Supplemental fat for dairy calves during mild cold stress.

Eighty-one Holstein and Holstein-cross dairy calves fed calf milk replacer (CMR) were used to determine response to increasing amounts of supplemental fat during mild cold stress. Calves (n=27) were randomly assigned to 1 of 3 treatments: (1) low fat [LF; 28% crude protein:15% fat milk replacer (28:15 MR)]; (2) medium fat [MF; 28:15 MR+113 g/d of commercial fat supplement (FS)]; (3) high fat (HF; 28:15 MR+227 g/d of FS). The MF and HF calves received FS from d 2 to 21, and all calves were fed LF from d 22 to 49. The CMR was fed at 1.4% of birth body weight (BBW) from d 1 to 10, at 1.8% of BBW from d 11 to 42, and at 0.9% of BBW from d 43 to 49. Calves were weaned on d 49 and remained in hutches until d 56. The CMR was reconstituted to 13% solids. Calves were fed a commercial starter grain (19.2% crude protein on a dry matter basis) ad libitum and offered warm water after CMR feeding. Calves were fed CMR twice daily at 0630 and 1730 h in hutches bedded with straw. Starter intake, CMR intake, and ambient temperature were measured daily, and body weight (BW), hip height, and body length were measured weekly. Data were analyzed using PROC MIXED in SAS (SAS Institute Inc., Cary, NC) as a randomized design with linear and quadratic contrasts. Calf BBW averaged 42.0 ± 1.0 kg, total serum protein averaged 5.8 ± 0.1mg/dL, and birth ambient temperature averaged 5.0 ± 1.1°C. Feeding FS increased metabolizable energy intake (MEI) over maintenance but decreased efficiency of conversion of BW gain:MEI. Starter intake by LF calves was greatest until the beginning of weaning, after which starter intake was similar among treatments. Because of higher starter intake, total MEI was similar among treatments. Feed efficiency through d 49 was greater for calves fed MF and HF. Average daily gain during fat supplementation was greater for MF and HF than for LF. Lack of increase in BW gain and feed efficiency between MF and HF treatments indicated that HF did not result in advantages over MF. Supplementing fat to preweaned calves fed CMR increased BW gain and decreased starter intake through d 21 which had carryover effects on starter intake on d 49 and reduced hip height and tended to reduced withers height and body length by d 56. The addition of supplemental fat to LF, during mild cold stress, may result in a suboptimal ratio of crude protein to metabolizable energy in the CMR.

Extended negative dietary cation-anion difference feeding does not negatively affect postpartum performance of multiparous dairy cows.

Low postpartum blood calcium remains one of the largest constraints to postpartum feed intake, milk yield, and energy balance in transitioning dairy cows. Supplemental dietary anions decrease the dietary cation-anion difference (DCAD) and reduce the risk for postpartum hypocalcemia. Prepartum management strategies aiming to minimize social stress and diet changes have resulted in a need to explore the effects of extended exposure to a negative DCAD (>21 d) diet. Holstein and Holstein-cross dairy cows (n=60) were assigned to 1 of 3 treatments 42 d before expected calving to evaluate effects of supplying anions for 21 or 42 d during the dry period on energy status, postpartum production, and Ca homeostasis. Treatments included (1) a control diet (CON; DCAD=12 mEq/100 g of DM), (2) a 21-d negative DCAD diet (21-ND; DCAD=12 and -16 mEq/100 g of DM), and (3) a 42-d negative DCAD diet (42-ND; DCAD=-16 mEq/100 g of DM). Cows fed CON were fed positive DCAD prepartum for 42 d. Cows fed 21-ND received the positive DCAD (12 mEq/100 g of DM) diet for the first 21 d of the dry period and the anionic diet (-16 mEq/100 g of DM) from d 22 until calving. Cows fed 42-ND received the anionic diet for the entire dry period. Control and anionic diets were formulated by using 2 isonitrogenous protein mixes: (1) 97.5% soybean meal and (2) 52.8% BioChlor (Church & Dwight Co. Inc.), 45.8% soybean meal. Supplementing anions induced a mild metabolic acidosis, reducing urine pH for 21-ND and 42-ND compared with CON. Prepartum DMI was not different among treatments. Postpartum DMI was higher for 21-ND compared with CON (20.8 vs. 18.1±1.1 kg/d), and 42-ND had similar DMI compared with 21-ND. During the first 56 d of lactation 21-ND had greater average milk production compared with CON (44.8 vs. 39.2±2.1 kg/d). Average milk production by 42-ND was similar to 21-ND. Postpartum total blood Ca concentration was greater for 42-ND. Cows fed anionic diets prepartum tended to have lower lipid accumulation in the liver after calving compared with CON. These data suggest low-DCAD diets fed for 21 or 42 d during the dry period can have positive effects on postpartum DMI, Ca homeostasis, and milk production.

Effects of prepartum controlled-energy wheat straw and grass hay diets supplemented with starch or sugar on periparturient dairy cow performance and lipid metabolism.

This study examined the effects of a forage source [wheat straw (WS) versus grass hay (GH)] prepartum and supplemental carbohydrate source [corn (dry feed; DF) versus molasses (liquid feed; LF)] on pre- and postpartum intake, digestibility, selective particle consumption, milk yield, and lipid metabolism. The objectives were to determine if forage or pre- and postpartum supplement alters periparturient intake, energy balance, and milk yield. Sixty (n=15) multiparous dairy cows were used in a randomized complete block design with a 2 × 2 factorial arrangement of treatments to compare WS versus GH diets supplemented with either DF or LF. Dietary treatments were (1) WS prepartum + DF pre- and postpartum (WSDF), 2) WS prepartum + LF pre- and postpartum (WSLF), (3) GH prepartum + DF pre- and postpartum (GHDF), and (4) GH prepartum + LF pre- and postpartum (GHLF). Treatments began at dry-off, × before expected calving. During the prepartum phase, cows maintained dry matter intake (DMI) at 2.0% of body weight and prepartum energy balance remained positive for all treatments until calving. Prepartum GH diets had a more positive energy balance compared with WS diets. On week -5, energy balance was more positive for GHDF than for WSDF or GHLF. Energy balance for WSLF, however, was lower on week -3 and -1 than GHDF. Liquid feed decreased dry matter digestibility and increased prepartum liver triglyceride, serum nonesterified fatty acids (NEFA), and tended to increase ß-hydroxybutyrate. After calving, LF decreased DMI and energy balance, but not yield of milk or 3.5% fat-corrected milk, resulting in greater feed efficiency compared with DF. Forage did not affect postpartum DMI, but milk yield tended to be higher for WS versus GH. The DMI expressed as percentage of body weight was not affected by supplement or prepartum forage type. Cows fed WS had lower serum NEFA, higher liver glycogen, and tended to have a lower triglyceride to glycogen ratio postpartum than GH. Serum NEFA peaked on d 14 for all treatments and then declined thereafter. In postpartum diets, more particles were retained on the top screen for LF (>19.0mm) of the Penn State Particle Separator, which also tended to have more particles in the second screen (particles 19.0-8.0mm). Supplement had minimal effect on postpartum selective particle consumption. In conclusion, feeding diets containing WS resulted in lower postpartum serum NEFA, higher liver glycogen, and a tendency for greater milk production and lower liver triglyceride to glycogen than those containing GH. Liquid feed reduced postpartum DMI but not yield of milk yield or 3.5% fat-corrected milk yield, resulting in an improvement in feed efficiency. Future research should continue to investigate the use of single dry cow diet feeding strategies as they affect pre- and postpartum animal responses.

Metabolic effects of abomasal L-carnitine infusion and feed restriction in lactating Holstein cows.

L-Carnitine is required for mitochondrial fatty acid oxidation, but the effects of carnitine supplementation on nutrient metabolism during dry matter intake depression have not been determined in dairy cows. Studies in other species have revealed responses to L-carnitine that may be of specific benefit to dairy cows during the periparturient period. Eight lactating Holstein cows (132 +/- 36 d in milk) were used in a replicated 4 x 4 Latin square experiment with 14-d periods. Treatments were factorial combinations of abomasal infusion of either water or L-carnitine (20 g/d; d 5 to 14) and either ad libitum or restricted intake (50% of previous 5-d dry matter intake; d 10 to 14) of a balanced lactation diet. Liver and muscle biopsies were obtained on d 14 of each period. Feed restriction induced negative balances of energy and metabolizable protein. In feed-restricted cows, carnitine infusion increased 3.5% fat-corrected milk yield compared with those infused with water. Total carnitine concentration in liver was increased in feed-restricted cows infused with carnitine but not in feed-restricted cows infused with water. Carnitine infusion stimulated in vitro oxidation of [1-(14)C] palmitate to acid-soluble products and decreased the proportion of [1-(14)C] palmitate that was converted to esterified products by liver slices. Feed-restricted cows infused with carnitine had lower liver total lipid concentration and tended to have decreased triglyceride accumulation compared with feed-restricted cows infused with water. Plasma nonesterified fatty acid concentration was not altered by carnitine infusion but was increased by feed restriction; serum beta-hydroxybutyric acid was increased by carnitine infusion in feed-restricted cows. In cows fed for ad libitum intake, carnitine infusion affected beta-hydroxybutyric acid, insulin, and urea N in serum, liver glycogen concentration, and in vitro alanine oxidation by liver slices, suggesting that hepatic and peripheral nutrient metabolism was influenced. L-Carnitine infusion effectively decreased liver lipid accumulation during feed restriction as a result of greater capacity for hepatic fatty acid oxidation. Further research examining dietary supplementation of L-carnitine during the periparturient period is warranted.