Evolution of udder morphology, alveolar and cisternal milk compartment during lactation and their relationship with milk yield in Najdi sheep

Abstract

A total of 30 multiparous Najdi ewes were used to study the evolution of udder morphology traits and milk fractions in the udder during suckling (3rd, 6th, 9thwk) and milking (10th, 11th, 12thwk) periods. During suckling period, daily milk yield was estimated by using the double oxytocin injections method 4-h after milking. During milking period, ewes were hand-milked once daily. Udder and teat morphology traits for all ewes were measured 4-h after milking. Udder compartments were evaluated 8-h after milking by using atosiban and oxytocin; milk samples of each fraction were collected. Najdi ewes had a medium and healthy udders (CMT<1), with medium sized teats (length, 3.2±0.1 cm and width, 1.7±0.1 cm) attached at 35.7 ± 11º angle. Milk yield averaged 1.88±0.18 and 0.44±0.12 L d-1 during suckling and milking periods, respectively. A drop in milk yield (-75%, p<0.01) was found in the transition from suckling to milking. Udder traits, teats angle and width, and distance between teats declined (p<0.05) throughout lactation, whereas teat lengths did not show any change. Positive correlations (p<0.05) were observed between milk yield and udder depth (r=0.47-0.49), width (r=0.31-0.39) and distance between teats (r=0.26-0.39). The cisternal milk volumes decreased (p<0.05) after weaning, whilst the corresponding percentages increased (p<0.05). Cisternal milk accounted for 55% and 67% of the total udder milk during suckling and milking periods, respectively. Cisternal milk was positively correlated (r=0.93, p<0.05) with total milk yield. The percentages of protein and total solids in alveolar and cisternal milk increased significantly (p<0.05) after weaning, whilst fat percentages in cisternal milk did not change. In conclusion, the evaluated Najdi ewes showed medium sized cisterns and teats, which considered adequate for machine milking. Udder morphology traits had positive correlations with milk yield and hence, can be utilized in breeding programs.

Changes in the composition and fatty acid profile of Najdi ewes’ milk before and after weaning

“…The increased milk protein content during lactation was in agreement with the results obtained by Gargouri et al (1993) and Ayadi et al (2014), who found that milk protein content during the suckling period was lower than in the milking period. The average milk fat percentage (4.41%) in this trial was similar to the value reported by Abd Allah et al (2011) in Chios ewes and Ayadi et al (2014) in Najdi ewes, but was lower than the values (6.2-7.4%) reported by Nudda et al (2002) in Awassi ewes and Castillo et al (2009) in Lacaune and Manchega ewes. Breed differences and diet could explain the discrepancies in fat percentages between these results and those of previous studies.…”

“…Similar reductions in the daily milk yield, ranging from 30% to 75%, have been reported in several sheep breeds (Gargouri et al, 1993;Ayadi et al, 2011Ayadi et al, , 2014.The drop in daily milk productivity after weaning could be explained by the partial disappearance of the stimulus caused by the transition from suckling to milking. According to Marnet (1997), the decrease in milk yield during weaning might be explained by the reduced emptying frequency and to a lesser degree by dam-lamb separation.…”

“…Sheep play an important role in the agribusiness economy of Saudi Arabia, where the sheep population is close to 7.2 million (Ayadi et al, 2014). Rearing sheep for milk production is generally a tradition in the Middle East, and has recently been gaining importance in the dairy sector owing to its high dry matter content and exceptional nutritive value.…”

“…They are well adapted to the extreme hot summer conditions, are used for milk production under traditional Bedouin rearing conditions, and are classified as fat-tailed, carpet-wooled, and non-seasonal breeders. Ayadi et al (2014) reported that Najdi ewes had immense potential for milk production under intensive production systems, yielding an average of 1.94 L day -1 during the first nine weeks of lactation. Alternative weaning systems that could spare larger amounts of milk for the commercial dairy industry have been sought by Najdi breeders.…”

Effect of ewes entry order into milking parlour on milkability and milk composition

“…During milking, the presence of the neuroendocrine milk ejection reflex is crucial for complete emptying of the udder because only 20% of the total milk in cows and above 40% in dairy sheep is located in cisternal compartment after a 12-hour milking interval (Pfeilsticker et al 1996;Marnet and McKusick 2001). The extraction of milk stored in the alveoli is important to obtain maximum milk yield and content of fat also in sheep (Antonic et al 2013;Ayadi et al 2014).…”