Effects of  diet preparation and improved physical environment  on milk production and physiological  parameters of dairy cattle.

Duong Nguyen Khang and T R Preston

Nong Lam University, Thu Duc, Vietnam
duongnguyenkhang@yahoo.com

Abstract

Forty crossbred cattle (Holstein x LalSind) weighing on average 480 kg were allocated at random to 4 treatments in a 2*2 factorial arrangement.  The first factor was “Mixed Diet - MD”, consisting of Panicum grass, concentrate, brewery waste, alfalfa hay and sugar cane juke; “Separate Diet - SD”, including the same feedstuffs supplied separately. The second factor was “temperature-humidity improved environment - IE”, consisting of sprayed water and air fan and NIE (normal conditions). There were thus 4 treatments with 10 replications by dairy cows in a MD-IE, SD-IE, MD-NIE and SD-NIE. The diets were supplied ad-libitum during 4 months experimental period. The results showed that there were differences in dry matter intake of feedstuffs between treatments (P>0.05). The higher total dry matter intake was observed for treatment “temperature-humidity improved environment” and “Mixed Diet”. The highest total dry matter intake was observed for treatment MD-IE, with 3.12 kg DM/100 kg LWt/day, followed by treatments SD-IE, MD-NIE and SD-NIE, with 2.85, 2.95 and 2.66 kg DM/100 kg LWt/day, respectively. The milk yield on treatment MD-IE was greater than on treatments SD-IE, MD-NIE and SD-NIE (P<0.001). The highest milk yield was observed for treatment MD-IE, with 9.23 kg, followed by treatments SD-IE, MD-NIE and SD-NIE, with 7.45, 9.17 and 7.39 kg, respectively. There were non-significant differences in the body temperature, heart rate and breath rate among treatments.

Key words:  Dry matter intake, humidity, respiration, THI, temperature,

 

Introduction

Dairy production in Vietnam is a recent development and is mainly based on crossbred cattle (Holstein x Sindhi). Dairy cattle and milk production development are one of the priority strategies of the national food and feedstuff programme in Vietnam. In 2003 the population of Vietnam was 80 millions inhabitants, and the total annual milk production was 127 millions litters of fresh milk (FAOSTAT 2004). Although, the growth rate of dairy herd is rather high, milk consumption is still low and total domestic fresh milk can only provide about 10 % of the demand. In order to rely less on imports in the future, production systems have turned from being extensive to being more intensive, especially in the suburban areas. The higher production intensity in combination with shortage of high quality forages, especially during the dry season, make the dairy farmer dependent on supplementation of concentrates. The farmers use abundant amounts of concentrates for dairy cows, which results in competition for the use of cereal by-products with monogastric animals; it also increases the risk of lactic acidosis syndrome in lactating cows (Leng 1997).

It is important to develop dairy systems that work against the dependency on concentrates. This can be done by using local resources such as crop residues and agro-industrial by-products for feeding lactating dairy cows. However, problems rise when feeding dairy cows these low quality fibrous feeds in a hot and humid tropical environment. Feeding generates a lot of heat in the cow, both from metabolic processes and muscular activities. This heat is usually referred to as the heat increment. To avoid entering heat stress, the cow reduces the appetite with decreased feed intake and milk production as a result.

Feed DMI starts to decline and maintenance expenditures increase when environmental temperatures exceed 25°C (NRC 1981). Therefore it is of great importance to formulate diets that help the cow to regulate her body temperature and maintain milk production. This can be done by decreasing the fiber content of the diet. As a general rule, the more fibrous is the feed, the higher is the heat increment. Tropical diets often are short in protein. By adding a protein feed to the diet the efficiency can increase, both by increased microbial growth in the rumen and by supplying the cow with intestinally-available amino acids that are restricting production. However, feeding protein - especially rumen degradable protein - in excess of NRC (1981) recommendations has been shown to decreases DM intake and milk yield in heat-stressed cows (Huber et al 1994). The decrease in milk yield is greater than the reduction in energy intake because additional energy is required to convert the excess protein into urea for excretion.

Improving protein quality supports higher levels of milk yield in cows under heat stress (Huber et al 1994). Cows fed diets containing higher concentrations of lysine (from a combination of soybean, fish, and blood meals) produced 11% more milk under heat stress conditions (Chen et al. 1993). The results of including supplemental fats which have a low heat increment have been variable. Milk yield increased (Chan et al 1992; Huber et al 1993) or remained the same (Chan et al  1993) suggesting that the response to supplemental fat is less for heat-stressed cows than unstressed cows. Addition of fungal cultures has been reported to increase milk yield by approximately 4% and decrease rectal temperatures and respiratory rates (Huber 1994), but the results have not been consistent. Imbalanced diets may lead to excessive rumen ammonia resulting in a decreased energy efficiency when ammonia has to be excreted as urea, and thereby resulting in a higher heat increment. This is of course also a question of animal welfare, because heat stress has shown to cause drastic physiological and behavioral changes in the cow.

The hypothesis behind this study is that use of appropriate supplements could help the cow to regulate her body temperature and maintain a high feed intake and milk production with feeds that generally generate a lot of heat during digestion.

The objectives of this study were to: a) quantify the effects on feed intake, production and heat stress of dairy cows fed diets consisting of fibrous by-product feeds combined with a protein source of varying quality, b) study the impact of the heat load on the cow’s welfare through physiological and behavioural measurements, and c) compare the susceptibility to enter heat stress between cows of the tropical breeds and cows of the temperate breeds with higher production potential.   

Materials and methods

Location

The experiments were carried out at the state farm of Long Thanh district, Dong Nai province, VietNam. The mean air temperature was 28 °C and the relative humidity was 74 %.

Animals and housing

Forty crossbred cattle (Holstein x Sindhi) weighing on average 480 kg were housed in individual stalls in a barn with open sides. Fresh water was available ad libitum during the whole experiment.

Experimental design

The animals were allocated at random to 4 treatments in a 2*2 factorial experiment. The first factor was: MD, Mixed diet, consisting of Panicum grass, concentrate, brewery waste, alfalfa hay and sugar cane juice; and SD, Separate diet, including the same feedstuffs as MD but supplied separately. The second factor was improved environment: IE, consisting of spraying water on the animals and an air fan; and unimproved environment (NIE) with no intervention.. The treatment period lasted 120 days.

Diet and treatments

The diets were distributed twice daily at about 07:30 h and 15:00 h. In the MD treatment the Panicum grass, brewery waste, alfalfa hay, sugar cane juke and concentrate were mixed and fed together. In the SD treatment the feedstuffs were the same as in the MD treatment but were offered separately. The animals had access to the feeds the whole day.

Measurements

Temperature, humidity and temperature-humidity index (THI)

The temperature was recorded by thermometer. Humidity was recorded by hygrometer. The temperature-humidity index (THI) was calculated from the formula:

THI = T + (0.36 * H/100 * T) + 41.2⁰C.

Rectal temperature, heart rate and respiration rate

Rectal temperature, heart rate and respiration rate were measured frequently in order to quantify the effects of heat load.

Chemical composition of feed ingredients

Feed samples were taken for analysis of crude protein, ether extract, neutral detergent fiber, and acid detergent fiber, according to procedures of AOAC (1990).

Dry matter intake and milk production

Data on daily feed intake were calculated by weighing the Panicum grass, brewery waste, alfalfa hay, sugar cane juke and concentrate offered and refused each morning during the last 3 days of each week. Feed samples for dry matter and ash contents were also determined at this time.  The milk production was measured daily.

Statistical analysis

Data were analyzed by ANOVA using the General Linear Model option and Pair-wise comparisons in Minitab Statistical Software version 13.31 (Minitab 2000).

Results

Temperature, humidity and temperature-humidity index (THI)

The data for temperature, humidity and THI indicated conditions were similar in the improved and unimproved environment (Table 1; Figure 1).

Rectal temperature, heart rate and respiration rate

Rectal temperature, heart rate and respiration rate were not affected by diet preparation or by the environmental condition (Table 2).

Chemical composition of diet ingredients

During the experimental period, there were only small changes in the chemical composition of Panicum grass, brewery waste, alfalfa hay, sugar cane juice and concentrate (Table 3)..

Table 3. Chemical composition of feed ingredients used in the experiment (mean and SE on DM basis)

Feed intake and milk yield

Dry matter intake and daily milk yield were higher in the improved environment but there were no differences due to diet preparation (Table 4).

Acknowledgments

The authors are grateful to the Swedish International Development Authority (Sida) for funding this study.

References

AOAC, 1990. Official methods of analysis of the Association of Official Analytical chemist (15^th Edn.), Washington, DC. 1: 69-90.

Chan, S. C., J. T. Huber, Z. Wu, K. H. Chen, and J. Simas. 1992. Effect of fat supplmentation and protein source on performance of dairy cows in hot environmental temperatures. J. Dairy Sci. 75 (Suppl. 1):175. (Abstr.)

Chen, K. H., J. T. Huber, C. B. Theurer, D. V. Sullivan. 1993. Effect of supplemental protein quality and evaporative cooling on lactational performance of Holstein cows in hot weather. J. Dairy Sci. 76:819 - 825.

Huber, J. T., Z. Wu, S. C. Chan, and J. Simas. 1993. Feeding of fat during heat stress conditions, and combinations of fat sources. Page 90 in Proc. Southwest Nutr. Manage. Conf., Phoenix, AZ, Dept. Anim. Sci., Univ. of Arizona, Tucson.

Huber, J. T., G. Higginbotham, R. A. Gomez-Alarcon, R. B. Taylor, K. H. Chen, S. C. Chan, and Z. Wu. 1994. Heat stress interactions with protein, supplemental fat, and fungal cultures. J. Dairy Sci. 77:2080 - 2090.

FAOSTAT data, 2004. FAO statistical Database. Food and Agriculture Organization of the United Nations. Rome. http://faostat.fao.org/default.jsp.

Leng, R. A. 1997. Tree foliage in ruminant nutrition. FAO animal production and health paper, volume 139. FAO, Rome.

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