By Melanie Barkley
Sheep producers constantly strive to improve lamb quality and value within their flock in order to produce an acceptable commodity for their buyers. These buyers could be either lamb packers or lamb consumers from the general public. Acceptability of the finished product can have major impacts on profitability for the sheep operation. Here are a few tips to consider that may improve the quality and value of lambs produced by a flock.
First, let's start with an understanding of what quality is. Eating quality is a perception by the consumer based on some key characteristics such as tenderness, juiciness, flavor, and overall acceptability of the product. Basically, we want all lamb consumers to have a good eating experience, which may add more value. We can help to ensure this good eating experience for consumers by considering the main factors that affect lamb quality and value.
There are several points that producers can control to manage lamb quality. Aspects such as genetics, feed, growth rates, body condition and husbandry practices can greatly impact lamb quality.
Genetics
Genetic impacts start with selecting breeding stock with appropriate muscling. Consumers certainly prefer larger loin eyes when selecting lamb chops. However, producers may want to avoid genetics that carry the Callipyge gene, a genetic mutation responsible for increasing muscle size and appearance in sheep. Although this appearance may look attractive to some individuals, the Callipyge mutation can also greatly decrease tenderness of meat produced from Callipyge carcasses. In other words, Callipyge genetics produce lamb chops with larger loin eyes, but those lamb chops tend to be very unacceptable to consumers from a tenderness standpoint.
Feeds
Feeds can impact lamb flavor profiles. Lambs finished on a high forage diet produce a more intense flavor when compared to lambs finished on a grain diet. This flavor may sometimes be referred to as "gamey" to some individuals not accustomed to lambs finished on forages. In contrast, meat from lambs produced with extended periods of high grain diets can result in off flavors and soft fats that leads to higher rancidity and decreased shelf life. The decision to finish lambs on grain or grass should be made based on customer preferences. Know what your customer wants you to produce.
Growth Rate
Rations can certainly impact lamb growth rate, but tenderness remains similar between fast and slow growth rates. Regardless of the growth rate (fast or slow), it is very important that lambs maintain a consistent growth rate from weaning to harvest. This is especially critical during the last two weeks of finishing just prior to slaughter.
Rations will also impact the amount of time is takes for lambs to develop intramuscular fat, also known as marbling, found in the meat. However, meat quality differences can be minimal if lambs are fed to a particular end point (harvest) weight. At this end point collagen degradation rates will be greater in lambs with high growth rates. What this means in terms of lamb quality is that the collagen tissues break down more quickly in lambs fed to gain weight faster and thus results in a more tender meat.
Body Condition or Finish
Lambs should be marketed when they reach a desired body condition or finish. Lambs fed to a yield grade 2 or 3 are often the most ideal for packers and consumers. A lamb with a yield grade 2 will have 0.16 to 0.25 inches of backfat at the 12th rib, while a lamb with a yield grade 3 will have 0.26 to 0.35 inches of backfat. This is an important consideration when producing lambs, because animals with an adequate amount of finish should yield a high-quality carcass that has enough fat to produce meat with desirable sensory qualities. These qualities should provide the consumer with a good eating experience. Adequate fat cover also provides enough insulation over the carcass to prevent cold shortening, a quality defect caused by chilling small or lean carcasses too rapidly. Whenever a carcass is hanging in a cooler for chilling, the muscle tissues can shorten if the chill rate is too fast. "Cold shortening" can lead to extremely tough meat because the "shortening" effect causes the muscle structure to remain in a constant state of being contracted. However, the amount and extent of shortening can be lessened whenever the carcass has adequate finish because it chills more slowly. Very small and/or lean lamb carcasses may need a two-step chilling process to avoid excessive cold shortening.
Appropriate amounts of finish impact the value of lambs to packers. Lamb carcasses exhibiting excessive fat cover will have a lower value because it costs the packer time and money to trim the excess fat. Lamb meat with appropriate amounts of fat will also be more acceptable to most consumers. In contrast, under finished lambs can develop quality defects due to excess drying of the meat while hanging in the cooler.
Husbandry Practices
Husbandry practices can also affect meat quality due to various stressors at the farm, stress caused by transport and the pre-slaughter environment. Always seek to minimize stress when handling or transporting lambs by reducing noise and by handling animals gently. Do not mix lambs from different groups into one pen or lairage, check loading ramps and trailers for any areas that could cause bruising and avoid overloading the trailer. Also, be sure to move animals slowly and avoid vigorous exercise. Chasing lambs around the pen can be quite stressful to sheep at any age.
Whenever an animal is stressed or has vigorous exercise prior to slaughter, glycogen becomes depleted in the muscle tissues. Animals store glycogen, a form of sugar or energy, in muscle tissues. This impacts the pH level of the muscle tissue after slaughter which can impact meat quality. Once an animal is harvested, the stored glycogen is converted to lactic acid which decreases the meat pH from about 7.2 to 5.5.
The meat derived from stressed animals with depleted glycogen levels maintains a high pH (> 6.0), which has a negative impact on meat quality. The meat color will remain dark upon cutting into chops or roasts, will produce a more intense flavor and have a decreased shelf life.
Pre-slaughter husbandry practices can help to manage glycogen reserves in muscle tissue. Lambs that have not been appropriately weaned prior to slaughter should be processed immediately on arrival at the processing facility to minimize stress. Weaned lambs that have been hauled a long distance should receive an adequate rest period prior to slaughter. All lambs should have access to water to prevent dehydration which could lead to meat quality issues such as dark colored meat. Dehydration also leads to decreased carcass weights and dressing percentages.
Lambs should be held off feed for a 12-hour period prior to slaughter. This allows the GI tract to empty, which decreases the likelihood of fecal contamination on the carcass. For lambs that may be scouring prior to shipment, feeding additional hay may stop the scouring. However, avoid feeding hay in high enough levels or for extended periods of time that may result in lambs losing weight within the two weeks prior to slaughter.
Overall, increasing the quality and value of lambs begins with paying close attention to nutrition, selecting animals with adequate muscling, feeding them to an appropriate body condition, keeping lambs clean and making sure that lambs are gaining weight throughout the finishing phase and especially during the last two weeks before harvest. Minimizing stress to the lambs will also positively impact meat quality. Paying close attention to these few simple production aspects can result in higher quality meat and more satisfied consumers.
Source : psu.edu