August 06, 2007	Monday	Rajab 21, 1428

ABOUT 30 - 35 million of the rural population is involved in raising livestock. An average household holding is 2-3 cattle/buffalos, 3-4 sheep/goats and 10-12 poultry per family contributes 35 to 40 per cent of their income. Livestock with almost 50 per cent contribution to agriculture grew reasonably well at 4.3 per cent last fiscal year as against a strong growth of 7.5 per cent in the previous year.

The reason for this slower growth rate of livestock sector is the non-availability of adequate forage. And whatever is available is of poor quality and of less nutritive value. In recent years, advances in plant and animal breeding, introduction of new products, and development of new management approaches have made it possible to increase animal performance. However, for this, to be realised there must be additional focus on forage quality.

Forage quality has a direct effect on animal performance, its value, and ultimately on profits. Adequate nutrition for animal is essential for ample milk production, efficient reproduction, and better profits. However, forage quality varies greatly. Similarly, nutritional needs of animals also vary among and within species and their classes.

Many factors influence forage quality. The most important are forage species, stage of maturity at harvest, and (for stored forages) harvesting and storage methods. Secondary factors include soil fertility and fertilisation, temperatures during forage growth, and variety. Some of the important factors affecting forage quality are as below:

Legumes vs. grasses: Legumes generally produce higher quality forage than grasses. This is because legumes usually have less fibre and favour higher intake than grasses. One of the most significant benefits of growing legumes with grasses is improvement of forage quality from the second cut of a mixed stand. However, applying substantial amounts of nitrogen fertiliser to grasses can improve their crude protein (CP) levels comparable to legume forage.

Cool vs. warm-season grasses: Forage grasses are divided into two broad categories: cool season (adapted to temperate regions) and warm season (best adapted to tropical or subtropical environments). Cool-season grasses include orchard grass, Kentucky bluegrass, perennial and annual ryegrass. Bermuda grass and corn are examples of warm-season grasses. Cool-season species are generally higher in quality than warm-season grasses. The digestibility of cool season grass species averages about nine per cent higher than warm-season grasses.

Minimum crude protein levels found in warm-season grasses are also lower than those found in cool-season grasses. Within each category, annual grasses are often higher in quality than perennials. Due to differences in leaf anatomy (tissue arrangement or structure), warm-season grasses convert sunlight into forage more efficiently than cool-season grasses, but their leaves contain a higher proportion of highly lignified, less digestible tissues.

Temperature: Plants grown at high temperatures generally produce lower quality forage than plants grown under cooler temperatures, and cool-season species grow most during the cooler months of the year. However, forage of any species tends to be lower in quality if produced in a warm region rather than a cool region.

Maturity stage: Maturity stage at harvest is the most important factor determining forage quality of a given species. Forage quality declines with advancing maturity. For example, cool season grasses often have dry matter (DM) digestibility above 80 per cent during the first two to three weeks after growth initiation in spring. There after, digestibility declines by 1D three to 1D two percentage units per day until it reaches a level below 50 per cent. Maturity at harvest also influences forage consumption by animals. As plants mature and become more fibrous, forage intake drops dramatically.

Typical DM digestibility and intake values for cool-season grass hays harvested at different stages of maturity are shown in table 1. Numerous studies have shown similar effects in many different species.

Leaf-to-stem ratio: Reduced leaf-to-stem ratio is a major cause of the decline in forage quality with maturity, and also the loss in quality that occurs under adverse hay curing conditions. Leaves are higher in quality than stems, and the proportion of leaves in forage declines as the plant matures. Reproductive growth lowers leaf-to-stem ratio, and thus forage quality. Most cool-season grasses require a period of cool temperatures for flowering, so they produce reproductive stems only in the spring. Thus, the forage quality of re-growth of these grasses is greater and changes less over time because they have higher leaf-to-stem ratios than first-growth forage. Legumes and some grasses such as Bermuda grass can flower several times each season, so their forage quality patterns are less closely linked to season.

Fertilisation: Fertilisation of grasses with nitrogen (N) often substantially increases yield and also generally increases CP levels in the forage. Fertilisation usually has little or no effect on digestibility. Fertilisation with phosphorus (P), potassium (K), or other nutrients that increase yield may actually slightly reduce forage quality when growth is rapid. Excessive levels of some elements such as potassium may in some cases decrease the availability of other elements such as magnesium (Mg) in the diet.

Variety effects: Some silage corn varieties have higher grain content and digestibility than others. The development of multi-foliate alfalfa varieties (having more than three leaflets per leaf) is a strategy aimed at increasing forage quality, but some multi-foliate varieties have no higher leaf percentage than traditional trifoliate varieties. Some trifoliate varieties exhibit superior quality, but care should be taken to assure that a “high-quality” variety is not substantially lower in yield.

Harvesting and storage effects: Leaf shatter, plant respiration, and leaching by rainfall during field drying of hay can significantly reduce forage quality, particularly with legumes. Rainfall during curing damages legume leaves most. Rain during field drying has less impact on the forage quality of grasses than legumes. Quality losses also occur due to weathering, plant respiration, and microbial activity during storage. In high rainfall areas, losses can be large for round bales stored outside, due to weathering of the outer layers.

Matching forage quality to animal needs: Animal performance is determined by feed availability, feed nutrient content, intake, extent of digestion, and metabolism of the feed digested, but availability and intake most often determine animal performance. A cow never produced milk or a steer never grew on feed that it didn’t eat. With regard to the nutritive content of forage, digestible energy (digestibility) is the most common limiting factor. However, there are times when protein and minerals are the nutrients that limit animal performance, especially in grassing situations when supplementation is impractical. The amounts of digestible energy, protein, vitamins, and minerals needed for maintenance is low relative to other animal processes. In general, forages that contain less than 70 per cent NDF and more than 8 per cent crude protein will contain enough digestible protein and energy, vitamins, and minerals to maintain older animals. Thus, even many low quality forages and crop residues can meet the maintenance needs of some classes of animals, if protein and minerals are adequate.

Following key points should be remembered while managing the forage quality:

The ultimate measure of forage quality is animal performance. Factors having the greatest impact on forage quality are forage species, stage of maturity at harvest, and (if forage is mechanically harvested) harvesting and storage techniques. Forage quality varies greatly among and within forage crops, and nutritional needs vary among and within animal classes and species. Knowing forage quality and animal nutritional needs is necessary to formulate rations that result in desired animal performance.

Leaves are higher in quality than stems; young stems are higher in quality than old stems; and green leaves are higher in quality than dead leaves. In most cases, higher quality is also associated with legumes as compared to grasses; and with cool-season plants as compared to warm-season plants.

Rain during field drying damages legume hay more than grass hay. Also, the dryer the hay when rain occurs, the greater the damage. However, delayed harvest due to concern about rain probably results in more forage quality loss. Fertilising with nitrogen generally increases the crude protein level of grasses, but fertilisation usually has little or no effect on the digestible energy of forage.

Sensory evaluation of forage provides important information. While protein and minerals can limit animal performance, digestible energy is more likely to be the limiting factor from forage.

The more mature and fibrous (lower in quality) forage, the longer it takes to be digested and the less an animal will consume. Major losses in forage quality often occur due to poor storage and feeding techniques. Producing forage with good nutritive value is not enough; good animal performance results when animals consume forage that is suitably high in nutrients and low in fibre.

There is need to supply of pure and quality seed supply to ensure forage of high and nutritional value. The Agricultural Department has to put more emphasis on varieties improvement of fodder crops along with cash crops for enhancing dairy productivity.