Measurement of the energy metabolism of dairy cows using the traditional face mask system. (Short Communication)

Abstract

MEASUREMENT OF THE ENERGY METABOLISM OF DAIRY COWS USING THE TRADITIONAL FACE MASK SYSTEM Zhang Xiaoming* and Jiang Yongqing* Calorimetric measurements are normally made in respiration cha&ers but the face mask has some advantages for short-term measurements of energy exchange of large animals. It is inexpensive and measurements can be made on animalsinpens. Three energy exchange experiments on dairy cows and heifers were conducted with a Chinese-made traditional open-circuit mask system in a thermneutral zone on a dairy farm near Beijing. Experiment 1: The fasting metabolism of 4 adult, non pregnant, dry Chinese Holstein cows was measured on days 4-6 of fasting. The expired air from the cows was collected for 5-8 mins at 0200 h, 0800 h, 1400 h and 2000 h each day. The colrposition of the collected air was analysed with Haldane apparatus, The heat production was calculated using Brouwer's (1965) forrmla. The average 24h heat product.0 +zalculated from the surcrmation of each collection period was 72.1 Kcal dY. l Experiment2: The fasting metabolism of four groups of 3 Chinese Holstein growing heifers (9-18 months of age) was measured. The age intervals between the groups was 3 months, Theexperimentalmethodwasthe same asthatused in aged 12-18 mnths at experiment 1. The fasting heat production of fasted body weight of 190-320 kg was 277.5 Kcal per day. A large effect of age on fasting metabolism was evident, and the statistically significant regression of fasting heat production (FM) on age (t, months) was: Experiment 3: The heat production of 3 early pregnant Chinese Holstein heifers aged 22 months was measured during standing and walking at two different speeds. The experiments were conducted in 0700-08OOh each day. After measurements during standing, the mask system was fixed to the bxk of the cows. The expired air was collect&l during walking. The collection period was about 2.5 minutes. The energy cost of walking was 0.33 Cal/kg W per mtravelled and 0.46 Cal/kg W per m at speeds of 0.95 m/set and 1.54 m/set . respectively. There was a significant effect of speed on energy expenditure. BEtOWER, E. (1965). In: 'Energy Metabolism of Farm Animals' ted. K-L. Blaseter) pp. 441-443 (Academic Press: London). *Departmt of Animal Science, Beijing Agricultural University, Beijing 100094, China, 16A