1- Agricultural Research,Education and Extension Organization
Abstract: (9 Views)
Background: Lambs raised under nomadic systems, which primarily rely on grazing in natural pastures, may undergo delayed puberty due to inadequate nutrition. Furthermore, poor nutritional management and lack of supplementary feeding can lead to missed breeding opportunities in ewe lambs. This may result in a delay in the age at first lambing, thereby causing the loss of an entire productive year of breeding ewes. Therefore, finding an appropriate strategy to address this issue can contribute to improved production and reproduction in nomadic herds. In addition to the positive effects of nutrition on fertility rates, estrus synchronization using hormones plays an effective role in enhancing ewe fertility. Synchronizing estrus ensures the birth of age-matched lambs in a condensed timeframe, streamlining their management throughout different rearing stages. In the nomadic rearing system of Moghani sheep, the first mating that leads to pregnancy in young female lambs is not possible before 18 months of age due to their poor body condition and low weight. Hence, the present study aimed to investigate the effects of supplementary feeding of Moghani lambs and pre-scheduled estrus synchronization, compared to nomadic conditions, on productive and reproductive traits.
Methods: Prior to the main project and to produce age-matched lambs, estrus synchronization was performed on a nomadic herd of 190 ewes using progesterone-impregnated sponges and hormone therapy with 400 IU of pregnant mare serum gonadotropin. Mating of synchronized ewes was conducted naturally using appropriate rams. After lambing and the random selection of female lambs, , the main study was conducted in three phases. In the first phase, 80 Moghani lambs were divided into two groups including 40 lambs. One group was fed on mother’s milk and pasture only, while the other group received, in addition to milk and pasture, a concentrate diet containing 17.5% protein and 2.65 Mcal of energy. The first phase lasted from birth to the completion of the lambs’ third month. During the second phase, from four to nine months of age, the protein and energy levels in the second group’s diet were reduced to 15% and 2.5 Mcal, respectively. At the end of the second phase, 50% of each group underwent estrus synchronization. Natural mating was performed in all groups using rams. The weights of treated lambs were recorded monthly. Following lambing of the ewes under study, parameters including lambing rate, twinning rate, lamb mortality, lambing percentage, birth weight, and weaning weight were measured. Additionally, the average daily milk production of the ewes during two lactation periods was recorded. Monthly weight means were compared using t-tests. Statistical analysis of discrete traits (lambing rate, twinning rate, lamb mortality, lambing percentage) and continuous traits (birth weight, weaning weight, and ewe milk production at first and second lactation) was performed using the GENMOD and GLM procedures in SAS software, respectively.
Results: According to the results obtained, the average weight of lambs supplemented with concentrate was significantly higher than that of the group fed by mother’s milk and grazing in pasture (P < 0.05). Both the feeding method and the application or absence of estrus synchronization had a significant effect on lambing rate and lambing percentage (P < 0.05). Specifically, 65% of ewe lambs receiving concentrate gave birth, compared to only 20% in the control group. Estrus synchronization also significantly increased the lambing rate within these groups (P < 0.05). Feeding methods and synchronization did not have a significant impact on twinning rate and lamb mortality rate. Moreover, birth weight and weaning weight of lambs born to mothers receiving concentrate were significantly higher than those born to mothers grazing on pasture only (P < 0.05). Additionally, ewes supplemented with concentrate produced significantly more milk during both the first and second lactation compared to the other group (P < 0.05). Estrus synchronization had a significant effect only on milk production at the first lactation, with no significant impact on other traits. The interaction between feeding and synchronization has no significant effects on any of the studied traits.
Conclusion: The results of the present study suggest that supplementary feeding under pastoral grazing conditions can improve both productive and reproductive traits in lambs. Supplementary feeding combined with estrus synchronization can significantly increase the chances of breeding and lambing at younger ages in ewe lambs. Prepubertal supplementary feeding not only enhances physical condition and accelerates puberty onset, but also results in lambs with higher weights at weaning. Furthermore, improved body growth and better mammary development in these lambs can enhance future milk production efficiency. The positive effects of supplementary feeding and estrus synchronization in ewe lambs born under nomadic systems could contribute to improved overall farm productivity
Methods: Prior to the main project and to produce age-matched lambs, estrus synchronization was performed on a nomadic herd of 190 ewes using progesterone-impregnated sponges and hormone therapy with 400 IU of pregnant mare serum gonadotropin. Mating of synchronized ewes was conducted naturally using appropriate rams. After lambing and the random selection of female lambs, , the main study was conducted in three phases. In the first phase, 80 Moghani lambs were divided into two groups including 40 lambs. One group was fed on mother’s milk and pasture only, while the other group received, in addition to milk and pasture, a concentrate diet containing 17.5% protein and 2.65 Mcal of energy. The first phase lasted from birth to the completion of the lambs’ third month. During the second phase, from four to nine months of age, the protein and energy levels in the second group’s diet were reduced to 15% and 2.5 Mcal, respectively. At the end of the second phase, 50% of each group underwent estrus synchronization. Natural mating was performed in all groups using rams. The weights of treated lambs were recorded monthly. Following lambing of the ewes under study, parameters including lambing rate, twinning rate, lamb mortality, lambing percentage, birth weight, and weaning weight were measured. Additionally, the average daily milk production of the ewes during two lactation periods was recorded. Monthly weight means were compared using t-tests. Statistical analysis of discrete traits (lambing rate, twinning rate, lamb mortality, lambing percentage) and continuous traits (birth weight, weaning weight, and ewe milk production at first and second lactation) was performed using the GENMOD and GLM procedures in SAS software, respectively.
Results: According to the results obtained, the average weight of lambs supplemented with concentrate was significantly higher than that of the group fed by mother’s milk and grazing in pasture (P < 0.05). Both the feeding method and the application or absence of estrus synchronization had a significant effect on lambing rate and lambing percentage (P < 0.05). Specifically, 65% of ewe lambs receiving concentrate gave birth, compared to only 20% in the control group. Estrus synchronization also significantly increased the lambing rate within these groups (P < 0.05). Feeding methods and synchronization did not have a significant impact on twinning rate and lamb mortality rate. Moreover, birth weight and weaning weight of lambs born to mothers receiving concentrate were significantly higher than those born to mothers grazing on pasture only (P < 0.05). Additionally, ewes supplemented with concentrate produced significantly more milk during both the first and second lactation compared to the other group (P < 0.05). Estrus synchronization had a significant effect only on milk production at the first lactation, with no significant impact on other traits. The interaction between feeding and synchronization has no significant effects on any of the studied traits.
Conclusion: The results of the present study suggest that supplementary feeding under pastoral grazing conditions can improve both productive and reproductive traits in lambs. Supplementary feeding combined with estrus synchronization can significantly increase the chances of breeding and lambing at younger ages in ewe lambs. Prepubertal supplementary feeding not only enhances physical condition and accelerates puberty onset, but also results in lambs with higher weights at weaning. Furthermore, improved body growth and better mammary development in these lambs can enhance future milk production efficiency. The positive effects of supplementary feeding and estrus synchronization in ewe lambs born under nomadic systems could contribute to improved overall farm productivity
Type of Study: Research |
Subject:
مدیریت دامپروری و تولید
Received: 2025/04/29 | Accepted: 2025/08/18
Received: 2025/04/29 | Accepted: 2025/08/18
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