Study of influence of heat stress on some physiological and productive traits in Holstein-Friesian dairy cows

Received: October 6th, 2020 ; Accepted: February 1st, 2021 ; Published: March 18th, 2021 ; Correspondence: [email protected] aim of the research was to study the effect of heat stress (HS) on some physiological and productive traits in Holstein-Friesian dairy cows. The study included 22 cows on different parities. In the building where the cows were housed, the temperature-humidity index (THI) was reported at 10:00 and 15:00 h, at the same time the rectal temperature (RT) and respiratory rate (RR) were reported for each of the examined cows. The daily rumen activity was taken from the SCR system by Allflex. The average THI values in May were 71, in June - 75, in July - 74, and in August - 77, from which it follows that in the summer months the cows were in conditions of mild to moderate heat stress throughout the day. The average daily milk yield of the cows increased from May to June and reached 41.44 kg day-1 , then decreased in July and August to 37.2 and 32.48 kg day-1 , respectively. With an increase in the THI values, an increase in the RR and RT was registered, as in THI above 79 the RR was 56.54 per min, and the RT was 39.33 °C. With increasing the THI values, the rumination of the cows decreased from 563 per day at THI < 72 to 542.5 at THI > 79. In cows with high daily milk yield, a higher RT was registered, and in cows with more than 50 kg per day, the RT was 39.09 °С. A more intense rumination was found in cows with higher daily milk yield. In cows with an average daily milk yield of 33.26 kg, an average of 450 ruminations per day were reported, and in those with an average milk yield of up to 42.89 kg - 650 ruminations per day. From the research conducted it was found that the studied physiological traits - rectal temperature, respiration rate and rumination are influenced by HS and the intensity of this effect depend on the daily milk yield of cows and THI levels

CHONDROCALCINOSIS AURICULAE WITH CHONDRODERMATITIS NODULARIS HELICIS

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Relation between first lactation milk yield and functional traits in dairy cows

The aim of the study was to analyze the relationship between first lactation milk yield (FLMY) and age at first calving (AFC), longevity and productive life in dairy cows. The study covered 944 Holstein cows housed in 5 dairy cattle farms in Bulgaria. All cows from the five farms culled in the period 2012–2018 with FLMY data were included. The average AFC for all culled cows included in the study was relatively high for the Holstein-Friesian breed - 29.75 months. The average FLMY of the herds included in the study was 7,660.94 kg with significant herd variation from 5,899.09 kg to 8,646.0 kg. Significant effect of the herd (P < 0.001), AFC and the associated effect of the herd and AFC (P < 0.05) on the average FLMY were found. The highest FLMY was reported in primiparous with AFC of 28–30 months – 7,860.8 kg, and the lowest in those with AFC ≤ 24 months – 7322.8 kg. In the herd with the lowest average FLMY - 5,899.09 kg 27.5% of the heifers had calved at age over 34 months. A statistically significant effect of AFC (P < 0.001) was found on longevity, whereas the productive life was significantly influenced by FLMY (P < 0.05). A tendency for higher longevity for cows with higher AFC of 34–37 months and over 37 months – 5.9 and 5.8 years, respectively was observed. The lowest were the longevity values for cows calved at age up to 24 months – 4.9 years. The cows with the lowest average FLMY (up to 4,000 kg) had the shortest productive. Both very low and high AFC were associated with lower first lactation cow productivity and shorter productive life. The losses for farmers were greater when keeping a high AFC in heifers, which increases the cost for housing them, and the lower productivity and longer productive life reduce the probability

Influence of the van Hove singularity on the specific heat jump in BCS superconductors

Within the weak-coupling BCS scheme we derive a general form of the coefficients in the Ginzburg-Landau expansion of the free energy of a superconductor for the case of a Fermi level close to a van Hove singularity (VHS). A simple expression for the influence of the VHS on the specific heat jump is then obtained for the case where gaps for different bands are distinct but nearly constant at the corresponding sheets of the Fermi surface.Comment: 8 pages, 2 figures, LaTeX2