ROLE OF HEAT STRESS AND MANAGEMENTAL PRACTICES ON THE PRODUCTIVITY OF INDIAN DAIRY ANIMALS AND THEIR MITIGATION STRATEGIES
Y.Nagendra Reddy1and G Shalini
Ph.D Scholar, Department of Animal Reproduction, Gynaecology and Obstetrics, CVAS, Mannuthy, Thrissur, Kerala
Corresponding author mail id: nagendrareddyy93@gmail.com
INTRODUCTION
India has the largest dairy herd in the world which comprises of water buffalo and other native and crossbred cattle. It is also the world’s greatest producer and consumer of milk. As per 19th livestock census India ranks second in cattle population (190.9 million) and first in buffalo population (108.7 million) (Goi, 2014). In India and other developing countries about 70% of the milk producers are smallholder and landless farmers, dairy farming has become more essential and contributes significantly for sustaining their livelihood and also to the rural economy (Otte et al. 2012). According to FAO, there will be a 74% and 58% increase in the global demand for milk by 2050 compared to dairy and meat, respectively, with a significant portion of this demand coming from developing nations. Improving production efficiency through the prudent use of available feed resources is the major challenge in meeting the current and future demand for milk and given the genetic potential of the livestock, its production depends primarily on managerial practices, which exhibit high variation across agro-climates and reduced milk production by 50% during the summer. Compared to native cattle, exotic and crossbred animals are more vulnerable to the negative effects of heat stress. This article focuses mostly on the issues that dairy animals face including heat stress, nutrition and production management as well as the methods used to address these issues.
PRODUCTIVE PARAMETERS OF DAIRY ANIMALS
Average daily milk yield (lit):
The dairy animals’ milk yield is a crucial indicator of their performance. Average daily milk of Buffalo, CB cow, Indigenous cow, were as 5.75±0.65, 7.55±0.74 and 3.27±0.3 litre/day/animal respectively (Meena et al., 2013).
Lactation length (Days):
One of the best measures of the performance of dairy cows is the length of their ideal lactation. lactation length of Buffalo, CB cow, Indigenous cow, was 276±14, 274±16 and 294±18 days/ animal respectively (Meena et al., 2013). The average lactation length for a crossbred cows was approximately 305 days, which is considerably good
Lactation milk yield (Lit):
Lactation milk yield has positive relation with the overall performances of dairy animals. Lactation milk yield of Buffalo, CB cow, Indigenous cow was 1587.60±113, 2091.35±145 and 964.65±98 litre/ animal respectively (Meena et al., 2013).
Peak yield (Lit):
Average peak milk yield of Buffalo, CB cow, Indigenous cow, were 8.56±0.85, 10.42±1.42 and 5.51±0.53 litre/animal respectively. More the peak yield of animal higher will be its cost in market and higher the returns (Meena et al., 2013).
CHALLENGES AND MITIGATION STRATEGIES:
Productivity of dairy animals is affected predominantly by heat stress, management practices and nutritional status.
- HEAT STRESS
The most common index of heat stress (temperature humidity index or THI) is calculated from the temperature and relative humidity (RH). Animals lose feed energy by panting and sweating when exposed at high ambient temperature. During summer the milk production is reduced to 50% and especially crossbred / exotic animals are more prone to the heat stress losses as compared to indigenous cattle. According to Armstrong (1994) heat stress in animals leads to Reduced feed intake, increase water intake, change in the metabolic rate / maintenance requirement, increased evaporative loss, changes in blood hormones concentrations, increase body temperature.
| THI | Stress level | Effects |
| <72 | None | |
| 72-79 | Mild | Dairy cows adjust by seeking shade, increasing respiration rate, dilatation of blood vessels. The effect on milk production is minimal |
| 80-89 | Moderate | Both saliva and respiration rate increases, feed intake reduces and conversely water intake increases, milk production and reproduction decreased |
| 90-98 | Severe | Cows become uncomfortable and there is marked increased in respiration and saliva production, milk production and reproduction will be markedly decreased |
| >98 | Danger | Potential cow deaths occur |
Strategies to reduce heat stress
Productivity loss during summer can be reduced substantially by adopting the following heat stress management coupled with good health management i.e., Proper summer-oriented housing, animal cooling system, development of breeds tolerant to heat stress, high energy feeding.
The cow sheds in Indian conditions should be designed to reduce the heat load because heat stress cause more damage to animals compared to winter. Animal can tolerate winter condition up to 15C (C: degree Celsius) without any difficulty but the temperature above 30C result in drop in milk production and breeding efficiency. In the animal shelter ideal micro environment i.e., temperature and humidity level should be around 15 to 25 C and 10-12 mm Hg (Pandey et al., 2008). A shed with a longitudinal axis that runs east-west is cooler than one that is oriented north-south. The mean and lowest temperatures in closed sheds were much higher than in open sheds so open sheds have an advantage over closed sheds. In order to reduce heat load, the minimum roof height should be 10.0 feet. The height of shelter in hot climate should be between 3.0 – 5.0 m. A height less than 3.0 m interferes with proper ventilation and result in reduced convective heat loss from animals. The roof’s shape might be “A” shaped, sloping, or flat. In hot climates, a “A” shaped roof is unquestionably preferable to a flat roof. Hay or straw, galvanised steel, plywood, and other polymers can be used as roofing materials. Asbestos sheet as top layer in double roof shelter is more effective than others (Pandey et al., 2008)
MANAGEMENT PRACTICES:
This included the practices with respect to breeding, feeding, milking, housing, health care.
BREEDING:
Breeding is crucial to the current growth of the livestock industry because it produces enough improved germplasm seed stock to support the production of animal goods.AI helps in extensive use of elite males. However, natural service is also practised in several parts of India (Gupta et al., 2007). The concept of sexed semen has introduced to produce elite female animals everywhere in India currently. Now a days concept of assisted reproductive technologies came into force that provides transfer of embryo to oestrous animal (recipient animal) on 7th day of heat rather than insemination of semen. Among all these assisted reproductive technologies genetic merit of the animal is good and rapid through artificial insemination when compared with other technologies (Ferre et al., 2020).
FEEDING:
Balanced feeding is essential to increase the productivity of animals. Feeding balanced ration did not alter body weight of dairy cows but after nutrient balancing, there was increase in intake of nutrients and subsequent increase in milk production.
Fig.1 %deficiency/excess of nutrients in %cattle study population before balanced feeding
(DM, CP, TDN and ME) (Deen et al., 2018)
The role of balanced feeding on milk production are depicted in fig 2 and nutrition parameters alters (Table1) with increase in feed conversion ratio in dairy animals after balanced feeding (Table 2).
Fig. 2. Effect of balanced feeding on milk yield in cattle in field condition (Deen et al., 2018)
Table 1: Effect of balanced ration balancing on body weight and nutrient intake (Deen et al., 2018)
| Particulars | Baseline | After balanced feeding |
| Bodyweight(kg) | 324.22±11.95 | 325.90±11.79 |
| DMI (kg/day) | 8.49a±0.61 | 9.93b±0.28 |
| CPI (kg/day) | 0.93a±0.09 | 1.17b±0.04 |
| Calcium intake (g/day) | 25.38a±2.19 | 50.78b±1.93 |
| Phosphorus intake (g/day) | 12.50c±0.90 | 26.90d±0.98 |
a, b Means with a different superscript in a row differ significantly (P<0.05)
c, d Means with a different superscript in a row differ significantly(P<0.01)
Table 2: Feed conversion efficiency and economics of milk production (Deen et al., 2018)
| Particulars | Baseline | After balanced feeding |
| FCE (kg FCM/kg DMI) | 1.06c ± 0.05 | 1.12d ±0.04 |
| Cost of ration/kg milk yield (Rs) | 15.70b ±0.89 | 12.80a ±0.91 |
| Cost of ration/day (Rs/day) | 97.00a ± 7.65 | 103.90b ±4.97 |
| Return from sale of milk (Rs/d) | 199.20c ± 11.36 | 250.00d ±10.11 |
(a, b) Means with different superscripts in a row differ significantly (p <0.05)
(c, d) Means with different superscripts in a row differ significantly (p<0.01)
Milking of animals:
Nearly 97% households adopted the practice of washing the udders before milking the animals and hand milking was practised widely in rural areas but in commercial dairy farms machine milking is practised. There is no vary in Milk yield in both the techniques but knuckling technique of hand milking should be avoided to prevent damage to the udder and preventing further infections (Gupta et al., 2008)
DISEASES:
A lot of metabolic diseases like milk fever, mastitis, downer cow syndrome etc., and also systemic diseases leads to decline in milk production in dairy animals. These diseases are common during the transition period and can be diagnosed and treated but mastitis is a most prevalent disease of livestock, which is challenging to both field veterinarians and dairy farmers. Bovine Mastitis is a common disease accompanied by physical, chemical, pathological and bacteriological changes in milk and glandular tissue in dairy cows (Samad, 2008). Researchers and dairy farmers are distracted by the financial losses associated with mastitis, which is the most expensive disease due to significant losses in milk quality and quantity since it damages udder tissue irreversibly and occasionally results in fatalities. (Radostits et al., 2000). Heavy losses can occur due to treatment costs, discarding of milk with antibiotics, lower price for less quality milk and death from severe inflammations (Radostitis et al., 1994).
Antibiotics are classified according to World Health Organization (WHO) and the American Food and Drug Administration (FDA) categorize fluoroquinolones, cephalosporins of the third and fourth generation and (partially) macrolides as antibiotic with (highest priority) critical importance for human medicine. Prophylactic measures include reducing the number of new infections (NI) and pathogen transmission by streamlining management guidelines, making judgements on segregation and culling, and minimising the worsening of subclinical to clinical mastitis. Trevisi et al. (2014) increase in immunocompetence and disease resistance by proper use of immunomodulators such as lactoferrin promises a substantial reduction in AMU in dairy cows. The employment of bacteriophages and their products effectively inhibit the growth of streptococci in milk illustrating their potential for clinical mastitis treatment (Schmelcher et al., 2015; Yang et al., 2015). Further approaches comprise the application of a platelet concentrate (Lange- Consiglio et al., 2014) and the possible utilization of epigenetic mechanisms to enhance immune responses (Chang et al., 2015) or natural compounds (e.g., Rhodomyrtus tomentosa leaf extract) which exhibit inhibiting abilities against mastitis causing pathogens in vitro (Mordmuang & Voravuthikunchai, 2015). Further dairy farmers use homeopathy as alternate to conventional treatment on herd level and individual cow level for reducing AMU, that is allowing farmers to meet the organic principles (Hektoen, 2004; Hektoen et al., 2004; Orjales et al., 2016).
Udder health management is a continuous improvement process so further improvement may enhance reduction in AMU but in a gradual and time-consuming manner. Udder health management in the dry period is important to enables good start to the lactation period and most of the infections existing at parturition occur during the dry period (Pieper et al., 2013). Damaged or senescent epithelial cells are physiologically replaced (Capuco et al., 1997). Dry cow therapy (DCT) is highly efficient so that most intramammary infections heal up because key component of dry cow mastitis management is the use of antibiotics. DCT essentially has two functions, the elimination of existing IMI at dry- off and the prevention of new IMI during the dry period (Bradley & Green, 2004). DCT has been shown to achieve a 1.78 times higher cure rate when compared with self- cure in untreated quarters (Halasa et al., 2009)
CONCLUSION
In order to increase the productivity of dairy animals the common causes for reduction in milk production like heat stress, nutritional stress and diseases can be countered not only at the individual animal level but also at the herd level by dry cow therapy, proper managemental practices like proper housing orientation, breeding, feeding to increase feed conversion ratio, milking practices and treatment of systematic and metabolic diseases so that milk production can be increased and can keep the India on top at the global stage as a highest milk producing and consumer country.
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