1	Historical examination of culling of dairy cows from herds in the United States H. DUANE NORMAN, E. HARE, and J.R. WRIGHT Animal Improvement Programs Laboratory Agricultural Research Service, USDA Beltsville, MD 20705-2350 dnorman@aipl.arsusda.gov 301-504-8334
2	Positive vs. negative terms
3	Selection Natural control vs. Human control
4	“Do we always do the right thing in selection?”
5	“Let’s make sure our dairy animals can continue to reproduce naturally!”
6	Cow population vs. production
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8	Production (quantity, quality) Producers have largely emphasized milk and component yields and type traits We could have selected for sustained production using more fitness traits (had more of the traits been recorded)
9	Maturity rate vs. survival “Has rate of maturity changed over time? How has it affected survival?”
10	What impacts culling?
11	Factors that impact culling rate Management style (Hansen et al., 1998; Washburn et al., 2002; White et al., 2002)
12	Low culling rates Expanding herds (Weigel et al., 2003) Type traits (Caraviello et al., 2003, 2004) Bulk milk SCC (Barkema et al., 1998) SCS (Samore et al., 2003) Crossbreeding (Weigel and Barlass, 2003) Theoretical analysis (Hill, 1980) Economic evaluation (Korver and Remkena, 1979)
13	Longevity definitions True longevity = how long cows actually stay in the herd
14	Longevity periods Two phases: Productive Nonproductive Nonproductive = Birth to first calving Productive = First calving to disposal
15	Productive life Culling dates needed for all animals Genetic evaluation First US national evaluation in 1994 First international Holstein bull rankings for longevity in November 2004 Indirect response from correlated traits
16	Days open phenotypic trend
17	Economic value of longevity Fewer replacement heifers needed to maintain herd size Higher yield near maturity Replacement heifers are better genetically Higher proportion of cows in more profitable lactations
18	Health disorders Big impact on voluntary culling Reproductive and udder problems most likely contributors Risk factors (dystocia, displaced abomasum, mastitis)
19	Reliable health information?
20	Objectives Examine survival rates over time Document how long cows remain in the herd Examine when in the lactation cows are culled Examine why cows are culled Assess the impact of culling
21	Data edits Herds participating in DHI testing for 1 yr prior to first calving and remaining on test throughout the cow’s lactations Cows first calving 1980 to 1994 and remaining in same herd Cows culled for dairy purposes excluded No missing lactations (required 270–650 d between lactations)
22	Opportunity group Subgroups created based on opportunity of each cow to calve at each lactation
23	Cows eligible for opportunity groups
24	Survival rate Defined as fraction of cows that had the opportunity to calve again that did Survival to parity 1 assumed to be 100% as no information was available for heifers
25	Survival to parity 2
26	Survival to parity 3
27	Survival to parity 4
28	Survival to parity 7
29	Survival rates (1966–83)
30	Survival rates (1980-94)
31	Survival rates- Holstein (1980-94)
32	Registered vs. grade survival
33	Herd composition by lactation
34	Herd composition by lactation
35	Holstein herd composition by parity
36	Mean number of parities Additional measure of survival Sum of mean survival rates for parities 1 through 8 transformed to an overall indicator of number of parities (calvings)
37	Mean parities through parity 8
38	Mean number of parities
39	Mean Holstein parities by herd size Cows (no.) 51– 101– 201– 501– 1001– 2001– Year 5–50 100 200 500 1000 2000 5000 1985 3.05 3.02 2.99 3.03 3.02 2.87 2.82 1987 2.95 2.94 2.92 2.95 2.96 2.86 2.60 1989 2.85 2.85 2.85 2.92 2.88 2.83 2.73 1991 2.83 2.82 2.82 2.85 2.89 2.80 2.68 1993 2.82 2.79 2.77 2.80 2.89 2.81 2.76 1994 2.83 2.80 2.75 2.79 2.83 2.79 2.74
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41	Mean Holstein parities by region Mid- Mid- Mtn.- North- North- South- South- Year east west Prairie east west east west 1980 3.24 3.09 3.03 3.43 3.23 3.14 3.22 1982 3.16 2.99 2.96 3.32 3.11 3.13 3.17 1984 3.03 2.91 2.95 3.23 3.04 3.01 3.14 1986 2.97 2.83 2.89 3.14 2.99 2.89 3.03 1988 2.90 2.74 2.81 3.06 2.91 2.82 2.97 1990 2.88 2.73 2.78 3.02 2.90 2.74 2.91 1992 2.80 2.71 2.78 2.95 2.83 2.67 2.90 1994 2.74 2.70 2.74 2.92 2.84 2.59 2.89
42	When are cows culled?
43	DIM at lactation termination
44	DIM at culling for Holsteins first calving 1998–99 by parity
45	Culling probability for cows 1st calving 1998–99
46	Why are cows culled?
47	USDA termination codes assigned to Holsteins not calving again by parity (first calving in 1998 or 1999)
48	Impact of culling
49	Mean calving age across all parities
50	Conclusions
51	Conclusions
52	What dairy producers need
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54	Survival to parity 5
55	Survival to parity 6
56	Survival to parity 8
57	Mean lactations through 8