Variation in Feed Quality: What To Do When It Declines

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Introduction
Feed ingredients, such as barley and wheat, vary substantially in quality. If the variation in ingredient quality is ignored, the quality of finished feed may vary, resulting in changed feed intake and/or reduced growth performance. Feed ingredient quality is thus a nutritional and economic concern in the pork industry, especially the quality differences that are related to energy intake or protein deposition. Feed ingredient quality is related to its chemical composition and not to physical characteristics (bushel weight). Thus, ingredient chemical characteristics should be analyzed regularly. Analyses can be considered an investment to ensure a predictable growth performance.
Variation in ingredient quality has become increasingly important for the pork industry, because minimizing the differences between actual and calculated quality of finished feed helps to achieve a predictable performance. Diets are formulated using least-cost diet formulation, and safety margins have been included to guarantee minimum dietary nutrient levels. These margins could be reduced if ingredient quality is monitored properly. Analyses or predictions of nutrients with the greatest impact on diet cost or performance (energy, amino acids) is the most effective way to manage variation in ingredient quality, and will likely provide a high return on investment.

Variation in feed quality
Feed ingredient quality is now defined as digestible nutrient content rather than total nutrient content. Most swine nutritionists in western Canada use digestible energy (DE) and digestible amino acids to describe ingredient quality. The nutritional value of ingredients is a function of their digestible nutrient content and the pig’s voluntary feed intake (VFI).
For cereal grains, DE is the most valuable nutrient. Variations in the DE content of western Canadian wheat (range of 630 kcal/kg) and barley (range of 450 kcal/kg) can be large, due to changes in the grain’s energy digestibility. In the last decade, we have related changes in the DE content of wheat and barley to changes in their fibre or non-starch polysaccharide (NSP) content (Zijlstra et al. 1999; Fairbairn et al., 1999). Based on the relations, we have developed equations that predict the DE content for barley and wheat based on their chemical characteristics.

Prediction of wheat DE. Our best equation for the prediction of wheat DE content on a dry matter (DM) basis was based its fibre (neutral detergent fibre; NDF) and protein (CP) content:
DE (DM) = 3,584 + 38.3 x CP (DM) – 16.0 x NDF (DM) (R2 = 0.75)

Prediction of barley DE. Our best equation for the prediction of barley DE content on a DM basis was based on its fibre (acid detergent fibre; ADF) content:
DE (DM) = 3,918 – 92.8 x ADF (DM) (R2 = 0.85)

Use of prediction equations. Theoretically, prediction equations are only valid for the range of chemical characteristics used to create the equation. Some wheat samples from the 2002-harvest have a unique combination of chemical characteristics (CP and NDF) that have not been measured before. Thus, the existing equations to predict the DE content of wheat based on CP and NDF may not be valid for a large portion of the 2002-harvest. The 15 wheat samples used to create the original prediction equations (¨) have a lower CP and NDF contents than some samples from the 2002-harvest (à) (Figure 1). Thus, the existing prediction equations should be used cautiously. Barley and wheat samples from the 2002-harvest should be analysed for their chemical characteristics and DE content in grower pigs to validate and improve upon these prediction equations.

Origin of variation in DE. Barley and wheat available in western Canada vary substantially in their nutritional value. For example, the DE content of 20 barley samples ranged from 2,700 to 3,100 kcal/kg, a range that cannot be explained by the samples’ gross energy (GE) content (Figure 2). The range in wheat or barley DE content is therefore mostly due to a change in energy digestibility. A current hypothesis is that a reduction in DE content or energy digestibility is partly due to higher fibre levels. Consequently, low quality grain samples might therefore be more responsive to treatments that enhance energy digestibility.

Voluntary feed intake. Apart from ranges in DE content, a range of feed intake has been described for Australian wheat in weaned pigs (Cadogan et al. 2000) and western Canadian wheat in broiler chicks (Swift et al. 1998). A range of energy digestibility exists for western Canadian wheat (Zijlstra et al. 1999); however, the range in energy digestibility is not related to changes in feed intake in weaned pigs (Cadogan et al. 2000) or broiler chicks (Swift 1998). The existence of a range of feed intake and energy digestibility in western Canadian wheat fed to weaned pigs has not been confirmed to date. A recent study using 12 Canadian wheat varieties organized into 2 varieties in 6 wheat classes did not show a range in feed intake or growth performance for weaned pigs. However, the wheat samples included in this study did not differ much in fibre content and thus quality (Zijlstra et al. 2003).

Economic implications of ingredient quality
The economic implication of variation in feed ingredient quality was calculated for two scenarios.
Scenario 1. A change in quality will change the economic value of the ingredients. For wheat, the economic impact of a 5% change in the digestible lysine (dLYS) or DE content was calculated for grower pigs. Lysine-HCl (78% dLYS; $2.45/kg) and canola oil (8,800 kcal DE/kg; $0.89/kg) were considered as purified sources of dLYS and DE. Assuming that wheat has a mean nutritional value of 0.29% dLYS and 3,425 kcal DE/kg, a 5% difference in these nutrients will be 0.15 kg dLYS in a tonne of wheat and 171 kcal DE in a kg of wheat. The economic value of the 5% difference is per tonne of wheat is:

For dLYS: (0.15/780) * $2,450 = $0.47/tonne
For DE: (171/8,800) * $890 = $17.29/tonne

The higher economic value for the change in DE compared to digestible lysine verifies that the greatest cost-pressure with least-cost diet formulation is against dietary DE content (Zijlstra et al. 2001).

Scenario 2. If changes in energy content are ignored, pig performance may be affected. An unaccounted for reduction in dietary DE content and thus DE intake may reduce gain if feed intake is not increased, or may reduce feed efficiency if feed intake is increased to maintain the DE intake. The following estimates of costs were made for a 7% reduction in DE intake, using data from an energy intake study.

A reduction in gain of 70 grams per day results in pigs that are 8 kg lighter at slaughter after 16 weeks in the grower-finisher barn. The lower body weight at marketing would result in a loss of $10.56 per pig sold, assuming a market price of $1.50/kg and an average index of 110.

An increase in feed intake of 7%, to compensate for the reduced dietary DE content, may increase feed conversion by 0.2 kg feed per kg gain, which would increase feed costs by $2.95 per pig sold.

Change in diet formulation
Reaching a predictable performance is important to maximize net income. But to reach a predictable performance the actual diet DE content should be close to the calculated diet DE content. Thus, diet formulation must be adjusted with a decline in feed ingredient quality. Thus, low quality grains can be used effectively in swine diets, considering:

Ingredient DE content has been predicted using chemical analyses (or perhaps NIRS);

The ingredient specifications have been altered during least-cost diet formulation;

The diets have been re-formulated to ensure that the dietary DE content required for a predictable performance is met. For example, if the predicted barley DE content is lower than the average book value for barley DE, additional energy in the form of canola oil or tallow should be added to the diet to ensure that that actual dietary DE content is at the desired level.
Only then can the grower-finisher pig achieve the energy intake required to maintain protein deposition.

Value-added processing
As discussed previously, the variation in barley or wheat DE content is mostly due to a change in energy digestibility and not a change in gross energy. A decrease in energy digestibility has been linked to an increase in fibre content (Zijlstra et al. 1999; Fairbairn et al., 1999). Therefore, ingredient or diet processing techniques that increase energy digestibility might add nutritional and economic value to low quality wheat or barley. Value-added processing of low quality ingredients might include reducing particle size by grinding more finely (Oryschak et al 2002) or supplementation of fibre-degrading enzymes (Zijlstra et al. 2000).
Regular grinding results in a mean particle size of 700 to 900 microns; however, there may be merit in reducing the particle size of low quality grain to 600 microns or below. Due to the higher fibre content in low quality wheat or barley, supplementation of enzymes to digest fibre might be more beneficial in ingredients with a low or normal DE content compared to ingredients with a high DE content. The impact of value-added processing should be validated using the 2002-harvest, although some indication can be given for the expected improvement in DE content using value-added processing (Zijlstra et al. 1998),

Summary
The 2002-harvest in western Canada was poor. The amount harvested was below average and contained a large proportion of low quality grains. This manuscript focused on determining wheat and barley quality and the possible actions to take after identification of low quality grain. Possible actions include changing diet formulations and/or using value-added processing.

Implications
The quality of low quality grains, especially their DE content, may be predicted using equations based on chemical characteristics. The existing prediction equations should be used cautiously for now, and be validated using the 2002-harvest. Changing diet formulation might allow the use of low quality ingredients by introducing a larger portion of energy-providing ingredients. Value-added processing might further increase the effective use of low quality wheat or barley in swine diets, because their DE content will be increased and a lesser amount of expensive energy-providing ingredients will have to be included in the diet to meet the desired dietary DE content. Low quality wheat or barely may form a large proportion of the diet; thus, accurate prediction of their DE content is important. Further flexibility may be introduced by reducing the proportion of low quality grains in the diet and by including a number of other ingredients.

Effect of wheat sample, particle size and xylanase supplementation on energy digestibility of wheat fed to grower pigs

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The feed processing procedures grinding and enzyme supplementation were tested to reduce the existing variability in DE content of heat. Particle size reduction and xylanase enzyme supplementation increased energy digestibility of wheat and partially reduced the variation in energy digestibility.

Listeria monocytogenes occurrence and characterization in meat-producing plants

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Effect of retention time on gas production and fertilizer value of biodigester effluent

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Comparison of injuries in sows housed in gestation stalls versus group pens with electronic sow feeders.

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Most of the challenges to housing pregnant sows are to balance between providing enough space for free movement and control aggression. Both inadequate space and aggression can cause injuries in sows. There are mainly 2 types of gestation housing systems: individual stalls and group housed pens. Individual stalls may not provide adequate space, but preventing sows from aggression. Group housing, on the other side, provides open space for free movement, but not preventing sows from aggression. The current study was to compare the location and severity of injuries in pregnant sows housed in individual gestation stalls with that in pregnant sows housed in groups in pens with electronic feeders. A total of 100 pregnant sows in parity 1 to 3 were used. Fifty sows each were randomly allotted to gestation stalls or group pens with electronic feeders. Injures were scored on the basis of location, number, and depth of wounds. Injury scores for sows in both housing systems were compared during a period of 90 days. The influence of factors such as duration of stay in the housing system, parity, and body weight on sow injuries was also examined. The results indicated that injury scores were higher in group pens. As body weight increased, injury scores decreased for sows housed in group pens and increased for sows housed in gestation stalls. To evaluate welfare of pregnant sows in individual stalls vs. in group pens, multiple measurements are needed.

Grouping and social preferences in calves, heifers and cows.

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In order to improve animal welfare, a growing number of calves, heifers and dairy cows are reared in loose housing systems. However, regrouping unfamiliar animals may result in aggressive interactions and distress. Increased knowledge about grouping and social integration would make it possible to develop effective management techniques that reduce the amount of problems occurring during social integration of cattle. The aim of this paper is to review recent literature on social integration of calves, heifers and cows and how this is influenced by early social environment, group size, introduction method and competition level. Grouping unfamiliar animals is found to increased aggression, social stress, locomotion behaviour and to have negative effects on feed intake and milk yield. Problems related to social integration are normally higher for the introduced animals than the resident animals. Previous social experience, number of animals that are mixed and the group composition are important factors that can influence social integration. Calves reared in groups are more social confident and show less fear than calves reared in single boxes or in isolation. Repeated grouping seem to accustom the animals to these procedures.

Behavioural and adrenocortical responses of dairy cows toward novel food: effects of food deprivation, milking frequency and energy density in the daily ration.

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One aspect of farm animal adaptability is behavioural and physiological responses toward challenging situations, often implying elements of novelty. Dairy cows show strong behavioural responses when presented with novel food and the behavioural responses reflect the degree of novelty in the food and have an acceptable repeatability. In the present study two experiments were conducted to examine whether the behavioural responses toward novel food were affected by short-term food deprivation or whether the metabolic load in terms of increased milking frequency and decreased energy density in the food affected behavioural and adrenocortical responses of dairy cows toward novel food. The effects of metabolic load and 12 h of food deprivation on the behavioural and physiological responses toward novel food were examined in dairy cows provided with 4 kg of carrots as novel food. In Experiment 1, effects of 12 h of food deprivation were tested using dairy cows provided with 4 kg of carrots as novel food after 0 h versus 12 h of food deprivation. Food deprivation did not affect the approach-avoidance behaviour toward novel food but led to increased attempts to steal usual food from neighbours as well as decreased self grooming. In experiment 2, effects of milking frequency and energy density in the food on behavioural and physiological responses toward novel food were examined. The cows were milked either twice or three times daily. The energy in the food after calving was low or high. An extra daily milking affected the approach-avoidance behaviour of the cows as shown by reduced time spend away from the novel food and reduced frequency of sniffing the novel food. Low energy density in the food led to increased time spent away, increased latency to eat novel food, decreased food intake and a higher proportion of cows performing self-grooming. Provision of novel food did not affect the plasma concentration of cortisol sampled after food provision, and no differences were found between treatments. In conclusion, 12 h of food deprivation did not affect behavioural responses toward novel food in dairy cows, suggesting that this test of behavioural responses toward novelty is rather insensitive toward day-to-day changes in eating motivation. Low energy density in the daily ration and increased milking frequency affected the behavioural, but not the adrenocortical responses toward novelty but there was no evidence for a simple relationship between the energy balance of dairy cows and their responses toward novel food.

Dairy cattle's choice of handling treatments in a Y-maze.

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Farm animals are often subjected to aversive handling, which can result in them becoming fearful of the person handling them and, in some circumstances, of people in general. This fear can increase handling problems and injuries to both animals and handlers, and reduce animal welfare and productivity. In contrast, gentle handling can reduce animals’ fear of people. However, it is not known exactly what types of handling are the most aversive or the most rewarding for animals. The purpose of this study was to assess dairy cattle’s preferences for handling practices by allowing animals to choose treatments in a Y-maze. Animals were first trained to expect one treatment on one side of the maze and another treatment on the other side of the maze. Animals were then allowed to choose between the two sides. In all experiments treatments were balanced for arm of the maze, color of clothing and handler. In the first experiment we validated the use of the Y-maze, using 34 heifers who chose between a) pail feeding versus control, b) hit/shout versus control and c) hit/shout versus pail feeding. Heifers chose pail feeding more often than control in treatment a), and control more than hit/shout in treatment b), and pail feeding more than hit/shout in treatment c). This demonstrates that animals can choose between treatments. In a second experiment, 24 cows were given choices between various handling treatments thought to be aversive a) shout versus hit, b) shout versus cattle prod, and c) control versus tail twist. No significant difference was found in any of the three comparisons. In a third experiment, 16 cows were used to determine if cows had a preference for hand feeding versus control and gentling versus control. Meanwhile twenty-four heifers were used to determine if a preference existed for gentling, pail feeding, or hand feeding over control. Cows showed no preference between control and gentling treatments but chose feeding by hand more often than control. In contrast, heifers showed no preference between control and hand feeding but chose pail feeding more often than control treatment. Heifers also showed no preference between control and gentling. In a fourth experiment, 24 cows were used to compare talking in a gentle voice versus control, gentle voice versus shouting, and shouting versus control. Cows showed no preference between talking in a gentle voice and control but chose control and talking in a gentle voice more often than shouting. Cattle can choose between handling treatments and the Y-maze is an effective method for determining cattle’s preferences. Shouting and the use of cattle prods are aversive; tail twisting is not aversive, if done gently. Feeding is rewarding although, for heifers, feeding by hand may not be. There was no evidence found that gentle or being spoken to in a gentle voice is rewarding for cattle.

Familiarity and group size affect emotional stress in Japanese Black heifers.

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The cattle in this study were exposed to three types of stressors while in the presence of other heifers. The other animals were either familiar with the observed cattle, or unfamiliar. The observed animal was in the presence of either 1 or 4 other cattle during the tests. The study was designed to determine if the presence of familiar vs unfamiliar animals, and the effect of number of other cattle, on the response to stress. The animals were stressed by having a strange object placed in front of them, by being surpised by a sudden loud sound, and by being provided a bucket of feed in such a way that they could not reach the food. All of the tests resulted in some indicators of stress. In general, the presence of familiar animals reduced the stress response of the animals, compared to having unfamiliar animals present. Also, the effect of familiar animals was greater in groups of five (4 plus subject) than when only one other animal was present. In conclusion, stressful events are less stressful if an animal is in a social group of familiar cattle, and a larger group reduces the stress even further.

Repeatability of litter traits of Nigerian indigenous sows

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