Milk Fat Production Research Articles

Morning and evening pasture access – comparing the effect of production pasture and exercise pasture on milk production and cow behaviour in an automatic milking system

Although pasture is low-cost feed, many farmers find it difficult to maintain high milk yield when using pasture for high-yielding dairy cows in automatically milked herds. Therefore, a seven-week experiment with 40 cows in early to mid-lactation was performed to evaluate a management model for including pasture in the diet without jeopardizing milk production. Within a part-time grazing system with morning and evening outdoor access, we compared a group with ad libitum grass silage indoors combined with access to a small grass-covered permanent paddock for exercise and recreation (group EX) with a group offered production pasture at a high allowance per cow and day combined with restricted grass silage allowance at night (group PROD). Both groups had the same outdoor access times and the same concentrate allowance based on pre-experimental milk yield. Milk yield and milking frequency were recorded daily in the automatic milking unit. Milk recordings and samplings for determination of milk composition took place weekly and outdoor behaviour of cows was recorded during pasture access hours on six observation days, evenly distributed over the experimental period. During the experiment, average metabolisable energy concentration was higher in the grass silage offered both groups than in pasture herbage. However, our results showed no significant difference in daily milk yield between treatments. Furthermore, no significant differences between treatments were found in energy-corrected milk, milk fat production, or body weight change. Milk protein production was, however, significantly higher in group PROD. In early lactation, no difference in milking frequency was observed between treatments while for cows in mid- to late lactation, milking frequency was significantly higher in group EX than group PROD. Over the entire experiment, group EX cows spent significantly less time outdoors than group PROD. In conclusion, offering high yielding dairy cows in automatic milking systems high-quality pasture at a high allowance for a few hours in morning and afternoon appears to be an interesting alternative to exercise paddock with full indoor feeding, as it can reduce costs for supplementary silage, facilitate natural behaviour, and encourage cows to spend more time outdoors, while maintaining milk production at a level comparable to that of full indoor feeding.

Adipocyte hypertrophy and lipid dynamics underlie mammary gland remodeling after lactation

Adipocytes undergo pronounced changes in size and behavior to support diverse tissue functions, but the mechanisms that control these changes are not well understood. Mammary gland-associated white adipose tissue (mgWAT) regresses in support of milk fat production during lactation and expands during the subsequent involution of milk-producing epithelial cells, providing one of the most marked physiological examples of adipose growth. We examined cellular mechanisms and functional implications of adipocyte and lipid dynamics in the mouse mammary gland (MG). Using in vivo analysis of adipocyte precursors and genetic tracing of mature adipocytes, we find mature adipocyte hypertrophy to be a primary mechanism of mgWAT expansion during involution. Lipid tracking and lipidomics demonstrate that adipocytes fill with epithelial-derived milk lipid. Furthermore, ablation of mgWAT during involution reveals an essential role for adipocytes in milk trafficking from, and proper restructuring of, the mammary epithelium. This work advances our understanding of MG remodeling and tissue-specific roles for adipocytes.

Role of Liver X Receptor in Mastitis Therapy and Regulation of Milk Fat Synthesis.

Mastitis is important disease that causes huge economic losses in the dairy industry. In recent years, antibiotic therapy has become the primary treatment for mastitis, however, due to drug residue in milk and food safety factors, we lack safe and effective drugs for treating mastitis. Therefore, new targets and drugs are urgently needed to control mastitis. LXRα, one of the main members of the nuclear receptor superfamily, is reported to play important roles in metabolism, infection and immunity. Activation of LXRα could inhibit LPS-induced mastitis. Furthermore, LXRα is reported to enhance milk fat production, thus, LXRα may serve as a new target for mastitis therapy and regulation of milk fat synthesis. This review summarizes the effects of LXRα in regulating milk fat synthesis and treatment of mastitis and highlights the potential agonists involved in both issues.

Milk production and composition, food consumption, and energy balance of postpartum crossbred Holstein-Gir dairy cows fed two diets of different energy levels

The objective of this study was to evaluate the production, consumption, and energy balance parameters of primiparous 3/4 and 7/8 Holstein × Gir (HG) dairy cows fed two diets of differing energy levels during the postpartum period. At the beginning of the study, 28days prepartum, the average weight of both genetic groups was 498 ± 12kg and body condition score (BCS) was 3.5 ± 0.05. At the end of the study, 61days postpartum, the 3/4 HG cows had higher weight and body condition scores than the 7/8 HG (456 ± 8 and 429 ± 8kg and 3.13 ± 0.03 and 2.94 ± 0.03 BCS for 3/4 HG and 7/8 HG, respectively). Milk from cows fed the high-energy diet had higher percentages of fat, protein, lactose, and total dry extract than cows fed the low-energy diet. Cows fed the high-energy diet had higher net energy intake (95.3 ± 1.9 vs. 88.1 ± 2.1MJ/day) and higher energy balance (3.64 ± 2.13 vs - 6.02 ± 2.30MJ/day). The 3/4 HG cows displayed higher energy for maintenance (33.1 ± 0.4MJ/day) than the 7/8 HG (31.5 ± 0.5MJ /day). In conclusion, although the primiparous 3/4 HG were heavier than the 7/8 HG and had a higher body condition score, no differences in milk produced up to 60days postpartum were observed. The higher energy diet during the postpartum period increased energy balance, resulting in higher production of milk fat, protein, and lactose.

Feeding reduced-fat dried distillers grains with solubles to lactating Holstein dairy cows does not alter milk composition or cause late blowing in cheese

Feeding dried distillers grains with solubles (DDGS) to lactating dairy cows has been implicated as a cause of late blowing defects in the production of Swiss-style cheeses. Our objectives were (1) to test the effect of feeding reduced-fat DDGS (RF-DDGS; ∼6% fat) to lactating dairy cows on the composition of milk and on the suitability of the milk for production of baby Swiss cheese and (2) to evaluate the effect of diet on cow lactation performance. Lactating Holstein dairy cows were fed both dietary treatments in a 2 × 2 crossover design. Cows were housed in a 48-cow freestall pen equipped with individual feeding gates to record feed intake. The control diet was a corn, corn silage, and alfalfa hay diet supplemented with mechanically expelled soybean meal. The experimental diet was the same base ration, but 20% (dry matter basis) RF-DDGS were included in place of the expelled soybean meal. The RF-DDGS diet was additionally supplemented with rumen-protected lysine; diets were formulated to be isoenergetic and isonitrogenous. Cows were allowed ad libitum access to feed and water, fed twice daily, and milked 3 times daily. For cheese production, milk was collected and pooled 6 times for each dietary treatment. There was no treatment effect on milk yield (35.66 and 35.39 kg/d), milk fat production (1.27 and 1.25 kg/d), milk fat percentage (3.65 and 3.61%), milk protein production (1.05 and 1.08 kg/d), lactose percentage (4.62 and 4.64%), milk total solids (12.19 and 12.28%), and somatic cell count (232.57 and 287.22 × 103 cells/mL) for control and RF-DDGS, respectively. However, dry matter intake was increased by treatment, which implied a reduction in feed efficiency. Milk protein percentage also increased (3.01 and 3.11%), whereas milk urea nitrogen decreased (14.18 and 12.99 mg/dL), indicating that protein utilization may be more efficient when cows are fed RF-DDGS. No differences in cheese were observed by a trained panel except cheese appearance; control cheese eyes were significantly, but not practically, larger than the RF-DDGS cheese. These results indicate that RF-DDGS can be effectively used in the rations of lactating Holstein cows with no deleterious effects on milk production and composition and metrics of the physiology of the cow (i.e., blood glucose and nonesterified fatty acids); however, feeding RF-DDGS increased dry matter intake, which decreased feed efficiency. Finally, feeding RF-DDGS did not negatively influence quality and suitability of milk for production of baby Swiss cheese.

Milk Production of Ettawah Grade Goat Fed Diet Containing Different Protein and Energy Contents Supplemented with Organic Mineral and Grapes Seed Oil

This study aimed to investigate the effect of different protein and energy contents and supplementation ofZinc (Zn), Chromium (Cr) and grapes seed oil on milk production in dairy goat.Randomized block design(RBD) was used in this study. Twelve lactating Ettawah crossbreed goats divided into three groupsbased on milk production. The treatment ration were:T1 = ration containing 16% CPand 66% TDN; T2 = ration containing 14% CP and 63% TDN supplemented with Zn 20 ppm + Cr 2 ppm; and T3 = T2 + 22 ml grapes seed oil/head/day. The ration wasa dry complete feed in the form of pellet. The feed ingredients used were rice bran, cassava, wheat pollard, soybean meal, coconut meal, molasses, coffee husk and corn straw.Experiment was conducted over 30 days. Results revealed that the goat fed the ration supplemented with Zn and Cr(T2) producehigher milk yield (1012.29 g/day) and better in milk fat production (P<0.05)compared to those fedT1 and T3. Feed intake was decreased in treatment supplemented with grapes seed oil in the T3 (P<0.05), but no significant in milk fat production compared with T1. In conclusion,drycomplete feed containingof CP 14%, TDN 63% supplemented with Zn 20 ppm + Cr 2ppm is recommended for lactating dairy goat.

Yak milk fat globules from the Qinghai-Tibetan Plateau: Membrane lipid composition and morphological properties

Yak milk fat products constitute the base of Qinghai-Tibetan pastoralists’ daily food intake. Despite the great importance of fat in processing and pastoralists’ health, studies about yak milk fat are scarce. In this study, the lipid composition and the morphological properties of milk fat globule membranes (MFGMs) of yak milk were investigated. The results demonstrated that the yak milk had a higher cholesterol and sphingomyelin content compared to cow milk. In situ structural investigations performed at 25 °C by confocal microscopy showed the presence of lipid domains in yak MFGM, with a larger number and wider size range compared to cow milk. Moreover, the simultaneous localization of glycosylated molecules and polar lipids indicated that glycosylated molecules could be integrated into the lipid domains in yak MFGM. Different characteristics in yak MFGM could be related to the lipid composition and may affect the functions of yak milk lipids during processing and digestion.

Electronic Northern Analysis of Genes and Modeling of Gene Networks Underlying Bovine Milk Fat Production

Milk fat is one of the most important economic traits in dairy animals. Yet, the biological machinery involved in milk fat synthesis remains poorly understood. In the present study, expression profiling of 45 genes involved in lipid biosynthesis and secretion was performed using a computational approach to identify those genes that are differentially expressed in mammary tissue. Transcript abundance was observed for genes associated with nine bioprocesses, namely, fatty acid import into cells, xenobiotic and cholesterol transport, acetate and fatty acid activation and intracellular transport, fatty acid synthesis and desaturation, triacylglycerol synthesis, sphingolipid synthesis, lipid droplet formation, ketone body utilization, and regulation of transcription in mammary, skin, and muscle tissue. Relative expression coefficient of the genes was derived based on the transcript abundance across the three tissue types to determine the genes that were preferentially expressed during lactation. 13 genes (ACSS1, ACSS2, ADFP, CD36, FABP3, FASN, GPAM, INSIG1, LPL, SCD5, SPTLC1, SREBF1, and XDH) showed higher expression in the mammary tissue of which 6 (ADFP, FASN, GPAM, LPL, SREBF1, and XDH) showed higher expression during adulthood. Further, interaction networks were mapped for these genes to determine the nature of interactions and to identify the major genes in the milk fat biosynthesis and secretion pathways.

Negative effects of long-term feeding of high-grain diets to lactating goats on milk fat production and composition by regulating gene expression and DNA methylation in the mammary gland

BackgroundIt is well known that feeding a high concentrate (HC) diet to lactating ruminants likely induces subacute ruminal acidosis (SARA) and leads to a decrease in milk fat production. However, the effects of feeding a HC diet for long periods on milk fatty acids composition and the mechanism behind the decline of milk fat still remains poorly understood. The aim of this study was to investigate the impact of feeding a HC diet to lactating dairy goats on milk fat yield and fatty acids composition with an emphasis on the mechanisms underlying the milk fat depression. Seventeen mid-lactating dairy goats were randomly allocated to three groups. The control treatment was fed a low-concentrate diet (35% concentrate, n = 5, LC) and there were two high-concentrate treatments (65% concentrate, HC), one fed a high concentrate diet for a long period (19 wks, n = 7, HL); one fed a high concentrate diet for a short period of time (4 wk, n = 5, HS). Milk fat production and fatty acids profiles were measured. In order to investigate the mechanisms underlying the changes in milk fat production and composition, the gene expression involved in lipid metabolism and DNA methylation in the mammary gland were also analyzed.ResultsMilk production was increased by feeding the HC diet in the HS and HL groups compared with the LC diet (P < 0.01), while the percentage of milk fat was lower in the HL (P < 0.05) but not in the HS group. The total amount of saturated fatty acids (SFA) in the milk was not changed by feeding the HC diet, whereas the levels of unsaturated fatty acids (UFA) and monounsaturated fatty acids (MUFA) were markedly decreased in the HL group compared with the LC group (P < 0.05). Among these fatty acids, the concentrations of C15:0 (P < 0.01), C17:0 (P < 0.01), C17:1 (P < 0.01), C18:1n-9c (P < 0.05), C18:3n-3r (P < 0.01) and C20:0 (P < 0.01) were markedly lower in the HL group, and the concentrations of C20:0 (P < 0.05) and C18:3n-3r (P < 0.01) were lower in the HS group compared with the LC group. However, the concentrations of C18:2n-6c (P < 0.05) and C20:4n-6 (P < 0.05) in the milk fat were higher in the HS group. Real-time PCR results showed that the mRNA expression of the genes involved in milk fat production in the mammary gland was generally decreased in the HL and HS groups compared with the LC group. Among these genes, ACSL1, ACSS1 & 2, ACACA, FAS, SCD, FADS2, and SREBP1 were down-regulated in the mammary gland of the HL group (P < 0.05), and the expressions of ACSS2, ACACA, and FADS2 mRNA were markedly decreased in the HS goats compared with the LC group (P < 0.05). In contrast to the gene expression, the level of DNA methylation in the promoter regions of the ACACA and SCD genes was increased in the HL group compared with the LC group (P < 0.05). The levels of ACSL1 protein expression and FAS enzyme activity were also decreased in the mammary gland of the HL compared with the LC group (P < 0.05).ConclusionsLong-term feeding of a HC diet to lactating goats induced milk fat depression and FAs profile shift with lower MUFAs but higher SFAs. A general down-regulation of the gene expression involved in the milk fat production and a higher DNA methylation in the mammary gland may contribute to the decrease in milk fat production in goats fed a HC diet for long time periods.

Surgical treatment in deep digital sepsis in cattle – Claw preserving methods and claw amputation

Still today lameness represents a major health problem in many dairy farms with prevalences ranging from 0 to 70%; mean prevalence rates of about 36% were reported by many authors. Unfortunately, the lameness prevalence is highly underestimated by farmers. An acceptable lameness prevalence in dairy herds regarding ethical and economical considerations is 5% to maximal 10%. Lameness continues to be one of the largest economic drains on dairy farming and is one of the three most common reason for culling, preceded by reproductive failure and mastitis. Lameness results in direct loss via culling as well as indirect loss via decreased production of milk, milk fat and protein, reproductive failure, prolonged calving interval, extra labor of the dairy farmer and the foot trimmer, extra visits of the veterinarian, treatment costs and costs for discarded milk.

Wheat is more potent than corn or barley for dietary mitigation of enteric methane emissions from dairy cows

Wheat is the most common concentrate fed to dairy cows in Australia, but few studies have examined the effects of wheat feeding on enteric methane emissions, and no studies have compared the relative potencies of wheat, corn, and barley for their effects on enteric methane production. In this 35-d experiment, 32 Holstein dairy cows were offered 1 of 4 diets: a corn diet (CRN) of 10.0 kg of dry matter (DM)/d of single-rolled corn grain, 1.8 kg of DM/d of canola meal, 0.2 kg of DM/d of minerals, and 11.0 kg of DM/d of chopped alfalfa hay; a wheat diet (WHT) similar to the CRN diet but with the corn replaced by single-rolled wheat; a barley diet (SRB) similar to the CRN diet but with the corn replaced by single-rolled barley; and a barley diet (DRB) similar to the CRN diet but with the corn replaced by double-rolled barley. Individual cow feed intakes, milk yields, and milk compositions were measured daily but reported for the last 5 d of the experiment. During the last 5 d of the experiment, individual cow methane emissions were measured using the SF6 tracer technique for all cows, and ruminal fluid pH was continuously measured by intraruminal sensors for 3 cows in each treatment group. The average DM intake of cows offered the CRN, WHT, SRB, and DRB diets was 22.2, 21.1, 22.6, and 22.6 kg/d. The mean energy-corrected milk of cows fed the WHT diet was less than that of cows fed the other diets. This occurred because the milk fat percentage of cows fed the WHT diet was significantly less than that of cows fed the other diets. The mean methane emissions and methane yields of cows fed the WHT diet were also significantly less than those of cows fed the other diets. Indeed, the CRN, SRB, and DRB diets were associated with 49, 73, and 78% greater methane emissions, respectively, compared with the emissions from the WHT diet. Methane yield was found to be most strongly related to the minimum daily ruminal fluid pH. This study showed that although the inclusion of wheat in the diet of dairy cows could be an effective strategy for substantially reducing their methane emissions, it also reduced their milk fat percentage and production of milk fat and energy-corrected milk.

Effect of Month and Season of Birth on Milk Quantity and Quality of Holstein Friesian Cows in Kabul Bini Hisar Dairy Farm

AEffect of calving month and season on productive traits of Holstein dairy cows. In Kabul Bini Hisar Dairy farm. Productive data on 305 days lactation period for 49 Holstein dairy cows, which were collected during one month from dairy cattle in Beni Hisar Farm in Kabul province using recorded data from 1389 to 1392 years, were used to estimate the effect of calving month and season for the purpose of estimating the correlation between milk yield, fat production and fat percentage of the Holstein dairy cows. General linear model (GLM) procedure and SPSS software were used for the estimation of the effect calving month and seasons. The results showed calving month influenced significantly on productive traits (P < 0.05). The greatest milk and fat production (kg) were observed in dairy cows that calved in December. In addition, dairy cows that calved in October had the greatest fat percentage totally, the results showed, animals that calved in fall season had greater performance than the others. Naturally, milk production of these animals reached production peak in winter when the weather and nutritional conditions are suitable for production.

Increasing dietary levels of citral oil on nutrient total tract digestibility, ruminal fermentation, and milk composition in Saanen goats

This study was undertaken to evaluate the effects of increasing dietary doses of high purity citral oil on nutrient total tract digestibility, ruminal fermentation, blood metabolites, milk yield and composition, and N utilization in dairy goats. Twenty-four Saanen goats [62±1.4kg of body weight (BW), 75±20days in milk, and 3.0±0.27kg/d of milk yield, at the start of experiment], being eight of them rumen-cannulated, were used in a 4×4 Latin square design experiment with 21-d periods in which the first 14 d were allowed to treatment adaptation. Animals were assigned to the following treatments: control, with no citral supply; and dietary addition of 0.08, 0.16 or 0.24mL of citral oil per kg of BW. Increasing doses of citral oil did not affect dry matter (DM) and nutrient intake, but it linearly decreased neutral detergent fiber total tract digestion in dairy goats. Treatments neither affected ruminal pH nor NH3N, but citral oil linearly increased butyrate proportion in ruminal fluid of goats. Citral oil consumption had a positive quadratic effect on ruminal propionate (mmol/dL and mmol/100mmol) and butyrate (mmol/dL) in goats. Treatments had a negative quadratic effect on ruminal acetate to propionate ratio and acetate proportion. Citral consumption by dairy goats linearly decreased blood urea concentration. Although treatments did not affect milk and fat-corrected milk yield, citral oil linearly decreased milk fat production in goats. Citral had no effect on milk fatty acid profile and N utilization in goats. Citral consumption had no effect on DM and nutrient intake as well as on fat-corrected milk yield, but it may increase ruminal propionate concentration in dairy goats.

Producción, calidad de leche y beneficio:costo de suplementar vacas holstein con Tithonia diversifolia

The aim of this study was to analyze the milk production, quality and cost:benefit ratio the addition of three levels (0%, 15% and 25%) our of Tithonia diversifolia in the supplement of Holstein cows. In a bovine milk production system in a high tropic were used nine cows (70 to 120 milk days and parity two to ve). They were randomly assigned in three groups, which grazed on Kikuyo grass (Cenchrus clandestinus) in La Montaña farm, located in San Pedro de los Milagros, Antioquia, Colombia, at 2350 meters above sea level. This study was carried out during March 2015. At 56 days, T. diversifolia (wild sunflower) from a fodder bank located at 2456 masl was harvested, and dried using marquees ground for an approximate period of time of ten days, it was then minced and stored to prepare isoenergetics (1.8 Mcal NEL/kg) and isoproteics (14% CP) supplements. The study evaluated its effect on dry matter intake (DMI), corrected milk production (4% fat, FCM), milk composition (protein, fat, lactose, total solids, milk urea nitrogen –MUN), somatic cell count (SCC), produced milk: supplement intake and cost:benefit ratio. The results showed signi cant differences for the inclusion of 25% of T. diversifolia flour in the supplement for benefit:cost ratio, lactose, MUN, SCC and produced milk:supplement intake ratio, contrary to what happened with DMI, corrected 4% fat milk production, protein, fat and total solids that not differ. The addition of 25% of wild sunflower in the supplement for grazing dairy cows improved the milk quality in reference to lactose concentration, efficiency in the use of the supplement, cost:benefit ratio.

Production of new human milk fat substitutes by enzymatic acidolysis of microalgae oils from Nannochloropsis oculata and Isochrysis galbana

Human milk fat substitutes (HMFs) with four kinds of n-3 fatty acid for infant formula were firstly synthesized using triacylglycerols (TAGs) from Nannochloropsis oculata rich in PA at the sn-2 position and free fatty acids (FFAs) from Isochrysis galbana rich in n-3 polyunsaturated fatty acids (n-3 PUFAs-ALA/SDA/DHA) via solvent-free acidolysis with Novozym 435, Lipozyme 435, TL-IM and RM-IM as biocatalysts. The results show that the resulting HMFs contain total n-3 PUFA of 13.92–17.12% and PA of 59.38–68.13% at the sn-2 position under the optimal conditions (mole ratio FFAs/TAG 3:1, 60°C (Novozym 435 and Lipozyme TL-IM) and 50°C (Lipozyme 435 and RM-IM), lipase loading 10%, reaction time 24h). Moreover, among the tested enzymes, Lipozyme 435, TL-IM, and RM-IM display the fatty acid selectivity towards SDA, LA and ALA, and OA, respectively. Overall, the examined lipases are promising biocatalysts for producing high-value microalgal HMFs in a cost-effective manner.

Vitamin Fortification of Fluid Milk.

Vitamin concentrates with vitamins A and D are used for fortification of fluid milk. Although many of the degradation components of vitamins A and D have an important role in flavor/fragrance applications, they may also be source(s) of off-flavor(s) in vitamin fortified milk due to their heat, oxygen, and the light sensitivity. It is very important for the dairy industry to understand how vitamin concentrates can impact flavor and flavor stability of fluid milk. Currently, little research on vitamin degradation products can be found with respect to flavor contributions. In this review, the history, regulations, processing, and storage stability of vitamins in fluid milk are addressed along with some hypotheses for the role of vitamin A and D fortification on flavor and stability of fluid milk.

Effect of pre-calving body condition score and previous lactation on BCS change, blood metabolites, oxidative stress and milk production in Holstein dairy cows

The aim of study was to determine the effect of pre-calving body condition score (BCS) and previous milk yield on BCS change, blood metabolites, oxidative stress and milk production in Holstein cows. At 3 wk before expected calving, 100 multiparous cows were grouped according to their BCS and then classified based the previous 305 milk yield. The four experimental groups (25 cows each) were medium BCS and moderate milk yield (MM), medium BCS and high milk yield (MH), high BCS and moderate milk yield (HM), and high BCS and high milk yield (HH). The cows’ BCS was recorded at −21, 0, 21, 50 and 80 d related to parturition time. Daily milk production of cows was recorded after parturition. Blood samples were taken at d −21, −7, +1, +7 and +21 postpartum. The HH cows had lower (p <.05) plasma insulin than MH group. Also, the HH cows had lowest (p <.05) plasma insulin at 7 d after calving. Cows with high BCS had greater (p <.05) NEFA and BHBA concentration than medium BCS groups. Cows with high BCS had lower activity of antioxidant enzymes (p <.05) compared to medium BCS groups. Milk production, fat-corrected milk (FCM) and energy-corrected milk (ECM) were affected (p <.05) by pre-calving BCS and previous milk yield. Pre-calving BCS and previous milk yield affect (p <.05) milk fat production. In conclusion, the HH cows have greater milk production; however they are susceptible to oxidative stress and metabolic disorders risk based on their blood metabolites.

Effect of short-term feed restriction on temporal changes in milk components and mammary lipogenic gene expression in mid-lactation Holstein dairy cows

Investigations of the temporal changes in mammary gene expression that occur during sudden diet change have been limited by the use of mammary tissue as the source of RNA because of the invasive nature of mammary biopsy procedures. However, the cytosolic crescent, present in 1% of the largest milk fat globules, contains mammary epithelial cell RNA that has become trapped between the inner and outer milk fat globule membranes during final formation and secretion of milk fat into the lumen of the mammary alveoli. We hypothesized that cytosolic crescent RNA extracted from milk fat could be used as an alternative source of mammary epithelial cell RNA to measure the immediate temporal changes in gene expression as a result of changes in diet. In this experiment, feed restriction was used to mimic the state of negative energy balance observed in early lactation and induce a rapid change in milk fat yield and lipogenic gene expression. Ten multiparous Holstein dairy were fed a basal diet ad libitum during a 14-d preliminary period followed by a 4-d experimental period where 5 cows remained on ad libitum feeding and 5 cows were fed at 60% of their d 8-14 intakes (restricted) on d 15 to 18 and then returned to ad libitum feeding on d 19 to 21. Milk samples were collected from each milking on d 13 to 20 and the milk fat was immediately isolated, mixed with Trizol LS, and stored at -80°C for subsequent extraction of RNA that was used for measurement of gene expression. Feed restriction tended to increase milk fat percentage. However, total milk and milk fat production were reduced by 21 and 18%, respectively. Consistent with increased use of body fat for milk synthesis, serum nonesterified fatty acids increased 6-fold (0.78 mEq/L in the feed restriction vs. 0.13 mEq/L ad libitum group), whereas the milk fatty acids <C16 decreased and ≥C16 increased by 6.5 percentage units. The lipogenic genes ACACA, FASN, and SCD1, and the transcription factor SREBF1were downregulated by 59, 36, 35, and 43%, respectively, during the feed restriction period. In addition, effects of feed restriction by day within period were detected for the genes AGPAT6, GPAM, BTN1A, and SREBF1, suggesting that temporal (day-to-day) changes in gene expression could also be detected. The results of this experiment were consistent with previous feed restriction studies in which researchers used the mammary biopsy technique to study gene expression in the mammary gland. We concluded that RNA isolated from milk fat could be used as an alternative approach to investigate rapid temporal changes in lipogenic gene expression.

Production responses of Holstein dairy cows when fed supplemental fat containing saturated free fatty acids: a meta-analysis.

ObjectiveA meta-analysis was conducted to evaluate the effects of supplemental fat containing saturated free fatty acids (FA) on milk performance of Holstein dairy cows.MethodsA database was developed from 21 studies published between 1991 and 2016 that included 502 dairy cows and a total of 29 to 30 comparisons between dietary treatment and control without fat supplementation. Only saturated free FA (>80% of total FA) was considered as the supplemental fat. Concentration of the supplemental fat was not higher than 3.5% of diet dry matter (DM). Dairy cows were offered total mixed ration, and fed individually. Statistical analysis was conducted using random- or mixed-effects models with Metafor package in R.ResultsSub-group analysis showed that there were no differences in studies between randomized block design and Latin square/crossover design for dry matter intake (DMI) and milk production responses to the supplemental fat (all response variables, p≥0.344). The supplemental fat across all studies improved milk yield, milk fat concentration and yield, and milk protein yield by 1.684 kg/d (p<0.001), 0.095 percent unit (p = 0.003), 0.072 kg/d (p<0.001), and 0.036 kg/d (p<0.001), respectively, but tended to decrease milk protein concentration (mean difference = −0.022 percent unit; p = 0.063) while DMI (mean difference = 0.061 kg/d; p = 0.768) remained unchanged. The assessment of heterogeneity suggested that no substantial heterogeneity occurred among all studies for DMI and milk production responses to the supplemental fat (all response variables, I2≤24.1%; p≥0.166).ConclusionThe effects of saturated free FA were quantitatively evaluated. Higher milk production and yields of milk fat and protein, with DMI remaining unchanged, indicated that saturated free FA, supplemented at ≤3.5% dietary DM from commercially available fat sources, likely improved the efficiency of milk production. Nevertheless, more studies are needed to assess the variation of production responses to different saturated free FA, either C16:0 or C18:0 alone, or in combination with potentially optimal ratio, when supplemented in dairy cow diets.

2,4-Thiazolidinedione Treatment Improves the Innate Immune Response in Dairy Goats with Induced Subclinical Mastitis.

Mastitis is a major disease in dairy cows resulting in significant economic losses. In vitro works suggest that ruminants peroxisome proliferator-activated receptor gamma (PPARγ) can aid in improving the response to mastitis and can control milk fat synthesis. The objectives of the present experiment were to test if treatment with the putative PPARγ agonist 2,4-thiazolidinedione (TZD) improves (1) the response to subclinical mastitis and (2) milk fat production. Lactating goats received daily injections of 8 mg/kg BW of TZD or saline for 3 weeks. After one week of TZD injection, half of the goats in each group received intramammary infusion of Strep. uberis or saline in both halves for a total of 4 groups (n = 6/group). TZD treatment did not affect milk fat but had positive effect on milk somatic cells count, blood nonesterified fatty acids, inflammatory markers, and liver function. TZD significantly increased myeloperoxidase but did not affect leukocytes phagocytosis or insulin. TZD increased adipocytes size and had minor effect on expression of PPARγ target genes in mammary epithelial cells but not in adipose tissue. Overall, TZD ameliorated the response to intramammary infection but the effect on milk fat synthesis and expression of related transcripts was less than expected.