characteristics, while fatty acid composition changed according to the site of extraction. CLA concentrations were increased in the tail fat deposit, with 1.8% SBO and in intermuscular fat deposit with 3% SFO. Intermuscular fat is the one most naturally consumed by humans, serving to improve food quality.     

Effect of linseed oil supplementation on performance and milk fatty acid composition in dairy cows

Thirty‐six Holstein‐Friesian crossbred lactating dairy cows were used to determine the effects of linseed oil supplementation on performance and milk fatty acid (FA) profile. Three treatments were as follows: basal diet (56:44 Roughage:concentrate [R:C] ratio, dry matter basis) supplemented with 500 g of palm oil as control (PO), 500 g mixture (1:1, w/w) of palm oil and linseed oil (POLSO) and 500 g of linseed oil (LSO). The LSO supplementation had no effects on total dry matter intake (DMI), milk yield and milk composition. Compared to control cows, cows supplemented with LSO increased milk concentrations of cis‐9,trans‐11 conjugated linoleic acid (CLA) and n‐3 FA (P < 0.05), particularly C18:3n‐3, C20:5n‐3 and C22:6n‐3. Feeding LSO reduced concentrations of milk short‐ and medium‐chain saturated fatty acids (P < 0.05) while it increased concentration of milk unsaturated fatty acids (P < 0.05). Milk proportions of n‐3 FA increased, whereas n‐6/n‐3 ratio decreased in the LSO as compared with the control (P < 0.05). In conclusion, supplementing dairy cows' diet based on corn silage with LSO at 500 g/day could improve the nutritional value of milk with potential health‐beneficial FA without detrimental effect on milk composition or cow's performance.     

蜀宣花牛无角新类群胴体不同部位肌内脂肪酸组成成分分析及结构研究

为明确蜀宣花牛无角新类群胴体不同部位肌内脂肪酸组分和结构情况,选择10头体重为324.79 kg±43.51 kg的7～8月龄健康无角公犊牛作为试验动物开展育肥试验,试验期300 d,屠宰后45 min内采集里脊、外脊、眼肉、上脑、辣椒条、米龙、大黄瓜条、小黄瓜条、臀肉、牛霖、胸肉、腹肉和腱子肉共13个部位的组织样本,...     

日粮中添加整粒油籽对绵羊体脂脂肪酸组成的影响

日粮中分别添加相当于40 g粗脂肪的油菜籽(canola)、油葵籽、红花籽和亚麻籽,饲喂成年母羊35 d后屠宰,用气相色谱技术测定了背最长肌、尾部、背膘和肾脏4个部位脂肪的脂肪酸(FA)组成,结果表明:1)红花籽可显著降低肌肉中的短链、长链饱和脂肪酸及总饱和脂肪酸(SFA)的比例,而增加单不饱和脂肪酸(MUFA)和总不饱和脂肪酸(UFA)的比例,而添加油菜籽对肌肉的FA无显著影响;2)油葵显著降低了尾部短链和中链脂肪酸,提高了多不饱和脂肪酸(PUFA)与SFA的比值(P:S),油菜籽可显著降低尾部短链脂肪酸;3)添加亚麻籽有增加所有组织UFA和P:S值,降低SFA的趋势,但只有背膘脂肪中的PUFA显著增高;4)各类油籽对脂肪组织中的总SFA和MUFA无明显影响,其中肾脏脂肪受影响最小.     

包被共轭亚油酸对山羊瘤胃氢化、肠道及乳脂肪酸的影响

文章旨在评估日粮添加棕榈油酸钙和包被共轭亚油酸对瘤胃氢化和长链脂肪酸从十二指肠到乳转化的影响。试验将12只体重(61.9±8.57)kg处于泌乳期的多胎次萨能奶山羊随机分为2组,每组6个重复,每个重复1只羊。两个试验组分别在基础日粮中补充50g棕榈油酸钙和包被共轭亚油酸,试验共开展42d。结果显示,两个试验组对山羊干物质、有机物、中性洗涤纤维、淀粉摄入量及养分在十二指肠流量和瘤胃表观消化率均无显著影响(P>0.05)。与棕榈油酸钙组相比,包被共轭亚油酸组有降低干物质和中性洗涤纤维消化率的趋势(P=0.08),但处理组对淀粉消化率无显著影响(P>0.05)。山羊饲喂棕榈油酸钙或包被共轭亚油酸日粮后,脂肪酸的十二指肠流量高于脂肪酸摄入量。包被共轭亚油酸增加了C18:2trans-10,cis-12和C18:2cis-9,trans-11的十二指肠流量,导致两种脂肪酸对瘤胃的氢化保护率均达到16%。C18:1cis-9、C18:2cis-9,12、C18:3cis-9,12,15的瘤胃生物氢化不受包被共轭亚油酸处理的影响(P>0.05)。综上所述,与添加棕榈油钙相比,在奶山羊中饲喂不受瘤胃生物氢化包被共轭亚油酸对干物质、有机物、中性洗涤纤维、淀粉摄入量、十二指肠流量及瘤胃表观消化率无显著影响。包被共轭亚油酸增加了十二指肠的流量和C18:2trans-10,cis-12和C18:2cis-9,trans-11的比例,使瘤胃生物氢化保护率达到15%~16%。     

Effect of supplementation of soy sauce oil and Ca salts of fatty acids on rumen fermentation,milk production and conjugated linoleic acid in milk of dairy cows

Eight cows were used to evaluate the effects of supplementation of soy sauce oil (SO) or Ca salts of fatty acids (FA) on rumen fermentation and milk production. The control diet (CO) consisted mainly of hay, corn silage and a concentrate. In the experimental diets, 400 g/day per cow of SO or FA (soybean oil and rapeseed oil) was supplemented to the CO diet. Experimental period for the three treatments was 14 days, and milk samples were taken during the last 2 days and rumen sample was taken on the last day. Dry matter intake was not affected by the treatments. The number of rumen protozoa at 0 h increased by SO and FA diets. Total volatile fatty acids at 2 h after feeding of SO diet was decreased compared to CO. The milk composition yield did not differ among treatments, although the percentages of fat and protein were decreased by SO and FA diets. The proportions of C8–C16 fatty acids in milk fat decreased, and those of C18 increased by SO and FA diets. The proportion of cis‐9, trans‐11 conjugated linoleic acid in milk fat by SO and FA diets increased by 120% and 135%, respectively. In spite of the slight suppression of rumen fermentation by SO diet, negative effects on feed intake and milk production were not detected.     

脂肪酸的吸收与脂肪酸结合蛋白

脂肪酸在动物体内的消化吸收是一个非常复杂的过程,需要通过小肠上皮细胞的消化、吸收和转运。脂肪酸吸收研究方法主要分为体内法和体外法。脂肪酸的吸收主要发生在小肠的前2/3部分,而小肠上皮细胞内含有脂肪酸结合蛋白对脂肪酸的吸收以及脂肪酸在细胞内的转运具有极其重要的作用。文中主要综述了脂肪酸的吸收及脂肪酸结合蛋白的相关功能,着重概括了小肠内表达的I-FABP、L-FABP两种蛋白。     

Pleiotropic effects of the goat prolactin receptor genotype on milk fatty acid composition

In the lactating mammary gland, prolactin (PRL) stimulates the synthesis of lactose as well as fatty acid uptake, lipogenesis, and triacylglycerol synthesis. Associations between bovine PRL receptor (PRLR) genotype and fat yield have been reported, which illustrates the role of PRL in conveying lipids toward the udder as well as in stimulating their local synthesis during lactation. Conversely, and to the best of our knowledge, the effects of PRLR genotype on milk fatty acid content have not been studied so far in any mammalian species. In this study, we sequenced most of the coding region of the caprine PRLR gene in several individuals from the Malagueña and Murciano-Granadina breeds. This approach allowed us to identify 2 long and short mRNA isoforms, produced by alternative splicing, and 4 single-nucleotide polymorphisms (SNPs), namely, c.177T>C, c.1131G>A, c.1201G>A and c.1355C>T. Two of these SNPs are nonsynonymous and involve G401R (c.1201G>A) and T452I (c.1355C>T) amino acid substitutions in the cytoplasmic domain of PRLR, which plays a fundamental role in signal transduction. Performance of an association analysis with milk composition traits in a Murciano-Granadina goat population revealed highly suggestive effects on palmitoleic acid content, whereas suggestive effects were detected for other fatty acids, such as palmitic and linoleic. These results are consistent with the pleiotropic effects of PRL on mammary gland lipid metabolism and milk composition.     

Genetic parameters of milk production traits and fatty acid contents in milk for Holstein cows in parity 1 – 3

The objective of this study was to estimate genetic parameters of milk, fat, and protein yields, fat and protein contents, somatic cell count, and 17 groups and individual milk fatty acid (FA) contents predicted by mid‐infrared spectrometry for first‐, second‐ and third‐parity Holstein cows. Edited data included records collected in the Walloon region of Belgium from 37 768 cows in parity 1, 22 566 cows in parity 2 and 8221 in parity 3. A total of 69 (23 traits for three parities) single‐trait random regression animal test‐day models were run. Approximate genetic correlations among traits were inferred from pairwise regressions among estimated breeding values of cow having observations. Heritability and genetic correlation estimates from this study reflected the origins of FA: de novo synthetized or originating from the diet and the body fat mobilization. Averaged daily heritabilities of FA contents in milk ranged between 0.18 and 0.47. Average daily genetic correlations (averaged across days in milk and parities) among groups and individual FA contents in milk ranged between 0.31 and 0.99. The genetic variability of FAs in combination with the moderate to high heritabilities indicated that FA contents in milk could be changed by genetic selection; however, desirable direction of change in these traits remains unclear and should be defined with respect to all issues of importance related to milk FA.