Nutritional Considerations for Livestock on Rangelands

1
Nutritional Considerations for Livestock on
Rangelands

• Mort Kothmann
• Texas AM University

2
Herbivore Foraging Strategies
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Do animals posses nutritional wisdom?

• What is the evidence?
• Diet quality is higher than the average of forage
  available
• Avoidance of toxic species
• Learned/conditioned behaviors
• Animals remember what they learn

4
How do animals learn what to eat and what not to
eat?

• Pre-natal influences
• From parent
• From peers
• Trial error sampling behaviors
• Anatomical adaptations
• Physiological adaptations

5
Roles of Feedback in Foraging Behavior

• Ingestive effects
• Morphological characteristics of forages
• Learning from post-ingestive feedback
• Concentrations of nutrients
• Concentrations of toxins
• Learning from con-specifics involving
  trans-generational interactions
• Genetic
• In utero
• Lactation
• Observation

Provenza Cincotta (1993)
6
Evidence for Palatability

• Sheep learned to associate flavors with nutrients
  and preference for higher nutrient concentration
• Sheep did not develop an aversion to lower
  nutrient foods
• Cattle learned to prefer protein blocks when
  ingesting forage low in protein

Provenza Cincotta (1993)
7
Evidence for learned avoidance

• Intake of foods decreased as concentration of
  toxin increased
• Decreased intake of foods deficient in essential
  nutrients
• Increase intake of foods that rectify nutritional
  deficiencies

Provenza Cincotta (1993)
8
How do animals learn to associate the flavor of
foods with post-ingestive feedback?

• Food novelty
• Intensity of taste vs concentration of nutrient
• Relative amounts of two foods ingested
• Temporal sequence of food ingestion
• Prior experience with illness
• Prior experience with a salient flavor

Provenza Cincotta (1993)
9
Relating senses to post-ingestive feedback

• Affective processes
• Taste
• Responses are aversive or positive
• Cognitive processes
• Odor and sight
• Combination of odor taste results in stronger
  leaned behavior

Provenza Cincotta (1993)
10
Variation among individuals with a species

• Anatomical
• Congenital
• Environmentally conditioned
• Physiological
• Congenital
• Environmentally conditioned

Provenza Cincotta (1993)
11
Goats and Blackbrush

• Blackbrush is a forage low in protein and high in
  condensed tannins (nutritionally similar to
  liveoak)
• PREFERENCE_Goats reared with mothers on
  blackbrush consumed 95 more than naive goats.
• PHYSIOLOGICAL_Experienced goats excreted 63 more
  uronic acids per unit of body weight
• MORPHOLOGICAL_Experienced goats had 30 greater
  reticulo-rumen mass

Provenza Cincotta (1993)
12
Models for foraging theory

• Darwin and Spencer thought that selection would
  necessarily lead to perfection, but species,
  people, and cultures all perish when they cannot
  cope with rapid change. (Skinner 1981)
• Flexible responses and rapid adaptation are
  primary correlates of survival

Provenza Cincotta (1993)
13
Basic principles of adaptation

• Error-making
• Differential response
• Memory
• (Note These same principles are important in the
  design and use of TGM.)

Provenza Cincotta (1993)
14
Role of Adaptation and Learned Behaviors in
livestock management

• Naïve animals do not function as efficiently in a
  new environment as animals who have one or more
  generations of conditioned experience in that
  environment
• Consider this when selecting and purchasing
  animals

15
Questions?

• What is the source of the drive to eat (forage)?
• What is the source of the feedback responses?
• How does the animal integrate the many positive
  and negative feedback signals generated during
  foraging?
• How does an animal sense a nutrient deficiency
  and match diet selection with foods that rectify
  that deficiency?
• How does an animal decide when to forage and when
  to stop?

16
Factors Regulating Intake of Grazing Animals
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Short-term vs Long-term RegulationP. Faverdin

• Short-term reduction of intake does not
  necessarily indicate long-term reduction.
• Animals require a learning period to adapt to
  changes in diet.
• Dietary preferences shift towards optimum rumen
  functioning, rather than animal nutritional
  requirements as listed by NRC Nutrient
  Requirements

18
Effect of Nutrients on Feed IntakeP. Faverdin

• VFA have short-term effect to depress feed
  intake. All except propionate appear to relate to
  osmolarity.
• Local anesthetics in rumen eliminate effects of
  acetate and butyrate but not propionate.
• Propionate effects differ if infused into jugular
  vein (no effect) or hepatic vein (reduced
  intake). Apparently the effect of propionate is
  mediated in the liver.
• Intestinal digestion of starch and glucose have
  little effect on intake regulation.
• Protein in rumen stimulates intake.
• Fats and other substances that disrupt rumen
  function decrease intake.

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Glucose Insulin in RuminantsP. Faverdin

• Ruminants obtain little glucose from digestion
  products of normal herbivore diets.
• Glucose is synthesized by gluconeogenesis in
  liver.
• Glucose infused into the rumen has little effect
  on intake.
• Insulin infusion produces short-term depression
  of intake for 30 minutes followed by compensatory
  increase in intake following one hour.

20
Role of Dietary Lipids in Intake RegulationP.
Faverdin

• Natural diets of herbivores are low in lipids.
• High levels of lipids in diet disrupt rumen
  functions.
• Infused lipids have immediate proportional
  effects in reducing short-term intake.
• Mobilization of body lipids in response to
  lipolytic substances (B-adrenergic agonists) has
  no short-term effect but does reduce intake in
  the long-term.
• Effect of free fatty acids on appetite in
  ruminants does not seem to be direct and
  mechanisms involved in intake regulation have not
  been identified.

21
Integration of Post-ingestive FeedbackP. Faverdin

• Infusions and other artificial interventions may
  interfere with the animals ability to link
  post-ingestive responses with the diet consumed.
• Animals learn through post-ingestive feedback
  and anticipate the meals post-ingestive
  consequences.
• A treatment that has no effect over the very
  short term may modify the animals feed intake
  over the long term through a learning process.
• Disruption of the animals equilibrium may cause
  short-term decreases in intake that disappear
  after several days, if the animal can adapt to
  the disequilibrium.

22
Role of N ProteinP. Faverdin

• Intake responds to the ratio of proteinenergy in
  diet.
• Very low or greatly increased NH3 in the rumen
  depresses intake.
• Effects of protein on rumen functioning may
  stimulate appetite independently of its effects
  on rumen fill.
• Ruminants prefer diets high in high-quality
  degradable N. (There must be a balance of DIP and
  UIP. MMK)
• Ruminants rapidly learn to prefer diets that
  improve the functioning of the rumen.

23
Intake in relation to forage quality and protein
supplementation

• N content in diet of 1 is required for optimal
  rumen function.
• When diet CP is below 7, intake and forage
  digestibility respond linearly to increases in
  dietary N
• Above 7 CP in the diet, intake responses are
  primarily a function of metabolic responses in
  the ruminant at the tissue level.

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Impact of bypass protein supplementation (/-
urea) on intake of low-quality forages in
different climatic zones
Slide from Gordon Carsten
Studies conducted in tropical or subtropical
climates
Studies conducted in temperate climates
From G. Carstens
Leng, 1990 Nutr Res Rev 3277
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Receptors Involved in Intake Regulation (J.M.
Forbes)

• Receptor locations (stomach, intestines, liver
  and metabolizing tissues)
• Property sensed (volume, osmolality, pH, and
  concentration of specific chemicals in digesta
  and portal blood)
• Integration of signals in central nervous system
  (CNS) determines what food to eat and whether
  feeding should start or stop.

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Gastrointestinal ReceptorsJ.M. Forbes

• Stretch receptors are found in the anterior
  dorsal rumen wall.
• Stretch receptors are also sensitive to
  chemicals, including VFA.
• Physical responses to distension appear to be
  primarily related to short-term regulation
  possibly with cessation of eating at a meal but
  not with initiation of eating.
• There is no fixed physical capacity that limits
  intake. (Forbes 2000 Weston 1982 Pittroff
  Kothmann 1999)

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Osmotic Pressure Receptors
There are receptors in the GI tract that are
sensitive to osmotic pressure, irrespective of
the source. They apparently function to maintain
homeostasis. Significant increases in osmotic
pressure reduce intake. They also function to
regulate flow from the reticulum to the omasum
and to the abomasum. Increased osmotic pressure
in the rumen primarily functions to stop intake
and to increase the flow of digesta within the GI
tract.
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Liver (J.M. Forbes)
The liver is the first organ which can sense and
integrate the products of digestion after they
leave the GI tract. In the ruminant, infusion of
propionate functions to reduce intake similar to
glucose infusion in the non-ruminant. Oxidation
of VFA in liver depresses intake in the ruminant.
Liver receptors appear to be primarily involved
with cessation of individual meals rather than
with long-term regulation of intake. Denervation
of the liver leads to larger less frequent meals.
Higher circulating nutrient levels result in less
frequent meals. Supply of metabolites is
monitored at the porta hepatis (entrance of the
portal vein into the liver).
29
Adipose Tissue
Leptin is a hormone that provides feedback from
levels of fat stores to various physiological
functions that include down regulation of
intake, immune system function, and reproductive
hormones. Leptin is a hormone secreted by adipose
cells in proportion to their size. It circulates
in the bloodstream and influences receptors in
the brain. The discovery of leptin negates the
need for the physical limitation of intake by
crowding of the rumen by fat hypothesis that has
long been postulated to explain why animals
reduce intake as the percentage of body fat
increases above threshold levels.
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Short-Term Regulation
Short-term intake regulation serves to maintain
physiological parameters of the digesta and the
blood within acceptable ranges. Systems that
cause cessation of eating have received the most
research attention. These include physical and
chemical receptors in the rumen and chemical
receptors in the liver. Osmotic and chemical
receptor systems regulate the flow of digesta
through the GI tract. Physical receptors in the
anterior dorsal sac of the rumen may primarily
regulate rumination relative to ingestion. These
systems do not appear to have a significant role
in regulating long-term intake.
31
Long-Term Intake
Systems that initiate eating and stimulate
continued consumption of a meal have received
less attention. These systems appear to be the
primary mechanism for controlling long-term
intake. Positive stimuli may relate to the rates
of nutrient assimilation by metabolic tissues in
the animal. Leptin would provide a negative
feedback. Regulation of long-term intake probably
involves a balance between positive feed-forward
signals and negative feed-back signals.
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Metabolic Regulation of Intake

• Intake is reduced by either severe deficiency or
  excess of a specific nutrient.
• Animals tend to eat protein to match their
  ability to synthesize and utilize protein in body
  tissues and milk
• Animals do not eat to a fixed demand for energy.

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Protein as a regulator of energy utilization

• The availability of protein regulates the use of
  energy for growth, lactation, reproduction, and
  other productive functions. When the supply of
  energy exceeds the availability of protein,
  excess energy in the form of VFA is either stored
  as fat or oxidized by the liver. Both of these
  processes result in negative feedback to intake.

34
General intake regulation(Pittroff Kothmann
1999)
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Potential vs Realized Energy DemandPittroff
Kothmann 1999
Potential energy demand (PED) The animals PED
is determined by its current physiological state
and genetic potential for growth, lactation, and
other productive functions. Realized energy
demand (RED) PED is modified by climatic and
handling stresses, pathogen effects, and
properties of the diet itself (nutrient quantity
and balance over time).
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Effect of physiological function on efficiency of
ME utilization
Physiological ME for Diet ME
Diet ME Body tissue function
maintenance to milk to body to
milk Lactating 122 64.4 74.7 82.4 Nonlactating 10
0 -- 55.0 --
kcal/BW.75
Moe et al. (1981) JDS 641120. Data generated
from energy balance experiments involving
measurements of 350 lactating and 193
nonlactating cows.
Slide from Gordon Carsten
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Effect of physiological function on efficiency of
ME utilization
Slide from Gordon Carsten
Fat Storage
75 lactating
82
55 dry
Milk
Feed
Direct ME use 64
Fat--late lactation 75 x 82 62
Fat--dry period 55 x 82 45
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Impact of VFA profile on efficiency of ME
useInfused VFAs singly or in mixes into rumen of
sheep fed hay diets
Concept established that net efficiency of ME use
for growth was greater for diets providing more
propionate less acetate acid.
Armstrong and Blaxter (1957, 1958, 1961)
Slide from Gordon Carsten
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Effect of basal diet on efficiency of acetate
use--Acetate was infused into rumen of dairy cows
Slide from Gordon Carsten
Exp I both diets pelleted Exp II hay fed in
long form, concentrates fed in meal form (Tyrrell
et al., 1976 EAAP 1957)
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Effect of level of intake on Digestible Energy
Slide from Gordon Carsten
41
Effects of ambient temperature on digestibility
in ruminants

• Average decrease in digestibility per C decrease
  is equal to .18 NRC, 1981
• Occurs in both ruminant and nonruminant animal
  species

Slide from Gordon Carsten
42
Effect of level of metabolizable energy intake on
liver mass
Slide from Gordon Carsten
Liver weight increased 29 g per increase of 1 MJ
of ME
Johnson et al., 1990 J Nutr 120649
43
Effect of level of metabolizable energy intake on
gastrointestinal tract mass
GIT weight increased 61 g per increase of 1 MJ of
ME
Johnson et al., 1990 J Nutr 120649
Slide from Gordon Carsten
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Maintenance Energy Requirements

• Maintenance energy requirement is directly
  related to vital organ mass
• Animals on high plane of nutrition have higher
  vital organ mass
• This principle is very important when shifting
  animals from high plane of nutrition to lower
  nutritional level.

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Supplementation and Monitoring Nutritional Status
of Grazing Animals
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Considerations for Supplementation

• Will the supplement substitute or complement the
  forage intake?
• Feed to meet protein needs and manage to meet
  energy needs
• Feeding for breeding is the most economical
• Design the system to balance the cows annual
  energy budget
• It is more economical to reduce energy demand
  than to try to feed large amounts of energy
  feeds.
• Creep feed calves during last 45 days prior to
  weaning only if part of preconditioning program

47
Molasses-urea vs Concentrated Protein (CP) (e.g.,
Cottonseed or Soybean Cubes)

• Molasses is self-fed CP is hand fed
• Intake of molasses can only be controlled when
  there is not a large energy deficit
• Molasses works best when there is an abundant
  supply of potentially digestible forage
• Do not provide over 1/3 of CP requirement from
  urea
• Hand feeding useful for checking and handling
  animals

48
Feeding Cottonseed Cubes

• Can feed amounts up to 0.3 of BW per day
• Can feed 1, 2, or 3 times per week with
  comparable results
• Feeding after main morning grazing period has
  less effect on grazing behavior
• On low quality forages (forage intake and digestibility
• Can give large increase in DOMI

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Guidelines for using 20 breeder cubes

• Work best if fed daily in the PM with total
  amount not to exceed 0.3 of BW
• Skipping days and feeding larger amounts may
  reduce forage intake and digestibility
• Energy in the cube tends to substitute for energy
  in grazed forage which reduces net benefit to the
  animal
• Feeding daily can disrupt grazing patterns

50
Forero, et al. (1980) J. Anim. Sci.
50532-538.Evaluation of slow-release urea for
winter supplementation of lactating range cows.

• Natural protein was superior to both urea and
  SRU.
• SRU was slightly superior to urea apparently
  because of improved palatability and intake of
  the supplement.
• The 20 CP supplement with urea and corn fed at
  2.44 kg/head/day showed reduced performance
  compared to the soybean supplement fed at 1.22
  kg/head/day.
• Protein supplementation increased forage intake
  with the greatest increase from natural protein.
• Natural protein increased DMD of diet but urea
  did not.
• Urea as the sole source of N is not highly
  effective in enhancing fiber digestion. Animo
  acids and peptides with NH3 are more effective.

51
Forage Intake and DigestibilityEffects of
Supplements

• Forage CP of 6-7 is threshold for major effect
  of supplemental protein
• Starch in the diet has a negative effect on fiber
  digestion primarily through changing rumen pH and
  microbial populations.
• On low CP forages, starch digesting bacteria
  compete with cellulose digesting bacteria for NH3
  in the rumen.

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Monitoring Nutritional Status of Grazing Animals

• Vegetation
• Animal
• Feces

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Integration of Procedures for evaluating
nutritive status of range animals

• Determine forage availability
• Determine nutrient content of diet
• Estimate nutrient requirements of animal
• Determine nature and extent of nutritional
  deficiencies
• Evaluate management practices to determine causes
  and possible solutions

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Range Site
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Monitoring VegetationObservational

• Total amount available
• Forage density and distribution
• Potential bite size
• Nutritional heterogeneity
• Live-dead
• Leaf-stem
• Species composition

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Vegetation Analysis

• Measuring standing crop
• Chemical analyses
• CP, TDN, IVOMD, minerals

57
Monitoring Animals

• Animal body condition score
• Animal weight
• Animal appearance
• Fill, hair coat, eyes, body language
• Animal behavior
• Grazing periods (start and end)

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Feces

• Size of pats
• Shape of pats
• Moisture content of pats

59
Fecal Chemistry Bonds of Carbon
Oxygen Nitrogen Hydrogen

Diet Quality Crude Protein Dig. Org. Matter


Predicted Diet Crude Protein Digestible
Organic Matter
Y ß 0 ß 1x e
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Diet quality as estimated by NIR analysis of
fecal samples from Garfield Co, MT Rangeland
1996-2001
01
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Summary Systems Thinking

• Think holistically
• Climate
• Soils
• Plants
• Animals
• Management
• Work to create synergy between parts of the
  system