Animal Science Division
KVK Tuensang
INTRODUCTION
Among the livestock, pigs are the only species reared for meat purpose and it fits in extremely well with the mixed farming system. They are efficient converter of swill, waste food, slaughter waste and agricultural by-product into food source of high quality protein and thus making them the most profitable livestock enterprise. In the Northeast region of India, pigs are more popular among any other livestock as majority of the people prefer pork.
PROTEIN REQUIREMENTS
Pigs requires a number of essential nutrients to meet their needs for maintenance, growth, reproduction, lactation, and other functions for various classes of swine under average conditions.
Swine require six general classes of nutrients: water, carbohydrates, fats, protein (amino acids), minerals and vitamins. Amino acids (from protein) that exceed the animal’s requirements for maintenance and tissue protein synthesis provide energy.
The protein requirements in swine nutrition were the findings that an exclusive corn diet supplied too little protein both in quality and quantity for the growing pig. These deficiencies were met by the addition of such feeds as milk or milk by-products, fish meal, linseed meal, soybean meal, and similar products. Usually the cost of the protein supplements is higher than that of the cereals. It is not profitable to feed excessive amounts of protein beyond the requirements.
Pigs of all ages and stages require amino acids to build new proteins, such as muscle, which is composed of about 21 different amino acids. There are 10 essential amino acids that must contain adequate amount of amino acids required by pigs for maintenance, growth, reproduction and lactation. Those 10 essential amino acids are arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Two other amino acids (cysteine and tyrosine) are semi essential since both can be synthesized if adequate amounts of methionine and phenylalanine are present for cysteine and tyrosine, respectively. The other nine amino acids (aspartic acid, asparagines, glutamic acid, glutamine, glycine, alanine, proline, hydroxyproline and serine) are considered nonessential because they can be synthesized at sufficient rates if an adequate amount of protein is present in the diet.
Table: Feed Protein Levels Required by Swine
| Ration | Protein % |
| Creep Feeding | 18-20% |
| Growing (50-125 lbs) | 15-16% |
| Finishing (125-240 lbs) | 13-14% |
| Young gilts-boars | 15-16% |
| Older sows-boars | 13-14% |
AMINO ACID SOURCES
The proteins of corn and other cereal grains are deficient in certain essential amino acids for swine. Thus, protein supplements or sources are used in combination with cereal grains to correct the amino acid deficiencies. Soybean meal, cottonseed meal, canola meal, sunflower meal, and peanut meal, animal co-products (meat and bone meal, fish meal, spray-dried egg, blood co-products, poultry meal), grain co-products (dried distill¬ers, and corn gluten meal) or synthetic amino acids attractive for use in pig feed. Soybean meal is the only plant protein that compares with animal protein in terms of quality of amino acid content and can be used as the sole protein based ingredient in most swine diets. Depending on commodity markets, there may be an economical advantage for using both animal and plant
Standard diets are usually formulated to meet the pig’s requirement for lysine (the most limiting amino acid). The amino acid required are during nursery, growing-finishing, gestating females and breeding boars and lactating females. Lysine is used as the base value with other amino acids expressed as the percentage of the lysine requirement. The threonine, methionine, methionine + cysteine and phenylalanine + tyrosine ratios increase as the growing and finishing pig matures due to increased in maintenance needs.
EFFECT OF PROTEIN LEVELS
The effect of feeding protein levels on the production and reproduction for different stages of growth and development are as follows:
1. Effect on new born piglets: The importance of protein starts from the first day of piglet’s life and the required protein is supplied through the sows milk which contains proteins along with vitamins and antibodies which help in getting the pig started soundly. The first milk of the sow i.e. colostrums contains good amount of proteins required for normal weight gain of the piglets and therefore the colostrums should be available to the piglets within the first hour of their birth.
2. Effect on pre-starter pigs: The first feed for the pigs weaned before 3 weeks of age and is supposed to replace milk known as milk replacer. The pre-starter ration is rich in protein and vitamins and low in fibre content. This ration has usually 24 per cent protein. Feeding pre-starter rations to piglets was found to be materially beneficial in that it increased growth rate of pigs and reduce mortality among them. The supplementary feeding reduced the demand on sow’s milk and consequently the sow experiences less weight loss. Piglets start nibbling at food when they are about a week old and by the time they are two to three weeks they will start consuming feed. The milk production of the sow starts declining after third week of lactation. Therefore, it is necessary that the pig is started on a solid feed consisting of high protein by that time to meet their nutritional requirements. This is all the more necessary when the litter size is large and when the sows are in poor condition.
Pre-starter feeds are usually given when the pigs are one week old, weighting 2 to 2.2 kg. This extends usually to a period of two weeks during which each pig consumes one and half to two kilograms of pre-starter ration and gains about three kilograms, to weigh 5.0 kg at the end of the period. These rations are self feed in a trough or feed in a pen separate from that of the mother adjacent to it where the piglets can get in and eat but the sow cannot.
3. Effect on starter pigs: starter ration otherwise known as creep feed should contain 20 to 22 percent protein. The rapid growth of the pigs with the related increase in daily nutrient requirement, combined with the decline in milk yield, necessitates the provision of starter ration. The practice of feeding easily digestible concentrate feed which contains 22% crude protein and 3500 Kcal/kg DM of digestible energy to young piglets while still sucking the mother in a separate enclosure which cannot be accessed by the sow is called ‘creep feeding’. Creep is a device by which piglets are allowed access (creep in) to the concentrate mixture with the exclusion of sow. Creep feeding has pronounced effect on livability as there is significant difference in mortality between those creep fed and not fed. It is fed to piglets between 5.0 to 15.0 kg live weights. This period generally ends when the pigs are eight weeks old.
4. Effect on grower to finisher pigs. This stage is the stage during which the pigs grow from 35 kg to 60 kg body weight. Pigs above 60 kg live weight and until marketing are known as finishing pigs. They need ration containing 13 percent protein.
Recent years have found that tendency toward increased fatness is a matter of concern when pigs are fed low-protein (LP) diets. In response, the use of the net energy system and balanced amino acids for formulation of LP diets has been proposed as a solution to address these concerns and give a better understanding of this nutritional strategy.
In an experiment, the effect of increasing the dietary crude protein (CP) level on the growth performance and carcass characteristics of pigs reared under tropical climatic conditions was determined. They were individually fed one of four test diets based on corn and soybean-oil meal containing 12, 16, 20, and 24% CP, respectively and found that as the dietary CP level increased, dressing percentage and back fat thickness decreased and females were significantly leaner than barrows.
5. Effect on adult male pigs:
A breeding boar requires 2-2.5 kg concentrate per 100 kg body weight depending on the age, condition and breeding demand. The crude protein content of boar ration should be 14%. When compared to other classes of swine, nutritional research focusing on the breeding boar has historically been rather limited. Reasons for this relative lack of attention include the fact that mature boars did, and still do, comprise a relatively small part of the entire swine population. Another factor that may have limited research in this area is the large variation displayed among boars with regard to reproductive characteristics such as semen volume, sperm concentration, sperm motility or measures of sexual behaviour.
According to the NRC (National Research Council), sexually active boars require 260 g of total protein per day. Based on a scientific literature it is concluded that a prolonged period of protein and energy restriction decreases the production of sperm cells. It appears, however, that the deleterious effects of under-nutrition are more pronounced when protein, rather than energy, is limited.
Boars fed on low protein diet required more time to mount the artificial sow and start ejaculating, had shorter duration of ejaculations, and ejaculated less semen than did boars fed the high protein diet. Total sperm output and sperm motility were similar between treatment groups.
Boars consuming high-protein and either high or low energy diets had similar semen and ejaculation characteristics. However, animals in these groups produced 60% more semen and 33% longer durations of ejaculations than did boars consuming the low-energy and low-protein feed.
6. Effect on adult female pigs
Feeding gilts, un-bred sows, pregnant sows, feeding sow at the time of parturition and immediately after parturition and feeding lactating sow:
Dietary protein levels for gestating gilts on reproductive performance was linear increases in litter and piglet weight at lactation as dietary CP (crude protein) level increased. Results indicate that increasing dietary CP level under equal lysine content in gestation increases BW (body weight) of gilts and litter performance but does not affect litter size and milk composition. Feeding over 13% CP diet for gestating gilts could be recommended to improve litter growth.
Protein and amino acids play crucial roles in reproductive performance of sows. An adequate supply of protein and amino acids during gestation allowed sows to maintain their productivity, and that high body protein content of sows could maximize milk production and subsequent reproductive performance. NRC (1998) recommended 12.9% CP in gestation diets for gilts (average 125 kg of BW at breeding). However, modern gilts, genetically improved to have large litter and high milk production, require more nutrients to carry on normal reproductive cycle and body maturation. In a study, restricted dietary protein for gestating gilts did not affect litter size and litter birth weight but caused detrimental effects on litter weight gain although sufficient protein was provided during lactation. On the other hand, high dietary protein for gestating gilts increased litter weight and weight gain and elevated milk yield as well.
Sows fed gestation diets containing higher lysine levels (0.65 to 0.75%) than NRC (1998) recommendation under the same content of CP showed improvements in reproductive performance and litter growth, indicating lysine content in the gestation diets need to be increased. Even though lysine has been considered the first-limiting amino acid in corn-soybean meal diets for sows in gestation and lactation, the other essential amino acids play important roles in the efficiency of protein utilization by gestating sows. Effect of high protein intake in gestation has been reported to increase milk production and BW (body weight) at farrowing and improve subsequent reproductive performance of gilts. In a study, BW of gilts at farrowing tended to be linearly increased by increasing CP level. Studies reported high protein intake in gestation increased sow BW at farrowing, and weight gain in gestation indicating that increasing protein intake in gestation could increase body reserves with protein deposition. Similarly a quadratic increase of daily weight gain of gilts by increasing protein intake in gestation even though protein intake did not affect BW of gilts. A high protein intake in gestation and lactation reduced sow BW loss in lactation. However studies have shown that the sows consumed the same lactation diet during lactation.
Decreasing protein level in gestation diets did not affect total number born but resulted in decreased total number of born alive and increased stillborn piglet. Similar results were reported in which litter size was not affected by dietary protein level in gestation.
Insufficient amino acid content in gestation diets caused failure to normal litter growth in lactation, because of inadequate body protein reserves to produce milk, limitation of mammary gland development and damage to foetuses during gestation. Therefore, high CP level had a positive influence on litter growth but 11% CP level in gestation diet was not sufficient for gestating gilts to maximize piglet growth.
CP levels in gestation diets did not affect proximate composition of colostrum and milk. In contrast, it has been reported that high protein intake in gestation increased protein content in colostrum. Increased litter growth by increasing CP levels in gestation diets might be explained by increase of milk yield, not improvement of milk composition.
Experiment conducted on the effect of protein malnutrition of the sow on reproductive performance were conducted to estimate the effect of protein malnutrition on sow. Gestation gain and birth weights were significantly decreased, but litter size at birth was not significantly affected by feeding the low level of protein to the sow. Weight loss during lactation was significantly greater for dams fed the low-protein diet. Progeny survival to 45 days of age was significantly reduced by protein restriction during gestation and lactation. Pigs from dams fed the high-protein diet gained significantly faster and utilized their feed more efficiently than pigs from dams fed the low-protein diet.
Trial on severe protein restriction during gestation and lactation significantly impairs subsequent reproductive efficiency were observed. The percentage of sows exhibiting oestrus, the average number of days from weaning to oestrus, and the average ovulation rate and uterine weights were significantly lower in sows fed a low-protein diet. Conception rate and embryo survival to 28 days were not significantly affected. The detrimental effects from protein restriction were more severe in younger gilts.
7. Effect of protein during weaning
Weaning is one of the most critical stages in a piglet's life, during which it will face a series of difficulties that must be overcome: separation from its dam, mixing of litters, environment changes, hierarchy fights, exposure to new pathogens... and also a sudden change in diet, from liquid to solid and with a protein content much higher than that of sow's milk. This change in feeding will pose a major challenge to the piglet's still immature digestive system, especially if the feed has high protein content. When this happens, the excess protein ferments in the large intestine and causes a dysbiosis (microbial imbalance) and proliferation (increase in number) of pathogenic bacteria, especially E. coli, causing diarrhoea and delayed growth in the piglet. Therefore, the inclusion of highly digestible raw materials, minimization of protein contents and supplementation with amino acids will help prevent pathogens from colonizing the intestine, reducing the risk of diarrhoea, and facilitating the piglets' development and growth.
When reducing protein levels in the feed, however, it is necessary to ensure the animal receives all the amino acids it needs and that a certain balance between the amino acids is maintained, so that neither the growth nor the production rates are affected. Thus, in order to give the piglet exactly what it needs, the concept of ideal protein, defined as the amino acid profile that maximizes nitrogen retention (i.e., muscle) and covers the animal's physiological and growth needs, is applied when formulating diets.
Conclusion
The requirement of protein for swine is felt at every stages of life of the swine. The essential amino acids are required for maintenance, growth, reproduction and lactation. The proteins of corn and other cereal grains are deficient in certain essential amino acids for swine. Thus, protein supplements or sources are used in combination with cereal grains to correct the amino acid deficiencies. Soybean meal, cottonseed meal, canola meal, sunflower meal, and peanut meal, animal co-products (meat and bone meal, fish meal, spray-dried egg, blood co-products, poultry meal), grain co-products (dried distill¬ers, and corn gluten meal) or synthetic amino acids attractive for use in pig feed. The level of protein inclusion in the swine diets greatly effects the productive and reproductive performance of the animal. From the proper development of foetus to adulthood, from semen quality and quantity and from weaning to finisher, the protein plays an important role at all stages of life. Perhaps of all, the gilts and sows needs the protein most as they are needed for the developing foetus, for milk production, growth and maintenance. Lastly the inclusion of proper level of protein in the diets avoids reproductive failures in both male and females. In case of weaned pigs they attain the proper weight and during finisher stage.
(N.B. the source of contents was collected from articles of different research works carried out by different workers)
