The objective of this paper was to evaluate the effects of high temperatures on calves. The hypothesis that the red and white blood cells, health, and performance of calves would be influenced by the temperature period at birth and gender was tested. Sixty-three Holstein calves were used. They were reared in individual hutches from the second day of life to weaning at the age of 8 weeks. All calves were allotted to treatment groups according to the temperature period at birth: moderate temperature period 1 (MT1), high temperature period (HT), moderate temperature period 2 (MT2). The same conditions of nutrition were ensured. We recorded 62 summer days and 14 tropical days during HT. Sixty-six days with a value above 72.0 of the temperature-humidity index (THI) and 26 with values greater than 78.0 were found. No significant differences were found in red blood cells with the exception of hemoglobin between MT1 and MT2 (p = 0.031) during the 8th week. Significant differences were observed among treatment groups in the percentage of eosinophiles during the 6th week (p = 0.044). The HT calves had the least body weight from the first week to weaning (p = 0.053) and the highest water consumption (p = 0.042). The results emphasize the ability of dairy calves to maintain homeostasis during prolonged periods of heat stress. The exposure to high temperatures resulted only in a significant decrease of starter concentrate consumption and reduced growth.

The average temperature of the Earth surface keeps increasing and the hot summer 2003 may have a bearing on global warming. The majority of farmers were not ready to cope with such situation, so it could bring about significant economic losses. The number of days with extremely high temperatures which substantially influence the performance of animals is increasing, and this tendency will continue according to predictions. The above assumption will influence the management of dairy husbandry. We will have to consider housing and technological systems that will reduce this negative effect of climatic extremes when designing an optimum farm environment.It is apparent that performance, welfare and health of the animal are influenced by biometeorological factors. The most important climatological factors are high temperatures and relative humidity during the hot season and the wind-chilling factor during the cold season of the year (Gregoriadesová and Doležal, 2000). In the majority of barns for cows and heifers, the limits of air relative humidity were exceeded (Šoch et al., 2000).Summer climates cause the stress of dairy cows resulting in milk production depression. Heat stress occurs when the ambient temperature is higher than that of the animal's thermal neutral zone. The heat load is greater than their ability to lose heat (Šoch et al., 1997;Dolejš et al., 2000a). The potential for heat stress exists when the air temperature rises above the comfort zone, particularly if humidity is also high. When the tem- Effects of high air temperatures on milk efficiency in dairy cowsJ. BROUČEK, Š. MIHINA, Š. RYBA, P. TONGEĽ, P. KIŠAC, M. UHRINČAŤ, A. HANUS Research Institute of Animal Production, Nitra, Slovak Republic ABSTRACT: 26 herds with 71 586 individual records were used. We tested a hypothesis that milk efficiency was influenced by the elevation of the farm, housing system, breed, area of altitude, and by the cooling of dairy cows. There were 20 herds from lowlands and 6 herds from mountains, 20 herds from free-stall housing, 6 herds from tie-stall housing. 8 herds consisted of Slovakian Pied cattle, 4 herds of Red Holstein cattle, 11 herds of Black-Pied Lowland cattle and 3 herds of Slovakian Pinzgau cattle. The herds were divided into 4 groups according to the nearest meteorological station, and they were distributed according to the type of cooling. 10 herds were cooled by misting, 16 herds by fans. We recorded from 96 to 117 summer days and from 49 to 63 tropical days in lowlands for this summer period. Ninety days with temperature-humidity index (THI) above 72.0 were found in the lowest-elevation area. During 55 days we recorded the values higher than 78.0. Production of milk was higher in lowlands than in mountains (8 761.4 kg vs. 6 372.0 kg; P < 0.01). Differences were also recorded in the evaluation of fat and protein production (346.0 kg vs. 275.9 kg; P < 0.01; 282.6 kg vs. 205.9 kg; P < 0.001). Milk and protein production was higher in free-stall housing than in tie-stall housing (8 656.3 kg vs. 6 722.1 kg...

The study aimed to evaluate the effect of elevated temperature on milk production of dairy cows in southern Slovakia in the year 2003. The hypotheses that milk yield is influenced by the stage (peak, midlactation and late lactation), cooling (fogger+fan or fan), and breed (Slovakian Pied cattle and Blackand-White Holstein were tested. Production data included 47,600 test-day records belonging to 16 herds situated in lowlands. During the period from May to September, 113 summer and 59 tropical days were recorded, eighty days were with a mean termal humidity index (THI) value above 72.0, on twelve days we recorded mean values above 78.0. Differences between peak stage (S1) and late lactation stage (S3) were significant in all months, between

ABSTRACT:The aim of this study was to determine the impact of the length of calf sucking milk from its own mother on calf growth at the age of 3 months and milk yield of mothers. We tested a hypothesis that the nursing of calves by their own mothers increases the body weight of calves and decreases the milk production. 50 Holstein primiparous cows and their calves were divided into three groups according to the sucking length of calves: 7 days (A), 14 days (B) and 21 days (C). All calves suckled mother's colostrum and milk while mothers were milked twice per day. After weaning from mother calves were kept in individual hutches until 56 days of life, and then in group housing pens. In the period from birth to weaning the calves of group A reached the lowest and the calves of group C the highest daily gains (0.35 kg, 0.46 kg, 0.54 kg; P < 0.01). The lowest gain was recorded in animals of group A (0.55 kg) and the highest gain was reached by calves of group C (0.74 kg) for the period from birth to three months of age. For the first 305 days of lactation cows of group A produced insignificantly more milk than group C (7356.5 kg, 6779.2 kg, 6663.9 kg). A significant difference in milk production was recorded only during the first seven months of lactation (5494.5 kg, 5041.9 kg, and 4872.3 kg; P < 0.05). The long stay of calves with their mothers influences the growth of calves positively, but the milk production of mothers may decrease. Therefore, the stay of calves with the dam within 21 days after birth is not recommended for high-yielding dairy cows.

The aim of this work was to evaluate effects of high temperature on the growth, feed intake and health condition of calves kept in individual hutches in southern Slovakia. We tested a hypothesis that the calf performance would be infl uenced by the season at birth, sire lineage and gender. Sixtythree Holstein calves were reared in individual hutches from the second day of life to weaning at the age of 8 weeks. The calves originated from 5 sires. All calves were divided according to the temperature period at birth. The effects of period were determined according to two patterns: in pattern A, a low temperature period 1 (LT1, from April 4 to June 11, 69 days), high temperature period (HT, from June 12 to September 14, 95 days) and low temperature period 2 (from September 15 to November 24, 70 days) were distinguished; in pattern B, the results obtained in the LT1 and LT2 periods were combined and compared with those found in HT period. The same conditions of nutrition were ensured. We recorded 62 summer days and 14 tropical days during HT. Sixty-six days with the THI value above 72.0 and twenty-six with the values higher than 78.0 were found. The calves born during the HT had the lowest body weight from the fi rst week to the weaning in the both patterns (P<0.05). These calves drank up the most of water to the weaning, and had the least intake of starter mixture (P<0.05).