Cooling management effects on dry matter intake, metabolic hormones levels and welfare parameters in dairy cows during heat stress.

This research paper addresses the hypothesis that intensive cooling management during the summer improves the secretion of metabolic hormones in dairy cows. To test this hypothesis, we characterized the effect of different cooling managements on the different ghrelin isoforms and leptin secretion of 20 Israeli-Holstein dairy cows during 5 weeks during heat stress. The cows were divided into two groups: one was exposed to 5 cooling sessions per day (5 CS) and the other to 8 cooling sessions per day (8 CS). Blood was collected and leptin and ghrelin isoforms level were radioimmunoassayed. Analysis of the interaction between coolings and the week of the experiment showed that the 8 CS group consumed more food and produced more milk, although neither difference was statistically significant. In addition, the 8 CS group exhibited higher blood levels of acyl-ghrelin and leptin as compared to the 5 CS group. Conversely, the blood levels of total ghrelin were lower in the cows exposed to 8 CS as compared to cows from the 5 CS treatment. Furthermore, a significant correlation was found only between total ghrelin levels and the weeks, but not with other parameters examined. We further compared digestibility as well as stress parameters between the groups. We found that the 8 CS group cows ruminated and lay down more hours during a day and simultaneously had better activity time. No significant difference was detected between groups in milk yield and digestibility parameters. Our results suggest that intensive cooling management during the hot season influences the levels of metabolic hormones in the circulation and helps to mitigate the detrimental effect of heat stress on dairy cow welfare and production.

FABP4 gene has a very large effect on feed efficiency in lactating Israeli Holstein cows.

Improving feed efficiency (FE) is a major goal for the livestock industry. Previously, we have identified 48 SNP markers distributed over 32 genes significantly associated with residual feed intake (RFI) in Israeli Holstein male calves, the most significant of which are located in the bovine FABP4 gene. In the present study, we tested associations of eight of the FABP4 markers with RFI and feed conversion ratio (FCR), along with milk composition and feeding behavioral traits, in 114 lactating Israeli Holstein cows. Large allele effects were found, along with large contributions of FABP4 markers to the phenotypic variation [mean contribution of all significant markers (P < 0.05), 15.4 and 12.0% for RFI and FCR, respectively] and genotypic variation [means of all significant markers (P < 0.05), 75.7 and 32.4% in RFI and FCR, respectively]. However, the association of all significant FABP4 markers with FE and milk content traits was found in opposite directions, such that improved FE was accompanied by decreased milk content. Hence, before inclusion in breeding programs, the gain in FE must be economically balanced with the loss in milk contents. On the other hand, these findings imply that in any current improvement program concentrated on milk traits alone, without taking into account the effect on FE, the progress in milk composition is probably accompanied by deterioration of FE. These results, if confirmed in other populations and breeds, set FABP4 as a prime candidate in any marker-assisted selection program targeting FE as a whole and RFI in particular.

Effect of feeding ensiled mixture of pomegranate pulp and drier feeds on digestibility and milk performance in dairy cows.

Based on a previous ensiling study in glass silos of various pomegranate pulp (PP) mixtures, fresh pomegranate pulp (PP) was mixed with drier feeds including soy hulls and corn silage (40:35:25 on DM basis) and ensiled in 32 pressed bales (700 kg each) wrapped with stretch polyethylene film. This ensiled pomegranate pulp mixture (PPM) was included in lactating cow total mixed ration (TMR) at a level of 20% of DM (PPM-TMR). Performance and digestion experiment was conducted with two groups of 21 milking cows each, fed individually one of the two TMR: 1. Control TMR without ensiled PPM; 2. Experimental TMR which contained 20% ensiled PPM, including 8% PP as corn grain replacer. Voluntary DM intake of cows fed the control TMR was 5.04% higher than that of the PPM cows. In vivo digestibility of DM, OM, NDF, CP and fat were significantly higher in the control cows compared with the PPM group, but methane production in the rumen fluid was 25% lower in the PPM cows. A slightly higher milk yield (by 2.2%) observed in the control cows; however, milk fat content was 5.9% higher in the PPM cows. This was reflected in similar yield of energy corrected milk (ECM) and 3.97% increase in production efficiency (ECM/DM intake) of the PPM cows compared with the control ones. Welfare of the cows, as assessed by length of daily recumbence time, was in the normal range for both groups. Body weight gain was also similar in both groups. Data suggest that the level of 8% PP in the PPM-TMR used in this study was probably too high for lactating cows and should be lowered to 4% in order to achieve better performance.

Re-Evaluation of Genotyping Methodologies in Cattle: The Proficiency of Imputation.

In dairy cattle, identifying polymorphisms that contribute to complex economical traits such as residual feed intake (RFI) is challenging and demands accurate genotyping. In this study, we compared imputed genotypes (n = 192 cows) to those obtained using the TaqMan and high-resolution melting (HRM) methods (n = 114 cows), for mutations in the FABP4 gene that had been suggested to have a large effect on RFI. Combining the whole genome sequence (n = 19 bulls) and the cows' BovineHD BeadChip allowed imputing genotypes for these mutations that were verified by Sanger sequencing, whereas, an error rate of 11.6% and 10.7% were encountered for HRM and TaqMan, respectively. We show that this error rate seriously affected the linkage-disequilibrium analysis that supported this gene candidacy over other BTA14 gene candidates. Thus, imputation produced superior genotypes and should also be regarded as a method of choice to validate the reliability of the genotypes obtained by other methodologies that are prone to genotyping errors due to technical conditions. These results support the view that RFI is a complex trait and that searching for the causative sequence variation underlying cattle RFI should await the development of statistical methods suitable to handle additive and epistatic interactions.

Use of proximity loggers to Estimate Affiliative and Agonistic Relationships among Group-housed Holstein calves.

We used proximity loggers to map the social network of 15 group-housed suckling Holstein calves over a 70-day period divided into five trial periods. Tag ID, encountered tag ID, and encounter start time and length were collected from the proximity loggers. Use of 3D matrices and trendlines distinguished three encounter types: "rapid decline" (up to ~ 120 s), "moderate decline" (~120 to ~ 600 s), and "exponential decline" (longer than ~ 600 s). We hypothesized that a random encounter between two calves with an agonistic relationship would terminate quickly, whereas affiliative encounters would linger. Quadratic assignment with 5000 random permutations revealed a significant negative correlation between short encounters ("agonistic") and long encounters ("affiliative") matrices in periods 1 and 5 (r = -0.490 and -0.767, respectively), tendency toward negative correlation in period 3 (r = -0.141, p = 0.104), and no significant correlations in periods 2 and 4. These results were in accordance with the social network analyses revealing agonistic (short encounters) relationships in those periods. We suggest using this method in further studies on the effects of various factors on social network dynamics and its effect on health, intake, growth, and efficiency.

Reducing dietary sodium of dairy cows fed a low-roughages diet affect intake and feed efficiency, but not yield.

Wastewater from dairy farms has become a major environmental and economical concern. Sodium residue in treated and untreated wastewater from dairy farms used for irrigation can lead to soil and groundwater salinization, with the risk of soil degradation. We examined the effect of reducing sodium fed to mid to late lactating cows from 0.61% (high sodium [HS]) to 0.45% (low sodium [LS]) of dry matter on dry matter intake (DMI), milk and milk-component yields, eating behavior, apparent total track digestibility, feed efficiency, and sodium excretion into the environment. We randomly assigned 28 multiparous high-yielding ( > 35 kg milk/d) cows to 1 of 2 treatment groups (LS or HS) in a crossover design, with 7 d of adaptation and 28 d of data collection. Reducing sodium in the diet reduced sodium intake from 171 to 123 g/d while lowering sodium excreted in the manure by 22%. Energy corrected milk (ECM) yield (37.4 kg/d) and sodium excretion in the milk (33.7 g/d) were similar for both groups. The DMI of LS cows was lower than that of HS cows (27.3 vs. 28 kg/d) and consequently, feed efficiency of the LS cows was higher (1.40 vs. 1.35 ECM/DMI). Eating rate, meal and visit frequency, and eating time were similar for both treatments; meal and visit duration were longer for the HS cows, and meal and visit sizes tended to be larger. Digestibility of DM and amylase-treated neutral detergent fiber remained similar. Based on the results of this study, and discussed considerations, we recommend lowering the dietary sodium content for mid to late lactating cows in commercial herds to 0.52% of DM, in order to reduce sodium excretion to the environment via urine.

Proteomic analysis of adipose tissue revealing differentially abundant proteins in highly efficient mid-lactating dairy cows.

The improvement of nutrient utilization efficiency in dairy cows represents an important task in view of the current rising demand for animal products and sustainable resource usage. In this perspective, the identification of appropriate markers to identify the most efficient animals for dairy production becomes a crucial factor. Residual feed intake (RFI), which represents the difference between predicted and actual intake, is used to define the efficiency of cows. In this study, subcutaneous adipose tissue (AT) was collected from five high efficient (HEF) and five low efficient (LEF) mid-lactation Holstein dairy cows, that represented subgroups of the 20% lowest RFI values (HEF) and highest 20% RFI values (LEF), out of a cohort of 155 cows that were examined for feed efficiency at the individual dairy barn at Volcani Institute, Israel. Adipose samples were examined for proteomic analysis by nano-LC/MS-MS and gene expression by RT-PCR. A total of 101 differential proteins (P ≤ 0.05 and fold change ± 1.5) and two protein networks related to feed efficiency were found between HEF and LEF cows. Among the enriched top canonical pathways, FAT10 signaling, EIF2 signaling, Sirtuin signaling, Acute phase response signaling, Protein ubiquitination and mTOR signaling pathways were related to feed efficiency in AT. Furthermore, abundance of transferrin (TF; FC = 78.35, P = 0.02) enriched pathways, including mTOR signaling, LXR/RXR and FXR/RXR activation was found in AT of HEF cows. Relative mRNA expression of RBM39, which is involved in energy metabolism, was decreased in AT of HEF versus LEF. The relationship found between the AT proteins and/or metabolic pathways and the feed efficiency demonstrates that AT may reflect metabolic adaptations to high efficiency, and suggests that these proteins together with their metabolic mechanisms are suitable candidates as biomarkers to identify efficient cows for dairy production.