Severe claw lesions in pregnant sows reduce prolificacy and increase litter heterogeneity

Abstract

Background: Claw lesions (CLs) are highly prevalent in sow herds, affecting animal welfare and productivity. This study aimed to evaluate the incidence of CLs in pregnant sows and their impact on litter performance. Additionally, we assessed hair cortisol, cortisone, and oxytocin levels to determine whether CLs cause any stress in sows. The study involved 693 hyper-prolific sows, initially assessed for CLs at farrowing. After weaning, they were housed in individual AI crates, where their hair was shaved. At 28 days post-insemination, pregnant sows were moved to group pens. One week before expected farrowing, sows (n = 507) were transferred to individual farrowing crates where newly grown hair samples were collected, and CLs reassessed. Claw lesion severity was scored from 0 to 3 (SS0: no lesions, SS1: mild, SS2: moderate, SS3: severe). Sows were then classified into 3 categories (CAT): CAT1 (SS0 + SS1), CAT (SS1 + SS2, not SS3), and CAT3 (SS1 + SS2 + SS3). The total number of CL per sow and the final sow score were calculated as the sum of CLs observed on the claws and the sum of all CL severity scores, respectively.

Results: Only 4,1% of sows had no CLs, while 66.5% exhibited moderate to severe lesions (CAT2+CAT3). Sows from CAT3 had the highest CL number and final sow score (p < 0.05) and presented the worst values for total piglets born, piglets born alive, low-weight piglets born ( < 1 kg), proportion of low-weight piglets born per litter, and mean litter weight at birth. However, stress biomarker levels did not differ among categories and were not associated with litter performance.

Conclusions: Our findings indicate that severe CLs impair litter performance and increase litter heterogenicity, particularly the incidence of low-weight piglets born. These effects do not appear to be directly linked to stress biomarker levels but may result from behavioral and physiological disruptions affecting animal well-being derived from the presence of severe CLs. Given the significant economic and welfare implications of severe CLs, further research is needed to elucidate their impact on reproduction and to develop effective protocols to better detect stress and pain in affected sows.

Keywords: Claw lesion; Litter heterogeneity; Sows; Stress biomarkers.

Fig. 1

Frontal and rear pig foot views, showing the anatomical areas evaluated for each claw. Wall: the hard outer layer of each claw, can also be called the hoof horn. Heel: soft keratinized epidermis on the volar surface of the claw. Sole: the bottom portion of the claw, it is slightly softer than the wall and in pigs covers a relatively small area. Heel-sole junction: juncture line between the heel and the sole. White line: the line around the edge of the sole that is the junction between the sole and the wall on the underside of the claw. The toe: the anterior part of the sole. (PP, MP and DP: proximal, medial and distal phalange of the main digit; DC PP, DC MP and DC DP: proximal, medial and distal phalange of the dew claw) [1, 24, 25]

Fig. 2

Experimental design. The study involved 693 hyper-prolific sows, initially evaluated for claw lesions. After weaning, sows were housed in individual AI crates, where their hair was shaved to ensure that hair samples collected at the end of the subsequent gestation period reflected newly grown hair. These samples were subsequently used for biomarker assays. Twenty-eight days post-insemination, pregnant sows were transferred to group gestation pens, and one week prior to the expected farrowing date, they were moved to individual farrowing crates. Claw lesions were reevaluated in the farrowing crates after farrowing, and each sow’s claws were scored for no lesions (SS0) to severe (SS3) lesions. Sows were classified into three categories based on lesion severity: CAT1, CAT2, and CAT3. Prolificacy parameters, along with piglet birth weight (normal or low-weight), were recorded. The number of low-weight piglets born (LWPB) per litter, their proportion, and mean litter weight were calculated for each sow category

Fig. 3

Distribution of sow categories with representative images illustrating claw lesion types and severity scores. Claw lesion types: HOE, heel overgrowth and erosion; WLI, white line injuries; HCW, horizontal cracks on the wall; FHSJ, fissure of the heel-sole junction; ATL, abnormal toe length. Severity scores (SS) were defined as follows: SS0, no lesions; SS1, mild lesions (slight, short, superficial or very small superficial defects or deviations from a healthy claw); SS2, moderate lesions longer or larger but shallow lesions); and SS3, severe lesions (serious and deeper, including severe ulceration extending into the corium). Sows were classified into 3 categories (CAT): CAT1 (SS0+SS1), CAT2(SS1+SS2, not SS3), and CAT3 (SS1+SS2+SS3). ^a,b p < 0.001

Fig. 4

Frequency distribution of different types of claw lesions evaluated. (A) frequency of claw lessions (CLs) relative to the total number of observed lesions (n = 2,900). (B) frequency of CLs in the forelimbs (calculated from the total number of lesions observed in the forelimbs only; n = 1,362). (C) frequency of CLs in the hindlimbs (calculated from the total number of lesions observed in the hindlimbs only; n = 1,538). (HOE) heel overgrowth and erosion; (WLI) white line injuries; (FHSJ) fissure of the heel-sole junction; (ATL) abnormal toe length; (HCW) horizontal cracks on the wall; (VCW) vertical cracks on the wall; (ODC) overgrowth of the dew claw. Different letters (a, b, c, d, e) in the same graphic indicate significant differences (p < 0.01)

Fig. 5

Distribution of claw lesion (CL) types by sow category (CAT1, CAT2, CAT3) and anatomical location. (A) frequency of each CL type relative to the total CL recorded in the forelimbs (n = 1,362) by sow category. (B) frequency of each CL type relative to the total CL recorded in the hindlimbs (n = 1,538) by sow category. a,b,c,d,e,f indicate significant differences (p < 0.05) among CL types within each category; A,B indicate significant differences among CL types within each category between forelimbs and hindlimbs

Fig. 6

Number of claw lesions and final severity score per sow according to sow category (CAT). (A) the number of claw lesions (CLs) per sow was determined by summing the CLs observed in the claws of both forelimbs and hindlimbs, regardless of severity score. (B) the final severity score was calculated by summing the severity scores of all CLs present in the claws of the forelimbs and hindlimbs for each sow