Effects of day of gestation and feeding regimen in Holstein × Gyr cows: I. Apparent total-tract digestibility, nitrogen balance, and fat deposition.
This study investigated how feeding regimen (FR) alters apparent total-tract digestibility, performance, N balance, excretion of purine derivatives, and fat deposition in Holstein × Gyr cows at different days of gestation (DG). Forty-four pregnant multiparous Holstein × Gyr cows with an average initial body weight of 480±10.1 kg and an initial age of 5±0.5 yr old were allocated to 1 of 2 FR: ad libitum (AL; n=20) and maintenance level (ML; n=24). Maintenance level was considered to be 1.15% of body weight on a dry matter (DM) basis and met 100% of the energy requirements, whereas AL provided 190% of total net energy requirements. Data for hot and cold carcass dressing, fat deposition, average daily gain, empty body gain, and average daily gain without the gravid uterus were analyzed as a 4×2 factorial design. Intake, apparent total-tract digestibility, N balance, urinary concentration of urea, and purine derivatives data were analyzed as repeated measurements taken over the 28-d period (122, 150, 178, 206, 234, and 262 d of gestation). Cows were individually fed a corn silage-concentrate based diet composed of 93% roughage and 7% concentrate (DM basis) as a total mixed ration. Pregnant cows were slaughtered on 4 different DG: 139 (n=11), 199 (n=11), 241 (n=11), and 268 d (n=11). Overall, DM intake decreased as DG increased. This decrease observed in DM intake may be associated with the reduction in ruminal volume caused by the rapid increase in fetal size during late gestation. We observed an interaction for DM and organic matter apparent total-tract digestibility between FR and DG; at 150, 178, and 206 d of gestation, ML-fed cows had greater DM and organic matter apparent total-tract digestibility values than AL-fed cows. Rib fat thickness, mesentery, and kidney, pelvic, and heart fat were greater in AL-fed than in ML-fed cows at all DG, with the exception of rib fat thickness on d 139. Ad libitum-fed cows excreted more N in their feces and urine compared with ML-fed cows. Pregnant cows that were fed at maintenance had greater digestibility during some DG, excreted less N in feces and less N and urea in urine, and deposited less fat in the body. We therefore recommend ML (1.15% of body weight with 93% of roughage) as a FR for pregnant dry cows; however, during the last month of gestation, AL seems to be the most appropriate FR to avoid loss of body weight.
Department of Animal Science, Universidade Federal de Viçosa, Viçosa, Brazil 36571-000; Department of Animal Science, Colorado State University, Fort Collins 80523. Electronic address: polyana.rotta@ufv.br.
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PP
Rotta
Department of Animal Science, Universidade Federal de Viçosa, Viçosa, Brazil 36571-000.
S C Valadares
SC
Filho
Department of Animal Science, Universidade Federal de Viçosa, Viçosa, Brazil 36571-000.
T R S
TR
Gionbelli
Department of Animal Science, Universidade Federal de Viçosa, Viçosa, Brazil 36571-000; Department of Animal Science, Colorado State University, Fort Collins 80523.
L F
LF
Costa E Silva
Department of Animal Science, Colorado State University, Fort Collins 80523.
T E
TE
Engle
Department of Animal Science, Universidade Federal de Viçosa, Viçosa, Brazil 36571-000.
M I
MI
Marcondes
Embrapa Gado de Leite, Juiz de Fora, Brazil 36038-330.
F S
FS
Machado
Department of Animal Science, Universidade Federal de Viçosa, Viçosa, Brazil 36571-000.
F A C
FA
Villadiego
Department of Animal Science, Universidade Federal de Viçosa, Viçosa, Brazil 36571-000.
L H R
LH
Silva
D000824:Animal Nutritional Physiological Phenomena / Q000187:drug effects; D000818:Animals; D001823:Body Composition; D001835:Body Weight; D002417:Cattle / Q000502:physiology*; D004032:Diet / Q000662:veterinary*; D004043:Dietary Fiber; D004063:Digestion; D002149:Energy Intake; D005243:Feces; D005260:Female; D041981:Gastrointestinal Tract; D005865:Gestational Age; D007774:Lactation / Q000187:drug effects; D008892:Milk; D009584:Nitrogen / Q000378:metabolism*; D009751:Nutritional Requirements; D011247:Pregnancy; D012417:Rumen / Q000187:drug effects; D012820:Silage; D003313:Zea mays
D004043:Dietary Fiber; D009584:Nitrogen
N balance; ad libitum; maintenance; performance