Temporary alterations to postpartum milking frequency affect whole-lactation milk production and the energy status of pasture-grazed dairy cows

Abstract

This study investigated the immediate and long-term effects of temporary alterations to postpartum milking frequency (MF) on milk production, body condition score (BCS), and indicators of energy status in pasture-grazed cows supplemented with concentrates. Multiparous Holstein-Friesian cows (n = 150) were randomly assigned to 1 of 5 groups at calving: milked twice daily (2 ×) throughout lactation (control), or milked either once daily (1 ×) or 3 times daily (3 ×) for 3 or 6 wk immediately postpartum, and then 2 × for the remainder of lactation. During wk 1 to 3 postpartum, cows milked 1 × produced 15% less milk and 17% less energy-corrected milk (ECM) than cows milked 2 ×. This immediate production loss increased to 20% less milk and 22% less ECM during wk 4 to 6 postpartum for cows that remained on 1 × milking; these animals also produced less than 1 × cows switched to 2 × milking after 3 wk. During wk 8 to 32, when all cows were milked 2 ×, those previously milked 1 × had sustained reductions in milk (-6%) and ECM (-8%) yields, which were not affected by the duration of reduced postpartum MF. In contrast, cows milked 3 × postpartum had 7% greater milk yields during wk 1 to 6 compared with 2 × controls, irrespective of the duration of increased MF. Milk yields also remained numerically greater (+5%) during wk 8 to 32 in cows previously milked 3 ×. Nevertheless, yields of ECM were not increased by 3 × milking, because of lower milk fat and protein contents that persisted for the rest of lactation. In addition, indicators of cow energy status reflected an increasing state of negative energy balance with increasing MF. Cows milked 1 × postpartum had greater plasma glucose and lower plasma nonesterified fatty acid concentrations during the reduced MF, and plasma glucose remained lower for 2 wk after cows had switched to 2 × milking. Moreover, BCS was improved relative to 2 × controls from wk 5 to 6. In contrast, cows milked 3 × had lower plasma glucose concentrations, greater plasma nonesterified fatty acid concentrations, and greater BCS loss during wk 1 to 3; however, greater body fat mobilization was not sustained, indicating that additional energy supplements may be required to achieve better milk production responses. In conclusion, temporary 1 × milking had lactation-long negative effects on milk and milk component yields but improved cow energy status and BCS, whereas temporary 3 × milking immediately increased milk yield but did not improve milk fat and protein yields in pasture-grazed cows.

Milking traits affected by milking frequency during first month of lactation

“…Eslamizad et al (2010) found the milk yield and fat corrected milk yield to be higher for six times a day milkings compared to three times a day (36.82, 37.32 versus 34.56, 35.33 kg/d). Phyn et al (2014) found that different milking frequencies in early lactation affected milk yield but not milk fat or protein content. Also in the study by McNamara et al (2008), milking frequency had no influence on the milk fat and protein content.…”

Once-daily milking during late lactation in pasture-fed dairy cows has minor effects on feed intake, body condition score gain, and hepatic gene expression

“…We have also previously reported that short periods of 1× milking during early lactation had short-term positive carry-over effects on metabolic status once cows were switched to 2× milking as plasma glucose and insulin concentrations remained greater and NEFA concentrations remained lower (Phyn et al, 2014). However, only one published study has measured carryover effects of 1× milking in late lactation (Ferris et al, 2008).…”

“…We have previously reported improvements in the metabolic status of grazing cows when milked 1× either immediately postcalving or during a period of feed restriction in early lactation Phyn et al, 2014). Plasma concentrations of glucose and insulin were greater, and nonesterified fatty acids (NEFA) were reduced, in cows milked 1× compared with those milked 2× Phyn et al, 2014), indicating a more positive energy balance.…”

“…We have previously reported improvements in the metabolic status of grazing cows when milked 1× either immediately postcalving or during a period of feed restriction in early lactation Phyn et al, 2014). Plasma concentrations of glucose and insulin were greater, and nonesterified fatty acids (NEFA) were reduced, in cows milked 1× compared with those milked 2× Phyn et al, 2014), indicating a more positive energy balance. Additionally, hepatic expression of genes involved in gluconeogenesis (glucose-6-phosphatase catalytic subunit, G6PC; phosphoenolpyruvate carboxykinase 1, PCK1), fatty acid β-oxidation (carnitine palmitoyltransferase 1A, CPT1A; carnitine palmitoyltransferase 2, CPT2), and ketogenesis (3-hydroxy-3-methylglutaryl-CoA synthase 2, HMGCS2), were lower in cows milked 1×, supporting the positive metabolic effects reported (Grala et al, 2014a).…”

Production response in dairy cows milked two or three times a day: A meta-analysis

“…Three of the articles used in the meta-analysis were pen studies, and two used Jersey cows and reported two different trials ( Table 1). Only a single study used lactating dairy cows on pasture 30 . The average trial duration was 220±102 milking days.…”