Source: Ministry of Agriculture, Food and Rural Affairs
The analogy of farm animals as manufacturing machines has been employed for a long time to represent the different aspects of the whole animals’ energetic metabolism. Similar to machines, animals consume fuel (feed), produce a product (carcass) and, in accordance with their production level, energy will be lost, mainly as heat and gas emissions. Therefore, the lower the energetic losses relative to the energetic input (feed intake), the greater the animal’s energetic efficiency. Differences in energetic efficiency may have important economic and environmental implications.
At the Elora Beef Research Center, University of Guelph, leading edge equipment for assessing metabolic differences in cattle with known feed efficiency is currently in operation. This equipment features individual cattle stalls equipped with head chambers designed to continuously sample gasses (Figure 1). While an animal is restrained in the stall, sensors monitor the consumption of oxygen and the production of both carbon dioxide and methane, with measurements being taking each second. These measurements allow the calculation of metabolic heat production of the animal (indirect calorimetry).
Figure 1. Feedlot steers in individual stalls for 24h continuous gasses assessment at Elora Beef Research Center, University of Guelph.
An animal’s metabolic rate has a profound effect on the efficiency of feed utilization. The indirect calorimeter is the gold standard for equipment for evaluating metabolic rate in cattle. While not directly usable on commercial farms, its application on research centers, for testing alternative assessments which could be applied in commercial herds for feed efficiency, is crucial. The ultimate goal of these investigations is to fully evaluate the application of potential indicators for feed efficiency such as infrared thermography, blood plasma parameters (hormones and metabolites) and behaviour traits.
The experimental procedure for evaluating potential indicators for feed efficiency includes a 112 day feeding test to assess individual feed intake on a daily basis, plus body weights and ultrasound data collected every 28 days. At the end of the test, these data are used for ranking cattle according to feed efficiency. Following this, cattle with from each extreme of the efficiency ranking are selected for gasses measurement. (For example, out of 120 steers the 12 best and the 12 worst for feed efficiency would be selected) Each of these animals then have their gasses sampled for 24hrs in the calorimeter. At the same time, infrared pictures of 8 different body locations (e.g. feet, snout, eye, flanks) and blood samples are collected on an hourly basis to study how hormones and metabolite concentrations change over the 24h. In addition, pedometers are placed in these cattle during the 24h sampling period to quantify number of steps and time spent standing or lying down.
Feedlot steers (mainly Angus and Simmental crosses) were fed a ration of 80% high moisture corn, 12% haylage, 5% soybean meal and 3% mineral premix. Preliminary results revealed that high feed efficiency steers were consuming around 3 kg less feed a day (as fed basis) during the 112 days of feedlot than low efficiency cattle. This represents about 336 kg less feed per head for cattle which achieved the same body weight and carcass composition at the end of feedlot period. This equates to saving a tonne of feed for every 3 high efficiency cattle fed. The calorimetry data is also encouraging. These data indicated that high efficiency steers have significantly more efficient “metabolic engines”. High efficiency steers produced around 20% less heat and 40% less methane than low efficient cattle. The lower methane production of the high efficiency cattle not only represents a great environmental benefit for this type of cattle, but also helps to explain their efficiency advantage since methane (a combustible gas) is an important avenue for energy loss in cattle.
We are currently analyzing these data in conjunction with infrared data and blood parameters. We expect to have more clues regarding the identification of more efficient cattle in the near future.
We would like to thank the staff at Elora Beef Research Center for their assistance with these laborious trials, and also our big crew of volunteers (28 hard working students), as well as the support from BCRC, OMAFRA and OCA.
Author: Yuri R. Montanholi and Steve P. Miller – Department of Animal Science, University of Guelph
