本文是动物医学专业的留学生assignment范例，题目是“Equine Nutrition Assignment -Effect of Nutrition on Young Stock（马的营养分配-营养对幼畜的影响）”，马驹生命的开始强烈地决定了产出的结果。为了成功地生产小马驹或幼马，了解小马驹的需求是很重要的。遗传、环境和营养是决定它们个体生长模式的三个最重要的因素。通过有知识的育种，我们可以在一定程度上控制马驹的基因组成。一匹母马所缺乏的，我们也许可以在他身上找到，反之亦然。我们也可以用基因来赞美和强调彼此，希望能制造出我们想要的马。这种被称为遗传潜力的动物，是从父系和母系遗传而来的，它主要与动物一生生长模式的整体形状和成熟的体型有关。
The start of a foal’s life strongly determines the produced outcome. In order to achieve successful foal or young stock production, it is important that we understand the needs of the foal.Genetics, environment and nutrition are 3 of the most important factors in determining their individual growth patterns.Through knowledgeable breeding we can to a point, control the genetic make up of the foal. What a mare lacks we can find perhaps in the sire and vice versa. We can also use genetics to compliment and accentuate each other, hoping to make the desired horse. This genetic potential as it is called, is inherited from the sire and the dam and it mainly relates to the overall shape of the lifetime growth pattern and the mature size of the animal.
Through a safe and healthy environment, we can control the mare’s 340-day gestation period ensuring that the mare can deliver a healthy young foal. She won’t need specialized prenatal care for the first 8 months, but the attention she will need for the last 3 months of gestation are critical to both her health and that of her foal. It is very important at this point to give her the best possible health, welfare and nutrition, including vaccinations and parasite control that we can.
1.Growth Rates in Young Stock幼畜的增长率
The optimal growth rate we aspire to achieve should result in a desirable body size at a target age. We also need to be able to accomplish this without compromising the foal and without creating developmental issues.This is usually driven by the commercial endpoint and indeed, does not affect certain markets as much. However, in order to accomplish this, we need to understand what the intended horse is and for a particular purpose. Foals that are produced to be sold as weanlings, need to look big and strong to achieve good prices. Foals produced to be sold as yearlings however aren’t put under the same pressures.
Our main aims should be to achieve a steady weight growth rate, avoid sudden growth spurts and prevent excessive weight gain. Their growth should maintain an even and upward curve up until maturity usually at five years of age. This will help to avoid sudden growth spurts that can then put extra pressure on their joints, leading to poor conformation or soundness. Forced growth and an oversupply of carbohydrates will jeopardise the foal’s health and can be harmful to their physical development. Equally a sudden decrease in energy or protein intake can also contribute to DOD’s. This can often happen at the early weaning stage when the foal is suddenly deprived of the mare’s milk.
Weigh tapes and scales can be used to observe the progress of the foal and a developmental chart should be kept, noting the intended and average developmental gain for a foal of its age and type. Body weight, wither height, body length, and cannon circumference are some of the more commonly used measures of growth for horses. Each of these measures have a different pattern of growth, based on the types of tissues within that part of the body and the nutrients being supplied.
2.Feed Stuffs for Foals & Young Stock马驹及幼畜饲料
As are the last 3 months of the foal’s gestation the most impactful on growth in the womb so too are the first 2 years of their life. A healthy foal can grow up to 90% or more of its full adult size in these starting years, putting on as many as 3lbs per day.Correct feeding and balanced nutrition therefore are essential for their growth. Mare’s milk is the most important nutritional resource for foals during the ﬁrst months. For the first 36 hours it will provide the anti-body rich colostrum that helps protect it from disease and after that the huge volume of calories, fats and protein needed for their rapid growth.
Proper nutrition of the mare during gestation, will ensure that you have given her vital minerals such as iron, zinc, copper, manganese, selenium and vitamins A and E to pass onto the foal through lactation without depleting her of her own sources. Without these being available to the foal, it may succumb to bone developmental disorders.
A healthy well-conditioned mare will produce optimum protein, fat and sugar levels in milk thus encouraging correct growth rates of the foal. Higher amounts of fat will be produced by overweight mares, compromising the level of proteins. And on the other hand, and underweight mare will compromise both the fat and protein levels of milk which will affects the growth rate of foals.
At approximately 6 to 8 months the foals are generally weaned from their mothers, at this stage they weigh about 250kg and will be eating between 2-3% of its body weight in feed i.e. 2.5 kg a day.As weaning can be a time of increased stress, the foal can lose considerable weight. Environmental stresses, sudden weight losses and rapid weight gains can all contribute to DOD’s. Therefore, it is important to observe its body condition and eating habits before you address weaning and be confident that they are eating well before you proceed.
The quantity of protein enriched grain may need to be increased at this stage to make up for the loss of mare’s milk.
From weaning to 2 years old a horse will continue to grow at an incredible rate. They will continue to build muscle and bone rapidly therefore a high protein diet is necessary. At this stage they will need a diet containing 14-16% protein as well as high energy rations to be able to meet the demand for growth and activity.
A rule of thumb is to provide 60-70 % of the ration as concentrates and 30-40 % of the ration as roughage – measured by weight. The diet must also provide sufficient fibre to keep the digestive tract moving effectively to avoid any build up that could lead to gut pain and possibly colicing.
Feed merchants such as Red Mills and Gain produce complete feeds which contain a balanced ration suitable for foals and yearlings. They are purposely formulated to meet the requirements of growing young stock.
4.Factors that Affect Bone development影响骨骼发育的因素
Thoroughbreds and other light breeds will achieve 84% of their mature height at the age of 6 months old. Therefore, a weaning intending to achieve 16 hands, will approximately stand at 13,2” by this stage. At 12 months it will approximately be 15 hands achieving 94% of its adult height and by 22 months it will have almost reached 97% of its full height standing at 15,2”. This rapid growth succession demands huge growth efforts on behalf of the skeletal make-up of the horse.
Bone is a dynamic tissue always adapting to change in its nutritional and physical environment. Within the bone, there a many different compositions. The area mainly responsible for growth is the physes or the growth plates. They allow for the longitudinal extension of the bone enabling the horse to grow vertically and achieve its optimum height and form his structural conformation. This process is called ossification. In the growing foal, the diaphysis and epiphyses are centers of ossification. It is here where soft cartilage cells are transformed into hard bone cells thus growing the bone.
The strength of bone is derived from a mineralized cartilage framework. It responds to changes in the amounts of essential vitamins and minerals in the horse’s diet. Calcium and phosphorus comprise of 70% of the mineral content of bone while magnesium, copper, zinc manganese, vitamins A and D and other nutrients make up the rest.
Feeding the brood mare particularly in the last trimester with a balanced diet will ensure that the foal receives all the adequate nutrients and minerals for good health, a strong skeletal make-up and a healthy immune system. It is also important to make sure the quality of milk produced is good enough to feed the foal in the first few months.
Following on from that feeding the foal with a balanced ration and good quality forage they will attain all the essential amino acids, vitamins and minerals that they need to help promote good bone and hoof growth.
Exercise is also imperative to the development of bone. Providing a foal with regular turn out and exercise will assist in the laying down of periosteal bone in the cannon bones and other long bones and ensure future resilience and durability. Light exercise will train the skeletal tissues including ligaments, tendons and muscles to accept weight bearing forces imperative to healthy development of the skeletal system and bone conformation.
Once in training, the appropriate level of exercise should stimulate bone tissue, improve skeletal strength, and, in theory, reduce the probability of exercise-associated skeletal injuries. However, as bone is a dynamic tissue, long breaks from training can decrease bone mass and strength and leave the skeletal system vulnerable to DOD’s.
A horse will not achieve its maximum bone mineral content (BMC) until it is 6 years old. Therefore, it is vital that we take the necessary steps to healthy bone formation to avoid DOD’s and injuries. We need to provide a balanced feed and a suitable exercise regime which will ensure good strength and resilience of bone to withstand the activity level it is required for.
Nutrition plays a vital role in the healthy composition of bones and joints. It can have a huge impact on the musculoskeletal health, disease prevention and the future performance of horses. The growing foal passes through three important nutritional phases: nursing, creep feeding, and weaning. Nursing is completely dependent on the dam’s milk and should meet all the foal's nutritional needs until he reaches approximately two months of age. As this quality and quantity wane, creep feeding is needed to supplement the nutrients that may no longer be available in the desired amounts. At this stage, creep feed should contain approximately 14-16% crude protein, 0.7-0.9% calcium, 0.5-0.6% phosphorus, 50-90 ppm (parts per million) copper, and 120-240 ppm zinc.
营养对骨骼和关节的健康构成起着至关重要的作用。它可以对马的肌肉骨骼健康、疾病预防和未来的表现产生巨大的影响。生长中的马驹要经历三个重要的营养阶段:哺乳、匍匐喂养和断奶。哺乳完全依赖于母马的奶水，应该满足马驹的所有营养需求，直到它大约两个月大。随着这种质量和数量的减少，需要爬行取食来补充可能不再以所需数量可用的营养物质。在这一阶段，蠕变饲料应包含约14-16%的粗蛋白质，0.7-0.9%的钙，0.5-0.6%的磷，50- 90ppm(百万分之一)铜，120- 240ppm的锌。
Weaning then must provide all the nutrients the growing horse needs through good quality forage and concentrate feeds. Concentrates should be directly formulated for the growing horse and should contain approximately 14-16% crude protein, 0.8% calcium, 0.5% phosphorus, 50-80 ppm copper, and 100-200 ppm zinc.
As necessary as it is for foals to receive all the nutrients required by the rapid growing body so too must they receive them in adequate amounts. The ratios of certain nutrients can have a knock-on effect on others therefore they must receive the proper ratios between nutrients to ensure successful bone development.
While calcium is imperative to bone growth, excess calcium in the diet can inhibit the absorption of phosphorus in the body. So, while a diet might appear to have an adequate amount of phosphorus, it may not be fully available if the calcium levels are too high. Imbalances in phosphorous whether they are excessive or deficient can lead to osteochondrosis, a DOD that affects the cartilage formation in bone.The correct ratio a foal should receive of calcium and phosphorus is 2:1.Calcium should make up .8% of a weanling’s dry matter intake, and .5% of a yearling’s dry matter intake. Phosphorus should make up .5% of a weanling’s dry matter and .3% of a yearling’s dry matter.
Other nutrient imbalances of zinc, iodine, and copper can also be problematic during growth phases in foals.
There isn’t a “one diet that cures all” when it comes to developmental orthopaedic disease. Feeding the pregnant mare properly, then continuing that well managed feeding for each individual is the best way to try avoid DOD. Giving the young stock a well-balanced diet and sufficient exercise will definitely help in promoting good bone formation, regular farrier visits will also promote good hooves and hopefully prevent any issues that could arise in the future.