Summer heat stress affects production and reproduction of dairy cows. Israeli “Herdbook” data show a decrease in production difference between the seasons in dairy farms all over the country. The conventional cooling method used in the last decade make use of large amounts of water and energy and creates pollution problems due to the large amounts of water used. Lately, an alternative cooling system was developed combining wetting and cooling the cows along the feeding line by means of low-pressure misters installed in front of the fans. Recent data presented last year showed that using this method improved considerably production and reproduction of dairy cows during the summer in a farm located in the southern part of Israel, while reducing significantly the wetness of feeding line and the environmental pollution. The data findings of last year presents us with a method suitable to the conditions and demands of most of the Israeli farms.
The aim of this research was to evaluate the capability of different cooling systems to increase milk production, translated into the average daily production ratio between winter and summer in each farm.
Five dairy farms located in large areas of the south part of Israel and being under the ICBA milk control system (Israeli Herdbook), participated in this survey. The cows in all five farms were fed a same TMR and were milked three times a day, all year through.
In farm A, a cooling system was installed combining low pressure misting and forced ventilation, along the feeding line ( “CowKool “ manufactured by Polak Bros Ltd). The system includes 20” CowKool” fans and 4 misters of a capacity of 7 liters/hour, (manufactured by “ Dan sprinklers”) installed in front of each fan. The fans were installed at intervals of 6 m’ of each other, at a height of 2.2m’ above the cows’ backs. The system was operated the whole summer (July-October), between 06:00 to 22:00 hours, in cycles of half an hour each hour. The cooling treatment included a constant operation of the ventilation and wetting for 1 minute every 4 minutes.
In farm B fans and garden sprinklers were installed in the holding pen. The system was operated between 06:00 and 22:00 hours under constant ventilation and every 4 minutes a one-minute wetting was given. The cows stayed in the holding pen before the milkings and had free access to the yard between milking. The other three farms, served as control farms with no cooling.
Climatic data were automatically recorded during the summer by a “HOBO” recorder. Temperature Humidity Index (THI) values were calculated every hour for the whole summer. The cow’s body (rectal) temperature (0C), was measured in a group of cows in the farms where the cooling systems were installed. The milk production data were drawn from the monthly control figures in the ICBA Herdbook computer. Only control figures done within the first 300 days of the lactation of each cow were taken into account. The statistical process of the data was done by analyzing the multi factorial variance GLM of the SAS software. The following factors were included in the model : Treatment, Herd, Lactation, Season, Days in Lactation and their interaction. The comparison was done for the following criteria : Milk production (kg/d), fat (%) and protein (%). And Economical Corrected Milk (ECM), based on the value of milk according to fat and protein prices.
The months of July – October were defined as summer and December-February were defined as winter. The temperatures during most of the summer days moved around 22 to 35 degrees and the humidity rates ranged between 40% and 80%. The THI per hour ranged between 70 to 80, and was above the critical value for cattle during most of the summer days’ hours.
The rectal temperature of the cows was measured only in farm A. At 14:00 the rectal average temperature was 39.1 0C , while in only 44% of the cows a higher temperature than 39.1 0C was recorded. The average rectal temperature was set on 39.7 0C and 94% of the cows had temperatures of over 39.1 0C, for those cows received no cooling. Those findings point to an efficient cooling system.
The average daily milk production of cows in the survey was 32 Kg. The influence of Treatment, Lactation, Season and the Double interaction ( Treatment x Season ) and triple ( Days in lactation x Treatment x Season) were found statistically significant
(P < 0.01), for the milk as for the E.C.M. production. Averages of milk production and E.C.M. (Kg/d) in different treatments seasons are shown in Table 1.
Table 1 – Averages of Milk production and E.C.M. (Kg/d) and the ratio summer/winter in different treatments and seasons.
|Measured item|| Treatment
|“Misting” in feeding line
|cooling in holding pen||without cooling|
The results of this study show a clear advantage to the combined cooling of wetting and ventilating along the feeding line and its potential to reduce significantly the negative influence of the summer on milk production of high yielding cows in summer. These results match almost completely prior findings, published recently. It has to be said that those results were received at very low wetting level and environmental pollution relatively to the common system used in Israel wetting cows by sprinklers. Holding pen cooling contributes to the cows’ achievements in summer, but much less than the “misting in feed line” system.