Methods to Improve Feed Efficiency in Softshell Turtle Farming
In the process of factory-based softshell turtle farming, estimating and controlling feed quantities is a key part of daily work. The disadvantages of overfeeding are obvious: first, it wastes feed, directly increasing production costs; second, it pollutes water bodies, worsening the farming environment, leading to chronic poisoning in turtles, reduced immunity, increased disease incidence, lower survival rates and growth performance, as well as a decrease in feed conversion rate; third, it increases the cost of water changes, pollutes the environment, increases stress, affects feeding, thereby extending the farming cycle. On the other hand, insufficient feeding is also unacceptable: first, it suppresses the growth of the turtle population, forcing an extension of the production cycle; second, due to fierce food competition, the proportion of stiff turtles increases, and the proportion of inferior turtles rises due to mutual biting during food fights; third, due to insufficient feed, the proportion of feed used for growth decreases, thus reducing feed efficiency. Therefore, appropriate feeding in softshell turtle farming production is very crucial.
The so-called daily average feed quantity refers to the amount of feed each turtle needs daily for normal growth, measured in grams per turtle per day. For example, 10,000 turtles with an average size of 100 grams require a normal daily feeding of 20 kilograms, which means a daily average feed quantity of 2 grams per turtle per day. In my opinion, the daily average feed quantity for young turtles should be precise to 0.01 grams, while for juvenile and adult turtles, it should be precise to 0.1 grams, in order to accurately guide farming production. So, how do we correctly calculate the daily average feed quantity for softshell turtles in production? I believe the reverse calculation method should be applied. Simply put, softshell turtle farming involves how much feed is fed and how many turtles are produced; conversely, producing a certain number of turtles requires feeding a corresponding amount of feed. Therefore, if farmers can master two basic parameters, they can easily calculate the normal daily average feed quantity: one is the normal monthly growth speed of turtles, and the other is the normal feed coefficient of the feed being used. For instance, if the current average size of the farmed turtles is about 50 grams, then under normal production conditions, these turtles will gain an average net weight of approximately 40 grams per month. If the selected feed has a bait coefficient of 1.0, then feeding 40 grams of feed per turtle per month would meet the growth requirements, meaning a daily average feed quantity of 1.3 grams per turtle per day. Dividing a month into three periods, as turtles grow continuously, the feed quantity should also increase accordingly. Thus, the average daily feed quantity for the early period is 1.2 grams per turtle per day, the middle period is 1.3 grams per turtle per day, and the late period is 1.4 grams per turtle per day; these three numbers can serve as the basic parameters for the monthly daily feed quantity. The specific individual daily feed quantity should be determined by referring to recent turtle feeding status, health status, as well as water temperature, water quality, water changes, stress, climate, etc. Another example: the current average size of turtles is 100 grams per turtle with a normal monthly net weight gain of 60 grams per turtle, and the selected feed has a bait coefficient of 1.5, then 90 grams of feed need to be fed this month to meet the growth needs, meaning a daily average feed quantity of 3.0 grams per turtle per day.
How to determine the optimal feed quantity, in production, farmers often use the daily feeding rate provided on the feed packaging by feed manufacturers as a reference to determine the total daily feed quantity, but due to the lack of practical farming experience among feed company technicians, the daily feeding rate reference indicators marked on the packaging are either arbitrarily imagined or copied from each other, thus losing their reference value. Moreover, the concept of daily feeding rate itself is not rigorous enough, with too many variable factors and a large range, providing little guidance for actual production. If improperly referenced, it may cause significant losses to farming production. Therefore, I believe that in softshell turtle production, it is necessary to introduce the concept of daily average feed quantity to comprehensively replace the daily feeding rate.
1. Control of feeding quantity. Regarding this point, I believe it mainly involves considering both the daily average feeding quantity and the feeding time. The normal feeding quantity should be 0.1-1.2 grams per turtle for young turtles (3-50 grams per turtle), 1.0-2.6 grams per turtle for juvenile turtles (50-200 grams per turtle), and 2.5-6.0 grams per turtle for adult turtles (over 200 grams). As for feeding time, if feeding twice a day, it should be finished within 40 minutes; if feeding three times a day, it should be finished within 30 minutes; if using a small frequent meals feeding method, it should be finished within 20 minutes. Units with conditions should preferably adopt the small frequent meals method to feed, which not only reduces feed loss as much as possible but also allows more opportunities for turtles that eat poorly to consume feed, and improves the utilization rate of synthetic amino acids and carbohydrates added to the feed, thereby further lowering the bait coefficient.
2. Feed adhesion elasticity. The good or bad adhesion elasticity of feed directly affects the degree of feed loss, especially when using underwater feeding methods, the stickiness of feed becomes even more important. Strongly adhesive feed is less likely to be lost, resulting in less waste and naturally higher feed efficiency; otherwise, the feed efficiency will be low.
3. Selection of secondary processing machinery for feed. There are various types of feed processing machinery available on the market. I believe that choosing Hangzhou-produced soft pellet machines or modified meat grinders is preferable. Using this type of machinery to process feed, adding 400-500 grams of water per kilogram of feed results in uniformly sized soft pellets with smooth surfaces and good water stability after processing.
4. Selection and setup of bait trays. Common bait trays used by farming units include materials such as asbestos tiles, wooden boards, and cement boards, with various placement methods including flat, single-sided slope, and double-sided slope. I believe that setting up bait trays using the method of placing asbestos tiles underwater horizontally is the most ideal. This method reduces bait waste, ensures uniform feeding for turtles, makes residual feed easy to observe, and uses widely available materials, making it simple and feasible. It's important to note that the depth at which the asbestos tiles are placed underwater must be well controlled; if too deep, the bait is likely to escape, and if too shallow, it's difficult for turtles to eat. The appropriate depth is when the top of the asbestos tile waves is 3.0-4.0 centimeters away from the water surface.
5. Addition of oils. Adding an appropriate amount of oil to the feed not only increases the feed energy, ensuring the need for essential fatty acids, but also makes the processed feed have a smoother surface and better stability, greatly benefiting the reduction of feed waste and improving feed efficiency. Generally, it is believed that adding 1% fish oil and another 2% corn oil to softshell turtle feed is the best combination.
6. Selection of feeding methods. Currently, there are various feeding methods across different regions, each with its own characteristics. In general, they can be divided into four main ways: underwater feeding with soft pellets, above-water feeding with soft pellets, above-water feeding or underwater feeding with lump-shaped (or pancake-shaped) feed. I believe that the method of underwater feeding with soft pellets is the most scientific. This method ensures uniform feeding for turtles, makes it easier to control feeding time, guarantees feed freshness, reduces feed waste, minimizes individual differences in grown turtles, and lowers the bait coefficient.
7. Expectation of bait coefficients and growth rates of softshell turtles. Over the years, different feed production enterprises and farming units have had varied opinions on bait coefficients and expected growth rates of softshell turtles, with significant differences. Indeed, the factors affecting these two aspects are multifaceted, but ultimately, there are still some standards and patterns to follow. Under normal production conditions, high-quality softshell turtle feed has a bait coefficient of 0.8-1.0 for young turtles; for juvenile turtles, the bait coefficient is 0.9-1.2 under greenhouse conditions and 1.0-1.5 in outdoor ponds; for adult turtles in outdoor ponds, the bait coefficient is 1.2-1.6. From the perspective of normal growth rates, the average size of young turtles can reach 15-20 grams one month after release, 40-50 grams in the second month, and 80-100 grams in the third month. Afterwards, the average monthly weight gain per turtle should be 60 grams or more. After 185-195 days of breeding, 20-35% of turtles should reach the marketable size of over 8 liang (approximately 400 grams). Based on these two points, combined with the previously discussed control of feeding quantities, it is not difficult to calculate a relatively accurate daily feeding quantity, which is of great significance for guiding correct production. Some farming units always think that the more feed consumed, the faster the turtles will grow, and they tend to overestimate the bait coefficient. Combined with unscientific usage methods, what they actually perceive as turtles eating all the feed is just feed wastage. Consequently, the more feed is thrown, the faster the water quality deteriorates, requiring more frequent water changes, yet the turtles become harder to raise well, and the feed efficiency gets worse. This is the result of failing to correctly recognize the normal bait coefficient and not seeking the right way to use the feed.
8. Daily management. Daily management work mainly includes regulation of water temperature and air temperature, operation of oxygen generators, daily water quality management, handling of dead turtles, observation of feeding situations, and implementation of disease prevention measures, which are the key tasks for every farming unit. The quality of daily management work directly affects the health of the turtles and the effectiveness of feed usage.
The three indicators of daily average feed quantity, feed coefficient, and normal growth speed of softshell turtles influence each other and maintain a dynamic balance. Any change in any one of these indicators will directly affect the others.