Impacts of stocking density on development and puberty attainment of replacement beef heifers

Abstract

In all, 60 Angus×Hereford heifers were ranked by age and BW (210±2 days and 220±2 kg) on day 0, and assigned to: (a) one of three drylot pens (10×14 m pens; 10 heifers/pen) resulting in a stocking density of 14 m2/heifer (HIDENS; n=3), or (b) one of three pastures (25 ha pastures; 10 heifers/pasture), resulting in a stocking density of 25 000 m2/heifer (LOWDENS; n=3). Pastures were harvested for hay before the beginning of this experiment, and negligible forage was available for grazing to LOWDENS heifers during the experiment (days 0 to 182). All heifers received the same limited-fed diet, which averaged (dry matter basis) 4.0 kg/heifer daily of hay and 3.0 kg/heifer daily of a corn-based concentrate. Heifer shrunk BW was recorded after 16 h of feed and water withdrawal on days -3 and 183 for BW gain calculation. On day 0, heifers were fitted with a pedometer behind their right shoulder. Each week, pedometer results were recorded and blood samples were collected for puberty evaluation via plasma progesterone. Plasma samples collected on days 0, 28, 56, 84, 112, 140, 161 and 182 were also analyzed for cortisol concentrations. On days 0, 49, 98, 147 and 182, hair samples were collected from the tail switch for analysis of hair cortisol concentrations. On days 28, 102 and 175, blood samples were collected for whole blood RNA isolation and analysis of heat shock protein (HSP) 70 and HSP72 mRNA expression. Heifers from LOWDENS had more (P<0.01) steps/week compared with HIDENS. No treatment effects were detected (P=0.82) for heifer BW gain. Plasma cortisol concentrations were greater (P⩽0.05) in LOWDENS compared with HIDENS heifers on days 84, 140, 161 and 182 (treatment×day interaction; P<0.01). Hair cortisol concentrations were greater (P<0.01) in HIDENS compared with LOWDENS heifers beginning on day 98 (treatment×day interaction; P<0.01). Heifers from LOWDENS had greater (P=0.04) mean mRNA expression of HSP72, and tended (P=0.09) to have greater mean mRNA expression of HSP70 compared with HIDENS. Heifers from HIDENS experienced delayed puberty attainment and had less (P<0.01) proportion of pubertal heifers on day 182 compared with LOWDENS (treatment×day interaction; P<0.01). In summary, HIDENS altered heifer stress-related and physiological responses, and delayed puberty attainment compared with LOWDENS.

Impacts of estrus expression and intensity during a timed-AI protocol on variables associated with fertility and pregnancy success in Bos indicus-influenced beef cows1

“…Estrus intensity has been quantified in dairy cattle by physical activity using pedometers, with their activity during diestrus serving as baseline (Madureira et al, 2015a;Silper et al, 2015). In view of that, cows utilized in this experiment were classified by net physical activity during the proestrus + estrus period with pedometers (Schubach et al, 2017), which accounted for individual basal physical activity when cows were inserted with a CIDR (Lamb et al, 2001). Accordingly, net physical activity was greater (P < 0.01) in HIESTR and LWESTR vs. NOESTR cows (Table 2), corroborating with the increased physical activity triggered by estrus behavior (Kiddy, 1977).…”

“…All cows were inseminated by the same technician, using semen from the same bull and batch. At the time of PGF 2α on d −4, cows were fitted with a pedometer (HJ-321; Omron Healthcare, Inc., Bannockburn, IL) placed inside a polyester patch (Heat Watch II; Cow Chips, LLC, Manalapan, NJ) fixed behind their left shoulder to assess physical activity (Haley et al, 2005;Knight et al, 2015;Schubach et al, 2017). Pedometers had the capability to store daily data for seven consecutive days.…”

“…However, research is warranted to further understand fertility and pregnancy establishment parameters associated with estrus and to characterize the impacts of estrus intensity on reproductive function of beef females. One alternative for the latter is the use of pedometers to estimate cow physical activity (Schubach et al, 2017), which has been used as measurement for estrus intensity in dairy cattle (Silper et al, 2015). Therefore, we hypothesized that estrus expression and intensity will be positively associated with fertility variables and pregnancy rates in beef cows.…”

“…Expression of genes associated with pregnancy establishment in whole blood, serum concentrations of bovine pregnancy-associated glycoproteins (bPAGs), and pregnancy rates of Nelore × Angus beef cows according to estrus expression and intensity 1,2,3 Cows were assigned to an estrus synchronization + timed-AI protocol (Meneghetti et al, 2009) from d −11 to 0. Cows were fitted with a pedometer (HJ-321; Omron Healthcare, Inc., Bannockburn, IL) behind their left shoulder on d −4 (Schubach et al, 2017). An estrus detection patch (Estrotect; Rockway Inc., Spring Valley, WI) was attached to the tail-head of each cow on d −2.…”

Welfare assessment in dairy cows using hair cortisol as a part of monitoring protocols

“…No effect of stocking density (20% difference between groups) on hair cortisol of Jersey cows in the prepartum period was detected at calving in a study by Silva et al (2016), possibly because the high stocking density may not have been dramatic enough. In the study on beef heifers, higher cortisol concentrations were detected from the hair of animals kept in dry-lot pens with a stocking density 14 m 2 / heifer compared to animals kept on pastures with a stocking density 2.5 ha/heifer on day 98 after allocation (Schubach et al, 2017), showing stocking density can influence hair cortisol concentration. Some studies detected a negative relationship between milk yield and hair cortisol levels (Burnett et al, 2015;Talló-Parra et al, 2018).…”