Dairy cows may prioritise resting over other behavioural activities and cows that are restricted from lying down exhibit behavioural and physiological changes that are likely to alter health and milk production. Along with the flooring discomfort, heat stress can affect metabolic processes and decrease feed intake, which can contribute further to a reduction in the milk yield (Mandal et al., Reference Mandal, Bhakat and Dutta2021) and also result in a changed milk composition (Nasr and El-Tarabany, Reference Nasr and El-Tarabany2017). Teat lesions are very painful and frequent on hard floor surfaces and the number of even slight injuries is associated with increased somatic cell counts (Geishauser et al., Reference Geishauser, Querengasser, Nitschke and Sorbiraj1999) and higher incidence of mastitis. It is obvious from the above that high-performance dairy cows require ample rest and a comfortable environment to maximise their productivity and ensure their well-being. Therefore, knowledge of housing components is essential to ensure adequate rest, optimum milk production in terms of quantity and composition and good udder health of high producing crossbred cattle. Sinha et al. (Reference Sinha, Kamboj, Lathwal and Ranjan2017) also recorded that cows housed on sand floors had significantly higher average daily milk yield (18.2% higher) than cows housed on concrete floors. During the summer season, the paddy straw thatched asbestos roof shed was more effective than simple asbestos and white painted asbestos roof in maintaining a comfortable micro-environment for crossbred cows, indicated by high milk production (Patil et al., Reference Patil, Bharambe and Khirari2014).
For all these discomforts, correlations to decreased milk production and compromised udder health are accepted. Whilst researchers have investigated the impact of the thermal environment (controlled through roofing modifications) and flooring on cow udder health and milk production independently, there is a lack of understanding on the impact of a combination of the two. To test the hypothesis that housing modifications can protect crossbred dairy cows from environmental stress and thus, play an important role in increasing production performance, the present study aimed to investigate the effects of sand flooring and roof insulation on milk composition, rate of production and udder health of Jersey crossbred cows housed in a tropical climate.
Materials and methods
Animals and management
Twenty lactating crossbred Jersey cows were selected from the herd housed at the Eastern Regional Station (ERS) of Indian Council of Agricultural Research-National Dairy Research Institute, West Bengal, India (Online Supplementary Fig. S1). The macroclimate in the research area was hot and humid. In the summer the highest ambient temperature reached 39°C, while the lowest temperature dropped to around 8°C in the winter. Cows were divided into two groups: control (T 0) and treatment (T 1). Each group consisted of ten cows. The average age (months), lactation number, stage of lactation (days) and average milk yield (kg/day) of control group (T 0) were 64.93, 2.6, 38.4 and 11.86, respectively, and that of treatment group (T 1), the values were 58.88, 2.4, 37.5 and 11.39, respectively. Feeding and general management (aside from housing design manipulations) was the same for both groups. Each group had access to its own yard area measuring 151 m2, 57 m2 of which was under cover. Further details are provided in the online Supplementary File materials and methods and Table S1.
THI (Temperature Humidity Index)
For THI dry bulb and wet bulb record was noted 3 times in a day i.e., morning (7–8 am), afternoon (1–2 pm) and evening (4–5 pm). Formula used for calculating THI was that of Kadzere et al. (Reference Kadzere, Murphy, Silanikove and Maltz2002): THI = 0.72 (T DB + T WB) + 40.6; where T DB = dry bulb temperature in °C and T WB = wet bulb temperature in °C.
Experimental design
Cows in the control group (T 0) were kept in ‘traditional’ loose housing conditions, i.e. concrete flooring across the entire yard and asbestos sheet roofing comprising the sheltered covered area (Online Supplementary Fig. S2). Sand flooring (4–6″ deep) was provided to the treatment group (T 1) across 38% of the total yard area (Online Supplementary Fig. S3). To maintain the proper hygienic condition of sand floor, it was cleaned manually two times (morning and evening) daily with the help of shovel and on a weekly basis the bedding material was turned with the addition of ½ kg lime over the whole floor. Finally, the entire sand bed was replaced with new sand after 2.5 months of experiment. The asbestos roof in the treatment group was insulated using a 4″ thick thatch (paddy straw) ceiling under the asbestos roof. Three sides of the yards were surrounded by a half brick wall, the remaining side was fenced by manger and standing space. Floor and inside roof surface temperatures were measured by infrared digital thermometer (−32°C ˜ 320°C) of Metrix + TM, MT 2A. Rectal temperature, pulse rate and respiration rates of crossbred cows were recorded at weekly intervals at 9:00 AM and 2:00 PM. Milk yield was recorded over 5 months i.e. December to April. Modified California mastitis test (MCMT) was performed in the milking byre itself using the procedure described by Devi (Reference Devi1989) and (detailed in online Supplementary Table S2) and somatic cell count (SCC) was performed as per the method described by Schalm et al. (Reference Schalm, Carroll and Jain1971) within one hour of collection. Among the milk composition parameters, estimation of fat percentage in milk was performed by adapting the Gerber's butyrometer (ISO/R 488, 1983). The milk SNF percentage was estimated by lactometer method using the ISI formula (S.N.F. = CLR/4 + 0.25 (fat%) + 0.44). By adding the fat and SNF, total solid was determined. Udder and teat injuries were scored by self-developed scoring chart where 0 means no lesions in udder and teats, 1 indicates reddening of the udder and teat skin, 2 means laceration of udder and teats, 3 means open cuts and 4 indicates inflamed udder and teats with multiple cuts. Lying time (min/d) was calculated with the help of camera recordings and manual periodical scanning as per requirement. The hygienic condition of experimental cows were scored using 0–3-point scale of Hultgren and Bergsten (Reference Hultgren and Bergsten2001) at weekly interval during morning hours before grooming and milking, so that, the animal could be exposed to the floor surface at least for 12 h.
Statistical analysis
Data were analysed using SPSS software (Version 16.0) using descriptive statistics, one way ANOVA and a general linear model (GLM) multivariate method for analysis of variance. The conversion of SCC logarithms (Log10) was done to normalise the wide variation of data distribution. The following model was used
$$Y_{ijk} = {\rm \mu } + H_i + S_j + ( {{\rm HS}} ) _{ij} + e_{ijk}\eqno , \;$$Where,
μ = Overall mean, Hi = Effect of ith housing system (i = 1,2),
Sj = Effect of jth season (j = 1,2), (HS)ij = Interaction between ith housing and jth season,
eijk = Random error of observation
The Scheffe test was used to compare the least-square means of significant effects and the levels of significant mean differences were set at P < 0.05 and P < 0.01.
Results
The overall morning and evening rectal temperature, pulse rate and respiration rate were significantly (P < 0.01) higher in T 0 group cows (morning: 100.86 ± 0.04, 64.66 ± 0.35 and 22.32 ± 0.61, respectively, and evening: 101.38 ± 0.05, 69.32 ± 0.34 and 26.93 ± 0.67, respectively) as compared to T 1 group cows (morning:100.57 ± 0.03, 63.77 ± 0.25 and 18.75 ± 0.34, respectively, and evening: 101.20 ± 0.03, 67.74 ± 0.23 and 22.53 ± 0.37, respectively). A significant difference was observed between ceiling surface temperature (°C) of the covered area between the control (T 0) and modified (T 1) yards. During the winter season, the temperatures in the traditional shed (27.32 ± 1.56 and 29.06 ± 1.42) were significantly higher than the modified shed (19.46 ± 0.83 and 22.72 ± 1.06) at the peak hours (10:00–11:00 am and 2:00–3:00 pm) of the day (P < 0.01). However, in the control (T 0) group, temperature was significantly lower than the modified (T 1) shed in the evening (5:00–6:00 pm) time (P < 0.01). During the summer season, the temperature (˚C) was significantly (P < 0.01 and <0.05, respectively) higher in T 0 (36.53 ± 1.22 and 37.49 ± 1.51, respectively) shed compared to T 1 (27.41 ± 1.38 and 32.33 ± 1.73, respectively) shed during peak hours (10:00–11:00 am and 2:00–3:00 pm) of time in a day. It was observed that THI was significantly higher during summer (80.3 ± 0.34) as compared to winter season (65.3 ± 0.56). The time (min/d) cows spent resting in a lying position were significantly (P < 0.05) higher in the modified shed (683.51 ± 16.50) than the control shed (634.71 ± 9.39). Injuries to the udder and teats (0–4 point scale) were negligible in T 1 (0.86 ± 0.10) and less than in T 0 (2.13 ± 0.09).
The milk yield (kg) of the groups (Fig. 1) showed that the control group had a higher yield (11.92 kg/d) compared to the treatment group (11.54 kg/d) in the initial month of the experiment (P < 0.01). In later months (January onwards), milk yield of cows kept in the modified shed increased and the milk yield of cows in the treatment group was greater than that of the control group. Overall, the milk yield of the T 1 group was significantly (P < 0.01) higher (by 0.38 kg/d/cow) than in the T 0 group. Detailed statistical analysis is given in online Supplementary Table S3.
Fig. 1. Daily milk yield (kg) in Jersey crossbred cows in traditional housing (control group in blue diamonds) and housing improved by provision of heat-insulating thatch under the asbestos roof and a sand bed (treated group in red squares). Values are mean ± se, n = 10 cows per group.
The effects of roof ceiling modification and soft flooring on milk composition of Jersey crossbreed cow in different seasons have been presented in Table 1, with detailed statistical analysis in online Supplementary Table S4. In the T 1 group, there was a significantly higher (P < 0.01) fat and total solid percentage than T 0, but no significant difference was found between seasons for fat percentage. The total solid percentage was significantly higher in the winter season (P < 0.01). The per cent SNF did not differ significantly between the T 0 and T 1 groups, however it was significantly higher in winter than in summer.
Table 1. Milk fat (%), solids not fat (SNF, %) and total solids (%) in Jersey crossbred cows in different treatment groups and seasons
Values are mean ± se. N = 10 cows per group. Means with different superscripts differ significantly (lower case P < 0.05, upper case P < 0.01) within rows (treatment effect) or columns (season effect).
The modified California mastitis test (MCMT) was significantly higher (P < 0.05) in the T 0 group than T 1 (Table 2 and online Supplementary Table S5). There was no effect of season on udder health of experimental animals. MCMT grade is an udder health indicator and it is revealed from the current study that cows housed on sand bedding were less susceptible to mastitis (P < 0.05) compared to cows on the concrete floor (T 0). SCC and Log10 SCC in the different seasons are also presented in Table 2. Although there was no significant difference between the two groups in either parameter, the overall values were lower in the T 1 compared to the T 0 group. There was little effect of season. Detailed statistical analysis is given in online Supplementary Table S6.
Table 2. Modified California mastitis test (MCMT), somatic cell count and Log10 SCC of milk in Jersey crossbred cows in different groups and seasons
Values are mean ± se. N = 10 cows per group. Means with different superscripts differ significantly, P < 0.05.
Discussion
Decreased milk yield, changes in milk composition, increase of MCMT grades and somatic cell count during heat stress and resting discomfort in dairy cows are well recognised. However, a detailed study to improve the milk production, milk composition and udder health through comprehensive housing modifications of floor and roof materials has been less reported in tropical climatic conditions. The hypothesis that housing modifications of dairy cows can improve the production performance in different seasons could be clearly confirmed in our study. Improved production performance and better udder health was found in the modified shed. This is of high importance in understanding the role of different housing materials in relation to better well being and production performance during different seasons, particularly in Jersey crossbred cows maintained in tropical climatic conditions. Summer in tropical countries such as India can lead to extreme temperatures, in excess of 30 °C, which results in production losses for dairy cattle. This study revealed significantly lower temperatures in sheds with thatch underneath the traditional asbestos roofing, which is similar to other comparative studies (Sivakumar et al., Reference Sivakumar, Suraj, Yasotha and Phukon2017). The probable reason is the lower thermal conductivity of thatch, which creates a better thermo-comfortable environment for cows. Asbestos sheets emit radiation when they are heated up during peak hours of summer. This has the potential to raise the surface temperature of the animal and negatively alters the microclimate of the shed. However, in the control (T 0) group, temperature was significantly lower than the modified (T 1) shed in the evening which could be due to the rapid heat loss by asbestos shed, in contrast to the slow release of heat by thatch type sheds. The regular replacement of roofing materials might not be technically feasible or economically viable due to the heavy capital cost in permanent animal housing structures. It would, therefore, be useful to make appropriate roof modifications to the existing permanent structures, such as thermal insulation, rather than to change the entire roof, which is not only economical but also improves the efficiency of the existing roof (Mandal et al., Reference Mandal, Sahu, Mandal, Chatterjee, Bhakat, Rai, Karunakaran and Dutta2018).
The digestion of roughage produces a large amount of metabolic heat which increases the body temperature of cows. As temperature increases in the summer there is a concurrent increase of body temperature, and as a result cows decrease their feed intake to reduce heat stress. This leads to a gradual decline in milk production and a change in the content of milk. Modifications to animal housing to minimise the thermal stress during summer leads to increased production levels in dairy cattle by protecting them from severe temperature stress (Mandal et al., Reference Mandal, Bhakat and Dutta2021).
The choice of bedding material can also affect the ability of the animal to express natural behaviour, which also impacts animal health and production (Calamari et al., Reference Calamari, Calegari and Stefanini2009). Compared to cows housed on other bedding materials, cows housed on sand have longer lying times (Sahu et al., Reference Sahu, Mandal, Hussain Dar, Podder and Gupta2021) in both summer and winter seasons. Increased lying time has several positive effects on milk production of dairy cows by reducing stress. Rumination is positively correlated with lying time in cows. The results of the present study are in agreement with the reports of Bharambe et al. (Reference Bharambe, Patil and Burte2013) that in a thatched-roof shed, the average total solids and milk fat of crossbred cows were significantly higher than in the white painted and asbestos roofed shed.
The outcome of the MCMT and SCC grades indicated that the health of the udder on the sand floor was better than on the concrete floor. The SCC outcome of the present study is consistent with Bhakat et al. (Reference Bhakat, Chatterjee, Mandal, Karunakaran, Mandal, Garai and Dutta2017). The likely reason could be due to low environmental stress reducing udder and teat injury (Geishauser et al., Reference Geishauser, Querengasser, Nitschke and Sorbiraj1999), thus preventing mastitis and promoting better udder health (Elbers et al., Reference Elbers, Miltenburg, De Lange, Crauwels, Barkema and Schukken1998).
In conclusion, housing modifications by thermal insulation using thatch under the asbestos roof and provision of soft sand bed flooring created favourable environments for the crossbred Jersey cows which was indicated by increased milk yield, improved milk composition, and enhanced udder health. The asbestos sheet and concrete floor provided cows with less comfort, and it was evident through loss of production and poor udder health. It could be concluded that in both the summer and winter seasons, thatch ceiling under asbestos roofs and soft sand flooring could be used as important shelter improvement measures to improve productivity and udder health. However, a caveat needs to be recognised, in that the research was conducted in one housing facility of each type, traditional and improved. Statistical analysis was performed at cow level, with the positive effects being seen across 10 individuals in each housing type. The conclusions should be replicated in additional research employing more housing facilities of each type. In addition, the durability of materials and daily maintenance cost of sand bed needs to be further investigated.
Supplementary material
The supplementary material for this article can be found at https://doi.org/10.1017/S0022029922000826
Acknowledgements
The authors are grateful to Director, ICAR-NDRI, Karnal and Head, ERS-Kalyani of ICAR-NDRI, for providing necessary facilities. We would also like to thank Dr Ellen Williams, who assisted with manuscript editing as part of the International Society for Applied Ethology English Language Help Service.
