A 2-year study reveals implications of feeding management and exposure to mycotoxins on udder health, performance, and fertility in dairy herds.

We recently reported the ubiquitous occurrence of mycotoxins and their secondary metabolites in dairy rations and a substantial variation in the feeding management among Austrian dairy farms. The present study aimed to characterize to which extent these factors contribute to the fertility, udder health traits, and performance of dairy herds. During 2019 and 2020, we surveyed 100 dairy farms, visiting each farm 2 times and collecting data and feed samples. Data collection involved information on the main feed ingredients, nutrient composition, and the levels of mycotoxin and other metabolites in the diet. The annual fertility and milk data of the herds were obtained from the national reporting agency. Calving interval was the target criterion for fertility performance, whereas the percentage of primiparous and multiparous cows in the herd with somatic cell counts above 200,000 cells/mL was the criterion for impaired udder health. For each criterion, herds were classified into 3 groups: high/long, mid, and low/short, with the cut-off corresponding to the <25th and >75th percentiles and the rest of the data, respectively. Accordingly, for the calving interval, the cut-offs for the long and short groups were ≥400 and ≤380 d, for the udder health in primiparous cows were ≥20% and ≤8% of the herd, and for the udder health in multiparous cows were ≥35% and ≤20% of the herd, respectively. Quantitative approaches were further performed to define potential risk factors in the herds. The high somatic cell count group had higher dietary exposure to enniatins (2.8 vs. 1.62 mg/cow per d), deoxynivalenol (4.91 vs. 2.3 mg/cow per d), culmorin (9.48 vs. 5.72 mg/cow per d), beauvericin (0.32 vs. 0.18 mg/cow per d), and siccanol (13.3 vs. 5.15 mg/cow per d), and total Fusarium metabolites (42.8 vs. 23.2 mg/cow per d) and used more corn silage in the ration (26.9% vs. 17.3% diet DM) compared with the low counterparts. Beauvericin was the most substantial contributing variable among the Fusarium metabolites, as indicated by logistic regression and modeling analyses. Logistic analysis indicated that herds with high proportions of cows with milk fat-to-protein ratio >1.5 had an increased odds for a longer calving interval, which was found to be significant for primiparous cows (odds ratio = 5.5, 95% confidence interval = 1.65-21.7). As well, herds with high proportions of multiparous cows showing levels of milk urea nitrogen >30 mg/dL had an increased odds for longer calving intervals (odds ratio = 2.96, 95% confidence interval = 1.22-7.87). In conclusion, the present findings suggest that dietary contamination of Fusarium mycotoxins (especially emerging ones), likely due to increased use of corn silage in the diet, seems to be a risk factor for impairing the udder health of primiparous cows. Mismatching dietary energy and protein supply of multiparous cows contributed to reduced herd fertility performance.

Effect of reproductive management programs that prioritized artificial insemination at detected estrus or timed artificial insemination on the economic performance of primiparous Holstein cows of different genetic merit for fertility.

The objective of this randomized controlled experiment was to evaluate the effect of reproductive management programs that prioritized artificial insemination (AI) at detected estrus (AIE) or timed AI (TAI) during the first lactation on the economic performance of dairy cows of different genomically enhanced predicted transmitting ability for fertility. Lactating primiparous Holstein cows from 6 commercial farms were stratified into high, medium, and low fertility groups based on a reproduction index value calculated from multiple genomically enhanced predicted transmitting abilities to predict the number of days to achieve pregnancy. Within herd and fertility group, cows were randomly assigned either to a program that prioritized AIE (P-AIE; n = 1,416) and used TAI for cows not AIE for all AI services or another that prioritized TAI and had an extended voluntary waiting period for first service and prioritized TAI for second and greater AI services (P-TAI; n = 1,338). Cash flow (CF) per cow accumulated for the experimental (first) and second calving interval (CIN) and cash flow per slot per 28 mo after calving in the experimental lactation were calculated. Market and rearing heifer cost values were used for estimating CF. For cows in the high fertility group, a positive effect of delayed pregnancy on milk income during the first lactation was observed (+$248 for P-TAI) but was insufficient to generate significant differences in CF between treatments mainly because of milk income compensation in the second lactation (+$125 for P-AIE) and minor reductions in reproductive cost and gains in calf value for the P-AIE treatment. In this regard, CF for 2 CIN was greater for the P-TAI treatment by $61 and $86 for market and rearing replacement heifer cost, respectively. Similarly, CF per slot was favorable to the P-TAI treatment but only by $13 and $47 for market and rearing replacement heifer cost, respectively. For cows in the low fertility group, CF was numerically in favor of the P-AIE treatment due to a pregnancy and herd exit dynamics that resulted in gains in milk income over feed cost during the first ($29) and second ($113) lactation. Differences in CF for the 2 CIN were $58 and $47 for market or rearing heifer value, respectively, and $77 and $19 for market and rearing heifer values, respectively for the slot analysis. Differences in CF between cows of different genetic merit for fertility were consistent across treatment and estimation method. Of note, cows in the low fertility group had greater CF than cows in the high fertility group in all comparisons, ranging from $198 per cow for 2 CIN to as much as $427 per slot. For the low fertility group, greater milk production contributed directly (milk income over feed cost) and indirectly (reduced culling) to increased CF. We concluded that genetic merit for fertility and CF are associated because cows of inferior genetic potential for fertility had greater CF than cows of superior genetic for fertility despite some increased costs and reduced revenues. Also, the magnitude of the CF differences observed for cows of different genetic merit for fertility managed with the P-AIE or P-TAI program may be valuable to commercial dairy farms but did not allow to conclusively support the choice of a type of reproductive management strategy for cows of different genetic merit for fertility.

Performance of dairy cows fed diets formulated at 2 starch concentrations with either canola meal or soybean meal as the protein supplement.

This study was designed to evaluate the effects of substituting corn grain with nonforage fiber sources in diets containing soybean meal (SBM) or canola meal (CM) as the primary protein source. Sixteen Holstein cows were assigned to a replicated 4 × 4 Latin square design with 4 periods of 28 d each. Treatments were arranged as a 2 × 2 factorial with 2 protein sources (SBM and CM) and 2 dietary starch concentrations (21 and 27% dry matter, DM). Diets were formulated to contain 16.5% CP, and the 21% starch diets were obtained by replacing corn grain with soybean hulls and beet pulp. Protein source × starch interactions were observed for DM intake (DMI), milk fat and protein concentrations, milk protein yield, milk urea nitrogen, and feed efficiency. Cows fed CM diets had a higher DMI when dietary starch concentration was 27% compared with 21%, but those cows had DMI similar to that of cows on SBM diets regardless of the starch concentration. Milk fat percentage was decreased in cows fed CM with 27% starch compared with cows fed CM with 21% starch and cows fed SBM with 27% starch. Milk protein percentage and yield and milk lactose percentage were least in cows fed CM with 21% starch compared with the other 3 diets, but feed efficiency was greater for cows fed CM with 21% starch. Milk urea nitrogen was least in cows fed CM with 27% starch compared with the other 3 diets. Cows fed diets with 27% starch produced 2.5 kg/d more milk and 1.9 kg/d more energy-corrected milk compared with cows fed 21% starch. Digestibility of DM and organic matter was higher in cows fed SBM diets than in cows on CM diets, and cows fed 27% starch showed greater DM and organic matter digestibility than cows on 21% starch. Digestibility of neutral detergent fiber and acid detergent fiber was greater in diets with SBM than in those with CM. Molar proportion of acetate was the lowest for cows fed CM with 21% starch compared with cows fed SBM with 21% starch, with the remaining cows fed being intermediate and similar. However, propionate was highest for cows fed CM with 21% starch than for cows fed SBM with 21% starch, but the remaining treatments were intermediate and similar. Isobutyrate was greater for cows fed CM with 21% starch, which resulted in the lowest acetate:propionate ratio compared with cows fed the remaining treatments. Overall, we confirmed that the interaction of protein with starch in CM diets can sustain similar cow performance as with the SBM diets. Those making decisions about starch concentration and protein source should consider feed price when SBM or CM and different starch levels are being formulated in diets for lactating dairy cows.

Associations of Neonatal Dairy Calf Faecal Microbiota with Inflammatory Markers and Future Performance.

After birth, the immune system is challenged by numerous elements of the extrauterine environment, reflected in fluctuations of inflammatory markers. The concentrations of these markers in the first month of life are associated with the future performance of dairy youngstock. It is thought that bacterial genera colonizing the calf intestinal tract can cause inflammation and thus affect their host's performance via immunomodulation. This study explored how the faecal microbiota of newborn dairy calves were related to inflammatory markers during the first three weeks of life, and if the abundance of specific genera was associated with first-lactation performance. Ninety-five female Holstein calves were studied. Once a week, serum and faecal samples were collected, serum concentrations of serum amyloid A, haptoglobin, tumour necrosis factor-α, and interleukin-6 were measured, and faecal microbiota composition was examined by 16S rRNA gene amplicon sequencing. Faecal Gallibacterium abundance in the first week of age and Collinsella abundance in the second week were negatively associated with inflammatory response as well as with calving-conception interval. Peptostreptococcus abundance in the second week of life was positively associated with inflammatory response and calving-conception interval, and negatively with average daily weight gain. In the third week, Dorea abundance was positively, Bilophila abundance was negatively associated with inflammatory response, and both genera were negatively associated with age at first calving. These bacterial genera may be able to influence the inflammatory response and through this, possibly the future performance of the dairy heifer. Deciphering such microbiota-host interactions can help improve calf management to benefit production and welfare.

Dietary Live Yeast Supplementation Influence on Cow's Milk, Teat and Bedding Microbiota in a Grass-Diet Dairy System.

The supplementation of animal feed with microbial additives remains questioning for the traditional or quality label raw milk cheeses with regard to microbial transfer to milk. We evaluated the effect of dietary administration of live yeast on performance and microbiota of raw milk, teat skin, and bedding material of dairy cows. Two balanced groups of cows (21 primiparous 114 ± 24 DIM, 18 multiparous 115 ± 33 DIM) received either a concentrate supplemented with Saccharomyces cerevisiae CNCM I-1077 (1 × 1010 CFU/d) during four months (LY group) or no live yeast (C group). The microbiota in individual milk samples, teat skins, and bedding material were analysed using culture dependent techniques and high-throughput amplicon sequencing. The live yeast supplementation showed a numerical increase on body weight over the experiment and there was a tendency for higher milk yield for LY group. A sequence with 100% identity to that of the live yeast was sporadically found in fungal amplicon datasets of teat skin and bedding material but never detected in milk samples. The bedding material and teat skin from LY group presented a higher abundance of Pichia kudriavzevii reaching 53% (p < 0.05) and 10% (p < 0.05) respectively. A significant proportion of bacterial and fungal ASVs shared between the teat skin and the milk of the corresponding individual was highlighted.

Investigation of dairy cow performance in different udder health groups defined based on a combination of somatic cell count and differential somatic cell count.

Mastitis is still the costliest disease in milk production. In particular, its subclinical form, which may spread unnoticeably within a herd, is a major challenge. Somatic cell count (SCC) is broadly used as an indicator for mastitis and thus the basis for udder health management programmes, e.g. through dairy herd improvement (DHI) testing. Since recently, differential somatic cell count (DSCC, representing the combined proportion of polymorphonuclear neutrophils and lymphocytes as a percentage of total SCC) is available in addition. Our study was aimed to investigate dairy cow performance in four newly defined udder health groups (UHG) based on SCC and DSCC results from DHI testing. In total, 961,835 test-day results generated in Austria, China, Estonia, Germany, and Spain between January 2019 and March 2020 were available for data analyses. Cows were categorised into four UHG depending on test day SCC and DSCC results (UHG A: healthy/normal, ≤200,000 cells/mL and ≤65 %; B: suspicious, ≤200,000 cells/mL and >65 %; C: mastitis, >200,000 cells/mL and >65 %; D: chronic/persistent mastitis, >200,000 cells/mL and ≤65 %). Linear mixed effect models were used to compare the performance of cows between the UHG based on the parameters milk weight, energy-corrected milk, fat, protein, lactose, and estimated milk value. Highest performance was found for cows in UHG A and ranged between 21.4 (Austria) and 38.3 kg per cow and day (Spain). Interestingly, cows in group B were significantly less productive (0.9-2.4% less daily milk production) compared to those in group A. Cows in groups C (6.0-9.8% less daily production compared to group A) and D were, as expected, even less productive with a particularly significant drop for cows in group D (17.5-38.5% less daily production). These trends could be observed in all countries involved in this study. Proportions of cows in the four different UHG differed between countries, changed slightly within countries depending on season, differed depending on parity and days in milk, and were seen to vary hugely between herds. In conclusion, this study demonstrates changes in performance of dairy cows depending on their udder health status as defined based on the combination of SCC and DSCC. In particular cows in UHG B and D are of interest as they cannot be identified working with SCC only. Nevertheless, the actual udder health management measures that could be taken based on the new UHG still require further investigation.