Technical Note: The relationship between heart rate and energy expenditure in growing crossbred Boer and Spanish wethers1

Abstract

Eight Boer (75%) x Spanish (BS) and 8 Spanish (S) wethers (155 +/- 8 d of age and 19.2 +/- 2.3 kg of BW initially) were used in a replicated crossover design with a 2 x 2 factorial arrangement of treatments to determine effects of genotype, diet quality, and time of day on energy expenditure (EE), heart rate (HR), and EE:HR with ad libitum, near maintenance, and fasting levels of feed intake. Diets were 65% concentrate or coarsely ground alfalfa hay. Energy expenditure was ranked (P < 0.05) ad libitum > maintenance > fasting (500, 390, and 270 kJ/kg of metabolic BW). Heart rate did not differ between genotypes when fasting and with maintenance intake, but was greater (P < 0.05) for S than for BS when intake was ad libitum (BS: 55, 71, and 92; S: 52, 72, and 100 beats/min for fasting, maintenance, and ad libitum, respectively, SEM = 2.0). There was an interaction in EE:HR (P < 0.05) between level of feed intake and genotype (BS: 5.31, 5.59, and 5.00; S: 5.07, 5.57, and 5.22 kJ/kg of metabolic BW:beat/min for ad libitum, maintenance, and fasting, respectively, SEM = 0.13), without an effect of diet. The effect of time on EE, HR, and EE:HR differed among levels of intake (P < 0.05). General patterns of change in EE and HR as time of day advanced did not differ, but increases near meals followed by decreases were of slightly greater magnitude for maintenance than for ad libitum intake. The ratio of EE:HR was greater for the maintenance level of feed intake than for ad libitum intake at most times. These results indicate similar potential for use of HR to predict EE of different genotypes of growing meat goats and that establishing EE:HR with different diets or levels of intake may not be crucial. Magnitudes of difference among hours suggest that when EE:HR is used to predict EE of confined goats from full-day measurement of HR, EE:HR should be determined over an extended period of time, such as 24 h.

Effects of the number of animals per automated feeder and length and time of access on feed intake, growth performance, and behavior of yearling Boer goat wethers

“…The procedure of monitoring HR was described by Puchala et al (2007Puchala et al ( , 2009. In brief, wethers were fitted with 5 × 5 cm electrodes prepared from stretch conductive fabric (Less EMF, Albany, NY, USA), glued to Vermed PerformancePlus ECG electrodes (Bellow Falls, VT, USA) and attached to the chest just behind and slightly below the left elbow and behind the shoulder blade on the right side.…”

“…During the adaptation period, the ratio of heat energy (HE) to heart rate (HR) (HE:HR) was determined as described by Puchala et al (2007Puchala et al ( , 2009. The same diet used in the experiment was fed.…”

Simple methods to estimate the maintenance feed requirement of small ruminants with different levels of feed restriction

“…The most probable reason for the greater maintenance feed requirement for the HR vs. BW method with the 55% restriction level is the use of the HE:HR ratio determined in the preliminary period with a level of intake slightly above the assumed maintenance requirement. In this regard, Puchala et al (2009) reported ratios for Boer wethers of 5.59 and 5.00 kJ/kg BW 0.75 per heart beat/ min when consuming feed at a level of intake near maintenance and while fasting, respectively, and values of 5.57 and 5.22 were noted for SPA wethers with similar intake levels.…”

“…Wethers were moved to an adjacent room in the facility with an indirect open-circuit calorimetry system in sets of four. Heat energy (HE) and heart rate (HR) were determined as in other studies (Puchala et al 2007(Puchala et al , 2009 for approximately 24 h to derive the ratio of HE to HR for multiplication by HR estimated in subsequent phases to predict HE. Oxygen consumption and production of CO 2 and CH 4 were determined by an indirect open-circuit respiration calorimetry system (Sable Systems, Henderson, NV, USA) with four head boxes situated in metabolism cages in a calorimetry room.…”

Effects of restricted periods of feed access on feed intake, digestion, behaviour, heat energy, and performance of Alpine goats

“…HE was determined by use of heart rate (HR) for prediction, as described by Puchala et al (2007Puchala et al ( , 2009. During the middle week of each period on days 2 and 4, HR was recorded for 24 h, with measurements first on five animals per pen and then on the second five animals.…”