Investigating associations between lamb survival to weaning and dam udder and teat scores

Figures & data

Table 1. Description of the traits and scores used to assess udder morphology in ewes at different times between mating and weaning. Due to small numbers of ewes in some categories, scores were subsequently combined for analyses.

Trait and score	Description	Analysis score
Udder palpation ^a
7	Diffuse hard consistency of udder	Hard
6	Firm consistency of udder with small nodules (lumps) > 2 cm in size	Lump
5	Firm consistency of udder with small nodules (lumps) < 2 cm in size	Lump
4	Soft consistency of udder with small nodules (lumps) > 2 cm in size	Lump
3	Soft consistency of udder with small nodules (lumps) < 2 cm in size	Lump
2	Diffuse firm consistency of udder	Normal
1	Diffuse soft consistency of udder	Normal
Teat palpation^a
5	Teat obstruction (blind teat)	Abnormal
4	Dense, vertical cord in centre of teat (straw)	Abnormal
3	Hard consistency	Abnormal
2	Thickened teat end	Abnormal
1	Soft consistency	Normal
Udder depth^b	Distance between the udder cleft and the abdominal wall, taking the line joining the hocks as a reference
5	Udder cleft at the level of the abdominal wall	5
4		4
3	Udder cleft at hock level	3
2		2
1		2
Udder suspension^b	Ratio of udder attachment width to udder depth
5	Width is much larger than depth	5
4		4
3	Width is equal to depth	3
2		2
1	Width is much narrower than depth	2
Udder separation^b	Separation of the two udder halves.
5	Udder is very clearly divided into two halves	3
4		3
3		3
2		2
1	No separation	1
Teat placement^b	Measure of the external height of the teat cistern, the distance between the teat and the lowest part of the udder.
5	Teat is lateral	5
4		4
3		3
2		2
1	Teat is ventral	2
Clinical mastitis^a
Yes	Visible udder inflammation ± abnormal milk or purulent discharge	Yes
No		No
Lump midline^a
Yes	A superficial lump is located in the midline, immediately cranial to the udder	Yes
No		No
Udder Symmetry^b	Visible symmetry of the udder halves while the udder is hanging naturally
Asymmetrical		Asymmetrical
Symmetrical		Symmetrical

^aEwes examined in a sitting position.

^bEwes examined in a standing position.

Table 2. Number (%) of ewes (n = 981) in one flock that were recorded with different scores for udder traits (see Table 1) on four occasions between mating and weaning.

Trait and score	Pre-mating	Pre-lambing	Docking	Weaning
Udder palpation
Hard	29 (3.0%)	5 (0.5%)	16 (1.6%)	15 (1.5%)
Lump	29 (3.0%)	44 (4.5%)	58 (5.9%)	58 (5.9%)
Normal	923 (94.0%)	932 (95.0%)	907 (92.5%)	908 (92.6%)
Teat palpation
Abnormal-both	9 (0.9%)	12 (1.2%)	231 (23.6%)	208 (21.2%)
Abnormal-one	59 (6.0%)	51 (5.2%)	111 (11.3%)	52 (5.3%)
Normal	913 (93.1%)	918 (93.6%)	639 (65.1%)	721 (73.5%)
Udder depth
5	851 (86.8%)	87 (8.9%)	9 (0.9%)	40 (4.1%)
4	107 (10.9%)	756 (77.1%)	172 (17.5%)	458 (46.7%)
3	9 (0.9%)	132 (13.4%)	711 (72.6%)	444 (45.3%)
2	1 (0.1%)	5 (0.5%)	70 (7.1%)	5 (0.5%)
Missing data	13 (1.3%)	1 (0.1%)	19 (1.9%)	34 (3.4%)
Udder suspension
5	477 (48.6%)	33 (3.4%)	0 (0.0%)	2 (0.2%)
4	357 (36.4%)	351 (35.8%)	35 (3.6%)	240 (24.5%)
3	118 (12.0%)	418 (42.6%)	741 (75.5%)	561 (57.2%)
2	16 (1.6%)	177 (18.0%)	186 (19.0%)	144 (14.7%)
Missing data	13 (1.3%)	2 (0.2%)	19 (1.9%)	34 (3.4%)
Udder separation
3	11 (1.1%)	43 (4.4%)	59 (6.0%)	68 (6.9%)
2	139 (14.2%)	289 (29.5%)	376 (38.3%)	342 (34.9%)
1	811 (82.7%)	643 (65.5%)	505 (51.5%)	521 (53.1%)
Missing data	20 (2.0%)	6 (0.6%)	41 (4.2%)	50 (5.1%)
Teat placement
5	244 (24.9%)	62 (6.3%)	26 (2.7%)	88 (9.0%)
4	211 (21.5%)	273 (27.8%)	205 (20.9%)	258 (26.3%)
3	404 (41.2%)	480 (48.9%)	522 (53.2%)	457 (46.6%)
2	92 (9.4%)	156 (15.9%)	141 (14.4%)	103 (10.5%)
Missing data	30 (3.0%)	10 (1.0%)	87 (8.8%)	75 (7.6%)
Clinical mastitis
Yes	12 (1.2%)	8 (0.8%)	45 (4.6%)	30 (3.1%)
No	957 (97.6%)	972 (99.1%)	919 (93.7%)	921 (93.9%)
Missing data	12 (1.2%)	1 (0.1%)	17 (1.7%)	30 (3.0%)
Lump midline
Yes	11 (1.1%)	5 (0.5%)	25 (2.5%)	31 (3.2%)
No	958 (97.7%)	974 (99.3%)	939 (95.7%)	920 (93.8%)
Missing data	12 (1.2%)	2 (0.2%)	17 (1.7%)	30 (3.0%)
Udder symmetry
Asymmetrical	55 (5.6%)	48 (4.9%)	107 (10.9%)	100 (10.2%)
Symmetrical	914 (93.2%)	932 (95.0%)	855 (87.2%)	847 (86.3%)
Missing data	12 (1.2%)	1 (0.1%)	19 (1.9%)	34 (3.5%)

Table 3. Number of lambs born to ewes in one flock that were recorded with different scores for udder traits (see Table 1) on four occasions between mating and weaning. The number and percentage of lambs in each score category that did not survive to weaning are presented in brackets.

Trait and score	Pre-mating	Pre-lambing	Docking	Weaning
Udder palpation
Hard	52 (16, 30.8%)	10 (1, 10.0%)	31 (11, 35.5%)	29 (9, 31.0%)
Lump	52 (19, 36.5%)	88 (26, 29.6%)	119 (28, 23.5%)	114 (22, 19.3%)
Normal	1,718 (217, 12.6%)	1,724 (225, 13.1%)	1,672 (213, 12.7%)	1,679 (221, 13.2%)
Total	1,822 (252, 13.8%)	1,822 (252, 13.8%)	1,822 (252, 13.8%)	1,822 (252, 13.8%)
Teat palpation
Abnormal-both	17 (5, 29.4%)	21 (7, 33.3%)	434 (44, 10.1%)	404 (26, 6.4%)
Abnormal-one	114 (29, 25.4%)	101 (27, 26.7%)	224 (41, 18.3%)	104 (19, 18.3%)
Normal	1,691 (218, 12.9%)	1,700 (218, 12.8%)	1,164 (167, 14.4%)	1,314 (207, 15.8%)
Total	1,822 (252, 13.8%)	1,822 (252, 13.8%)	1,822 (252, 13.8%)	1,822 (252, 13.8%)
Udder depth
5	1,572 (204, 13.0%)	126 (12, 9.5%)	12 (10, 83.3%)	70 (49, 70.0%)
4	206 (36, 17.5%)	1,410 (189, 13.4%)	281 (72, 25.6%)	814 (87, 10.7%)
3	17 (8, 47.1%)	273 (46, 16.9%)	1,341 (126, 9.4%)	860 (82, 9.5%)
2	3 (2, 66.7%)	12 (4, 33.3%)	150 (24, 16.0%)	13 (6, 46.2%)
Total	1,798 (250, 13.9%)	1,821 (251, 13.8%)	1,784 (232, 13.0%)	1,757 (224, 12.7%)
Udder suspension
5	864 (107, 12.4%)	47 (7, 14.9%)	0 (0, 0.0%)	3 (0, 0.0%)
4	670 (96, 14.3%)	627 (78, 12.4%)	61 (24, 39.3%)	438 (74, 16.9%)
3	232 (39, 16.8%)	789 (107, 13.6%)	1,350 (156, 11.6%)	1,030 (113, 11.0%)
2	32 (8, 25.0%)	357 (58, 16.3%)	373 (52, 13.9%)	286 (37, 12.9%)
Total	1,798 (250, 13.9%)	1,820 (250, 13.7%)	1,784 (232, 13.0%)	1,757 (224, 12.7%)
Udder separation
3	18 (3, 16.7%)	89 (21, 23.6%)	118 (29, 24.6%)	126 (17, 13.5%)
2	251 (46, 18.3%)	538 (65, 12.1%)	708 (90, 12.7%)	630 (66, 10.5%)
1	1,513 (193, 12.8%)	1,184 (160, 13.5%)	916 (103, 11.2%)	971 (138, 14.2%)
Total	1,782 (242, 13.6%)	1,811 (246, 13.6%)	1,742 (222, 12.7%)	1,727 (221, 12.8%)
Teat placement
5	440 (46, 10.5%)	114 (17, 14.9%)	49 (9, 18.4%)	166 (16, 9.6%)
4	409 (55, 13.5%)	510 (65, 12.8%)	392 (44, 11.2%)	473 (60, 12.7%)
3	751 (103, 13.7%)	897 (120, 13.4%)	953 (93, 9.8%)	849 (99, 11.7%)
2	164 (35, 21.3%)	283 (45, 15.9%)	257 (41, 16.0%)	191 (32, 16.8%)
Total	1,764 (239, 13.5%)	1,804 (247, 13.7%)	1,651 (187, 11.3%)	1,679 (207, 12.2%)
Clinical mastitis
Yes	22 (5, 22.7%)	15 (5, 33.3%)	89 (29, 32.6%)	55 (19, 34.6%)
No	1,778 (245, 13.8%)	1,806 (246, 13.6%)	1,699 (207, 12.2%)	1,711 (206, 12.0%)
Total	1,800 (250, 13.9%)	1,821 (251, 13.8%)	1,788 (236, 13.2%)	1,766 (225, 12.7%)
Lump midline
Yes	19 (2, 10.5%)	10 (2, 20.0%)	47 (1, 2.1%)	63 (6, 9.5%)
No	1,781 (248, 13.9%)	1,810 (248, 13.7%)	1,741 (235, 13.5%)	1,703 (219, 12.9%)
Total	1,800 (250, 13.9%)	1,820 (250, 13.7%)	1,788 (236, 13.2%)	1,766 (225, 12.7%)
Udder symmetry
Asymmetrical	102 (25, 24.5%)	97 (27, 27.8%)	215 (62, 28.8%)	193 (46, 23.8%)
Symmetrical	1,698 (225, 13.3%)	1,724 (224, 13.0%)	1,569 (170, 10.8%)	1,564 (178, 11.4%)
Total	1,800 (250, 13.9%)	1,821 (251, 13.8%)	1,784 (232, 13.0%)	1,757 (224, 12.7%)

Table 4. Results of univariate analyses showing the OR (95% CI) for failure of a lamb to survive to weaning for lambs born to ewes in one flock that were recorded with different scores for udder traits (see Table 1) on four occasions between mating and weaning.

Trait and score	Pre-mating		Pre-lambing		Docking	Weaning
Udder palpation
Hard	3.1 (1.8–5.6)		0.7 (0.1–5.9)		3.8 (1.8–8.0)	3 (1.4–6.6)
Lump	4 (2.2–7.1)		2.8 (1.7–4.5)		2.1 (1.3–3.3)	1.6 (1.0–2.6)
Normal	Ref		Ref		Ref	Ref
Teat palpation
Abnormal-both	2.8 (1.0–8.1)		3.4 (1.4–8.5)		0.7 (0.5–1.0)	0.4 (0.2–0.6)
Abnormal-one	2.3 (1.5–3.6)		2.5 (1.6–3.9)		1.3 (0.9–2.0)	1.2 (0.7–2.0)
Normal	Ref		Ref		Ref	Ref
Udder depth
5	Ref		Ref		Ref	Ref
4	1.4 (1.0–2.1)		1.5 (0.8–2.7)		0.1 (0.1–0.3)	0.1 (0.1–0.1)
3	6 (2.3–15.6)		1.9 (1.0–3.8)		0.1 (0.1–0.1)	0.1 (0.1–0.1)
2	13.4 (1.2–148.6)		4.8 (1.2–18.1)		0.1 (0.1–0.2)	0.4 (0.1–1.2)
Udder suspension
5	Ref		Ref		N/A	N/A
4	1.2 (0.9–1.6)		0.8 (0.4–1.9)		Ref	Ref
3	1.4 (1.0–2.1)		0.9 (0.4–2.1)		0.2 (0.1–0.3)	0.6 (0.4–0.8)
2	2.4 (1.0–5.4)		1.1 (0.5–2.6)		0.3 (0.1–0.5)	0.7 (0.5–1.1)
Udder separation
3	Ref		Ref		Ref	Ref
2	1.1 (0.3–4.0)		0.4 (0.3–0.8)		0.4 (0.3–0.70)	0.8 (0.4–1.3)
1	0.7 (0.2–2.5)		0.5 (0.3–0.8)		0.4 (0.2–0.6)	1.1 (0.6–1.8)
Teat placement
5	Ref		Ref		Ref	Ref
4	1.3 (0.9–2.0)		0.8 (0.5–1.5)		0.6 (0.3–1.2)	1.4 (0.8–2.4)
3	1.4 (0.9–2.0)		0.9 (0.5–1.5)		0.5 (0.2–1.0)	1.2 (0.7–2.2)
2	2.3 (1.4–3.8)		1.1 (0.6–2.0)		0.8 (0.4–1.9)	1.9 (1.0–3.6)
Clinical mastitis
Yes	Ref		Ref		Ref	Ref
No	0.5 (0.2–1.5)		0.3 (0.1–0.9)		0.3 (0.2–0.5)	0.3 (0.1–0.5)
Lump midline
Yes	Ref		Ref		Ref	Ref
No	1.4 (0.3–6.0)		0.6 (0.1–3.0)		7.2 (1.0–52.2)	1.4 (0.6–3.3)
Udder symmetry
Asymmetrical	2.1 (1.3–3.4)		2.6 (1.6–4.1)		3.3 (2.4–4.7)	2.4 (1.7–3.5)
Symmetrical	Ref		Ref		Ref	Ref

N/A = not applicable, as there were ≤3 lambs in this category; Ref = the reference category for each variable.

Table 5. Results of final multivariable models^a showing the OR (95% CI) for failure of a lamb to survive to weaning in lambs born to ewes with different scores for udder traits (see Table 1) recorded on four occasions between mating and weaning, with the absolute probability of mortality for lambs born to ewes with different scores.

Trait and score	OR (95% CI)	p-value^b	Mortality (95% CI)
Pre-mating udder palpation
Hard	3.0 (1.5–6.1)	0.003	28.7 (16.6–44.9)%
Lump	4.9 (2.6–9.6)	<0.001	39.9 (25.6–56.3)%
Normal	Ref		11.8 (9.6–14.6)%
Pre-lambing udder palpation
Hard	0.3 (0.1–3.4)	0.359	9.9 (1.2–49.9)%
Lump	1.8 (1.0–3.2)	0.05	27.5 (18.1–39.4)%
Normal	Ref		11.4 (9.8–13.3)%
Pre-lambing teat palpation
Abnormal-both	3.8 (1.2–12.0)	0.024	32.2 (12.9–60.4)%
Abnormal-one	2.1 (1.1–3.6)	0.019	24.5 (15.5–36.4)%
Normal	Ref		11.3 (9.6–13.1)%
Pre-lambing udder symmetry
Asymmetrical	2.0 (1.1–3.6)	0.019	25.7 (17.0–36.9)%
Symmetrical	Ref		11.4 (9.8–13.3)%
Docking udder depth
5	54.8 (9.9–302.2)	<0.001	85.5 (55.4–96.5)%
4	3.2 (1.7–6.2)	<0.001	23.4 (18.1–29.6)%
3	0.8 (0.5–1.4)	0.451	7.9 (6.5–9.6)%
2	Ref		13.6 (8.4–21.3)%
Docking clinical mastitis
Yes	3.0 (1.5–5.9)	0.001	27.7 (16.7–42.2)%
No	Ref		9.6 (8.2–11.3)%
Docking udder symmetry
Asymmetrical	3.3 (2.2–4.9)	<0.001	26.1 (19.7–33.4)%
Symmetrical	Ref		8.5 (7.1–10.2)%
Weaning udder depth
5	9.6 (1.8–51.6)	0.008	72.8 (57.3–84.2)%
4	0.4 (0.1–1.8)	0.231	8.6 (6.8–10.7)%
3	0.3 (0.1–1.3)	0.097	7.5 (5.9–9.6)%
2	Ref		40.2 (13.3–74.6)%
Weaning clinical mastitis
Yes	3.9 (1.3–11.6)	0.013	39.3 (21.2–60.9)%
No	Ref		8.8 (7.4–10.4)%
Weaning udder symmetry
Asymmetrical	2.5 (1.5–4.0)	<0.001	20.7 (14.7–28.5)%
Symmetrical	Ref		8.3 (6.9–10.0)%

^aTraits for each time are those that were included in the final multivariable model for that time, in addition to the explanatory variables lamb sex (male or female), lamb birth rank (single, twin or triplet-born) and lamb birthweight.

^bSignificance of OR.

Ref = the reference category for each variable.