Feeding linseed to dairy cows results in milk fat depression (MFD), but there is a wide range of sensitivity among cows. The objectives of this study were to identify target genes containing SNP that may play a key role in the regulation of milk fat synthesis in cows resistant or sensitive to MFD. Four cows were selected from a dairy farm after a switch from a control diet to a linseed-rich diet; two were resistant to MFD with a high milk fat content in the control (4.06%) and linseed-rich (3.90%) diets; and two were sensitive to MFD with the milk fat content decreasing after the change from the control (3.87%) to linseed-rich (2.52%) diets. Transcriptome and SNP discovery analyses were performed using RNA-sequencing technology. There was a large number of differentially expressed genes in the control (n = 1316) and linseed-rich (n = 1888) diets. Of these, 15 genes were detected as key gene regulators and harboring SNP in the linseed-rich diet. The selected genes MTOR, PDPK1, EREG, NOTCH1, ZNF217 and TGFB3 may form a network with a principal axis PI3K/Akt/MTOR/SREBP1 involved in milk fat synthesis and in the response to diets that induced MFD. These 15 genes are novel candidate genes to be involved in the resistance or sensitivity of dairy cows to milk fat depression.
Essential oils may affect rumen fermentation, nutrient digestion, and milk production and composition. The objective of this study was to test the effects of capsicum oleoresin (CAP) and propyl-propane thiosulfonate (PTSO) on rumen fermentation, total tract digestibility, and milk yield and composition in lactating dairy cattle. Six lactating Holstein cows (averaging (mean ± SD) 130 ± 40 days in milk and 723 ± 55 kg of body weight) fitted with rumen cannulae were used in a duplicated 3 × 3 Latin square design. Treatments were: a control diet (CTR), the CTR diet with the addition of 500 mg/d/cow of CAP, and the CTR diet with the addition of 250 mg/d/cow of PTSO. Dry matter intake (DMI) averaged 20.7 kg/d with a tendency towards higher intake in cows fed CAP and lower in those fed PTSO (p = 0.08). Milk yield averaged 31.8 kg/d with no difference among treatments. However, feed efficiency was higher in PTSO supplemented cows compared with CTR (1.65 and 1.41 kg of milk yield/kg of DMI, respectively; p < 0.01). At the doses used in this experiment, CAP and PTSO failed to demonstrate any effects on rumen fermentation, but PTSO increased the efficiency of feed utilization to produce milk.
Three loose housing systems for lactating cows (compost bedded pack, CBP; conventional bedded pack, BP; and freestalls, FS) were assessed on one farm in terms of cow behavior and welfare. An on-farm welfare assessment based on the Welfare Quality protocols was used four times every three months on 757 cows. Video recordings taken twice over four days were used to assess behavior patterns at resting areas. Cows in CBP and BP were dirtier than those in FS (p < 0.0001). Fewer integument alterations were recorded for CBP and BP than FS (p < 0.001). Cows in BP were quicker to lie down and stand up compared to those in CBP or FS (p < 0.001). Percentages of cows needing more attempts before rising were higher for FS (p < 0.01). However, a higher frequency of kneeling was observed in CBP (p = 0.033). A lower percentage of cows lying in the resting area was recorded for FS (56%) than CBP or BP (97 or 84%, respectively, p < 0.05). Overall, in this study, cows kept in bedded pack barns were dirtier but had fewer integument alterations and spent more time lying down in the resting area than cows housed in freestalls.
