ANSC 318 1st Edition Lecture 18 Outline of Last Lecture I. Economic values for cattle and energy requirements of beef cows.Outline of Current Lecture II. Protein Requirements for Beef CowsIII. Mineral Requirements for Beef Cowsa. Trace Mineral NutritionIV. Body Conditioning ScoresV. Feeding Beef Cattlea. Impact of Forage Qualityb. Selecting SupplementsCurrent LectureProtein Requirements for Beef Cows•Protein is needed for maintenance, pregnancy, lactation, and growth (for 1st and 2ndcalf cows only)Mineral Requirements:•Fertility  P, Cu, Zn, Se, Mn•Appetite  Mg, K, Zn, Cu•Nervous System  Mg, P, Cu•Fetal Development  Cu, Zn, Se, Mn•Disease Resistance  Cu, Zn, Se•Hair Coat  Cu, Zn, Se•Skin and Hoof Health  Zn•Milk Production  Ca, P, Mg•Muscle Development  P, S, Zn, Se•Bone Development  Ca, P, Mg, Mn, CuMacromineralsMacromineral Gestating Cows Lactating Cows Maximum LimitCalcium, % *** 1.6 x P 1.6 x P 2.0Phophorous, % *** 0.17 0.24 1.0Potassium, % *** 0.70 0.80 3.0Magnesium, % *** 0.15 0.22 0.40Sodium, % *** 0.10 0.15 --These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Chlorine, % *** 0.25 0.30 --Sulfur, % *** 0.15 0.15 0.40• Calcium and Phosphorous are the most likely to be deficient• Magnesium deficiency = grass tetany• Sodium and Chloride = salt• Sulfur is not usually deficient and is often too high  above 0.30% will impair Copper absorptionMicromineralsMicromineral Gestating Cow Lactating Cow Maximum LimitCopper, ppm *** 17 17 100Zinc, ppm *** 60 60 500Manganese, ppm 70 70 1,000Selenium, ppm *** 0.20 0.30 2Cobalt, ppm 0.20 0.20 10Iodine, ppm 0.60 0.60 50Iron, ppm 87 87 1,000• Cu, Zn, and Se are most likely to be deficient• When Cu is deficient the pigment of hair can be dulled; average levels of most forages are below the requirement line for Zn and Cu• Enhanced Bull Fertility  Cu, Mn, Zn, Se, Vitamin E• Enhanced Cow Fertility /Immunity (Mastitis)  Cu, Mn, Zn, Se, Vitamin E• Maternal Selenium-Vitamin E Supplements shorten the days to estrus after calving, making rebreeding the cow a faster process; they also have a positive effect on fertility• Maternal Trace Mineral Nutritiono Enhanced Cold Tolerance  Cu, Se, Io Enhanced Immune System/Colostral Antibody Transfer  Cu, Co, Se, Vitamin EMineral Supplementation for Beef Cows•free-choice meals, blocks/tubs, liquid supplements•limit-fed energy-protein supplements•injectable vitamin A, D, E, and trace mineralsVitamin Requirements for Beef Cows•Vitamins A, D, and E need to be supplemented•water-soluble vitamins generally do not need supplementation•vitamin A, D, and E supplementation is especially critical when green forages are notavailableVitamin A, D, and E Sources•green forages or hay•synthetic sources (for use in feed supplements)•injectable vitamins•sunlight (vitamin D only)Vitamin Animal Class RequirementFeedlot 2,200Vitamin A Gestating Cow 2,800Lactating Cow 3,900Vitamin D All Cattle 275Vitamin E All Cattle 15 to 60Critical vs. Noncritical Stages of Production: 1. Calving to Breeding:•early lactation (high milk production)•preparing for cow rebreeding (adding weight)2. Breeding to Weaning:•late lactation (lower milk production)•slow fetal growth3. Weaning to start of late gestation:•slow fetal growth•no milk production4. Late gestation:•rapid fetal growth•Ranked highest to lowest  1, 2, 4, 3•Most critical high to low  1, 4, 2, 3•The critical periods (1 and 4) last about 3 months each Body Conditioning Scores•management tool to estimate body fat reserves in cows•used to monitor cow’s energy status•not an effective management tool to access protein, vitamins, or mineral status ofcowsScores Range from 1-9•BCS = 3 (thin)  ribs and backbone are visible•BCS = 5 (moderate)  ribs not visible and evidence of fat cover on each side oftail head•BCS = 7 (Borderline fat)  fleshy appearance, and abundant fat cover on both sides oftail headFeeding Beef CattleUnderfeeding Energy During Late Gestation (Period 4)•Impact on cow reproductive performance•Beef cows with low BCS (</= 4) at calving-cows less likely to reach sufficient body condition during early lactation to have goodreproductive success-lower pregnancy rates-conceive later in breeding season-increased cattle intervalUnderfeeding Energy During Late Gestation (Period 4)•Impact on calf survival•Calves born to low-energy heifers:-lighter at birth-lower survival rate at birth and during neonatal period-higher death losses due to scours Underfeeding Energy During Late Gestation (Period 4)•Impact on calving difficulty in heifersUnderfeeding Energy During Late Gestation (Period 4)•Impact on weak calf syndrome•Calves born to low-protein dams:-weaker and slower to suckle-more susceptible to pathogens and cold stress-higher incidence of morbidity and mortalityUnderfeeding Energy During Postcalving (Period 1)•Impact on cow productivity•cows with low BCS (</=4) at start of breeding-delayed return to estrus following calving-reduced pregnancy rates-conceive later in the breeding season-increased calving interval-lower milk production (weaning BW; minor)-decreased protein = decreased time to estrus (85 days from calving to breeding is ideal)Impact of Forage Quality:•increased protein = increased DMI-drops off with low protein because rumen microbes are being starved of ammonia•increased fiber = decreased DMIBest Way to Evaluate Forage Quality: TDN:CP Ratio•forage TDN:CP ratio = TDN (%) / CP (%)•ideal TDN:CP ratio for rumen microbes = 4 to 5:1•DMI of forage is negatively related to TDN:CP ratio•threshold = 7:1 (if above there will not be enough CP)Supplementation Programs for Grazing Beef Cattle:Decision Process:1. determine cow’s requirements-weight? Breed? Pregnant? -macro and microminerals 2. evaluate forage quality (TDN:CP)3. select supplement based on ideal TDN:CP-select low TDN:CP supplements for low quality forage4. determine target level of supplement intake-supplement intake shouldn’t exceed 0.5% of BW5. select method of supplementation based on costs and laborTypes of Supplements for Grazing Beef Cattle:•meal supplements•liquid supplements•cube supplements•block supplements•tub supplementsIonophores:•Rumensin (monensin), Bovatec (lasalocid), and Gain-Pro (bambermycin)-rumensin