Synergy Factors in the Analysis of Lamb Survival

Figures & data

Figure 1. The increase of odds ratios for female vs male lambs (1/0) for different combinations of inbreeding and birth type for Polish Merino (A) and and Wielkopolska sheep (B).

Figure 2. The increase of odds ratios for single vs multiple birth (1/0) for different combinations of sex and inbreeding for Polish Merino (A) and and Wielkopolska sheep (B).

Figure 3. The increase of odds ratios for inbred vs non-inbred lambs (1/0) for different combinations of sex and birth type for Polish Merino (A) and and Wielkopolska sheep (B).

Table 1. The description of data structure used in the analysis.

Sex	Inbreeding	Birth type	PM			WS
			Survived	Dead	Total	Survived	Dead	Total
f	NF	M	221(95)	344(121)	565(216)	707(451)	388(207)	1095(658)
f	NF	S	2493(747)	1495(380)	3988 (1127)	3092 (2072)	1140(614)	4232 (2686)
f	F	M	109(43)	4 (0)	113(43)	417(158)	17(11)	434(169)
f	F	S	676(294)	86(18)	762(312)	1226(774)	147(125)	1373(899)
m	NF	M	22(6)	20(3)	42(9)	88(63)	89(65)	177(128)
m	NF	S	378(127)	353(123)	731(250)	825(516)	484(320)	1309(836)
m	F	M	8(3)	3(2)	11(5)	58(16)	4(1)	62(17)
m	F	S	118(46)	26(9)	144(55)	403(189)	58(37)	461(226)
Total			4025 (1361)	2331(656)	6356 (2017)	6816 (4239)	2327 (1380)	9143 (5619)

PM, Polish Merino breed; WS, Wielkopolska sheep breed; f, female; m, male; NF, no inbreeding; F, inbreeding; M, multiple birth; S, single birth. Numbers of individuals per subclass in a reduced dataset are in brackets.

Table 2. Percentage of survived lambs of both breeds.

Breed	f	m	NF	F	S	M	Total
PM	64(69)	57(57)	58(61)	88(93)	65(70)	49(54)	63(67)
WS	76(78)	68(65)	69(72)	90(87)	75(76)	72(71)	75(75)

f, female; m, male; NF, no inbreeding; F, inbreeding; M, multiple birth; S, single birth; PM, Polish Merino breed; WS, Wielkopolska sheep breed. Numbers of individuals per subclass in a reduced dataset are in brackets.

Table 3. Odds and odds ratios.

Sex	Inbreeding	Birth type	PM		WS
			Odds	OR	Odds	OR
f	NF	M	0.64 (0.79)	Ref	1.82 (2.18)	1.84 (2.25)
f	NF	S	1.67 (1.96)	2.60 (2.50)	2.71 (3.37)	2.74 (3.48)
f	F	M	27.25 (87.00)	42.42 (110.69)	2.53 (14.36)	24.81 (14.82)
f	F	S	7.86 (15.92)	12.24 (20.25)	8.34 (6.19)	8.43 (6.39)
m	NF	M	1.10 (1.86)	1.71 (2.36)	0.99 (0.97)	Ref
m	NF	S	1.07 (1.03)	1.67 (1.31)	1.70 (1.61)	1.72 (1.66)
m	F	M	2.67 (1.40)	4.15 (1.78)	14.50 (16.00)	14.66 (16.51)
m	F	S	4.54 (4.89)	7.06 (6.23)	6.95 (5.11)	7.03(5.27)

PM, Polish Merino breed; WS, Wielkopolska sheep breed; OR, odds ratio; f, female; m, male; NF, no inbreeding; F, inbreeding; M, multiple birth; S, single birth; ref, the group was assumed as reference, for which OR is equal to 1. Numbers of individuals per subclass in a reduced dataset are in brackets.

Table 4. Estimates of regression coefficients and the corresponding synergy factors.

Variables	PM		WS
	Regression coefficients	SF	Regression coefficients	SF
Sex	0.538 (0.860)	-	0.611^** (0.810**)	-
Inbreeding	3.748^**(4.707**)	-	2.685^** (2.804**)	-
Birth type	0.954** (0.916)^**	-	0.545^** (0.509**)	-
Sex-inbreeding	-2.862^** (-4.989**)	0.057^** (0.007**)	-0.086 (-0.918)	0.918 (0.399)
Sex-birth type	-0.981^** (-1.503*)	0.375^** (0.222*)	-0.147 (-0.072)	0.863 (0.931)
Inbreeding-birth type	-2.197^** (-2.614*)	0.111^** (0.073*)	-1.280^* (-1.651)	0.278^* (0.192)
Sex-inbreeding-birth type	2.756^** (4.453**)	15.732^** (85.909**)	-0.196 (0.372)	0.822 (1.450)

PM, Polish Merino breed; WS, Wielkopolska sheep breed; SF, synergy factor.

*P=0.05

**P=0.01. The results for a reduced dataset are in brackets.