reproduction Cow-calf operations: calendar of operations Animal Science 144 Beef Cattle & Sheep Production R. D. Sainz Lecture 05

Transcription

1 Cow-calf operations: reproduction Animal Science 144 Beef Cattle & Sheep Production R. D. Sainz Lecture 05 Cow-calf operations: calendar of operations 1

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3 Anatomy - female Anatomy - male The estrous cycle Estrus Day 1 of the cycle Female is receptive to the male, will stand to be mounted hours (cows), hours (ewes) Cows are polyestrous, ewes may be seasonally anestrous Metestrus Days 1 4 of the cycle Ovulation 4 16 hours after end of estrus Initial development of the corpus luteum Diestrus Days 5 17 of the cycle Functional corpus luteum Blocks LH release, prevents new follicle growth Proestrus Days of the cycle PGF 2α from uterus lyses CL; progesterone drops LH, FSH released from anterior pituitary Follicular growth Estrogen (from Graafian follicle) triggers LH pulse, causes estrus 3

4 The estrous cycle The estrous cycle 4

5 Hormonal control Main drivers: Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) Puberty 8 12 months (Bos taurus) months (Bos indicus) 6 9 months (sheep) related more closely to size than to age (ca. 2/3 mature wt) Gestation days in cows days in ewes gestation length correlated with birth wt (including genetic, nutritional effects) parturition: expulsion of newborn dystocia usually not a problem in sheep, can be a problem due to small dams & large calves correlated to birth wt : pelvic area ratio 5

6 Pelvic area = Height x Width Dystocia Natural breeding vs. artificial insemination Bulls have + lower labor costs + less intensive management + higher conception rates higher feed costs higher initial costs minimum herd size requirements (+/-) AI very intensive management requirements (observation, gathering, etc.) needs experienced labor can be expensive (>$20/dose) + requires good records must feed cows or keep close during breeding season must detect heats (estrus) or synchronize + reduce risk of venereal diseases + can use a variety of bulls in herd + can use best bulls 6

7 Estrus synchronization Why synchronize? facilitate use of AI more uniform calf crop (shorter breeding season) breed heifers earlier basic concept: interrupt estrous cycle & restart, all together Prostaglandin injections cause CL regression and standing estrus in 2 to 3 days. Progestin hormones, released from implants or ingested in feed, mimic progesterone by preventing cycles from occurring as long as they are present in the body. Once removed, the cow comes into estrus in 2 to 3 days. anr-1027/anr-1027.html Effects of nutrition Goal: 12 month calving interval So: 365 days 282 days gestation = 83 days calving-to-conception Post-partum anestrus period: at least days (uterine involution, etc.) 7

8 Body condition scores Extremely thin All skeletal structures are visible No muscle tissue is evident No external fat present, Survival during stress doubtful Weight gain to BCS 5: 260 pounds BCS 1 Very thin Skeletal structures are visible Muscle tissue is evident, but not abundant No external fat present Weight gain to BCS 5: 202 pounds BCS 2 8

9 Thin Upper skeleton is prominent (vertebra, hips, pin bones) Muscle tissue is more abundant Body fat is not obvious Weight gain to BCS 5: 140 pounds BCS 3 Marginal Ribcage backbone junction becoming less visible Hooks and pins becoming less obvious Muscle tissue is abundant Fat is beginning to cover ribs Weight gain to BCS 5: 73 pounds BCS 4 Medium flesh for calving Ideal flesh at weaning Ribcage is only slightly visible Hooks and pins are visible but not obvious Muscle tissue is nearing maximum Fat deposit behind shoulder is noticeable Ribs are covered slightly BCS 5 9

10 Ideal flesh at calving Ribcage is only barely visible Hooks and pins are becoming less prominent Muscle tissue volume is at a maximum Fat deposit behind shoulder is obvious Ribs are covered completely with fat beginning to cover rump Weight loss to BCS 5: 80 pounds BCS 6 Slightly over-conditioned for efficient production Skeletal structures are becoming difficult to identify Fat deposits behind shoulder and at tailhead are obvious Flat appearance is beginning to dominate topline Weight loss to BCS 5: 167 pounds BCS 7 Over-conditioned Skeletal structures are invisible Fat deposits are flattening rump Fat is filling brisket and over shoulder Weight loss to BCS 5: 258 pounds BCS 8 10

11 Obese Flat appearance dominates Brisket is heavy Weight loss to BCS 5: 360 pounds BCS 9 % Cycling By Body Condition 50 Days 1 70 Days 90 Days Thin (BCS 1-3) Moderate (BCS 4-6) Fat (BCS 7-9) From calving. Condition score at calving Number of cows % pregnant 1st 20 days % pregnant 1st 60 days Days of breeding season, not post-partum. 11

12 Number of days from calving to first heat Condition score change after calving to day 90 Condition score at calving (Body condition score scale: 1 = emaciated; 9 = obese) From: Effects of Early Weaning on Cow and Heifer Performance 1st-Calf Heifers Mature Cows Normal weaned Early weaned Normal weaned Early weaned Weight, lbs at early weaning at end of breeding at normal weaning time ,040 Conception rate, % Days from calving to first estrus From: 12

13 Cow-calf operations: health programs Health programs Basic rules: Never inject the rear leg Avoid IM injections Select sub-q products Never change dose without your Vet s O.K. Follow withdrawal times Health programs Vaccination decisions: Probability of each specific disease in the area Age, nutrition and production status of the animals Financial risk of a disease outbreak Manager s ability to find and treat sick animals Cost and benefit of each specific vaccine 13

14 Cows/heifers Before entering the herd (3 to 4 weeks prebreeding): MLV: IBR, BVD, PI3 5 way Lepto+Vibrio 4/7/8 way Clostridia Pre-breeding/post-calving (best 3 to 4 week prebreeding): MLV: IBR, BVD, PI3? (every 3-5 years) 5 way Lepto+Vibrio-oil booster Deworm (fall calving) as needed Cows/heifers Post-breeding: Pregnancy check Scour vaccine (as needed) Heifers need priming dose Deworm as needed (spring calving) 5 way Lepto booster Grub control Lice control as needed Cull: Check withdrawal times Cows/heifers Moved to Calving Pastures (3 to 7 weeks pre-calving): Scour vaccine booster 4/7/8 way Clostridium Vitamin A-D? (spring) best to feed vitamin fortified supplement Lice control as needed 14

15 End of Growing Period: MLV: IBR, BVD, PI3 5 way Lepto 4/7/8 way Clostridial Bulls Pre-breeding (best 3 to 4 weeks pre-breeding): MLV: IBR, BVD, PI3? (3-5 years) 5 way Lepto+Vibrio-oil 4/7/8 way Clostridium Deworm Lice control as needed Breeding Soundness Exam Cull: Check withdrawal times Calves At birth: Dehorn Castrate Dip navel in iodine ID tag If dystocia, milk dam & give calf 1 pint colostrum/20 lbs of calf weight. Prior To Breeding Cow: Dehorn Castrate Implant* Vaccinate** Calves *Use a product designed for calves, following the manufacturer's directions. Never implant bull calves intended for breeding. **Vaccines to consider: 4 way MLV IBR, BVD, PI3, BRSV 2 way modern pasteurella 4/7 way Clostridial 2ml modern product 5 way Lepto? 15

16 Calves Pre-Weaning (2 to 4 weeks): Vaccinate* Weigh calves individually Implant (important if calves will be backgrounded on premises) * May not be as important if calves were vaccinated at the pre-breeding opportunity or if calves will be backgrounded on premises. Calves Vaccines to consider: IBR, BVD, PI3, BRSV* 4/7 Clostridial 2 ml product (include tetanus if banding) 5 way Lepto? 2 way modern Pasteurella* *Select one safe for use around pregnant cows. Calves At Weaning: Weigh all calves individually only if calves will be going through a chute for other management objectives. Background on premise: No vaccines required if two MLV virus and 2- way modern pasteurella pre-weaning vaccines given or unless mixed with other non-vaccinated calves. No implant needed and can deworm in feed if implanted preweaning. Consider revaccinating with modified live IBR, BVD, PI3, BRSV. 16

17 Calves Feedlot: Vaccinate Modified Live Virus: IBR, BVD, PI3, BRSV Clostridial? Lepto? H. somnus? Pasteurella H/M? Replacement Heifers only: Using Brucellosis 1-2 months post weaning will lower combined stresses.) Deworm Implant If implanted at pre-weaning, delay first implant days. Cow-calf operations: replacements From: 17

18 If: You have 100 cows With a 86% calving rate And a 50:50 male:female ratio And you turn over 20% of the cow herd each year 1-5% death loss 15-19% culls Then: You will have 43 bull calves, and 43 heifer calves born each year You need to raise (or purchase) 20 pregnant heifers each year You will need 3 to 5 bulls for breeding Therefore, your herd consists of: 100 cows 5 mature bulls 25 yearling heifers 25 2-year old heifers (factor in 80% calving rate) 86 suckling calves At some point you must select those heifer calves that will be kept as replacements Generally done at weaning Maybe later e.g. take pelvic areas at 12 months of age Use of records know birth weights, dates calculate wt:day of age estimate EPDs for important traits Make sure all vaccinations are done (esp. Brucellosis < 12 mos) 18

19 Raising vs. purchasing replacement heifers Cost of raising a replacement heifer $700 Cost of buying a replacement heifer??? Advantages of buying: Carry more cows (~ 15%) Simplify management Disadvantages of buying: Genetic quality Herd health - potential for disease introduction Heifer development Goal calve as 2-year-olds Must breed by 15 months (3/4 mature wt) Must reach puberty by 12 months (2/3 mature wt) Example: if cows are 500 kg (1100 lbs), then heifers must reach 333 kg (733 lbs) by 12 months 375 kg (825 lbs) by 15 months Effect of body weight on ovulation in yearling Angus-Hereford heifers 40.0% 35.0% 30.0% y = x R 2 = % cycling 25.0% 20.0% 15.0% 10.0% 5.0% 0.0% Average body wt, kg SFREC 2005 (N = 20/group) 19

20 400 y = 0.816x Age, days Wt, kg This means that heifer calves must have an average daily gain of kg/day (1.8 lbs/day) during the first year of life. This is fairly normal during the suckling phase, but will require good nutritional management after weaning, either with good quality pasture and/or the use of supplemental feed. Puberty Weight of Heifers by Breed (Average puberty age months) Breed Wt at breeding Wt at breeding Anticipated 50% cycling (lbs) 90% cycling (lbs) mature wt (lbs) Angus Brangus Charolais Hereford Shorthorn British x British Charolais x British Jersey x British Limousin x British Simmental x British Puberty Weight of Heifers by Breed (Average puberty age months) Breed Wt at breeding Wt at breeding Anticipated 50% cycling (lbs) 90% cycling (lbs) mature wt (lbs) Brahman Santa Gertrudis Brahman x British

21 From: 21

22 CA Range quality NDF TDN CP Range Spring Range Early Summer Range Fall nd Economical growing program for replacement heifers Utilize standing or harvested forages as a major portion of the diet. Heifers may be grown slowly then given higher energy feed to accelerate the rate of gain to achieve the required 65% of mature size by the start of the breeding season. Utilize the highest quality hays and/or the best pastures because young cattle cannot utilize low quality roughage as well as the mature cows. Use an ionophore to improve feed utilization and hasten the onset of puberty. Creep feeding From: 22

23 Negative impact of feeding calves Heifer calves fed a high energy ration before weaning can develop fatty tissue in the udder that consequently lowers milk production, compared to those heifers not fed high energy creep rations. This impairment of future production can occur before the heifer reaches 6 months of age. Adequate (but not excessive) nutrition is needed for the heifer calf to reach sexual maturity by the time she is 13 to 15 months old. 23