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
