RESEARCH

 

Comparison of external udder measurements of the sheep breeds Improved Valachian, Tsigai, Lacaune and their crosses

Pavol Makovický¹*, Melinda Nagy¹, and Peter Makovický<sup>2

1</sup>J. Selye University, Pedagogical Faculty, Department of Biology, Bratislavska 3322 945 01, Komárno, Slovak Republic.
*Corresponding author (makovicky.pavol@gmail.com).
²Czech University of Life Sciences, Faculty of Agrobiology, Food and Natural Resources, Department of Veterinary Sciences, Kamycka 129 (street) 165 21 Prague 6 - Suchdol, Prague, Czech Republic.

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Morphological udder traits have recently become of greater interest from farmers to researchers. In dairy ewes, the udder is very important due to its physiological and conformational characteristics. External udder traits were measured in ewes (Ovis aries L.) of nine genotypes (355 ewes) created of the basis of Improved Valachian (IV), Tsigai (T), and Lacaune (LC) breeds (six traits; 1185 data for each trait) during the milking period 2002-2008. Udder measurements were assessed for: udder length (UL), udder width (UW), rear udder depth (RUD), cistern depth (CDE), teat length (TL), and teat angle (TA). Data were processed by restricted maximum likelihood (REML) methodology using a MIXED procedure from the SAS statistical package. All studied parameters were influenced by the genotype (P < 0.001), many of them also by the effect of parity and lactation stage. The exactly detected UL, UW and RUD during the lactation and with the age of ewes expand gradually (P < 0.001). Teat length was greater in older ewes (expanding, with the parity). Indicator TA during lactation worsened. Crosses with 25 to 75% share of genetic dairy breeds (in particular with LC, to a lesser extent 'East Friesian' -EF) were in most cases larger than the udder cisterns of purebred ewes T and IV. Purebred LC had the largest udders, with the largest cisterns. In conclusion, crosses with specialized dairy breeds have more suitable udders for machine milking than purebred default breeds (T, IV, LC) and are suitable for machine milking.

Key words: Dairy, ewes, lactation, mammary morphology, Ovis aries, teat, udder measurements.

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INTRODUCTION

The anatomy and morphology of the sheep (Ovis aries L.) udder is well known for many years due to many scientific papers (Sagi and Morag, 1974; Labussiere et al., 1981; Labussiere, 1988; Tenev and Rusev, 1989; Ruberte et al., 1994; Pulina and Nudda, 1996; Pulina et al., 1996; Tatarczuch et al., 1997; Carretero et al., 1999; Pulina et al., 2009). The study of the anatomical structure of mammary gland is useful for improving milk yield (Salaris et al., 2007; Casu et al., 2008; Emediato et al., 2008; Rovai et al., 2008; Kominakis et al., 2009; Blascakova and Porácová, 2009; Sadeghi et al., 2013) and good milking ability (Labussiere, 1988; Bruckmaier et al., 1997; Marnet and McKusick, 2001; Bencini et al., 2003; Dzidic et al., 2004; Marie-Etancelin et al., 2006; Castillo et al., 2008a; 2008b; Makovický et al., 2012; 2013). Animals that store a large proportion of milk in the gland cistern produce more milk, and are more able to tolerate extended milking intervals (Knight and Dewhurst, 1994; Stelwagen et al., 1996; Davis et al., 1998; Ayadi et al., 2003; Salama et al., 2003; 2004; Ayadi et al., 2009; Castillo et al., 2009). There are several factors which may affect udder morphology and, therefore, milking efficiency; these include genotype, number and stage of lactation and milk yield (Fernandez et al., 1995; Dzidic et al., 2004; Ugarte and Gabina, 2004; Casu et al., 2008). Mammary morphology is a key factor for optimizing machine-milking ability in ruminants and its inclusion in dairy sheep improvement programs has been widely recommended (Labussiere, 1988; De la Fuente et al., 1996; Caja et al., 2000; Rovai et al., 2004). The external udder traits have been researched in various dairy sheep breeds and have been investigated by a number of authors ('Churra': Fernandez et al., 1995; 'East Friesian': McKusick et al., 2000; 'Manchega' and 'Lacaune': Rovai et al., 2008; 'Istrian': Dzidic et al., 2004; Prpic et al., 2013; 'Bergamasca': Emediato et al., 2008; 'Kermani': Kahtuei et al., 2008; 'Frizarta': Kominakis et al., 2009; 'Improved Valachian' and 'Tsigai': Makovický, 2009; 'Awassi': Iñiguez et al., 2009; 'Sicilo-Sarde': Ayadi et al., 2011; 'Kivircik', 'Tahirova' and 'Karacabey': Altincekig and Koyuncu, 2011; 'Assaf': Legaz et al., 2011, Perez-Cabal et al., 2013; 'Lori Bakhtiari' breed ewes: Sadeghi et al., 2013). Udder morphological traits in meat breeds ('Chilota', 'Suffolk Down') and their relationship with milk production were studied by Martinez et al. (2011).

The objective of this research was to investigate the external udder measurements in purebred 'Improved Valachian' (IV), 'Tsigai' (T), 'Lacaune' (LC) and their crosses with 25%, 50%, and 75% genetic proportion of LC and 'East Friesian' (EF). The analyses of genetic and non-genetic factors that are expected to influence the udder morphology were also done.

MATERIALS AND METHODS

The experiment was performed during the 7-yr period from 2002 to 2008 in one experimental flock of dairy sheep. Each year the ewes were kept within the same flock and were milked twice a day. Purebred 'Improved Valachian' (IV), purebred 'Tsigai' (T) and purebred 'Lacaune' (LC) ewes, and IV and T crosses with 25%, 50%, and 75% genetic proportion of specialized dairy breeds (SDB) 'Lacaune' and 'East Friesian' (EF) were included in the experiment (IV x SDB 25%, IV x SDB 50%, IV x SDB 75%; T x SDB 25%, T x SDB 50%, T x SDB 75%). In total, we compared the external udder measurements in nine genotypes of ewes (three purebreds and six groups of crossbreds). Most crosses created were based on the breed T respectively IV were two-breeding crosses with 25%, 50%, and 75% of LC breed's genetic proportion. Three-breeding crosses with 25%, 50% and 75% of the genetic contribution of both dairy breeds LC and IV represented for the whole period significantly less of the evaluated population (17 ewes, i.e. about 5% of the population). Ewes included in the experiment represented all nine genotypes in each of the reviewed years on the first, second, third, and higher lactation. Most measurements were made in May and July. Control measurements of ewes' udders size were always conducted after the evening milking, and then after the morning milking. During dairy period at least two but in some years up to four control measurements of milk were performed. Some ewes were included in the experiment in 2 yr or even more years which means that in case of some ewes up to eight control measurements of milk were conducted. For the whole period, we surveyed the exact udder size of 355 ewes. Per each ewe the average from 2.84 to 3.47 of measurements were carried out depending on the monitored indicator. Specific numbers of observations in monitored indicators depending on the genotype, parity and lactation stage are shown in Tables 1 and 2. The methodology used for measuring udder traits (Figure 1) was that described by Milerski et al. (2006). External udder measurements of six traits were made by at least two technicians using ruler, measuring tape, and protractor and they included: udder length (UL), udder width (UW), rear udder depth (RUD), cistern depth (CDE), teat length (TL) and teat angle from the vertical (TA). Statistical analysis was done using the restricted maximum likelihood (REML) methodology (MIXED) procedure as implemented in SAS/STAT v.9.2, (SAS Institute, 2002-2008).

Table 1. Effect of genotype on traits describing external udder measurements of ewes (LSM ± SE).


***P < 0.001; **P < 0.01; *P < 0.05; ns: non-significant effect.
UL: udder length; UW: udder width; RUD: rear udder depth; CDE: cistern depth; TL: teat length; TA: teat angle; SDB: specialized dairy breeds; LSM ± SE: least square means ± standard error.
(100): 'Improved Valachian' (IV); (125): crossbreds of IV breed with 25% genetic proportion of specialized dairy breeds Lacaune (LC) and East Friesian (EF); (150): crossbreds of IV breed with 50% genetic proportion of specialized dairy breeds LC and EF; (175): crossbreds of IV breed with 75% genetic proportion of specialized dairy breeds LC and EF; (200): 'Tsigai' (T); (225): crossbreds of T breed with 25% genetic proportion of specialized dairy breeds LC and EF; (250): crossbreds of T breed with 50% genetic proportion of specialized dairy breeds LC and EF; (275): crossbreds of T breed with 75% genetic proportion of specialized dairy breeds LC and EF; (300): LC.
¹Number of measurements.


Table 2. Effect of parity and stage of lactation on traits describing external udder measurements of ewes (LSM ± SE).

***P < 0.001; **P < 0.01; *P < 0.05; ns: non-significant effect; LSM ± SE: least square means ± standard error; UL: udder length;
UW: udder width; RUD: rear udder depth; CDE: cistern depth; TL: teat length; TA: teat angle.
¹Number of measurements.

Figure 1. Morphological parameters measured on udder and teats.


A: udder length (UL); B: udder width (UW); C: rear udder depth (RUD);
D: cistern depth (CD); E: teat length (TL); a: teat angle from the vertical (TA).

The following statistical model with fixed and random effects was applied:

y_ijklm = μ + Y_i + LS_j + GENk + Pi + an_m + a * DIM_ijklm + e_ijklm

where: y_ijklm is dependent variables studied, such as (UL, UW, RUD, CDE, TL, TA), Y_i is year (fixed effect with five to seven levels; depending on the analyzed indicator 20022008), LS_j is lactation stage (fixed effect with four levels), from 40^th to 99^th lactation day, from 100^th to 129^th lactation day, from 130^th to 159^th lactation day and from 160^th to 210^th lactation day, GEN_k is genotype (breed group; fixed effect with nine levels; see above for characterization), P₁ is parity (fixed effect with three levels; - first, second, third and further parity), an_m is animal (random effect), DIM_ijkin, is days in milk (covariate; 40 to 210 d in milk), e_ijklm is random error. The differences were significant at P < 0.05, P < 0.01, and P < 0.001.

RESULTS AND DISCUSSION

The basic statistical characteristics of the variation of selected parameters characterizing the external udder measurements of ewes for IV, T, LC and their crosses with genetic proportion of LC and EF-25%, 50%, and 75% are shown in Table 3. While measuring the exact udder sizes of ewes (UL, UW, RUD, CDE, TL, and TA) using ruler, measuring tape and protractor, we realized 1185 measurements, and we found extraordinary great variability of values. The lowest average value for the exact udder sizes of ewes was found in the indicator cistern depth on level (25.33 mm), and the highest average value was found in the indicator udder length (248.72 mm). The average udder length is characterized by a relatively large margin, where the minimum value for this parameter was detected at 110 mm and a maximum value at 570 mm. Coefficients of variation were medium high for all indicators, with the exception of CDE indicator, where we found that the coefficient of variation was as high as 61.39%. This means that some cisterns of the monitored ewes were negligible (0 mm), while the cisterns in some ewes were very large (85 mm).

Table 3. Basic statistical characteristics of the variation of
selected parameters characterizing the external udder measurements of ewes.


¹Number of sets of measurements.
SD: standard deviation; CV: coefficient of variability.

Our results show (Table 4) that genotype had a significant effect on all the studied parameters of the exact udder sizes of experimental ewes (P < 0.001). Significant effect of genotype on exact udder sizes of 'Churra' ewes also found Fernandez et al. (1995) and De la Fuente et al. (1996).

Table 4. Covariance analysis of traits describing external udder measurements of ewes.

UL: Udder length; UW: udder width; RUD: rear udder depth; CDE: cistern depth; TL: teat length; TA: teat angle.

As shown in Table 1, the highest average udder length (309.89 ± 4.908 mm) was found in purebred LC ewes. The smallest average udder length (197.29 ± 4.782 mm) was found in purebred T ewes. Lower average values in comparison with our results were indicated by Rovai et al. (2008) for purebred 'Manchega' ewes (12 cm) and LC (11.5 cm), respectively Kahtuei et al. (2008) in 'Kermani' (11.97 ± 0.142), Iñiguez et al. (2009) in 'Awassi' (10.7 cm), and McKusick et al. (2000) for EF ewes (19.7 ± 1.8 cm). On the contrary, higher values in comparison with our results were found by Altinçekiç and Koyuncu (2011), who report the average of UL between (21.32 ± 2.64 to 23.01 ± 2.69 cm) in 'Kivircik', 'Tahirova' and 'Karacabey'.

Purebred LC ewe, as expected, also reached the largest average UW (130.31 ± 1.302 mm). Minimum average UW was found in purebred T ewes (103.51 ± 1.276 mm). Similar results were also report by Fernandez et al. (1995) in 'Churra' (12.18 cm), respectively Altinçekiç and Koyuncu (2011) found the average of UW ranging from (12.28 ± 0.93 to 13.17 ± 1.24 cm) in 'Kivircik', 'Tahirova' and 'Karacabey'. Higher values compared with our results were observed by Emediato et al. (2008) in 'Bergamasca' (from 16.86 to 17.70 cm), Iñiguez et al. (2009) in 'Awassi' (13.5 cm), Kominakis et al. (2009) in 'Frizarta' (14.47 ± 0.11 cm) and Sadeghi et al. (2013) in 'Lori Bakhtiari' ewes (from 15.1 to 18.4 cm). Lower average values in comparison with our results were indicated by Kahtuei et al. (2008) in 'Kermani' (6.02 ± 0.062 cm).

The next monitored indicator was RUD. The comparison between genotype groups shows that the greatest RUD (181.18 ± 2.636 mm) characterizes purebred LC ewes. The smallest average RUD we found, as expected, for purebred T ewes (127.93 ± 2.572 mm). Lower results for RUD indicator were published by Fernandez et al. (1995) in 'Churra' (9.30 cm), respectively by Kahtuei et al. (2008) in 'Kermani' (10.53 ± 0.160 cm) and Ayadi et al. (2011) in 'Sicilo-Sarde' (5.04 ± 0.14 cm). Altinçekiç and Koyuncu (2011) referred to average udder depth ranging from (7.34 ± 0.93 to 7.67 ± 1.41 cm) in 'Kivircik', 'Tahirova' and 'Karacabey' and Emediato et al. (2008) in 'Bergamasca' ewes (from 17.34 to 19.14 cm). Higher results than our own were found by Rovai et al. (2008) in 'Manchega' (19.6 cm) and LC (22.5 cm).

As for the cistern depth (CDE) indicator, our results show that the largest CDE characterized purebred LC ewes (33.41 ± 1.386 mm). In purebred T ewes we found an average cistern depth (17.09 ± 1.350 mm), while the lowest average cistern depth was measured in purebred IV ewes (16.90 ± 1.485 mm). Lower values compared with our results were referred to by Fernandez et al. (1995) in 'Churra' (1.48 cm). Values in accordance with our results were published by Iñiguez et al. (2009) in 'Awassi' (3.4 cm), respectively McKusick et al. (2000) in EF ewes (2.8 ± 1.2 cm). Rovai et al. (2008) found in 'Manchega' 15.6 cm and in the LC breed 27.1 cm. Kominakis et al. (2009) found 3.57 ± 0.13 cm average cistern depth in 'Frizarta' and Sadeghi et al. (2013) in the 'Lori Bakhtiari'ewes (from 1.63 to 3.23 cm).

A greater teat length was observed 36.61 ± 2.098 mm in crosses T x SDB (25% SDB) compared to purebreds LC ewes (33.94 ± 0.552 mm). The lowest average teat length (32.68 ± 0.721 mm) was found in crosses T x SDB (50% SDB). Lower average results of teat length compared with our results were found by Fernandez et al. (1995) in 'Churra' (3.83 cm), Emediato et al. (2008) in the 'Bergamasca' ewes (2.86 to 2.91 cm), Kahtuei et al. (2008) in 'Kermani' (2.64 ± 0.620 cm), respectively Ayadi et al. (2011) at 'Sicilo-Sarde' (18.5 ± 4.9 mm) and Altinçekiç and Koyuncu (2011) in 'Kivircik', 'Tahirova' and 'Karacabey' ranged from (2.68 ± 0.47 to 2.88 ± 0.3 cm). Values in accordance with ours were found by Rovai et al. (2008) in 'Manchega' (42.7 mm) and LC breed at (32.7 mm). Iñiguez et al. (2009) found in 'Awassi' average teat length 3.4 cm, Kominakis et al. (2009) for 'Frizarta' 3.42 ± 0.06 cm and Sadeghi et al. (2013) in the 'Lori Bakhtiari' ewes (from 2.32 to 3.25 cm).

Regarding teat angle, the highest average values for teat angle were found among all genotype groups at crosses T x SDB (50% SDB) at 50.08 ± 1.527; the lowest average teat angle we found in purebred Tsigai ewes (39.40 ± 1.143°). Similar average teat angles were reported in 'Churra' ewes (50.39°) by Fernandez et al. (1995) and Dzidic et al. (2004) in 'Istrian' ewes (from 44 ± 2° to 49 ± 4°), Ayadi et al. (2011) in 'Sicilo-Sarde' (45.2 ± 10.0°), Kominakis et al. (2009) in the 'Frizarta' ewes (51.9 ± 1.4°), respectively. Lower average results compared with ours were measured by Altinçekiç and Koyuncu (2011) in 'Kivircik', 'Tahirova' and 'Karacabey', where average teat angle ranged from (30.72 ± 1.71 to 31.98 ± 2.14°).

Table 2 shows that the factor order of lactation had a statistically significant (P < 0.001) effect on the UL, UW and RUD, on CDE and TL. We found that the largest udders with the largest cisterns had sheep on the third lactation. Older ewes in most cases have significantly greater TL than the first lactation ewes, but during the stage of lactation it became smaller. Similar results were published by Fernandez et al. (1995) and De la Fuente et al. (1996) also, and they note that age, respectively order of lactation increases mammary glands of ewes, but decreases TA.

CONCLUSION

In comparing the observed genotypes of sheep, we found relatively large differences. Our results show that crosses have more suitable udders for machine milking than default breeds ('Tsigai' and, 'Improved Valachian'). The outcome of our research also indicates that specialized dairy breeds ('Lacaune' and, 'East Friesian') are suitable for machine milking, and we can expect better milkability than in the purebred, 'Lacaune' ewes.

ACKNOWLEDGEMENT

This study was written during realization of the project KEGA 016PU-4/2012 "Animal and Human Physiology, Adaptation and Environment".

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Received: 18 May 2013.
Accepted: 3 September 2013.