Livestock Feeding An S 320 Swine Feeding and

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Livestock Feeding An. S 320 “Swine Feeding and Management” Lecture 1: April 13 Dr.

Livestock Feeding An. S 320 “Swine Feeding and Management” Lecture 1: April 13 Dr. John F. Patience Department of Animal Science 201 H Kildee Hall Phone: 294 -5132 Email: jfp@iastate. edu

Applied Swine Nutrition Research Program www. ans. iastate. edu/faculty/jfp/acc/

Applied Swine Nutrition Research Program www. ans. iastate. edu/faculty/jfp/acc/

Objectives 1. To establish and maintain effective two-way communication with the pork industry. 2.

Objectives 1. To establish and maintain effective two-way communication with the pork industry. 2. To implement a research program with a short- to medium-term time line. 3. To fully integrate graduate training at both the M. S. and Ph. D. levels into our research program. 4. To communicate the results of the research program to the pork industry and the academic community.

Our Goal To develop an understanding of high priority nutrition and management issues to

Our Goal To develop an understanding of high priority nutrition and management issues to create solutions and develop strategies that support greater economic success and improved long term sustainability of the pork industry

Research Themes 1. Energy metabolism o How to best supply energy to the pig

Research Themes 1. Energy metabolism o How to best supply energy to the pig o How the pig uses energy for growth 2. Ingredient evaluation o Evaluation of ingredients o Improved approaches to ingredient evaluation 3. Feeding and management o Based on industry input and suggestions

Outline • Concepts of life-cycle feeding of swine • Feeding and management: Sows Ø

Outline • Concepts of life-cycle feeding of swine • Feeding and management: Sows Ø Diet formulation issues Ø Feeding management issues • Feeding and management: Gestation Ø Example diets Ø Diet formulation issues Ø Feeding management issues • Feeding and management: Lactation Ø Example diets Ø Diet formulation issues Ø Feeding management issues

PRODUCTION CONTINUUM What occurs in one phase of production often affects outcomes in later

PRODUCTION CONTINUUM What occurs in one phase of production often affects outcomes in later phases. Or Diagnosing problems in one phase of production often requires consideration of what is happening in earlier phases. Breeding Farrowing Nursery Growout

Life cycle feeding objectives 1. To ensure that the feeding of animals in one

Life cycle feeding objectives 1. To ensure that the feeding of animals in one phase of the production system does not impair production later in life Market Gestation Lactation Growout Nursery

Life cycle feeding objectives 2. By understanding the implications of life-cycle feeding, achieve production

Life cycle feeding objectives 2. By understanding the implications of life-cycle feeding, achieve production objectives at the lowest possible cost

WHAT GETS MEASURED GETS MANAGED OR YOU CANNOT MANAGE WHAT YOU CANNOT MEASURE

WHAT GETS MEASURED GETS MANAGED OR YOU CANNOT MANAGE WHAT YOU CANNOT MEASURE

The decision-making process Perception of Risk versus Perception of Reward

The decision-making process Perception of Risk versus Perception of Reward

Accuracy versus Precision High accuracy High precision Low accuracy High precision High accuracy Low

Accuracy versus Precision High accuracy High precision Low accuracy High precision High accuracy Low precision Source: Rutherford and Moughan, 2000 Low accuracy Low precision

Feeding and Management: Sows

Feeding and Management: Sows

Framework for Developing Feeding Programs Nutrient Requirements Nutrient Supply Feeding Program Profitability Pork Quality

Framework for Developing Feeding Programs Nutrient Requirements Nutrient Supply Feeding Program Profitability Pork Quality Functional Properties Sustainability

Life cycle feeding Ø Gestation feeding affects: Ø Sow condition at farrowing Ø Feed

Life cycle feeding Ø Gestation feeding affects: Ø Sow condition at farrowing Ø Feed intake during lactation Ø Sows that get too fat in gestation eat less in lactation Ø Piglet birth weight Ø Response is very small Ø Cost of feeding the breeding herd Ø Feeding too much feed or too rich a diet increases feed costs with no benefits, possibly detriments Ø Well-being of the sow Ø Thin sows are easily chilled and more susceptible for illness

Life cycle feeding Ø Lactation feeding affects: Ø Sow condition at weaning Ø Affects

Life cycle feeding Ø Lactation feeding affects: Ø Sow condition at weaning Ø Affects subsequent reproduction Ø Litter weaning weights Ø Sows will “milk off their back” but this is both inefficient and ineffective, compared to feeding the sow correctly Ø Cost of feeding the breeding herd Ø Feeding too much feed or too rich a diet increases feed costs with no benefits, possibly detriments Ø Well-being of the sow Ø Thin sows are easily chilled and more susceptible for illness

Tracking actual sow feed usage: Gestation feed Example: 3, 500 sow herd using 1,

Tracking actual sow feed usage: Gestation feed Example: 3, 500 sow herd using 1, 020 tons of gestation feed over 4 months. Average daily gestation feed disappearance = 1, 220 tons X 2, 000 lb/ton 3, 300 crates X 166 days = 2, 440, 000 547, 800 = 4. 45 lb/sow/day

Tracking actual sow feed usage: Lactation feed: Option 1 Example: 3, 500 sow herd

Tracking actual sow feed usage: Lactation feed: Option 1 Example: 3, 500 sow herd with 525 crates farrows 2, 950 litters using 325 tons of lactation feed over 4 months Average daily lactation feed disappearance = 325 tons X 2, 000 lb/ton 525 crates X 122 days = 650, 000 64, 050 = 10. 1 lb/sow/day [Under-estimates actual usage, due to empty crates, or pre-farrowed sows in crates. Must know this information to use the information effectively. ]

Tracking actual sow feed usage: Lactation feed: Option 2 Example: 3, 500 sow herd

Tracking actual sow feed usage: Lactation feed: Option 2 Example: 3, 500 sow herd with 525 crates farrows 2, 950 litters using 325 tons of lactation feed over 4 months Average daily lactation feed disappearance; ave. lactation 19 d = 325 tons X 2, 000 lb/ton 2950 litters X 19 days = 650, 000 56, 050 = 11. 6 lb/sow/day [Over-estimates actual usage, because feed given to sows prior to farrowing is included. Must know this information to use the information effectively. ]

Recommended Nutrient Levels for Lactating Sows and Giltsa NUTRIENT Amount/head/day (g) Amount/ton (%) TID

Recommended Nutrient Levels for Lactating Sows and Giltsa NUTRIENT Amount/head/day (g) Amount/ton (%) TID Lysine TID Met & Cys TID Tryptophan 48 26 9 0. 87 0. 47 0. 16 TID Threonine TID Valine Calcium Available phosphorus Salt 30 43 49 24. 5 0. 55 0. 78 0. 90 0. 45 27 0. 50 a. Assumes 12 lb/day feed intake of a diet containing 0. 87% TID lysine

Dietary TID Lysine Level Based Upon Litter Weaning Weight and Sow Feed Intake Adj.

Dietary TID Lysine Level Based Upon Litter Weaning Weight and Sow Feed Intake Adj. 21 -day litter weaning wt, lb 8 9 10 11 12 100 0. 88 0. 71 0. 64 0. 59 110 1. 02 0. 91 0. 82 0. 74 0. 68 0. 63 1. 03 0. 93 0. 84 0. 77 0. 71 0. 66 1. 04 0. 94 0. 86 0. 80 0. 74 1. 04 0. 96 0. 88 1. 05 0. 97 120 130 140 150 Lactation feed intake, lb/d 13 Lysine, g/d 14 15 TID Total 32 36 37 42 42 48 0. 69 47 53 0. 82 0. 76 52 59 0. 90 0. 84 57 65

Suggested TID Amino Acid Ratios for Sows Lysine Methionine Met & Cys Threonine Tryptophan

Suggested TID Amino Acid Ratios for Sows Lysine Methionine Met & Cys Threonine Tryptophan Isoleucine Valine Gestation 100% 28% 70% 80% 20% 67% Lactation 100% 28% 55% 62% 19% 55% 90%

Recommended Nutrient Levels for Lactating Sows and Giltsa VITAMINS Amount/head/day Amount/ton Vitamin A 60,

Recommended Nutrient Levels for Lactating Sows and Giltsa VITAMINS Amount/head/day Amount/ton Vitamin A 60, 000 USP 10, 000 USP Vitamin D 7, 5000 USP 1, 250, 000 USP Vitamin E 360 IU 60, 000 IU Vitamin Kc 24 mg 4, 000 mg Riboflavin 45 mg 7, 500 mg Niacin 270 mg 45, 000 mg d-Pantothenic acid 150 mg 25, 000 mg Vitamin B 12 0. 21 mg 35 mg 9 mg 1, 500 mg 1. 2 mg 200 mg 3, 000 mg 500, 000 mg 27 mg 4, 500 mg 270 mg 45, 000 mg Folic acid Biotin Choline Pyridoxine Carnitine a. Assumes 12 lb/day feed intake of a diet containing 0. 87% TID lysine c. Menadione

Recommended Nutrient Levels for Lactating Sows and Giltsa TRACE MINERALSb Copper Iodine Iron Manganese

Recommended Nutrient Levels for Lactating Sows and Giltsa TRACE MINERALSb Copper Iodine Iron Manganese Selenium Zinc Chromium a. Assumes b. Trace Amount/head/day (mg) Amount/ton (g) 90 15 1. 6 900 216 1. 6 900 1. 09 0. 27 150 36 0. 27 150 0. 181 12 lb/day feed intake of a diet containing 0. 87% TID lysine minerals and vitamins levels added to the diet

Recommended Maximum Concentrations of Toxin in Swine Diets Pig Dietary Concentration Deoxynivalenol Zearalenone Aflatoxin

Recommended Maximum Concentrations of Toxin in Swine Diets Pig Dietary Concentration Deoxynivalenol Zearalenone Aflatoxin ppm ppb Breeding herd 1. 0 2. 0 100 Young Growing Finishing Young males Old males 1. 0 1. 0 3. 0 20 ---a 200 ---a a Concentration not determined Modified from Michigan State University

Feeding and Management: Gestation

Feeding and Management: Gestation

Example Gestation Diets Mixed parity diet Ingredient Young parity diet Old parity diet Corn-soy

Example Gestation Diets Mixed parity diet Ingredient Young parity diet Old parity diet Corn-soy diet Soy hull diet 1, 626 1, 548 1, 617 291 271 202 Soy hulls --- 100 100 Monocalcium phosphate, 21% P 32 31 31 29 Limestone 28 27 27 29 Salt 10 10 Vitamin premix with phytase 5 5 Trace mineral premix 3 3 Sow add pack 5 5 2, 000 Corn or milo Soybean meal, 46. 5% CP Total

Example Gestation Diets Mixed parity diet Calculated analysis Corn-soy diet Soy hull diet Young

Example Gestation Diets Mixed parity diet Calculated analysis Corn-soy diet Soy hull diet Young Old parity diet TID Lysine, % 0. 56 0. 55 0. 46 Total lysine, % 0. 65 0. 55 TID Lysine: ME ratio, g/Mcal 1. 71 1. 44 TID Methionine: lysine ratio, % 38 38 38 41 TID Met & Cys: lysine ratio, % 78 78 78 85 TID Threonine: lysine ratio, % 76 76 76 80 TID Tryptophan: lysine ratio, % 23 22 22 23 ME, kcal/lb 1, 484 1, 451 Protein, % 13. 7 13. 4 12. 1 Calcium, % 0. 90 Phosphorus, % 0. 66 0. 64 0. 61 Available phosphorus, % 0. 39 0. 38 0. 35 0. 44 0. 42 Available phosphorus equiv, %a a. The available phosphorus equivalency includes the phosphorus release due to inclusion of phytase in the vitamin premix.

Gestation feeding challenges 1. Optimize lifetime sow productivity, as a means of maximizing herd

Gestation feeding challenges 1. Optimize lifetime sow productivity, as a means of maximizing herd profitability 2. Over-feeding sows in gestation reduces feed intake in lactation 3. Under-feeding sows in gestation impairs reproductive performance and animal well-being (shoulder sores) 4. Avoid mycotoxins; this may be the worst place to feed mycotoxin contaminated feed

Gestation feeding targets 1. Body condition score between 3 and 3. 5 – for

Gestation feeding targets 1. Body condition score between 3 and 3. 5 – for ALL sows Ø Avoid sows that are too fat or too thin 2. Backfat levels of 0. 75” to 0. 80” at farrowing (measured at last rib, 2. 5” to 3. 0” off the midline) Ø Avoid bf less than 0. 55” at weaning 3. Adjust feed intake according to body weight and backfat 4. Very thin sows have higher maintenance energy requirements, because they have lower insulation levels and are often more active.

Gestation feeding program 1. Sows must be limit fed during gestation; otherwise they become

Gestation feeding program 1. Sows must be limit fed during gestation; otherwise they become too fat 2. Do not feed more than 4 to 5 lb per day for the first 3 weeks after breeding; excess intake lowers fetal survival 3. Feed 4. 0 to 4. 5 lb of a corn-soybean meal diet per day, adjusting as required for body condition 4. Increase feed allowance by 2 lb during the last 21 days of gestation Ø Increases gut capacity to support maximum intake in lactation Ø Recognizes that most fetal growth occurs during the final 3 weeks of gestation. Ø Exception if over-fat sows

Limit feeding gestating sows Ø Easily accomplished in gestation stalls Ø Automatic drops MUST

Limit feeding gestating sows Ø Easily accomplished in gestation stalls Ø Automatic drops MUST be calibrated regularly, to ensure the sow is receiving what you think she should be receiving. Ø More difficult to achieve in group housing systems Key rule: to successfully feed sows in group housed gestation, remove competition for feed. The greater the competition among sows for feed, the less successful the housing system will be. Ø Options: Ø Electronic sow feeders Ø Walk-in-lock-in feeding stalls Ø Trickle feeders Ø Floor feeding, with multiple drops, spreading out supply of feed throughout the pen. Including dividers within the pen helps Ø

Energy and Feed (lb/day) Required to Maintain Body Weight Sow weight, lb 350 400

Energy and Feed (lb/day) Required to Maintain Body Weight Sow weight, lb 350 400 450 500 550 600 ME, kcal 4, 741 5, 240 5, 724 6, 195 6, 654 7, 103 Dietary energy, kcal/lb 1, 400 1, 500 3. 4 3. 2 3. 7 3. 5 4. 1 3. 8 4. 4 4. 1 4. 8 4. 4 5. 1 4. 7

Energy and Feed (lb/day) Required For Backfat Gain Above Requirement For Maintenance Backfat gain,

Energy and Feed (lb/day) Required For Backfat Gain Above Requirement For Maintenance Backfat gain, mm (in) 0 (0) 3 (. 12) 6 (. 24) 9 (. 35) ME, kcal 342 991 1, 649 2, 307 Dietary energy, kcal 1, 400 1, 500 0. 24 0. 23 0. 71 0. 66 1. 18 1. 10 1. 65 1. 54

Feeding Levels (lb/day) For Gestating Sows Based on Backfat and Weight Category at Breeding

Feeding Levels (lb/day) For Gestating Sows Based on Backfat and Weight Category at Breeding Flank to flank, in Estimated weight, lb < 36. 3 Backfat at breeding, mm (in) 9 -11 (. 35 -. 43) 12 -14 (. 47 -. 55) 15 -17 (. 59 -. 67) > 18 (. 71) > 325 5. 0 (. 20) 4. 4 (. 17) 3. 9 (. 15) 3. 4 (. 13) 36. 4 - 39. 2 325 - 400 5. 5 (. 22) 5. 0 (. 20) 4. 4 (. 17) 3. 9 (. 15) 39. 3 - 41. 8 400 - 475 5. 9 (. 23) 5. 4 (. 21) 4. 9 (. 19) 4. 3 (. 17) 41. 9 - 44. 0 475 - 550 6. 4 (. 25) 5. 9 (. 23) 5. 4 (. 21) 4. 8 (. 20) > 44. 0 550 - 650 6. 9 (. 27) 6. 4 (. 25) 5. 8 (. 23) 5. 3 (. 21) Based on a diet containing 1, 500 kcal ME/lb (corn-soybean meal).

Case study You are managing a large sow herd, and your records indicate that

Case study You are managing a large sow herd, and your records indicate that sow productivity is a modest 23 pigs per sow per year (p/s/y). You realize that financial success is unlikely unless you elevate this level of productivity to at least 26 p/s/y. Reviewing the Pig. Champ records, you note the following: 1. Non-productive sow days (NPD) is well above target (63) 2. Weanling to re-breeding interval is acceptable (5. 8) 3. Percent bred by 7 days is unacceptable (88) 4. Percent repeats is excessive (12) 5. Numbers born and born alive is unacceptable (11. 9/11. 0) You are confident that your genetics and breeding management are capable of achieving your sow productivity target. You take a walk through your gestation barn; what would you expect to see and what feeding and feeding management actions would you undertake to correct the problems?

Feeding and Management: Lactation

Feeding and Management: Lactation

Example Lactation Diets TID Lysine, % Ingredient, lb/ton 0. 80 0. 85 0. 90

Example Lactation Diets TID Lysine, % Ingredient, lb/ton 0. 80 0. 85 0. 90 0. 95 1. 00 1. 05 Corn 1, 435 1, 395 1, 356 1, 316 1, 277 1, 238 Soybean meal, 46. 5% CP 486 526 566 605 645 685 Choice white greasea 0 -5% 0 -5% Monocalcium Phosphate, 21% P 28. 5 28 28 28 27. 5 Limestone 28 27. 5 27 27 Salt 10 10 10 Vitamin premix with phytase 5 5 5 Trace mineral premix 3 3 3 Sow add pack 5 5 5 2, 000 2, 000 Total a If adding fat, substitute for grain on an equal weight basis

Example Lactation Diets Calculated analysis TID Lysine, % 0. 80 0. 85 0. 90

Example Lactation Diets Calculated analysis TID Lysine, % 0. 80 0. 85 0. 90 0. 95 1. 00 1. 05 Total Lysine, % 0. 91 0. 97 1. 02 1. 08 1. 13 1. 19 TID Lysine: ME ratio, g/Mcal 2. 35 2. 49 2. 64 2. 79 2. 93 3. 08 TID Methionine: lysine ratio, % 32 31 30 30 29 28 TID Met & Cys: lysine ratio, % 65 64 62 61 60 59 TID Threonine: lysine ratio, % 69 68 68 67 66 66 TID Tryptophan: lysine ratio, % 22 22 22 ME, kcal/lb 1, 547 1, 547 Protein, % 17. 1 17. 9 18. 7 19. 4 20. 2 20. 9 Calcium, % 0. 90 Phosphorus, % 0. 66 0. 67 0. 68 0. 69 Available phosphorus, % 0. 36 0. 37 Available phosphorus equiv, %b 0. 48 b. The available phosphorus equivalency includes the phosphorus release due to inclusion of phytase in the vitamin premix.

Feed intake One of the greatest challenges in feeding the nursing sow is maximizing

Feed intake One of the greatest challenges in feeding the nursing sow is maximizing feed intake Ø Low feed intake leads to low nutrient intake Ø Low nutrient intake leads to: ü ü Lower weaning weights Loss of sow body condition Increased sow culling Impaired rebreeding and subsequent litter size

Effects of Lactation Feeding Level on Litter and Pig Performance Lactation Feeding Item Restricted

Effects of Lactation Feeding Level on Litter and Pig Performance Lactation Feeding Item Restricted Ad libitum SED Probability, P < 38 40 --- d 3 (start creep) 11. 0 10. 9 0. 3 0. 75 d 21 10. 4 0. 3 0. 93 Mortality, % 5. 9 5. 3 1. 8 0. 76 d 3 (start creep) 39. 3 38. 6 1. 4 0. 53 d 21 125. 1 132. 6 4. 5 0. 10 Total 94. 7 102. 9 3. 9 0. 04 ADG 5. 20 5. 64 0. 21 0. 04 No. of litters Pigs/litter Litter weight, lb Litter BW gain, lb NB – Restricted were fed 25% less than ab libitum

Lactation feeding program Ø Small amount of feed on day of farrowing Ø Ø

Lactation feeding program Ø Small amount of feed on day of farrowing Ø Ø Hungry sows are restless and more likely to over-lay piglets Sows typically will not eat much feed; farrowing room is very warm and fed deteriorates quickly Ø Day 1 – 2: Limit fed modestly; do not want to limit feed very much Ø Days 3+: Keep fresh feed in front of the sows at all times

Feeding Strategy for Lactating Sows Number of 4 -pound scoops to feed at each

Feeding Strategy for Lactating Sows Number of 4 -pound scoops to feed at each feeding from day 0 to 2 of lactation Feeding Feed in feeder AM PM Empty 1 1 < 2 lb 0 0. 5 > 2 lb 0 0 Number of 4 -pound scoops to feed at each feeding from day 2 to weaning Feed in feeder AM Noon PM Empty 2 2 2 < 2 lb 1 1 1 > 2 lb 0 0 1

Factors affecting feed intake - 1 Ø Feed delivery Ø Ø Pigs cannot eat

Factors affecting feed intake - 1 Ø Feed delivery Ø Ø Pigs cannot eat feed that isn’t in front of them! By the 3 rd day of lactation, sows should have feed in front of them all of the time Feeding 3 to 4 times per day is preferred to feeding once or twice. Ø Density of the diet Ø Pigs eat more of a low density (low energy) diet, up to the volumetric capacity of their stomach Ø Temperature Ø High temperature discourages feed intake; low temperature encourages feed intake Ø If the temperature is too cold, or conditions are drafty and damp, part of the energy consumed by the sow will be needed to maintain thermal homeostasis

Factors affecting feed intake - 2 Ø Genetics Ø Some lines of pigs have

Factors affecting feed intake - 2 Ø Genetics Ø Some lines of pigs have a naturally higher appetite. If using a low appetite line of pigs, even greater attention must be directed at maximizing feed intake Ø Palatability Ø It is important to note that the important factor here is what the pig considers palatable, not what the producer “thinks” is palatable. Ø Nutrient balance Ø Imbalances among, for example, amino acids will reduce feed intake Ø Body condition and reproductive cycle feeding Ø If sows are overfed in gestation, they will accrue more body fat and this tends to impair feed intake during lactation

Factors affecting feed intake - 3 Ø Feeder design Ø Large feed troughs tend

Factors affecting feed intake - 3 Ø Feeder design Ø Large feed troughs tend to increase feed intake Ø Wet/dry feeders tend to increase feed intake Ø Access to water Ø Water is particularly critical to a lactating sow Ø A sow weaning 11 piglets at 3 weeks of age weighing 13 lb will be producing an average of 2. 5 gallons of milk per day!

How much lactation feed is enough? Example Ø Piglets are gaining 11. 5 lb

How much lactation feed is enough? Example Ø Piglets are gaining 11. 5 lb during 19 d nursing period Ø Sow is weaning 10. 5 piglets per litter Ø Total weight gain is 120. 8 lb, or (120. 8/19) 6. 4 lb/d Ø Estimated energy req’t is 3. 6 Mcal DE/lb litter gain Ø Daily energy requirement would be (6. 4 X 3. 6) 23. 0 Mcal DE/d, or 21. 9 Mcal ME/d Ø Diet ME content is 1. 45 Mcal ME/lb Ø Therefore, sow must eat 15. 1 lb feed/d Ø Is this possible? Ø If yes, what actions can producer take to maximize intake? Ø If no, what options are available to 1) the sow, or 2) the producer?

Fibre in lactation diets Ø Nursing sows are susceptible to constipation Ø Constipation can

Fibre in lactation diets Ø Nursing sows are susceptible to constipation Ø Constipation can be treated by using: Ø Fiber Ø Wheat midds (± 20%) Ø Soybean hulls (± 10%) Ø Alfalfa meal (± 25%) Ø Sugar beet pulp (7±%) Ø Oats (± 20%) (Risk: Use of fibrous ingredients will lower diet energy density and may compromise sow’s ability to consume sufficient energy Ø Chemical laxatives Ø Mg. SO 4 (Epsom salts: 30 lb/ton) Ø Na. SO 4 (Glauber salts: 60 lb/ton) (Risk: Chemical laxatives are harsh; should be used carefully)

Lactation feeding quandary Ø In order to maximize sow feed intake, she wants the

Lactation feeding quandary Ø In order to maximize sow feed intake, she wants the room kept as cool as possible Ø In order to maximize piglet growth and well-being, they want the room to be kept very warm Ø If the room is kept too cool for the piglets, they will huddle with the sow, increasing the risk of being over-lain Ø Increased mortality due to overlays is often related to a room temperature that is too cool Compromise ü Keep the farrowing room temperature elevated during farrowing and the first 24 to 36 hours post-farrowing, to get the piglets off to a good start. ü Lower the temperature to 68 to 72⁰F thereafter and provide zone heating for the piglets ü Feed intake declines by about 0. 2 lb/d per ⁰F above 68⁰F

Further reading • • Paper 1 Paper 2 Paper 3 Paper 4

Further reading • • Paper 1 Paper 2 Paper 3 Paper 4