Associations between peripartum lying and activity behaviour and blood non-esterified fatty acids and β-hydroxybutyrate in grazing dairy cows

During early lactation, most dairy cows experience negative energy balance (NEB). Failure to cope with this NEB, however, can place cows at greater risk of developing metabolic disease. Our objective was to characterise, retrospectively, lying behaviour and activity of grazing dairy cows grouped according to blood non-esterified fatty acids (NEFAs) and β-hydroxybutyrate (BHB) as indicators of postpartum metabolic state. Blood was sampled weekly for up to 4 weeks precalving, on the day of calving (day 0), daily between 1 and 4 days postcalving, and then at least weekly between week 1 and week 5 postcalving for analysis of plasma NEFAs and BHB concentrations. Two hundred and forty-four multiparous Holstein-Friesian and Holstein-Friesian × Jersey cows were classified into one of three metabolic status groups based on maximum blood NEFAs and BHB concentrations during week 1 and 2 postcalving. A cow was classified as having either: (1) low NEFAs and low BHB (Lo–Lo; n = 78), when all blood samples were <1.0 mmol/L for NEFAs and ≤1.0 mmol/L for BHB during the first 2 weeks postcalving; (2) high NEFAs and low BHB (Hi–Lo; n = 134), when blood NEFAs were ≥1.0 mmol/L and blood BHB was ≤1.0 mmol/L at the same sampling time point during the first 2 weeks postcalving; or (3) high NEFAs and high BHB (Hi–Hi; n = 32), when blood NEFAs were ≥1.0 mmol/L and blood BHB was ≥1.2 mmol/L at the same sampling time point during the first 2 weeks postcalving. Accelerometers (IceTag or IceQube devices; IceRobotics Ltd.) were used to monitor lying and activity behaviours peripartum (–21 to +35 days relative to calving). Changes in lying behaviour and activity occurred before the mean day that cows were classified Hi–Hi and Hi–Lo (2.2 and 3.5 d postcalving, respectively). Up to 3 weeks preceding calving, Hi–Hi cows were more active, had fewer daily lying bouts (LBs), and spent less time lying than Lo–Lo cows. In addition, Hi–Hi cows had fewer daily LBs and were less active up to 4 weeks postcalving than Lo–Lo cows, but these differences were biologically small. Groups of grazing cows classified as experiencing a more severe metabolic challenge behave differently up to 3 weeks precalving than their herdmates with lower blood NEFAs and BHB postcalving. These altered behaviours may allow identification of individual cows at risk of a metabolic challenge, but further research is required.     

Novel insights into heat tolerance using metabolomic and high-throughput sequencing analysis in dairy cows rumen fluid

Heat stress influences rumen fermentative processes with effects on the physiology and production of dairy cows. However, the underlying relationship between rumen microbiota and its associated metabolism with heat tolerance in cows have not been extensively described yet. Therefore, the main objective of this study was to investigate differential heat resistance in Holstein cows using rumen bacterial and metabolome analyses. We performed both principal component analysis and membership function analysis to select seven heat-tolerant (HT) and seven heat-sensitive (HS) cows. Under heat stress conditions, the HT cows had a significantly (P < 0.05) higher propionic acid content than the HS cows; while measures of the respiratory rate, acetic, and butyric acid in the HT cows were significantly (P < 0.05) lower compared with the HS cows. Also, the HT cows showed lower (P < 0.01) rectal temperature and acetic acid to propionic acid ratio than the HS group of cows. Omics sequencing revealed that the relative abundances of Muribaculaceae, Rikenellaceae, Acidaminococcaceae, Christensenellaceae, Rikenellaceae_RC9_gut_group, Succiniclasticum, Ruminococcaceae_NK4A214_group and Christensenellaceae_R-7_group were significantly (P < 0.01) higher in the HT cows; whereas Prevotellaceae, Prevotella_1, Ruminococcaceae_UCG-014, and Shuttleworthia were significantly (P < 0.01) lower in HT cows compared to HS cows. Substances mainly involved in carbohydrate metabolism, including glycerol, mannitol, and maltose, showed significantly higher content in the HT cows (P < 0.05) compared to that in the HS cows. Simultaneously, distinct metabolites were significantly correlated with differential bacteria, suggesting that glycerol, mannitol, and maltose could serve as potential biomarkers for determining heat resistance that require further study. Overall, distinct changes in the rumen microbiota and metabolomics in the HT cows may be associated with a better adaptability to heat stress. These findings suggest their use as diagnostic tools of heat tolerance in dairy cattle breeding schemes.     

Effects of replacing soybean meal with pumpkin seed cake and dried distillers grains with solubles on milk performance and antioxidant functions in dairy cows

Pumpkin seed cake (PSC), a byproduct of pumpkin seed oil processing, is used in ruminant feed as a beneficial protein source. Experiments were conducted to evaluate PSC as a substitute for soybean meal in the diets of lactating cows based on performance, rumen fermentation, antioxidant function and nitrogen partitioning. Six multiparous lactating cows were used in a replicated 3 × 3 Latin square experiment with 27-day periods. The cows were randomly divided into three treatment groups: group (1) was fed a diet containing no PSC (0PSC), and groups (2) and (3) were fed diets in which soybean meal was replaced with PSC and dried distillers grains with solubles (DDGS) at levels of 50% (50PSC) and 100% (100PSC), respectively. The diets were isonitrogenous and contained identical roughage but different proportions of PSC and DDGS. Replacement of soybean meal with PSC and DDGS did not influence rumen degradation, milk performance, rumen fermentation, DM intake or apparent total tract digestibility, and nitrogen partitioning between milk, feces and urine did not differ in the animals fed the three diets. However, compared with a diet containing no PSC, the total antioxidant capacity (P < 0.05) and antioxidant enzymes (total superoxide dismutase, glutathione peroxidase and catalase) activities (P < 0.05) were increased in the animals that received the 50PSC and 100PSC diets. In contrast, addition of PSC significantly reduced concentrations of aspartate transaminase (P < 0.05), alkaline phosphatase (P < 0.05) and malondialdehyde (P < 0.05) in the plasma. These results demonstrate that PSC can be completely substituted for soybean meal in the diet of dairy cows without any negative impact on milk performance, rumen fermentation or apparent digestibility and that this dietary change improves antioxidant functions and blood parameters in dairy cows, indicating that PSC has the potential for use as a feed source for dairy cows.     

Milk production responses and rumen fermentation of dairy cows supplemented with summer brassicas

Forage brassicas, such as summer turnip (ST; Brassica rapa) and forage rape (FR; Brassica napus), are used as supplementary crops during summer. However, studies with lactating dairy cows fed these forages are limited and report inconsistent productive responses. The aim of this study was to determine dry matter intake, rumen fermentation and milk production responses of dairy cows in mid-lactation supplemented with and without summer (‘ST’ or ‘FR’) brassicas. Twelve multiparous lactating dairy cows were randomly allocated to three dietary treatments in a replicated 3 × 3 Latin square design balanced for residual effects over three 21-day periods. The control diet consisted of 16.2 kg DM of grass silage, 2.25 kg DM of commercial concentrate and 2.25 kg DM solvent-extracted soybean meal. For the other two dietary treatments, 25% of the amounts of silage and concentrates were replaced with FR or ST. The inclusion of forage brassicas had no effects on milk production (24.2 kg cow/day average) and composition (average milk fat and protein 43.2 and 33.6 g/l, respectively). Dry matter intake was 0.98 kg and 1.12 kg lower for cows supplemented with FR and ST, respectively, resulting in a greater feed conversion efficiency (1.35 kg milk/kg DM for ST and FR v. 1.27 kg milk/kg DM for the control diet). Intraruminal pH was lower for cows supplemented with ST compared to the control diet; however, it did not decrease below pH 5.8 at any time of the day. After feeding, the concentrations of total short-chain fatty acids (SCFAs) in rumen contents increased with ST supplementation compared to the control diet. Inclusion of FR in the diet increased the molar proportion of acetate (68.5 mmol/100 mmol) in total SCFA at the expense of propionate, measured 6 h after feeding of the forage. The molar proportion of butyric acid was greater with ST and FR supplementation (13.1 and 12 mmol/100 mmol, respectively) than in control cows. The estimated microbial nitrogen (N) flow was 89.1 g/day greater when supplementing FR compared to the control diet. Based on the haematological measures, the inclusion of summer brassica forages did not affect the health status of the animals. These results indicate that mid-lactation dairy cows fed brassicas are able to maintain production despite the reduced intake, probably due to improved rumen fermentation and therefore nutrient utilization.     

Rubber seed oil and flaxseed oil supplementation alter digestion,ruminal fermentation and rumen fatty acid profile of dairy cows

Rubber seed oil (RO) that is rich in polyunsaturated fatty acids (FA) can improve milk production and milk FA profiles of dairy cows; however, the responses of digestion and ruminal fermentation to RO supplementation in vivo are still unknown. This experiment was conducted to investigate the effect of RO and flaxseed oil (FO) supplementation on nutrients digestibility, rumen fermentation parameters and rumen FA profile of dairy cows. Forty-eight mid-lactation Holstein dairy cows were randomly assigned to one of four treatments for 8 weeks, including basal diet (CON) or the basal dietary supplemented with 4% RO, 4% FO or 2% RO plus 2% FO on a DM basis. Compared with CON, dietary oil supplementation improved the total tract apparent digestibility of DM, neutral detergent fibre and ether extracts ( P < 0.05). Oil treatment groups had no effects on ruminal digesta pH value, ammonia N and microbial crude protein ( P > 0.05), whereas oil groups significantly changed the volatile fatty acid (VFA) profile by increasing the proportion of propionate whilst decreasing total VFA concentration, the proportion of acetate and the ratio of acetate to propionate ( P < 0.05). However, there were no differences in VFA proportions between the three oil groups (P > 0.05). In addition, dietary oil supplementation increased the total unsaturated FA proportion in the rumen by enhancing the proportion of trans-11 C18:1 vaccenic acid (VA), cis-9, trans-11 conjugated linoleic acid (CLA) and α-linolenic acid (ALA) ( P < 0.05). These results indicate that dietary supplementation with RO and FO could improve nutrients digestibility, ruminal fermentation and ruminal FA profile by enhancing the VA, cis-9, trans-11 CLA and ALA composition of lactating dairy cows. These findings provide a theoretical basis for the application of RO in livestock production.     

Effects of dietary conjugated linoleic acid on metabolic status,BW and expression of genes related to lipid metabolism in adipose tissue of dairy cows during peripartum

Conjugated linoleic acid (CLA) dietary supplementation reduces milk fat content and yield, but its effects on lipid metabolism and energy status remain controversial. The objective of this study was to investigate the effects of dietary CLA on adipose tissue (AT) mRNA abundance of genes related to lipid metabolism, plasma indicators of metabolic status, body condition score (BCS) and BW changes in dairy cows. Sixteen multiparous Holstein cows (3.2 ± 1.4 lactations, 615 ± 15 kg BW) were randomly assigned to treatments: 1) CLA; rumen-protected CLA (75 g/d) or 2) Control; equivalent amount of rumen inert fatty acid (FA) as the previous diet (78 g/d), from − 20.2 ± 3.2 (mean ± SEM) to 21 d relative to calving (d 0). Subcutaneous AT was biopsied from the tail-head region at d 21 to determine the mRNA abundance of genes related to lipid metabolism. Blood samples were collected at − 20.2 ± 3.2, 0, 7, 14 and 21 d relative to calving to determine plasma non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHBA), insulin and glucose. Conjugated linoleic acid decreased milk fat yield and milk fat content by 15 and 16%, respectively. Cows fed CLA had lower plasma NEFA and BHBA and greater glucose and insulin concentrations (P < 0.05). Mean BCS at 21 d postpartum was greater (P < 0.01; 2.89 vs 2.25), and BCS loss from the day of enrollment to 21 d postpartum was reduced (P < 0.01; − 0.13 vs − 0.64) in the CLA group. The expression of acylcoenzyme A oxidase, carnitine palmitoyltransferase 1A, hormone-sensitive lipase, β2 adrenergic receptor and acetyl-CoA carboxylase was downregulated by CLA supplementation, whereas the expression of sterol regulatory element binding protein, lipoprotein lipase and peroxisome proliferator-activated receptor gamma was upregulated (P < 0.01). In summary, CLA-supplemented cows showed signs of better metabolic status and less severe fat mobilization. Moreover, CLA increased mRNA abundance of genes related to lipogenesis and decreased mRNA abundance of genes related to FA oxidation and lipolysis in the AT of dairy cows during early lactation.     

Effects of an artificial hay aroma and compound feed formulation on feed intake pattern,rumen function and milk production in lactating dairy cows

The Kempen system is a dairy feeding system in which diet is provided in the form of a compound feed (CF) and hay offered ad libitum. Ad libitum access to CF and hay allows cows in this system to achieve a high DM intake (DMI). Out of physiological concerns, the voluntary hay intake could be increased and the consumption pattern of CF could be manipulated to maintain proper rumen functioning and health. This study investigated the effects of an artificial hay aroma and CF formulation on feed intake pattern, rumen function and milk production in mid- to late-lactating dairy cows. Twenty Holstein–Friesian cows were assigned to four treatments in a 4 × 4 Latin square design. Diet consisted of CF and grass hay (GH), fed separately, and both offered ad libitum, although CF supply was restricted in maximum meal size and speed of supply by an electronic system. Treatments were the combination of two CF formulations – high in starch (CHS) and fibre (CHF); and two GH – untreated (UGH) and the same hay treated with an artificial aroma (TGH). Meal criteria were determined using three-population Gaussian–Gaussian–Weibull density functions. No GH × CF interaction effects on feed intake pattern characteristics were found. Total DMI and CF intake, but not GH intake, were greater (P < 0.01) in TGH treatment, and feed intake was not affected by type of CF. Total visits to feeders per day, visits to the GH feeder, visits to the CF feeder and CF eating time (all P < 0.01) were significantly greater in cows fed with TGH. Meal frequency, meal size and meal duration were unaffected by treatments. Cows fed CHF had a greater milk fat (P = 0.02), milk urea content (P < 0.01) and a greater milk fat yield (P < 0.01). Cows fed TGH had a greater milk lactose content and lactose yield (P < 0.05), and milk urea content (P < 0.01). Cows fed TGH had smaller molar proportions of acetic acid and greater molar proportions of propionic acid compared with UGH. In conclusion, treatment of GH with an artificial aroma increased CF intake and total DMI, but did not affect hay intake. Additionally, GH treatment increased the frequency of visits to both feeders, and affected rumen volatile fatty acid profile. Type of CF did not affect meal patterns, ruminal pH, nor fermentation profiles.     

Bacterial communities in the rumen and feces of lactating Holstein dairy cows are not affected when fed reduced-fat dried distillers’ grains with solubles

Reduced-fat dried distillers’ grains with solubles (RF-DDGSs) are co-products of ethanol production and contain less fat than traditional distillers’ grains. The fat in corn is ~91% unsaturated, and it is toxic to rumen microorganisms so it could influence the composition of the rumen microbiome. It has been demonstrated that RF-DDGS is a suitable ration ingredient to support the high-producing dairy cow, and this feedstuff is a promising alternative protein source for lactating dairy cows. The current study aims to better understand the effect of RF-DDGS on the rumen and fecal bacterial composition in lactating dairy cows. Thirty-six multiparous (two or three), mid-lactation Holstein cows (BW = 680 ± 11 kg; 106 ± 27 DIM) were randomly assigned to two groups which were fed a control diet made up of corn, corn silage, and alfalfa hay supplemented with expeller soybean meal or with added RF-DDGS (20% of the DM) containing approximately 6.0% fat. Whole rumen contents (rumen fluid and digesta; esophageal tubing method) and feces (free-catch method) were collected on day 35 of the experimental period, after the 14-d acclimation period. Rumen contents and feces from each cow were used for DNA extraction. The bacterial community composition in rumen and fecal samples was assessed via the 16S rRNA gene by using the Illumina MiSeq sequencing platform. Bacteroidetes, Actinobacteria, and Firmicutes were the most abundant phyla in rumen contents. The fecal microbiota was dominated by the phyla Firmicutes and Bacteroidetes, as well as Actinobacteria and Chloroflexi. RF-DGGS increased bacterial richness, evenness, and Shannon diversity in both rumen and fecal samples and was associated with several taxa that had different abundance in treatment versus control comparisons. The RF-DGGS, however, did not significantly alter the bacterial community in the rumen or feces. In general, these findings demonstrated that dietary inclusion of RF-DDGS did not impose any serious short-term (within 30 days) health or production consequences, as would be expected. With this study, we present further evidence that inclusion of 20% (DM basis) RF-DDGS in the diet of lactating dairy cows can be done without consequence on the microbiome of the rumen.     

Short communication: Variance and autocorrelation of deviations in daily milk yield are related with clinical mastitis in dairy cows

Daily milk production, and fluctuations therein, can provide information on health and resilience of dairy cows. We studied variance and autocorrelation of deviations in daily milk yield in relation to the occurrence of clinical mastitis (no, early or later in lactation). Individual lactation curves were fitted to 305-d lactations of 414 dairy cows using quantile regression. Log-transformed variance (lnVar) and autocorrelation of the quantile residuals of daily milk yield (predicted – observed) were evaluated for intervals until 30 and until 305 days in milk (DIM). Cows were classified as having no mastitis (n = 249), early mastitis that first occurred before 30 DIM (n = 29); or later mastitis (n = 136). Subsequently, linear models were used to assess effects of mastitis and parity class (primiparous or multiparous) on lnVar and autocorrelations; and logistic regression analyses were performed to predict mastitis from lnVar or autocorrelation and parity. From 10 to 30 DIM, lnVar was greater for cows with early mastitis than for cows with no or late mastitis, and autocorrelation tended to be lower for cows with early mastitis than for cows with no mastitis. The lnVar and autocorrelation from 10 to 30 DIM were not predictive of late mastitis. From 10 to 305 DIM, lnVar was greater and autocorrelation was lower for both cows with early and late mastitis than for cows with no mastitis; and both were predictive of having mastitis in the 305-d lactation. Primiparous cows had lower lnVar than multiparous cows. In cows without mastitis, autocorrelation values were positively correlated with lnVar. Results confirm that increased lnVar is associated with clinical mastitis.     

Effects of a combination of fibrolytic and amylolytic enzymes on ruminal enzyme activities,bacterial diversity,blood profile and milk production in dairy cows

We hypothesised that adding a combination of fibrolytic and amylolytic enzymes to the diet of early-lactation dairy cows would improve rumen enzyme activity and bacterial diversity, promote energy metabolism, and benefit milk production in cows. Twenty multiparous early-lactation (90 ± 5 d) Holstein cows with similar body conditions were randomly allocated to control (CON, n = 10) and experimental (EXP, n = 10) groups in a completely randomised single-factor design. The CON was fed only a basal total mixed ration diet, and the diet of the EXP was supplemented with a combination of fibrolytic and amylolytic enzymes at 70 g/cow/d (cellulase 3 500 CU/g, xylanase 2 000 XU/g, β-glucanase 17 500 GU/g, and amylase 37 000 AU/g). The experiment lasted 28 days, with 21 days for adaptation and 7 days for sampling. Enzyme addition increased the activity levels of α-amylase and xylanase, and the ammonia-N concentration (P < 0.05) tended to increase the activity of β-glucanase (P = 0.08) in rumen fluid. However, there was no significant difference in the rumen bacterial richness and diversity, phylum (richness > 0.1%) or genus (richness > 1%) composition between the CON and EXP groups (P > 0.05). A tendency of difference was found between CON and EXP (R = 0.22, P = 0.098) in principal component analysis. Ten genera showed different abundances across the CON and EXP groups (linear discriminant analysis effect size, linear discriminant analysis > 2). EXP increased the ratio of albumin to globulin and the concentrations of total cholesterol and low-density lipoprotein cholesterol (P < 0.05) and tended to increase triglycerides (P = 0.09) in blood. Milk yield, 3.5% fat-corrected milk yield and energy-corrected milk yield increased with enzyme supplementation (P < 0.05). The production levels of milk fat and lactose increased, but the percentage of solids, not fat and protein, decreased in EXP (P < 0.05). Although the DM intake was not affected, the feed efficiency tended to increase (P = 0.07) in EXP. In conclusion, dietary supplementation with a mixture of fibrolytic and amylolytic enzymes on multiparous early-lactation dairy cows increased α-amylase and xylanase activity levels in rumen fluid, enhanced milk performance and tended to improve the feed efficiency in cows.     

Short-term physiological responses to moderate heat stress in grazing dairy cows in temperate climate

Even in temperate climate regions, an increase in ambient temperature and exposure to solar radiation can cause heat stress in lactating dairy cows. We hypothesised that grazing dairy cows exhibit short-term physiological changes due to increasing heat load under moderate climate conditions. Over two consecutive summers, 38 lactating Holstein dairy cows were studied in a full-time grazing system. Data were collected in 10 experimental periods of up to three consecutive days with a moderate comprehensive climate index (CCI). The individual animals’ vaginal temperature (VT), heart rate, and locomotor activity data were automatically monitored with sensors. Blood samples and proportional whole milk samples were collected at afternoon milking. The concentrations of beta-hydroxybutyrate, glucose, non-esterified fatty acids, urea nitrogen, plasma thyroxine and triiodothyronine were analysed in blood plasma, and fat, protein, lactose, urea nitrogen, cortisol, Na⁺, K⁺, and Cl^? concentrations were analysed in milk. The daily distribution of VT recordings greater than 39 °C showed a circadian rhythm with a proportion of recordings of 2% and lower during the night and a percentage of 10% or higher in the afternoon. The cows’ maximal daily vaginal temperature (VT_MAX) between 0830 and 1430 h was positively related to the mean daily CCI in the same time period (CCI_MEAN; mean and SD 23.6 ± 5.4 °C). Cows with greater VT_MAX had an increased mean heart rate, plasma glucose and milk cortisol concentrations and decreased concentrations of plasma thyroxine and triiodothyronine. The concentration of Na⁺ in milk was lower, and the concentration of K⁺ in milk tended to be higher in cows with increased VT_MAX. For beta-hydroxybutyrate, non-esterified fatty acids and urea nitrogen concentrations in plasma and fat and lactose concentrations in milk no relationships were found in terms of increasing VT. For milk urea nitrogen and protein concentrations, the proportion of total variance explained by inter-individual or -period variance was high. In conclusion, changes observed in milk and blood likely reflected short-term physiological responses to moderate heat stress. In particular, milk cortisol and Na⁺ may be useful traits for timely monitoring of heat stress in individual cows because their inter-individual variances were relatively small and samples can be collected non-invasively.     

Comparison of sheep and dairy cows for in vivo digestibility of perennial ryegrass

Sheep are often used as a proxy for dairy cows when measuring the digestibility of a feed. In recent years grassland management guidelines for ruminant animals have been re-evaluated in accordance with the progression in animal genetics and the acknowledgement that genetic potential has an influence on both feed intake and digestibility. Recommended pre-grazing herbage mass (HM) targets are now much lower with improved perennial ryegrass varieties available for grazing swards. The objective of this study was to compare the in vivo digestibility of perennial ryegrass in wether sheep and lactating dairy cows. The experimental design was selected to measure the effect of animal species (cows, sheep), sward HM measured cutting herbage at 4 cm above ground level (low: 1 700 kg DM/ha and high: 4 000 kg DM/ha) and season (Spring: Apr–May, Summer: Jul–Aug) on the digestibility of perennial ryegrass. Each HM treatment was offered to each animal within species and season for 12 d using a 2 HM × 2 period changeover Latin square design. There were eight cows and eight sheep, so there were four 2 × 2 Latin squares for each animal species (two) at each season (two), giving 64 observations. During each 12 d experimental period, the first 6 d were used for adaptation (adaptation phase) and the final 6 d were used for measurement (measurement phase). In vivo organic matter digestibility (OMD) in spring did not differ between animal species but in summer sheep had higher in vivo OMD than cows. The results described herein highlight the suitability of wether sheep as an alternative to dairy cows for determining the digestibility of perennial ryegrass in spring but not in summer. Stage of growth of the plant, which is intrinsically linked to season, should be considered as results show that digestibility in the ruminant was affected by season but not differentially affected by changing sward HM.     

Effects of medium-chain fatty acid supplementation on performance and rumen fermentation of lactating Holstein dairy cows

Medium-chain fatty acids (MCFAs) have antimicrobial properties and cause negative or positive effects on animal performance depending on its dosage. We hypothesized that MCFA supplementation at a lower dose (i.e., 0.05–0.2% of dietary DM) would increase rumen pH and milk production without decreasing nutrient digestibility which is typically observed with the higher inclusion rates (i.e., >1% of dietary DM). The objective of this study was to evaluate the effects of MCFA supplementation at a lower dose on productivity, plasma energy metabolite concentrations, apparent total tract nutrient digestibility, rumen fermentation, and rumen microbial profile of lactating dairy cows. Thirty (n = 8 primiparous, n = 22 multiparous) Holstein cows in mid-lactation (637 ± 68.5 kg of initial BW, 98.5 ± 27.4 d in milk; mean ± standard deviation) were used in a crossover design with two 28-d periods. The MCFA supplement, consisted of 25% MCFA (containing 32% C8:0, 21% C10:0, 47% C12:0 on DM basis) and 75% carrier ingredients, was fed at 0.25% of dietary DM replacing dry ground corn in control (CON). Total inclusion of MCFA was 0.063% of dietary DM. No differences were observed in DM intake, apparent total tract nutrient digestibility and BW change between MCFA and CON. Milk and milk component yields did not differ between treatment groups. The MCFA supplementation tended to have higher minimum rumen pH (5.66 vs. 5.54), and decreased daily fluctuation range of rumen pH (1.17 vs. 1.40) compared to CON. However, the duration of acidosis (pH < 5.8, min/d) did not differ between treatment groups and ruminal total volatile fatty acid concentration and its profile did not differ between treatment groups. For rumen microbiota, the Chao1 index of bacterial community tended to be lower (10.9 vs. 11.6) whereas the Shannon index did not differ (0.91 vs. 0.93) in MCFA compared to CON, and both indices did not differ for archaeal and protozoan communities between treatment groups. The relative abundance of Methanobrevibacter gottschalkii increased when supplemented with MCFA (5.14 vs. 4.92%). These results suggest that supplementation of MCFA at 0.063% dietary DM may not affect overall animal performance or total tract nutrient digestibility, but decrease the daily range of pH and the bacterial richness in the rumen.     

Odd- and branched-chain fatty acids in milk fat from Holstein dairy cows are influenced by physiological factors

Dairy products are the major source of odd- and branched-chain fatty acids (OBCFAs), a group of nutrients with emerging health benefits. The animal diet is known to influence milk fat OBCFAs of dairy cows; however, little is known about the effects of physiological factors. The objective of this study was to investigate the effects of parity and lactation stage on OBCFAs in milk fat of dairy cows. Holstein dairy cows (n = 157) were selected according to parity (first, second, third, or greater) and days in milk (DIM) (≤21 DIM, 21 < DIM ≤ 100, 100 < DIM ≤ 200, >200 DIM). All cows were fed the same total mixed ration for three weeks. Milk samples were collected during the last three days of each lactation stage for fatty acid (FA) analyses via gas chromatography. Results showed that first- and second-parity cows displayed significantly higher proportions and yields of iso-14:0, iso-15:0, iso-16:0, total iso-FA, and total branched-chain FA (P < 0.05) compared with other parities. The proportions of C17:0 and C17:1 cis-9 were also greater in first-parity cows (P < 0.05), while the yields of C17:0 and C17:1 cis-9 were similar among different parities (P > 0.05). The proportions of total OBCFAs were greater in first- and second-parity cows (P < 0.05), whereas the highest yield was observed in second-parity cows. Lactation dairy cows in ≤ 21 DIM group displayed lower proportions of iso-13:0, anteiso-13:0, C13:0, iso-14:0, C15:0, iso-16:0, total iso-FA, and total OBCFAs compared with that of the other groups (P < 0.05), and also lower yields of iso-14:0 and iso-16:0 (P < 0.05). In contrast, C17:0 and C17:1 cis-9 proportions and yields were higher in dairy cows with ≤ 21 DIM (P < 0.05). Iso-17:0 and anteiso-17:0 were not affected by lactation stage (P > 0.05). Taken together, our data showed that both parity and lactation stage have considerable effects on milk fat OBCFAs of dairy cows. In summary, first- and second-parity cows had higher milk OBCFAs compared with later parity cows, and OBCFAs with medium chain lengths were lower in dairy cows with ≤ 21 DIM, while C17:0 and C17:1 cis-9 were higher. These findings show that milk OBCFA contents are differentially modulated by physiological state. They will be useful in future studies that seek to alter OBCFA composition of Holstein dairy cow milk fats.     

Comparison of fertility,regular returns-to-estrus,and calving interval between Ovsynch and CO-synch + CIDR protocols in dairy cows

The main aims of the present study were to compare the pregnancy rate (PR), regular returns-to-estrus, and calving interval of a CO-Synch + controlled internal drug release (CIDR) device, commonly used to synchronize ovulations in beef cows, with the classical Ovsynch protocol in high-producing dairy cows. Holstein-Friesian cows (n = 128) from six commercial dairy herds, ≥40 days postpartum and not previously inseminated, were randomly assigned to one of two treatments. Cows submitted to Ovsynch protocol (group OS as control group; n = 66) received 10 μg of a GnRH analogue 7 days before and 48 hours after 25 mg PGF_2α, followed by artificial insemination (AI) 16 hours after the second GnRH administration. Cows submitted to CO-Synch + CIDR (1.38 g of progesterone) inserted for 7 days beginning at the first GnRH administration (group CoS + CD; n = 62) had the second administration of GnRH concurrent with AI, 64 hours after CIDR removal/PGF_2α administration. Nonpregnant cows with return-to-estrus between 18 and 24 days after first AI were reinseminated (second AI). Logistic regressions were used to analyze PR and returns-to-estrus. No effect of group or herd was observed in PR at first timed AI. However, the sum of cows pregnant at first AI and nonpregnant cows with regular returns-to-estrus and the total PR (first + second AI) were influenced by group treatment. Overall, cows of group CoS + CD (total PR = 56.5%) were 2.1 times more likely to became pregnant after AI and until first regular returns-to-estrus than cows of group OS. The calving interval was lower in group CoS + CD (425.9 ± 78.8 days; ±SD) than in group OS (475.3 ± 83.7 days). The CO-Synch + CIDR protocol was reliable to use in dairy herds and provided reproductive advantages when compared with Ovsynch protocol.     

Variation of immunoglobulins G,A, and M and bovine serum albumin concentration in Holstein cow colostrum

Immunoglobulins G (IgG), A (IgA), and M (IgM) represent 70–80% of total proteins in cattle colostrum and are essential for the passive transfer of antibodies from the dam to the calf. Considering the practical difficulties of colostrum sample collection and the high cost of analysis, non-genetic sources of variation of the three immunoglobulins fractions have been scarcely studied together on a large scale in dairy cows. In the present study, IgG, IgA, IgM, and bovine serum albumin (BSA) were determined in colostrum samples of Holstein cows through bovine-specific radial immunodiffusion kits; such phenotypes allowed to investigate the effects of parity, herd, and calving season, and interactions. Only the first colostrum was considered in the present study, as the calf was separated from the dam immediately after birth and was not allowed to suckle. The average of IgG (n = 676), IgA (n = 573), IgM (n = 658), total immunoglobulins (n = 525), and BSA (n = 614) was 91.31, 4.20, 105.99, 5.05, and 2.47 g/L, respectively, and all traits positively correlated to each other. Overall, the immunoglobulins were less concentrated in colostrum of first- and second-parity cows than later-parity cows. These findings suggest that colostrum quality, based on Ig, is overall greater in cows that experienced more than two lactations, likely due to a greater experience of the immune system and to a wider immune heritage compared to younger cows. As regards the effect of calving season, the concentration of all Ig tended to be generally greater in colostrum sampled from August to November. Moreover, there were differences in IgG, IgA, and IgM concentration among the nine herds involved. Future studies will investigate the relationships of these traits with yield, and gross and detailed composition of bovine colostrum and will consider their genetic background to evaluate potential selection strategies to improve colostrum quality.     

Evaluation of nitrogen excretion equations for ryegrass pasture-fed dairy cows

Accurate and precise estimates of nitrogen (N) excretion in faeces and urine of dairy cattle may provide direct tools to improve N management and thus, to mitigate environmental pollution from dairy production. Empirical equations of N excretion have been evaluated for indoor dairy cattle but there is no evaluation for cows fed high proportions of fresh forage. Therefore, the objective of the current study was to evaluate N excretion equations with a unique data set of zero-grazing experiments. Through literature searches, 89 predictive equations were identified from 13 studies. An independent data set was developed from seven zero-grazing experiments with, in total, 55 dairy Holstein-Friesian cows. Models’ performance was evaluated with statistics derived from a mixed-effect model and a simple regression analysis model. Squared sample correlation coefficients were used as indicators of precision and based on either the best linear unbiased predictions (R²_BLUP) or model-predicted estimates (R²_MDP) derived from the mixed model and simple regression analysis, respectively. The slope (β₀), the intercept (β₁) and the root mean square prediction error (RMSPE_m%) were calculated with the mixed-effect model and used to assess accuracy. The root mean square prediction error (RMSPE_sr%) and the decomposition of the mean square prediction error were calculated with the simple regression analysis and were used to estimate the error due to central tendency (mean bias), regression (systematic bias), and random variation. Concordance correlation coefficient (CCC) were also calculated with the simple regression analysis model and were used to simultaneously assess accuracy and precision. Considering both analysis models, results suggested that urinary N excretion (UN; R²_MDP = 0.76, R²_BLUP = 0.89, RMSPE_m% = 17.2, CCC = 0.82), total manure N excretion (ManN; R²_MDP = 0.83, R²_BLUP = 0.90, RMSPE_m% = 11.0, CCC = 0.84) and N apparently digested (NAD; R²_MDP = 0.97, R²_BLUP = 0.97, RMSPE_m% = 5.3, CCC = 0.95) were closely related to N intake. Milk N secretion was better predicted using milk yield as a single independent variable (MilkN; R²_MDP = 0.77, R²_BLUP = 0.97, RMSPE_m% = 6.0, CCC = 0.74). Additionally, DM intake was a good predictor of UN and ManN and dietary CP concentration of UN and ManN. Consequently, results suggest that several evaluated empirical equations can be used to make accurate and precise predictions concerning N excretion from dairy cows being fed on fresh forage.     

Milk fatty acids as indicators of negative energy balance of dairy cows in early lactation

Most dairy cows experience negative energy balance (NEB) in early lactation because energy demand for milk synthesis is not met by energy intake. Excessive NEB may lead to metabolic disorders and impaired fertility. To optimize herd management, it is useful to detect cows in NEB in early lactation, but direct calculation of NEB is not feasible in commercial herds. Alternative methods rely on fat-to-protein ratio in milk or on concentrations of non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHB) in blood. Here, we considered methods to assess energy balance (EB) of dairy cows based on the fatty acid (FA) composition in milk. Short- and medium-chain FAs (primarily, C14:0) are typically synthesized de novo in the mammary gland and their proportions in milk fat decrease during NEB. Long-chain FAs C18:0 and C18:1 cis-9 are typically released from body fat depots during NEB, and their proportions increase. In this study, these FAs were routinely determined by Fourier-transform infrared spectroscopy (FTIR) of individual milk samples. We performed an experiment on 85 dairy cows in early lactation, fed the same concentrate ration of up to 5 kg per day and forage ad libitum. Daily milk yield and feed intake were automatically recorded. During lactation weeks 2, 4, and 6 after calving, two milk samples were collected for FTIR spectroscopy, Tuesday evening and Wednesday morning, blood plasma samples were collected Thursday morning. Net energy content in feed and net energy required for maintenance and lactation were estimated to derive EB, which was used to compare alternative indicators of severe NEB. Linear univariate models for EB based on NEFA concentration (deviance explained = 0.13) and other metabolites in blood plasma were outperformed by models based on concentrations of metabolites in milk: fat (0.27), fat-to-protein ratio (0.18), BHB (0.20), and especially C18:0 (0.28) and C18:1 cis-9 (0.39). Analysis of generalized additive models (GAM) revealed that models based on milk variables performed better than those based on blood plasma (deviance explained 0.46 vs. 0.21). C18:0 and C18:1 cis-9 also performed better in severe NEB prediction for EB cut-off values ranging from −50 to 0 MJ NEL/d. Overall, concentrations of C18:0 and C18:1 cis-9 in milk, milk fat, and milk BHB were the best variables for early detection of cows in severe NEB. Thus, milk FA concentrations in whole milk can be useful to identify NEB in early-lactation cows.     

Potential of a rumen bolus containing 1,25-dihydroxyvitamin D3 glycosides for the prevention of hypocalcaemia in primiparous and multiparous dairy cows

Periparturient hypocalcaemia is a widespread metabolic disorder in dairy cows. Clinical and subclinical cases occur primarily in multiparous (Multi) cows, but subclinical cases have also been reported in primiparous (Primi) cows. A preventive strategy was investigated by administering the physiologically active vitamin D₃ metabolite, 1,25-dihydroxyvitamin D₃ (1,25-dihydroxycholecalciferol, 1,25(OH)₂D₃) as a rumen bolus. The bolus contained tablets of 1,25(OH)₂D₃ glycoside extract from Solanum glaucophyllum (SGE), releasing SGE over several days. The aim was to study the effect of a bolus containing 0 (C) or 500 µg (SGE) of 1,25(OH)₂D₃ on 1,25(OH)₂D₃ and mineral status in periparturient cows up to three weeks into lactation and on colostrum, milk and calves’ blood mineral contents. The bolus was administered three to four days prior to expected calving to Primi and Multi cows fed a herbage-based diet (dietary cation-anion difference of +522 mEq/kg DM). One C or SGE bolus was applied to 12 Primi and 12 Multi cows. Blood was regularly sampled (and selected a posteriori for antepartum samples) in regard to the actual calving day (d0), immediately prior to bolus application and at day ?2, 0.5, 1, 1.5, 2, 4, 8, 11, 15, 18 and 22. Additional samples included urine (at bolus application, d0.5 and d2), colostrum, milk samples (weekly) and calves’ blood (d2). Blood serum 1,25(OH)₂D₃ increased between d0.5 and d2 in Primi-SGE, but remained unchanged in Primi-C, as did parathyroid hormone (PTH) and Ca in all Primi. Urinary Ca of Primi-SGE was increased on d2, indicating regulation of Ca excess. Three Multi-C cows with confirmed clinical hypocalcaemia needed treatment and thus were excluded from the dataset and replaced. Blood serum 1,25(OH)₂D₃ and PTH increased while Ca dropped by 40% between d0.5 and d2 in Multi-C, whereas 1,25(OH)₂D₃, Ca and PTH remained unchanged in Multi-SGE. Blood serum carboxyterminal telopeptide of type I collagen was higher in Primi than in Multi and increased with time, except in Primi-C. Mineral contents in colostrum, milk and blood serum of calves were not influenced to a relevant degree. In conclusion, Primi-C did not, in contrast to Multi-C, develop subclinical hypocalcaemia (<2.0 mmol Ca/l). Prevention of hypocalcaemia with one SGE bolus applied three to four days prior to expected calving was successful in maintaining blood Ca within normal range in Multi over the critical first two days and up to the first three weeks of lactation, without any observed detrimental effects on cows or calves.     

Flaxseed supplementation decreases methanogenic gene abundance in the rumen of dairy cows

The objective of this study was to investigate the effects of a flaxseed-supplemented diet on archaeal abundance and gene expression of methanogens in the rumen of dairy cows. In all, 11 non-lactating dairy cows were randomly divided into two groups: group A (five cows) and B (six cows). The two diets fed were: (1) the control diet, a conventional dry cow ration; and (2) the flaxseed-supplemented diet, the conventional dry cow ration adjusted with 12.16% ground flaxseed incorporated into the total mixed ration. A cross-over experiment was performed with the two groups of cows fed the two different diets for five 21-day periods, which included the first adaptation period followed by two treatment and two wash out periods. At the end of each feeding period, rumen fluid samples were collected via rumenocentesis and DNA was extracted. Quantitative PCR was utilized to analyze the gene abundance of 16S ribosomal RNA (16S rRNA) targeting the ruminal archaea population and the mcrA gene coding for methyl coenzyme-M reductase subunit A, a terminal enzyme in the methanogenesis pathway. Results demonstrated a 49% reduction of 16S rRNA and 50% reduction of mcrA gene abundances in the rumen of dairy cows fed the flaxseed-supplemented diet in comparison with those fed the control diet. This shows flaxseed supplementation effectively decreases the methanogenic population in the rumen. Future studies will focus on the mechanisms for such reduction in the rumen of dairy cattle, as well as the relationship between methanogenic gene expression and methane production.