Properly measuring and determination of body weight is essential for achieving many important goals related to the medical or economic status of animals. However, in village settings, this can be challenging due to the lack of weighing scales.
Knowing the live body weight of small and large ruminants is crucial for various reasons, such as breeding, proper feeding, and health management (Slippers et al., 2000).
In addition to taking live weight, researchers often use other measurements like body length, pelvis width, height at the withers, and chest girth to evaluate live animals (Atta et al., 2004).
Under standard conditions, properly calibrated livestock scales are the most accurate and consistent way to determine body weight. However, on farms where scales and records are unavailable, it can be difficult to know the weight of sheep and goats (Abegaz and Awgichew, 2009).
Furthermore, these standard scales are often too expensive for most small farmers (Mahieu, 2011), forcing them to estimate body weights using easily measurable body characteristics (Alade et al., 2008).
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Procedures for Estimating the Weight of Small Ruminants
1. Weight Band
The weight band is wrapped directly behind the shoulder blade, down the fore-ribs, under the body behind the elbow, and back around to the point behind the shoulder blade. The ends of the band overlap on top of the goat’s spine, and the weight is read off the band in kilograms.
2.Visual Appraisal
Estimating the weight of animals by sight often leads to errors, such as using the same estimate for more than one breed of a particular species (Otoikhian, 2008).
Body structure can be misleading when estimating weight (Slippers et al., 2000). For example, Red Sokoto goats often appear lighter than they are because of their light bones. Additionally, white animals often appear bigger than they are (Otoikhian, 2008).
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3. Body Linear Measurements
Various linear dimensions can be used to estimate an animal’s size and weight. The most common measurements include height at withers, heart girth, chest depth, body length, fore cannon bone length, rump height, distance between the eyes, ear length, ear width, paunch girth, and tail length. Heart girth and cannon bone length are least affected by the animal’s posture.
Abegaz and Awgichew (2009) describe these linear measurements as follows:
i. Height at Withers (HAW): This measures the distance from the surface on which the animal stands to the withers. The measurement is best taken with a special measuring stick that has two arms: one vertical and one sliding arm at a right angle. The sheep or goat should stand squarely on all four legs, equally spaced, and carrying equal portions of its weight.
The vertical arm is placed on the ground, ensuring it is at a right angle to the platform. The sliding arm is then lowered until it touches the shoulder at the desired point. The distance is then measured with a measuring tape, or the height can be read directly from a scale inscribed on the vertical arm. This method can be used alone or with other linear measurements for more accurate results.
ii. Heart Girth (HG) or Chest Circumference: Heart girth is measured around the chest just behind the front legs and withers. The measurement should be taken to the nearest 0.5 cm. Although HG is highly repeatable, it may vary slightly due to the animal’s posture or breathing.
iii. Body Length (BDL): Body length refers to the distance from the base of the ear to the base of the tail, or from the base of the tail to the base of the neck, the front of the chest, or the tip of the nose. Care must be taken to ensure the backbone is straight in both vertical and horizontal planes.
iv. Hip Width (Pin Bone Width) (HW): Hip width is the distance between the outer edges of the major hip bones on the right and left sides. These bones are easy to locate, and the distance can be measured with a pair of large, half-round or oval-shaped calipers.
v. Rump Height (RH): Rump height is the distance from the platform surface to the rump, measured with a stick as described for height at withers.
vi. Fore Cannon Bone Length (CB): This is the length of the lower part of the leg, from the hock to the fetlock in hoofed mammals. It is well-established that the linear development of different bones in the body is strongly related.
vii. Chest Depth (CD): Chest depth measures the distance from the backbone at the shoulder (standardized on one of the vertical processes of the thoracic vertebrae) to the brisket between the front legs.
Precautions While Taking Body Linear Measurements
Since an animal’s body movement and posture can introduce errors in measurements and weight estimates, Abegaz and Awgichew (2009) suggest the following precautions:
1. Choose measurements that are less affected by the animal’s posture when possible.
2. Standardize the position of all animals to be compared.
3. Be patient and wait for the animal to stand correctly.
In summary, accurately measuring the body weight of livestock is essential for managing their health, breeding, and feeding. However, in rural areas, the lack of weighing scales makes this challenging, prompting farmers to rely on alternative methods like visual appraisals and body measurements.
These methods, though practical, can be inaccurate due to variations in animal posture, body structure, and breed differences. Researchers recommend using standardized linear measurements, such as height at withers, heart girth, and body length, as reliable indicators of weight. Proper techniques and patience are crucial to minimizing errors and improving the accuracy of weight estimates.
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