The domestic water buffalo belongs to the species Bubalus bubalis. All European buffaloes are considered to be of the same breed, the Mediterranean, which includes those of Italy, Egypt, Greece, Bulgaria, Syria and Turkey (Han et al. Reference Han, Lee, Zhang and Guo2012). Buffalo are the second most valuable species in the world for milk production (Han et al. Reference Han, Lee, Zhang and Guo2012; Coroian et al. Reference Coroian, Erler, Matea, Miresan, Raducu, Bele and Coroian2013). However, buffalo are low milk producers compared to the dairy cow breeds reared in Egypt, but their milk price is approximately three times that of dairy cattle (Rosati & Van Vleck, Reference Rosati and Van Vleck2002). Customers are now looking for a product with desirable and efficient properties. Thus, milk prices have been based on composition and the dairy producers have altered their farming management to produce milk with high protein, fat and solids. This has increased the need for studies that aim to increase milk's valuable components without altering its industrial quality.
The Italian buffalo is considered the best in the world, it has the highest milk production and fat percentage (Varricchio et al. Reference Varricchio, Di Francia, Masucci, Romano and Proto2007), good genetic make-up and facilitates application of practical technologies and monitoring of hygiene, thus achieving good quality products. The consumption of buffalo milk in Egypt has increased drastically, and is currently considered the second source of milk production (45·86%, FAOSTAT, 2015). Improving buffalo milk production (i.e. quantity and quality) works as a tool for improving the quality of life especially for family farmers in charge of this animal in developing countries (Aggarwal & Upadhyay, Reference Aggarwal, Upadhyay, Aggarwal and Upadhyay2013). Improving milk yield is not straightforward, as selecting for a single trait such as quantity might lead to lower milk quality and/or reproductive efficiency (Barros et al. Reference Barros, Oliveira, Hurtado-Lugo, Aspilcueta-Borquis and Tonhati2014). On the other hand, the heritability estimate for milk yield was moderate, suggesting that this trait will respond to direct mass selection (Malhado et al. Reference Malhado, Malhado, Ramos, Carneiro, Souza and Pala2013). With this in mind producers had attempted to improve this trait, as well as reproductive traits, of their Egyptian buffaloes by crossbreeding the pure Egyptian buffaloes (EB) with the Italian buffaloes, using imported Italian buffalo semen with proven breeding values.
In tropical and subtropical areas, high environmental temperature, relative humidity, solar radiation and heat stress are the most crucial constraint on animal production (Marai et al. Reference Marai, Daader, Soliman and El-Menshawy2009). The weather in Egypt is described as moderate to high summer temperatures coupled with moderate humidity levels. Dairy cattle can be significantly affected by heat stress, and severe hot and humid weather such as that found in Egypt can affect welfare, health and survival ability as well as reproductive and productive performances (Dunn et al. Reference Dunn, Mead, Willett and Parker2014). Nonetheless, buffaloes have a higher ability to withstand undesirable environmental conditions and a notable longevity (approximately 10 years of production; Dunn et al. Reference Dunn, Lallo, Carnadovan and Ram2013). The buffalo exceeds the cow's ability to acclimatise in hot and humid regions of muddy and swampy lands. Therefore, buffaloes do well in extremely hot conditions of tropics and subtropics (Marai & Habeeb, Reference Marai and Habeeb2010). The adaptability estimates for buffaloes vs Friesian cows were 89·1 and 82·9%, respectively (Marai et al. Reference Marai, Daader, Soliman and El-Menshawy2009). Temperature humidity index (THI) is commonly used all over the world to evaluate the consequence of temperature and relative humidity on animal performance (Akyuz et al. Reference Akyuz, Boyaci and Cayli2010). To our knowledge, scant and limited information is available in the literature regarding the associations among THI, milk yield and composition with different buffalo genetic types (pure Egyptian buffalo and their crosses with Italian) and the performance difference between them, especially under subtropical conditions. Therefore, this study aimed to compare the milk yield and composition of different genetic types (EB, F1 and BC) and investigate the impact of THI on milk yield and composition under subtropical Egyptian conditions.
Materials and methods
Animals and management
This study was carried out on lactating buffalo reared by a farm in Masr-Ismallia El Sahrawy Road, Ismallia, Egypt. The herd consisted mainly of 516 lactating buffalo; 152 pure Egyptian buffalo (EB), 176 F1 crosses (50% pure Egyptian buffalo and 50% Italian buffalo) and 188 back cross (BC; 75% pure Egyptian buffalo and 25% Italian buffalo). Buffalo were kept loose in a free-stall yard under partially roofed sheds to protect them from extremes of hot and/or cold weather. They were kept in separate pens according to their level of milk production, with free access to drinking water. All animals were fed the same mixed ration (MR 50 kg/daily). The ration was mixed daily and formulated to meet the predicted requirements of energy, protein, minerals and vitamins for reproductive status and milk yield. The MR was analysed by wet chemistry methods and its primary analysis include 12·5% crude protein, net energy for lactation (Mcal/kg = 2·4), 31% neutral detergent fiber and 19% acid detergent fiber. Buffalo were fed with Egyptian clover berseem (Trifolium alexandrinum), during December to May and Alfalfa hay during the rest of the year. Animals were machine milked three times daily at 04:00 am, 12:00 pm and 08:00 pm. Milk yields were recorded individually for each buffalo at each milking. This study was carried out under the Animal Care and Welfare Committee of Zagazig University, Egypt (ANWD-206). Milk samples of 50 ml were collected in clean sterile polypropylene containers from the three consecutive milking and pooled at the mid of lactation for determining the milk composition (fat %, protein %, total solids %, solids not fat %, ash % and lactose %) using infra-red spectroscopy (Milko-Scan 133B; N. Foss Electric, DK 3400 Hillerod, Denmark). Samples were transferred on dry ice and stored at −80 °C until analysis.
Metrological data
Temperature-humidity index (THI) has been developed as a weather safety index to monitor and decrease losses associated with heat stress. It is a distinctive value coupled the effects of air temperature and humidity. The daily ambient temperature and relative humidity in the farm area were obtained from the nearest meteorological station, approximately 37 km way. The collected data were used to estimate the maximum daily THI (Kendall & Webster, Reference Kendall and Webster2009) as follows:
$${\rm THI} = (1 \!\cdot\! 8{^\ast}{\rm AT} + 32)-\left( {\left( {0 \!\cdot\! 55-0 \!\cdot\! 0055{^\ast}{\rm RH}} \right) \times \left( {1 \!\cdot\! 8{^\ast}{\rm AT}-26} \right)} \right),$$where AT = ambient temperature (°C), RH = relative humidity (%).
The monthly average temperature, relative humidity and THI varied with season as expected with maximum values between July and September and a nadir in December and January. To investigate the impact of THI on milk yield and composition, buffalo were classified according to the THI at calving day into low (months with average ≤70 THI), moderate (months with average >70 and ≤80 THI and high (months with average >80 and up to 85 THI: Gantner et al. Reference Gantner, Mijic, Kuteroval, Solic and Gantner2011).
Statistical analysis
Statistical analysis was carried out through a generalised linear model using SAS statistical system Package (SAS, 2008). The data were normally distributed. The statistical model was adjusted for the following effects; fixed effects of THI, genetic groups and parity, while the dependent variables were milk yield (305 d), milk/d, peak of milk yield, days to attain peak yield, fat %, total protein %, total solids %, solids not fat %, lactose % and ash %, also with buffalo age as covariate. The comparison of means among the groups was performed with Duncan's multiple range tests. Values were considered significant at P ≤ 0·05.
Results
The effect of different genetic types on milk yield and composition
Crosses of Egyptian and Italian buffalo (25 and 50% Italian buffalo) have a significantly higher milk yield (2511·59 and 2408·48 kg, respectively) than pure Egyptian buffalo (2276·65 kg). The average daily milk yield was highest in the BC. They yielded 1·05 and 0·87 kg of milk/d more than EB and F1, respectively. The peak of milk production was higher in both crosses (14·74, BC and 14·56, F1 kg) when compared with the Egyptian buffalo (13·69 kg). EB had the highest significant milk fat %. They produced 0·65% more fat than that of both crosses. There was no significant difference in the days to attain peak milk production, milk protein, solid not fat, total solids, lactose and ash among the three different genetic types (Table 1).
Table 1. Effect of different Genetic types of buffalo on milk yield and composition
† EB: pure Egyptian buffalo.
‡ F1: crossbred Egyptian buffalo 50% X Italian buffalo 50%.
§ BC: backcross of Egyptian buffalo 75% X Italian buffalo 25%.
¶ RSD: residual standard deviation.
†† SNF: solid not fat.
‡‡ TS: total solids.
a,bValues within a row with different superscripts differ significantly.
The effect of THI on milk yield and composition
In EB, there were no significant differences in milk yield and days to attain the peak of milk yield between low (2212·63 kg and 34 d, respectively) and high (2331·92 kg and 40 d, respectively) THI (Table 2), while in F1 milk yield and days to attain the peak of milk yield significantly decreased from 2463·83 kg and 42 d in low THI to 2255·90 kg and 36 d in high THI, respectively (Table 3). But, there was no significant difference between low and moderate THI, and between moderate and high THI in BC (Table 4). The average daily milk yield was lower only in F1, in which decreased from 10·33 kg (low THI) to 8·38 kg (high THI) (Table 3). High THI reduced the peak milk production in the three genetic types. It decreased from 15·02 kg (low THI) to 13·72 kg (high THI); 15·24 kg (low THI) to 14·07 kg (high THI) and 15·52 kg (low THI) to 14·04 kg (high THI) in EB (Table 2), F1 (Table 3) and BC (Table 4), respectively. Milk fat and total solids % tend to increase in the high THI when compared with the lower one in the different genetic types, while no difference was detected for the other milk composition in the different genetic types between the three THI levels.
Table 2. Effect of temperature-humidity index (THI) at calving on milk yield and composition in pure Egyptian buffalo
† Low: THI ≤ 70.
‡ Moderate: THI, > 70 and ≤ 80.
§ High: THI over 80.
¶ RSD: residual standard deviation.
†† SNF: solid not fat.
‡‡ TS: total solids.
a,bValues within a row with different superscripts differ significantly.
Table 3. Effect of temperature-humidity index (THI) at calving on milk yield and composition in F1 (50% Egyptian X 50% Italian buffalo)†
† F1: crossbred Egyptian buffalo 50% X Italian buffalo 50%.
‡ Low: THI ≤ 70.
§ Moderate: THI, >70 and ≤80.
¶ High: THI over 80.
†† RSD: residual standard deviation.
‡‡ SNF: solid not fat.
§§ TS: total solids.
a,bValues within a row with different superscripts differ significantly.
Table 4. Effect of temperature-humidity index (THI) at calving on milk yield and composition in BC†
† BC: backcross of Egyptian and Italian buffalo (25% Italian buffalo).
‡ Low: THI ≤ 70.
§ Moderate: THI, >70 and ≤80.
¶ High: THI over 80.
†† RSD: residual standard deviation.
‡‡ SNF: solid not fat.
§§ TS: total solids.
a,b,cValues within a row with different superscripts differ significantly.
Discussion
Effect of different genetic types on milk yield and composition
The current study was conducted to assess the productive performance of the EB and their F1 and BC crossbred, under stressful subtropical conditions in Egypt and furthermore, to compare the adaptability of the crosses to such conditions in comparison to EB. Differences in the results of milk yield and composition in different buffalo populations around the world may be due to a variety of factors including: herds’ genetic makeup, size of the herds, environmental condition, managerial, hygienic-sanitary situation, feed quality, calving season and calving order (Macedo et al. Reference Macedo, Wechsler, Ramos, Amaral, Sousa, Resende and Oliveira2001; Fooda et al. Reference Fooda, Mourad and Gebreel2010; Araújo et al. Reference Araújo, Rangel, Fonseca, Aguiar, Simplício, Novaes and Júnior2012; Bhutkar et al. Reference Bhutkar, Thombre and Bainwad2014). In the current study, the milk yield of F1 and BC was higher than that of EB (5·79 and 10·32%, respectively) which supported the recent finding of Fooda et al. (Reference Fooda, Elbeltagy, Hassan and Awad2011) on a similar crossing. These results were compatible with the findings of others on pure Italian buffalo (Rosati & Van Vleck, Reference Rosati and Van Vleck2002). This might be due to the recently efficient genetic improvement in Italian buffalo and increasing their milk production (Borghese, Reference Borghese and Borghese2005). Moreover, the milk yield from EB in the current study was similar to the findings of Borghese (Reference Borghese and Borghese2005) who used the same Egyptian breed. The average daily milk yield ranged between 8·35–13·87 kg/buffalo/d in both pure Egyptian and Italian buffalo (Varricchio et al. Reference Varricchio, Di Francia, Masucci, Romano and Proto2007; Araújo et al. Reference Araújo, Rangel, Fonseca, Aguiar, Simplício, Novaes and Júnior2012; Morsy et al. Reference Morsy, Ebeid, Kholif, Murad, Abd EL-Gawad and El-Bedawy2014). The results of this study in the three genetic types were within this range, although the BC revealed higher daily yield when compared with EB and F1 (7·74 and 3·92%, respectively).
The peak milk yield is the highest daily milk production at any time in lactation. F1 and BC had a higher peak yield than EB (6·36 and 7·67%, respectively). However, all of them were in the range 8·14–11·30 kg reported by others (Hamid et al. Reference Hamid, Farooq, Mian, Syed and Jamal2003; Kianzad et al. Reference Kianzad, Seyyedalian, Hasanpur and Javanmard2013). The higher peak milk yield might be attributed to greatly productive animals and more efficient use of feed (Hamid et al. Reference Hamid, Farooq, Mian, Syed and Jamal2003). Bhutkar et al. (Reference Bhutkar, Thombre and Bainwad2014) stated that days to attain peak yield is a crucial factor which influences lactation yield, lactation length and shape of the lactation curve. A growing number of studies have found that the days to attain peak milk yield were in the second and towards the start of the third month (Sarubbi et al. Reference Sarubbi, Polimeno, Auriemma, Maglione, Baculo and Palomba2013). The results of this study were within this range. However, there was no significant difference between the different genetic types in this study, but BC had the highest milk yield and peak with longer days to attain the peak, which was compatible with the findings of Kianzad et al. (Reference Kianzad, Seyyedalian, Hasanpur and Javanmard2013). They found a positive correlation between peak milk yield and days to attain peak yield.
Fat % of EB in the present study was in agreement with the reported range (5·95–7·0%) by others on Egyptian buffalo (Macedo et al. Reference Macedo, Wechsler, Ramos, Amaral, Sousa, Resende and Oliveira2001), but was lower than the findings (7·99%) of other (Morsy et al. Reference Morsy, Ebeid, Kholif, Murad, Abd EL-Gawad and El-Bedawy2014). Fat% in F1 and BC was lower than that of pure Italian buffalo 7·9–8·69% (Rosati & Van Vleck, Reference Rosati and Van Vleck2002). The slightly higher fat % in EB might be due to the fact that the daily milk yield had a negative significant correlations with fat % (Barros et al. Reference Barros, Oliveira, Hurtado-Lugo, Aspilcueta-Borquis and Tonhati2014), demonstrating that direct selection for improving milk production would result in decreased the concentrations of fat (Bampidis et al. Reference Bampidis, Nistor, Skapetas, Christodoulou, Chatziplis, Mitsopoulos and Lagka2012). Thus, higher milk yield has a consequential dilution effect on fat concentrations (Quist et al. Reference Quist, LeBlanc, Hand, Lazenby, Miglior and Kelton2008). The three genetic types in this study had the same protein % and TS % which were compatible with the findings of other in Egyptian buffalo (Morsy et al. Reference Morsy, Ebeid, Kholif, Murad, Abd EL-Gawad and El-Bedawy2014), Mediterranean buffalo (Macedo et al. Reference Macedo, Wechsler, Ramos, Amaral, Sousa, Resende and Oliveira2001; Varricchio et al. Reference Varricchio, Di Francia, Masucci, Romano and Proto2007; Bampidis et al. Reference Bampidis, Nistor, Skapetas, Christodoulou, Chatziplis, Mitsopoulos and Lagka2012) and Murrah buffalo (Araújo et al. Reference Araújo, Rangel, Fonseca, Aguiar, Simplício, Novaes and Júnior2012; Barros et al. Reference Barros, Oliveira, Hurtado-Lugo, Aspilcueta-Borquis and Tonhati2014), while it was lower than the range reported in pure Italian buffalo (Rosati & Van Vleck, Reference Rosati and Van Vleck2002).
Effect of THI levels on milk yield and composition of different genetic types
There have been conflicting results on the effect of calving season on milk yield. While some authors have found no difference (Fooda et al. Reference Fooda, Elbeltagy, Hassan and Awad2011; Araújo et al. Reference Araújo, Rangel, Fonseca, Aguiar, Simplício, Novaes and Júnior2012), others have reported that milk yield decreased under hot environmental conditions (Marai et al. Reference Marai, Daader, Soliman and El-Menshawy2009). However, our results were in accordance with the majority of studies that have found that THI had a negative impact on milk yield. Improved feeding and management may be conquering the conflicting results which caused by stress factors. Livestock performance might be influenced by THI (over the thermoneutral zone of dairy cows) in several ways: Firstly, fodder deficiency (intake, quality and utilisation), disturbances in metabolism, enzymatic reactions and hormonal secretions (Young, Reference Young2002). Secondly, animal struggling in losing heat will decrease its heat production by depression of the feed intake (Mader & Davis, Reference Mader and Davis2004). Thirdly, heat stressed cows rely on glucose for body energy requirements, thus a lesser amount of glucose is directed to the mammary gland and consequently lowered the milk production (Aggarwal & Upadhyay, Reference Aggarwal, Upadhyay, Aggarwal and Upadhyay2013). Fourthly, heat stress causes vasodilatation with amplified blood flow to skin surface, high rectal temperature and decreased metabolic rate, which associated with negative impacts on production and reproduction in dairy animals (West et al. Reference West, Hill, Fernandez, Mandebvu and Mullinix1999).
EB and BC revealed some evidence of robustness at the different THI levels under subtropical conditions. Their daily milk yield did not change under different levels of THI, while in F1 it decreased by 18·88% from low to high THI. This result was compatible with the results of Pawar et al. (Reference Pawar, Kumar and Narang2013). They concluded that heat stress lowered daily milk yield by 18·2%. This may be due to the fact that BC had a higher Egyptian blood percentage, therefore adapted well under hot Egyptian environments. There have been conflicting results on the effect of THI on milk composition. While some authors have found no differences (Araújo et al. Reference Araújo, Rangel, Fonseca, Aguiar, Simplício, Novaes and Júnior2012), others have reported that milk fat and TS% decreased under hot environmental condition (Bernabucci et al. Reference Bernabucci, Basiricò, Morera, Dipasquale, Vitali, Cappelli and Calamari2015). However, in the current study the THI had a negative impact on fat and TS% which were comparable to the study performed by Coroian et al. (Reference Coroian, Erler, Matea, Miresan, Raducu, Bele and Coroian2013). This may be due to milk yield that was negatively correlated with fat and TS (Khosroshahi et al. Reference Khosroshahi, Rafat and Shoja2011). Moreover, heat stress had a negative effect on the secretary function of the udder (Silanikove, Reference Silanikove1992). Most of the milk compositions (protein, SNF, lactose and ash) were not different under different levels of THI and this was in accordance with other studies (Khosroshahi et al. Reference Khosroshahi, Rafat and Shoja2011; Bampidis et al. Reference Bampidis, Nistor, Skapetas, Christodoulou, Chatziplis, Mitsopoulos and Lagka2012). This may be an indication for the satisfactory management conditions in the farm all over the year (Marai & Habeeb, Reference Marai and Habeeb2010; Araújo et al. Reference Araújo, Rangel, Fonseca, Aguiar, Simplício, Novaes and Júnior2012; Bampidis et al. Reference Bampidis, Nistor, Skapetas, Christodoulou, Chatziplis, Mitsopoulos and Lagka2012).
Consumption of buffalo milk in Egypt has been increasing and the improvement of dairy buffalo is necessary for an efficient production. Consequently, EB crossed with Italian buffaloes, such as BC, tend to be the best in milk yield, average daily milk and peak yield with evidence of robustness under sever hot condition which are approximately similar to that of EB. Therefore, it is recommended to encourage producers to increase the number of BC animals in their farm for improving the milk production to fulfil the demand of Egyptian markets.
The author wishes to thank the owner of the farm, Ismailia Road, Cairo for allowing me to collect the data. I greatly appreciate the help of veterinary doctor Mohamed El-Sayed, manger of the farm in collecting and managing the data.
