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ThesisItem Open Access Effect of environmental heat stress on performance of crossbred dairy cattle(Department of Livestock Production Management, College of Veterinary and Animal Sciences, Mannuthy, 1989) Thiagarajan, M; KAU; Thomas, C KAmple evidences are available on the poor performance of livestock inhabiting the tropical regions of the world, compared to their counterparts in the temperate zones. By and large, the management practises adapted in the warmer areas are to be quite different from cooler regions to reach optimum productivity. Among the management practises, housing and feeding aspect needs to be given more emphasis in bringing about the much desired results to meet the ever increasing demand for livestock products. In the present work, an attempt has been made to investigate the effects of housing and feeding inter alia. On the growth and production of B. Taurus x B. indicus crossbred cattle. Besides these, some of the important climatic components, such as solar radiation, mean radiation, temperature of the surrounding and the wind velocity, the factors which have hither to been widely neglected, were tried to be methodically quantified and presented in relation to their direct effect on the physiological and productive responses of cattle. To assess the effect of shelter and the type of ration on the physiological responses and growth performance of crossbred cattle, an experiment involving 20 weaned heifer calves, was conducted at the University Livestock Farm (KAU), Mannuthy. The experiment included four treatments encompassing protection and exposure to solar radiation, and concentrate and roughage – oriented feeding in different combinations. The selected calves were distributed equally to the four treatments, observing the standard statistical procedures. Physiological variables like cardiac rate, respiration rate, rectal temperature and skin temperature were measured and recorded for all the calves twice a day on a fixed day in a week and for 14 weeks of the study by using standard equipments and procedures. The body weights and body measurements were recorded once in a fortnight at a fixed time in a day. The body measurements included height, length and girth. All the measurements were made on individual calves. The climatic data, atmospheric temperature, relative humidity, wind velocity, black globe temperature and vapour pressure were recorded inside the shed and atmospheric temperature, solar radiation, relative humidity, wind velocity, vapour pressure and rainfall were recorded in the open paddock. A continuous recording “Solar Radiation Balance Meter” was used to record the solar radiation continuously throughout the experiment. The average daily maximum air temperature that prevailed in the unshaded location during the hot – dry period was 350 C and in the shaded location, 300 C. During the rainy period the maximum temperature ranged from 25.37 to 29.310 C under the shade and 29.36 to 33.500 C in the unshaded location. The relative humidity ranged from 76 to 93 per cent in the mornings and 55 to 88 per cent in the afternoons. The wind velocity ranged from 0.13 to 0.97 m per sec in the unshaded area and almost zero in the shaded area. The vapour pressure ranged from 21.41 to 25.98 mm of Hg. The rectal temperature of the calves in the unshaded location was significantly higher than those of the shaded ones (P < 0.01) during the hot – dry period. Significantly lower value for rectal temperature was obtained for the concentrate – fed unshaded calves during the morning recording of rainy period and higher values were obtained in the afternoons indicating a diurnal rhythm. The skin temperature of the calves was always higher than the rectal temperature in all the cases except in the shaded calves on rainy days. During the hot – dry period, the respiration rates were significantly higher (P < 0.01) in the unshaded group compared to the shaded lot for the morning recordings and in the afternoons, in all the treatments, it was almost double of what was recorded in the mornings. In general, the cardiac rates were found to be higher in the afternoons, than the mornings and lower during the rainy period. Highly significant variations (P < 0.01) in all the physiological reactions measured were noticed between the housed and unhoused treatments, the calves exposed to direct solar radiation recording higher values of rectal and skin temperature and respiration and cardiac rates, with few exceptions. The higher physiological reactions of the calves in the open could be attributed to higher effective temperature caused by direct solar radiation. The analysis of growth parameters indicated significant differences in certain fortnights only. It was observed that maximum gains in live weight, height and girth were obtained by the calves exposed to solar radiation and fed roughage – oriented ration but the gain in length was the least in this group. The next best was the housed and concentrate oriented feeding group which had the highest gain in length, second highest gains in live weight and girth, but the lowest gain in height which implies that under housed conditions concentrate – oriented feeding and under exposed conditions roughage – oriented feeding favour better growth. In general, it was observed that housing in open conditions increased physiological reactions significantly but these increases were not physiologically meaningful to cause retardation in growth. With a view to study the effects of housing on cows with respect to milk production and other traits, eight cows were subjected to a switch over trial in which sheltered and unsheltered conditions alternated. The experiment ran for eight periods of one month each and in total, milk production for 33 weeks were partitioned into 15 weeks of early lactation and the remaining 18 weeks of late lactation periods. The cows were divided into two groups based on their milk yield. The cows of one of the groups at random were kept in an open paddock exposed to direct solar radiation while cows of the other group were housed in a tile – roofed shed. At the end of every month the groups were interchanged. For feeding the cows, adequate measures were taken to meet both maintenance and production requirement and requirements were worked out every fortnight. The physiological variables like the cardiac rate, respiration rate, rectal temperature and skin temperature of the individual cows were measured and recorded twice in a day, two days in a week, by following standard procedures. The twice daily milk yields of the cows were measured by individually weighing the quantity in kg at each milking. Milk fat and protein were estimated from samples collected with due precautions at every milking. The feed, grass and water consumption were measured for individual cows. Standard statistical methods were employed to analyse the data. Multiple regression analysis was resorted to find out the relationship of climatic variables with physiological responses. Highly significant (P < 0.01) differences were found between the shaded and unshaded locations in the relative humidity levels. This may probably be due to accumulation of moisture in the atmosphere inside the animal house resulting out of interference with free exchange of air by housing arrangements. Analysis also revealed highly significant (P < 0.01) difference in wind velocities between locations. The wind velocities recorded in the present experiment generally were lower than what had been suggested as ideal for tropical animal husbandry. The analysis of climatic factors revealed that the animals housed in the shaded location were under additional stress due to radiated heat from the surroundings apart from experiencing stress of the high air temperature. The same phenomenon was observed in the unshaded location also. Both the day and night total radiation values remained high. The rainfall distribution was not uniform during the period of study. In the early lactation period, the cardiac rates, respiration rates, rectal temperature and skin temperature of cows under exposed condition were high in the afternoons. Similar trend was observed in the late lactation period also. In both the treatment groups, all the physiological parameters recorded were on the higher side than the normally accepted standards. The cows had the physiological ability to bring the skin temperature on par with rectal temperature and sometimes even higher than that. The cows in the open seem to compensate during the night and bring down their body temperature to the level of sheltered and eat as much or more of grass and feed. This resulted in similar milk yield in late lactation and slightly higher milk yield in early lactation. Under the hot humid conditions, the higher wind velocity in the open seem to favour the cows considerably. The generally held view that under hot humid conditions ventilation is most important and animals do not need much elaborate housing gets further strengthened from these findings. It was observed that the fat percentages varied significantly (P <0.01) between treatments from both morning and afternoon milk obtained from the cows, the milk fat content being lower when they were exposed to direct solar radiation. The exposed cows though they had maintained their milk production higher, the milk fat content had dropped. A highly significant (P < 0.01) difference had been found between treatments in protein content of the afternoon milk indicating that exposure of cows to day time stress in the open sun considerably altered milk composition and reduced the protein percentage. During late lactation period, both fat and protein content in milk were lesser for the unshaded treatment but statistically there was no significant difference between treatments. A highly (P < 0.01) significant difference was observed in concentrate feed intake between shaded and unshaded treatments during early lactation and the reverse was observed in the case of grass consumption. The difference in overall mean water consumption under shaded and unshaded condition was highly (P < 0.01) significant, cows remaining in the open paddock drinking 21 to 23 per cent more water. Observations on physiological reactions revealed that the cows in the unsheltered condition made physiological compensations through increased circulatory and respiratory activities and by physical means during the night to bring down the rectal temperature in the morning to normal levels. During the late lactation period, no significant differences were found in the consumption of grass and concentrate feed by the cows between treatments. A highly significant difference (P < 0.01) was found only with water consumption. During the early lactation, the solar radiation was found to exert a negative, significant (P < 0.05) influence on the cardiac rates but the influence by wind velocity was positive and highly significant (P < 0.01). In the same way, the rectal and skin temperatures also were influenced significantly only by the wind velocity, the effect being negative and highly significant (P < 0.01). During the late lactation stage, the physiological parameters studied had not been influenced by the explanatory variables chosen except in the case of respiration rate which was positively and significantly (P < 0.05) influenced by black globe temperatures. The relationships between climatic variables and animal responses were not as intense when they were housed as when they remained exposed. However, the black globe thermometer readings which represented the combined influence of ambient temperature, wind speed and solar radiation, was found to have significant influence on the respiration rate. This may indicate that the black globe thermometer deserves to be used more extensively for evaluating thermal characters of animal environments. The results of the study clearly indicate the beneficial effects of ‘open – air’ conditions in a hot – humid tropical environment. Factors such as comfort of men tending animals and hygiene preclude cattle keeping without housing structures. The result of these experiments however point to the advisability of loose housing system in which cattle have continuous access to an open paddock shaded by trees. The sheltered area of the loose houses also should be simple roofs on pillars allowing maximum ventilation and air movement. It was also found that growing heifers can be maintained equally well on a roughage – oriented feeding schedule.ThesisItem Open Access Draught potentialities of indigenous and cross-bred cattle(Department of Livestock Production Management, College of Veterinary and Animal Sciences, Mannuthy, 1988) Sreekumar, D; KAU; Thomas, C KThe draught performance of Bos indicus x Bos Taurus crossbred bullocks was compared with that of bullocks belonging to a South Indian draught breed (Kangayam type) under the agro - climatic conditions of Kerala, with a hot – humid tropical climate. Two pairs of adult cross – bred bullocks (Jersey x Red Sindhi) and two pairs of adult indigenous bullocks (Kangayam type) were used for ploughing on dry land for 4 hours and 5 hours continuously on alternate days. Physiological responses like respiratory rate, pulse rate and rectal temperature and haematological parameters like haemoglobin per cent, erythrocyte sedimentation rate, packed cell volume, lactic acid and plasma bicarbonate were estimated before work, immediately after work and after 1 hour of rest after work. The dry matter intake and water intake on days of work and on days on which no work was done were measured and compared. In order to evaluate the relative efficiency of work, the average speed of walking and the total area ploughed in 1 hour were compared. The cross – bred bullocks had significantly higher physiological responses even before the start of work. As a result of work the physiological responses increased significantly and during rest, the values declined but did not reach the pre – exercise values after one hour rest. The haemoglobin per cent of blood, packed cell volume and plasma bicarbonate content decreased significantly and the erythrocyte sedimentation rate and blood lactic acid content showed a significant increase as a result of work. One hour of rest was not sufficient to bring these parameters to pre – exercise values. The indigenous bullocks consumed more dry matter per metabolic body size than the cross – breds. However, the total dry matter intake by the indigenous bullocks was less due to smaller body size. It was found that work had no effect on dry matter intake as the dry matter intake of indigenous and cross – bred bullocks on days of work and on days on which no work was done was almost similar. The cross – breds consumed more water per day matter per metabolic body size on days of work and no work. The total area ploughed by indigenous bullocks in 1 hour was significantly more than the cross – bred bullocks. Also, the average speed of walking of indigenous bullocks was greater than that of the cross – breds. The enhanced physiological reactions in the cross – breds even before the work pointed to the fact that they were under some degree of thermal stress due to the hot – humid climate. Exercise (work) increased the stress and widened the gap between the cross – breds and indigenous bullocks. The lower total feed intake and greater speed and more area ploughed per unit time make the indigenous Kangayam type bullocks a more economical animal. Their higher feed intake and lower water intake per unit metabolic size indicates that they can better sustain energy supply to the tissues for work and manage under lower water availability. Coupled with these advantages, their greater heat adaptability make them a superior draught animal.