Milk production and anatomical udder capacity changes of udder halves subjected to increased milking frequency at two stages of lactation.

This study aimed to characterize the effects of increased milking frequency (IMF) at early and mid-lactation on milk yield and its association with changes in cistern and alveolar capacity. Fourteen multiparous Holstein cows were subjected to IMF using the unilateral frequent milking method from 3 to 24 d in milk (DIM). At mid-lactation, cows were randomly assigned to 1 of 2 treatments: control or repeated. From 150 to 170 DIM, IMF treatment was reimposed in the repeated group. During IMF, left udder halves were milked 2× and right udder halves were milked 4× daily. To separate individual milk yields of udder halves, separate buckets were used to collect samples from each udder half. Milk samples and milk yield from right and left udder halves were collected on d 150, 170, 200, 230, 260, and 290 of lactation. Alveolar and cistern capacity were measured 26 h after the last milking at 140 and 172 DIM using an oxytocin inhibitor. Cistern and alveolar capacity were measured by evaluating the milk harvested after oxytocin inhibitor and oxytocin administration, respectively. Udder half difference yields were calculated by subtracting left half yield from right half yield. At 170 DIM, the udder half difference in repeated was 2.27 kg greater than the udder half difference in control. Udder halves milked 4× produced more milk and protein than 2× udder halves in the repeated group at 170, 200, 230, and 260 DIM. Cumulative (150 to 290 DIM) and carry over (200 to 290 DIM) udder half differences in milk yield were similar between the control and repeated treatments. Alveolar volume was similar between udder halves milked 2× or 4× at 140 DIM, while cistern volume was larger for udder halves milked 4× than 2× in early lactation. There was no difference between alveolar or cistern volume proportion in udder halves milked 2× or 4× before mid-lactation IMF. After 20 d IMF for the repeated group, alveolar volume was similar between control and repeated independent of udder half milking frequency. However, repeated held 4.9 kg more cistern milk than control. Control treatment udder halves had a greater alveolar proportion than repeated treatment udder halves. As expected, the cistern proportion was smaller in control and larger in repeated after mid-lactation IMF. IMF at early and mid-lactation enhances milk and protein yield largely during differential milking frequency regimens. The lack of enhancement in milk yield after IMF might be associated with a different response to IMF in the mammary gland at early versus mid-lactation. Based on our results, we conclude that udder halves subjected to early and mid-lactation IMF had increased cistern volume capacity.

The effects of dexamethasone administration on physiological, behavioral, and production parameters in dairy cows after a difficult calving.

Dairy cows are predisposed to diseases during the postpartum period. Dystocia has been associated with increased risk for disease, which is likely the result of increased tissue trauma and stress during the prolonged parturition. To attenuate the inflammatory response seen in dystocic animals and improve well-being, we assessed the effects of a glucocorticoid, dexamethasone administered within 12 h after calving. Dystocia was defined as a difficult birth resulting in a prolonged calving (≥70 min after the amniotic sac appears) and was monitored through 3 video cameras in the close-up dry-cow pen. Cows meeting the dystocia definition were randomly assigned to receive a single intramuscular injection of either dexamethasone (DEX; 0.1 mg/kg of body weight; n = 43) or saline (CON, n = 44) within 12 h following a dystocic calving. Serum haptoglobin, blood ß-hydroxybutyrate (BHB) concentrations, body temperature, and several behaviors were measured for the first 7 d postpartum. Additionally, milk production and components for the first 120 d were recorded. Using a mixed model, the fixed effects of treatment, parity, calving assistance, and time, along with 2- and 3-way interactions, were analyzed with cow as a random effect. We observed that primiparous DEX cows had greater serum haptoglobin concentrations on d 3 and d 7 postpartum compared with primiparous CON cows. There was no difference between treatment groups for blood BHB concentrations and body temperature. Behavior was altered between treatments, with DEX cows having reduced activity for the first week postpartum, as well as less restlessness and increased lying times on some of the days following calving. Treatment interacted with time for milk yield, such that DEX cows produced 2.7 kg/d less milk than CON cows for the first month following calving. The administration of dexamethasone resulted in changes in behavioral measurements, which could suggest a reduction in discomfort; however, due to the reduction in milk yield for the first month following calving, DEX administration may not be applicable for typical farm use. Additional research is needed to investigate treatments for cows experiencing dystocia without detrimental effects on milk yield.

Meloxicam administration either prior to or after parturition: Effects on behavior, health, and production in dairy cows.

Parturition is often a stressful period, when the incidence of disease is high after calving, which has been associated with an uncontrolled inflammatory response. Therefore, the objective of this study was to test the effect of the administration of a nonsteroidal anti-inflammatory drug (meloxicam) on the behavior, health, and production of peripartum cows. Meloxicam was dosed at 1 mg/kg of body weight, and an empty gel capsule served as a placebo. Both were administered orally with a balling gun. Dairy cows and heifers were randomly assigned to 1 of 3 treatment groups: (1) meloxicam administration before calving, with a placebo administered after calving (MEL-PRE, n = 60), (2) placebo administered before calving, and meloxicam administered after calving (MEL-POST, n = 69), and (3) a placebo administered before calving and after calving (CTL, n = 65). To identify imminent calving events, a vaginal thermometer was inserted approximately 2 wk before the expected calving date and a drop in temperature was used to identify cows close to calving. Calving events were monitored via video cameras, and the amount of time that elapsed between the appearance of the amniotic sac at the vulva until delivery of the calf was used to determine calving difficulty score. Eutocic calving events were defined as cows that calved in ≤70 min, and dystocia was defined as cows that took longer than 70 min to calve. Milk yield and components were measured for the first 15 wk of lactation and accelerometers were used to record activity and lying behaviors. The effects of treatment, breed, parity, calving difficulty, and, when applicable, a repeated measure, along with interaction terms, were analyzed in mixed models. Regardless of the time of administration, dystocic cattle that received meloxicam were less active than dystocic CTL. Dystocic animals displayed more lying bouts on the day of calving and then displayed fewer lying bouts and were less active during the days following calving. No effect of treatment was noted on any health outcomes. Eutocic MEL-PRE animals produced 6.8 kg/d more milk than eutocic CTL. Regardless of calving difficulty, MEL-PRE animals produced more milk fat, protein, and lactose (kg/d) than CTL. In conclusion, meloxicam administration before calving appears promising in increasing milk yield in eutocic cows.

Effect of early grain feeding of beef steers on postabsorptive metabolism.

The objective of this study was to determine the effect of early weaning followed by a period of high-grain feeding on plasma acetate kinetics and signaling protein phosphorylation in LM tissue of growing steers. We hypothesized that early grain feeding would result in altered cell signaling and acetate use to support observed improvements in carcass gain and marbling. Fall-born Angus × Simmental steers were weaned at 106 ± 4 d of age (early weaned [EW]; n = 6) and fed a high-grain diet for 148 d or remained with their dams (normal weaned [NW]; n = 6) on pasture until weaning at 251 ± 5 d of age. Both treatments were subsequently combined and grazed on mixed summer pasture to 394 ± 5 d of age followed by a feedlot ration until harvest at 513 ± 5 d of age. Longissimus muscle tissue biopsies were collected at 253 ± 5 and 394 ± 5 d of age and at harvest. Total and phosphorylated forms of 5' adenosine monophosphate-activated protein kinase (AMPK) and downstream proteins of the mammalian target of rapamycin signaling pathway were determined by western blotting. Eight steers were used to assess acetate clearance at different age points via a bolus infusion of acetate (4 mmol/kg of BW). Early weaned steers had greater (P < 0.05) ADG than NW steers during the early grain feeding period. Phosphorylated to total ratios of ribosomal protein S6 (rpS6) and ribosomal protein S6 kinase 1 (S6K1) were significantly different during the early grain feeding period. Phosphorylated to total ratios of S6K1, rpS6, acetyl-CoA carboxylase, and 4E binding protein 1 and the absolute amount of phosphorylated AMPK were correlated with ADG, explaining 46% of the variance. Acetate clearance rates were less (P < 0.05) and synthesis rates were greater (P = 0.06) in EW steers during early grain feeding. Acetate synthesis rates were also greater (P < 0.05) in NW steers at harvest, suggesting a permanent shift in the gut microflora or gut function in response to the treatment. Neither treatment nor acetate infusion significantly affected plasma glucose or insulin concentrations. Plasma ß-hydroxybutyric acid concentrations increased with acetate infusion (P < 0.05). Based on these results, altered cell signaling during the early grain feeding period likely mediated increased protein deposition, leading to increased carcass weights, but observed changes in acetate appearance and clearance rates do not appear to explain the observed differences in intramuscular fat deposition during the terminal feeding period.

Effect of timing of second prostaglandin F 2 alpha administration in a 5-day, progesterone-based CO-Synch protocol on AI pregnancy rates in beef cows.

The objective was to compare the timed AI pregnancy rate of Angus-cross beef cows synchronized with a 5-d CO-Synch + CIDR (a progesterone-releasing intravaginal insert) protocol and given two doses of PGF(2 alpha) (PGF), with the first dose in conjunction with CIDR withdrawal on Day 5, and the second dose given either early or late relative to the first dose. All cows (N = 1782) at 16 locations received 100 microg of GnRH + CIDR on Day 0. Cows received 25 mg of PGF concurrent with removal of the CIDR on Day 5, and were randomly allocated within locations to receive a second PGF either early (N = 881; from 0.5 to 3.9 h) or late (N = 901; from 4.5 to 8.15 h) relative to the first PGF treatment. On Day 8 (72 h after CIDR removal), all cows were inseminated and concurrently given 100 microg of GnRH. Cows were fitted with a pressure-sensitive mount detection device (Kamar) at CIDR removal. Cows were observed twice daily through Day 7 and at the time of AI on Day 8 for estrus and Kamar status (estrus - red, partial and lost Kamar versus no estrus - white Kamar) was recorded. Accounting for location, season, AI sire, cow observed in estrus or not at or before timed AI, and treatment by cows observed in estrus interaction, timed AI pregnancy rates were greater for the late (6.45 +/- 0.03 h) than the early (2.25 +/- 0.05 h) interval, 57.2 vs. 52.7%, respectively (P < 0.05). In conclusion, cows that received the second PGF late after the first PGF on the day of CIDR removal in a 5 d CO-Synch + CIDR synchronization protocol had significantly higher timed AI pregnancy rates than those receiving the second PGF early after the first PGF.