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I. Vujanac et al. Large Animal Review 2012; 18: 31-36
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Milk production in high-yielding dairy cows under different environment temperatures I. VUJANAC1, D. KIROVSKI2, H. ŠAMANC1, R. PRODANOVIC´1, N. LAKIC´3, ˇ IC´2 M. ADAMOVIC´4, O. VALC 1
Department of Farm Animal Diseases, Faculty of Veterinary Medicine University of Belgrade, Bulevar oslobod¯enja 18, 11 000 Belgrade, Serbia 2 Department of Physiology and Biochemistry, Faculty of Veterinary Medicine University of Belgrade, Bulevar oslobod¯enja 18, 11 000 Belgrade, Serbia 3 Department of Agroeconomy, Faculty of Agriculture University of Belgrade, Nemanjina 6, 11 080 Zemun, Belgrade, Serbia 4 ITNMS, Bulevar Franš d’Eperea 86, 11 000 Belgrade, Serbia
SUMMARY The aim of this paper was to evaluate the effects of different environment temperatures on milk production in dairy cows under conditions typical for the moderate-continental climate. The trial was carried out on 40 Holstein Friesian dairy cows (20 cows in summer and 20 cows in the spring season). The cows were monitored from day 30 to day 90 of lactation and housed in a stable which during the summer was not equipped with additional cooling. The temperature-humidity index (THI) was recorded hourly. Milking was measured daily. Based on the results calculated for average all-day THI, during the spring season the cows were not exposed to heat stress. During the summer season, especially in the afternoon hours, the cows were exposed to the effects of moderate to severe heat stress. Average daily milk yield in the spring season from day 30 to day 90 of lactation was significantly higher (p < 0.001) compared to the same lactation period during the summer season. Nevertheless, there was no significant difference in average milk yield from day 30 to day 60 of lactation (p = 0.110) between spring and summer season. Average milk yield per cow from day 61 to day 90 of lactation in the summer period was significantly lower (p < 0.001) compared to the same period during the spring season. Average daily feed consumption was significantly lower (p < 0.001) during the summer compared to spring during whole trial period. In conclusion, although feed consumption was significantly lower during the summer season throught the study, milk production compared to the spring season, was significantly lower only from day 61 to 90 of lactation. This could mean that the negative impact of feed intake on milk production is not as effective during early lactation (until day 60 of lactation), when homeorhetic mechanisms play a significant role in the rearrangement of metabolism, as it is thereafter i.e. from day 61 to 90 of lactation.
KEY WORDS Dairy cows, milk yield, temperature-humidity index.
INTRODUCTION Cows exposed to environment temperatures over 27°C with a temperature-humidity index (THI) over 72 are considered to be under heat stress1. A number of papers on the subject of negative effects of heat stress on milk production, reproduction and health of high-yielding dairy cows have been published2,3. For a long time it was considered that a decrease in milk production under conditions of high environmental temperature is the consequence of concurrent reduced feed intake2,4. However, in the case of heat stress decreased feed intake participates with 35% in the overall production fall4. The metabolic rearrangement is responsible for the remaining 65% production losses. In fact, in the case of heat stress the energy requirements increase by up to 30%5. This is due to the fact that energy is partially used for processes which are needed in order to enable the emission
Autore per la corrispondenza: Danijela Kirovski (
[email protected]).
of excessive heat under conditions of heat stress. In cattle the first mechanism of protection from excessive heat is the increase in body temperature6. The process is indispensable in order to maintain the temperature difference between the body and the environment, thus enabling heat loss not only by evaporation from the body surface, but by conduction, convection and radiation, also. However, when ambient temperature is over 30°C, heat loss is possible only by more intensive water evaporation from the body surface and increased breathing rate7. These two physiological mechanisms have high energy requirements. In order to achieve conditions of heat stress the majority of authors studied its effects under controlled ambient temperatures in heated chambers. During these studies the cows were exposed to continuous moderate or high heat stress4,8. Such controlled conditions are close to the climatic changes which are present in the subtropical climate and are quite different from the conditions present in the moderate-continental climate during the summer season. The basic difference between the above mentioned climatic zones lies in the fact that during the summer the moderate-continental climate exhibits marked temperature variations between the
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Milk production in high-yielding dairy cows under different environment temperatures
day and night. Thus, day temperatures can be double compared to those recorded during the night. This is the reason why on dairy farms in moderate-continental climate zone heat stress is present as a periodical - half day feature. Such action of high environment temperature can be a significant strain for the high-yielding dairy cows in lactation as in order to adapt to heat stress their homeostatic mechanisms require a longer time9. The largest number of studies on the effects of heat stress on milk production was done on dairy cows which were in lactation for over 100 days4,8. At this time the lactating cows have reached a state of energy balance and the homeorhetic mechanisms were no more active. It is still an open question if the realignment of metabolism in conditions of heat stress is any different during the early stages of lactation during which the cows are in a negative energy balance. The aim of this paper was to evaluate the effects of different environmental temperatures on the milk production in highyielding dairy cows from day 30 to day 90 of lactation under conditions typical for the moderate-continental climate.
MATERIALS AND METHODS Experimental animals The trial was carried out on high-yielding Holstein Friesian dairy cows. The measurements were done during the summer from June 20th to August 18th 2008 and in spring from March 20th to May 17th 2009. Randomly 20 cows were selected for the summer and 20 for the spring research period. All cows were between the second and fourth lactation, aged from 3 to 7 years, and clinically healthy. The experimental animals were included in the study at day 30 of lactation and monitored until day 90 of lactation.
Table 1 - Ingredients of cow’s diet from day 30 to day 90 of lactation. Ingredient
Kg
Alfalfa hay
3.43
Corn silage 44% DM
9.50
Corn silage 33.94% DM
9.00
Alfalfa haylage 47.40% DM
5.00
Brewer’s grain 21.00% DM
5.00
Corn grain
2.50
Barley grain
1.50
Soybean grits
1.30
Soybean meal 44%N
1.13
Wheat flour
1.30
Sugar beet pulp
1.82
DextroFat SC
0.40
Optigen II, 41% N
0.14
Dextrose monohydrate
0.10
Dicalcium phosphate 18% P
0.27
Magnesium oxide
0.05
Sodium bicarbonate
0.15
Sodium chloride (iodized)
0.07
Calcium carbonate
0.03
Total
42.69
previous day to 1000 of the following day. The daily THI were obtained by measuring the average THI measured from 1000 to 2200 of the following day.
Housing The cows were housed in a tie system stalls on a commercial farm, located at coordinates 44°49’14’’ North, 20°27’44’’ East, in a stables which during the summer does not have side walls and the metal roof construction is tiled with plywood without thermal insulation. The stable, beside roof ventilation, was not equipped with additional cooling (fans or misters). During the spring period the sides of the stable were build from rolled hay blocks 140 x 110 cm.
Environmental conditions Temperature, relative humidity, and dry and wet thermometer temperatures were measured at hourly intervals. The values were recorded at the meteorological station of the Republic Hydrometeorological Service of Serbia located at 2 km from the farm. Based upon the collected data the hourly heat indices (THI - temperature-humidity index) were calculated for the whole period of the study. The THI was calculated with the formula: THI = (Tdt* + Twt**) x 0.72 + 40.610 *Tdt - dry thermometer temperature; **Twt - wet thermometer temperature. Based upon the recorded values the average all-day (measured from 2200 of the previous day to 2200 the following day) THI was calculated. The overnight THI values were obtained by the hourly THI measured in the period from 2200 of the
Diet During the summer and spring period the studied cows were fed twice a day (645 and 1730) with a mixed meal (TMR - Total mix ratio) (Table 1). Feed intake was monitored on a daily basis. The nutritive value of the diet is shown in Table 2.
Milk yield Milking was measured daily during the whole trial period in both spring and summer season using automatic milking machine “Delaval”. Milk yield was monitored at the morning and evening milking (600 and 1800).
Statistical analysis Statistical analysis was performed using analysis of variance for repeated measures and the t-test for independent or dependant samples. The statistical analysis of the experimental results was performed by using the STATISTICA v.6 packet. The differences were considered significant at p < 0.05. All results are expressed as means ± SE.
RESULTS Based on the results calculated for all-day THI, during the spring season (Graph 1) the cows were not exposed to heat stress.
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I. Vujanac et al. Large Animal Review 2012; 18: 31-36 Table 2 - Chemical composition of cow’s diet. Chemical composition DM kg
23.63
Net energy of lactation (NEL) MJ
163.03
Crude protein (CP) %
16.05
Rumen undegradable protein (RUP) %
5.06
Crude fat %
4.78
Acid detergent fibre (ADF) %
22.08
Neutral detergent fibre (NDF) %
35.48
Ca %
0.90
P%
0.52
Na %
0.36
Cl %
0.29
Mg %
0.34
K%
1.18
S%
0.22
Mn ppm
82.40
Cu ppm
25.64
Zn ppm
96.90
Co ppm
0.54
J ppm
1.64
Fe ppm
220.53
Se ppm
0.70
Vit A IU/kg
21 273.58
Vit D IU/kg
3 445.30
Vit E Iu/kg
69.35
Graph 1 - THI values during the spring season.
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During the summer season (Graph 2), especially afternoon hours, the cows were exposed to the effects of moderate to severe heat stress. The milk yield during the spring season at the start of the study was 41.72 ± 0.97 L, after which the milk production had an increasing trend (Graph 3). In spring, average daily milk yield was significantly higher than the initial value (day 30 of lactation) during all experimental periods (except on days 31, 33, 41, 51, 52, 63 and 66 of lactation). On day 60 of lactation the average daily milk yield was 43.75 ± 1.5 L. After this period the daily milk yield did not significantly change up to the end of the trial i.e. day 90 of lactation, except at days 62, 80, 81 and 82 of lactation when it was significantly higher than on day 60 (p = 0.025; p = 0.029; p = 0.013; p = 0.013, respectively). At the start of the summer period the milk yield of the cows was 37.65 ± 0.89 L (Graph 3). After this period the average milk production per cow increased in a more marked fashion compared to the spring period. The ascending trend of the average milk production per cow is maintained with only slight variations up to day 61 of lactation when average milk yield was 43.30 ± 1.52 L. Namely, until day 61 of lactation, average daily milk yield was significantly higher then on day 30 of lactation except from days 32 to 37 and day 55 of lactation when there was no difference in milk yields compared to the initial value. At day 60 of lactation daily milk yield was 43.87 ± 1.24 L. After day 61 of lactation, the average milk production per cow showed a steep decrease. From days 62 to 90 of lactation day milk production was significantly lower compared to days 60 and 61, respectively. After 64 days of lactation the trend was maintained up to the end of the study i.e. milk yields did not change significantly compared to day 64 (except on days 77 and 84 of lactation). The milk yield of the cows included in the study during the spring season was significantly higher compared to the sum-
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Milk production in high-yielding dairy cows under different environment temperatures
mer for the period from day 30 to day 40, and from day 64 of lactation to day 90 (Graph 3). Results of group tests, analysis of variance for repeated measures, show that tested animals had a significantly different dai-
Graph 2 - THI values during the summer season.
Graph 3 - Milking yields during the summer and spring period.
ly milk yield relative to day of lactation (Table 3). In spring and in summer in the period from day 30 to day 90 of lactation, and in subperiods from day 30 to 60 and day 61 to 90, the factor day of lactation caused statistically significant differences
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I. Vujanac et al. Large Animal Review 2012; 18: 31-36 Table 3 - Results of analysis of variance for repeated measures in different seasons and lactation periods. Period
Factor
Spring
Summer
F-value
p level
F-value
p level
Day 30 to 90 of lactation
day cow
2.559 264.651
