Body Composition Changes in Response to Skeletal Muscle Phenotype and Fat Supplementation in Lactating Dairy Cattle
Creators: name: Hanno, Samantha L
Publisher: name: Purdue University Graduate School
Year: 2024
Subjects: classificationCode: 300302
subject: Animal management

description: The production cycle of lactating dairy cattle consists of physiological adaptations and changes in body tissue reserves as energy and protein requirements shift and may not be able to be met by feed intake. Tissue reserves are mobilized in early lactation and accreted thereafter, which can be used as a pool of labile amino acids and energetic substrates used at the beginning of the subsequent lactation. Nutritional strategies can be employed to mitigate extensive tissue loss and gain as a management tool to enhance dairy performance. The first study's objective was to evaluate the effects of high oleic soybean oil (HOSO) supplementation on milk production, body composition, and apparent total tract digestibility variables. A cross-over design with 21-d periods was employed with thirty Holstein cows (n = 16 primiparous, n = 14 multiparous at 87 ± 26 DIM at start of trial). Treatments consisted of a control (CON) with no added soybean oil and a HOSO diet with 1.5% diet dry matter (DM) of high oleic soybean oil added. Milk production and DM were collected on the last 7 d of each period. Body weights (BW), milk, and fecal samples were collected on the last 3 d of each period. Ultrasound scans of the <i>longissimus dorsi </i>muscle and body condition scores (BCS) were collected on the last d of each period. Dry matter intake, milk production, and milk component yields were not impacted by HOSO supplementation, although milk fat concentration tended to be greater for HOSO cows. A treatment by parity interaction and treatment by parity tendency were observed for BCS and BW, respectively, with multiparous HOSO cows having increased BCS and BW compared to CON with no effect on primiparous cows. Compared with CON, HOSO increased backfat depth (BFD) by 0.44 mm as well as apparent total tract fat digestibility by 12 percentage units with no differences observed in muscle<i> </i>depth. The second study’s objective was to evaluate changes in <i>longissimus dorsi </i>depth and its impact on production parameters in cows with two muscle phenotypes. Forty multiparous dairy cows were categorized into two muscle phenotype groups of high muscle (HM; n = 18) and low muscle (LM; n = 22) as determined by <i>longissimus dorsi </i>depth immediately after parturition. Ultrasound images of the <i>longissimus dorsi </i>and body weights were collected monthly from 0 to 300 DIM. Blood samples were collected from the coccygeal vessels on d 7, 150, and 300 and analyzed for 3-methylhistidine (3-MH), creatinine, non-esterified fatty acids (NEFA), and insulin. Milk weight data was collected daily using AfiFarm and milk components were collected from monthly DHIA test day data. Neither BW nor BFD were different between HM and LM cows at any timepoint, although, a DIM effect was observed. Cows lost BW from 0 to 60 DIM and BFD from 0 to 90 DIM and began increasing thereafter until 300 DIM. A muscle group by DIM interaction was observed where HM cows had more <i>longissimus dorsi </i>depth (LDD) at 0 and 300 DIM and tended to have more at 60 DIM compared to LM cows, with no differences at any other timepoint. In both muscle groups, LDD was decreased from 0 to 60 DIM but substantial LDD accretion did not occur until 240 DIM. No differences were observed between muscle groups for blood analytes; however, significant DIM effects were observed and corresponded to the observed changes in body tissue reserves. Daily milk production was grouped by stage of lactation with DIM groups consisting of early lactation from 0 to 60 DIM, mid-lactation from 60-240 DIM, and late lactation from 240 to 300 DIM. There was a muscle group by DIM group interaction for daily milk yield as HM cows produced more milk/d in early and mid-lactation but produced less milk in late lactation compared to LM cows. The results of these studies indicate that oleic acid can be supplemented to lactating dairy cattle to increase adipose tissue reserves with no effect on muscle reserves. This could potentially be caused by the lack of muscle accretion throughout mid-lactation whereas adipose tissue is gained. These results also describe that nutrition and muscle phenotype play a role in body composition throughout lactation.