RESUMEN
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.
RESUMEN
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.
RESUMEN
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.