Short communication: Repeated mammary tissue collections during lactation do not alter subsequent milk yield or composition

Abstract

Mammary biopsy collection (MB) is a valuable approach for studying mammary gland biology, but it is unclear if repeated MB impair the performance of lactating dairy cows. The objective of this trial was to examine the effect of repeated MB during lactation on udder health, dry matter intake (DMI), and lactation performance of lactating dairy cows. Sixty-four multiparous, mid-lactation Holstein cows were enrolled in a 29-wk trial, and 32 cows were randomly selected for repeated MB. The MB and non-MB (NMB) cows had similar parity (2.6 ± 0.9) and days in milk (96.5 ± 56.3 d) at enrollment. All animals were housed in the same barn and managed in the same manner. Cows were milked 3 times daily with milk yield recorded at each milking. Milk composition was measured weekly and DMI recorded daily. Three MB were performed per cow: 1 wk after enrollment and at 15 and 24 wk. The first and third MB were performed on the left rear quarter, whereas the second MB was on the right rear quarter. The MB were performed based on previously described procedures using a rotating stainless steel cannula with a retractable blade connected to a cordless drill, with appropriate sedation and antiseptic treatment after each MB. After MB, udder health, surgical wound healing, and presence of blood in milk were visually examined at each milking. Blood was cleared from milk 3.86 ± 2.0 d after MB. During the experiment, 4 rear quarters of MB cows and 5 rear quarters from NMB cows were diagnosed and treated for clinical mastitis. No differences were observed in DMI, milk yield, somatic cell score, or milk concentration and yields of fat, protein, lactose, and solids-not-fat between MB and NMB. In conclusion, lactating cows recover rapidly from MB, and repeated MB have no long-term effects on DMI, milk yield and composition, or udder health of lactating dairy cows.

Short communication: Effects of mammary biopsy in the dry period on activity and feeding behavior of dairy cows

“…We found no effect of the mammary biopsy during the dry period on milk yield during the first 9 wk after calving (38.0 vs. 40.6 kg/d; SE = 3.4; P = 0.59). This is consistent with previous findings that mammary biopsies did not affect milk yield or composition in lactating cows (Weng et al, 2017).…”

“…In the present study, cows were in heat stress conditions when pen temperature-humidity index was 77.6 (as described in greater detail by Fabris et al, 2017), although all enrolled cows received active cooling. Consistent with previous findings (Weng et al, 2017), we found no significant effect of mammary biopsy on DMI. Similarly, Mølgaard et al (2012) found no effect of liver biopsy on feed intake.…”

“…Collection of more behavioral data in future work may provide further insight into the effects of mammary biopsy on feeding motivation. Our observed absence of effects on total feeding time or feed intake, in combination with previous findings (Mølgaard et al, 2012;Weng et al, 2017), suggests that cows prioritize maintaining feed intake, such that it may be a less useful indicator of pain, but that feeding patterns may be more sensitive to emotional or inflammatory effects of painful procedures. Feeding time and feed intake are affected by lameness (Norring et al, 2014), likely because accessing the feedbunk causes specific pain due to standing on affected limbs.…”

“…In dairy cattle, mammary biopsies are commonly used to study mammary development and function (Weng et al, 2017;Skibiel et al, 2018). It is common practice to apply analgesic and local anesthetic for this procedure, yet post-biopsy inflammation may also cause pain.…”

“…Mammary biopsies have previously been found to have no effect on DMI or milk yield, suggesting that this procedure may not affect production (Weng et al, 2017). Previous studies suggest that behavioral changes follow liver biopsy procedures in dairy cattle (Beausoleil and Stafford, 2012;Mølgaard et al, 2012), but effects of mammary biopsy on similar behavioral changes, which may be indicative of ongoing pain, have not been evaluated.…”