# Presentation: 696756

## Relationship of gestation length to stillbirth

*R.L. Powell,* H.D. Norman, J.R. Wright *
- Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705-2350

- Abstr. M39

- _INTRODUCTION_
- Stillbirth (SB) evaluations have been computed by AIPL since August 2006.
- Research is being reported that may lead to AIPL evaluations for gestation length.
- Relationships of SB with GL are not as well established as with dystocia.

- _OBJECTIVES_
- Examine the factors affecting SB rate among heifers and cows.
- Determine the relationship between SB and GL.

- _CONCLUSIONS_
- SB are highest with short GL, likely because of inadequate calf development and vitality.
- SB are higher for GL longer than average likely because of relationship with dystocia.
- Relationship of dystocia and body condition needs to be added to the study.

- _DATA & METHODS_
- _Edits__:_
- Inseminations initiating gestation must have been after February 1998 and subsequent parturition must have been before January 2006
- Holsteins with >86% breed purity based on AIPL crossbred database
- Gestation length limits of 260-295 days
- Herds with ≥ 15 calvings and at least 3 reported SB
- Matings to identified AI sires only
- _Data:_
- Holstein data from 311,511 heifers and 5,245,251 cows for GL.
- Holstein data from 136,723 heifers and 1,228,270 cows for SB.

- Mean SB rate was 12.3% for heifers and 5.4% for cows; higher for both shorter and longer GL.
- Multiple births increase SB for any GL.

**	**** **
**  *****Year:***			**SB%****	*****Parity/age:******	******	******	*****SB%**
- 	1998		  5.43		 Parity 2
- 	1999		  5.42			<26 mo		5.53
- 	2000		  5.37			26-27 mo	5.37
- 	2001	 	  5.26			28-29 mo	5.25
- 	2002		  5.43			30-31 mo	5.17
- 	2003		  5.44			32-33 mo	5.13
- 	2004		  5.45			34-35 mo	5.09
- 	2005		  5.66			>35 mo		5.34
-    ***Month:******	******	******	******	******	****** ***Parity 3
- 	Jan			  5.19			<42 mo		5.06
- 	Feb			  5.82			42-47 mo	5.16
- 	Mar			  6.19			>47 mo		5.44
- 	Apr			  6.31		 Parity 4
- 	May			  5.88			56 mo		5.35
- 	Jun			  5.09			57 mo		5.71
- 	Jul			  4.79		 Parity 5			5.93
- 	Aug			  4.62		 Parity 6			6.20
- 	Sep			  5.01		 Parity 7			6.61
- 	Oct			  5.22		 Parity 8			7.32
- 	Nov			  5.12		 Parity 9+		6.85
- 	Dec			  5.29
-    ***Parturition Code:******	******	******Days-in-Milk group:***
- 	1 F		    	  5.06		<251			4.91
- 	1 M		          4.68		251-300			4.86
- 	2 F			16.42		301-350			5.12
- 	2M			15.52		351-400			5.60
- 	1F/1M		18.92		401-450			6.02
- 	1F/1 unk	14.31		451-500			6.40
- 	1M/1 unk	16.91	 	>500			7.14
-    ***MEMilk group (1000 kg):***
-    	<8			 6.45
-    	8-10		 5.80
-   	10-12 		 5.43
-   	12-14 		 5.17
-   	>14 	 	 4.93

-  Solutions for SB by effect for cows

- SB 1.5% higher for cows with conceptions in Mar-Apr compared with Jul-Aug; 4.3% higher for heifers in Mar-Apr compared with Aug-Sep
- SB higher for multiple births compared with single births by 3.5 times for cows; 2.3 for heifers.
- SB 2.0% higher for days in milk of > 500 days compared to 250 days
- SB 1.5% higher for milk yields < 6000 kg compared with > 16000 kg
- SB higher for 5th or later parity
- Little effect for conception year

- There was little relationship between daughter PTA for GL and SB; correlations were near 0.2 and significant for service sire PTA.

- 					_RESULTS __*(cont.)*_

- 					_RESULTS __*(cont.)*_

- Trait		PTA GL (cows) 	PTA GL(heifers)
- PTA SSB1			0.212***			0.193**
- PTA DSB1		0.045			0.035
- 1 *Includes all parities     * **** p<.01    *** p<.001**

-  Correlations between this study’s calculated 	service sire SB (SSB) and daughter SB (DSB) 	PTA with February 2007 USDA PTA SB

-   Were moderate (0.73 for SSB, 0.63 for DSB).
-   Differences likely due to differences in editing 	and	model.

- _DATA & METHODS __*(cont.)*_
- _Model__:_
- Fixed effects for conception year, herd-conception year, month of conception, parturition code, lactation length, parity-age and milk yield level.
- Random effects for sire of calf, sire of cow, and cow.

- _RESULTS_
- Stillbirth percent by gestation length for Holstein heifers and cows

- (r = -0.037)
- (r = -0.004)
- (r = -0.128)

- SB solutions for heifers similar for available effects (not displayed)