Factors affecting milk yield and composition of Tunisian camels (Camelus dromedarius) over complete lactation

Lactation traits and reproductive performances of Sahraoui female camel in two breeding systems at Algerian Sahara

The main objective of this study is to determine the impact of the camel livestock system on individual and herd performances of milk production, lactation curve, fats, and protein concentrations. For this purpose, 13 she-camels of Sahraoui breed from the south eastern Algeria and belonging and semi-intensive system (N = 6) and intensive system (N = 7) were studied. Recording and sampling of milk were carried out at regular intervals during a full lactation. The lactation curve was estimated using Wood's gamma function and the t-test of independent groups was carried out to compare lactation performances, lactation curve, and reproductive parameters. The overall average daily milk (DMY), fat (DFY), and protein (DPY) yield were 6.77 ± 0.82 kg/day, 4.15 ± 0.91%, and 4.49 ± 0.20%, respectively. The mean of total milk yield (TMY) was 2696.39 ± 343.86 kg during a mean lactation length (LL) of 398.38 ± 20.65 days. The peak of milk production (6.79 ± 0.68 kg) was reached at 93.9 ± 55.8 days after calving. The open day (DO) and inter-calving interval (ICI) recorded in this study were 348.38 ± 30.33 and 723.38 ± 30.33 days, respectively. There is no significant difference (p > 0.05) between intensive and semi-intensive breeding systems for TMY (2795.39 ± 261.88 kg vs. 2580.89 ± 414.43 kg), DMY (6.96 ± 0.66 kg vs. 6.55 ± 1.00 kg), and LL (402.14 ± 21.18 days vs. 394 ± 21.03 days). However, the total amount of fat was significantly higher in intensive system (182.02 ± 33.91 kg) and the DPY content was significantly higher in semi-intensive system (4.60 ± 0.13%). The parameters α, β, and γ of lactation, fat, and protein curves between the two systems showed a highly significant difference (p < 0.01) for the parameters (α and β) for the milk production curve, significant (p < 0.05) for the time to reach peak yield, and no significance for the other parameters. The corresponding values of the coefficient of determination (R2) were 0.62, 0.35 for milk yield (p > 0.05), 0.12, 0.13 (p > 0.05) for fat, and 0.03, 0.11 (p < 0.05) for protein, in the intensive and semi-intensive systems, respectively. In addition, DO and ICI were not significantly different between the livestock systems, but were higher in the intensive system than the semi-intensive system (337.17 ± 26.26 vs. 712.17 ± 26.26, respectively). The study concluded that the intensive system had a higher milk performance with a more efficient lactation curve. The incomplete gamma model (Wood) used in this study was inappropriate for estimating milk yield, but acceptable for fat and protein.

DNA polymorphisms of FGFBP1, leptin, κ-casein, and αs1-casein genes and their association with reproductive performance in dromedary she-camels

In livestock, selection programs on reproductive traits are time consuming due to long generation interval and low heritability; however understanding the genetic factors that influence reproductive performance facilitates an accurate selection and genetic improvement of these quantitative traits. Therefore, the aim of this study was to identify the effect of lactation order and polymorphisms of FGFBP1, leptin, κ-casein, and αs1-casein genes on reproductive performance in dromedary she-camels. Blood samples were collected from one hundred she-camels using vacutainer tube containing EDTA as an anticoagulant for DNA extraction. PCR-DNA sequencing approach was performed to investigate the polymorphisms in fragments for coding sequence (CDS) parts of FGFBP1 (539-bp) and leptin (359-bp), 5'-flanking region of κ-casein (488-bp) and intervening non-coding fragment spanning from exon 4 to exon 6 (924-bp) of αs1-casein genes. Results revealed that there were single nucleotide polymorphisms (SNPs) in the investigated genes between enrolled she-camels except for leptin gene that elicited a monomorphic pattern. The identified SNPs allocated camels into different groups according to which animal harbored the explored SNPs. Multiple linear regression analysis (MLR) reveled that identified SNPs and parity order had significant effects on age at first calving (AFC), days open (DO), calving interval (CI), number of services/conception (NS/C) and milk yield traits. Determination coefficients (R²) value indicated also that variability in the phenotypic measurements of studied traits might be correlated with the identified SNPs in the reproduction related genes. This study highlights that parity order has a remarkable effect on reproductive performance. Single nucleotide polymorphisms in the investigated genes could be also used as proxy predictors and genetic markers that permit a marker assisted selection for reproductive performance traits in dromedary she-camels.

Transcriptional profiling of buffalo mammary gland with different milk fat contents

Milk fat is the most important energy substance in milk and contributes to its quality and health benefits. Water buffalo milk is well known for its high milk quality with higher fat contents compared with cattle milk. Dehong buffalo is a unique local swamp breed in Yunnan Province with higher milk fat and excellent milk quality which provides a good model for the investigation of the molecular mechanisms of milk fat deposition. In this study, we used RNA-seq to obtain mammary tissue transcriptomics of buffalo with different milk fat phenotypes including high(H), medium (M)and low (L) fat content groups. Comparative analyses of buffalo among three groups yielded differentially expressed genes (DEGs). Analyzing the number of different genes among H_VS_L, H_VS_M, and M_VS_L showed the same expression pattern between H_VS_M. The increasing expression levels of genes including CSN1S1, BTN1A1, LALBA, ALDH1L2, SCD and MUC15, and down-regulated expression levels of genes containing CCL2, CRABP2, ADTRP, CLU and C4A in H_VS_L and M_VS_L were found. GO and KEGG enriched pathways revealed these DEGs involved in milk protein and fat as well as immune response. The findings would enhance the understanding of the interplay between the milk composition and immune response, which suggests that the immune capacity should be considered when we tried to improve the milk quality.