Impact of nutrient restriction at dry-off on performance and metabolism

Thanks to improvements in genetics, nutrition, and management, modern dairy cows can still produce large amounts of milk at the end of lactation, with possible negative effects on health and welfare, particularly when milking is stopped abruptly. To limit yield at dry-off, strategies involving different types of dietary restriction have been used worldwide. Thus, we aimed to investigate the effects of a reduced nutrient density at dry-off on milk production, metabolism, the pattern of rumen fermentation, and milk fatty acid profile around dry-off and in the ensuing periparturient period. During the last week before dry-off, 26 Holstein cows were enrolled in pairs according to the expected calving date and either fed ad libitum ryegrass hay (nutrient restricted, NR; 13 cows) or continued to receive lactation diet (control group, CTR, 13 cows). After dry-off, both groups received only grass hay for 7 d, and free access to water was always provided. Blood, milk, and rumen fluid samples were collected from 7 d before dry-off to 28 d in milk. Milk production, DMI (during the periparturient period), and rumination times were recorded daily. At dry-off, compared with CTR, NR decreased milk yield (- 62%) and milk lactose but had higher fat and protein contents. In the subsequent lactation, no significant differences were observed in milk yield and composition. The BCS did not differ between groups during the transition period, but it decreased in NR after dry-off. Before dry-off, NR had decreased glucose, urea, and insulin, but higher creatinine, β-hydroxybutyrate, and nonesterified fatty acids (NEFA). The day after dry-off, NEFA were lower in NR, but they were higher 7 d after calving. At dry-off, NR had higher rumen pH, lower lactate, urea, and total volatile fatty acid concentrations. Considering volatile fatty acid molar proportions, NR had increased acetate but decreased propionate and butyrate at dry-off. Rumination time dropped 6 d before dry-off in NR and after dry-off in CTR, but no differences were observed in the periparturient period. Milk fatty acid profile revealed a remarkably lower proportion of short-chain fatty acids in NR at dry-off and a higher proportion of medium- and long-chain ones. These results confirmed that decreasing nutrient density reduce milk yield before dry-off. However, metabolism around dry-off was significantly impacted, as suggested by plasma, rumen fluid, and milk analyses. Further research is required to investigate the impact of the metabolic effects on the inflammatory response, liver function, and immune system, particularly concerning the mammary gland.

Effect of temporary cessation of milking on the innate immune components in goat milk

Temporary cessation of milking is widely used during the dry period of dairy cows. Temporary cessation of milking induces an increase in the somatic cell count (SCC) and level of several inflammatory components of milk, which is believed to be a local adaptation and defense mechanism of the mammary gland. In Japan, temporary cessation of milking combined with antibiotic administration is widely used to treat mastitis. The present study aimed to elucidate the role of the innate immune system during temporary cessation of milking in a goat model by investigating the concentration of several innate immune components in milk during and around the temporary cessation. In experiment 1, 6 goats were subjected to cessation of milking for 3 d in both udder halves, whereas in experiment 2, 6 other goats were subjected to cessation of milking for 3 d only in 1 udder half. In experiment 1, the milk yield was lower on d 5 and 6, whereas the mean SCC was higher on d 5 compared with d 0 before temporary milking cessation. The concentrations of goat DEFB1, S100A7, cathelicidin-2 and 7 (CATHL-2 and 7), IgA, and lactoferrin were increased after temporary cessation of milking. In experiment 2, the milk yield was lower between d 5 and 7, whereas the mean SCC was higher between d 4 and 7 compared with d 0. The concentrations of CATHL-2, IgA, and lactoferrin were increased after temporary cessation of milking only in the udder half subjected to milking cessation. These results suggest that temporary cessation of milking increase the SCC and concentration of several innate immune components in milk without infection, which may contribute to mastitis treatment.